ML18116A317
| ML18116A317 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 07/10/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18116A316 | List: |
| References | |
| NUDOCS 7908140105 | |
| Download: ML18116A317 (3) | |
Text
INTRODUCTION e
SAFETY EVALUATION OF PROPOSED MODIFICATION FOR 480V EMERGENCY POWER SYSTEM SURRY POWER STATION, UNIT 1 DOCKET NO. 50-280 By letter dated May 3, 1979, VEPCO has proposed modification to the 480V emergency power system on Surry Unit 1.
The modification consists of adding one 480V Class IE load center to each train of the emergency power system.
The justification and adequacy of this modification is established by licensee's subsequent submittals of May 17 5 1979, consisting of load and voltage analysis and that of June 18, 1979, consisting of an integrated test program and relay coordination.
BACKGROUND Based on LER#79-008 from VEPCO dated April 5, 1979, we requested the licensee by letter dated April 16, 1979 to propose modification plans and a testing program to correct the reported underpower capacity condi-tions on the station 480V emergency buss es.
The 1 i censee submitted the modification plan dated May 3, 1979.
The plan constitutes of adding a 1333 KVA(fan cooled rating) 480V load center to each of the two trains of the emergency power systems.
A 11 460V 1 a rge motors ( 200 HP and above) are powered from the existing load center whereas the MCC feeders are from the added load center.
The existing 4KV feeder breaker shall be common.
to both load centers.
Details of the modification are shown on the attached sketch and we discussed the modifications with the licensee in a meeting held on May 3, 1979.
In response to our request in the meeting, the licensee submitted a detailed study dated May 17, 1979, with regard to loading capability of the modified system and the voltage profile on Cl~ss IE busses during various modes of plant operation as specified in the FSAR.
They further submitted their integrated test program and relay coordination data on June 18, 1979, to establish the adequacy of the proposed modification.
EVALUATION Addition of another load center to each of the two trains and transferring two MCCs from the existing load center to the one added, resulted in reduced loading of the existtng load center to approximately 75% of its f~n-c0~ 1~d r~~in0 f~"~ the o~igi~21 lo?din: of almost 125%.
The new 102c c-<;:1*~2t S'.orves on*tj' tv-10 hCCs anJ is loaded to approximate1y 507~ o*?
it:: f2t:.... crc'10d r~-;-t1~:J.
Th[:: 7-!1~*:{~-:~!c:'. 0.c c 1c-::*:d ce: 1:*~e~---
-~::--i ;::c.c:h t\\**r*f!1 2... ~
snaring t~e existing connectea 1oaa has adequately improvet voltage conditions on the 480V Class IE busses for all plant operating conditions.
The steady state voltages on 480V Class IE equipment terminals remain within the design limit of plus 10% for light load condition and minus 10% for heavy load condition of the plant for anticipated switch-yard 7908140(0'5"
e
- voltage variations.
The itarting voltage on the 480V Class IE equipment remains* above 70% of the name plate rating during the worst condition of simu1taneous low grid voltage and heavy bus loading.
The current carrying capacity of the cable between 4KV. breaker and the load center trans.former is -
150% of air cooled amperage rating of the load center.
One of the new load centers has a disconnect switch on the primary side of the load center transformer.
In the meeting, the licensee informed us that there is a single kirk key that is used to close both the disconnect switch and the L.C. bus supply breaker. This feature ensures closure of the disconnect switch before the supply breaker is closed.
The proposed test program for the modified 480V Class IE ?'YStem is suffi-cient for verifying the systems design capability to perform its safety functio~s.
The program is capable of testing 480V Class IE equipment ratings and performances.
CONCLUSIONS The analysis, data and other information provided by the licensee show the following features of the modified 480V Class IE systems.
a.-
Total load on the existing load center is within its self-cooled rating.
- b.
The new load center is only 50% loaded~
- c.
Ampacity of the 4KV cable connecting 4KV breaker-to load centers is adequate.
- d.
Starting and steady state voltages on the 480V Class IE equipment are within design limits.
- e.
Integrated test program for the modified 480V Class IE system is
~
adequate.
It is, therefore, our conclusion that the proposed modification to the 480V Class IE system is acceptable.
J. i\\\\\\ Pi
\\
tli
~ !j.
\\
,._ --..c..-,;,_:_----------------...... ___________
_:s:!_!,0t:'.,!.:lf~l...;W:..:.D::.:1:..:.Tr:,..l.!:..INC=IN:!!f(~UH~ac::!o~*:..::l'O~*"!:!!'~'°'".!.!~'-----------------""'---------',----'-,
MC.C.
IJ\\-1 tJciTE!S 1,/1orll v.CC.
\\,J\\*l.
, /,.l!t.fLI
/µ1,(f't/
'2000 I\\ 9KR W\\111 \\,00 n
'TRIP co\\L CJ) 1::x.,~T1 tJ.9 C>..Bt.E.5 Lf... ru 11 HI. PL\\, I J 10PLI 1 ~ \\\\-110 PL!
TO '8(. R.!.RooTe.U k5,;;; T{f.1*At;(iED /\\S '61-\\C>W~
- ~
MCC.
n\\1-1
/1//ol'LI V\\CC
,u,-2.
Jl/l'sPLI I,
QA.* ctn:. -:r:
ONE. Lu.a:; "Dil\\~RA.),\\
- cALc, HollE EME~. rwif.R. s-<sTeM DATE, -1111,1 n.