Hi All,
I have a question about fault current behaviour in a ZNyn1 (22kV/0.440kV) transformer, which is being used as an earthing and auxiliary transformer.
For a line-to-ground (LG) fault on the LV (yn) side, my calculations show a very low fault current, which seems to align with standard...
Hi All,
There has been an increase in the need for Special Protection schemes as a result of the ever-changing power system. Would anyone be able to share any guidelines on how to scope, design, commission and maintain these schemes. I would appreciate any direction you can provide. Thanks
sushilksk; but i doubt any SOTF scheme put into place would beat line differential in the first place, as SOTF schemes have 1-2 cycle pickup delay.
thermionic1: yeah only if the line is energised with faulty comms and there is a dead short circuit at the yard yielding no polarising voltage for...
Hello All,
Just want to get your view on implementation of SOTF scheme on line diff relays?
I tend to think that being a current based protection no special SOTF(overcurrent threshold based, etc.) needs to be implemented on a line diff. relay. Appreciate your views/experience on this?
VT may not be the solution as it is difficult to descriminate the fault relying on a bus VT.
NPS is a good way to detect low LL fault. What about low LLL fault?
Using a recloser is an excellent option; however, multiple reclosers are needed to provide remote backup during hardware failure.
Hi Davidbeach.
Even though reclosers are installed there wont be any overreaching protection or upstream backup unless you install few reclosers.
Also what are your views on not clearing or catering for end of line LL fault?
Hi,
What is your experience with clearing LL faults at the end of rural distribution feeder with low fault current. The problem is with fault level so low, there is no discrimination against load current. Also, what are the concerns with such a low LL fault going undetected? If this fault...
Hi RRaghunath, how does the metering CT behave during an active fault and when breaker fails? The CT will go into deep saturation and not yield the 10 or 20% I required for check current. Also remember CBF delay time may complicate things further.
PS: the breaker will continue to feed the active...
Thanks All, Just a question, using BCU for current checked CBF can lead to a problem, as BCUs are generally feed from measuring CTs which may saturate during the fault condition and not yield replica current required for Current check? what are your thoughts on this?
For transmission lines what are the benefits of having AR functionality reside in Bay Control Unit?
I am used to relays(X & Y) doing the AR; however, of late seen some schemes where BCU does this based on the AR initiate/block signal from relay.
25MVA YNyn0d1, source side ungrounded transformer tripped on Instantaneous EF during energisation. The waveform signature revelled inrush, but the question is how did neutral current appear on the supply side when the star point is floating?
Appreciate any thoughts
Hi Davidbeach,
Will the ground fault contribution from the generator increase because of additional grounding path and what will be the impact of circulating current and chances of mis/no operation of protection device?
What will be the impact of having multiple grounding source connected to Substation bus during normal/fault condition. the situation is:
a. 6.6kV generator connected to the bus with its neutral grounded
and
b. 6.6kV LV side of 3 winding transformer connected to the same bus. The LV neutral...
