Information Notice No. 88-58:Potential Problems with ASEA Brown Boveri ITE-51L Time-Overcurrent Relays
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
August 8, 1988
Information Notice No. 88-58: POTENTIAL PROBLEMS WITH ASEA BROWN BOVERI
ITE-51L TIME-OVERCURRENT RELAYS
All holders of operating licenses or construction permits for nuclear power
This information notice is being provided to alert addressees to potential
problems involving ASEA Brown Boveri ITE-51L time-overcurrent relays. It is
expected that recipients will review this information for applicability to
their facilities and consider actions, as appropriate, to avoid similar
problems. However, suggestions contained in this information notice do not
constitute NRC requirements; therefore, no specific action or written response
Description of Circumstances:
Several spurious actuations of ASEA Brown Boveri (ABB) ITE-51L relays have
occurred at the Beaver Valley nuclear power plant. These actuations resulted
in unnecessary interruptions of the electrical power supply to safety-related
equipment. The ITE-51L relays monitor circuit current. When the magnitude of
the current exceeds a reference value for a specific duration, the relay
actuates to energize the circuit breaker's trip coil. The licensee has
determined that the spurious relay actuations were caused by faulty silicon-
controlled rectifiers (SCRs) that were manufactured by the Motorola Company.
SCRs are solid-state devices that are used as electronic switches in
electrical circuits. When a voltage is applied across the terminals of the
SCR, the device is designed to allow current to flow only when "gated" or
switched on by the proper electrical signal. The SCRs that failed at Beaver
Valley allowed current to flow in the absence of the proper gating signal.
These "leakage" currents were of sufficient magnitude to energize the trip
coil of the associated circuit breaker.
The licensee was informed by Motorola that SCRs manufactured between the late
1970s and early 1980s are susceptible to this mode of failure and that these
SCRs are likely to fail within the first 2 years of service. Since 1982, all
SCRs manufactured by Motorola have been subjected to a "burn-in" test. In this
test, the SCRs are placed in a high-temperature environment both with and
without voltage applied. SCRs that pass this test are expected to perform
normally for an extended period.
August 8, 1988
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Beaver Valley Unit 2 has approximately 105 ITE-51L relays installed in safety-
related applications, and Unit 1 has 10. The licensee is testing all the
relays in Units 1 and 2 to determine whether the SCRs are faulty.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the
technical contacts listed below or the Regional Administrator of the
appropriate regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: K. R. Naidu, NRR
N. E. Fields, NRR
Attachment: List of Recently Issued NRC Information Notices
Page Last Reviewed/Updated Friday, May 22, 2015