Emergency power supply requirement
Emergency power supply requirement
(OP)
I have a system where the emergency diesel generator (EDG) is located in the main substation which is about 200 mtrs away from the new electrical room. The 415V main emergency switchboard (SWBD) at the main substation has one normal incomer and the EDG incomer. During the normal operation the normal incomer will supply power and during the blackout or normal incomer fails the EDG will start and restore voltage to the 415V emergency switchboard (SWBD). This is an industry standard arrangement in the main substation.
One of my emergency load in the new electrical room is supplied from the main emergency Distribution Board (DB) through three (3) intermediate emergency Distribution Board (DBs).
Up to the final load point, there are total eleven (11) circuit breakers in series. So many no. of breakers in series would reduce the system security drastically. Additionally, the relay coordination will be extremely difficult from the source to the load point.
I want to know whether there is any standard which specifies the maximum no. of circuit breakers permitted in the emergency supply circuit. Any reference is available?
Any thought/input is most welcome.
One of my emergency load in the new electrical room is supplied from the main emergency Distribution Board (DB) through three (3) intermediate emergency Distribution Board (DBs).
Up to the final load point, there are total eleven (11) circuit breakers in series. So many no. of breakers in series would reduce the system security drastically. Additionally, the relay coordination will be extremely difficult from the source to the load point.
I want to know whether there is any standard which specifies the maximum no. of circuit breakers permitted in the emergency supply circuit. Any reference is available?
Any thought/input is most welcome.






RE: Emergency power supply requirement
RE: Emergency power supply requirement
Thanks for your quick input.
If you have to coordinate all these breakers, imagine how many layers of curves. How can you give sufficient grading between some many devices. Please remember that all these relay/fuses are in the same voltage level.
RE: Emergency power supply requirement
I can't remember off the top of my head at the moment, but I believe Eaton offered some type of solution for this.
RE: Emergency power supply requirement
What is of more concern is all the other loads and breakers. If a fault on any branch circuit is cleared by a main breaker rather than the branch circuit breaker, you may lose power on your Emergency Load of Interest.
For a critical circuit, the coordination of all other circuits fed from the same main is more important than the coordination of the Load of Interest.
That said, if this Emergency Load is very critical, have you considered a new feeder from the source?
Bill
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"Why not the best?"
Jimmy Carter
RE: Emergency power supply requirement
Thanks for the input.
In our set up, it is very difficult to initiate any re-configuration and introduce anything new, unless there is some documentary evidence which suggests that. So in order to make the case strong, I need some good reference of codes.
My location is in the offshore oil platform in the middle east region. So mostly we refer IEC standards. However, API and NFPA are also referred, if the requirement is stringent.
I am still searching in some IEEE books like, IEEE 493 (Gold, Reliable Power systems) and IEEE Std 446 (IEEE Orange Book) - emergency and standby power.
I would appreciate if anyone provides me some lead.