What is phase-to-phase short circuit: its causes, methods of protection and consequences

For an interphase short circuit, there must be at least 2 "phases" - it is logical. Therefore, this phenomenon is often found in manufacturing or in the private sector, where 380 V is the standard line voltage. Apartment buildings with 2 or more phase conductors can be seen only in the control room on the staircase or in the common panel in the basement.

Causes of interfacial short circuit

Now we will talk exclusively about the phase-to-phase short circuit, forgetting what the potential difference between the phase and neutral wires is.

Because of what a short circuit may occur between the two "phases":

• Insulation breakdown of phase conductorslocated close one to one. A frequent occurrence in switch rooms, where several "phases" take place.
• Interturn short circuit in electric motors and transformerswhere electric current from two different "phases" can flow in two adjacent windings.
• In switching equipment. For example, in circuit breakers. Rarely, but still possible, mainly due to damage to the case of the machine under the influence of high temperature.

The main reason for this type of short circuit is still damage to the insulation of conductors due to old age, mechanical stress (the car has run over) or exceeding the permissible load. But also a short circuit can occur when a foreign metal object enters the cabinet, therefore, 380 V lines require appropriate protection.

How to avoid?

The simplest, and therefore the ideal solution, is the installation of a three-phase circuit breaker, which is not only will protect the line in case of short circuit, but also preserve the integrity of the conductors during their prolonged heating as a result of an increase load.

Advice! Do not install 3 single-phase circuit breakers, it is better to install one three-phase, calculated and designed specifically for 380 V networks.

If this is a switchgear at a transformer substation, then machines are rarely installed there, most often these are fusible links in a ceramic case filled with sand. Their difference from usual in a special design and rated conductivity of high currents.

The need for periodic line maintenance

1. The best way to avoid a malfunction is to prevent it. So that a short circuit does not happen, you should periodically check the insulation resistance of the wires. It is problematic to do this on your own - it is better to call a good master.
2. It is impossible to check the circuit breaker in the same way, the only thing that can be done is to forcibly close 2 phases. But such an operation is quite dangerous, therefore, periodic cleaning of the contacts of the switching device will be quite sufficient.
3. It also does not interfere with monitoring the load in the house. Excessive overheating of the conductor leads to damage to its insulation. Of course, a special bimetallic plate is installed in the machine, which disconnects the line in the event of a gradual heating, but the cases are different and you should not rely too much on protective devices - an extra check is never will interfere.

P.S. I recommend that you read my video, where I cover the topic of phase-to-phase circuit in even more detail.