Ultrafast tripping times
Ultrafast tripping times
(OP)
Hello,
I am wondering if anyone has run across any whitepapers or IEEE articles relating to ultrafast tripping times. I am trying to find, given our current technology, what the fastest time a relay can initiate a correct trip signal is.
As of right now I cannot find anything where the required sample size is less than one cycle. Current relays would sample for a minimum of one full cycle (0.01667s), convert the analog signal to digital, put it through a peak detection filter, and most likely a cosine filter to get rid of the harmonics and DC components. Does anyone know if it is possible to render a useful signal (where the relay can send a trip signal with high confidence that the sampled signal is in fact a fault) with a sample size less than this (perhaps 1/2 cycle)?
Thanks
I am wondering if anyone has run across any whitepapers or IEEE articles relating to ultrafast tripping times. I am trying to find, given our current technology, what the fastest time a relay can initiate a correct trip signal is.
As of right now I cannot find anything where the required sample size is less than one cycle. Current relays would sample for a minimum of one full cycle (0.01667s), convert the analog signal to digital, put it through a peak detection filter, and most likely a cosine filter to get rid of the harmonics and DC components. Does anyone know if it is possible to render a useful signal (where the relay can send a trip signal with high confidence that the sampled signal is in fact a fault) with a sample size less than this (perhaps 1/2 cycle)?
Thanks






RE: Ultrafast tripping times
RE: Ultrafast tripping times
RE: Ultrafast tripping times
RE: Ultrafast tripping times
1. I have only seen relays which initiate a tripping signal based on the filtered rms value (ie. the signal sent by the CT and filtered for DC and harmonic components). Is this for the most part correct?
a. If so, does anyone know the typical time interval used to calculate the rms current (ie. the signal is integrated over 1/4 cycle continuously)?
davidbeach, by what you have said above, it is logical to conclude that the time to register an instantaneous trip signal is a function of the multiple of prospective fault current (ie. pickup @ 1/2 of available) and not the multiple above continuous load current. Would this be correct?
2. Has anyone seen a di/dt method used in conjunction with rms current magnitude for locating fault events?
Thank you
RE: Ultrafast tripping times
Using common relay test set, from the time if current initiation to the output trip contact closure is 10 mses for SEL-321 / 421 or ABA REL series relays.
The event record has a sple rate of only 4 times per cycle, but I do not kniw what the on-biard A/D clock cycle is. The output trip relay,ga a 4 mse response time in the spec ? And tha's from memory.
our line breakers are 1.5 or 2 cycle breakers.
RE: Ultrafast tripping times
1-It is 1 cycle. In numerical relays;- RMS value at reference point tc is calculated by measuring window situated on the left of tc and its length corresponds to ONE period of the nominal frequency (60Hz=> 16.66ms)
RE: Ultrafast tripping times
RE: Ultrafast tripping times
RE: Ultrafast tripping times
RE: Ultrafast tripping times
If your system has inherent Z that gives a dependable worst case max current rise that is probably >10x short circuit rise time, this 'rate of rise' method should be useful.
www.KilroyWasHere<dot>com
RE: Ultrafast tripping times
rate of current rise in drives
got a couple possible hits?
http://www.galeon.com/tapioca/shortcircuit.pdf
http://www.evdl.org/docs/igbt_shortoff.pdf
not sure if it helps give ideas for you but may be interesting reading and a direction to turn?
www.KilroyWasHere<dot>com