ML17298B685
| ML17298B685 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 12/17/1984 |
| From: | BECHTEL GROUP, INC. |
| To: | |
| Shared Package | |
| ML17298B684 | List: |
| References | |
| RTR-REGGD-01.075, RTR-REGGD-1.075 13-ES-600, NUDOCS 8412200287 | |
| Download: ML17298B685 (13) | |
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Table of Contents RG 1.75 Low Eneggy, Ciecu.it=Analysis 1.0 PURPOSE 2.0 EVALUATION BASIS 3.0 DETAILED ANALYSIS
4.0 CONCLUSION
5.0 REFERENCES
l.0 Purpose This study provides ustificetion b.. a a-y.
n lys.i-s-that,although some nstcument c ccuits cables do not meet the separation requirements of RG 1 lh-he effected Class lE circuits cannot be degraded below aa
~ acceptable level.
The results of this study will only be used to justify deviations from the RG 1.75 separation requiceme t (i
d conf igucationl'interference problems) on a case by b
i Th n
s
.e.,
ue to construction se y case as s.
The analysis shows that consecvetively established maximum fault essembl cenn m
eu curren s
n one cable t
essem y cannot cause degradation of another cable assembly in the vicinity.
2.0 Evaluation Basis h.
Ciccuit Classifications Only instrument circuits ace evaluated in this study as to be "low energy circuits."
Power and control circuits are only considered from the standpoint that these low energy Class lE oc non Class lE instrument circuits cannot degrade the Class 18 power or control ciccuits below an acceptable level.
B.
Cable Construction In that the cables installed at the Palo Verde Nuclear Generating Station meet the requirements of IEEE 383-19?4(~),
they are considered flame retardant and will self-extinguish when the flame coaxial source is removed.
(Mith the exception of some fibe ti d
- cables, the cabling installed passed the flame test with a er op c an 210,000 Btu pec hour source which is three times the requirement)
C.
Circuit Impedance Except where the seperati.on problem is at a specific single point, this analysis does not determine the fault limiting characteristics of cables.
Circuit impedance, if considered, would further limit fault currents due to the small wice size (i.e., yielding high resistance) of the instrument cables.
Powec Supply Voltages n
z's.
Qh E.
In most cases power supply pecformance data under faulted conditions is not available.
Therefore, the output is considered to remain constant at its nocmal value.
This basis is conservative since most powec suppli,ed to these circuits is provided by regulated power supplies (amplifiers) in which a shocted circuit vill cause saturation resulting in a near zeco output source voltage.
Interrupting Devices Actuated by Fault Current Although usually included in the design, this analysis does not take credit for any internal cI.rcuit breakers or fuses.
3.0 Detailed Analysis The following is a case by case analysis justi,fying that the identified circuits are low onerty and ttsretore-cannot-causa dstradatlon" oC any Class lE cables in the vicinity.
s A.
Non Class 1E Fiber Optic Cables Fiber optic cables do not carry any electrical signals.
The optical signals that they caccy cannot generate heat; therefore, fiber optic cables are consideced low enecgy circuits.
Failures n fiber optic cables cannot affect any other cables in the vicinity..
B.
Non Class 18 Fire Detection Pcotectowice Protectowire consists of two conductors individually encased in heat sensitive material.
The encased conductors are twisted together to impose a spring pressure between them.
When heated to the critical or operating temperature the heat sensitive material yields to the pressure on it, permitting the conductors to move into contact with each other.
A supervisory current of 1.1 ma normally flows through the Protectowire.(15~
During an alarm conditi.on this current rises to 12 ma.(15)
Therefore, Protectowice is considered a low energy circuit, which is designed to shoct during an alacm condition, and cannot affect any other cables in the vicinity.
C.
Non Class lE Fice Detector Cables Within Panels When an ionization fire detector alarms, it closes a contact which shorts out the loop(+) end lo'op (-) terminals.(4)
The detector circuits have a normal operating, current of 300 microamps and an alarm current of 29 milliamps.(4)
Fice system alarms are checked by shorting out the end of line resistors.
Fire detector cabling within panels is designed to be shorted ducing an alarm condition, therefore, is consi.dered a low energy circuit which cannot affect any other cables i.n the vicinity.
D.
Non Class 18 Radiation lfonitoring System Computer Signal and Information Cables The computer power supply can provide 5
+.05 or 12
+.Ol volts DC.
(Since the data for the 5 volt power supply is more (19) conservative it is used in this analysis.)
This data indicates that the 5 VDC power supply will current limit to 4.5 amps.
The cable has a curcent rating of 16 emps.(12)
Comparing the cables ampaci,ty rating to the maximum current ducing a fault the Radiation Monitoring System Computer Signal and Information Cables can be considered low energy circuits which cannot affect any other cables in the vicinity.
a
'p"
(NOTE:
Based on the fact that the power supply voltage is 5 volts, and there is inherent voltage drop within the circuit, fault current will be eubatantially reduced from the a
5 Indicated.)
om e
amp vaiue Class lE Radiation Monitoring System Detector'Cables The power supply for the radiation monitoring detectors has an output oi 500 to 1500 VDC. (16>
The circuit resistance is at least 10 kohms due to a 10 kQ resistor in series.
Assuming that the regulating power supply is not current limiting (conservative assumption since the power'upply data sheet for C-15 high voltage power supplies indicates that the rating is 1 ma), the 10 kQ resistor will limit the fault current to 0.15a or 150 ma.
Therefore, the Radiation Monitoring System Detector Cables can be considered low energy circuits which cannot affect any other cables in the vicinity.
Non Class 18 Plant Telephone System rin er Discussion with Teleflex Communications indicates th t t 1 h
g, current is SO ma.
Discussion with Brand Rex (system cable s
a eop one manufacturer) indicates that the No.
19 telephone cable has an ampacity of 7 amps.
Since maximum telephone current occurs during
- ringing, (SO ma) and the cables ampacity is 7 amps the telephone circuits can be considered low energy circuits.
4ewa G.
Non Class 1E Plant Paging System The amplifier output is 70V at an impedance of 100 Q(5 ~ 1B).
Discussion vith Brand Rex (system cable manufacturer) indicates that the No.
19 speaker cable has an ampacity of 7 amps.
This cable cable has a resistance of 8.51 9/1000 ft.(17)
Th h
t ca e to a speaker is 300 ft. vhich results in a cable resistance of 2.55 Q.
Since the average cable length is about 1000 ft. i.t is likely that some additional resistance due to cable vill be nel c
present to limit fault current.
However conservati 1
rva ve y neg ecting the cable resistance and assuming the output of the amplifier remains constant during a fault, the maximum fault current i,s.7 amps.
Comparing the cables ampacity of 7 amps vith the maximum fault current of.7 amp, the plant paging circuits can be considered to be low energy circuits, which cannot damage any associated cabling given a fault condition.
Non Class lE Main Steam and Feedwater Isolation System (MSPIS)
Trouble Alarm Miring MSFIS trouble alarms employ photosensitive resistance detectors whose resistance changes from 90 ohms to one megaohm when trouble is detected in the MSPIS cabinet(11).
The alarm wiring is No.
22 AUG Tefzel insulated and is terminated on terminal blocks
within two metal boxes interconnected by a rigid metal conduit vithin the MSFlS cabinet.
Plant 'annunciator employs a 24 VOC power supply to interrogate the resistance detectors through interconnecting wiring.
A signal input card in the annunciator is desi.gned to limit the signal current to 2 milliamps when the input is shorted at the annunciator terminals.
Considering the short circuit fault across the resistance
- detector, the current in non 1E alarm viring vould increase to 2 milliamps, as limit'ed by signal input card, resulting in an insignificant temperature rise in non 1E wiring and no effect on 1B wiring.
Considering a short circuit fault across the annunciator signal input card, the current in non lE wi,ring will be limited by the internal resistance of the annunciator power supply, the interconnecting wiring, and the resistance detector (90 ohms minimum).
Disregarding the internal resistance of the annunciator power supply and the resistance in viring, the maximum current would be:
24 V/90 ohms
= 0.266 amp.
Since the wiring in the cabinet is rated at 3 amps, the temperature rise due to fault current would be negligible.
Considering the ground fault in a non 1E MSFXS cabinet vire, a
negligible current would flow only in annunciator ground detector since the annunciator is otherwise ungrounded.
The 1E viring would not be affected.
Therefore, since there is no degradation of lE circuits by any fault in non 1E circuits, these circuits can be considered lov energy circuits which cannot affect any other cables in the vicinity.
Non Class 1E RCP Temperature Sensor Nonitoring System Spec.
13-JN-111 Power is fed through a 332 ohm resistor to an operatf.onal amplifier< which in turn feeds this power to the temperature sensor.<
The 20 VOC pover supply is ungrounded.<6~
This analysis does 'not take credit for the current limiting operational amplifier.
The power supply vill be considered grounded.
Mith the above assumptions, the conservative maximum fault current at the temperature sensor vill be 0.060 amp to ground.
Therefore, the temperature sensors:
13-J-RCN-TB-118,
-128, -138, -148, -150,
-151, -156, -157, -160, -161, -166, -167, -170, -171, -176, -177,
-180, -181, -186, -187, -190, -191, -192, and -193 can be considered lov energy circuits which cannot affect any other cables in the vicinity.
Non Class 1B RCP Temperature Recording System Spec.
13-JH-304 There is a resistor of 40K ohms in series with a 21 VOC supply to the temperature sensor.<7~
The maximum fault current at the
-1 t
I r
temperature sensor will be 0.001 amp to ground.
Therefore the temPerature sensors:
13-J-RCN-TE-152,
-153, -158, -162, -163,
-168, -172, -173, -178, -182, -183, and -188 can be.considered low-=--- =-
-- -energy--circuits which cannot affect any other cables in the vicinity.
'.(
Class lE and Non Class 1E RCP Shaft Speed Sensing System The maximum current for a fault at the speed sensing probe would be less than 0.030 amp.(13')
Therefore, these probes 13 J RCN SE 154 ~
155 ~
164 ~
1&5 ~
174 ~
175 ~
184 ~
185 ~
-123A, -133A, -143A, 13J-RCB-SE-113B,
-123B,
-133B, -143B, 13J-RCC-SE-113C,
-123C,
-133C,
-143C, 13J-RCD-SE-113D,
-123D, -133D, and -143D can be considered low energy circuits which cannot affect any other cables in the vicinity.
L.
Non Class 1E RCP Vibration Monitoring System Spec.
13-JM-803 The maximum current for a fault at the proximity probe would be less than 0.005 amp.(14' Therefore, the proximity probes 13J-SVN-YE-21, -22, -23, -24, -25, -26, -27, and -28 can be considered low energy circuits which cannot affect any other cables in the vicinity.
Non Class lE Valve Vibration Monitoring System Spec.
13-JM-366 The accelerometer probes create a small electrical charge (e.g.,
0-2.4 x 10-9 coulombs) which is amplified to 0-5 volts by a charge converter.(10)
The converter sends no voltages or currents to the probes, it only measures the charges created by these probes.
Since these probes 1-J-SGE-ZE-&97,
-699, -701,
-706, -707, and -708 produce such a small charge they can be considered low energy circuits which cannot affect any other cables in the vicinity.
4.0 Conclusion The above discussion Justifies that the analized circuits do not provide sufficient energy under faulted conditions to cause degradation of other Class 1E circuits in the vicinity.
5.0 References 1.
1 1975 2.
IHHH Standard 383-1974 f
3.
I~
equi e~,s*.
'4 V
'1 II 4J
4.
5.
6.,
7.
8.
Instruction Manual M651-92-2 Instruction Manual E048h-13-1
.Instruction Manual Jill-91-& (Model 2hl-P2V}
Instruction Manual J304-8-3 (Model M11H)
Instruction Manual N001-6.02-171-4 10.
Instruction Manual J803-23-11 Instruction Manual J366-431-2 ll.
Instruction Manual J108-229-3 12.
Telephone Notes TN-3&71 dated 2/24/84 13.
Telephone Notes TN-8-3951 dated 11/5/84 14.
15.
16.
Telephone Notes TN-E-3915 dated 10/19/84 Power Requirements of Circuits Protectowire Panels M650-722-1 Operation Manual N997-274-2 17.
QVDR 8033-11-1 18.
19.
hltec Lansing Catalog 183.2.5M Rev.
11 (15938 Aniplifiers)
N997-561-1
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