Distance Operation Due to inrush
Distance Operation Due to inrush
(OP)
Hi,
I have distance protection relay used for 33KV radial line around 80 KM long with more than 150 Distribution transformers.
this relay have been operating by Zone-1 many times at energization due to high inrush current 800 A while the maximum feeder load is 200 A.
to avoide this situation we usually open at the middle of the line and energize then we close.
my question: I understand the effect of inrush current in overcurrent operation, can any one explain its effect on distance relay?
thanx
I have distance protection relay used for 33KV radial line around 80 KM long with more than 150 Distribution transformers.
this relay have been operating by Zone-1 many times at energization due to high inrush current 800 A while the maximum feeder load is 200 A.
to avoide this situation we usually open at the middle of the line and energize then we close.
my question: I understand the effect of inrush current in overcurrent operation, can any one explain its effect on distance relay?
thanx






RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
Or if you know the inrush dosen't exceed 800A you can set the fault detector above that level.
RE: Distance Operation Due to inrush
Many times after OHL maintenance, it happens that the earth is not removed and the OHL is switched on. This is called 'Switchon to fault' condition.
The protection would not be effective for this as it is delayed.
Instead, to make the relay stable against transformer inrush currents, it could be good idea to inhibit the protection operation on sensing 2nd harmonic component in the OHL current.
This should be easy to configure in case of numerical relays.
RE: Distance Operation Due to inrush
there is a feature in 'Transformer Diff.' ABB Typre RET541
Called Deblocking ! ( removing blocking of 2nd harmonic in
case of 'Switching on to fault'.but if there is no exist
of fault will continue blocking 2nd harmonic after energization.I don't know if new numerical relays solved
that in OHL or not with distance relays but that should be
treated anyway.
RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
1. time delay can be added to zone 1 . But how much? Inrush period & magnitude is un predectable.
2. Second harmonic detection in series with tripping signal. i think this can be implemented in configuration file.
3. stick with overcurrent : Good solusion :)
thanks everyone
SMB
RE: Distance Operation Due to inrush
A misapplication of distance protection obviously. See davidbeach comment above.
Zone 1 has to be instantaneous in principle, unless you want to burn down something.
A protection study is indicated/recommended.
Must be far out in the bush someplace.
regards, rasevskii
RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
RE: Distance Operation Due to inrush
The issue of slow tripping for cases of closing into a fault is one I did not think about. That is something to consider. One way to partially address it for the first ## cycles after closing a breaker, enable an impedance element with high settings that will not trip for inrush. After that time delay, enable a more sensitive impedance element.
RE: Distance Operation Due to inrush
Some relays have a 50 element that is used to supervise the distance element such that it is set higher than the maximum line in-rush but below the minimum line-line fault. This 50 element is used to arm and disarm the distance element (like in the case of SEL 311B).
If your relay does not have one, then you may (IMHO) provide a 50 relay to supervise the trip.