High Impedance Bus Zone- Surge Arrester in zone
High Impedance Bus Zone- Surge Arrester in zone
(OP)
I'm involved in a project which involves the replacement of an 11kV switchboard on an industrial 11kV underground network. The new switchboard has surge arresters which are within the zone of the high impedance busbar protection scheme. The client has asked whether the bus zone protection operation should be delayed by a few milliseconds to avoid maloperation if the surge arrester operates. The client has seen a SEL paper on the subject of bus bar protection which suggests that this should be done.
I've never come across this practice before. My view was always that surge arresters conduct for transients in the MHz range, and I can't see how they would be transformed by a CT as an operate current or picked up by a high impedance relay.
I'd be interested in your views, and whether the delaying of bus bar protection operation for this reason is practiced in your area.
https://www.google.com.au/url?sa=t&rct=j&q...
Regards
Marmite
I've never come across this practice before. My view was always that surge arresters conduct for transients in the MHz range, and I can't see how they would be transformed by a CT as an operate current or picked up by a high impedance relay.
I'd be interested in your views, and whether the delaying of bus bar protection operation for this reason is practiced in your area.
https://www.google.com.au/url?sa=t&rct=j&q...
Regards
Marmite






RE: High Impedance Bus Zone- Surge Arrester in zone
I find it interesting that we take instrument transformers rated for 50 or 60 Hz and attach them to power quality meters that capture high speed transients and high numbered harmonics. Apparently these transformers can supply the waveform.
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone
I'm just intrigued as to whether this is a real problem with modern arresters. Maybe for switching transients with a longer duration than lightning?
Regards
Marmite
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone
If there is any consolation price, you are no along in this issue. There is a general believe in the industry that relay detection/trip and surge arrester operation are not related since they work in different time range. It is well known that surge arresters transient operate at high frequency in in the microsecond range vs. millisecond for relay detection.
With advance on fast fault detection logic of modern digital relays, there is a growing concerns that nuisance tripping of bus differential relaying is susceptible to misoperation due to mismatch caused probably by discharging through the bus lightning arrester(s), reflection, and refraction and/or skewed sampling of the bus differential relay.
We should take this opportunity to encourage the researchers and relay manufacturers to implement better fault detection algorism to eliminate this type of nuisance tripping instead of adding delays tripping time.
RE: High Impedance Bus Zone- Surge Arrester in zone
The parameters measured by the power quality meters are still related with power frequency. The CT frequency bandwidth should be accommodating these frequencies upto about 50*f.
But the surge arrestor conduction is for the for the high frequency. for example if the surge voltage rise time is 50µs, the frequency is 1 [s] / (50 x 10-6) [s]
= 20,000 Hz or 20 kHz
Moreover, the surge arrestor is expected to conduct for a cycle or two only. This conduction is only to discharge the trapped energy which is measured in Joules.
Hence in my opinion it is not correct to draw parallels between the harmonic currents and the surge current.
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone
RE: High Impedance Bus Zone- Surge Arrester in zone