Switch on the fault scheme in distance relay?

Replies

• 

  Ramani Aswath

  The question is too open.
  There are situations where a fault can cause major damage to circuits or equipment. In such cases generally a crow bar protection circuit is used.
  I was myself involved in developing a microwbar spark detection and protection circuit for an aerospace Electro Chemical Milling Machine. This machine was designed for running at 10000 amps (40V DC)load. The problem was that if there was a small spark of even a few amps, a very expensive tool would be damaged. It was necessary to detect a very small current spark riding on a very large load current and short circuit the supply voltage within micro secs and then use a cascaded thyristor switch off and contactor opening to protect the mains supply.
  The crucial issue was the shorting of the load side within micro secs to minimise tool damage. Hence the name microwbar protection.
  
  Here are a couple of links on crow bar protection:
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  Crowbar %28Circuit%29
  
  (As an interesting aside, the name crow bar protection apparently came from linemen working on HV lines throwing an iron crow bar across live and neutral to protect other workers from getting accidentally electrocuted.)
• 

  kashmirihasan

  oky but how it is used as a function of distance relay?
• 

  Ramani Aswath

  I am not knowledgeable in this area. What I described may have nothing to do with what you want.
  May be this paper from General Electric may help.
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• 

  kashmirihasan

  yes. But i need a little bit elaboration on this topik