SCREENING METHOD FOR DETERMINING IF A STUCK BREAKER CONTINGENCY HAS UNACCEPTABLE INTER-AREA IMPACT

The following presents the general philosophy/method for determining if a stuck breaker (SB) contingency will have unacceptable inter-Area impact.

1)	Simulate the SB contingency.

2)	Identify any circuits that are overloaded at or above their STE rating.

3)	Open the STE overloaded circuits and rerun the loadflow.

4)	Repeat steps 2) and 3) and determine inter-Area impact as follows:

a)	If the circuit STE overloads/openings stop and the case solves without severe voltage/reactive conditions, inter-Area impact is acceptable.

b)	If the circuit STE overloads/openings continue to the point where a circuit in New York becomes overloaded at or above its LTE rating, (STE allowed for underground cable circuits  (except 1385 Norwalk Harbor-Northport 138 KV cable and CONED-PSE&G tie lines, which are cable circuits) unacceptable inter-Area impact is indicated. 

c)	If the circuit STE overloads/openings continue to the point where the case will not solve, demarcate the subarea in New England that would separate from the rest of the system. This should be based on the cascading overload pattern evidenced by the loadflows. Then go back to the original case and calculate the net power flow into or out of the subarea that would be separated. Unacceptable inter-Area impact is possible if the subarea is supplying more than 1300 MW to the rest of the system or if it is absorbing more than 1200 MW of power. If the subarea is supplying < 1300 MW or absorbing < 1200 MW, the SB contingency would not have unacceptable inter-Area impact.

OP 19 AppG.rtf
8/31/98