SEL Mirrored Bits
SEL Mirrored Bits
(OP)
I am wondering if anyone has daisy-chained a bunch of relays together using mirrored bits to carry out zone blocking to reduce bus arc flash levels? Sending a bit from one relay to the next until it is sent up to the relay bus relay. I am wondering if it is faster while also providing the added benefit of letting you know if communications have failed.
About how long does it take for a mirrored bit to transfer from one relay to another?
About how fast are high speed and non-speed physical contacts?
About how long does it take for a mirrored bit to transfer from one relay to another?
About how fast are high speed and non-speed physical contacts?






RE: SEL Mirrored Bits
I personally avoid the whole issue and use a bus differential.
RE: SEL Mirrored Bits
RE: SEL Mirrored Bits
But to the point, fixing old gear is never easy. Our guys were all with some scheme like you are proposing, until we informad them that live gear testing required the moon suit anyway because they were taking the high speed system out of service to test each feeder, and they required an outage anyway to test the bus scheme.
This was versis the testing of each feeder in normal clothes, and taking an outage to test the bus differential.
The only way such a voteing scheme makes since is if you have guys in the gear on a regular bases, other than testing. Which in a substation is not typical.
RE: SEL Mirrored Bits
The hard-wired contacts are not as fast, but they will be still be much faster than waiting on the normal coordinated time overcurrent function.
SEL calls this "fast bus tripping" - they used to have some white papers on their website. We call it the poor man's bus differential relay.
RE: SEL Mirrored Bits