Content:
- Valid values
- The causes of the phenomenon
- Dangers and consequences of skewing
- Protective measures
Valid values
There are norms and permissible values that are indicated in the corresponding GOSTs and PUEs regarding the quality of electricity. According to these standards, the ratio between the currents of the least loaded conductors and the most loaded ones in switchboards should not exceed 30%, and in ASU panels - 15%. According to GOST p. 5.5 the permissible phase imbalance in the negative sequence should be 2%, and in the zero sequence - 4%.
The causes of the phenomenon
There are several reasons for this action to occur. The main reason when skewing occurs is considered to be incorrect and uneven load distribution in the internal electrical network, when one phase receives an overload. The second and third, as a result, will work with significant underload.
In a network where there is only one phase, the load can also increase. This occurs when a large number of household appliances are turned on. Then the skew becomes noticeable, as the power drops and the devices stop working.
Due to the fact that household appliances start to work incorrectly, this can lead to their breakdown. As a rule, motors are considered the weak point in most devices. Therefore, it is they who fail. You can check where there is a bias using a special device (clamp meter), which will help determine which circuit exists overload.
The three-phase network has a solidly grounded neutral. It is she who evens out the uneven distribution of voltage in the electrical circuit. But with break zero, the role of neutral is assumed by one phase. Then the voltage on it can reach up to 380 volts, and on the rest it will be 127 volts and below.
Dangers and consequences of skewing
What is the danger of phase imbalance in the mains? Conventionally negative moments can be divided into three groups:
- Harm to electrical receivers (devices, equipment): their damage, reduced service life.
- Harm to sources of electricity: mechanical damage, increased consumption of electricity, reduced service life of the source.
- Consequences for consumers: increased electricity costs, the need to repair electrical equipment, possible injury.
Due to the fact that electricity is distributed unevenly along the conductors, electricity consumption in the power grid increases significantly. A three-phase network, which has formed an asymmetry, can reduce the life of electrical appliances and household appliances.
If this is an autonomous power plant, then the consumption of oil and fuel in such a situation increases significantly, and the generator may break down. In the case when one phase receives more voltage than the other two, electrical safety is violated. And this can lead to various electrical injuries, as well as to the fire of electrical household appliances and the wiring itself.
As you can see, the consequences of this phenomenon are significant and their solution and elimination can lead to large material costs. In order to avoid such an unpleasant situation, certain measures should be taken in advance.
Protective measures
In order for the three-phase network to work symmetrically and the voltage on each circuit to be normal, special devices should be used. Most often they perform installation of a voltage stabilizer. In everyday life, single-phase devices are used that are able to protect electrical appliances and equipment. And in industry, a three-phase stabilizer is used, which consists of three single-phase devices. But such protective devices cannot completely eliminate the imbalance, since only one phase is assigned to them and they equalize the voltage only in it.
Therefore, a three-phase network cannot completely protect against such a phenomenon with stabilizers, as well as eliminate their cause and consequences. There are times when these devices themselves are the cause of uneven and inappropriate energy distribution. This problem can be corrected thanks to an alternative technology that is able to equalize the voltage across all phases of the circuit.
A three-phase network is protected against unbalance in the following ways:
- correct power supply design, taking into account possible loads;
- the use of devices that are able to automatically balance the load;
- a change in the existing circuit of the energy consumption scheme (in the case when each phase was not previously calculated for overload);
- in the most critical situations, it is necessary to change the power of consumers.
- installation of a special phase control relay and a voltage that cuts off the power if it detects unbalance (pictured below).
In this way, the skew in the three-phase power network can be eliminated and your electrical devices can be protected from damage. Finally, we recommend watching a useful video on the topic:
So we examined the danger of phase imbalance in a three-phase network and how to protect yourself from this phenomenon at home. We hope the information provided was useful and interesting for you!
It will be helpful to read:
- How to assemble a three-phase electrical panel
- How to use a clamp meter
- Low voltage in the network - what to do
