High Resistance Interruption

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High Resistance Interruption[/caption]

High Resistance Interruption is a topic of switchgear protection. In this method are resistance is made to increase with time so that the current becomes insufficient to maintain the arc.

The rate at which the resistance is increased or the current is decreased is not abnormal so as to cause harmful induced voltages in the system.

Because of the resistive nature of the arc discharge, most of the energy in the system will be received by the circuit breaker.

The main drawback of this interruption is that the energy dissipation is high.

Hence it can be used only in low and medium circuit breakers and in d.c. circuit breakers.

Arc resistance can be increased by:

(a) Lengthening the arc:

Arc resistance is directly proportional to the length of are so as to increase resistance, the separation between the contacts is increased.

(b) Cooling the arc:

Cooling helps in deionization of medium thus increasing arc resistance.

(c) Splitting the arc:

The resistance can be increased by splitting the is into a number of smaller arcs in series. Each arc experiences the effect of lengthening and cooling. Arc may be split by introducing some conducting plates between the contacts.

(d) Reducing cross-section of the arc:

When the area of the arc is reduced, the voltage required to maintain the arc to be increased i.e. resistance is increased. Allowing the arc to pass through a narrow opening can reduce the cross-section area.

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