Guidelines for conducting acceptance tests. Guidelines for testing power transformers
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RD 34.45.309-92
|
ORGRZS MOSCOW 1993 |
ISHSTECSH OF FUEL AND ENERGY OF THE RUSSIAN FEDERATION
METHODOLOGICAL INSTRUCTIONS FOR CONDUCTING HEATING TESTS OF GENERATORS
RD 34.45.309-92
ORGRES SERVICE OF EXCELLENCE
As testing practice shows, it is easiest to measure the resistance of the rotor winding by supplying power from battery or a special direct current source, providing a stable current of about 10 A, with the same instruments that will be used for measurements in load modes.
Power is supplied to the rotor winding using special clamps or bands made of aluminum or copper busbars, placed on the rotor rings. The voltmeter must be connected at separate ends directly to the rings. The connection is usually made using probes and only for the duration of instrument readings.
Measurements should be carried out after turning on the current and at the end of the transient process* caused by the rotor inductance. Instrument readings are carried out simultaneously upon command.
If the rotor winding is powered from a backup exciter (or other powerful source direct current) with a current of the order of O.3-0.5 rated, in order to avoid errors from heating the winding during the experiment, the duration of the latter should be limited. For rotors of turbo and hydrogen generators with indirect cooling, in which the rated current density is about 3.5-4 A/W%, the permissible counting time during which the winding heats up by no more than 1% is 1-2 minutes at a current of 0.3-0.51 NSh
For the windings of turbogenerators with direct gas or liquid cooling, in which the nominal current density is 7-10 A/mm^, the permissible counting time is reduced to 10-20 e. Thus, for these machines, the specified method turns out to be practically inapplicable without extrapolation of the obtained temperature at the moment of current supply ^
Measurements should be made at several (about three) current values, making at least three readings for each of them.
Since the same millivoltmeters are usually used as direct current devices (one with a shunt, the other with an additional resistor), it is recommended to repeat the experiments by swapping the indicated devices to increase the accuracy of g x measurement.
The values of r x are calculated as the average of the results of those readings that do not differ from the average value by more than 0.556. The number of such readings must be no less than one.
Determining r x should be especially careful, since an error in this measurement affects all subsequent measurements of the rotor temperature rise (a 1% error in measurement gives an error of approximately 2.5 ° C when determining the temperature).
The resulting rotor winding resistance should be brought to a temperature of 15% in order to be able to compare with the manufacturer's data.
3.3. Before testing, it is necessary to measure the resistance of all installed resistance thermal converters at DC in a cold state and insulation resistance in accordance with GOST 11828-86 and (ij.
It is necessary in advance to technical documentation set the resistance values of the connecting wires inside the generator from the resistance thermal converter to the output terminals.
You should also check the compliance of the markings and installation locations of resistance thermal converters with the factory drawings.
It is advisable to measure the resistance of resistance thermal converters on a closed machine, and if it is open, it is recommended to cover the ends with a tarpaulin, since due to drafts in the machine room the temperature of individual parts of the stator may be different. Measurements should be made no earlier than 6-7 days after stopping the generator, provided that during this time the temperature in the machine room did not change significantly. If necessary, this period can be reduced by rotating the generator at the rated frequency at Idling without excitation after disconnection from the network. The criterion for achieving a steady-state temperature is its stabilization over time and the coincidence of measurement results for resistance thermal converters that have the same resistance of connecting wires.
The temperature inside the generator should be measured with expansion thermometers installed in the switchboards and generator housing. If possible, additional thermometers should be placed in the generator housing. 6, the average of all measured temperature values is taken as the calculated temperature.
The resistance of resistance thermal converters should be measured with a single bridge of an accuracy class of at least 0.5 or other - - 12 -
with instruments* that provide the specified accuracy. You can connect the measuring device to the terminals of resistance thermal converters either using probes* or using a switch installed for measurements during heating tests (see paragraph 3.5). It is also necessary to measure the resistance of the connecting wires from the terminals to the measuring bridge (including the resistance of the switch). The obtained resistance values of the resistance thermal converters (minus the resistance of the connecting wires inside and outside the generator) lead to a temperature of O^C. The resulting resistances should not differ from the nominal resistance of resistance thermal converters at 0°C by more than 1%.
3.4. The excess of the temperature of the rotor winding over the temperature of the cooling medium should be determined by the change in winding resistance at direct current when it is heated.
To do this, during the experiment, the resistance of the winding in a heated state (g x) must be measured using the voltmeter and ammeter method.
The voltage should be measured directly at the rotor wheels to eliminate the influence of the voltage drop across the working brushes.
Copper mesh or plate brushes should be used as measuring brushes; it is not recommended to use carbon brushes, since the contact resistance between the brush and the ring quickly increases due to the formation of a film on the surface of the brush. A film can also form on copper-graphite brushes with a low copper content, so when using such brushes they should be cleaned periodically.
Measuring brushes must be equipped with insulated handles with which the brushes apply the rings during measurement. It is most convenient to install measuring brushes in brush holders from which the working brushes have been previously removed. Measuring brushes must be well insulated from the brush holders.
To check this, you should compare the voltage values measured directly on the rings and on the traverses of the brush apparatus. The voltage on the traverses is greater than the voltage on the rings by the value of the voltage drop in the working brushes and the transition resistance between the rings and brushes. This value is usually 2-5 V.
It is most advisable to carry out this check at the beginning or end of a series of readings.
The wires from the measuring brushes to the device must have reliable insulation, since the voltage on the rings of modern large generators reaches 500 V or more. You can, for example, use LPRGS wires enclosed in a vinyl chloride tube.
Counts by control devices measuring current and voltage must be carried out simultaneously by two observers. For each measurement, at least three readings should be taken. The rotor winding resistance is calculated as the average of the readings of this measurement.
The temperature rise of the rotor winding is determined by the formula
A l ) = JLt£<.(r r - г х) +т} х - г1 0 ,
where is 1? x - temperature at which the resistance was measured
rotor speed () in a cold state, °C;
Temperature of incoming cooling gas,
D - number equal to 235 for copper winding (without additive and with silver additive); g x 1 g g - rotor winding resistance measured in cold and heated states. Om-
The temperature rise should be determined immediately after each measurement* If the results of individual readings differ from each other by more than $0.5, the measurement should be repeated.
In modern large hydrogen generators, excitation is carried out by rectified alternating current, the voltage of which has a fairly significant alternating component. Although the magneto-electric device, which usually measures the voltage on the rotor rings, does not respond to this component, it can be overloaded. Therefore, before testing, the effective voltage value should be measured and compared with the average. If the ratio - E FU exceeds 1.5, it is recommended to turn on the device measuring voltage through an * L-shaped LC filter with low active resistance - - 14 -
laziness. The values of L and C are selected so that the ratio -jj*- does not exceed 1.5. The filter should be turned on through fuses and in such a way that the container is located on the side of the device.
For a device that measures excitation current, installation of a filter is not required.
3.5. For generators with indirect cooling, the excess of the temperature of the winding and stator steel above the temperature of the cooling gas entering the machine should be determined by the readings of resistance thermal converters installed in the grooves. Resistance thermal converters that measure the temperature of the winding are placed between the rods, and those that measure the temperature of the steel are placed at the bottom of the groove.
For generators with direct gas and oil cooling, a similar system for installing resistance thermal converters is adopted, however, the temperature measured by resistance thermal converters placed between the rods can be taken as the winding temperature only conditionally, since the heat generated in the winding is removed mainly by the cooling medium, passing inside the rod, and the highest temperature occurs in the area where it exits the rods, and not in the groove part where resistance thermal converters are installed. In oil-cooled turbogenerators, resistance thermal converters that control the temperature of the stator steel can be embedded in the back of the stator core.
In generators with direct water cooling of the stator winding, resistance thermal converters are placed between the rods or under wedges in each groove, or in the grooves of the drain rods of each hydraulic branch, or are pressed by spacers to the side surfaces of the lower drain rods when exiting the groove, and in machines with full water cooling - in the drain hoses of each of the rods outside the winding. The main purpose of these resistance thermal converters is to control the uniform distribution of the distillate over the individual winding rods and the absence of their clogging.
For generators with direct water cooling, resistance thermal converters that measure the temperature of the steel are installed on the surface.
The resistance of resistance thermal converters should be measured with a single bridge of an accuracy class of at least 0.5.
During testing, readings from panel ratiometers or automatic recording devices should also be recorded.
The bridge must measure the resistance of all resistance thermal converters installed in the generator, regardless of whether they are connected to the operational thermal control system or not.
When measuring with a bridge, the operating system switch must be set to a position in which all measured resistance thermal converters are turned off. In the presence of recorders, this requirement is difficult to fulfill. In this case, it should be borne in mind that resistance measurement with a bridge can only be carried out at a time when the resistance thermal converter is not connected to the thermal control system.
High-power water-cooled generators have a large number of resistance thermal converters embedded in the stator. Since their resistance is measured by the bridge every half hour during the last hours of the experiments, it is inconvenient to use probes for this.* It is recommended to use multi-channel 1 switches for this purpose, which are connected to the assembly of resistance thermal converters for the entire test period. Before testing, the contact system of these switches must be carefully checked and the resistance of the connecting ends (including the switch contacts) re-measured.
The switches must be connected in such a way as not to distort the readings of the operational heat control system.
If you have well-established self-speaking electronic bridges or an automated control system with an accuracy class of at least 0.5, it is necessary to monitor the thermal state of the generator during testing using these devices. In this case, before testing, the accuracy of the readings of these instruments must be checked.
The temperature rise according to the installed resistance thermal converter is determined by the same formula as the temperature rise of the rotor winding.
Since resistance thermal converters used in generators have a standard nominal resistance at 0°C, this formula can be simplified. For resistance thermal converters manufactured in accordance with GOST 6651-84, the nominal resistance at (Rac is 50 cm, and for thermal converters manufactured earlier - 53 Ohm.
The formulas for calculation will accordingly look like:
6t)-M(g g -50)-F o, &\) w 4№(g g -53)-1) 0 .
The values of r g obtained during the experiments are substituted into these formulas, minus the resistance of the connecting wires. The latter represents the sum of the resistances of the connecting wires inside and outside the generator.
The simplified formula greatly facilitates the processing of the obtained data without significantly affecting the accuracy of the results obtained.
3.6. The temperature of the gas entering and exiting the generator is measured using all thermometers and thermal converters installed on the generator. In advance, with the generator stopped, you should inspect the installation locations of thermometers and thermal converters and make sure that they are located in the gas flow, the temperature of which is controlled. You can (in addition to clause 3.3) check the correctness of the readings of resistance thermal converters by installing control expansion thermometers in the immediate vicinity of them and then checking them. indications.
The resistance of resistance thermal converters is measured in the same way as indicated in paragraph 3.3.
The calculated temperature of the hungry eider is taken as the fraction;
a) for generators with coolers installed outside the generator (in cold gas chambers) - the gas temperature at the inlet to the generator;
b) for generators with coolers built into the housing, the temperature of the gas at the outlet of the coolers.
In all cases, the average value must be determined from the readings of all expansion thermometers and thermal converters measuring the temperature of the cold gas, unless these readings diverge by no more than 2-44].
The temperature of the heated gas leaving the generator is taken as the average of the readings of all expansion thermometers and thermal converters installed in the hot gas chambers or at the inlet to the coolers.
Of particular importance is the measurement of the temperature of the heated gas at the outlet of the stator winding for generators with direct gas cooling.
The temperature of the gas leaving the caps of the stator winding largely characterizes the heating of the winding. This also applies to the temperature of the gas leaving the stator core with an axial cooling system. Both of these temperature values are standardized and special attention is paid to them when operating the generator. Therefore, it is necessary to carefully check the serviceability and correct installation of resistance thermal converters that measure the temperature of the gas leaving the winding and core.
For generators with direct cooling in the presence of a compressor, the temperature before and after it and the temperature of the gas supplied to cool the rotor winding (in the bypass sections) are also determined.
3.7. To measure the temperature of the coolant entering and leaving the stator and rotor windings, control expansion thermometers with 0.1°C division foam must be installed in addition to stationary resistance thermal converters. The pockets in which thermometers are installed must provide the possibility of filling them with oil and immersing the working part of the thermometer
not less than 2/3 of the pipeline diameter.
3.8. The temperature of the water entering and leaving gas coolers and heat exchangers is measured by expansion thermometers installed in pockets welded into oil-filled pipes. Pockets should be installed in the same way as indicated in ft.3.7. Tempe-
The temperature of the water entering the cooler can be measured on the common water pipeline immediately before its branching to the coolers. The temperature of the water leaving the coolers should be measured in the immediate vicinity of each cooler; it should be measured with thermometers with 0.1°C divisions.
3.9. The flow of water through gas coolers and distillate through the windings, core and other structural parts should be measured using restriction devices (diaphragms) by differential pressure.
Orifice plates must be installed on the cooling water pressure lines of each chiller. If there are no separate cooler sections on the pipelines that are long enough to install diaphragms, you can measure the flow rate on a common pressure pipeline.
The pressure drop across the diaphragm is measured by U-shaped differential pressure gauges. To fill them, you can use light liquids that do not mix with water (for example, tetrabromoethane, bromoform, carbon tetrachloride, etc.), depending on the observed pressure drop.
The calculation method for newly manufactured diaphragms, requirements for the design and installation of diaphragms, connecting lines and differential pressure gauges are contained in.
The distillate flow through the windings, core and other structural elements is determined using station flow meters. If necessary, additional measuring diaphragms can be installed*
EVIL. Determination of gas flow through the generator is carried out using one of the generally accepted methods described in [Z] - .
For sealed generators with built-in gas coolers, gas flow can be determined from the heat balance equation of gas coolers:
Water and gas consumption, m e /s;
Volumetric heat capacities of water and gas, J/m 3 * °C;
Ai)q and AL? r - temperature differences of water and gas* passing through the gas cooler, °C.
To determine gas flow, the water flow through each gas cooler and the temperature of the water and gas at the inlet and outlet of the gas cooler must be measured. The heat capacity of water is taken equal to unity, the heat capacity of gas is determined by the formula:
where P is the absolute gas pressure in the generator housing, MPa, kg/cm^ or mmHg;
P atm - atmospheric pressure, MPa, kg/cm^ or mm Hg. (normal);
Gas temperature at the gas cooler inlet, °C.
The gas flow through the generator is the sum of the gas flow through the individual gas coolers.
3. II On hydrogen-cooled generators, the heating test must also measure:
a) excess hydrogen pressure in the generator housing (at an excess hydrogen pressure of 0.005-0.01 MPa (0.05-0.1 kg/cm^), it is recommended to use a water pressure gauge; at 0.05-0.1 MPa (0.5 -1 kg/cm^) and higher pressures - spring (preferably laboratory);
b) the purity of hydrogen using a panel gas analyzer (the readings of the gas analyzer should be checked based on the results of a chemical analysis of the gas).
3.12. Determination of control characteristics, rated and maximum excitation currents should be made in accordance with the requirements of GOST 10169-77.
3.I2.I. The control characteristics, which are the dependences of the excitation current on the armature current, should be determined at constant voltage, power factor and rotation speed using the direct load method. It is allowed to determine the adjustment characteristics using the graphical construction method.
DEVELOPED by the All-Union Scientific Research Institute of Electric Power Industry (VNIIE)
PERFORMERS L.G.VOLODARSKY, E.V.1USCH®, O.I.IB1DOV,
G. A. OSTROUMOVA, A. P. CHISTIKOV
U TVER8DEN0 Department of Scientific and Technical Development 01/29/92
Deputy Head K.M.ANTIPOV
(C) SPO SR1G8S, 1993
3.12.2. The rated excitation current should be determined from the control characteristic taken at the rated power, voltage, power factor and frequency of the network. If, when taking this characteristic, the network voltage deviated from the rated voltage by no more than +5$, it is possible to plot the dependence of the excitation current on the apparent power and determine the value of the rated excitation current for the rated apparent power. The rated excitation current can also be determined graphically using a diagram. To determine the calculated inductive reactance Xp in accordance with the requirements of GOST 10169-77, use the characteristics of no-load and short circuit and the load characteristic point taken at COS ^ * 0 and excitation current
niya, close to nominal. It is allowed to determine xp by the method of successive approximation. To do this, having set Xp * 0.85 X "d, a diagram is constructed for one of the experimental points of the control characteristic, from which the calculated rotor current is determined and compared with the experimental value of the rotor current. If there is no discrepancy, then the value of X p is corrected and the diagram is drawn again for the same experimental point of the control characteristic. The construction is repeated until a good agreement between the calculated and experimental values of the rotor current is obtained. The final value of X p is taken as the calculated value and can be used to determine the rated and maximum rotor currents obtained under the following conditions:
I -0.95l f
I - 1,051 nom
METHODOLOGICAL SPECIFICATIONS
SIMPLE"" IYASHTASHL RD 34.45.309-92
GSHERATSROZ FOR HEATING
These Guidelines establish the scope and procedure for conducting heating tests on generators in operation at power plants.
The guidelines are intended for workers of power plants and organizations involved in testing generators for heating.
With the release of these Methodological Instructions, the previously published “Methodological Instructions for Conducting Heating Tests on Generators” (Moscow: SPO Soyuetekhvnergo, 1964) are cancelled.
GENERAL PART
Tests of generators for heating the valley are carried out no later than 6 years after commissioning. Subsequently, during operation, control tests for heating are carried out periodically (once every 10 years) at one or two renins of operation. Donning tests are carried out after complete winding of the rotor or stator, or reconstruction of the cooling system. Generators with a capacity of up to 12 MW do not need to be tested.
The first seven sections provide recommendations for conducting heating performance tests to determine the heating characteristics of the generator, determine their compliance with the requirements of standards and specifications of delivery, and determine the loads permissible in operation. In some cases, tests may fail in order to determine the causes of problems in the generator cooling system.
Based on the results of these tests, the highest permissible operating temperatures (rounded up to 5%) of the stator windings, rotor, active steel and cooling media at the outlet of the windings or stator core are established during continuous operation of the generator at rated load at rated power factor values , voltage and parameters of cooling media.
For turbogenerators, on which, in accordance with GOST 533-85 and technical conditions, long-term operation with an increased compared to the rated active load is allowed at established values of the power factor and cooling parameters, the highest permissible operating temperatures should be determined when operating at the rated and maximum continuous load* For the highest permissible operating temperatures for such machines, the maximum temperatures determined for these modes should be taken - If the highest temperatures obtained from the results of heating tests when generators operate at rated or long-term maximum load are higher than the maximum permissible values given in GOST 533 -85, GOST 5616-81, technical conditions or specified by the manufacturer in the technical description and operating instructions, then the power of the generator under test must be accordingly limited to a value at which heating will not exceed the maximum permissible until the causes are identified and eliminated, which caused increased heating. The power plant must report the power limitation to the Technical Department of Rosenergo Corporation and the manufacturer*
If the highest temperatures obtained from the results of heating tests are below the maximum permissible values, then one hundred cannot serve as a basis for re-labeling the generator to a higher power. If it is necessary to re-mark the generator, when an increase in power is desirable to deliver the “locked” power of the turbine and is not limited by the power of the transformer, additional special tests must be carried out according to a program drawn up for each case. Before testing the valley, appropriate calculations should be carried out and the generator equipped with additional means of measuring temperature and other quantities. It should be borne in mind* that I will give after the corresponding
During tests, remarking can only be done with the permission of the manufacturer and the Technical Department.
I. CONDITIONS FOR CONDUCTING PERFORMANCE TESTS FOR HEATING
1.1. Tests must be carried out on a generator in good condition, with all its main parts and auxiliary devices operating normally. Particular attention should be paid to the condition of the cooling system. It is also necessary to check the rotor winding for the absence of short-circuited turns. The check is carried out both in a stationary state and when the rotor rotates at different speeds, up to the nominal
(according to GSST 10169-77).
For rotors with turn faults, it is impossible to measure the temperature using the resistance method, since the value of the measured resistance differs from the actual one, therefore heating tests of such machines must be carried out after the turn shorts have been eliminated.
1.2. The instruments used to make measurements must be verified and have the stamps of the State Verification Authorities.
The use of devices that have not passed metrological verification is prohibited.
1.3. On hydrogen-cooled turbogenerators that are approved for air-cooled operation, tests are carried out with both hydrogen and air cooling. On hydrogen-cooled turbogenerators, which, according to their tabular data, can operate at different hydrogen pressures, tests must be carried out for the specified hydrogen pressure values.
Tests at hydrogen pressure exceeding the nominal pressure, in cases where the maximum pressure is not indicated in the generator passport, are carried out in agreement with the manufacturer. Tests at elevated pressure should be preceded by pressure testing of the generator together with the gas-oil system with an excess air pressure of 0.05 MPa (0.5 kgf/cm^), exceeding the pressure at which the tests will be performed.
2. SCOPE OF HEATING PERFORMANCE TESTS
The scope of testing includes:
2.1. Determination of the resistance of the rotor winding and embedded resistance thermal converters in a cold state.
2.2. Carrying out four heating experiments with loads of about 0.6; 0.75; 0.9 and 1.0 Rn (active power) at rated or close to rated power factor. In this case, the machine voltage should not differ from the nominal voltage by more than 5%. It is allowed to carry out heating tests at a voltage higher than the rated voltage by more than W (according to the operating conditions of the power plant). However, the total power of the generator should not exceed that set by the manufacturer.
In accordance with GOST 11828-86 "Rotating electrical machines. General test methods" it is possible to carry out tests at three to four different loads within 0.6 rated power up to the maximum possible under the operating conditions of the power plant (but not lower than 0.9 rated current), at which the intervals between the squares of the currents of the working circuit of the windings would be approximately the same in order to, if necessary, provide a more accurate extrapolation of the obtained dependencies.
During the experiments the following should be measured:
a) electrical quantities that characterize the operation of generators
b) temperature of the winding and stator steel according to the installed thermal resistance converters;
c) temperature of the rotor winding using the resistance method;
d) the temperature of the incoming and outgoing cooling rasa, and for liquid-cooled generators also the temperature of the incoming and outgoing liquid;
e) temperature of cooling water at the inlet and outlet of gas coolers and heat exchangers;
f) water flow through gas coolers, and for liquid-cooled generators, liquid flow through the windings and core and liquid pressure at the inlet and outlet of the windings;
g) gas flow through the generator;
h) pressure and purity of hydrogen.
Determination of water flow through coolers is desirable in all cases and mandatory when testing new types of generators and new types of coolers, as well as when the inlet gas temperature is elevated above normal and other problems in the cooling system.
Determination of gas flow is mandatory in cases where there is increased heating of generator parts and cooling gas, temperature unevenness or other problems in the cooling system.
2.3. Determination of the regulation characteristic, nominal and maximum excitation currents under nominal conditions and when the stator voltage and current deviate by +5$ of nominal values.
3. MEASUREMENTS AND REQUIREMENTS
TO MEASURING INSTRUMENTS
3.1. During heating tests and when determining the control characteristic, the following electrical quantities are measured:
a) active and reactive power;
b) current in the stator winding (in three phases);
c) stator winding voltage (in three phases);
d) excitation current;
e) voltage on the rotor rings;
e) frequency.
All specified values are determined both by station switchboard devices and by control devices installed at the time of testing. It is allowed to determine the frequency of the current using panel devices.
Measuring instruments in accordance with the requirements of GOST 11828-86 should be selected so that the measured values are within the $30-95 scale. The accuracy class of control devices must be no lower than 0.5, and for devices installed in the excitation circuit, no lower than 0.2. Stator monitoring devices are connected to station instrument transformers. Installation of special instrument transformers is not required. It is only necessary to check whether the current transformers are overloaded as a result of switching on additional devices, and, if necessary, take measures to unload them during the tests.
The control shunt installed in the rotor winding circuit must have an accuracy class of at least 0.2. In the absence of shunts of this class, shunts of class 0.5 can be used without reducing the requirements for the devices that are connected to them. It is allowed to use operational shunts of a class of at least 0.5. The power factor is determined by calculation based on the readings of control instruments installed to measure current, active power and stator voltage. It is possible to determine the power factor by the ratio of the readings of two wattmeters installed to measure active power in accordance with. In this case, it is necessary to ensure that the measured values of currents and voltages are not lower than 30$ of the nominal tqkob and voltages of the wattmeters used.
When taking measurements on more than one instrument, it is recommended to take readings from all instruments for each measurement simultaneously. This is mandatory when measuring resistance using the ammeter and voltmeter method and three-phase current power using the method
TWO WattmöhrSZ.
3.2. Before heating tests, the resistance of the rotor winding at direct current in a practically cold state (G x) and the temperature at which this was carried out must be measured.
measurement (l? x) according to GOST 11828-86. The value of this resistance is the starting point for determining the temperature rise of the rotor winding during heating tests. According to GOST 183-74, the practically cold state of the machine is taken to be one in which the temperature of any part of the machine differs from the ambient temperature by no more than +3°C. The winding temperature in a cold state on a removed rotor or on an open machine is measured by several (at least four to five) expansion thermometers installed on turbogenerators under the bandages and along the rotor barrel, and on hydrogenerators - at different poles along the winding.
The ambient air temperature is determined according to GSST 11828-86 as the arithmetic mean of the readings of several thermometers located at different points around the generator, at a height equal to half the height of the generator, and at a distance of 2 m from the generator.
If, due to operating conditions, the generator cannot be opened, it is permissible to measure g x on a closed generator. In this case, it is necessary to periodically monitor the cooling of the generator using all installed temperature indicators (resistance thermal converters or thermocouples and expansion thermometers) and begin measuring g only after reaching a practically cold state -
Simultaneously with the measurement of g x, the temperature is measured using all installed temperature meters. The average of all obtained temperature values is taken as the winding temperature.
Expansion thermometers must have a division value of no more than 1%.
For water-cooled rotors, the winding temperature is taken to be the average of the temperatures of the water entering and exiting the winding, provided that these values differ from each other by no more than 1^, and the temperature of the incoming water does not change by more than C.5 °b for 30 minutes preceding the resistance measurement.
g x should be measured using the voltmeter and ammeter method. Measuring instruments must have an accuracy class of at least 0.2. When measured using an ammeter-voltmeter method, the shunt must have an accuracy class of at least 0.2.
These Rules are mandatory for Consumers operating electrical installations with voltages up to 220 kV. When testing and measuring the parameters of electrical equipment of electrical installations with voltages above 220 kV, as well as generators and synchronous compensators, one should be guided by the relevant requirements.
3.6.2. Specific terms for testing and measuring the parameters of electrical equipment of electrical installations during major repairs (hereinafter - K), during routine repairs (hereinafter - T) and during overhaul tests and measurements, i.e. during preventive tests performed to assess the condition of electrical equipment and not related to the removal of electrical equipment for repair (hereinafter referred to as M), the Technical Manager of the Consumer is determined based on Appendix 3 of these Rules, taking into account the recommendations of factory instructions, the state of electrical installations and local conditions.
3.6.3. For types of electrical equipment not included in these standards, specific standards and terms for testing and measuring parameters must be established by the technical manager of the Consumer, taking into account the instructions (recommendations) of the manufacturers.
3.6.4. Test standards for electrical equipment of foreign companies must be established taking into account the instructions of the manufacturer.
3.6.5. Electrical equipment after repair is tested to the extent determined by the standards. Before repairs begin, tests and measurements are carried out to establish the scope and nature of the repairs, as well as to obtain initial data with which the results of post-repair tests and measurements are compared.
3.6.6. Assessment of the insulation condition of electrical equipment that is in the stage of long-term storage (including emergency reserve) is carried out in accordance with the instructions of these standards, as well as those in operation. Individual parts and components are checked according to the standards specified by the manufacturer in the accompanying documentation for the products.
3.6.7. The scope and frequency of tests and measurements of electrical equipment of electrical installations during the warranty period must be taken in accordance with the instructions of the manufacturers.
3.6.8. A conclusion on the suitability of electrical equipment for operation is issued not only based on a comparison of test and measurement results with the standards, but also on the basis of the totality of the results of all tests, measurements and inspections performed.
The values of the parameters obtained during tests and measurements must be compared with the results of measurements of the same type of electrical equipment or electrical equipment of other phases, as well as with the results of previous measurements and tests, including their original values.
The initial values of the measured parameters should be understood as their values indicated in the passports and reports of factory tests and measurements. In the case of a major or restorative repair, the initial values mean the measurement results obtained during these repairs.
In the absence of such values, the values obtained during testing of newly introduced equipment of the same type can be taken as initial values.
3.6.9. Electrical equipment and insulators with a rated voltage exceeding the rated voltage of the electrical installation in which they are operated can be tested with increased voltage according to the standards established for the insulation class of this installation.
3.6.10. If testing with increased rectified voltage or power frequency voltage is carried out without disconnecting the busbar from the electrical equipment, then the value of the test voltage is taken according to the standards for electrical equipment with the lowest test voltage.
High voltage testing of insulators and current transformers connected to power cables of 6 - 10 kV can be carried out together with the cables according to the standards adopted for power cables.
3.6.11. In the absence of the necessary AC test equipment, it is allowed to test electrical equipment of switchgears (voltage up to 20 kV) with an increased rectified voltage equal to one and a half times the value of the power frequency test voltage.
3.6.12. Tests and measurements must be carried out according to programs (methods) approved by the Consumer’s manager and corresponding to the requirements of duly approved (recommended) documents, standard guidelines for tests and measurements. Programs must include measures to ensure the safe conduct of work.
3.6.13. The results of tests, measurements and testing must be documented in protocols or acts that are stored together with passports for electrical equipment.
3.6.14. Electrical tests of electrical equipment and sampling of transformer oil from tanks of devices for chemical analysis must be carried out at an insulation temperature of at least 5 °C.
3.6.15. It is recommended to measure the insulation characteristics of electrical equipment using the same type of circuits and at the same temperature.
Comparison of insulation characteristics should be made at the same insulation temperature or similar values (temperature difference no more than 5 °C). If this is not possible, then temperature recalculation must be carried out in accordance with the operating instructions for specific types of electrical equipment.
3.6.16. Before testing and measuring electrical equipment (except for rotating machines in operation), the outer surface of its insulation must be cleaned of dust and dirt, except in cases where measurements are carried out using a method that does not require turning off the equipment.
3.6.17. When testing the insulation of the windings of rotating machines, transformers and reactors with increased power frequency voltage, each electrically independent circuit or parallel branch must be tested in turn (in the latter case, if there is complete insulation between the branches). In this case, one pole of the testing device is connected to the output of the winding under test, the other - to the grounded body of the electrical equipment being tested, to which all other windings are electrically connected for the entire duration of testing a given winding. Windings that are tightly connected to each other and do not have an outlet for the ends of each phase or branch must be tested against the housing without disconnection.
3.6.18. When testing electrical equipment with increased power frequency voltage, as well as when measuring current and no-load losses of power and instrument transformers, it is recommended to use the linear voltage of the supply network.
The rate of voltage rise to 1/3 of the test value can be arbitrary. Next, the test voltage must rise smoothly, at a speed that allows visual reading by measuring instruments, and upon reaching the set value, it must be maintained unchanged during the test time. After the required exposure, the voltage gradually decreases to a value of at least 1/3 of the test value and turns off. The test duration means the time of application of the full test voltage established by the standards.
3.6.19. Before and after testing the insulation with increased power frequency voltage or rectified voltage, it is recommended to measure the insulation resistance using a megohmmeter. The one-minute value of the measured resistance R60 is taken as the insulation resistance.
If, in accordance with the standards, the determination of the absorption coefficient (R60 / R15) is required, the count is made twice: 15 and 60 s after the start of measurements.
3.6.20. When measuring the insulation parameters of electrical equipment, random and systematic errors must be taken into account due to the errors of measuring instruments and apparatus, additional capacitances and inductive couplings between the elements of the measuring circuit, the effects of temperature, the influence of external electromagnetic and electrostatic fields on the measuring device, method errors, etc. When measuring leakage current (conduction current), if necessary, rectified voltage ripples are taken into account.
3.6.21. The values of the tangent of the dielectric loss angle of the insulation of electrical equipment and the conduction current of the arresters in these standards are given at an equipment temperature of 20 °C.
When measuring the dielectric loss tangent of electrical equipment insulation, its capacitance should also be determined at the same time.
3.6.22. Testing with a voltage of 1000 V of industrial frequency can be replaced by measuring the one-minute value of insulation resistance with a megohmmeter for a voltage of 2500 V. This replacement is not allowed when testing critical rotating machines and relay protection and automation circuits, as well as in cases specified in the standards.
3.6.23. When testing the external insulation of electrical equipment with increased power frequency voltage produced under environmental factors different from normal (air temperature 20 °C, absolute humidity 11 g/m3, atmospheric pressure 101.3 kPa, unless other limits are adopted in the standards for electrical equipment) , the value of the test voltage must be determined taking into account the correction factor for the test conditions, regulated by the relevant state standards.
3.6.24. Carrying out several types of insulation tests of electrical equipment, high voltage testing should be preceded by a thorough inspection and assessment of the insulation condition by other methods. Electrical equipment rejected during external inspection, regardless of the test and measurement results, must be replaced or repaired.
3.6.25. The results of the high voltage test are considered satisfactory if, when applying the full test voltage, no sliding discharges, leakage current surges or smooth increases in leakage current, breakdowns or flashovers of insulation were observed, and if the insulation resistance measured by a megohmmeter remained the same after the test.
G U "P E T E R B U R G G O S E N E R G O N A D Z O R"MILITARY ENGINEERING AND TECHNICAL UNIVERSITY
METHODOLOGICAL INSTRUCTIONS
ON CONDUCT OF ACCEPTANCE AND DELIVERY
TESTS
SPECIAL ELECTRICAL INSTALLATIONS
USING HEATING
CABLES
to VTT SEUNK
_______________________
2001
2001
CONTENT
General provisions
Preparation for acceptance testing of SEUNK
Inspection of SEUNK
SEUNK tests
Requirements for the SEUNK acceptance test protocol
Safety precautions during testing
Measuring the resistance of the phase-zero loop
Checking the characteristics of the protective device (settings of circuit breakers, fuse currents, RCD testing) Appendix D (recommended) Methodology for testing the ohmic resistance of a heating cable
GENERAL PROVISIONS
1.1 Before putting into operation, each installed SEUNK must undergo acceptance tests in accordance with the requirements of GOST R 50571.16-99, PUE (Chapter 1.8) and BTT.
The proposed acceptance testing methodology makes it possible to implement a systematic approach to performing tests both in terms of volume and sequence of their implementation.
1.2 Before carrying out acceptance tests, preparations are carried out for their implementation.
Acceptance tests of SEUNK include:
inspection of the installed SEUNK;
direct testing.
When conducting acceptance tests of SEUNK. installed during the reconstruction of the facility (room, roof, pipeline, tank, etc.). it is necessary to make sure that the use of SEUNK meets the requirements of the set of standards GOST R 50571, Temporary technical requirements and does not reduce the electrical and fire safety of existing electrical installations and electrical equipment.
PREPARATION FOR ACCEPTANCE
2.1 Before the start of work on the acceptance testing of the control system, the following activities must be completed:
the design documentation for a special electrical installation using a heating cable, its connection with production technology and technical documentation of the SEUNK manufacturers were studied;
the work schedule has been agreed upon;
the necessary instructions and technical literature have been selected, protocol forms or workbooks have been selected in the required quantity;
a fleet of necessary instruments and devices has been prepared.
agree with the Customer on the allocation of production premises for storing instruments and equipment, for working with design and reporting documentation (the premises must be located in close proximity to the tested control system);
together with the Customer’s representative, establish the timing of acceptance tests and the work schedule (The organization of work is built taking into account the constant and uniform workload of testers).
The site or team must be led by a qualified engineer with experience in electrical testing and measurement. The head of the unit can be an engineer or a qualified technician, depending on the complexity of the test object.
2.4. Each section, team, unit must receive a specific task and deadline for completing the work.
2.5. Comments on the design documentation, installation work and electrical installation are recorded in the act for bringing to the attention of the relevant organizations and their further elimination. All comments, as well as data on the replacement of heating cables, structures, materials, instruments, apparatus, on new test methods used that are of technical interest, are also recorded in the act. This particularly applies to imported electrical equipment and electrical installations.
2.6. Selection of acceptance testing methods and their sequence
carried out by the team leader in accordance with this Methodology for conducting commissioning tests and work schedule. Changing the order and schemes of specific types of tests given in this Methodology is strictly prohibited!
INSPECTION OF SEUNK
3.1 Inspection of the control unit must precede testing and is carried out with the control unit completely switched off.
3.2 When carrying out an inspection, it is necessary to make sure that the installed SEUNK:
satisfies the requirements of safety regulations, current standards, design and technical documentation for components and control systems in general;
correctly selected and installed in accordance with the requirements of the set of standards GOST R 50571. VTT and the manufacturer’s instructions;
has no visible damage that reduces its safety and performance.
measures of protection against electric shock;
selection of supply conductors based on long-term permissible current and voltage loss;
selection of protection and alarm devices and settings for their operation;
selection and matching of connecting and heating cables;
the presence and correct location of thermostats and disconnecting and switching devices;
correct connection of conductors;
availability of warning labels and diagrams;
circuit markings;
accessibility for ease of operation and maintenance.
SEUNK TESTS
4.1 The following checks, measurements and tests must be carried out on all newly installed SESUNK (preferably in the given sequence):
Checking the continuity of protective conductors (checking the integrity of grounding circuits).
Measurement of insulation resistance SEUNK.
Checking protection that ensures automatic shutdown of power supplies.
Electrical insulation strength test.
Heating cable ohmic resistance test.
Measurement of grounding resistance.
Checking the functionality of the electronic control system.
4.4 Checking the continuity of protective conductors (checking the integrity of grounding circuits).
4.4.1 It is recommended to perform tests using a power source having an open circuit voltage of 4 to 24 VDC or AC with a test current of at least 0.2A. It is allowed to use electrical measuring instruments designed to measure the resistance of grounding wiring for testing.
4.4.2 There should be no breaks or unsatisfactory contacts in the wiring connecting the metal sheaths of the cables and all open and third-party conductive parts with the PE bus of the group panel from which the power supply unit is supplied.
4.4.3 Contact resistance is not standardized, but should not exceed 0.05 Ohm.
4.5 Measurement of insulation resistance SEUNK.
4.5.1 Measurements are carried out with a megger for a voltage of 1000 V.
4.5.2 The insulation resistance of heating cables is measured between each heating core and the metal sheath (for cables without a metal sheath - between the heating core and the metal mesh connected to the grounding device of the power supply installation), and for self-regulating cables - between the current-carrying cores connected together and the metal sheath. To avoid failure of thermostats during measurements, they should be disconnected from the circuits in which the measurement is being carried out.
4.5.3 For heating cables, the insulation resistance must be at least 1 MOhm, and for other SEUNK elements - at least 0.5 MOhm.
4.6 Checking the protection that ensures automatic shutdown of power supplies.
4.6.1 The effectiveness of protection against indirect contact by automatic switching off of the power supply should be verified by carrying out the following tests:
a) Measurement of the resistance of the phase-zero loop.
It is carried out at the point of connection of the heating cable to other elements of the SEUNK that is accessible for measurement (terminals of the thermostat, contactor, magnetic starter). When connecting a heating cable to the terminals of the thermostat, the measurement should be carried out on the network terminals of the thermostat in order to prevent failure of the latter.
The value of the measured loop impedance must comply with the requirements of 1.7.79 PUE, as well as 3.6.1 VTT. If there are calculations of the resistance of the phase-zero loop or the resistance of the protective conductors and the SEUNK device allows you to check the length and cross-section of the conductors (heating of roofs, gutters, etc.), the above measurement is not necessary. In this case, checking the continuity of the protective conductors is sufficient.
b) Checking the characteristics of protective devices:
setting currents of automatic circuit breakers and currents of fuse links;
RCD response characteristics; RCD test methods must comply with GOST R 50571.16-99 Appendix B.
4.7 Electrical insulation strength test.
4.7.1 It is carried out by measuring the one-minute value of insulation resistance with a 2500 V megohmmeter. If the resistance value is less than that given in Table B1, Appendix B, a voltage test of 1000 V industrial frequency must be carried out in accordance with 1.8.34 PUE.
4.7.2 Tests are carried out in accordance with the procedure for checking insulation resistance (Appendix B).
4.8 Heating cable ohmic resistance test.
4.8.1 Testing for all types of heating cables was carried out at a heating core temperature of 20°C (cold state).
If environmental conditions differ from the table ones, then the obtained resistance values of the heating cable cores must be adjusted to t=20°С according to the formula:
Where t- ambient temperature during measurement (°C), R 20 - resistance of the heating cable reduced to t= 20°С (Ohm), R t- resistance of the laid heating cable (Ohm), L- length of laid heating cable (m).
4.8.2 The ohmic resistance values obtained from the measurement results may differ from the nominal value given in the cable data sheet within -5%...+10%.
4.9 Measurement of grounding resistance.
4.9.1 It is carried out only in those SEUNK. for which a separate grounding device is provided, regardless of the grounding device in the supply network.
4.9.2 The value of the current spreading resistance of the grounding conductor must correspond to the design.
4.10 Checking the functionality of the electronic control system.
4.10.1 The inspection is carried out in accordance with the manufacturers' instructions depending on the type of heating system and should include thermal tests.
4.10.2 Thermal tests are carried out for a fully assembled SEUNK connected to a power source.
4.10.3 It is recommended to carry out thermal tests of fully assembled SEUNK:
a) when heating floors - at the calculated air and room temperature for at least four hours for floors with heat accumulation, and at least one hour for thin floors;
b) when heating external areas - at the design ambient temperature. The test time depends on the type of heated area and the design of the heating system, but should not be less than four hours;
c) when heating pipelines - at the design ambient temperature. The test time depends on the diameter of the pipeline and the type of liquid product, but should not be less than three hours.
4.10.4 In order to reduce the time required for commissioning of the electronic control system, upon agreement with the customer, thermal tests can be carried out at an ambient temperature different from the design temperature.
4.10.5 The results of thermal tests are considered satisfactory if during their process there were no unauthorized operations of switching and protective equipment, no local overheating of the heated object was observed, and if the insulation resistance of the heating cable, measured with a megohmmeter immediately after disconnecting the heating system from the network (in a hot state), is not less than 0.5 MOhm.
UDC 621.313.1.01.7.001.4(083.96)
Ministry of Fuel and Energy of the Russian Federation
ORGRES SERVICE OF EXCELLENCE
METHODOLOGICAL INSTRUCTIONS
ON TESTING GENERATORS FOR HEATING
RD 34.45.309-92
Developed by: All-Union Scientific Research Institute of Electric Power Industry (VNIIE) Performers: L.G. Volodarsky, E.V. Gushchin, O.I. Ibadov, G.A. Ostroumova, A.P. Chistikov U confirmed: Department of Scientific and Technical Development 01/29/92 Deputy Head K.M. Antipov These Guidelines establish the scope and procedure for conducting heating tests on generators in operation at power plants. The guidelines are intended for workers of power plants and organizations involved in testing generators for heating. With the release of these Methodological Instructions, the previously published “Methodological Instructions for Conducting Heating Tests on Generators” (Moscow: SPO Soyuztekhenergo, 1984) are cancelled.a common part
Heating tests of generators must be carried out no later than 6 months after commissioning. Subsequently, during operation, control heating tests are carried out periodically (once every 10 years) under one or two operating modes. Heating tests are also carried out after a complete replacement of the rotor or stator winding, or reconstruction of the cooling system. Generators with a capacity of up to 12 MW do not need to be tested. The first seven sections of this document provide recommendations for conducting operational heating tests in order to obtain the heating characteristics of the generator, determine their compliance with the requirements of standards and technical delivery conditions, and determine the loads permissible for operation. In some cases, tests may be carried out to determine the causes of problems in the generator cooling system. Based on the results of these tests, the highest permissible operating temperatures are established (rounded up to 5 °C) of the stator windings, rotor, active steel and cooling media at the exit from the windings or stator core during continuous operation of the generator with rated load at rated values of power factor, voltage and cooling media parameters. For turbogenerators for which, in accordance with GOST 533-85 and technical conditions, long-term operation is allowed with an increased active load compared to the rated load at established values of the power factor and cooling parameters, the highest permissible operating temperatures should be determined when operating with the rated and maximum continuous load . The highest permissible operating temperatures for such machines should be taken to be the maximum temperatures defined for these modes. If the highest temperatures obtained from the results of heating tests, when operating generators at rated or long-term maximum load, are higher than the maximum permissible values given in GOST 533-85, GOST 5616-81, technical conditions or specified by the manufacturer in the technical description and instructions operating instructions, then the power of the generator under test should be accordingly limited to a value at which heating will not exceed the maximum permissible until the reasons that caused these increased heating are clarified and eliminated. The power plant must report the power limitation to the Technical Directorate of Rosenergo Corporation and the manufacturer. If the highest temperatures obtained from the results of heating tests are below the maximum permissible values, then this cannot serve as a basis for re-labeling the generator to higher power. If it is necessary to re-mark the generator, when an increase in power is desirable to deliver the “locked” power of the turbine and is not limited by the power of the transformer, additional special tests must be carried out according to a program drawn up for each case. Before these tests, appropriate calculations must be carried out and the generator must be equipped with additional means of measuring temperature and other quantities. It should be borne in mind that even after carrying out the appropriate tests, remarking can only be done with the permission of the manufacturer and the Technical Department. The last four sections provide recommendations for conducting heating tests in underexcited, asynchronous, single-ended, and to determine the possibility of re-marking generators. Recommendations have been developed for generators with both indirect and direct cooling.1. Conditions for conducting heating performance tests
1.1. Tests must be carried out on a generator in good condition, with all its main parts and auxiliary devices operating normally. Particular attention should be paid to the condition of the cooling system. It is also necessary to check the rotor winding for the absence of short-circuited turns. The check is carried out both in a stationary state and when the rotor rotates at different speeds, up to the nominal (according to GOST 10169-77). For rotors with turn faults, it is impossible to measure the temperature using the resistance method, since the value of the measured resistance differs from the actual one, therefore heating tests of such machines must be carried out after the turn shorts have been eliminated. 1.2. All instruments used to make measurements must be tested and have the stamps of the State Inspectorate. The use of devices that have not passed metrological verification is prohibited. 1.3. On hydrogen-cooled turbogenerators that are approved for air-cooled operation, tests are carried out with both hydrogen and air cooling. On hydrogen-cooled turbogenerators, which, according to their tabular data, can operate at different hydrogen pressures, tests must be carried out for the specified hydrogen pressure values. Tests at hydrogen pressure exceeding the nominal pressure, in cases where the maximum pressure is not indicated in the generator passport, are carried out in agreement with the manufacturer. Tests at elevated pressure should be preceded by pressure testing of the generator together with the gas-oil system with an excess air pressure of 0.05 MPa (0.5 kgf/cm2) exceeding the pressure at which the tests will be performed.2. Scope of heating performance tests
The scope of testing includes: 2.1. Determination of the resistance of the rotor winding and embedded resistance thermal converters in a cold state. 2.2. Carrying out four heating experiments with loads of about 0.6; 0.75; 0.9 and 1.0 R n (active power) at rated or close to it power factor. In this case, the machine voltage should not differ from the nominal voltage by more than 5%. It is allowed to carry out heating tests at a voltage higher than the rated voltage by more than 5% (according to the operating conditions of the power plant). However, the total power of the generator should not exceed that set by the manufacturer. In accordance with GOST 11828-86 "Rotating electric machines. General test methods" it is possible to test at three or four different loads within 0.6 rated power up to the maximum possible under the operating conditions of the power plant (but not lower than 0.9 rated current), at which the intervals between the squares of the currents of the working circuit of the windings would be approximately the same in order to, if necessary, provide a more accurate extrapolation of the obtained dependencies. During the experiments, the following should be measured: a) electrical quantities characterizing the operation of the generator; b) temperature of the winding and stator steel according to the installed resistance thermal converters; c) temperature of the rotor winding using the resistance method; d) the temperature of the incoming and outgoing cooling gas, and for liquid-cooled generators, also the temperature of the incoming and outgoing liquid; e) temperature of cooling water at the inlet and outlet of gas coolers and heat exchangers; f) water flow through gas coolers, and for liquid-cooled generators, liquid flow through the windings and core and liquid pressure at the inlet and outlet of the windings; g) gas flow through the generator; h) pressure and purity of hydrogen. Determination of water flow through coolers is desirable in all cases and mandatory when testing new types of generators and new types of coolers, as well as when the inlet gas temperature is elevated above normal and other problems in the cooling system. Determining gas flow is mandatory in cases where there is increased heating of generator parts and cooling gas, temperature unevenness or other problems in the cooling system. 2.3. Determination of the control characteristic, rated and maximum excitation currents under rated conditions and when the stator voltage and current deviate by 5% of the rated values.3. Carrying out measurements and requirements for measuring instruments
3.1. During heating tests and when determining the control characteristic, the following electrical quantities are measured: a) active and reactive power; b) current in the stator winding (in three phases); c) stator winding voltage (in three phases); d) excitation current; e) voltage on the rotor rings; e) frequency. All specified values are determined both by station switchboard devices and by control devices installed at the time of testing. It is allowed to determine the frequency of the current using panel devices. Measuring instruments in accordance with the requirements of GOST 11828-86 should be selected so that the measured values are within 30-95% of the scale. The accuracy class of control devices must be no lower than 0.5, and for devices installed in the excitation circuit, no lower than 0.2. Stator monitoring devices are connected to station instrument transformers. Installation of special instrument transformers is not required. It is only necessary to check whether the current transformers are overloaded as a result of switching on additional devices, and, if necessary, take measures to unload them during the tests. The control shunt installed in the rotor winding circuit must have an accuracy class of at least 0.2. In the absence of shunts of this class, shunts of class 0.5 can be used without reducing the requirements for the devices that are connected to them. It is allowed to use operational shunts of class not lower than 0.5. The power factor is determined by calculation based on the readings of control instruments installed to measure current, active power and stator voltage. It is possible to determine the power factor by the ratio of the readings of two wattmeters installed to measure active power in accordance with. In this case, it is necessary to ensure that the measured values of currents and voltages are not lower than 30% of the rated currents and voltages of the wattmeters used. When taking measurements on more than one instrument, it is recommended to take readings from all instruments for each measurement simultaneously. This is mandatory when measuring resistance using the ammeter and voltmeter method and three-phase current power using the two-wattmeter method. 3.2. Before heating tests, the resistance of the rotor winding should be measured at direct current in a practically cold state ( r x) and the temperature at which this measurement was carried out ( x) according to GOST 11828-86. The value of this resistance is the starting point for determining the temperature rise of the rotor winding during heating tests. According to GOST 183-74, the practically cold state of the machine is taken to be one in which the temperature of any part of the machine differs from the ambient air temperature by no more than 3 °C. The winding temperature in a cold state on a removed rotor or on an open machine is measured by several (at least four to five) expansion thermometers installed on turbogenerators under the bandages and along the rotor barrel, and on hydrogenerators - at different poles along the winding. The ambient air temperature is determined according to GOST 11828-86 as the arithmetic mean of the readings of several thermometers located at different points around the generator, at a height equal to half the height of the generator, and at a distance of 1 to 2 m from the generator. If, due to operating conditions, the generator cannot be opened, it is allowed to measure r X on a closed generator. In this case, it is necessary to periodically monitor the cooling of the generator using all installed temperature indicators (resistance thermal converters or thermocouples and expansion thermometers) and begin measuring r X only after reaching a practically cold state. Simultaneously with measurement r X The temperature is measured using all installed temperature meters. The average of all obtained temperature values is taken as the winding temperature. Expansion thermometers must have a division value of no more than 1 °C. For water-cooled rotors, the winding temperature is taken to be the average of the temperatures of water entering and exiting the winding, provided that these values differ from each other by no more than 1 °C, and the incoming water temperature does not change by more than 0.5 °C during the 30 min preceding the resistance measurement. To measure r x follows the voltmeter and ammeter method. Measuring instruments must have an accuracy class of at least 0.2. When measured using an ammeter-voltmeter method, the shunt must have an accuracy class of at least 0.2. As test practice shows, it is easiest to measure the resistance of the rotor winding by supplying power from a battery or a special direct current source that provides a steady current of about 10 A, with the same instruments that will be used for measurements in load modes. Power is supplied to the rotor winding using special clamps or bands made of aluminum or copper bars, placed on the rotor rings. The voltmeter must be connected at separate ends directly to the rings. The connection is usually made using probes and only for the duration of the readings on the instruments.Russian FederationRD
RD 153-34.1-26.303-98 Guidelines for conducting operational tests of boiler installations to assess the quality of repairs
set bookmark
set bookmark
RD 153-34.1-26.303-98
METHODOLOGICAL INSTRUCTIONS
ABOUT PERFORMANCE TESTS
BOILER INSTALLATIONS FOR REPAIR QUALITY ASSESSMENT
Date of introduction 2000-04-03
DEVELOPED by the Open Joint Stock Company "Company for setting up, improving technology and operating power plants and networks ORGRES"
Performer G.T. Levit
APPROVED by the Department of Development Strategy and Scientific and Technical Policy of RAO "UES of Russia" 01.10.98
First Deputy Chief A.P. Bersenev
1. GENERAL PART
1.1. The tasks of operational tests (acceptance tests) are determined by the "Methodology for assessing the technical condition of boiler installations before and after repairs", according to which, when conducting tests after a major overhaul, they must be identified and compared with the requirements of normative and technical documentation (NTD) and test results after the previous repair the values of the indicators listed in Table 1 of these Guidelines. The specified Methodology also defines as desirable tests before repair to clarify the scope of the upcoming repair.
Table 1
Statement of technical condition indicators of the boiler installation
Index | Indicator value |
|||
after the last major renovation | after real renovation | before the current renovation |
||
1. Fuel, its characteristics | ||||
2. Number of operating dust preparation systems* | ||||
3. Dust fineness ()*, % | ||||
4. Number of working burners* | ||||
5. Excess air behind the superheater * | ||||
6. Steam production, reduced to nominal parameters, t/h | ||||
7. Temperature of superheated steam, °C | ||||
8. Temperature of reheat steam, °C | ||||
9. Feedwater temperature, °C | ||||
10. Temperature at control points of the high pressure steam-water path. and intermediate superheater, °C | ||||
11. Maximum measurement of the temperature of the walls of the heating surface coils in characteristic places | ||||
12. Suction of cold air into the firebox | ||||
13. Cold air suctions into dust preparation systems | ||||
14. Suction cups in the convective flue ducts of the boiler | ||||
15. Suction cups in the flue ducts from the air heater to the smoke exhausters | ||||
16. Vacuum in front of the guide vanes of smoke exhausters, kg/m | ||||
17. Degree of opening of the guide vanes of smoke exhausters, % | ||||
18. Degree of opening of fan guide vanes, % | ||||
19. Flue gas temperature, °C | ||||
20. Heat loss with flue gases, % | ||||
21. Heat loss with mechanical incomplete combustion, % | ||||
22. Efficiency boiler "gross", % | ||||
23. Specific electricity consumption for dust preparation, kWh/t of fuel | ||||
24. Specific electricity consumption for traction and blast, kWh/t steam | ||||
* Accepted with a regime card. |
The efficiency (%) of the boiler is determined by the reverse balance using the formula
Where - heat loss with exhaust gases, %;
Heat loss with chemical incomplete combustion, %;
Heat loss to the environment, %;
Heat loss with physical heat of slag, %.
3.2. Due to the fact that the purpose of these Guidelines is to assess the quality of repairs, and comparative tests are carried out under approximately the same conditions, heat loss with flue gases can be determined with sufficient accuracy using a somewhat simplified formula (in comparison with that adopted in):
Where is the coefficient of excess air in the exhaust gases;
Flue gas temperature, °C;
Cold air temperature, °C;
Heat loss with mechanical incomplete combustion, %;
A correction factor that takes into account the heat introduced into the boiler with heated air and fuel;
Coefficients depending on the type and reduced moisture content of the fuel, the average values of which are given in Table 3.
Table 3
Average coefficient values, Andto calculate heat loss
Anthracite, semi-anthracite, lean coals | |||
Stone coals | |||
Brown coals | |||
Fuel oil, oil | |||
Natural gases | |||
Associated gases | |||
The cold air temperature (°C) is measured on the suction side of the blower fan before the control hot air is introduced.
The correction factor is determined by the formula
It makes sense to take physical heat of fuel into account only when using heated fuel oil. This value is calculated in kJ/kg (kcal/kg) using the formula
Where is the specific heat capacity of fuel oil at the temperature at which it enters the furnace, kJ/(kg °C) [kcal/(kg °C)];
Temperature of fuel oil entering the boiler, heated outside it, °C;
Heat share of fuel oil in the fuel mixture.
Specific heat consumption per 1 kg of fuel introduced into the boiler with air (kJ/kg) [(kcal/kg)] when preheating it in air heaters is calculated by the formula
Where is the excess air entering the boiler in the air duct in front of the air heater;
Increase in air temperature in heaters, °C;
Reduced fuel humidity, (kg·%·10)/kJ [(kg·%·10)/kcal];
Physical constant equal to 4.187 kJ (1 kcal);
Lower calorific value, kJ (kcal/kg).
The normalized humidity of solid fuel and fuel oil is calculated based on the current average data at the power plant using the formula
Where is the fuel moisture per working mass, %.
When burning fuel of different types and brands together, if the coefficients , and for different brands of solid fuel differ from one another, the given values of these coefficients in formula (28) are determined by the formula
Where , ... are the thermal fractions of each fuel in the mixture;
Coefficient values (,) for each fuel
3.3. Heat losses with chemical incomplete combustion of fuel are determined by the formulas:
for solid fuel
for fuel oil
for natural gas
The coefficient is taken equal to 0.11 or 0.026, depending on whether it is determined in kcal/m or kJ/m.
The value is determined by the formula
When calculating in kJ/m, the numerical coefficients in this formula are multiplied by a coefficient = 4.187 kJ/kcal.
In formula (37), and are the volumetric contents of products of incomplete combustion of fuels as a percentage relative to dry gases. These values are determined using chromatographs using previously selected gas samples. For practical purposes, when the boiler operating mode is carried out with excess air providing a minimum value of , it is quite sufficient to substitute only the value into formula (37). In this case, you can get by with simpler gas analyzers like "Testo-Term"
3.4. Unlike other losses, determining heat losses with mechanical incomplete combustion requires knowledge of the characteristics of the solid fuel used in specific experiments - its calorific value and working ash content. When burning hard coals of unknown suppliers or brands, it is useful to know the volatile yield, since this value can affect the degree of fuel burnout - the content of combustibles in the entrainment and slag.
Calculations are carried out using the formulas:
Where and is the proportion of fuel ash falling into a cold funnel and carried away by flue gases;
The heat of combustion of 1 kg of fuel is 7800 kcal/kg or 32660 kJ/kg.
It is advisable to calculate heat losses with entrainment and slag separately, especially with large differences in and. In the latter case, it is very important to clarify the meaning of , since the recommendations on this issue are very approximate. In practice, they depend on the size of the dust and the degree of contamination of the furnace with slag deposits. To clarify the value, it is recommended to carry out special tests.
When burning solid fuel in a mixture with gas or fuel oil, the value (%) is determined by the expression
Where is the share of solid fuel by heat in total fuel consumption.
When several grades of solid fuel are simultaneously burned, calculations using formula (39) are carried out using the weighted average values and .
3.5. Heat losses to the environment are calculated based on recommendations. When conducting experiments at a load less than the nominal one, recalculation is carried out using the formula
3.6. Heat losses with the physical heat of the slag are significant only with liquid slag removal. They are determined by the formula
Where is the enthalpy of ash, kJ/kg (kcal/kg). Determined by .
The ash temperature for solid slag removal is assumed to be equal to 600 °C, for liquid ash removal it is equal to the temperature of normal liquid slag removal or +100 °C, which are determined by and.
3.7. When conducting experiments before and after repairs, it is necessary to strive to maintain the same maximum number of parameters (see paragraph 1.4 of these Guidelines) in order to minimize the number of corrections that need to be introduced.
Only a correction to the cold air temperature can be determined relatively simply if the temperature at the inlet to the air heater is maintained at a constant level. This can be done based on formula (28), determining for different values of . Taking into account the influence of deviations of other parameters requires experimental verification or machine calibration calculations of the boiler.
4. DETERMINATION OF HARMFUL EMISSIONS
4.1. The need to determine the concentrations of nitrogen oxides () is also dictated by the urgency of the problem of reducing harmful emissions from power plants, which has received increasing attention over the years. This section is missing.
4.2. To analyze flue gases for the content of harmful emissions, portable gas analyzers from many companies are used. The most common electrochemical devices at Russian power plants are the German company Testo. The company produces devices of various classes. Using the simplest device "Testo 300M" you can determine the content in dry flue gases in % and volume fractions (ppm)* and automatically convert the volume fractions into mg/nm at = 1.4. Using the more complex Testo-350 device, in addition to the above, it is possible to determine the temperature and velocity of the gas at the probe insertion point, and to determine the efficiency by calculation. boiler (if the probe is inserted into the flue behind the boiler), separately determine using an additional unit ("Testo-339") the contents of and, as well as when using heated hoses (up to 4 m long).
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* 1 ppm=1/10 volume.
4.3. In boiler furnaces, when fuel burns, nitrogen monoxide is mainly formed (95-99%), and the content of more toxic dioxide is 1-5%. Partial uncontrolled additional oxidation occurs in the boiler flues and further in the atmosphere. Therefore, conditionally, when converting the volume fraction (ppm) into a standard mass value (mg/nm) at = 1.4, a conversion factor of 2.05 is applied (and not 1.34, as for ). The same coefficient is also adopted in Testo devices when converting values from ppm to mg/n
4.4. The content of nitrogen oxides is usually determined in dry gases, therefore water vapor contained in flue gases must be condensed and removed as much as possible. To do this, in addition to the condensate drain that Testo devices are equipped with, it is advisable to install a Drexler flask in front of the device for short lines to organize gas bubbling through the water.
4.5. A representative gas sample for determining , and can also be taken only in the section behind the smoke exhauster, where the gases are mixed, while in sections closer to the firebox, distorted results can be obtained due to sampling from a plume of flue gases characterized by an increased or decreased content of , or . At the same time, when studying in detail the reasons for increased values, it is useful to take samples from several points along the width of the flue. This makes it possible to associate the values with the organization of the combustion regime, to find regimes characterized by a smaller spread of values and, accordingly, a smaller average value
4.6. The determination before and after repair, as well as the determination of other boiler indicators, should be carried out at rated load and in the modes recommended by the operating map. The latter, in turn, should be focused on the use of technological methods for suppressing nitrogen oxides - organizing staged combustion, introducing recirculation gases into the burners or into air ducts in front of the burners, different supplies of fuel and air to different tiers of burners, etc.
4.7. When conducting experiments on maximum reduction, which is often achieved by reducing the excess air in the control section (behind the superheater), growth should be avoided. The limit values for newly designed or reconstructed boilers, according to , are: for gas and fuel oil - 300 mg/nm, for pulverized coal boilers with solid and liquid slag removal - 400 and 300 mg/nm, respectively.
Conversion from ppm to mg/nm is made by multiplying by specific gravity 1.25 and 2.86
4.8. To eliminate errors when determining the content in flue gases, it is necessary to sample the gases behind the smoke exhauster and, in addition, to prevent the condensation of water vapor contained in the flue gases, since it dissolves well in water with the formation. To do this, at a high temperature of the flue gases, which prevents condensation of water vapor in the gas intake tube and hose, make them as short as possible. In turn, in case of possible moisture condensation, heated (up to a temperature of 150 ° C) hoses and an attachment for drying flue gases should be used.
4.9. Sampling downstream of the smoke exhauster is associated with sub-zero ambient temperatures for a fairly long period, and Testo devices are designed to operate in the temperature range of +4+50 °C, so for measurements downstream of the smoke exhauster in winter it is necessary to install insulated cabins.
For boilers equipped with wet ash collectors, the definition behind the smoke exhauster allows for partial absorption in the scrubbers to be taken into account.
4.10. To eliminate systematic errors in determination and compare them with generalized materials, it is advisable to compare experimental data with calculated values. The latter can be determined by and .
4.11. The quality of repair of a boiler installation, among other indicators, is characterized by emissions of solid particles into the atmosphere. If it is necessary to determine these emissions, and should be used.
5. DETERMINATION OF STEAM TEMPERATURE LEVEL
AND THE RANGE OF ITS REGULATION
5.1. When conducting operational tests, it is necessary to identify the possible range of steam temperature control using desuperheaters and, if this range is insufficient, determine the need to intervene in the combustion mode to ensure the required level of superheat, since these parameters determine the technical condition of the boiler and characterize the quality of repairs.
5.2. The steam temperature level is assessed based on the value of the conditional temperature (steam temperature in the event of desuperheater shutdown). This temperature is determined from tables of water vapor based on conventional enthalpy:
Where is the enthalpy of superheated steam, kcal/kg;
Decrease in steam enthalpy in the desuperheater, kcal/kg;
A coefficient that takes into account the increase in heat absorption of the superheater due to an increase in temperature pressure when the desuperheater is turned on. The value of this coefficient depends on the location of the desuperheater: the closer the desuperheater is located to the outlet of the superheater, the closer the coefficient is to unity. When installing a surface desuperheater on saturated steam, it is assumed to be 0.75-0.8.
When using a surface desuperheater to regulate the steam temperature, in which the steam is cooled by passing part of the feed water through it,
Where and is the enthalpy of feed water and water at the inlet to the economizer;
and - consumption of superheated steam and continuous blowdown, by the value of which the feed water consumption differs from the steam consumption.
When using injection desuperheaters
Where is the water consumption for injection (own condensate or feed water);
Enthalpy of condensate, in the absence of subcooling, corresponding to the enthalpy of water on the saturation curve at pressure in the drum; when injection of feed water is replaced.
If there is no measurement of water flow for injection, the latter can be determined by the formula
Where and is the enthalpy of steam before and after the desuperheater.
In cases where there are several injections on the boiler, the water consumption for the last injection along the steam flow is determined using formula (46). For the previous injection, instead of in formula (46), one should substitute (-) and the values of the enthalpy of steam and condensate corresponding to this injection. Formula (46) is written similarly for the case when the number of injections is more than two, i.e. is substituted (--) etc
5.3. The range of boiler loads within which the nominal fresh steam temperature is provided by devices designed for this purpose without interfering with the operating mode of the furnace is determined experimentally. The limitation for a drum boiler when the load decreases is often associated with leakage of the control valves, and when the load increases, it can be a consequence of the lower feedwater temperature due to the relatively lower steam flow through the superheater at a constant fuel consumption. To take into account the influence of the feed water temperature, you should use a graph similar to that shown in Fig. 3, and to convert the load to the nominal feed water temperature - in Fig. 4.
Rice. 3. An example of determining the necessary additional decrease in the temperature of superheated steam in desuperheaters when lowering
feed water temperature and maintaining constant steam flow
Note. The graph is based on the fact that when the feed water temperature decreases, for example from 230 to 150 °C, and the boiler steam output and fuel consumption remain unchanged, the enthalpy of steam in the superheater increases (at = 100 kgf/cm) by 1.15 times (from 165 to 190 kcal/kg), and the steam temperature from 510 to 550 °C
Rice. 4. An example of determining the boiler load, reduced to a nominal feed water temperature of 230 °C (at =170 °C and =600 t/h =660 t/h)
Note. The graph was built under the following conditions:
545/545 °C; =140 kgf/cm; = 28 kgf/cm; =26 kgf/cm; =320 °C; =0.8
5.4. When conducting comparative tests of the boiler before and after repair, the load range at which the nominal temperature of the reheat steam is maintained must also be experimentally determined. This means the use of design means for regulating this temperature - a steam-steam heat exchanger, gas recirculation, gas bypass, in addition to an industrial steam superheater (boilers TP-108, TP-208 with split tail), injection. The assessment should be carried out with the high-pressure heaters turned on (design feedwater temperature) and taking into account the steam temperature at the inlet to the reheater, and for double-shell boilers - with the same load on both buildings.