AC Substation Equipment Failure Report - nerc.com

1 nerc | AC Substation Equipment Failure Report | November 2014 I AC Substation Equipment Failure Report nerc ACSETF December 2014 Table of Contents Preface .. iii Executive Summary .. iv Introduction ..1 Chapter 1 Equipment Failure Analysis and Observation ..4 Chapter 3 Discussion of Observations and Recommendations .. 23 Chapter 4 ACSETF Roster .. 26 Appendix Analysis of TADS Data .. 29 nerc | AC Substation Equipment Failure Report | November 2014 ii Preface The North American Electric Reliability Corporation ( nerc ) is a not-for-profit international regulatory authority whose mission is to ensure the reliability of the bulk power system (BPS) in North America. nerc develops and enforces Reliability Standards; annually assesses seasonal and long-term reliability; monitors the BPS through system awareness; and educates, trains, and certifies industry personnel.

2 nerc s area of responsibility spans the continental United States, Canada, and the northern portion of Baja California, Mexico. nerc is the electric reliability organization (ERO) for North America, subject to oversight by the Federal Energy Regulatory Commission (FERC) and governmental authorities in Canada. nerc s jurisdiction includes users, owners, and operators of the BPS, which serves more than 334 million people. The North American BPS is divided into several assessment areas within the eight Regional Entity (RE) boundaries, as shown in the map and corresponding table below. FRCC Florida Reliability Coordinating Council MRO Midwest Reliability Organization NPCC Northeast Power Coordinating Council RF ReliabilityFirst SERC SERC Reliability Corporation SPP-RE Southwest Power Pool Regional Entity TRE Texas Reliability Entity WECC Western Electricity Coordinating Council nerc | AC Substation Equipment Failure Report | November 2014 iii Executive Summary Background nerc s AC Substation Equipment Task force (ACSETF) was formed to analyze one of nerc s top-priority reliability issues: ac Substation Equipment failures.

3 This Report presents the analysis of Substation alternating current (ac) Equipment failures and contributing causes based on the data gathered by the It summarizes contributing causes, observations, and recommendations to reduce the impact of Substation Equipment failures. As reported in nerc s 2013 State of Reliability report2 and reconfirmed in the 2014 State of Reliability Report ,3 ac Substation Equipment failures are a significant contributor to disturbance events and have a positive correlation to increased transmission outage AC Substation Equipment Failure data was assembled from nerc s Event Analysis Process,5 the Transmission Availability Data System (TADS)6 (including a voluntary survey7), and Equipment Failure data collected by the WECC Substation Work Group (SSWG).

4 8 The ACSETF analyzed ac Substation Equipment failures, identified possible root causes and contributing causes, and developed observations, conclusions, and recommendations to reduce the risk to BPS reliability by reducing the impact of ac Substation Equipment failures. The ac Substation Equipment Failure data varied from data source to data source. For example, the data was collected at various voltage thresholds, some data sources include Equipment nameplate information, and each data source had varying degrees of root cause investigation and coding. AC Substation Equipment Failures Impact Transmission Severity Metric Inherent in ac Substation Equipment Failure is an increased probability that additional BPS elements will also be forced out of service, potentially increasing the calculated value of the transmission severity metric.

5 The current method of calculating transmission outage severity does not include the impact of transformer outages and treats the impact of any line within a voltage class as identical, without regard to actual capacity or value to reliability of the integrated transmission system. It also does not consider the impact of outage duration in the calculation. The definition of transmission severity, and the function and configuration of ac Substation Equipment , naturally lead to a positive correlation of ac Substation Equipment failures with increased transmission severity. Transmission severity metrics and suggested improvements to its calculation are discussed further in this Report . The recommended improvements include adding an outage duration component and including transformer outages to the transmission severity metric calculation.

6 Automatic Outages from AC Substation Equipment Failures Decline In addition to the transmission severity metric, nerc metric ALR6-13,9 the ACSETF reviewed the metric Automatic Outages Initiated by Failed AC Substation Equipment /AC Circuit Equipment . An analysis of ALR6-13, provided later in the Report , revealed that ac Substation Equipment failures are on a downward trend and have been consistently 1 ACSETF Scope, 2 2013 State of Reliability Report , 3 2014 State of Reliability Report , 4 Transmission Severity, 2013 State of Reliability Report , 5 nerc Event Analysis Process, 6 TADS, 7 TADS Voluntary Survey, 8 WECC SSWG, 9 ALR6-13, nerc | AC Substation Equipment Failure Report | November 2014 iv Executive Summary at a low level of failures.

7 The ACSETF recommends the initiation of enhanced data collection on ac Substation Equipment failures. Additional information is needed on each Failure to identify Substation Equipment Failure trends. There may be opportunities for nerc to collaborate with other organizations for data sharing and collection. Observations and Recommendations The ACSETF does not believe that ac Substation Equipment failures are at a level that warrants immediate intervention to reduce the Failure rate. The 2014 State of Reliability Report states: The metric (ALR6-13) shows that outages per element demonstrate year-over-year improvement from 2011 to 2013. In fact, that metric has been consistently below outages per ac circuit due to ac Substation Equipment failures for six years now.

8 Nevertheless, the ACSETF recommends continued monitoring of ac Substation Equipment failures. This monitoring could identify emerging trends that need to be communicated to the industry. Rather than duplicate data that is being collected by other organizations, the ACSETF recommends that nerc research a cooperative method of acquiring and analyzing Substation Equipment Failure data with other organizations that are currently collecting Failure data and performing analysis. In addition to the suggestions above, the ACSETF also proposes following observation and recommendations: Table 1: Observations and Recommendations Observation Recommendation Referencing Section of Chapter 3 for Further Detail Reliance on TADS6 data and transmission severity calculation does not provide industry a complete picture of failed ac Substation Equipment s impact on reliability.

9 nerc should incorporate data from other sources and analyze the impact on BES reliability. nerc should consider improvements in transmission severity calculation as mentioned in Report . Transmission Severity and TADS Data The Failure of a circuit breaker to operate properly increases the probability that additional BPS elements will also be forced out of service, increasing the transmission outage severity of the incident. nerc should evaluate the Failure rate of circuit breakers and consider the impact of bus configuration on ac transmission circuit outages. Equipment Application, Bus configuration and Design Bus configuration is the primary determinant of the impact of breaker Failure on transmission outage severity. Entities should evaluate the impact of breaker failures on system performance when choosing bus configurations for new installations or modifying existing substations.

10 Equipment Application, Bus configuration and Design The duration of a BPS element outage is not captured in the transmission outage severity calculation. nerc should add a duration component to transmission outage severity calculation. Transmission Severity and TADS Data Transformer outages are not included in the transmission outage severity calculation. nerc should add a component to account for transformer outages to transmission outage severity calculation. Transmission Severity and TADS Data nerc | AC Substation Equipment Failure Report | November 2014 v Executive Summary Table 1: Observations and Recommendations Observation Recommendation Referencing Section of Chapter 3 for Further Detail Existing data collection processes are not sufficient for cause analysis of failed ac Substation Equipment .