NERC PRC-23 Line Loadability
NERC PRC-23 Line Loadability
(OP)
I have been looking at the standarded PRC-23, which is in place to prevent loading and operator actions from tripping a relay. I have a long 345 kV line that has enough line impedance to limit the fault current far below out neighbor we are interconnect to short term thermal rating of the line. I am supposed to evaluate the loading of the line with 0.85 percent voltage and 30 degree power factor angle.
The part I don't get is that in the worksheets they draw a line from origin at 30 degrees representing the load and from that you get Zrelay30, which is point the line intsects the zone protection. Why isn't the 30 degree load line drawn so that it intersects the impedance point that represents the end of the line?
http://www.nerc.com/docs/standards/sar/Relay_Loada...
My artistic rendering of what I am talking about.
http://ge.tt/58RbA1s
The part I don't get is that in the worksheets they draw a line from origin at 30 degrees representing the load and from that you get Zrelay30, which is point the line intsects the zone protection. Why isn't the 30 degree load line drawn so that it intersects the impedance point that represents the end of the line?
http://www.nerc.com/docs/standards/sar/Relay_Loada...
My artistic rendering of what I am talking about.
http://ge.tt/58RbA1s






RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
Normally it is true but in some case where it is not true, then the load encroachment will be use to overcome the issue
RE: NERC PRC-23 Line Loadability
RE: NERC PRC-23 Line Loadability
Figure out your emergency rating, add 50%, give it a 30 degree angle, assume 85% nominal voltage and plot what the relay sees. Then draw a line from the back to th origin, probably comes out pretty close to 30 degrees.
RE: NERC PRC-23 Line Loadability
Most of us use use the first requirment to meet the standard for lines, although there are twelve other ways to meet the standard.