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Out-of-step tripping for generation

Out-of-step tripping for generation

Out-of-step tripping for generation

(OP)
At what size unit does out-of-step tripping become practical?
We have a number of older units that never had the 78 protection, and it is looking like we need to consider adding it.

RE: Out-of-step tripping for generation

Hi cranky108.
In this case size of unit is not important.
Its depend on grid, connections, etc.
We had a 40MVA units with this protection and 150MVA witout it.

Best Regards.
Slava

RE: Out-of-step tripping for generation

Look at your loss of field protection characteristic. Sometimes it provides the equivalent protection since a swing on out-of-step can look like a loss of excitation event to an impedance relay connected to the generator terminals.  

It depends on how fast the swing is and what the time delay is on your 40 relay.  Check if the swing locus goes through the 40 relay operating zone.   

RE: Out-of-step tripping for generation

Pole slip protection - which, when applied to a generator, is the same function as far as I understand - is common on British machines over 50MW or so.

With the advent of multi-function relays it is becoming common to see it on smaller machines embedded in the distribution system too, although how well the protection function is set is perhaps a different question. As Slava indicates you need a fair amount of information on the system and it is normally easier to get that information from the transmission system operator than a distribution company, plus the TSO will likely be able to give more definitive answers because of the smaller number of network permutations compared with the distribution system.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Out-of-step tripping for generation

On a smaller machine the main breaker will trip.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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