What voltage deviation in the network is considered the maximum permissible

Standards according to GOST

The maximum deviation (positive and negative) should not exceed the 10% mark from the nominal value. Total we receive such values:

• for a 230 V network – from 207 to 253 V;
• For a 400 V network – from 360 to 440 V.

As for the permissible voltage deviation from consumers, GOST stipulates that this value at the points of common connection is established directly by the network organization, which in turn must meet the criteria specified in these standards.

In addition, I would like to note that during normal operation of the network, the permissible voltage deviation at the terminals of electric motors is in the range from -5 to + 10%, and for other devices no more than 5%. At the same time, after an emergency, it is allowed to reduce the load by no more than 5%.

By the way, I would also like to note that according to standards, the deviation on the power supply in electrical networks with a power of 0.4 kV should not exceed the 5% mark, in fact, as well as on the consumers themselves. Total, 5% at source + 5% from consumers, we have 10% of the maximum allowed.

It is important to know the causes of voltage deviation. So the main reason is the seasonal or daily change in the electrical load of the consumers themselves. For example, in winter, everything suddenly switches to heaters, as a result of which the power supply parameters decrease significantly. About, what to do if the voltage is low, we told in the corresponding article!

Negative effect of parameter deviation

In order for you to understand the full danger of voltage deviation in the network, we offer the following facts for reading:

1. When the value drops below the normal range, the service life of electrical equipment is greatly reduced and at the same time, the possibility of an accident occurring. In addition, the duration of the production process itself increases in technological installations, which entails an increase in the cost of production.
2. In a home network, as we said before, voltage deviations reduce the life of light bulbs. With a 10% increase in voltage, the life of conventional lamps is reduced by 4 times.In contrast, energy-saving lamps begin to flash when the voltage decreases by 10%, which also negatively affects the duration of their operation. About the rest reasons for the flickering of fluorescent lamps you can find out from our article.
3. For electric motors, due to the decrease in voltage, the current consumed by the motor increases. This in turn reduces engine life. If the voltage is even insignificant, it may seem 1% higher than normal, the reactive power consumed by the electric motor can increase to 7%.

To summarize, I would like to note that there are several modern ways to solve the problem: reducing voltage losses in the electrical network, which we wrote about in the corresponding article, as well as load regulation on outgoing lines and substation buses.

So we checked the norms of voltage deviations in the network according to GOST. Now you know how low or high this parameter is in three-phase and single-phase AC networks!