1

NPCC – A-2

Dr. Mayer Sasson

Transmission Planning

Consolidated Edison of New York

June 1, 2006

Presented to the NYSRC-RRS

2

Purpose NYISO stated to the NYSRC EC that in its work on the

Comprehensive Reliability Planning Process (CRPP) it found that its rules where less stringent than those of the NPCC (A2 Criteria) and they where therefore going to follow A-2

EC asked RRS to conduct a review and report back at its June meeting

This presentation to RRS is intended to review NPCC Criteria document A-2, especially in relation to

Conditions for the calculation of normal and emergency transfer limits Determination of which limits are used in LOLE studies

The purpose of reviewing the NPCC A-2 criteria is be to serve as a basis for conducting the RRS review of the NYSRC rules

NYSRC reliability rules must be consistent with, but can be more stringent or more detailed than, those of NERC and NPCC, but never less stringent or inconsistent

3

NYISO Comprehensive Reliability Planning Process Reliability Needs Assessment (RNA)

Purpose of RNA: Ensure that all NYSRC reliability rules are observed throughout the horizon period

Ten year horizon Defined assumptions on future facilities Transfer limits determined for system to meet all

transmission design criteria Determine transfer limits used in LOLE calculations Needs defined by years in which NYCA LOLE > 0.1 Responsible TO(s) assigned

Responsible TO backstop solutions proposed Comprehensive Reliability Plan (CRP)

NYISO acceptance of proposed backstop solutions NYISO evaluation of impact on transfer limits and LOLE After NYISO verification that system will meet all NYSRC

reliability rules, NYISO issues CRP

4

Present Review of NPCC A-2 and NYSRC Reliability Rules Review NPCC A-2 to clarify

Conditions for determination of normal and emergency transfer limits

Use of normal and emergency transfer limits Limits used in LOLE studies

Review of NYSRC Reliability Rules Adherence to NPCC A-2 Clarity

5

NPCC A-2 Section 3: General Requirements Basic Criteria are not necessarily applicable

to those elements that are not part of the bulk power system or in portions of the system where instability or overloads will not jeopardize the reliability of the remaining bulk power system

6

NPCC A-2 Section 3: Resource Adequacy – Design Criteria Area probability of disconnecting firm load

due to resource deficiencies < 0.1 years Due allowance for demand uncertainty,

scheduled outages, forced outages, assistance over interconnections from neighboring regions, (emergency?) transmission transfer capabilities and capacity and/or load relief from available operating procedures

7

NPCC A-2 Section 4: Resource Adequacy – Operating Criteria Each area shall have procedures in place to

schedule outages such that available resources meet area’s forecasted load plus reserves requirements

8

NPCC A-2 Section 5: Transmission Design Criteria Applies to the bulk power system of each

area Applies after the loss of any critical facility,

assuming area generation and flows have been adjusted by use of 10-minute reserves, PARs and HVdc control

9

NPCC A-2 Section 5.1: Stability Assessment Stability shall be maintained during and following

the most severe of the following contingencies a. 3-phase fault with normal clearing

b. Simultaneous phase-to-ground faults on two phases on a multiple circuit tower with normal clearing

c. Phase-to-ground fault with delayed clearing

d. Loss of any element without fault

e. Phase-to-ground on a circuit breaker with normal clearing

f. Loss of both poles in a DC facility without a ac fault

g. Failure of circuit breaker to operate when initiated by an SPS

10

NPCC A-2 Section 5.2: Steady State Assessment

a. Adequate reactive power shall be installed in each area to maintain voltages within normal limits for pre-contingency conditions, and within emergency limits for all post-contingency conditions listed in 5.1

b. Flows shall also be within normal limits for pre-contingency conditions, and within emergency limits for all post-contingency conditions listed in 5.1

11

NPCC A-2 Section 6: Transmission Operating Criteria Individual areas shall be operated in a

manner such that the contingencies noted in Sections 6.1 and 6.2 can be sustained and do not adversely affect other areas

12

NPCC A-2 Section 6.1: Normal Transfers Pre-contingency voltages and flows shall be

within normal limits Stability of the bulk power system shall be

maintained following the most severe contingencies listed in 5.1 with due regard to reclosing

Voltages must be maintained within normal limits pre-contingency and within applicable emergency limits for all contingencies listed in 5.1

13

NPCC A-2 Section 6.2: Emergency Transfers When firm load cannot be supplied within

normal limits, transfers may be increased to the point where pre-contingency voltages and flows are within applicable emergency limits, provided that, Stability of the bulk power system is maintained

following the most severe contingency a. and d. of the list in 5.1 (certain single element contingencies)

Voltages and flows shall be within applicable emergency limits for same contingencies

14

Transfer Limits Used in LOLE Calculations Since

Design LOLE calculations measure probability of disconnection of firm load (Section 3)

And Transfers are allowed to increase to emergency limits prior

to the disconnection of firm load (Section 6.2) Therefore,

LOLE calculations (RNA/CRP and IRM/LCR ) must use emergency transfer limits as defined in Section 6.2

The NYSRC rules also require the same Observation:

Emergency transfer limits are the emergency thermal limits unless limited by post-contingency stability and violation of emergency low voltage limits (Section 6.2)

15

Conclusions

The NYSRC rules were written to be consistent with, and not less stringent than, NPCC A-2 The entire Table A-1 (identical to the list in 5.1 of A-2)

contingencies apply to the calculation of normal limits while only contingencies listed under “a” and “d” apply to the calculation of emergency transfer limits

Emergency transfer limits must be used in all LOLE studies, such as in the RNA and in the IRM/LCR studies

NYSRC rules in Sections on Planning (Design), Operations and Resource Adequacy need to be reviewed by RRS to meet the task assigned by the EC