ML20134E799
| ML20134E799 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 10/28/1996 |
| From: | CENTERIOR ENERGY |
| To: | |
| Shared Package | |
| ML20134E790 | List: |
| References | |
| NUDOCS 9611040111 | |
| Download: ML20134E799 (4) | |
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Attachment 2 PY-CEl/NRR-2105L i
Page 1 of 4 Typical Derating Calculation for a Tray
'Ihe general approach utilized in these calculations was as follows:
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- 1. Obtain the ampacity value from the appropriate industry standard, accounting for envimnmental conditions, such as equipment temperatum, ambient temperatum, cable type, and raceway construction.
( 2. Adjust the ampacity value fmm the industry standard for diffemnces in cable l diameters per ICEA P-54-440 Section 2.3 " Correction Factor for Diameters of Cables."
- 3. Apply an additional derating factor to account for the pmsence of'Ihermo-Lag, utilizing data provided in Refemnces I and 2.
- 4. Calculate the ampacity margin.
'Ihe following is a sample calculation for tray number 106, which contains thme energized circuits.
TRAY NO.106 DESCRIFrION REllARKS 38 3~
SIZE LENGTH = 157' 4'I6 / 460 V TYPE 3;g DIVIslON I LADDER TYPE.IlOT DIPPED, MATERIAL GALVANIZED STTEL THERMO-LAG II Tl 55, Hom M RAMO FIRE ZONE OC-1A AMBIENT 11 MPERATURE = 88*F TRAY FILL (%) 33.67 CABLE O.D. VS.1 RAY %1DTII TOTAL NO.OF 3 CABIES Tray 106 contains thme circuits: IP42FI A, IP47FI A, and IP47H1 A, with the following cable characteristics.
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9611040111 961028 PDR ADOCK 05000440
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Attachment 2
. r PY-CEI/NRR-2105L Page 2 of 4 CABLE CHARACTERISTIC IP42FIA IP47FIA IP47HIA CABLE NUMBER IP42 IP47 IP47 VOLTAGE CLASS 480 V 480 V 4KV CABLE ID NUMBER IA 1A lA CABLE TRAY del"Fl! GNCIIES) 1.0 1.0 1.0 CABLE CONT 10URAllON 3 CONDUCTOR 3 CONDUCTOR 3 CONDUCTOR CABLE SIZE 4/0 4/0 4h CABLE CONSTRUC110N 5 KV (ARMOR) 5 KV (ARMOR) 5 KV(ARMOR)
CABLE O.D. (INCIIES) 2.02 2.02 2.02 BASELINE AMPACirY (AMPS) 288.41 288.41 288A1 EQUIPMENT DESCRII' HON PUMP PUMP CIIILLER FULL LOAD CURRENT (AMPS) 115.0 115.0 94.0 ENEROIZEDOR DE-ENEROlZED ENEROlZED ENERO! ZED ENERO! ZED The depth of cables luuted in trays that contain well below 50% tray fill is calculated per ICEA Publication P-54-440 Section 2.2 " Calculated Depth of Cables in Trays" as follows:
2 where: d = diameter of cables (in)
Calculated Depth (in) = Id w = width of tray (in) w However, this tray consists of a single layer arrangement of the cables. Single and three-conductor 600 V and 5 KV cables #4 AWG and larger are routed in power trays in a single layer with 3/8" minimum spacing between cables. A cable depth of 1" was used for cable trays consisting of a single layer arrangement of the cables. Cable ampacities, showTI below, are obtained from ICEA P-54-440 Tables 3-15 for a cable depth of 1.0".
CIRCUIT CABLE NUMBER AMPACITY IP42F1A 257 amps 1P47F1A 257 amps l 1P47HIA 257 amps 1
'Ihe diameters of PNPP 600 V and 5 KV cables are generally not the same as those used in the ICEA tables. Therefore, cable ampacities are adjusted for differences in cable diameters per ICEA P-54-440 Section 2.3 " Correction Factor for Diameters of Cables" as follows:
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Attachment 2
. o PY-CEl/NRR.2105L Page 3 of 4 d where: d, = PNPP cable diameter o do = cable diameter from IGA I, = p* X I Table 3-15 I. = ampacity of cable diameter do from ICEA Table 3-15 I, = ampacity of cable diameter d, he result of the cable ampacity adjusted for differences in cable diameters is the baseline ampacity. The following table pmvides the results of the cable ampacities for the circuits in tray 106, corrected for differences in cable diametels.
1P42F1A IP47FIA IP47111A IGA Cable Diameter 1.80" 1.80" 1.80" PNPP Cable Diameter 2.02" 2.02" 2.02" IGA Cable Ampacity 257 amps 257 amps 257 amps PNPP Cable Ampacity 288.41 amps 288.41 amps 288.41 amps IGA P-54-440 also provides a correction factor for differences in temperatures. The ICEA tables are based on a conductor temperatum of 90 C (194 F) and an ambient air temperature of 40 C (104 F). However, the highest actual ambient temperature surrounding the cables evaluated in PNPP Calculation MISC-0009 is 94*F. To be conservative, the calculation for tray 106 does not include correction factors for a lower ambient temperature.
De percent margin between cable ampacity and full load current rating is detemlined for the cable with and without a nemio-Lag fire barrier in place. De actual conductor load is based on equipment FULL LOAD AMPERE (FLA) ratings. De load factor is 1.0 for resistive loads and 1.1 for otherloads. De calculation of the percent margin between cable ampacity and fullload current rating is detailed below for circuit IP42FI A.
% MarginWithout hermo-Lag = (Cable Ampacity)-(Fullhad Current x Load Factor)
Cable Ampacity 288.41 - (115.0 x 1.1)
% Margin Without Hermo - Lag = = 56%
288.41 Applying the additional derating factor (0.315 for cables in trays), as stated in step 3, to account for the presence of Thermo-Lag, the ampacity with ne:mo-Lag is:
AmpacityWithThermo-Lag = (Cable Amyiiy) x (1 - Derating Factor)
Ampacity With Thermo. Lag = 288.41 amps x (1 0.315) = 197.56 amps
Attachment 2 4 PY-CEl/NRR 2105L
- Page 4 of 4
% MarginWithThermo Lag = (Cable Ampacity)-(Full Load Current x Load Factor)
Cable Ampacity l
197.56 - (115.0 x 1.1) ,
l % MarginWithThermo-Lag = = 36%
- 197.56
'Ihe percent margin between cable ampacity and full load current rating was also calculated for circuits IP47FI A and IP47111 A. 'Ihe results for the three cables in tray 106 are shown below.
f CIRCUIT NO. IP42FIA IP47FIA 1P47H1A i
! FUllLOAD CURRENT (AMPS) 115.0 115.0 94.0 CABLE AMPACfrY(AMPS) 288.41 288.41 288.41 AMPACITY WrDITIIERMo LAG (AMPS) 197.56 197.56 197.56 AMPACITY MARGIN %TrilOUT TIIERMO-LAG 56 % 56 % 64 %
AMPACITY MARGIN %Till TIIERMO LAG 36 % 36% 48%
l REFERENCES
- 1. Omega Point Laboratories Report No.12340-94583,95165-95168,95246,"Ampacity Derating of Fim Pmtected Cables," dated 03/19/93.
- 2. NRC Letter to Texas Utilities Electric Company dated 06/14/95," Safety Evaluation of Ampacity Issues Related to 'Ihermo-Lag Fire Barriers at Comanche Peak Steam Electric Station, Unit 2 (TAC No, M85999)."
- 3. Insulated Cable Engineers Association (ICEA)(IPCEA) Standard P-54-440 (NEMA ,
WC 51),1986, Ampacities of Cables in Open-Top Cable Trays. l 1
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