Shzv Vacuum on-Load Tap Changer for Oil Immersed Transformers Switch

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 currentcarrying 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 capacityof OLTChas been
improved greatly.

4. All the vacuum interrupters are fixed firmly and mal-operation will not happen.

The highest voltage of the OLTC is 252kV, three-phase OLTC is application for neutral point winding connection
of transformer with voltage up to 550kV, and single-phase OLTC can be used for any selectable winding
connection, the max. rated through current of tap changer is 1000 Amp. in three-phase and 2400 Amp. in
single-phase.
SHZV structure is the combined type and is composed of diverter switch and tap selector.SHZV is installed on
the top cover of transformer by its head flange, and connected to SHM-III motor drive unit through the upper
gear box on the cover of OLTC, bevel gear (auxiliary devices) and driving shaft (horizontal & vertical), realizing
the switching operation of OLTC by motor or remote control.

This operation instruction includes all the necessary information for the installation and operation of SHZV
OLTC. The structure is subject to change without notice.

Designation of the tap changer model number

 

The operating condition of OLTC

a. The temperature of oil in which the tap changer operates is - 25ºC ~ 100ºC .

b. The ambient temperature under which the tap changer operates is - 25ºC ~ 40ºC .

Technical Data of Type SHZV

Mechanical operating principle of the tap changer

Tap change operation begins with the motor of motor drive unit, the driving force is transmitted to the bear gear
box through the vertical driving shaft, then transmitted to the retarding mechanism on the head flange via the
horizontal driving shaft, and its output shaft drives the insulation shaft rotate. The rotation of insulation shaft
then drives the main driving system to operate the spring accumulation mechanism (the energy released from
the energy-storing mechanism drives the diverter switch operate), and the Geneva wheel mechanism of tap
selector, the rotating of Geneva wheel mechanism makes the singular or dual moving contact of tap selector
rotate one operating position.

Maintenance period

1.Maintenance should be carried on every 300,000 operations of tap changing.

2.Diverter switch should be replaced after 800,000 operations.

3.Maintenance should be carried on tap selector after 800,000 operations.

4.The maintenance of the tap changer is normally performed by Huaming. And usually the maintenance can be
finished within one day.