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High Resistance Interruption

High Resistance Interruption

High Resistance Interruption is a topic of switchgear protection. In this method, resistance increases 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 the area so as to increase resistance, the separation between the contacts is increased.


(b) Cooling the arc:

Cooling helps in the deionization of the 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 divided by introducing some conducting plates between the contacts.


(d) Reducing the cross-section of the arc:

When the arc area is reduced, the voltage required to maintain the arc is 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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