ML19330A242
| ML19330A242 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 08/13/1971 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML19330A236 | List: |
| References | |
| NUDOCS 8007151025 | |
| Download: ML19330A242 (4) | |
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RIIPC!i2 % QLL~rIOff FPOM DR. GOODM/Ji RECi?O!!!G DERGE:Cl FOWER SUTPLY SYSJEM Dr. Goodman's Question (Tr. 2920):
"... tased on extensive past experience of any kind of standby power systems, whether it's a hospital or anything else, how many redundant systema do they have per unit that has to te manned?"
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/m,wer:
The necessity of providing efficient generaticri of adequate elec-tric power in emergencies armi other short term situations has received in-creasing attention by industry in recent years. Typical installations requiring such emergency power sources are hospitals, rest hcmes, comrmmi-cation centers, aircraft centrol and vaming systems, and air and marine navigstional systess.
In order to detemine the Yasis on which the number of diesel generators for various standby uses is determined, infoz nation was solicited fran tva of the najor suppliers of autcoatic start diesel generator sets, Alco Engine Division of White Industrial Power Inc. and Fairbanks-Morris, and from a number of facilities at which suca. Senerator sets had been I
installed.
The installation experience of the suppliers was that it has not been the practice to require, cr prchde, redundant systems for hospital nervice. This s% ject was further pursued by direct contact with four hosfitata in the San Francisco Bay area, une in New York City, and one I
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i in Baltimore in order to determine if the number of standby units provided bore any relaticuship to the number of facilities served, i.e., operating rocas.
In each instance, it was detemined that redundancy was not pro-vided and that load grouping on each unit was not selected to provide divers' ty of supply for a particular function.
i For example, all operating ^
rooms may be supplied by only one diesel generator while all elevators may be supplied by another.
tfith recard to standby power systems for airport facilities, a study is currently in progress for the FAA to establist new reccanended standards for design of high reliability power systems with safety of air-craft movement and handling the prime concem. Current criteria for the fifty U. 3. airports designated by the FAA as continuous pover airports does not require redundant systems but does require a standby engine Because of the long distances between facilities at airports generator.
which necessitate long cable interconnecticus, FAA rules express a pref-erence for installations utilizing a small diesel generator at each out-lying facility. ';nier such a criterion, redundancy of engine generator cets is not provided.
Dulles airport is an example of an airport that does utilize a redundant power system.
This system consists of two full capacity diesel ec.gine generators each capable of serving all facilities at the airport.
Thus in this case the number of generaters is based on redundancy but not on the number of electricity-consuming facilities. During the time in serv-ice there have been no reported failures of the diesels to start.
Chipboud emergency diesel ganerator sets for passenger ships
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vere also considend since this appl' cation places total dependence on I
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the standby power system, no "off site" power source being feasible. The i
regulations of the U. S. Coast Guard and rules of The American Bureau of Shipping place 1erticular emphasis on independerx:e of the emer6ency source of supply from normal ship service and propulsion engines and reliability of starting (multiple cranking cycles) but redundancy is ni a requirement.
Further statistical background regarding diesel starting re-garding diesel starting reliability was obtained from the Alco Engine Division of White Industrial Power Inc. Alco has made 12 auta::atic diesel generator sets fcr e: ergency standby service since 1955 Five of these are in hospital standby, one in a prison, two in a telephone exchange, one at the end of a power line serving several tovna, one in an airline terminal and two in nuclear facilities. Except for initial debugging, and one specific failure and later removal cf a catalytic afterburner, no failures to start have been reported to the manufacturer. Based upon the total time in service and an assumed test frequency of at least once every month, it appearc that these units may have aggregated in excess of 750 rtarto without failure.
The results of this comparisen of industry practice may be sum-marized as follova; 1.
In no m; plication that we are aware of, other than as standby power supplies for nuclear power generating j
stations, is redundancy of emergency generators pres-ently a design requirement. The absence of such a requirement appears to be to a large extent based ai satisfactory perfomance of standby systems over the 1
last twenty years. It should also be noted that in l
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4 the case of land installations, the emergency diesel generator is generally viewed as redundant to the off site source of supply.
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The number of diesel generators required is in no case determined by units or facilities to be manned, but rather by:
a) Total load requirements (i.e., if the load reqsire-ment exceeds the capacity available in a single suitatie unit more units are required).
b) Physical separation of facilities dictating use of separate diesel generators.
c) Expansion or additica of new facilities requiring additional standby power.
d) Diverse load requirements such as large single phase loads versus three phase loads.
It is our opinica that the criteria as developed for the design of stand-by power supplies for nuclear power generating stations, and as applied in the design of Midire.d Plant, has in fact drawn on the best available ex-perience in industry. And further thpt in meeting the overall design re-quirements of independence, separation, and redundancy of standby sources the number of staniby diesel generators is properly determined by the need for ccupatibility with the number of redundant load groups and ability to provide the required design basis capacity not by the number of facilities served.
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