ML20138C103

Analysis of Electrical Separation Criteria for Seabrook Station

ML20138C103
Person / Time
Site:	Seabrook
Issue date:	03/24/1986
From:	Jamison R PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:
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ML20138C100	List: ML20138C095 ML20138C103
References
NUDOCS 8604020225
Download: ML20138C103 (49)

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0 ANALYSIS OF ELECTRICAL SEPARATION CRITERIA FOR SEABROOK STATION i

Prepared By: c i U

E 3f 34f3d 3 (Date)

Approved By: 3 ~') 3!)'/!k'I (Date) i A O 3 t

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TABLE OF CONTENTS Page I. ABSTRACT.......................................................... 1 II. BACKGROUND........................................................ 2 III. TEST PROCRAM DESCRIPTION.......................................... 5 A. General Description.................. ....................... 5 B. Fault Current Levels......................................... 6 IV. EVALUATION OF TEST RESULTS AND REVISED SEPARATION CRITERIA'........ 8 A. Introductiom................................................. 8 B. Internal Panel Separation Criteria........................... 8 C. Conduit-to-Conduit Separation Criteria....................... 9 D. Conduit-to-Cable Tray Separation Criteria.................... 11 E. ALS-to-ALS Separation Criteria............................... 14 F. ALS-to-Conduit / Cable Tray separation criteria................ 15 V. REFERENCES........................................................ 16 APPENDIX A - Tables and Figures APPENDIX B - Fault Cable Currents APPENDIX C - Power Cable Ignition Analysis

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, l I. ABSTRACT

. This analysis describes a test program which justifies separation distances less than the standard criteria given in IEEE 384-1974 and 4 Seabrook FSAR Appendix 8A.

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s II. BACKGROUND For cable and raceway separation, Seabrook Station has committed to meeting the requirements of FSAR Appendix 8A, IEEE Standard 384-1974, and Regulatory Guide 1.75. Revision 2. These documents provide two options for establishing separation criteria. The first option inrolves performing an analysis based on tests to establish separation criteria (Sections 5.1.1.2 and 5.6 of 384/8A). The second option provides standard separation criteria for use in different areas of the plant if lesser distances are not established by the first option (Sections 5.1.1.3, 5.1.3, 5.1.4, and 5.6 of 384/8A). For internal panel separation, Section 4.3.3 of IEEE 420-1982 repeats the requirements of Section 5.6 of IEEE 384 and Appendix 8A by providing two options, standard criteria or analysis / test.

The separation criteria established in the FSAR for the Seabrook design was based on the second option of st'andard criteria as follows:

Cable Tray to Cable Tray - Cable Spreading Room: 1-foot horizontal and 3-foot vertical or provide barriers / enclosed raceways with a minimum separation of 1 inch.

- General Plant Area: 3-foot horizontal and 5-foot vertical or provide barriers / enclosed raceways with a minimum separation of 1 inch.

Conduit to Conduit - All~ plant areas: 1-inch minimum separation.

Internal Panel - Six-inch air separation or provide barriers.

As Seabrook construction proceeded, the following concerns were identified with the FSAR separation criteria:

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1) In the Main Control Board (MCB), it was becoming difficult to install equipment with 6-inch air separation or to install barriers because of the confined area of the MCB. In addition, some barriers were being questioned because they did not provide a tight fit, i.e., there was a small gap (<1/4 inch) through which measurements were being made with findings of less than 6-inch separation between opposite train wires.

2) During installation, minor deviations to the 1-inch conduit-to-conduit separation criteria may occur, for example, 7/8 inch versus 1 inch. Although these deviations are minor, they have to be fixed in order to comply with the FSAR commitments.

These fixes can be difficult and costly.

3) The regulatory standards do not provide clear guidelines on conduit-to-cable tray separation criteria. Our interpretation has been that one inch separation is adequate. An alternate interpestation of the standards could be to have tray covers top and bottom to enclose a tray anywhere a conduit was less than the standard criteria values (l'H-3'V or 3'H-5'V) from a tray.

4) Aluminum Sheath (ALS) lighting cable is used for most lighting circuits at Seabcook. Similar to Item 3, there is no guidance in standards for ALS. In addition, it is not clear if the aluminum sheath on ALS can be considered a barrier.

As mentioned above, these concerns can be difficult and expensive to resolve, and for Items 3 and 4, it was not even clear what resolution would be acceptable. Based.on this, it was decided to perform a test program which would be analyzed as permitted by the regulatory standards (see Option 1 above) to develop new minimum separation criteria which would resolve the above-described concerns. This test program consisted of various configurations of cables and raceways and an internal panel setup. Based on discussions with other utilities, similar test programs have been successfully performed with acceptable results showing that the standard criteria are very conservative and that separation l

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4 distances less than the standard. criteria given in the standards are

1. justifiable. The test program and results are described in the

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s III. TEST PROGRAM DESCRIPTION A. General Description The test program consisted of various configurations of cable and raceway and an internal panel setup where a cable was subjected to a fault current with temperature monitoring and functional tests to evaluate the effect of the faulted cable on other cables (target cables). These setups were specifically selected to address the four concerns described in Section II. The proximity of the target cables to the faulted cables was selected to represent the different raceway arrangements at Seabrook. The internal panel configuration represented the Main Control Board. The various fault cables, target cables, raceways, etc., used in the test program were of the same type used at Seabrook.

The fault current was applied to the fault cable until it open circuited, short circuited, or the temperature stabilized. If the cable shorted (conductor-to-conductor), the current was increased to a short circuit current level (actually limited by test equipment capacity) until the cable open circuited. The fault current levels used are described in Section III.B.

The target cables were energized throughout the tests. Acceptance criteria for the target cables was based on insulation resistance and hipot functional tests and on maintaining continuity throughout the test. Also evaluated were maximum temperatures and evidence of physical damage.

Thermocouples were mounted at various points on the fault cables, target cables, and raceways and in arrays at various heights to monitor temperature. Fault cable current, target cable voltages and currents, and temperatures were recorded.

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The fault and target cables were oriented with the fault cable below the target cables. This orientation was selected as having the potential for worst case heat interaction. This concept was verified in the Configuration 4 Tests (Section IV.F) where there was a target cable above and below the fault cable and the upper target cable was hotter than the lower target cable.

A power cable was used as the fault cable for the tests which had the fault cable in a cable tray or conduit because the larger size of the power cables had the potential for greater heat generation under faulted conditions as compared to control or instrumentation cables. .Five sizes of power cable were tested (3/C-8 AWG, 3/C-2 AWG, 3/C-2/0 AWG, 250 MCM triplex, and 500 MCM triplex) to determine the worst case cable in terms of heat generation. The 3/C-2 AWG and 500 MCM triplex were selected as worst case and were used in subsequent tests.

A brief description of each test setup and results and an analysis of the results to establish revised separation criteria for Seabrook are provided'in Section IV.

B. Fault Current Levels Fault current levels for the tests were developed based on an evaluation of the electrical system considering a combination of loads failing and protective devices not operating to produce a worst case, conservative, fault current. The fault current levels used for the different tests are given in Table 1.

The power cable fault current was based on the locked rotor current of the largest motor that a particular cable was sized to supply at Seabrook. In addition, the primary motor protective device was assumed to fail such that the locked rotor current would flow until the cable open circuited, short circuited, or the temperature stabilized.

The ALS lighting cable fault current was based on failure of the primary protective device with the current selected at a value slightly below the long time setting of the backup protective device so that the backup device would not operate. Actually, the first two protective devices (lighting panel circuit breakers) were assumed to fall since they were not qualified. The backup protective device used to select the current level was the qualified motor control center feeder breaker.

For the internal panel test, the primary protective device was also assumed to fail. However, a screening type test was performed to evaluate separation. This involved initially applying a 70A~ fault current until the temperature stabilized. The fault current was then increased in 15A increments with the temperature being allowed to stabilize at each increment until a current was reached where the wire open circuited. A second test was then conducted using the l current which caused the wire to open circuit in the first test.

The assumption of the primary protective device failure is very conservative since this really represents a double failure, i.e.,

the load and protective device. If this assumption is not used, the i

protective device would be operated by the fault current before cable damage could pecur and therefore, there could be no detrimental interaction between cables.

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4 IV. EVALUATION OF TEST RESULTS AND REVISED SEPARATION CRITERIA A. Introduction The following sections summarize the test program results which are documented in Wyle Test Report No. 47966-02 (Reference (a)) and analyze these results to develop revised separation criteria to resolve the concerns described in Section II. The revised separation criteria are given in Table 2.

B. Internal Panel Separation Criteria i

The Internal Panel Separation Test (IPST) was conducted to evaluate separation within the Main Control Board (MCB). As shown~in Figure 1, the setup consisted of: (a) typical MCB wires separated vertically by a 1-inch air gap with no interposing barriers, and (b) typical MCB wires in contact with opposite sides of a metal barrier. The fault current was applied to the bottom set of wires with the top set of wires monitored as a target. As explained in Section III.B. two tests were conducted. The target wires from the first test were reused for the second test since they showed no apparent damage from the first test.

During application of the fault current, the fault wire open circuited in both tests without ignition. The maximum target cable temperatures occurred in the second test with 287 F across the 1-inch air gap and 328 F across the metal barrier. The target wires conducted current throughout both tests. The post-test insulation resistance and hipot functional tests were acceptable.

No physical damage was observed on the target wires after both tests. We considered these test results acceptable.

The results of these tests demonstrate that 1-inch free air and "O" inch (in contact) across a barrier is an acceptable separation

criteria for the MCB. Margin is included in this criteria because the target wire temperatures were sufficiently below acceptable levels and because the same target wires were undamaged through two tests.

The internal panel test was set up using parallel runs of wire (both free air and in contact with the barrier) which is worst case in l terms of heat interaction. Most field installations involve more of l a crossing situation, not parallel runs, which would result in less l heat transfer and add more conservatism and margin for actual field l installations.

l The tested barrier was metal. Some nonmetallic (Glastic) barriers l have 'been used in the Main Control Board. Metal barriers were tested because they would conduct heat more readily which makes them worst case in terms of potential degradation of target wires. The separation criteria will apply to both metal and nonmetallic barriors.

Although a lesser value could probably be used for horizontal separation, the same criteria will be used for both horizontal and vertical separation to simplify implementation.

C. Conduit-to-Conduit Separation Criteria Three tests were conducted to evaluate condult-to-conduit separation. The test setups are shown in Figures 2, 3, and 4 and were designated Configuration 2. Test 1 (C2-TI), Configuration 2, Test 2 (C2-T2), and Configuration 1 Test 2 (Cl-T2).

Test C2-T1 (Figure 2) used a 500 MCM triplex fault cable installed in a rigid conduit with a rigid and flexible conduit containing target cables mounted 1/4-inch vertically above and parallel with the conduit containing the fault cable. Fault current was applied to the fault cable until it open circuited in 25.2 minutes. The fault cable did ignite. The high temperatures resulting from the

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o fault cable ignition damaged the target cables in the rigid and flexible conduits. However, as explained in Appendix C, this fault cable ignition resulted from the overly conservative assumption which applied fault current until the fault cable open circuited, short circuited, or temperature stabilized. Using a more realistic assumption, the analysis in Appendix C demonstrated that actual fault current duration in the field would be such that cable ignition would not occur. Therefore, the results of this test will be evaluated based on data measured at the time (5.8 minutes) defined in Appendix C before the fault cable ignited.

At this time, the maximum temperature on the target cables was 135 F and they were conducting current. Although insulation resistance and hipot test measurements were not made at this time, it is our judgement that the results would have been acceptable since there are other tests (see Tests C2-T2 and Cl-T2 below) where the same type of target cables experienced higher temperatures (142 F and 272 F, respectively) and passed functional tests with no physical damage. Therefore, based on the analysis in Appendix C, we considered these test results acceptable.

Test C2-T2 (Figure 2) used a 3/C-2 AWG fault cable installed in a flexible conduit with a rigid and flexible conduit containing target cables mounted 1/4-inch vertically above and parallel with the conduit containing the fault cable. Fault current was applied to the fault cable until it open circuited at 27.3 minutes. The fault cable did not ignite. The maximum temperature on the target cables was 142 F. The target cables conducted current throughout the test. The post-test insulation resistance and hipot functional tests were acceptable. No physical dam &ge was observed on the target cables. We considered these test results acceptable.

Part of Test Cl-T2 (Figures 3 and 4) involvsa a conduit-to-conduit test where a rigid and flexible conduit containing target cables were mounted 1/4-inch vertically above and at about a 45 crossing angle with the conduit containing the fault cable. The fault cable 9

was a 500 MCM triplex cable. Fault current was applied until the fault and target cable temperatures stabilized at 91.5 minutes and the test was stopped. The fault cable did ignite but had no degrading effect on the target cables in the rigid and flexible conduits. The maximum temperature on the target cables was 272 F. The target cables conducted current throughout the test.

The post-test insulation resistance and hipot functional tests were acceptable. No physical damage was observed on the target cables.

We considered these test results acceptable.

These test results demonstrated that 1/4-inch is acceptable for a conduit-to-conduit separation criteria. Margin is included in this criteria because the target cable temperatures were sufficiently below acceptable levels.

Tests C2-Tl and C2-T2 were setup with parallel runs of conduit which is worst case in terms of heat interaction. Most field installations involve crossing situations which would result in less heat transfer and add more conservatism and margin for actual field installation.

Although a lesser value could probably be used for horizontal separation, the same 1/4-inch criteria will be used for both horizontal and vertical separation to simplify implementation.

D. Cable Tray-to-Conduit Separation Criteria Three tests were conducted to evaluate conduit-to-cable tray separation. The test setups are shown in Figures 3, 4, 5, and 6 and

, were designated Configuration 1-Test 1 (Cl-TI), -Test 1A (Cl-TIA),

and -Test 2 (Cl-T2).

Test Cl-T1 (Figure 5) used a 3/C-2 AWG fault cable installed in a filled cable tray with a rigid conduit and wireway containing target cables mounted 1/4 inch above and parallel with the cable tray side l rails. The fault cable was the top centerline cable cradled in four

e same size cables carrying rated current. Fault current was applied to the fault cable until it short circuited in 26.9 minutes. A short circuit current was then applied and the cable open circuited in two seconds. The fault cable did not ignite. The maximum temperature on the target cables was 217.6 F. The target cables conducted current throughout the test. The. post-test insulation resistance and hipot functional tescs were acceptable. No physical damage was observed on the target cables. We considered these test results acceptable.

Test Cl-TIA (Figure 6) used the same setup as Test Cl-T1 except that the fault cable was a 500 MCM triplex cable installed in the cable tray with one layer of cable spaced at a nominal 1/4 cable diameter spacing. Fault current was applied to fault cable until it open e.rcuited in 61 minutes. The fault cable did ignite. The high temperatures resulting from the fault cable ignition damaged the target cables in the conduit and wireway. However, as explained in Appendix C, this fault cable ignition resulted from the overly conservative assumption which applied fault current until the fault cable open circuited, short circuited, or temperatures stabilized.

Using a more realistic assumption, the analysis in Appendix C demonstrated that actual fault current duration in the field would be such that cable ignition would not occur. Therefore, the results of this test will be evaluated based on data measured at the time (8.4 minutes) defined in Appendix C before the cable ignited.

At this time, the maximum temperature on the target cables was 105 F and they were conducting current. Although insulation resistance and hipot test measurements were not made at this time, it is our judgement that the results would have been acceptable since there are other tests (see Tests C2-T2 and Cl-T2,Section IV.C) where the same type of target cables experienced higher temperatures (142 F and 272 F,.respectively) and passed functional tests with no physical damage. Therefore, based on the analysis in Appendix C, we considered these test results acceptable.

Test Cl-T2 (Figures 3 and 4) used a 500 MCM triplex cable installed in a rigid conduit mounted 1/2 inch below and parallel with the cable tray side rails with target cables in the tray directly above the conduit and in a wireway mounted 1/2 inch horizontal from the conduit. Fault current was applied until the fault cable temperature stabilized at 91.5 minutes and the test was stopped.

The fault cable did ignite but had no degrading effect on the target cables. The maximum temperature on the target cables was 414 F.

The target cables conducted current throughout the test. The post-test insulation resistance and hipot functional tests were acceptable. No physical damage was observed on the target cables.

Although this high temperature of 414 F did not damage the target' cable, we feel it was high enough to require further evaluation. As explained above for Test Cl-TIA, the analysis in Appendix C demonstrated that actual fault current duration in the field would be such that cable ignition would not occur. At the time (8.4 minutes) given in Appendix C, the maximum temperature on the target cables was 120 F which is very acceptable and well below 414 F.

Although insulation resistance and hipot test measurements were not made at this time, they would have been acceptable since they were acceptable at the end of the test as stated above. We considered these test results acceptable.

The results of Tests Cl-T1 and Cl-TIA demonstrated that 1/4 inch'is an acceptable separation criteria for conduits to cable trays with the conduit above the cable. tray. The results of Test Cl-T2 demonstrate that 1/2 inch is an acceptable separation criteria for conduits to cable trays with the conduit below the cable tray. To simplify implementation of the criteria, we have selected 1/2 inch as the separation criteria for conduits to cable trays for conduits both above and below the cable tray. Margin is included in this criteria because the target cable temperatures were sufficiently below acceptable levels.

The Configuration 1 Tests were setup with parallel trays and conduits which is worst case in terms of heat interaction. Most field installations involve crossing situations which would result in less heat transfer and add more conservatism and margin for field installations.

Although a lesser value could probably be used for horizontal separation, the same 1/2-inch criteria will be used for both horizontal and vertical separation to' simplify implementation.

E. ALS-to-Conduit / Tray Separation Criteria The Configuration 3 Test was conducted to evaluate Aluminum Sheath (ALS) lighting cable separation to cable trays and conduits. As shown in Figu'.e 7, the test setup used a 3/C-4 AWG ALS fault cable mounted 1/4 inch below and parallel with a conduit and cable tray both containing target cables.

During application of the fault current, the ALS fault cable open circuited in 5.3 minutes. The ALS fault cable ignited out both ends and at two' points under the conduit and cable tray but there was no degradation of the target cables. The maximum temperature on the target cable was 270 F. The target cables conducted current throughout the test. The post-test insulation resistance and hipot functional tests were acceptable. No physical damage was observed on the target cables. We considered these test results acceptable.

Based on these test results, we have selected a 1/4-inch separation criteria for ALS to cable tray and conduit / wireway separation.

Margin is included in this criteria because the target cable temperatures were sufficiently below acceptable levels.

The Configuration 3 Test was setup with parallel runs of ALS and cable trays and conduits which is worst case in terms of heat interaction. Most field installations involve crossing situations which would result in less heat transfer and add more conservatism and margin for actual field installations.

Although a lesser value could probably be used for horizontal separation, the same 1/4-inch criteria will be used for both ho'rtzuutal and vertical separation to simplify implementation.

F. ALS-to-ALS Separation Criteria The Configuration 4 Test was conducted to evaluate ALS-to-ALS cable separation. Js shown in Figure 8, the test setup used a vertical group of three ALS cables. The fault ALS cable was in the middle with the target AL cables mounted vertically above and below and in contact with the ft 'x ALS cable.

Fault current was applied until the ALS fault cable open circuited in 2.6 minutes. The fault ALS cable ignited out both ends but there was no degradation of the target ALS cables. The maximum temperature was 526 F on the top ALS target cable and 226 F on the bottom ALS target cable. The target cables conducted current throughout the test. The post-test insulation resistance and hipot functional tests were acceptable. No physical damage was observed on the target cables. Although the 526 F temperature appears high, it is acceptable because the lighting system which uses ALS cable is nonsafety related. Therefore, any potential degradation the high temperature could cause would not be a problem unless it was severe enough to cause an actual circuit interconnection between the fault and target cable circuits which obviously did not occur in this test. We considered these test results acceptable.

Based on these results, we have selected a "0"-inch (in contact) separation criteria for ALS-to-ALS cables. Margin is included in this criteria because the target cable temperatures were-sufficiently below the melting point of the aluminum sheath (1,220 F) where the sheath would have to melt to cause a direct interconnection.

V. REFERENCES (a) Wyle Test Report No. 47966-02, dated January 24, 1986.

(b) Yankee Atomic Elec'ric t Calculation No. SBC-134, " Determination of 460 Volt Motor Pigtail Melting Times," dated March 24, 1986.'

e APPENDIX A TABLES AND FIGURES w--- -- - --,r w-, - '-

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TABLE 1 Fault Current Levels Test Current Level (amperes)

Internal Panels Test 1 70, 85, 100, 115, 130 Test 2 130 Power Cables 3/C-8 AWG 193 3/C-2 AWG 465 3/C-2/0 AWG 887 250 MCM Triplex 1,716 500 MCM Triplex 1,760 , 2,116 ALS Configuration 3 600 Configuration 4 440 Notes: (1) 2,116A represents the locked rotor current of the largest motor

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supplied by 500 MCM triplex cable and was used for the power cable screening test and Test C2-T1. 1,760A represents the long time setpoint of_the backup protective device and was used for Tests Cl-T2 and Cl-TIA for comparison to 2,116A. See Appendix B for further explanation.

(2) 440A was selected to evaluate effects of a lower current on ALS.

See Appendix B for further explanation.

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TABLE 2 Seabrook Electrical Separation Criteria as Established by Testing New Criteria Horizontal Vertical Conduit-to-Cable Tray (1) 1/ 2 1/2" Conduit-to-Conduit (1) 1/4" 1/4" ALS-to-Cable Tray / Conduit (1) 1/4" 1/4"

, ALS-to-ALS In In Contact Contact Internal Panel - Main Control Board 1" free air 1" free air space or in space or.in contact with contact with opposite opposite sides of a sides of a barrier barrier Notes: (1) Conduit includes rigid conduit, flexible conduit, and wireway.

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APPENDIX B FAULT CABLE CURRENTS gw . - - w., -

APPENDIX B Fault Cable Current As briefly explained in Section III.B. fault current levels for the test program were developed based on an evaluation of the electrical system considering a combination of loads failing and protective devices not operating to produce a worst case, conservative, fault current. Based on previous test lab experience, the worst case fault current is typically in the range of four to eight times cable rated current. This represents an overload current level. At current higher than this, the cables tend to open too quickly to detect potential interaction. For currents lower than this, the fault cables tend to stabilize at acceptable temperatures without opening.

The basis for selectian of the fault current levels for the different tests are described below. . summary of the test current levels is given in Table 1.

1) Power Cable Fault Current For power cables, the most probable type of load failure which would cause a sustained fault current in the overload range described above would be a motor jamming and drawing locked rotor current. Other types of power loads for example, heaters, would tend to fail open or to short circuit instead of an overload condition.

The fault current level for each of the power cables tested'was based on 6.5 times the full load current of the largest motor that the particular cable was sized to supply at Seabrook. The standard multiplier of 6.5 was used instead of the actual motor locked rotor current to make the current levels more generic and to add margin. An additional 10% margin

~

was added to this calculated current. Field cable impedance and voltage drop were not included for conservatism. The following are the resultant currents for each size cable:

B-1 4

Largest Full Load Fault Cable Motor (hp) Current (Amos) Current (Amps) 3/C-8 AWG 20 27 193 3/C-2 AWC 50 65 465 3/C-2/O AWG 100 124 887 250 MCM Triplex 200 240 1,716 500 MCM Triplex 250 296 2,116 Since motor protection is sized to interrupt locked rotor current before motor or field cable damage occurs, it is conservatively assumed that

~

the primary motor protective devices fail to operate with the test current being applied until the fault esble open circuited, short circuited, or temperature stabilizes (see Section III.A). If this assumption is not used, the motor protection would open before the cable could be damaged, and therefore, no detrimental interaction could occur between raceways. In essence, this is assuming a double failure, i.e.,

motor jamming and protective device not operating. The shortest time to ignition from the testing was 7.9 minutes (250 MCM triplex) whereas a typical motor protective device for this size cable would operate in less than 40 seconds at locked rotor current demonstrating the conservatism this assumption adds.

For certain 500 MCM triplex cable applications, the backup protection (unit substation circuit breaker) would also respond to the locked rotor current. For two tests (see Table 1), the 500 MCM triplex cable fault current was the above listed 2,116 amps which includes an assumption that the backup protection does not operate (a third failure). For two other tests (see Table 1), a lower fault :urrent of 1,760 amps was used based on the backup protective device long time setting plus 10%.

~

Except for the longer time to open for the lower current, there appeared to be no significant differences between the test results for the different fault currents.

B-2

In actual field applications, a mot'or would not operate continuously at locked rotor current but would be damaged (motor windings or pigtails would open or short) to the point where the fault current would be interrupted in a relatively short period of time. This would tend to 1

limit fault current duration. For conservatism, it was initially assumed that motor damage would not occur to limit the test current duration, and therefore, fault current was applied until the fault cable open circuited, short circuited, or stabilized. Appendix C discusses why this assumption proved to be overly conservative and how motor damage has been included in the evaluation of the test results.

2) ALS Cable Fault Current The Aluminum Sheath (ALS) lighting cable fault current level was based on failure of the primary protective device with the current selected at a value slightly below the long time setting of the backup protective device so that the backup device does not operate. This method was used since there is no load s'imilar to a motor which could fall and produce overload type currents. This will produce conservative test results since lighting circuits would tend to either fail open resulting in no fault current or short circuit resulting in protective device operation in very short time.

Actually, the first two protective devices (the distribution panel feeder circuit breaker and the main panel circuit breaker) were assumed to fail since they are not qualified. The backup qualified motor control center circuit breaker on the 480 V side of the lighting transformer was assumed to limit the current. This resulted-in a 600-amp test current. For added conservatism, no credit was taken for-the current being limited by circuit or transformer impedance.

The Configuration 4 ALS cable test was conducted at 600 amps. For the Configuration 3 ALS cable test, the current was reduced to 440 amps to evaluate the effects of a lower fault current. The 440 amps represents I l

B-3 ,

l

a current about midway between 600 amps and the test cable rated current. There appeared to be no significant differences between the test results for the different fault currents.

3) Internal Panel Test Current Again, as with ALS cables, there was no load similar to a motor for power cables which could be used for determining fault current for a Main Control Board (MCB) circuit. MCB circuits are either control level (relays, contactors, lights, etc.) or instrument level (recorders, indicators, etc.). Control devices tend to fail open resulting in no fault current or short circuit resulting in protective device operation in a very short time. No worst case current was obvious for the MCB circuits.

A screening-type approach was therefore used. This involved two tests.

The first test used different current levels to determine the current

~

that would open circuit the wire. This started by applying 70 amps until temperature stabilized. The current was then increased in 15-amp increments until the wire open circuited at 130 amps with the temperature being allowed to stabilize at each increment. The second test wan conducted using a fault curreat of.130 amps until the wire open circuited. This current level represents the approximate level which should cause the most potential for temperature interaction.

B-4 l

9 APPENDIX C POWER CABLE IGNITION ANALYSIS

APPENDIX C Power Cable Ignition Analysis As explained in Appendix B, the fault current selected-for power cables was based on the locked' rotor current for the largest motor connected to a particular size cable. This current was applied until the cable open circuited, short circuited, or stabilized. This also assumed that the primary protective device did not operate to interrupt the locked rotor current.

Although this actually in/oires a double failure (locked rotor current and breaker misoperation), this basis wac used because of the conservatism it adds to the test.

However, as noted in Sections IV.C and IV.D. this fault current and duration was sufficient to cause ignition of the 500 MCM triplex cable which resulted in target cable damage. It became obvious that assuming the fault current would flow until the fault cable open circuited, short circuited, or temperature stabilized was overly conservative to the point of negatively effecting the test results.

Af ter evaluating what conditions could limit the time the fault current would flow, we concluded that the most probable conditions would be motor winding damage or motor pigtail melting. The winding failure could be an open circuit which would interrupt the current or a short which would cause the backup chott circuit protection to operate and interrupt the current. Pigtails melting open would directly interrupt the current.

The potential for motor damage was discussed with our primary motor manufacturer. They agreed with our judgement that motor damage would probably occur.before the field cable ignited. However, they did not have any basis from testing to calculate an exact damage time; therefore, this option was not further evaluated.

C-1

To evaluate motor pigtail melting, a comparison was made of motor pigtail size to the field cable size supplying the motor. This comparison showed that'the pigtail cable size was several cable sizes smaller than the field cable indicating that at a given current (locked rotor for this analysis) that the pigtail should open before the field cable opens.

To determine specific motor pigtail melting times, Calculation No. SBC-134,

" Determination of 460 Volt Motor Pigtail Melting Times," (Reference (b)) was performed. This calculation was based on an equation from ICEA Standard-32-382 which is an industry-accepted equation for calculating short circuit withstand for cables. A correction f actor, based on our test results, was applied to the equation to account for heat dissipation which is not included in the base equation since short circuit durations are typically very short. An additional 10% margin was added to the melting times for conservatism.

The results of the calculation are summarized below for the 500 MCM triplex field cable connected to a 250 hp motor. These results show that the motor pigtails will melt and open circuit before the field cable ignites. For smaller motors, the smaller pigtails would melt open even faster than the times given below.

500 MCM Triplex Cable /250 hp Motor Time to Open Motor Pistall Melting Test Current Innition Time Circuit Size Time 1760 A 33 min. >91.5 min ( ' 2 - No. 2 AWG 8.4 min.

1760 A 42 min. >61.5 min.( ' 2 - No. 2 AWG 8.4 min.

2116 A 16.8 min. 25.2 min. ' 2 - No. 2 AWG 5.8 min.

Notes: (1) - Test Cl-T2,Section IV.D. cable temperature stabilized.

(2) Test Cl-T1A,Section IV.D, cable shorted.

(3) Test C2-T1,Section IV.C.

C-2

E SBN-

+

ENCLOSURE 2 FSAR REVISIONS

SB 1 & 2 Amendment 56 FSAR November 1985

.) .

limit switches. Qualification of valve appurtenances, such as motor- l operators, solenoid valves and limit switches, is in accordance with this Regulatory Guide. Details of the qualification of specific motor operators, solenoid valves and limit switches are contained in Reference 15.

For NSSS safety-related motor-operated valves located inside containment, environmental qualification is performed in accordance with IEEE Standards 382-1972 and 323-1974. The qualification program for valve related equipment is described in Reference (9). ll

.54 l Regulatory Guide 1.74 Quality Assurance Terms and Definitions (Rev. O, 2/74)

Endorses ANSI N45.2.10-1973 44 The guidance of this standard has been utilized to provide consistent terms and definitions in the description of the quality assurance program with the following exception, regarding Section 2.0 of the standard: The definitions of " Certificate of Conformance" and " Certificate of Compliance" shall be interchanged to comply with ANSI N45.2.13 (Section 10.2) and the ASME B&PV Code. For further clarification during the Operational Phase, see Section 17.2. , 44 Regulatory Guide 1.75 Physical Independence of Electric (Rev. 2, 9/78) Systems i Theedesign is consistent with the criteria for physical independence of l electrical systems established in " Attachment C" of AEC letter dated December 14, 47 1973 (see FSAR Appendix 8A) and is in general conformance with Regulatory Guide 1.75, Rev. 2, except as follows:

Battery Room Ventilation - four Class lE batteries are located in four seismic 47 Category I structures, and are served by two cross-connected safety-related ventilation systems. Each room can be isolated by fire dampers.

The subject of this regulatory guide is further discussed in Subsections l 8.1.5.3 and 8.3.1.2. 4444 The NSSS and BOP furnished systems comply with the recommendations of Regulatory Guide 1.75, Rev. 2, as discussed in Subsection 7.1.2.2. 44 I NSE9.T 4 1.8-29

SB 1&2 Amendment 44 FSAR February 1982 s a f egua rd s , reactivity, turbine, heat cycle equipment, cooling water, 9

ultimate heat sink and the electrical power distribution systeam. The rear panels of the MCB contain the controls and instrumentation displays for the secondary support systems.

The separation criteria are discussed in Subsection 7.1.2.2a.

The covered wireways, formed from solid or punched sheet steel, and the conduits above or below each board-mounted ,

device, comply with the separation criteria required by IEEE l S tanda rd s . The MCB wiring is color-coded NEC type SIS copper conductor with flame retardant insulation, rated and qualified per IPCEA, UL, or IEEE Standards. Non-metallic components, such as terminal blocks, wire cleats, cable ties, receptacles, indicating light lenses, nameplates, etc. are d' furnished of materials meeting the non-flammability require-ments of UL standards.

j Each component is clearly identified with a distinctively colored permanent tag. Colored nameplates are employed on the exterior surfaces of the MC3 to identify the components function (see Subsection 7.1.2.3).

c. Fire Protection For electrical equipment within the NSSS scope of supply, Westinghouse specifies non-combustible or fire retardant material and conducts 9

vendor supplied specification reviews of this equipment, which includes assurance that materials will not be used which may ignite or explode from an electrical spark, flame, or from heating, or will independently support combustion. These reviews also include assurance of conservative current carrying capacities of all instrument cabinet wiring, which precludes electrical fires resulting from excessive overcurrent (I 2R) losses. For example, wiring used for instrument cabinet construction has teflon or tefzel insulation and is adequately sized based on current carrying capacities set forth by the National Electric Code. In addition, fire retardant paint is used on protection rack or cabinet construction to retard fire or heat propagation from rack to rack. Braided sheathed material is non-combustible.

Sections 8.3.1 and 8.3.2 describe design aspects utilized for BOP electrical equipment in the prevention of fires in cable systems, r including separation between redundant trains and voltage levels, cable material selection and cable sizing.

9 7.1-17

)

i 1

SB 1 & 2 Amendment 56 1 FSAR Noveraber 1985 I testing requirements for diesel generators. Because the FSAR O 1 commits to the type test program of IEEE 387-1977, it is our engineering judgment that the Seabrcok design meets this standard.

IEEE 317-1976:' All major electrical containment penetrations were manufactured to meet the 1976 version of the standard. Some minor electrical penetrations, 3/4" to 1" size which are associated with the personnel air lock, the equipment hatch and the containment recirculation sump isolation valve encapsulation tank, were manufactured to meet the 1972 version. It is our engineering judgment that these minor penetrations meet all the important design requirements necessary to perform their safety fucction. Requirements that may be lacking are in the areas of QA documentation, Service Classification documentation, and definition of certain production tests.

IEEE 384-1974: The Seabrook design meets the requirements of this standard except es noted. For exception to 3ection 5.1.2 on conduit markings, see FSAR Section 8.3.1.4.k. p WEU g k

'IEEE 338-1977: The Seabrook design meets the requirements of this standard.

IEEE 484-1975: The Seabrook design meets the requirements of this standard.

IEEE 450-1975: The Seabrook design meets the requirements of this standard.

8.1.5.3 Regulatory Guides

a. The design of the electric power system is in conformance with the following Regulatory Guides:

RG 1.6 " Independence Between Redundant Standby (Onsite)

(3/10/71) Power Supplies and Between Their Distribution Systems" - Refer to Subsections 8.3.1.2 and 8.3.2.2 RG 1.29 " Seismic Design Classification" - Refer to (Rev 3) Section 3.2 RG 1.30 " Quality Assurance Requirements for the Installation, (8/11/72) Inspection and Testing of Instrumentation and Electric Equipment" - Refer to Section 1.8 RG 1.40 " Qualification Tests of Continuous Duty Motors (3/16/73) Installed Inside the Containment of Water Cooled Nuclear Power Plants" - Refer to Section 3.11 RC 1.41 "Preoperational Testing of Redundant Onsite Electric (3/16/73) Power Systems to Verify Proper Load Group Assignments" O

8.1-4a

SB 1 & 2 Amendment $6 FSAR November 1985

{N

ratio used in speci fying the electrical penetrations is 4. Calculations show that this value is conserva-tively applied because the actual ratio is considerably less than 4. Refer to Subsection 8.3.1.2 RC 1.68 "Preoperational and Initial Startup Test Program for (Rev 2) Water-Cooled Power Reactors" -- Refer to Subsection 14.2.6 for exceptions RG 1.75 " Physical Independence of Electric Systems" (Rev 2)

The design is consistent with the criteria for physical independence of electric systems established in Attach-ment "C" of AEC letter dated December 14, 1973, and is in general conformance'with Regulatory Guide 1.75, except as follows:

Battery Room Ventilation. Although the four Class lE batteries are housed in separate safety 4 class structures, they represent only two redun-dant load groups (see Subsection 8.3.2). Each lead group is served by a separate safety-related ventilation system. There is a cross-tie between the two ventilation systems to allow one system

[/)

to serve both load groups in case the other system is inoperable. Fire dampers are provided

! to isolate each battery room.

A5 For additional information on the four batteries and two redundant load groups, see Subsection 8.3.2.1.a.

Refer to Subsection 8.3.1.2.b.5 for a discussion of

! the onsice ac power system.

! 91 The requirements of position C4, as it relates to cables for the associated circuits, is clarified as follows:

Instrumentation, control and power cables used for the associated circuits will not be covered by the Operational Quality Assurance Program (OQAP). However, programmatic controls will be applied to these items. . The actual implementa-tion of these controls will be defined by the program manuals used to control- specific activi-ties at Seabrook Station. Implementation of these programmatic controls will be verified by Quality Assurance personnel to the extent neces-sary.to insure proper application. For further details on provisions and considerations for

/~' the associated circuits, see FSAR Chapter 8, h} Subsection 8.3.1.4.b.l.d.

TsA 8.1-7

SB 1 & 2 Amendmznt 55 FSAR July 1985 ICEA No.

S-19 1969

" Rubber Insulated Wire and Cable for the Transmission and Distribution of Electrical Energy" Wll ICEA No. " Power Cable Ampacities" P-46-426-1962 ICEA No. "Ampacities - Cable in Open-top Cable Trays" P-54-440 - 1972 ICEA No. " Cross-Linked Thermosetting Polyethylene Insu1ation for Power Cable Rated 601-15,000 Volts"

~

S-66-525 - 1971 51 NEMA MG " Motors and Generators" 1972 Attachment "C" of AEC lett.r dated December 14, 1973,- entitled " Physical Independence of Electric Systems" (see FSAR Appendix 8A). For exception to Section 5.1.2 of Attachment "C" on conduit markings, see FSAR Section l 8.3.1.4 k. p g i \s _

Documents Applicable to Equipment Purchase Orders - The issue of the docu-ments listed above in effect on the date of the purchase orders are

, applicable when supplying equipment / services against the purchase order.

1 e

i i

i i

4 8

8.1-10 ,

I i

4

e SB 1 & 2 Amendment 55 i FSAR July 1985 N

4. Regulatory Guide 1.63 - Electric Penetration Assemblies in Containment Structures for Water-Cooled Nuclear Power Plants 48 The electric penetration assemblies are designed to withstand, without loss of mechanical integrity, the maximum fault current vs. time conditions'that could occur as a result of single random failures of circuit overload devices. The 600 volt system X/R ratio used in specifying the electrical penetrations is 4. Calculations show that this value'is conservatively applied because the actual ratio is considerably less than 4.

To preclude damage to electric penetrations due to single failures of circuit overload protection devices, each penetra-tion circuit, with the exception of instrumentation and low energy circuits, is provided with dual Class IE overload protective devices. For more details refer to Subsection 8.3.1.1.c. 15 kV penetrations are protected by seismically qualified Class 1E fuses. Additional protection is provided by two non-Class lE breakers in series. Dese breakets are coordinated and derive their control power from different batteries. For more details refer to Subsection 8.3.1.1.a.

5. Regulatory Guide 1.75 - Physical Independence of Electric Systems The design is consistent with the criteria for physical independence of electric systems established in Attachment "C" st of AEC (NRC) letter dated December 14, 1973. Attachment "C" which is incorporated as Appendix 8A, is in general confor-mance with Regulatory Guide 1.75. l c

3 i For clarification of position C4 as it relates to associated circuits, refer to FSAR Subsection 8.1.5.3.b. g n

b SEf5 b hysical separation and identification of circuits are ll 0 described in detail in Subsections 8.3.1.3 and 8.3.1.4, 4547 ,

j respectively. l i I

c. Compliance to Branch Technical Position PSB Adequacy of )

Station Electric Distribution System Voltages l l

1. Position B1 An acceptable alternative to the second level undervoltage protection system described in Position 1 is provided. This alternative system is described in Subsection 8.3.1.1.b.4.(b).

2. Position B2 The Seabrook Station design meets Position 2 of Branch

. L Technical Position PSB-1. The bypass of the load shedding feature during sequencing, and its restoration in the event of a subsequent diesel generator breaker trip, is discussed in 62.

8.3-37 l l

4

SB 1&2 Amendment 52 FSAR December 1983 In accordance with the provisions of Section 4.5a and 4.6.2 of 0

FSAR Appendix 8A, Sections 4.5(1) and 4.0.1 of IEEE 384-1974, and Position C4 of Regulatory Guide 1.75, Revision 2, we have elected to associate all of the Non-Class lE circuits with Class IE circuits. This application of associated circuits allows the plant to be designed with one less separation group; that is, instead of having five separation groups consisting of four safety-related separation groups and one non-safety-related separation group, Seabrook has only four separation groups. The major advantages of this approach are the ability to provide greater separation distances between the groups, as well as to reduce the raceway g system's exposure to fire.

, As a result of this design, all plant circuits are specifically assigned to one of the following four separation groups as noted in Figure 8.3-57:

Group A - Train A, Channel I and Train A Associated Circuits l Group B - Train B, Channel II and Train B Associated Circuits Group C - Channel III Croup D - Channel IV The great majority of associated circuits are with Group A, a very limited number are with Group B, and none are with Groups C and D. .

The circuits that are associated with Train A consist of:

1) Non-Class IE power, control, instrument circuits contained within the Nuclear Island.

2) Non-Class IE power, control, and instrumentation circuits that_ traverse the Nuclear Island boundary.

3) Non-Class IE power, control, and instrument circuits outside the Nuclear Island.

The circuits that are associated with Train B consist of:

1) Non-Class IE power, control, and instrument circuits contained within the Nuclear Island.

2) Non-Class IE power, control, and instrumentation circuits that traverse the Nuclear Island boundary.

The Nuclear Island boundary is shown in Figure 8.3-58. This figure denotes the buildings, structures, duct banks, etc., which are part of the Nuclear Island. All other buildings, structures, etc.,

are considered to be outside the Nuclear Island.

INSES.T 3 8.3-40

SB 1 & 2 Amendment 55 FSAR July 1985 to normal operation as practical, the full operational sequence that brings the system into operation, including portions of the protection system, is tested.

b. Compliance with Regulatory Guides

1. Regulatory Guide 1.6 - Independence Between Redundant Standby Power Sources and Between their Distribution Systems The safety-related po tion of the station de system for each unit includes four b.tteries. The redundant safety-related load groups are each fed by a separate battery and battery charger. There is no provision for automatically connecting one battery-charger combination to sny other redundant load group, nor is there any provision for interconnecting batteries either manually or automatically. Te further enhance safety and reliability, two de supply buses of the same train ~may be connected together manually, but circuit breaker interlocks prevent an operator error which would parallel two batteries.

(See Figure 8.3-37).

2. Regulatory Guide 1.32 - Criteria for Safety Related Electric Power Systems for Nuclear Power Plants The design is consistent with the requirements of this regula- )

tory guide. For details, refer to Subsections 8.3.2.1.c and 8.3.2.1.e.

3. Regulatory Guide 1.75 - Physical Independence of Electric Systems a

The design is consistent with the criteria for physical independence of electric systems established in Attachment "C" of AEC letter dated December 14, 1973. Attachment "C" is incorporated as FSAR Appendix 8A and is considered similar to Regulatory Guide 1.75.

For clarification of position C4 as it relates to associated IEyg3e,rt b circuits, refer to FSAR Subsection 8.1.5.3.b. 55

4. Regulatory Guide 1.129 - Maintenance, Testing and Replacement of Large Lead Acid Storage Batteries for Nuclear Power Plants

1. ~

5 For compliance to this regulatory guide, refer to Subsection 8.3.2.1.e.

c. Compliance with IEEE-308, Class IE Electric Systems The station de system conforms to the requirements of IEEE-308.

The power supplies, distribution system, and load groups (see Sub- g section 8.3.2.1) are arranged to provide direct current electric 3 8.3-62

-. . . - . . - - ~ . _ ..

b '

SB 1 & 2 Amendment 52

+

FSAR December 1983 f

power to the Class IE direct current electric loads, and for the control and operation of the Class lE systems. Sufficient physical separation, electrical isolation, and redundancy are provided to j- prevent the occurrence of common failure modes in the Class lE systema,

d. Conformance with Appropriate Quality Assurance Standards The equipment of the de system conforms to the controls for electri-cal equipment listed in Chapter 17.

e. Independence of Redundant Systems The criteria and bases of minimum requirements to preserve the independance of redundant Class IE electric systems are those out-lined in the General Design Criteria and IEEE-308. Safety loads are divided into redundant groups and equipment is physically  ;

l separated from its redundant counterpart so as to prevent the.

occurrence of a common failure mode.

l Batteries are in individual rooms,~and chargers and distribution j equipment are separated by physical barriers, as . indicated on Figure i

8.3-27.

g The criteria and bases for the installation of raceways and #1

-/ electrical cable for this system are the same as those listed for

+

the ac power system in Subsection 8.3.1.4. Train separation through-

! out the safety-related portions of the plant is indicated on Figures

8.3-36, 8.3-43 and 8.3-44, which shows electrical arrangements at j~ the three critical elevations of the unit.

3

f. }%ysical Identification of Safety-Related Equipment I

The methods used to physically identify the de safety-related equip-uent to assure its appropriate treatment is the same as that for the ac safety-related equipment listed in Subsection 8.3.1.3.

Identification systems distinguish between redundant separation j

Jroups; it is clearly evident to the operator or maintenance craf tsman which equipment is safety-related and, if safety-related,

which separation peoup is involved.

8.3.3 Fire Protection for Cable Systems The_ fire prevention and protection system for cables is part of the integrated -

fire detection and protection system for the entire plant, and is described in Subsection 9.5.1.

Design aspects utilized in the prevention of fires in cable systems include separation between redundant trains and voltage levels, cable material selec-

) tion and cable sizing. This is described in Subsections 8.3.1 and 8.3.2.

M.9ht ,

o 8.3-63

INSERT A The Seabrook cable and raceway separation criteria (see FS AR Section 8.3.1.4) is a combination of the standard criteria given in Attachment C of AEC Letter dated December 14, 1973 (see FSAR Appendix 8A) and IEEE 384-1974 and criteria established by analysis and testing as per-mitted by Attachment C and IEEE 384-1974.

INSERT B i

The four separation groups are routed through four separate raceway systems per the separation criteria given in Table 8.3-10. This separation criteria are based on a combination of the following:

(a) Standard separation criteria given in Sections 5.1.3, 5.1.4, and 5.6 of FSAR Appendix 8A and IEEE 384-1974 and (b) Separation criteria established by analysis and testing as permitted by sections 5.1.1.2 and 5.6 of FSAR Appendix 8A and IEEE 384-1974. This analysis and testing are documented in References (a) and (2) (see FS AR Section 8.3.4).

INSERT C The separation criteria within the MCB is given in Table 8.3-10 and was based on. analysis and testing as permitted by Section 4.3.2 of IEEE 420. This analysis and testing are documented in References (1) and (2) of FSAR Section 8.3.4.

INSERT D 8.3.4 References (1) " Analysis of Separation Criteria for Seabrook Station" dated March 24, 1986.

(2) Wyle Test Report No. 47966-02 dated January 24, 1986.

---n.--- , ,,-.,.m. , -- -en-. -- -, --- -

4

,o '

TABLE 8.3-10 ELECTRICAL CABLE AND RACEWAY SEPARATION CRITERIA SEPARATION DISTANCE HORIZONTAL VERTICAL 7

Cable Tray to Cable Tray General Plant Areas (1), (4) 3 foot 5 foot

-Cable Spreading Room (1), (4) I foot 3 foot Conduit-to-Cable Tray (2), (3), (4) 1/2 inch 1/2 inch Conduit-to-Conduit (2), (3) 1/4 inch 1/4 inch Aluminum Sheath ( ALS) Cable-to- 1/4 inch 1/4 inch Cable Tray / Conduit (2), (3), (4)

ALS to ALS (2) in contact in contact Main Control Board (2), (5) 1 inch free air 1 inch free air space or in space or in contact with contact with opposite sides of opposite sides of a barrier a barrier Other Internal Panels (1), (5) 6 inches 6 inches NOTES:

(1) Standard criteria from FSAR Appendix 8A/IEEE 384-1974 (2) Criteria established by test and analysis (see Section 8.3.1.4(a))

(3) Conduit includes rigid conduit, flexible conduit, and wireway (4) S'ee Section 8.3.1.4(e) for explanation of the_zero reference point for measuring ' separation to cable trays (5) This separation applies to wiring and equipment

- , , - - -c- ------

-v-w,, , - , ,, ,, , ,