what exactly is a remote substation?

[jacksonville]

hi there

i am doing a fault analysis on a power system that consists of two substations interconnected by a line.

The purpose of this project is to determine the positive and zero sequence impedances of the line and the source for different types of faults. I am doing this so i can determine the correct settings for the relays by use of a specific software.

The fault is applied on the line interconnecting these substations. How do i identify the local and remote substations? Does it depend on the fault location?

please assist

thank you

 

[cranky108]

The local substation is where you are standing. The remote substation is somewhere else.

 

[davidbeach]

Somewhat more specifically, local is the home of the relay and remote is the far end of the protected line. In that regard it doesn't matter where you are standing. Relays at the other end of the line will have the opposite definition of local and remote.

 

[jraef]

My smartypants answer is that the Remote Station is at least 100 miles away and staffed by the people without incriminating pictures of the boss...


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[jacksonville]

thanks Davidbeach.

so would it be correct in saying that the substation closest to the fault location is the local substation?( depending on the reach of the relay),and the other substation then become the remote substation.

 

[davidbeach]

No. The local substation is where the relay is. The fault can be close to, or even beyond, the remote substation.

 

[rasevskii]

This sounds like a distance relay.Is this an existing or a theroretical installation?

Usually, about 90% of the line impedance is considered to be Zone 1 as seen by the relay, beyond this is the remote substation, which is in Zone 2, most of the impedances of any lines beyond that are Zone 3. Zone 1 has a certain ohm setting and no time lag, Zone 2 a higher ohm setting and usually a half second or 1 second time lag. Zone 3 yet higher with additional time lag.

Faults are phase to Earth (each phase) Phase to phase, or 3-phase short circuit.

The impedance measurement is directional, the relay looks outward to the line and sees only faults occurring in that direction. Faults in back of the relay location are not seen.

At the remote substaion there would be another distance relay looking toward the first substation. Unless there is no source of power beyond the remote station, i.e. a dead ended sysrem.

Go to the ABB library web site and look up descriptions for the classic relays RAZFE, RAZOA, REZ (1, 2, etc. ) there is a lot of info on calculations, theory, and info on distance relays there.

regards, rasevskii

 

[davidbeach]

Zone 2 delay no more than 0.35 seconds without extreme circumstances, Zone 3 is typically reverse (at least for those of us who use SEL relays) and used in communications assisted tripping schemes, Zone 4 either 0.7 or 1.0 seconds. The sags associated with Zone 2 clearing at 0.35 seconds are bad enough, I can't imagine allowing 1 second clearing in the protected zone.

 

[rasevskii]

for Davidbeach:

Sorry, I was used to the old days in the Middle East, out in the desert, where we had all those old relay types...IIRC the smallest time increment was 0.5 seconds...

rasevskii

 

[cranky108]

Zone 3 could be either forward or reverse, depending on your application. I've used SEL relays both ways.
However on short lines I would not set zone 1 more than 80% of the line.

 

[jacksonville]

thanks guys, i think im a bit more familiar with the concept now..