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T&D World Magazine

Southwest Transmission Power Implements GPS Time Source to Synchronize Substations

Southwest Transmission Electric Power Cooperative Inc., the Arizona-based electric power cooperative that operates and maintains a power delivery system that includes 580 miles of transmission lines and 20 substations, has implemented Symmetricom’s XL-750 GPS Time Source. Accurate time stamping of events is fundamental to efficient fault diagnosis and efficient restoration of electric power service. The XL-750, an accurate GPS timing instrument for power industry substation and utility companies, synchronizes protection relays and other intelligent electronic devices (IEDs) that collect and time stamp fault data.

“Symmetricom’s ability to immediately deliver the XL-750 paid off for us right away,” commented Tom Spence, technical services manager for Southwest Transmission. “With data constantly flowing-in on disturbances ranging from open breakers to customers without power, having files with accurate time stamps has improved operational efficiency and customer service. Saving two hours on fault diagnosis time means two hours less time our customers have to go without power. The XL-750 also improved the efficiency of the billing process by providing reliable and accurate time to electronic data collection systems which eliminates manual double checking so we’re ensured customers are always billed correctly.”

The XL-750 was developed by Symmetricom specifically for the power industry. Using GPS satellites, the XL-750 generates accurate output pulses and time codes in multiple formats and offers timing accuracy (100 nanoseconds to UTC). The XL-750 synchronizes a wide variety of microprocessor-based power system equipment including: SCADA systems, remote terminal units (RTUs), protection relays, sequence of event recorders, digital fault recorders, power/tariff meters and other intelligent electronic devices (IEDs).

Southwest Transmission also expects the XL-750 to provide future benefits in relation to regulatory requirements such as support of synchrophasors derived from GPS synchronized measurements of voltage and current relationships throughout the power grid. With the XL-750 at each substation, the company expects it will be prepared for any mandatory compliance requirements.

The XL-750 also meets the recommendations of the North American Electric Reliability Council (NERC) for event timing, such as Recommendation #12 concerning GPS time-synchronized recording devices.

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