ML17213B133

Forwards Addl Info Re 821210 Degraded Grid Voltage Protection Submittals,Per 820223 Telcon.Voltage/Time Setpoints Will Be Supported by Two Undervoltage Devices

ML17213B133
Person / Time
Site:	Saint Lucie
Issue date:	03/11/1983
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Clark R Office of Nuclear Reactor Regulation
References
L-83-139, NUDOCS 8303160200
Download: ML17213B133 (6)

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<<4L REGULA Y INFORMATION DISTRIBUTI SYSTEM AOCESSION NBRg8303160200 DOCeDATE: 83/03/11 NOTARIZED: NO ¹ FACIL:50-335 St. Lucie Plant< Unit ig Florida Power & Light Co. 05000335 AUTH ~ NAME AUTHOR AFFILIATION UHRIGeReEe -Florida Power 8 Light Co,-

NOTES'OCKET REC IP i NAME RECIPIENT AFFILIATION

.CLARKgR,AD Operating Reactors Branch 3 W

SUBJECT:

Forwards addi info re 821210 degraded. grid.vol,tage protection submit.tais per 820223 telcon,Voltage/time.

setpoints will be supported by two =undervoltage devices.

DISTRIBUTION CODE: A015S iCOPIES'ECEIVED!LTR. / ENCL, / SIZE:,

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FLORIDA POWER & LIGHT COMPANY March 11, 1983 L-83-139 Office of Nuclear Reactor Regulation Attention: Mr. Robert A. Clark, Chief Operating Reactors 8ranch g3 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Clark:

Re: St. Lucie Unit 1 Docket No. 50-335 Degraded Grid Voltage Protection During a telephone conference on February 23, 1982 with your staff, Florida Power 5 Light was requested to provide additional information and clarifi-cation regarding our degraded grid voltage submittals of December 10, 1982 (L-82-536 and L-82-537). The requested information is attached.

Should you or your staff have further qu'estions on this subject, please contact us.

Very truly yours Vice President Advanced Systems Il Technology REU/PLP/js Attachment cc: J. P. O'Reilly, Region II Harold F. Rei s, Esquire P NS-L I-83-181-1 8303160200 8303ii PDR hDOCK 05000335 r P PDR PEOPLE... SERVING PEOPLE

Glar'ifications to Florida Power & Light Company letters of December $ 0, 1982 (L-82-536 and L-82-537), Degraded Grid Voltage St. Lucie Unit Ill.

Reference:

NRC - Florida Power 6 Light telephone conference on February 23, 1983.

Clarification No. 1:

Describe the proposed undervoltage relaying logic fixed time, steps, fixed voltage, number of relays, etc.

The following describes the St. Lucie Unit //1 proposed undervoltage relaying logic for both the 480 volt and 4160 volt Class IE safety related busses.

On each of the 480 volt busses the following relaying logic is proposed.

Presently, an ITE type 27 fixed voltage fixed time relay is used. This relay, contact is in series with the safety injection signal, such that this relay could only actuate during an accident condition. In order to satisfy the staff requirement and preclude separation from the offsite source due to spurious actuation of a single relay following a safeguard signal, a second ITE type 27 will be installed. The two relays will be paralleled and their contacts will be series connected to produce the required acceptable coincident 2-out-of-2 logic per bus.

Each of the 4160 volt Class IE safety related busses will have a total of six (6) undervoltage devices.. These will be of a fixed time, fixed voltage type.

The present Westinghouse's CV-2--inverse time relays will not be utilized. As proposed in the Technical Specification, three (3) different voltage/time setpoints will be incorporated in 'the overall relaying logic scheme. Each set of voltage/time setpoints will be supported by a set of two (2) undervoltage devices. This scheme meets the staff requirement for a coincident 2-out-of-2 logic.

Ther'e is no intertie between the A and B 480 volt Class IE busses or between

'he A and B 4160 volt Class IE busses undervoltage tripping/diesel generator starting/load sequencing logics. Should testing or maintenance be required or a device malfunction occur, it would affect the respective bus only. The other bus will remain connected to its source and ready to initiate its diesel generator should it be required to provide protective action as specified in IEEE-279-1971. The 480 volt and 4160 volt schemes will include 'built in testability and annunication of by-pass in the control room.

Clarification No.2:

What is the equivalent voltage on the 4KV bus that corresponds to the 429 volts condition on the 480 volt bus?

A voltage of 429 volts on the 480 volt Class IE safety related busses corresponds to 94.4% or 3927 volts on the 4160 volt Class IE busses during the condition when the unit trips From full load and transfers the loads to the start-up transformer with a concurrent accident condition. At this voltage on the 4160 volt busses, the 4160 volt equipment is capable of starting and running. The 429 volt setpoint satisfies the staff request that the bus voltage of all safety related equipment be above their required starting voltage during an accident condition.

Clarification No. 3:

Clarify the 8 seconds (7 sec. + 1 sec) time delay on the 480 volt bus undervoltage relays.

For the case of loss of offsite power, the period between the time of an accident (safety injection actuation signal - SIAS) and the time when the safety injection system starts to pump emergency cooling water into the core is assumed to be 30 seconds in the FSAR accident analyses. This time includes a 10 second period in bringing the diesel generator up to speed and voltage. The 7 seconds + 1 second time delay for the 480 volt undervoltage bus relays comes into play only when accident concurrent with a degraded system voltage exists. Since under an

'n SIAS the diesel generator automatically starts, comes up to speed and voltage within 10 seconds and stands by ready to accept loads, the 8 seconds maximum time delay in the 480 volt relays do not add any additional time to the core cooling anlysis for accident condition concurrent.;with loss of offsite power.

The 8 seconds maximum time precludes spurious actuation due to momentary fluctua-tion in the system and the system is given an opportunity to remain on the preferred source.

Clarification No. 4:

Provide design information such as, relay types, one lines, etc., on the proposed undervoltage relaying logic for. the 480 volt and 4160 volt busses.

P Detailed design for the proposed scheme on Clarifications $ through 3 above are not yet available.

These designs will be finalized up'on acceptance of our proposed relay scheme with the NRC staff. The requested detailed designs can be forwarded to the NRC staff when complete.

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