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Power Systems has chosen to use the
basic padmount transformer design which is a proven
technology since the 1970’s. This transformer design
offers an economic and reliable package and making the
overall appearance very acceptable.
All transformers used with the Power
Systems MiniSub are built to the CSA C227.4 M1978 specification
, and conforms to CSA C802 specification for efficiency
and losses. Transformer sizes are available from 150
KVA up to 3000 KVA in 5 to 34.5 kV range. This gives
a very broad range of application for the MiniSub.
Transformers are available in standard
transformer oil (ONAN), or
R-Temp oil (LNAN)
for installation in non fire rated environments. Our
transformer designs are also built to meet ANSI/IEEE
C57.92-1981 guide for loading of oil filled transformers
55°C or 65°C rise, which allows for up to 30%
overload.
Transformer Standard Accessories
- Liquid temperature gauge
- Liquid level gauge
- Pressure relief device
- Fill and drain valve
- Transformer riveted cover
- Tap switch and off load 5 position
changer
- Copper ground bar in both HV and
LV compartments
- Lifting and jacking devices
- Spare fuse holder
- Tamperproof design with secure hinges
and lockable handle.
Fuse Protection
All Power Systems MiniSub's are equipped with a system
of Bay-O-Net® and current limiting fuse assemblies
in a two fuse protection scheme, with the current limiting
fuse as the backup. In this arrangement, secondary faults
and overload currents are cleared by the Bay-O-Net®
fuse. High level faults caused by internal failure is
cleared by the CL fuse. The two fuses are connected in
series. If a CL fuse is not requred, an isolation link
is provided.
Access to the Bay-O-Net® fuse is
restricted by a metal cover over the fuse holders which
is key interlocked with the ArcWhipper switch, to be
sure that power is in the off position prior to assessing
the fuses.
NOTE: The application of internal
fusing in voltages at 25kV and above can only be done
in a wye primary connected design. The load on the transformer
can not exceed more than 50% delta connected secondary
loads. Certain condition of ferrule resonance can exist
at these voltages and the application of lightning arrestors
should be considered.
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