Managing Reliability Risk with Spare Transformers Brochure

Access to spare transformer equipment for the Bulk Power System is an important technique for managing reliability risk in the utility industry. Organizations including the North American Electric Reliability Cooperation (NERC) and the Edison Electric Institute (EEI) are increasingly providing programs and guidance to help minimize the length of power supply disruptions and the associated impacts that can result from transformer failures. Background An aging energy infrastructure, the threat of physical and cyber terrorism, and the potential impacts of geomagnetic disturbances have increased the vulnerability of large power transformers. In May 2012, NERC’s Severe Impact Resilience Task Force identified numerous recommended actions for industry to limit significant power disruptions, including: “Consider the spare equipment critical to BPS restoration and ways to improve the availability of these spares.” Transformer replacement is costly and logistically challenging. It also requires a long lead time for engineering and delivery of equipment. The order and delivery of a transformer for in-kind replacement from a manufacturer can take up to several years depending on the situation. The availability of a suitable spare, replacement transformer within a given utility however, typically allows circuits to be restored to normal configuration in short periods of time. Determining the risk associated with electrical equipment failure requires an assessment of the following factors: • Equipment age • Equipment condition • Equipment design • How critical the equipment is to the system • Impact to the customer should the equipment fail Resilience and readiness calls for more than just the identification of needed equipment. Avoiding the risk of an extended loss of supply in the event of equipment failure requires careful pre-planning and where possible engineering. The availability of spare transformers contributes to the availability and reliability of the transmission system only if transportation and logistical plans, engineering and business arrangements are prepared in advance to minimize reliability and security risks. For more information, please contact: Steve Persutti, VP of Operations Development, Power Delivery Engineering spersutti@trcsolutions.com | 860-503-1681 | www.trcsolutions.com Business Issues and Good Utility Practice Although utilities typically hold an inventory of spare transformers, the quantities may not be adequate nor have the spares on hand been reviewed and compared against potential needs in several years. Due to the long-lead times associated with replacing power transformers, regular reviews of stock levels and participation industry wide spares sharing programs should be undertaken based on asset replacement rates and anticipated or experienced failure rates. In-house combinations of mobile transformers and spare transformers are typically relied upon to provide necessary replacement of medium-voltage level transformer capacity. To keep the population of high cost mobile transformers to a minimum, and to address the lack of availability of mobile transformers at the higher voltage levels, a number of spare transformers are typically retained as permanent spare replacements for failed units. A utility-wide strategy must provide for the review of and, where necessary, the purchase of spare transmission transformers. Essential elements of an effective spare equipment strategy include: • Reviews of present stock levels; • Transportation logistics plans; • System protection procedure; • Engineering pre-planning; and a • Secure, logical physical location for spares storage. Good utility practice dictates that the minimum target level of spare transformers is one spare transformer for each of the major voltages and/or electrical vector and impedance configurations unless: • Range of applicability of a particular spare can be extended to cover several MVA ratings and reduce the number of spare transformers required. • Alternative power system configuration options are available. • Populations of a specific family exceed a value of in-service units which will warrant an additional spare. • The failure rate of a specific family is above the average transformer failure rate. Spare Equipment Programs Participating in spare equipment programs is an economical and efficient way for utilities to enhance their spare transformer resources. In 2006, federal energy regulators approved the EEI Spare Transformer Equipment Program (STEP) to strengthen the ability of the utility industry to restore the transmission system more quickly in the event of a terrorist attack. STEP represents a coordinated approach to increasing the inventory of spare transformers and streamlining the process of transferring needed transformers to affected utilities. For more information, please contact: Steve Persutti, VP of Operations Development, Power Delivery Engineering spersutti@trcsolutions.com | 860-503-1681 | www.trcsolutions.com Under the EEI program, each participating electric utility is required to maintain and, if necessary, acquire a specific number of transformers. STEP requires each participating utility to sell its spare transformers to any other participating utility that suffers a "triggering event," defined as an act of terrorism that destroys or disables one or more substations and results in the declared state of emergency by the President of the United States. NERC’s Spare Equipment database also supports industry wide identification of spare equipment. The program is a key tool to address the potential impacts of geomagnetic disturbances or terrorism events. Several major US utilities have recorded their spare transformers in the program. As of July 2013 there 15 participating utilities and 47 identified spare transformers. The program, while currently voluntary, may become mandatory as more utilities participate. More information is available in a recent webinar from NERC. Regulatory Considerations State regulatory restrictions on the movement of assets from one utility to another may limit the effectiveness of these spare transformer sharing programs. Spares identified or obtained from the EEI STEP program are not subject to these constraints if a U.S. president has declared a state of emergency. However, this is a significant limitation on the usefulness of the program for normal spares activity. Be Prepared To effectively manage reliability risk, utilities must assess their necessary supply of spare transformers and other equipment. Identifying the most appropriate storage location for those assets and securing your spare equipment is more important than ever. Quantity, condition, location, and suitability of spare transformers should be independently reviewed and spare asset levels managed where surplus or obsolete stocks are identified. In order to keep transformer moves to a minimum, a spare is typically installed permanently where it meets voltage, vector relationship, impedance, and present/projected future MVA ratings. System spares replenishment should be addressed through comprehensive system spare equipment projects that go beyond transformers and consider other major, long lead time equipment, such as circuit breakers. To minimize the level of future spare transformer requirements, a review should encompass the entire utility and subsidiary companies. For more information, please contact: Steve Persutti, VP of Operations Development, Power Delivery Engineering spersutti@trcsolutions.com | 860-503-1681 | www.trcsolutions.com Resources NERC Industry Webinar: Spare Equipment Database • Presentation • Recording NERC Spare Equipment Database EEI Spare Transformer Equipment Program (STEP) TRC Power Delivery Engineering Services TRC NERC Compliance Support Services About Us TRC’s Power Delivery Engineers provide full service transmission, substation and relay engineering, consulting and construction management for utilities, municipalities and industry. Comprised of over 800 personnel, many of whom are experienced utility engineers, our project teams know how to plan, design, and install facilities that meet a client’s financial, technical, and scheduling goals. This regulatory update is a service to our utility clients, helping keep them informed of issues that impact their reliability risk and business goals. For more information, please contact: Steve Persutti, VP of Operations Development, Power Delivery Engineering spersutti@trcsolutions.com | 860-503-1681 | www.trcsolutions.com