Under reaching Zone 1 of Distance relays

[HiSet]

Generally speaking the zone 1 of distance relays is intentionally set to under reach the line length to the tune of 70 to 90 %. Also we know that the under reaching zone 1 is likely to over reach in case the parallel line is out of service and earthed. I invite reders your comments on ways to over come this quandary.
Regards

 

[Bung]

almost all the major relay manufacturers have technical literature on their websites that discuss problems like this.

Bung
Life is non-linear...

 

[davidbeach]

That's why relays have multiple settings groups. One group is two lines in service, another is one line in service with the other open, a third setting group would be one in service and the other grounded. The proper control system scheme will then switch between settings groups as needed.

 

[sanalv]

If I well understand your question, you can have a look to Walter A. Elmore, "Zero-sequence mutual effects on ground distance relays and fault locators", 46th Annual Protective Relaying Conference at the Georgia Institute of Technology, Atlanta, Georgia, April 29-May 1, 1992.

 

[HiSet]

Sanalv,
Could you send me a link to this paper ?
Thanks

 

[sanalv]

Sorry HiSet.

I have read some technical documents that reference the paper, I have been looking for it on the Net with no luck at all, up to date.

 

[alehman]

Take a look at this instruction manual. There are six setpoint groups (bottom of page 2). Each setpoint group is a complete set of relay settings. The active group is selected by a control input signal.

http://www.selinc.com/datasheets/321ds.pdf