ML20023C524
| ML20023C524 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 05/13/1983 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8305170401 | |
| Download: ML20023C524 (4) | |
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PHILADELPHIA ELECTRIC COMPANY 23O1 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 SHIELDS L. DALTROFF ELECTR C PR D C ON May 13, 1983 Docket Nos. 50-277 50-278 Mr. John F.
Stolz, Chief Operating Reactors Branch 44 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555
SUBJECT:
Peach Bottom Proposed Technical Specification on Degraded Grid Voltage Protection Ref.:
Conference Call between G. E. Gears (NRC) and M.
B.
Ryan (PECO) on March 31, 1983
Dear Mr. Stolz:
4 In the referenced conference call on degraded grid voltage for Peach Bottom, Mr. G. E. Gears asked us to provide an explanation of the degraded grid voltage relay circuit (see Attachment) that was provided as an attachment to a letter sent to you dated March 10, 1983.
We have added information to the attached sketch to assist the reviewer, and this letter will provide an explanation of the relay circuit.
The loss of the voltage circuit indicates the availability of the 125 Vdc auxiliary control power and initiates an annunciator in the Control Room if 125 Vdc is lost.
In addition, when the test plug is removed during surveillance testing, the same annunciator will indicate that the relays are being tested.
The voltage on the source of each startup transformer supply breaker to each 4 kV Class lE bus is monitored by three relays.
The three relays are:
oof 8305170401 830513 PDR ADOCK 05000277 P
pg i
s Mr. J. F. Stolz Page 2 1)
An~IAV inverse time delay relay, 2)
An ITE-27D relay, and 3)
A CV-6 (inverse time) relay.
The first sensing channel on the attached schematic
.contains an auxiliary relay (Aux-1), two contacts from the IAV relay and a seal-in contact from the Aux 1 relay.
With normal supply voltage'available to the 4 kV bus, the upper IAV contact will be open and the lower-contact will be closed.
If the source voltage drops below approximntely 60% nominal voltage, the upper IAV contact will close and energize the coil of the Aux 1 relay.
A second contact.from.the Aux 1 relay is in the trip circuit of the normal supply breaker to each 4 kV class IE bus.
Energizing the Aux 1 relay will trip the supply breaker.
The relays and contacts contained in the second and~
third sensing channels and the trip logic section'of the attached schematic are to be installed for degraded grid voltage protection..
The second sensing channel contains an ITE 27 contact and two time delay to pick-up relays (TDPU).
The time delay relays are set to pick-up at six and sixty seconds.
The ITE.27 contact will be open if the source voltage is normal.
When the source voltage drops to 90%. nominal, the ITE 27 contact will close and start the timing of both the timers.
The third sensing channel contains a contact from a CV-6 type relay..The CV-6 has an inverse time characteristic.
This relay will operate if the source voltage drops below 87% nominal voltage and will take approximately 30 seconds to close its
-contact at 70% nominal.
If the CV-6 contact closes, it will energize the AUX 2 relay, close the AUX 2 contact in the breaker trip circuit, and trip the breaker.
The trip logic includes contacts of the two time delay pick-up relayri (TDPU), a test plug, a contact of the 14AK39A relay, and the number 2 auxiliary relay (AUX 2).
If a LOCA signal is present, relay contact 14AK39A will close.
When the 6 second timing relay in the second sensing channel completes its timing, its contact in the trip logic circuit will close.
If the contacts from~the 14AK39A relay and the 6 second TDPU relay are both closed, the coil of the AUX 2 relay will energize, close the AUX 2 contact in the supply breaker trip circuit and trip the breaker.
If no LOCA signal is present, or none occurs while the contact of the 6 second TDPU relay is closed, the contact of the 60 second TDPU relay will energize the AUX 2 relay when the 60 second TDPU relay completes its timing.
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Mr. J. F. Stolz Page 3 Contacts on the AUX 1 and AUX 2 relays connected in series are also wired to a test connector, which is used for functional surveillance testing.
The functional surveillance test will usually be performed without tripping the supply breakers to each 4 kV bus.
The AC connections to the three undervoltage relays are wired through a test block so that convenient connections can be made to a testing box during surveillance tests.
The wiring of the AUX 1 and AUX 2 contacts into the breaker trip circuit is also wired through an additional test block so that the breaker tripping by the undervoltage relays can be blocked for the duration of the surveillance test.
During the surveillance test, each undervoltage relay is made to operate individually be varying the voltage to the relay with a variac from a test box.
Correct operation will be verified and timing will be measured on the undervoltage relays, timing relays, and auxiliary relays by monitoring the AUX 1 and AUX 2 contacts at the test box.
A complete operating and timing check is thus made for the entire circuit, with the exception of an actual breaker trip.
Tripping of the breakers will be verified during refueling outages when the relays are recalibrated.
If you have any questions or require additional information, please don't hesitate to call.
Very truly yours, I
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^~f-Attachment cc:
R. A. Blough Site Inspector i
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