GENERATING UNIT PERFORMANCE METRICS
INTRODUCTION 2-2
I. DATA COLLECTION AND REPORTING 2-4
II. DATA ANALYSIS 2-12
III. BENCHMARKING PERFORMANCE 2-14
This section describes those methods and measures used to monitor and confirm the ultimate effectiveness of the maintenance program, or alternatively, alert CPUC management of the potential need to perform audits of generating asset owner compliance to the Generation Maintenance Performance Standards and Assessment Guidelines, as certified.
The ultimate objective of the Generation Maintenance Program is to improve generating capability within the State of California. This will lead to improved grid reliability. Therefore measurement of maintenance program effect on generation capability is an essential metric. For this purpose, the Capacity Unavailability Factor (CUF) was chosen as the primary performance metric.
The CUF is equal to the sum of all of the hours of lost generation in a period divided by the period hours, and expressed as a percentage. In essence, it is the percentage of Net Dependable Capacity generation that was not available to the grid over the reporting period due to maintenance, fuel limitations (hydro), or regulatory restrictions. It does not address whether or not the generating asset was bid into the system, nor does it recognize significant changes in generator operation (e.g., starts and stops, total generation, and operating hours) that could influence future availability or capability.
Planned Outage Hour + Maintenance Outage Hours + Scheduled Outage Extension Hours +
Unplanned (Forced) Outage Hours + Equivalent Unplanned Derate Hours + Equivalent Planned Derate Hours
CUF=----------------------------------------------------------------------------------------------------------------------------x 100%
Period Hours
CUF is numerically equal to NERC GADS EUF (North American Electric Reliability Council's Generation Availability Data System Services Equivalent Unavailability Factor). CPUC chose to modify the name and expand the terms in the numerator to make the equation clear as to the factors that are being utilized.
This factor was chosen as the primary metric because each factor in the numerator is believed to be sensitive to the effect of a change to the applied maintenance program. However, there is no single performance metric that can suffice to evaluate the effectiveness of a maintenance program, especially during periods when generator operational characteristics change significantly. Therefore, other operating parameters will be monitored along with CUF to assure that conclusions regarding plant operation are not drawn from an incomplete set of measurements.
It should also be recognized that this performance measure, despite its close relationship to the adequacy or effectiveness of the maintenance program, is still a historical or lagging indicator. Therefore, generating asset owners and the CPUC t should use additional information or measures to provide early warnings that some element of a maintenance program may have deteriorated. This can sometimes be better accomplished by ad hoc review of the raw data used to derive this upper tier performance measure.
For these reasons, the CPUC has adopted the North American Electric Reliability Council's (NERC) Generation Availability Data System (GADS) practice of generating asset owners reporting data in a raw format, and then storing the data in such a manner that CUF can be calculated from the raw data. This approach provides the added benefits of enabling other more detailed analyses of performance trends, with consideration of recent changes in operating practices and external factors such as evaluating CUF with the effects of fuel limitation and regulatory limitation filtered out. It also facilitates storage of information for reprocessing in the event that better higher-tier performance measures are developed in the future. This data can also then be used to assess past performance for benchmarking purposes.
