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High Resistance Interruption

High Resistance Interruption


[caption id="attachment_1285" align="alignnone" width="300"]High Resistance Interruption 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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