After more than five years of research and development, and an investment of more than $2 million resulting in six different simulator designs, it is clear that a major breakthrough in relay testing has been achieved.
As a result of this investment of research time and money, transient testing of protection relays has proven to be a viable and necessary practice. Presently, commercial arrangements are in place to bring this new, affordable technology to the market for widespread, future use by the utility industry.
The viability and importance of this research was given recognition through organization of the First International Conference on Digital Power System Simulators, the first professional forum in the world devoted to the new development and application of digital simulators for relay testing. Texas A&M University, a significant contributor to this field of study, was awarded the conference held April 5-7, 1995, and co-sponsored by DOE-WAPA, the National Science Foundation (NSF), Electric Power Research Institute (EPRI), Florida Power and Light Co. (FPL), Electricité de France and Texas A&M University. |  In late 1989, the visionary research program was inititated and sponsored by EPRI, FPL, Pacific Gas and Electric Co., Houston Lighting and Power Co., and the Department of Energy-Western Area Power Administration (DOE-WAPA).
The approach, allowing testing of relays under actual fault conditions, proved a far more advanced method than the previously existing techniques based on a generation of phasors as an approximation of the fault transients. As a result of a successful study, the research was extended into development of various digital simulator configurations.
A prototype of a PC-based configuration was developed in 1992, with participation of Techron International Inc., a vendor of high-performance audio amplifiers. Techron’s contribution was the development of a commercial grade input/output (I/O) cabinet, containing digital to analog (D/A) subsystem and contact I/O, as well as voltage and current amplifiers. The PC-based simulator with two cabinets, was delivered to Florida Power & Light for Beta-site testing in 1993. In addition, one PC-based configuration was developed for further uses and evaluation at Texas A&M University University.
Development took yet another direction with the implementation of a two-terminal digital simulator for back-to-back testing of transmission line relaying schemes. The design was implemented using an IBM RISC 6000 workstation for improved software performance.
Two identical configurations, each equipped with two I/O cabinets, have been developed by Texas A&M University. One of these configurations has been delivered to WAPA for Beta-site testing, and the other is being used for further evaluations at Texas A&M.
These developments target open-loop relay testing applications, generating, processing and replaying fault waveforms into a relay for testing. The relay responses are then captured and presented to the operators. Even though this design falls short of real-time interactive applications, it does allow extensive signal processing supported with graphical user interface and database management. | In 1990, DOE-WAPA began sponsorship of research and development of a real-time digital simulator design capable of real-time interaction with a relay under test. This design requirement could only be met by developing a new transient simulation program and advanced I/O subsystem capable of outputting the transients, inputting the relay responses and altering the transients simulation in real-time.
The design solution, the first of its kind developed in the world, combined a commercial-grade, high-performance workstation, the I/O cabinet developed for the open-loop simulator project, and some custom-designed I/O interface boards. The design has proven that the real-time relay testing can be done at a lower cost than available in the past. The real-time simulator was delivered to WAPA in the spring of 1994.
In the meantime, a new real-time simulator project was initiated under sponsorship of Commonwealth Edison Co. (ComEd) of Chicago. The simulator was completed at the end of 1995 and delivered to ComEd in February of 1996. This design provides further enhancements in which both the real-time and the open-loop simulator operation are provided in the same design. |
