Why is low voltage dangerous? What to do if the network voltage is low? Photo of low voltage in the network
Substation installed nearby: increased voltage. Installed far away – low voltage.
Below is a piece of paper with real data that I left at the site after installation.
Established voltage relay limits and real overvoltages by phase
This is a problem on the side of the energy supply organization, and installed relay voltage switched off the problematic phase, which is what should happen.
What to do if there is increased voltage
The exit routes are as follows.
1. Call a representative of the energy supply organization to carry out control measurements, based on the results of which a report should be drawn up.
Action must be taken on this act, or you can refuse to pay for the energy consumed for reasons of unsatisfactory quality.
2. Temporarily distribute (reconnect) the load from the second phase to 1 and 3 phases.
3. Install a voltage stabilizer on the 2nd phase, this will lower the voltage to normal and completely eliminate the problem. Moreover, this will improve the voltage stability in case of voltage drops at the input from 130
up to 270 V.
The asking price (minimum) is 14,000 for a 10 kW stabilizer plus 3,000 rubles for materials and installation work. Total – 17 tr.
4. Ignore the problem by setting the max. the voltage relay limit for the 2nd phase is at the level of 257...259 Volts, so that it does not work often.
Another option is to insist that the voltage at the output of the energy substation transformer be switched to a lower one. But, as already mentioned, residents of distant houses may suffer.
Or, connect to a neighboring street if it is powered by another transformer.
What to do if the voltage is low.
The most common case is when the voltage in the house is greatly underestimated. This occurs mainly in the private sector; old thin long wires with significant resistance come to houses.
As we know from Ohm's law, the greater the current, the more the voltage drops on the wires. After all, wires have resistance.
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As we know, there is no money to globally correct the situation by changing the supply lines. Therefore, everyone gets out of the situation as best they can. Namely, there are two options:
- connect and make an input from another line, or phase. Or lay a separate SIP from the substation. This may not always be technically and financially possible.
- install a voltage stabilizer that will “pull” the voltage to normal.
In 99% of cases, people go for option 2 because it is easier, faster and cheaper.
What does this lead to? The voltage in the house will, of course, rise to acceptable limits, thanks to the efforts of the stabilizer. However, energy cannot be taken from nowhere - the voltage at the output of the stabilizer increases due to an increase in the current at its input. This means that there is also current in all wires BEFORE the stabilizer, starting from the 0.4 kV substation. And the current is greater - which means the voltage drop is also greater, and the voltage for those who did not install a stabilizer is less! That is, installing stabilizers aggravates the situation as a whole.
By the way, an important note! If the stabilizer is installed in a house where there is often low voltage, then you need to take into account that the current at its input can increase greatly, sometimes by 2.5 times! Therefore, the cross-section of the input wires should be a step or two larger than the output wires.
And the output wires, of course, are selected from the load.
In general, the main idea is that before eliminating the consequences of low or high voltage, think about eliminating the cause.
How do you solve these problems? Share and ask questions in the comments.
Manufacturers of borehole pumps indicate in their passports that the voltage in the supply network must be within certain limits. As a rule, limits of minus 10% - +6% are indicated (taking into account tolerances in the voltage value - 220 - 240V and losses in the power cable). In other words, in borehole pump The voltage must be within the range of 180 - 255V. Let's consider why operating the pump at a voltage that is higher or lower than the given values can lead to its failure.
Overvoltage
With increased voltage everything is clear. Increased voltage automatically means increased current, which means increased heat generation in the winding electric motor. During prolonged operation in this mode, due to increased heat generation, the winding insulation quickly ages, its service life decreases sharply and, in the end, it will occur. short circuit in an electric motor. In this case, a minimum rewinding of the electric motor is required.
Undervoltage
What is the danger of low voltage? The fact is that when the voltage decreases, the efficiency of the pump deteriorates and the power consumption automatically increases, and therefore the current. So, when the voltage drops by 10%, the current increases by 5%, and the temperature increases by 20%! At the same time, do not forget that the pump is cooled by the pumped water. Efficiency has decreased - the volume of pumped water has decreased - heat dissipation has deteriorated - the pump temperature has increased. In this case, the following events are possible:
1. The shaft bearings of the well pump will melt.
2. A short circuit will occur in the motor winding.
3. The tightness will be broken rubber seals in the pump, water will get inside and again a short circuit will follow.
As you can see, low voltage is even more dangerous than high voltage. Since replacing a bearing, and maybe a shaft, is even more troublesome than rewinding an electric motor.
How to avoid power surges?
Let's start with the fact that some control systems protect pumps from power surges by turning off the well pump (using protective voltage relays such as CP-720). What if such leaps occur constantly? Then pump for a long time will not work, and what kind of quality water supply can we talk about? The only way out in this situation is to install a voltage stabilizer. But here there is one big BUT. The fact is that when the pump is turned on, the starting currents increase by 2-3 times. Therefore, the stabilizer must calculate a power that is at least 2-3 times higher than the rated power of the pump. And there must also be a reserve. Therefore, you need to multiply the engine power by five. That is, if the well pump has a power of 1 kW, the stabilizer must have 5 kW! Stabilizers of this power cost at least 20 thousand rubles (such as the Shtil R 4500, 4.5 kVA AC voltage stabilizer, costing 23 thousand rubles).
From our point of view, it is more advisable to use a soft starter, which allows for a smooth start of the pump. In this case, the starting currents are not much different from the rated ones, and a 1.5 kW stabilizer for a one-kilowatt pump will be sufficient. In this case, the cost will be: 4000 rubles. (softstarter type PSR3-600-70 1.5 kW) + 6-8 thousand rubles (stabilizer type "Shtil" R 1200, 1.2 kVA (6500 rub.) or "Shtil" R 2000, 2 kVA (10 thousand. rubles)). Total 10-12 thousand rubles plus system soft start, which significantly increases the service life of the pump motor.
Residents of the private sector often encounter low voltage; this problem also occurs in city apartments. First of all, you should find out whose fault it is - the electricity supplier or the consumer and, depending on the reason, take action.
Insufficient voltage in the house - possible causes
Low voltage in the network is an unpleasant phenomenon, but many people deal with it. Bad light, when the light bulb only indicates its presence, it’s not the biggest problem. It’s worse when it’s impossible to do laundry, boil water, cook food on an electric stove, or the refrigerator works intermittently. This happens when the voltage drops to critical value, but 180 Volts, when everything seems to be working, are also not very pleasing. Devices consume the same current as at normal voltage, and motors consume even more current, but perform their functions over a longer period of time.
The electricity supplier is obliged to provide services that meet the standards: 220 V at the entrance to the apartment with permissible deviations 198–242 V. Why regulatory requirements sometimes violated? One of the reasons is the aging of power lines, their poor quality maintenance, and repairs are rarely carried out. Equipment is often worn out, outdated and unresponsive modern requirements. There are also errors in planning power lines and supply lines to houses, when one phase is overloaded and the other is underloaded.
The reasons also lie in the consumers themselves. If in Soviet times there was a 6.5 A fuse under the meter, this meant that residents simultaneously consumed a maximum of 1.5 kW. Now one kettle has a power of 2 kW, how many more? household appliances, various power tools are available in modern house? There is also seasonality in electricity consumption, which increases significantly in the cold season when electric heating is turned on. At dachas, consumption increases on weekends, the power of the networks is insufficient, and the voltage is less than necessary.
Who is to blame - the supplier or the consumer?
First of all, we find out who is responsible for the insufficient voltage. IN apartment building This is very easy to do, just ask your neighbors if they have a similar problem. If not, we look for the reason ourselves. In the private sector, we interview people whose houses are connected to the same phase. We look at the power line, remember which wires lead to own home, we are looking for houses powered by the same wires. You can also turn off all devices and measure the voltage. If it is normal, but drops after turning on several appliances, the reason lies in the house.
If the voltage drops in the house, then the reasons are as follows:
- 1. Insufficient input. A thin wire causes low voltage in the network, especially at maximum load
- 2. The contact at the input is burnt, additional resistance is formed, causing the voltage to drop. Losses can be significant.
- 3. Poor quality of branch wire from the line to the house. Poor contact on the twist increases the resistance, and everything happens similar to the previous case.
The voltage drop is accompanied by the release of heat. If the wiring cross-section is insufficient, this is not a problem, since the heat is evenly distributed along the entire length of the wiring. If the contacts are bad, the consequences can be very unpleasant. This place will heat up intensely to the point that the wiring will burn out, but a fire is also possible. If the voltage problems are related to the power company, then it seems as if solving this issue is easy, you just need to write a statement.
In reality, everything is more complicated; suppliers often ignore low voltage in the network, because it is associated with expensive work on power lines. It is possible that due to increased electricity consumption, the substation transformer is overloaded and needs to be replaced. It happens that power transmission line wires were laid a very long time ago, and now their cross-section is unable to satisfy the increased needs, it is necessary to carry out reconstruction. Another common reason is uneven load distribution across the transformer phases.
Conductors with a small cross-section are more common in gardening partnerships, but the same problem exists in the private sector of the city. The fact is that several decades ago, cheap steel-aluminum wire was used on power lines. He then satisfied the existing needs, but now they have increased significantly. The wire cross-section of 16 mm 2 is no longer enough. A characteristic feature low power of the transformer or insufficient cross-section of conductors is a reduced voltage during the day and its increase to normal at night.
It is almost impossible to prove that the transformer has insufficient power or the load is incorrectly distributed among the phases. Network congestion may occur for a while and then disappear. The phenomenon of voltage sag is variable, and consumers often have to solve the problem themselves. You need to write a complaint to the energy company, but you also have to do something yourself.
Voltage sag is a particular solution to the problem
If you are convinced that tension home network falls due to problems with the branch line from the power line to the house, then we take some action. We inspect the connection of the branch with the main power line. Very often it is made by conventional twisting, which leads to a steady increase in resistance. Only good cooling under open air protects wires from burning out. The connection is made using certified clamps.
Sometimes connected by twisting aluminum wires lines and copper inputs into the house. The junction of two dissimilar metals gets very hot, we replace the twist with clamps or a terminal block.
If the connection is made with clamps, pay attention to their body. A melted surface indicates poor contact. If we turn on the maximum load, then the appearance of smoke and sparking inside indicates that a voltage drop is occurring in the clamp; we replace it with a new one. A similar problem occurs on the upper terminals of the input machine. We replace a device with burnt contacts, a melted body, and tighten the contacts securely.
If the energy company ignores the residents’ requests, does not change the transformer to a more powerful one, or the main wires to a larger cross-section, you will have to find a way out on your own. Electricity suppliers, eliminating problems with increasing voltage, are faced with the need for millions of capital investments, and are reluctant to take such a step. One of the ways to privately solve the problem is to supply three phases to the house, which requires permission from the energy sales office. If it is received, we place a phase switch at the input and, if necessary, use the least loaded one.
There are other ways to solve the problem privately:
- 1. We install a voltage stabilizer at our input, but if there is a significant drop to 160 V, the device may be ineffective. A good stabilizer of suitable power is expensive. If a dozen similar devices are connected along the street, the network will drop to its limit and the stabilizer will be useless.
- 2. Install the step-up transformer, selecting the appropriate parameters. But the fact is that the drawdown is unstable and, when the voltage returns to normal, the transformer raises it to such a value that all connected devices will burn out. To avoid this, we install a relay that will break the circuit when the limit threshold is reached.
- 3. We install additional grounding of the neutral wire at the input. Thus, the resistance of the zero and the entire wiring as a whole is reduced. But the method is dangerous; there is a possibility that during repairs the phase and neutral wire, there will be a short circuit. Even worse, when there is a zero break on the power line, the current will flow through the grounding, very serious consequences are possible.
- 4. For a private home, with sufficient funds, we purchase a voltage converter with an energy storage device. This is the most radical way raise the voltage, get rid of problems, but such equipment is very expensive: from 3 to 20 thousand dollars.
Such a device provides ideal current parameters in the network, supplying consumers with electricity when it is turned off. It operates on the same principle as an uninterruptible power supply for a computer, but has a much higher power from 3 to 10 kW. The device has electronic communication with diesel generator, which automatically starts when there is a power outage. But the startup occurs after some time, first the device’s batteries are used.