Coordination of Breakers on synchronization Bus and Emergency Bus of the building

[mayank]

Is coordination possible for Breakers on the synchronization bus and Emergency Bus of the building. The DG system comprises of two parallel feeding Generators. A fault in any Substation kills the emergency supply by tripping both DG simultaneously. The DG incomer breakers are of lower capacity than the outgoing breakers of the DG bus. The breakers at the emergency bus are of same capacity as the outgoing breakers of the DG Bus.

Is there a way to coordiante breakers so that a fault downstream will selectively trip the outgoing breakers and not the both DG.

 

[templdl]

Have you considered a Pilot wire relay scheme?
This is what I found:
A pilot wire relay protection system for detecting and responding to phase-to-phase, three-phase, phase-to-phase to ground, and ground current faults including relatively low level ground current faults occurring within an electrical power network is disclosed. The pilot wire relay protection system includes current transformers coupled to transmission lines of the electrical power network for developing coupled currents representative of the transmission-line currents. The current transformers are positioned at the ends of a section of the electrical power network for which protection is desired. The coupled currents from the current transformers are inputted to pilot relays having an analog device for producing a composite signal indicative of the condition of the protected section of the network. The pilot wire relay also includes an electronic device to detect if preset fault limits have been exceeded. Upon detecting a condition indicative of a fault within the protected section, the pilot relay transmits an electrical signal to a power circuit breaker which in turn disconnects the protected section of the electrical power network from the remainder of the network.

GE has SPD and SPA relays as illustrated in the pdf:http://store.gedigitalenergy.com/FAQ/Documents/SPA/GET-6462A.pdf

I know just enough to be dangerous in this stuff and am no way even close to being knowledgeable. But I've sold doubled ended switch gear that has either the pilot wire of differential relays schemes specified with them. In one instance my direct customer wanted a pilot wire relay scheme and I strongly suspected that a differential relay scheme was probably more appropriate. After supplying what my customer specifies the end user had them retrofit the swgr to differential relaying. As I recall the pilot wire relay may be what you want.

 

[rcwilson]

Look at zone interlocking the breakers. Most switchgear breakers now have this option.

With zone interlocking, when a down stream breaker detects a fault it sends a signal to the upstream breaker to hold off tripping for a few tenths of a second. The downstream breaker is essentially saying, "hang on, I've go this one covered." This only works if the breakers can withstand the fault current for the delay time needed. If the fault is between the breakers, the upstream breaker does not receive an ihibit signal and trips quickly.

Full coordination may not be possible depending on the breaker types, fault levels, etc.

Have an engineer look at the fault study and coordination curves.

 

[templdl]

Look at zone interlocking the breakers. Most switchgear breakers now have this option.

With zone interlocking, when a down stream breaker detects a fault it sends a signal to the upstream breaker to hold off tripping for a few tenths of a second. The downstream breaker is essentially saying, "hang on, I've go this one covered." This only works if the breakers can withstand the fault current for the delay time needed. If the fault is between the breakers, the upstream breaker does not receive an ihibit signal and trips quickly.

Full coordination may not be possible depending on the breaker types, fault levels, etc.

Have an engineer look at the fault study and coordination curves.

That's a good idea also. But, have you ever noticed that when the OP does not include anything about the description of the system in question we are all end up shooting at shadows by guessing what the actual application is.
If he were to have attached a one line we could provide some more specific suggestions for his application. Instead, I'm thinking about a large double ended MV switchboard and then there are insulated case power breakers, air circuit breakers, in addition to molded case breakers. We don't have the slightest idea as to what the voltage is nor the KW or ampere ratings.
And the beat goes on.....