Metallic return transfer breaker development. Research project 667. Final report
EPRI and Hughes Research Laboratories (HRL) contracted to develop and test a metallic return transfer breaker (MRTB) utilizing the novel Hughes crossed-field tube, which, on an earlier contract (EPRI Project RP 91) had become the world's first HVDC circuit breaker to successfully clear a fault on a multiterminal HVDC system. The function of an MRTB is to transfer load current between earth and metallic returns on a bipolar HVDC system. THE MRTB with a single crossed-field tube, mechanical in-line switch (MIS), and zinc-oxide resistor was completed and successfully passed high-voltage withstand and electro-magnetic interference (EMI) tests at Hughes Malibu facility in July of 1978. The unit was installed at the Celilo station of the Bonneville Power Administration in December of 1978. An operational test in December 1978 was to include transfer from the earth-return to the metallic-return mode at line currents 300, 600, 1200, and 1800 A. The 300- and 600-A tests were completely successful and produced no unusual results. At the start of the 1200-A transfer, an arc was struck from the top of the entrance bushing to the enclosure of the interrupter, followed by an explosion that blew the doors off the enclosure. An ensuing fire was self-extinguishing. A thorough analysis revealed that the primary cause of failure was an arc struck from a temporary instrumentation lead previously opened at the connecting lug by excess tension from mechanical flexing. A secondary cause was rupture of the case of the interrupter head of the MIS, which created a flammable state within the MRTB enclosure. EPRI and HRL jointly decided termination appeared the most practical option because the MIS could not easily be replaced by HRL with a unit of different design. EPRI decided to pursue an alternative approach. The control and communication electronics of EPRI MRTB, which survived the explosion without failure, could be utilized.
- Research Organization:
- Hughes Research Labs., Malibu, CA (USA)
- OSTI ID:
- 6780773
- Report Number(s):
- EPRI-EL-1816
- Country of Publication:
- United States
- Language:
- English
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CIRCUIT BREAKERS
DC SYSTEMS
DESIGN
ELECTRICAL EQUIPMENT
ENERGY SYSTEMS
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FAILURES
HVDC SYSTEMS
PERFORMANCE TESTING
POWER SUBSTATIONS
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