Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
For SFS equipment power supply a substation with two dry transformers have been
constructed with power of 630 kVА and two-section switchgear, with automatic switch to backup
equipment between the sections. The power is supplied to the substation by two independent cable
lines from 6 kV sections on units 3 and 4.
1.4.2.7.1.1 Cable traces and sections
The main elements forming the SFS electric power supply logic are as follows:
· two transformers 6/0,4 kV ;630 kVА: They are located in one room of SFS.
· two 0,4 kV sections (I and II): Each of the sections is connected with one of the
transformers.
· 9 assemblies 0,4 kV: four of the assemblies are connected with the operating power
supply from SFS I section (operating) and from SFS II section (backup) and are located in
one room of the SFS. The other 4 are connected with power supply from SFS section I
(operating) and SFS ІІ section (backup) and are located in a separate room and one separate
assembly with power supply from SFS I section (operating) and from EDGP (backupuninterruptible),
which is located in a separate room.
1.4.2.7.1.2 Logics, layout and protection against internal and external events
The auxiliary electric equipment is located in separate rooms of SFS, which are seismically
and fire resistant. To decrease the fire hazard, the greater part of the cables is with cover made of
inflammable material. Besides, treatment of cable sheaves with fire protection composition is
provided.
1.4.2.7.2 Backup power supply
The SFS power supply logic is implemented with two independent channels for operating
off-site power supply.
1.4.2.7.2.1 Independence, physical separation and protection against external and internal
impacts
The power and control cables routs of the two independent channels of SFS electric power
supply are specially separated – they go through separate rooms, or where impossible, by different
walls of the room.
1.4.2.7.2.2 Restrictions in availability of backup power supply sources and external measures
to extend operability time
In case of failure to power supply to one of the auxiliary switchgear sections due to external
cause (failure to transformer or in 6 kV chain) automatically switches off the automatic circuit
breaker and entire load on auxiliary transformer substations set is connect to the single transformer.
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