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Forwards Response to 980728 RAI Telcon Re Ifis Contained in Insp Repts 50-280/98-201 & 50-281/98-201
	ML18153A322
Person / Time
Site:	Surry
Issue date:	09/02/1998
From:	Ohanlon J; VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	50-280-98-201, 50-281-98-201, 98-452, NUDOCS 9809140135
	Download: ML18153A322 (12)
	v • d • e

-.

VIRGINIA ELECTRIC AND PowER CoMPANY.

RICHMOND, VIRGINIA 23261 September 2, 1998 Document Control Desk United States. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.98-452 NLOS/GDM R2 Docket Nos. 50-280/50-281 License Nos. DPR-32/DPR-37 PLANT DESIGN INSPECTION INSPECTOR FOLLOW-UP ITEMS (IFls)

REQUEST FOR ADDITIONAL INFORMATION During a July 28, 1998 telephone call between the NRG and Virginia Electric and Power Company staff, design information associated with two IFls identified in the Surry Plant D~sign Inspection Report Nos. 50-280, 281/98-201 was discussed.* The two IFls were 50-280/98-201-04, Motor Thermal Overload for 1-SI-P-1 B Pump and 50-280/98-201-05, Adequacy of 4160 VAC Electrical Cables to Withstand Fault Current. The discussion was based on a list of information previously requested by the NRG via facsimile on July 21, 1998. The design information was requested to support internal NRG staff evaluations of these two items.

At the conclusion of the telephone call, the NRG requested that the information discussed be provided formally. Therefore, we have documented the requested information in the attachment.

If you have any further questions or require additional information, please contact us.

Very truly yours, James P: O'Hanlon Senior Vice President - Nuclear Attachment Commitments contained in this letter: None.

9809140135 980902

-PDR ADOCK 05000280 G

PDR I I I I

~--

cc:

U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station

ATTACHMENT PLANT DESIGN INSPECTION INSPECTOR FOLLOW-UP ITEMS (IFls)

SURRY POWER STATION UNITS 1 AND 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION IFI 50-280/98-05, Adequacy of 4160 VAC Electrical Cables to Withstand Fault Current

1. Maximum fault current at 4160 volt switchgear from:

Bus 1 H will be discussed; 1J, 2H, and 2J are similar. Calculation EE-0334 was reviewed. Only three phase faults will be discussed. Available phase to ground fault current is limited to approximately 1500A.

a) Offsite source:

The fault current delivered from the offsite source is *nearly constant for all plant conditions. The current varies from 24000 to 25000 amperes.

b) EDG: 3440 kVA, 4160V, wye, ungrounded.

Direct Axis Subtransient Reactance = 0.298 per unit at rated kVA Direct Axis Subtransient Short Circuit Time Constant= 0.017 seconds (1 cycle) at 75 degrees Celsius Direct Axis Transient Reacta*nce = 0.462 per unit at rated kVA Direct Axis Transient Short Circuit Time Constant = 0.654 seconds at 75 degrees Celsius The initial or subtransient value of generator phase current resulting from a fault at the generator terminals:

AC Subtransient Amps =

1600 Maximum DC Component Amps =

2260 Maximum Total RMS Amps =

2770 For calculating the maximum fault current at the 4160 volt switchgear, 1600

amps is assumed; 2770 amps is assumed to evaluate the close and latch breaker ratings.

c) Motors:

The motor contribution varies depending on the plant condition and configuration. The current during normal operating conditions is as low as 650A.

The maximum motor contribution is as high as 9000A.

The total short circuit current for Bus 1 H is approximately 25,078A during normal operating conditions; this increases to 26,678A with the EOG on the bus.

The maximum short circuit current is 33,235A; this occurs with a Unit 1 accident coincident with a Unit 2 trip.

2. Switchgear MVA rating:

The 4160 volt 5HK250 switchgear circuit breakers are rated for 250MVA.

This equates to a 33,541 Amps Symmetrical Interrupting rating at the approximate operating voltage of 4300V. The Close and Latch Rating is 80,000 amps RMS.

3. 4160 V breaker tripping time:

The average tripping time between energizing of the trip coil and parting of arcing contacts is 1. 5 cycles.

4. Total time delay:

a) Relay time:

0.25 - 1 cycle b) Lockout relay time:

3 cycles (H FA relay)

5. Breaker interrupting time:

_The interrupting time between energizing the trip coil and complete interruption is 5 cycles.

6. Maximum asymmetrical short circuit current:

The asymmetrical breaker current interrupting capability is 1.2 times the symmetrical rating: Because the X/R ratio for the safety-related buses is low, i.e., 10-12, the available three-phase short circuit current requires no additional multiplication factor.

7. Cable:

All motors supplied from the safety-related buses are fed with #1 or #2 conductors.

a) Conductor material copper or aluminum:

b). Cable operating temperature:

c) Cable short circuit temperature:

2 Aluminum 90 degrees Celsius 250 degrees Celsius

d) Type of insulation:

All have Crosslinked Polyethylene (PEI) insulation. Note that two have neoprene jackets, the remainder have aluminum or galvanized interlocked armor.

8. Calculation to determine the minimum size cable for 4160 volt system:

No calculation has been identified, therefore, we have concluded that one does not exist. IEEE Std. 242-1986 was utilized to evaluate this condition during the recent inspection; however, Surry is not committed to this standard.

No design basis standard for Surry has been identified which specifically requires this evaluation, and therefore, we conclude that none applied at the time Surry was licensed.

From IEEE Std. 242, Figure 152 is used to determine a temperature correction factor. For 90°C initial temperature and 250°C maximum short circuit temperature, K1 = 0.925. The maximum available fault current is 33,235A. 33,235 x 0.925 =

30742A. Based on Figure 151, the minimum conductor for a 5-cycle circuit breaker is 250 MCM AL. The fault current available during normal plant operating conditions*

is 25,078A.

25,078 x 0.925 = 23,197 A. Based on Figure 151, the minimum conductor for a 5-cycle circuit breaker is 3/0 AL.

50-280/98-201-04, Motor Thermal Overload for 1-SI-P-1 B Pump

9. 1-SI-P-18 motor information: This motor was obtained from another plant (Shearon Harris) after a motor failure was experienced at Surry.

. a) Nameplate Data:

300HP, 460V, 1.15 service factor, 1763 full load RPM, 338A full load current, 2005A locked rotor current.

b) Motor test report:

The motor was rated to start its intended load at the Shearon Harris station in less than 2 seconds at 75% terminal voltage.

However, the Surry motor application services a smaller pump than the pump used in the Harris application.

The motor torque curve is well above the pump curve and can accelerate the pump even below 70% voltage.

c) Motor thermal curve:

A thermal limit curve was provided with the pump. Based on the motor outline drawing, the maximum allowable stall time assuming an 80 degrees Celsius 3

. '\\>

initial temperature is 10 seconds, and from a 30 degrees Celsius initial temperature is 15 seconds.

d) Motor time current curve:

The motor will accelerate its original load (i.e., the Harris plant application) in less than 2 seconds at 75 percent voltage.

However, the motor load at Surry is smaller than the originally intended load for the Harris plant application. No current curve exists for the specific Surry application.

10. Breaker coordination curve:

The available data for the 300 HP 1-SI-P-1 B and the three 250 HP pumps are attached. The curves for the 300 HP motor show, based on the 80 degree Celsius thermal limit curve provided, that the circuit breaker does* not protect the motor for the full range of current. However, this is acceptable in order to ensure that the motor is allowed to start. Based on the limitations of the protective device, if the protection is set faster, it might inhibit the start. No thermal limit curve is available for the other three motors.

11. 1-SI-P-1 B Pump Maximum Brake Horsepower and Load Current:

The expected maximum brake horsepower for 1-SI-P-1 B for the Surry application is 240. Based on motor power factor, efficiency, etc., the expected load current is 27 4 amps at 460 V.

4

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No. _______________________ _

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