ML20213G083
| ML20213G083 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek, South Texas, 05000000 |
| Issue date: | 05/08/1987 |
| From: | Wisenburg M HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20213G085 | List: |
| References | |
| ST-HL-AE-2172, NUDOCS 8705180114 | |
| Download: ML20213G083 (11) | |
Text
The Light NE f Ilouston 1.ighting & Power P.O. Box 1700 llouston. Texas 77001 (713) 228-9211 May 8, 1987 ST-HL-AE-2172 File No.: G9.15, J5, J28 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Information Concerning Struthers-Dunn Relays and Magnetic Current Transformers Used as Isolation Devices
References:
A.
Additional Information Concerning Electrical Isolation Devices and Class lE/Non-Class 1E Control Circuit Interfaces, M.R. Wisenburg, HL&P, Letter to the NRC; ST-HL-AE-1917; Dated February 14, 1987.
B.
Summary of Meetings and Audits on Electrical, Instrumentation and Control Systems, Equipment Qualification, SPDS, and Control Room Design Review Subj ec t, N.P. Kadambi, NRC Letter to HL&P; ST-AE-HL-91194, Dated March 12, 1987.
C.
Responses to I&C Audit Items, M.R. Wisenburg, HL&P, Letter to the NRC; ST-HL-AE-1943; Dated March 13, 1987.
Usage of Struthers-Dunn Relays and Magnetics Current Transformers as isolation devices was identified during the Instrumentation and Control Systems audit in January 1987. These devices are discussed in References A, B, & C.
Reference B requested responses to the standard isolation question for these devices. The information requested is provided in the attachments to this letter.
This information is expected to resolve any remaining NRC concerns relative to isolation devices.
l Y
C705180114 870508 PDR ADOCK 05000498
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A PDR
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Houston Lighting 8e Power Company -
ST-HL-AE-2172 File No.: G9.15, J5, J28 Page 2 i
If you should have any questions on this matter, please contact Mr.
M. E. Powell at (713) 993-1328.
eO M. R. Wisebburg Manager,_&gineeri and icensing THC/yd Attachments:
1.
Responses to NRC Isolator Question for Struthers-Dunn Relays 2.
Responses to NRC Isolator Question'for Magnetics Current Trans formers 3.
Struthers-Dunn memo, dated May 4, 1987, ST-XX-YB-535 4.
Wyle Laboratories Test Report No. 47950-01, dated September 26, 1985 5.
Elementary Diagram Standby Diesel Generators No. 11, 12, and 13 Emergency Control and Instrumentation; Bechtel Drawing 9E-DG04-01 6.
Single Line Diagram 125 VDC Class lE Distribution Panels PLO39A, PLO39B, PLO39C, PLO40A; Bechtel Drawing 9E-DJAE-01 7.
Elementary Diagram Steam Generator Preheater Bypass Valves FV-7189, FV-7190, FV-7191, and FV-7192; Bechtel Drawing 9E-FW29-02 8.
Elementary Diagram Steam Generator Bypass Valves FV-7189, FV-7190, FV-7191, and FV-7192; Bechtel Drawing 9E-FW29-01 9.
Magnetics Current Transformer Circuit Sketch
ST-HL-AE-2172 File No.
G9.15, J5, J28 Ilouston Lighting & Power Company Page 3 cc:
Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Drive, Suite 1000 P.O. Box 1088 Arlington, TX 76011 Austin, TX 78767-8814
- N. Prasad Kadambi, Project Manager A. von Rosenberg/M.T. Hardt U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771 Bethesda, MD 20814 San Antonio, TX 78296
- Robert L. Perch, Project Manager Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue 1717 H Street Bethesda, MD 20814 Washington, DC 20555 Dan R. Carpenter Senior Resident Inspector / Operations c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 Claude E. Johnson Senior Resident Inspector / Construction c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 M.D. Schwarz, Jr., Esquire Baker & Botts One Shell Plaza Houston, TX 77002 J.R. Newman, Esquire Newman & Holtzinger, P.C.
1615 L Street, N.W.
Washington, DC 20036 T.V. Shockley/R.L. Range Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403
- With Attachments 1 through 9; all others with Attachments 1 and 2 only.
Revised 2/3/87
ST-HL-AE-2172 s
Responses to NRC Isolator Question For Struthers-Dunn Relays a.
Question: For each type.of device used to accomplish electrical isolation at STP describe the specific testing performed to demonstrate that the device is acceptable for its application (s). This description should include elementary diagrams where necessary
-to indicate the test configuration and how the maximum credible faults were applied to the devices.
Response: The Struthers-Dunn relays used as isolators'at STP isolate Class 1E Control Circuits from non-Class 1E Control Circuits.
These relays (Model 219 X RX242NE) are rated for 125 VDC service.
Public Service Electric and Gas Company (PSE&G) has tested Struthers-Dunn Relays (Model 219xBXP,120V ac service) for
-the Hope Creek Generating Station as Isolation Devices. The Test is documented in the Wyle Laboratories Test Report provided in Attachment 4, Correspondence with Struthers-Dunn indicates that the 125 V DC relays use the same material as the 120 VAC relays, however the DC relay model (used at STP) is built to higher quality standards and has incorporated an improved coil design'(Attachment 3).
Therefore; the Wyle test report applies to the Struthers-Dunn relays used as isolation devices at STP.
i l
The dielectric strength and surge withstand capability test l
reports were previously transmitted by Reference A.
Specific applications at STP included a contact from the diesel generator reset switch (Attachments 5 & 6) and isolation of non-Class lE valve position indicating lights from the steam generator preheater bypass valves (Attachments 7 & 8).
o l
- b.
Question: Data to verify that the maximum credible faults applied during l
the test were the maximum voltage / current which the device j
could be exposed, and define how the maximum voltage / current was determined.
Response: A review of cabling installed in the same raceway as the non-Class lE cables connected to the Struthers-Dunn relays indicates that 144 VDC and 35 A are the maximum fault conditions. Wyle Lab report (Page fi) shows that these relays were tested as follows:
o 300 VAC (RMS) for 5 minutes o
300-350 AMPS applied through the closed contacts of the isolation relays until an open circuit occurs.
The test voltage /and current values are significantly higher than the maximum fault condition value at STP.
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r ST-HL-AE-2172 Page 2 Responses to NRC Isolator Question For Struthers-Dunn Relays c.
Question: Data to verify that the maximum credible fault was applied to the output of.the device in the transverse mode (between signal and return) and other faults were considered (i.e., open and short circuits).
Response: Sections IV and V of the Wyle Test Report (Attachment 4),
applied'300 VAC across the normally open contacts and 300 A-I across the normally closed contacts. These faults are well above those which are credible at STP. Open circuiting of,the non-Class 1E contacts has no effect on the Class 1E coil side of the relay.
d.
Question: Define the pass / fail acceptance criteria for each type of device.
Response:' Data sheet IV-8 of Attachment 4 defines the acceptance criteria for maximum credible voltage tests as "There shall be no evidence of insulation breakdown or flashover on the Class lE side (coil) with air applied potential of 300 Vrms for 5
[
minutes."
l Data sheet V-12 of Attachment 4 defines the acceptance criteria-L for short circuit current tests as "The integrity of the relay i-coil (Class 1E side) shall be maintained when 350 amperes of current are circulated through the associated relay contact."
e.
Question: Provide a commitment that the isolation devices comply with the environmental qualifications (10CFR50.41) and the seismic qualifications which were the basis for plant licensing.
Response: The isolation devices have been qualified environmentally and seismically and they meet the requirements of IEEE-323-1974,
.IEEE-344-1975 and NUREG 0588, Rev. 1.
The isolation devices are classified as mild environment equipment, Therefore, 10CFR50.49 which addresses only harsh environments does not apply.-
f.
-Question: Provide a description of the measures taken to protect the safety systems from electrical interference (i.e.,
Electrostatic Coupling, EMI, Common Mode and Crosstalk) that may be generated as a result of using the electrical isolators.
Response: For isclation relays used in the Class 1E coil to non-Class 1E contact configuration, no credible fault applied to the contacts can cause interference in the Class 1E coil circuit so long as coil integrity is maintained. Coil integrity was demonstrated'as discussed in item C above. Based on this analysis, no special noise testing is required.
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1 Attcchment 1 ST-HL-AE-2172 Page-3 Responses to NRC Isolator Question For Struthers-Dunn Relays
+.
S g.
Question: Provide information to verify that the Class lE isolators are u
powered from a Class 1E power source.
Response: The Class 1E coil side of these isolation relays is powered from the Class 1E power, as shown in Attachments 5, 6, and 7.
- 1..
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ST-HL-AE-2172 Page 1 Responses to NRC Isolator Question For Struthers-Dunn Relays i-a.
Question: For each type of device used to' accomplish electrical isolation at STP describe the specific testing performed to demonstrate that the device is acceptable for its application (s). This description should include elementary-diagrams where necessary to indicate the test configuration and how the maximum credible faults were-applied to the devices.
Response: Although testing has not been performed to prove that the isolation current transformer is acceptable for its application, the following engineering analysis addresses the impact on Class lE equipment of postulated maximum credible '
faults on the non-Class lE side of the isolation current transformer.
The isolation current transformer, used for non-Class lE diesel generator metering, is located within one of the main control panels. Wiring on the non-Class lE side of the isolation current transformer is located entirely within the main control panels.
(Refer to the sketch.provided in Attachment 9).
Maximum voltages on other wiring within the main control panel, where the isolation current transformers are located, do not exceed 208 VAC and 125 VDC, at a maximum sustained current of 3A.
Therefore, the maximum credible fault voltage that could be impressed on the non-Class 1E side of the isolation current transformer is 208 VAC.
If the isolation current transformer should fail, due to the application of 208 VAC or 125 VDC to
+
its secondary side, at worst, the primary side would be open circuited. This is irrespective of the fault current applied.
The primary circuit is connected to the Class lE current transformer.
These Class lE current transformers do not supply any other Class 1E loads.
4 If it is assumed that an overvoltage condition, caused by the open circuited Class 1E current transformer, causes cable 4
insulation failure, the resultant conductor in the faulted cable assembly. This current would immediately cause collapsing of the CT field, eliminating the overvoltage i
condition. Based on the CT sizes used, the CT would not deliver more than 5 amps under normal conditions (primary conductor unfaulted). The #10 conductor used in the CT circuit is capable of carrying in excess of 5 amps continuously; a short circuit in the output will not damage the CT.
Therefore, faults on the non-Class 1E side of the isolation current transformer will not affect the operation of the Class 1E diesel generator or Class lE 4 kv switchgear.
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O ST-HL-AE-2172 j
Page 2 Responses to NRC Isolator Question For Struthers-Dunn Relays b.
Question: Data to verify that the maximum credible faults applied during the test were the maximum voltage / current which the device could be exposed, and define how the maximum voltage / current was determined.
Response: Refer to the analysis provided in item a above.
c.
Question: Data to verify that the maximum credible fault was applied to the output of the device in the transverse mode (between signal and return) and other faults were considered (i.e., open and short circuits).
Response: Refer to the analysis provided in item a above. A short circuit, open circuit, or credible hot short applied to the non-Class lE output of the isolation CT will not degrade the Class lE bus, d.
Question: Define the pass / fail acceptance criteria for each type of device.
Response: The acceptance criteria of the analysis provided for item a above is that no credible fault cause degradation of the Class lE bus.
e.
Question: Provide a commitment that the isolation devices comply with the environmental qualifications (10CER50.49) and the saismic qualifications which were the basis for plant licensing.
Response: (Same as Attachment 1, Item e) The isolation devices have been qualified environmentally and seismically and they meet the requirements of IEEE-323-1974, IEEE-344-1975 and NUREG 0588, Rev. 1.
The isolation devices are classified as mild environment equipment, Therefo e, 10CFR50.49 which addresses only harsh environments does not apply.
f.
Question: Provide a description of the measures taken to protect the safety systems from electrical interference (i.e.,
Electrostatic Coupling, EMI, Common Mode and Crosstalk) that may be generated as a result of using the electrical isolators.
Response: It is not credible that electrical interference imposed on the non-Class lE secondary of the isolation current transformer could degrade the Class lE bus.
No special measures are necessary.
g.
Question: Provide information to verify that the Class 1E isolators are powered from a Class lE power source.
Response: No external power is required for this type of current transformer circuit.
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