1. BY: Ashok khoja
AT 132 KV GSS
NEEM KA THANA

2. • GENERAL DISCUSSION ON SUB STATIONS
• SINGLE LINE DIAGRAM
• COMPONENTS USED
• ISOLATERS
• BUSBARS
• CIRCIUT BREAKERS AND ITS CLASSIFICATION
• POWER TRANSFORMERS AND ITS MAIN PARTS
• INSTRUMENT TRANSFORMERS
• CURRENT TRANSFORMERS
• BUCHOLZ RELAY
• EARTHING
• POWER LINE CARRIER COMMUNICATION

3. Substation:- A station is a subsidiary station of an
electricity generation, transmission, & distribution system
where voltage is transformed to high to low or the reverse
using transformers.
A substation generally have switching, protection, & control
equipment & one or more transformers.
Types:-
(a) Transmission substation
(b) Distribution substation
Transmission substation connects two or more
transmission lines.
Distribution substation transfers power from transmission
system to the distribution system of an area.

5. COMPONENTS USED
• ISOLATERS
• CIRCIUT BREAKERS
• INST. TRANSFORMERS
• RELAYS

6.  Isolators are designed to open a ckt under n0 load. Its
main purpose is to isolate portion of ckt from the
other & is not intended to be opened while current is
flowing in the line.
 There are two types of isolators:-
 off load isolators
 on load isolators

7. DEFINITION:- A bus bar is a conducting bar that
carries heavy currents to supply several electric
circuits.
When a no. of generators or feeders operating at the
same voltage level to be directly connected electrically,
busbar are used as the common electrical component.
Bus bars are copper rod or thin walled tubes and
operate at constant voltage.
TYPES OF BUSBARS:-
 Main busbar
 Auxiliary busbar
One busbar is main busbar & another is spare or auxilary
busbar.

8. A circuit breaker is a piece of equipment which can:-
 break a ckt automatically under fault conditions.
 make a ckt either manually or by remote control
under fault conditions.
PRINCIPLE:- A ckt breaker essentially consists of
fixed & moving contacts, called electrodes under
normal operating conditions, these contacts remain
closed & will not open automatically until & unless the
systems becomes faulty. When a fault occurs on any
part of the system, the trip coils of the breaker get
energised & the moving contacts are pulled apart by
some mechanism. Thus opening the circuit.

9. CLASSIFICATION:-
 oil circuit breakers
 Sulphur Hexa Fluoride circuit breakers
 Air-Blast circuit breakers
 vaccum circuit breakers
Under training SF6 type, vaccum ckt breaker & Air-
Blast ckt breakers were used in the GSS.

11. Transformer is an electrical machine which works on
the principle of electromagnetic induction. It transfers
electric power from one electric ckt to other with the
help magnetic path(flux) on constant frequency but
equal or different current voltages. For this purpose
two sets of insulated windings are wounded on a close
terminated steel core. The winding which is connected
to the supply is called primary winding & that winding
is connected to the load is called secondary winding.

12. MAIN PARTS OF POWER
TRANSFORMERS:-
a) core
b) Winding(H.V winding, L.V winding, tertiary
winding)
c) Tap changer
d) Tank
e) Conservator
f) Air cell
g) Buchholz relay
h) Dehydrating breather
i) Oil temperature indicator
j) Winding temperature indicator

14. Instrument transformers are used for measurement
and protective applications together with equipments
such as meters & relays.
The lines in a station are operated at high voltages and
carry currents of thousands of amperes. The
measuring and protective devices are designed for low
voltage generally 100v and currents about 5A, therefore
they will not work satisfactory if mounted on the
power lines. This difficulty can be overcome by using
instrument transformers, which will step down the
voltages and currents to the convenient level for the
operation of measuring instruments & relays.

15.  C.T. is an instrument transformer used for protection &
metering of high values of currents. C.T. is used for
reducing a.c from higher to lower value for
measurement/protection/control. There are two classes of
C.T:
 protective C.T
 measuring C.T
 Protective C.Ts are used for over current protection, earth
fault protection, differential protection& impedence
protection, etc.
 Measuring C.Ts are used with ammeters, wattmeters, KV
meters & KWH meters for reducing line.

17. Potential transformers are instrument transformers. They
have a large number of secondary turns and a fewer
number of primary turns. They are used to increase the
range of voltmeters in electrical substations and generating
stations.
These are also called as voltage transformers used for line and
circuit protections.

19. Definition:- Buchholz relay is a gas actuated relay. It
can only be fitted to the transformers equipped with
conservator tanks as it is installed in b/w the
conservator tank and the main tank i.e., the pipe
connecting the two.
Principle:- Whenever a fault occurs inside the
transformers, the oil of the tank gets overheated and
gases are generated.
The heat generated by the high local current causes the
transformer oil to decompose and produce gas which
can be used to detect the faults.

20. Operation:- When a fault occurs, heat is produced
due to current leakage, some of the oil in the
transformer tank evaporates and some vapours
collect in the top of the chamber while passing to
conservator tank. When a predetermined amount
of vapours accumulate in the top of the chamber,
the oil level falls, and so closes the alarm circuit of
the relay and rings the bell. Thereby the operator
knows that there is some fault occurred in the
transformer.

22. Connection of an electric equipment to the earth
with the help of connecting rod or wire of
negligible resistance is known as earthling.
Methods of earthling arrangements at 132
kv GSS:
 pipe earthling
 plate earthling

24. For exchange of datas and transfer message between
grid substation, voice communication is necessary.
for this purpose high frequency carrier current is
transmitted on same transmission line on which
power is transmitted.
Hence such communication is called “power line
carrier communication’’.