Voltage Transformers are induction type
and are contained in their own SF6 compartment, separated from the
other parts of the installation.
The active portion consists of a
rectangular core, upon which are placed the secondary windings and the
high voltage winding.
Provision is made for up to two
secondary windings for measurement and an additional open delta winding
for earth fault detection.
A synthetic film separates the different wraps of the windings. The Transformers can be installed Any where on the substation.
For rated voltage up to 145
kV inductive Transformer with cast resin coil For rated voltage of
245 kV inductive VT with SF6 gas as main insulation. For 300 kV and
above, Capacitive Voltage Transformers are preferred Inductive type
The single-pole inductive type Voltage Transformers (Fig. 1) can be
mounted either vertical or horizontal. They are connected to the
Switchgear with the standardized connecting flange via a barrier
The primary winding is insulated with SF6 gas and connected to the HV.
by a flexible connection. The primary winding (2) surround the core on
which the secondary windings (1) are also wound.
The connection between the secondary winding and the terminals in the
external terminal box is made through a gas tight multiple bushing.
The Transformers are equipped with two metering windings and one
tertiary winding for earth-fault protection.
In Switchgear for voltage
above 300 kV, Capacitor Voltage Transformers are also employed. Two
systems are available:
- Transformers with high capacitance
connected to an intermediate Transformer. The oil-insulated capacitor of conventional
design is accommodated in an
enclosure filled with SF6 gas.
The high-voltage connection to the GIS is made through
barrier insulator. The low-voltage choke and the
intermediate Voltage Transformer are housed separately in a cabinet
on the earth potential side.
- Transformers with a low capacitance
accommodated in the current Transformer or in a separate housing,
connected to an