ML20195H642
| ML20195H642 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/23/1987 |
| From: | Rhoads E BBC BROWN BOVERI, INC. (FORMERLY BROWN BOVERI CORP. |
| To: | Russell W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| REF-PT21-88-148-000 PT21-88-148, PT21-88-148-000, NUDOCS 8811300526 | |
| Download: ML20195H642 (1) | |
Text
,
e
's 1e BBC Brown 15overi
, _,m.,
l Switchgear Products Group esc crown soverl.inc.
4379 County We Road i
Cva~ n, P A 18914 r,
- (215)822 4270 t
December 23,1987 g.. 12isier2-42n i
i Mr. William T. Russell Regional Administrator r
Region !
l U.S. Nuclear Regulatory Commission 1
631 Park Avenue King of Prussia, PA 19406
(
l Gentlement Enclosed is a copy of a 10CFR Part 21 Report filed with your office in Washington, D.C. On the advice received from the NRC in Washington ou i
December 22,1987, the report was addressed to Mr. Carl Berlinger.
I I
Subsequently, on December 23, 1987 we were advised to address any future Part 21 reports to your attention in Region I.
f t
Our office willbe closed from December 24,198 ? through January 4,1988. If f
you have any questions, you may reach me at hotie (215) 265-0699.
[
f I
ZAd..A E.W.RilOADS
[
Manager Quality Assurance l
L I
EWR/jm Enclosure 1
1 1
I i
j 1MI ha i
se k
f
\\ \\
o t,
Brown Boveri Switchgear Products Group sec grown soved,ine.
as Sentry Paa mar 610 Seetry Park Derember 22,1987 B6e Ben. PA 19422 Phone (215)834 7400 Mr. Carl Berlinger, Branch Chief, 1
Generic Communications U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Part 21 Report 27N Undervoltage Relay Only With !!armonic Filter Option (Catalog No. 211T4175-IIF) r Dear Mr. Berlingert l
An LER (87-023) issued by Philadelphia Electric Limerick Unit #1 describes an RIV (Reactor Protective System) breaker trip that was caused by a spurious undervoltage
{
relay trip signal.
t i
A subsequent investigation by BBC Brown Boveriinto this false trip signal experienced with the 27N Undervoltage Relay (Catalog #211T4175-HF) indicates that the misoperation occurred on the energized switchgear when the control voltage was reapplied af ter having been off for a period of time.
l Under these conditions, with 120 VAC input and no control voltage, a smalllow level i
voltage is coupled into the relay's internal circuits through an input pro'tection circuit.
Ris circuit consists of two diodes, D1 and D2, which are connected from a gate of input op-amp, U1, to the plus and minus 15 volt reference buses in order to protect U1 from any possible overvoltages. !!ence they are normally reverse biased and in an off state.
I When there is r.o control voltage present, the gate of U1 is not stabil:ed to its norn al l
condition of 0 volts, and can rise a few volts. His allows D1 and D2 to couple a small amount of the input AC signalinto the reference huses, which then rise to a few tenth's t
of a volt. his levelis just enough to partially energine some of the inputs to some IC's, which may cause them to be in an indeterminate state. Thw when the control voltge is l
restored, the circuit may not be able to follow the normal, orderly power-up dest ned
(
2 into the relay. When the condition occuri, a false trip signalis generated sbout 30 msec after the control voltage is restored, persists for about 30 msee and then clears.
l j
This condition occurs only in the 27N undervoltage relay model when the !!armonie Filter option is installed. hfodels without this option have a fast settling time which overrides l
any indeterminato state conditions, j
i A review of the input circuit showed that the protective diodes could be re-connected e J
by pasa excess input levels to the zero bus and give equal or better protection and yet not change the calibration or operation of the relay in any way. Ein change elin.taates the coup 1mg path and allows the circuit to always power-up from 0 volts as intended.
- A !!3W-
--1 T
t
b, s.
BBC e.
,,.c.e Mr. Carl Berlinger December 22,1987 Page2 Other 27N undervoltage relay
.ch the Harmonic Filter option) which hcve been supplied for Nuclear Safety Related applications are included in the attached list. The users have already been notified about the potential for tnisoperation when control voltage has been removed and then reapplied to energizeu cwitchgear. Users of the 27N undervoltage relay without the liarmonic Filter option will also receive a copy of this report for their information.
Modifications can be accornplished in the field by qualified electronics technicians using
. arts and instructions furnished by BBC Brown Boveri or the rehys may be returned to l
p the f,actory.
W q,
7 tad.yv /tt J/M <['
/d/ /p A. F. KAISER, President Switchgear Products Group EWR/jm Attachment l
l
%~.
.is
> %.: s BBC
... ~.. ~,.
27 N Relays Supplied wi th liarmonic Fi l t e r s Cat. 4211T4175-HF BBC SO
[9-Utility and Plant
_IQ QTY SN's 52891 Mississippi Power and Light GG10674 4
1368 thru 1371 Grand Gulf 53978 Mississippi Power and Light GG11245 1
1376 Grand Gulf 54525 Philadelphia Electric Co.
527741 2
1390, 1391 Limerick
' Tulsa) 55009 Philadelphia Electric Co.
EEZ76320 14 1412 thru 1425 Peach Bottom 55048 Philadelphia Electric Co.
3709584 4
1426 thru 1429 Limerick 11184 Philadelphia Electric Co.
18250F-4 1256 thru 1259 Limerick 00426
,