Power substation relay misoperations 2

[SidiropoulosM]

Any information on misoperation of power substation protection systems would be appreciated (categories and causes of misoperations, outage statistics etc.) Michael Sidiropoulos
Transmission Planning - Pacificorp

 

[grounds]

Induced voltage on control cables due to 60Hz fault current is one of the reasons for misoperation of some relays. I have seen a bus differntial relay misoperated due to a 15kV feeder cable failing insdie the substation. The fault current returned to the transformer from the corner of the substation via substation ground grid. The fault was outside the bus differential scheme and yet the differntial relay operated to take the entire substation out.

The investigation indicated that the fault current in the ground grid induced the voltage on the control cables. The induced voltage in differential mode caused the current to flow in the circuit.

 

[RRaghunath]

Grounds,

The bus differential protection might have lost stabilty during through fault (15kV cable failure). This is more likely, I feel, than the induced voltages during fault causing the relay maloperate.

The topic is interesting and I would appreciate any further feedbak on the subject.

 

[jbartos]

Suggestion: Visit

http://www.computer.org/proceedings/hicss/0001/00013/00013025.PDF

· Shunt Reactors and Capacitors - These
elements are used to provide system voltage support or
correction and are protected by a wide variety of
protective devices; differential, impedance and negative
sequence relays for reactors, fuses and overcurrent relays
for capacitors. They are susceptible to misoperation as
system parameters change drastically under unusual
system events. Their misoperation would exacerbate any
system problem by changing the voltage at the associated
system node.

 

[jstickley]

SEL has a large amount of literature on their site. Perhaps there are papers there that would be of interest.

http://www.selinc.com/sel-lit.htm

I took a quick glance through their list, and this one jumped out at me (regarding sympathetic tripping problem analysis / solutions):

http://www.selinc.com/techpprs/6061.pdf

GE also has a good amount of technical papers on their site. Again, there may be something of interest here.

http://www.geindustrial.com/industrialsystems/pm/notes/index.htm

Also, part of NERC's Compliance Program requires electric utilities to report relay misoperations as part of each Reliability Region's Compliance Program (planning standard III.A). I haven't dug through NERC's site (or regional reliability council sites) to find out if any of this information is publicly available, but if so it may be helpful as well.

http://www.nerc.com/~comply

 

[SidiropoulosM]

These are very useful comments, thanks to all.
Michael Sidiropoulos