Figure 1. WECC Remedial Action Scheme type definitions RAS Reviews Historically WECC has concentrated review efforts on schemes that have larger system impact, (WAPS) even prior to adopting formal type definitions. Prior to about 2011, LAPS, while not being completely ignored, were reviewed generally only at the request of the owner or when some misoperation raised scheme visibility within WECC. The 300 MW firm load loss in both LAPS and WAPS definitions is derived from the EOP-004, Attachment 1, DOE-OE417 form as well as the NERC Event Analysis categories (Category 2) used when these classifications were first developed. The 1000 MW generation loss value was selected in part as half the upper limit to the NERC Category 2 event; in addition, no WECC non-nuclear individual units were this large, and no WECC RAS were then operated to trip nuclear units. WAPS remain critically important to BES operation and still require detailed reviews. Review procedures for these schemes remain essentially unchanged. While a LAPS misoperation will not result in a large-scale impact on the system, these schemes still require a level of WECC review to encourage reliability and document what the scheme does. Similarly, a SN may have a significant system impact, but does not have the same single component failure requirement as a LAPS or WAPS. The overall WECC review process is outlined in Figure 2. Figure 2. WECC Remedial Action Scheme review process. Owner responsibilities are color coded in yellow and WECC responsibilities in blue. Since WECC generally does not review LAPS beyond the agreement that a scheme is a LAPS, WECC accepts the classification of such schemes. However, WAPS and SN are reviewed in substantial detail, which allows WECC to approve these schemes. WAPS are examined by the RASRS at the level of detail necessary to provide an review to “outside” ensure satisfying the requirements of PRC-012-1. Safety Net RAS are generally reviewed at a slightly lower level of detail than WAPS because the TPL standard does not require that such extreme events actually be remediated. Therefore, SN RAS do not require the same single component failure performance as LAPS or WAPS, but still require that system
Figure 1. WECC Remedial Action Scheme type definitions RAS Reviews Historically WECC has concentrated review efforts on schemes that have larger system impact, (WAPS) even prior to adopting formal type definitions. Prior to about 2011, LAPS, while not being completely ignored, were reviewed generally only at the request of the owner or when some misoperation raised scheme visibility within WECC. The 300 MW firm load loss in both LAPS and WAPS definitions is derived from the EOP-004, Attachment 1, DOE-OE417 form as well as the NERC Event Analysis categories (Category 2) used when these classifications were first developed. The 1000 MW generation loss value was selected in part as half the upper limit to the NERC Category 2 event; in addition, no WECC non-nuclear individual units were this large, and no WECC RAS were then operated to trip nuclear units. WAPS remain critically important to BES operation and still require detailed reviews. Review procedures for these schemes remain essentially unchanged. While a LAPS misoperation will not result in a large-scale impact on the system, these schemes still require a level of WECC review to encourage reliability and document what the scheme does. Similarly, a SN may have a significant system impact, but does not have the same single component failure requirement as a LAPS or WAPS. The overall WECC review process is outlined in Figure 2. Figure 2. WECC Remedial Action Scheme review process. Owner responsibilities are color coded in yellow and WECC responsibilities in blue. Since WECC generally does not review LAPS beyond the agreement that a scheme is a LAPS, WECC accepts the classification of such schemes. However, WAPS and SN are reviewed in substantial detail, which allows WECC to approve these schemes. WAPS are examined by the RASRS at the level of detail necessary to provide an “outside” review to ensure satisfying the requirements of PRC-012-1. Safety Net RAS are generally reviewed at a slightly lower level of detail than WAPS because the TPL standard does not require that such extreme events actually be remediated. Therefore, SN RAS do not require the same single component failure performance as LAPS or WAPS, but still require that system
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