desain tripping circuit main protection relays

[AAKEM]

What are the advantages and disadvantage using 2 tripping circuits from main protection relays (distance relays, differential relays, etc)to circuit breaker with 2 tripping coils in substation with only 1 DC supply system?
In my company, I find design of tripping circuit main protection relay only connected to 1 tripping coil and another tripping coil is used for back up protection and manual open circuit breaker.

 

[davidbeach]

A system to trip coil 1, B system to trip coil 2. Ok, today that means that A and B come from different DC circuit breakers in the same panel, but in the future they'll come from different breakers in different panels on different batteries. Take every step that presents itself, don't wait to start until the whole path is available. Three baby steps is far better than doing nothing while awaiting the opportunity to do it all in one fell swoop.

 

[AAKEM]

In Extra High Voltage substation (AIS and GIS) and High Voltage substation (GIS), we already implemented 2 DC supply systems for main A and main B protection relays. The problem is we have 150 High voltage S/S with each bay supplied only by 1 DC supply system. Need extra high cost and much effort to modify the existing tripping circuits to be ideal. If we modify using 2 tripping circuit from main protection with only 1 DC supply system, are we get other risks from this design?

 

[Mbrooke]

I'd go the 2 trip route regardless of supply. The whole point is if one trip coils fails or trip circuit shorts (make sure each is individually fuses) that the other will back it up and still trip the breaker. the higher up you go the more important it is to avoid breaker failure.

 

[bacon4life]

+ Trip coil failures occur much more often than battery failures, so the trip coil redundancy is useful even with just one battery.
-Multiple tripping paths makes testing more complicated. The circuits should be designed so that every trip path can be independently tested.

 

[AAKEM]

thanks for comments...
What are concerns if we design trip circuit from main protection to 2 tripping coils?
1. MCB DC supply must enough to supply 6 tripping coil. Using 2 MCBs DC supply to separate supply to TC 1 and TC2 is better.
2. ?????