Why Snubber Circuits are Required for Transformer Protection?

why snubber circuits are required for transformer protection cover

Switching Transients or Transient Recovery Voltages may occur in certain situations and events occurring frequently in normal operations of a MV or HV industrial or commercial Power System. They may not be fatal in their first occurrence but prolonged exposure to transients will reduce lifespan of power system equipment. They may also disturb the stability of the power system putting the entire installation at a risk of shutdown or failure of certain equipment.

A snubber circuit is a proven way of reducing these transients and ensuring the protection of individual equipment and the wider system. Therefore, snubbers find their applications in many areas in a power system, in most cases becoming an indispensable component of it.

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What are Snubber Circuits?

Snubber circuits consist of a combination of:

1. A capacitor

2. Resistor

3. Fuse

4. And a surge arrestor

components of a snubber circuit
components of a snubber circuit

What Does a Snubber Circuit Do?​

Broadly speaking, when you connect a snubber to a device of choice, it can absorb voltage spikes and normalize any abnormality or disturbance in the voltage waveform. They are most effective in mitigating fast-rising transient voltages and in attenuating reflections and resonances before they have a chance to build up. They are also employed to reduce the frequency of an electrical disturbance.

There are several reasons due to which transient recovery voltages (TRV) and power frequency over-voltages (PFOV) may arise in a power system.

Application of Snubber circuits

One may segregate the applications of snubbers into two broad categories:

  • Applications in Power electronics
  • Applications for the protection in power system

Snubber Circuits for the Protection of Power Transformers

Transformers being an integral part of the power system are susceptible to such transient voltages and disturbances. In a case where these transient recovery voltages and disturbances come close to the basic insulation level (BIL) of the transformer, if for a short time and within the permissible level, they will not be fatal at their first occurrence but repeated occurrences will damage the insulation and windings overtime and eventually cause transformer failure leading to damage and loss of costly equipment.

In some situations, voltage transients may be significantly higher than the BIL of the transformer where their occurrence will immediately disturb the stability of the system causing more circuit breakers to trip along the system and escalating the fault.

Engineers can be employed to reliably perform transient stability studies and switching transient evaluations for power trans
Engineers can be employed to reliably perform transient stability studies and switching transient evaluations for power trans

Snubbers for Protection of other Power System Equipment

With Circuit breakers, transmission lines, generators, large motors and reactors, they are used in parallel with surge arrestors to keep voltage transients within a safe level.

Read here to find out why it is important to perform transient recovery voltage studies to correctly predict the transient voltage levels.

Let us know if you have any queries regarding this topic and do provide us with your feedback in the comments.

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