Protection Coordination of Ring Circuits
Protection Coordination of Ring Circuits
(OP)
How is it really done? It seems you have bi-directional relays at the source bussbar and uni-directional relays at all the other busses looking towards the source. You then have two sets of uni-directional relays looking in opposite directions. When setting do you consider the situation as two separate radial circuits?






RE: Protection Coordination of Ring Circuits
RE: Protection Coordination of Ring Circuits
As long as every source proective device is coordinated with every load device (each load device must trip before each source device it can be energized from), you will be OK.
If multiple sources are present, they should have added directional relays which are set significantly lower than the overcurrent relays so that, in the case of a fault upstream on one source line, the other sources feeding that fault will trip quickly.
RE: Protection Coordination of Ring Circuits
RE: Protection Coordination of Ring Circuits
RE: Protection Coordination of Ring Circuits
You can use differential or directional protection for this kind of situations, like suggested by previous posters. From a coordination or protective viewpoint differential protection might be best option, but depending on the application, it might be much more expensive than directional protection.
From your initial question it seems as if you are more interested in directional protection. Most protective handbooks cover it, and you'll also find a lot of information regarding it on the web. One excellent resource:
Download: NPAG link
Chapter 9 - overcurrent protection for phase and earth faults.
9.14 - 9.15 deals with directional protection.
In short DanDel and stevenal are correct - read through the information in the link - if you have any specific question I will try my best to answer it. (or anyone else!)
Regards
Ralph
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RE: Protection Coordination of Ring Circuits
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RE: Protection Coordination of Ring Circuits
RE: Protection Coordination of Ring Circuits