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2. General
Until now, the oil-immersed on-load tap-changer (hereinafter referred to as OLTC), being widely used in
worldwide substation, inside which the oil is an insulation medium for OLTC themselves and for extinguishing
arc occurred on the main switching contacts and transition contacts, as well as a medium for lubrication of
mechanical parts and for cooling of contacts and all other current carrying parts. Therefore, this type OLTC is also
called the OLTC of arc-extinguishing inside the oil. The carbonization of oil for this type of OLTC is inevitable
during the operating of tap-changer. With the switching times increasing, inside the OLTC oil chamber there will
be more and more carbonizations. Therefore, except from neutral point connection, in application for other
winding connections of transformer, or power transformer with voltage of 220kV or above, the auxiliary device
like online oil filter plant has to be assembled with the oil-immersed OLTC in order to guarantee the insulation
level of oil and to decrease the carbon granule. When this kind of OLTC is used in the rectification and furnace
transformer, it operates very frequently under the full-load or even over-load, which quickens the wearing-out of
arcing contacts, the carbonization of oil and also the wearing-out of mechanical parts. As a result, such works as
continual changing of new oil and replacement of arcing contacts, frequent inspection and maintenance have to be
done to make the OLTC reliable, even replacing the new OLTC within the service life of transformer, the cost for
maintaining its normal operation is quite expensive.
The type of oil-immersed and vacuum arc-extinguishing OLTC-SHZV, with arc contacts replaced by vacuum
interrupter, has very prominent advantages˖
1. The current breaking in the vacuum interrupter, and the arc produced also extinguishing in the vacuum
interrupter, which solved the problem of oil carbonization. Therefore there is no need to equip with online filter
plant under any application condition.
2. Since the carbonization of oil in the oil compartment is eliminated, the carbon granule adhered to the surface of
insulation material does not exist any longer, the insulation level is guaranteed.
3. The task of carrying current for long time is undertaken by special mechanical main contacts while the vacuum
interrupter only taking the current instantly through, so the overload capacity of OLTC has been improved greatly.
4. All the vacuum interrupters are fixed firmly and mal-operation will not happen. The highest voltage of the
OLTC is 362 kV three-phase OLTC is application for neutral point winding connection of transformer with
voltage up to 765 kV,and single-phase OLTC can be used for any selectable winding connection, the max. rated
through current of tap-changer is 1300 Amp. in three-phase and 3000 Amp. in single-phase.
This instruction includes all necessary information for installing and using SHZV tap-changers.
NOTE!
Special design is available. Please contact Huaming for further information.
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