6. SPECIFICATION OF THE POWER
TRANSFORMER
Manufactured by ABB
Voltage Ratio- 220/66 KV
Class OF/AF Transformer
Rating- 100 MVA
7. LIGHTENING ARRESTOR ( THYRITE
TYPE)
Thyrite type Lightening
arrester consist of:
Series spark gap
Non- linear resistor
disc in series
(These discs are of
15cm diameter and19
mm thickness)
9. CIRCUIT BREAKER
Vacuum circuit breaker
Are quenching medium- vacuum
voltage range- 3.3- 33 KV
breaking capacity - 250-2000 MVA
SF6 Circuit Breaker
ARC quenching medium – SF6 gas at 5kg pressure
Voltage range- 3.3- 765 KV
Breaking capacity- 1000- 50,000 MVA
10. ISOLATOR
Isolators are employed only for isolating
circuit when the current has already
been interrupted.
They operate under no load conditions
and are employed on both the side of
the circuit breaker.
Isolator consist of insulator posts
mounted on a support.
There are fixed and moving contacts
each made of aluminium.
12. EARTHING AT 220 KV SUB
STATION,
DHANDARI KALAN-1
The earthing system consist of an array of conductors
buried horizontally at the depth of 0.5m Such earthing is
called an earthing grid or earth mat.
The main steps in the design of the earthing grid are as
under:
1.Selection of material and size of the conductor of the
grid.
2. Arrangement of the grid conductors.CC
3. Connections to the grid.
13. WAVE TRAP
It is the effort to utilize the same transmission line
between two substations for the purpose of
communication.
It does the trapping of high frequency communication
signals.
Itv is relevant in PLCC system for communication
among various sub stations.
The wave trap offers high impedance to the high
frequeny communication signals.