Department of ECE
ROLL NO: 1149178
AT 220 KV SUBSTATION,
The project will lose all its glittering if I don’t think the people without Whose
united effort I couldn’t have completed my training. To accomplish this is rather a
difficult task and is not possible for everyone but the Support and co-operation I got
here at the 220 KV Sub-Station, Ferozepur Road was over-whelming.
I express my sincere and whole hearted sense of gratitude to the Staff of sub-station,
Ferozepur Road especially to Er. Fateh Singh (SSE) for giving me an opportunity of
undergoing my six Week’s industrial training. I am also grateful to Er. Anil Kumar
Sharma (JE) under whose guidance I completed my training. He always helped me to
avail Maximum facilities, full assistance and guidance. I would also like to make specific
mention of substation staff that indirectly involved in this project and have been there for
me, my sincere Thanks and word of appreciation to them. I am obliged to all my
Friends for their frantic attitude and co-operation during the course of my training. I
would like to express a great deal of gratitude towards my institution (Gulzar
Group Of Institute ,Libra, Khanna) for Allowing availing the wonderful and learning
opportunity of undergoing6 weeks Training at 220 KV Sub-Station, Ferozepur Road,
220 KV Ferozepur Road Sub-Station is situated at a prime locality of the city. The Sub-
Station has a yard of 21427 sq. yard where five transformers, line isolators, bus-bars,
current transformers, minimum oil circuit breaker, lightening arresters are installed and
all these are controlled from panels which are placed inside the sub-station. During
the training period June and July, The sub-station received units 19663282 and
delivered units 19680929 on 11KV side to the consumers which show that the losses
on the equipments installed are properly maintained and employees are efficient
in their work.
Energy is the basic necessity for the economic development of a country. Many
Functions necessary to present-day living grind to halt when the supply of energy of
energy stops. The availability of huge amount of energy in the modern times has
resulted in shorter working day, higher agriculture and industrial production.
As a matter of fact, there is a close relationship between the energy used per person
and his parcel of our life.
Energy exists in different forms in nature but the most impotent form is the Electrical
energy. The modern society is so much dependent upon the use of electrical energy
that it has become a part and parcel of our life.
IMPORTANCE OF ELECTRICAL ENERGY:
Energy may be needed as heat, as light, as motive power etc. The present day
advancement in science and technology has made it possible to convert electrical
energy into any desired form. This has given electrical Energy a place of pride in
modern world. The survival of industrial undertaking and our social
structures depends primarily upon low cost and uninterrupted of electrical energy.
Electrical energy is superior to all other forms due to the following reasons:
Convenient form: Electrical Energy is a very convenient form of energy.
It can be easily converted into other forms.
Easy Control: The electrically operated machines have simple and convent
starting, control and operation. For instance, an electric motor Can be started or
stopped by turning on or off a switch. Similarly, with simple arrangements, the
speed of electric motors can be easily varied Over the desire range.
Greater Flexibility: One important reason for preferring electrical
energy is the flexibility that it offers. It can be easily transported from
One place to other with the help of conductors.
Cheapness: Electrical Energy is much cheaper than other forms of energy.
Thus it is overall economical to use this form of energy for domestic, commercial
and industrial purposes.
Cleanliness: Electrical energy is not associated with smoke, fumes or poisonous
gases. Therefore, its use ensures cleanness.
High transmission efficiency : The consumes of electrical energy are
Generally quite away from the centers of its productions. The Electrical energy
can be transmitted conveniently and efficiently from the centers of generations
to the consumers with the help of overhead conductors known as transmission
TYPES OF SUB-STATIONS
A Transmission Sub-Station is one whose main purpose is to connect various
transmission lines. The simplest case is where all transmission lines have the same
voltage. In such cases, the sub-station contains high voltage switches that allow lines to
Be connected together or isolation for maintenance. Transmission sub-station can
range from simple to complex. A small switching Station may be little more than a bus-
bar plus some circuit breakers. The largest transmission sub-station can cover a
larger area (several acres/hectares) with voltage levels and a large amount of protection
and control equipment (capacitors, relays, switches, breakers and voltage and current
A Distributed Sub-Station is one whose main purpose is to transfer power
from transmission system to the distribution system of some area. It is
Uneconomical to connect electricity consumers to main transmission
Networks (unless they use large amount of energy) so distribution station
reduces voltage to a value for connection to local loads.
Besides transforming the voltage, the job of distribution sub-station is to
Isolate faults in either the transmission or distribution system. Distribution
Sub-station may also be the points of voltage regulation, although on long
Distributed circuits, voltage regulation equipment may also be installed
Along the line.
220 KV SUB-STATION
(FEROZEPUR ROAD LUDHIANA)
This sub-station is situated at the bank of Sidhwan canal, on Ferozepur road, opposite
milk plant Ludhiana. This is PSTCL concerned ; it has 5 power transformer. Two of
220/66kv, 160MVA, 100MVA, one of 66/11kv 20 MVA and 2no’s of 66/11kv 16/20 MVA
which controls 66kv &11Kv supply. The Incoming supply of 220 Kv is received from 220
Kv ‘HUMBRAN” substation And 1 circuit from 220Kv ‘LALTON’ which are under P & M
i.e. protection And maintenance circle. This substation supplies 11 Kv to various
localities Area of Ludhiana. It also controls or supplies 66Kv to Model town, Haibowal,
D.C.Complex, PAU, Rajguru nagar and G.T. Road which Supplies 11Kv to areas
following under these substations. Ferozepur road Main controls the supply of
Sarabha Nagar, Agar Nagar, Bharat Nagar, Gurdev Nagar, B.R.S Nagar. There are
some essential and independent Feeders which supply electricity to milk plant feeders.
This sub-station is controlled by SSE Ferozepur Road PSTCL Ludhiana. Er. Fateh
Singh is sub-station engineer. All the power cuts and other Messages related to
power control ‘Patiala’ and are further delivered to Local sub-station for further
implementation of power cut in various areas Controlled by these sub stations.
LINE ISOLATERS CUM EARTH SWITCH:
This isolators is directly connected with incoming supply line of sub-station. In The staff
of the sub- station wants to work in this isolator, the line isolator Should be in open
position and line should be cut from feeding station.
C.T.’s are installed as per required load of the sub-station which varies from One station
MINIMUM OIL CIRCUIT BREAKER’s/SF6 BREAKERS:
There are two types of breakers used at this sub-station. One is MOCB and other is gas
filled circuit breakers i.e. SF6 breaker. It Works as a switch which can be operated ON
and OFF load. Arc is produced in the breaker while operation is quenched with the help
of oil and gas.
L.A.’s are provided under the line before and after the apparatus to protect The
equipment from lightening. The search counters are provided to record /count the
lightening search. It works as per capacity of the line device, it blocks 66Kv voltage and
the Excessive voltage goes to the earth through lightening arrestors.
Incoming 220kv Incoming 66kv
1 Lalton 1 Hambran
2 Hambran 2 South City
Outgoing 220kv Outgoing 66kv
Nil 1 Haibowal
2 Model Town
3 D.C Complex & PAU
4 Rajguru Nagar
1 Sanchar Colony 2 Spare
3 Bharat Nagar 4 Milk Plant
5 GADVASU 6 Agar Nagar
7 Vishal Tower 8 Spare
9 Sunet 10 Tagore Public School
11Mandir Wala 12 Pakhowal Road
13 Colony 14 Sarabha Nagar
15 Model Gram 16 BRS Nagar
17 FMI 18 Country Home
19 Gurdev Nagar 20 Phullanwal
21 Aarti 22 Gurdev Hospital
Instrument transformers are of two types:
1. Current Transformers (C.T.)
2. Potential Transformer
1. CURRENT TRANSFORMERS:
A current transformer is a measurement device designed to provide a current in its
secondary coil proportional to the current flowing in its primary. The ratio of Primary to
secondary current is roughly inversely proportional to the ratio of Primary to secondary
turns. Current transformers are commonly used in metering and protective relaying,
where they facilitate the safe measurement and control circuitry from the circuit being
Electric power distribution systems may require the use of a variety of circuit condition
monitoring devices to facilitate the detection and location of system Multifunction.
Current transformers in electrical substations measure the system currents at
predetermined measuring points of the switchgear with certain predetermined
accuracy. The measuring points are typically located at all incoming and outgoing
lines and also within the system, e.g. For the Bus – bar protection. The current
measuring signals are used for protective Functions, for monitoring the sub-station, for
calculating performance data for operating purposes or for consumption billing and for
the representation on a display. The output of the current transformer provides a
representation of the current flowing through the assembly that is being monitor.
2 POTENTIAL TRANSFORMERS:
The instrument potential transformer (PT) steps down voltage of a circuit to a low value
that can be effectively and safely used for operation of instrument such As ammeters,
voltmeters, watt meters and relays used for various protective purposes. There are
two (2) main windings on every transformer. H.T.winding and L.T. winding. Special oil
proof enameled copper wire is used and wound in layers, each layer being adequately
insulated from the adjacent layers. The L.T. Windings placed adjacent to the core
and is insulated from it, depending upon the requirement, two L.T. Windings can
be provided; one for metering and the other for the protection.
An isolator switch is a part of an electrical circuit and is most often found in industrial
applications. The switch does exactly what its name suggests i.e. isolates electrically,
the circuits connected to it. Such a switch is not used normally as an instrument to turn
on/off the circuits in a way that a light Switch does. Either the switch isolates circuits that
are continually powered or is a key element which enables an electrical engineer to
safely work in the protected circuit.
Isolator’s switches may be fitted with the ability for the switch to padlock Such that
inadvertent operation is not possible. In some designs the isolator switch has the
additional ability to earth the isolated circuit thereby providing additional safety.
Such an arrangement would apply to circuits which inter-connect power distribution
systems where both end of the circuit need to be isolated. Major difference
between isolator and circuit breaker is that isolator is an off-load device, whereas
circuit breaker is an On-load device. Isolator is installed on both sides of a circuit
breaker. They cannot be operated on load. These are essentially off load devices
although they are Capable of dealing with small charging currents of bus-bar and
connections. Isolators are installed for repair purpose. In case of any fault or for
maintenance of circuit breakers or any other device in the sub-station, it’s off position is
A circuit breaker is an automatically - operated electrical switch designed to
protect an electric circuit from damage caused by overload or short circuit. Its
Basic function is to detect a fault condition and by interrupting continuity, to
Immediately discontinues electrical flow. Unlike a fuse, which operates once and then
has to be replaced, a circuit breaker can be reset (either manually or
automatically) to resume normal operation. Circuit breaker are made in varying sizes,
from small devices that protect an individual household appliance up to large
switchgear designed to protect high voltage circuits feeding an entire city.
SF6 Tank Circuit Breaker
MAGNETIC CIRCUIT BREAKER: These are implemented using a solenoid
(electromagnet) that’s pulling force increases with the current. The circuit
breakers contacts are held closed by a latch. As the current in the solenoid
increases beyond the rating of the circuit breaker, the solenoid’s pull
release the latch which then allows the contact to open by spring action. Some
types of magnetic breakers incorporate a hydraulic time delay feature using a
viscous fluid. During an overload, the solenoid pulls the core
Through the fluid to close the magnetic circuit, which then provides sufficient
orca to release the latch?
THERMAL BREAKER: This uses a bimetallic strip, which heats and bends with
increased current, and is similarly arranged to release the latch. This type is
commonly used with the motor control circuits. Thermal breakers often have a
compensation element to reduce the effect of ambient temperature on the
TYPES OF CIRCUIT BRAKERS:
1. (Miniature Circuit Breaker): The rated current for this type is not more than 100 A.
Its trip characteristics are normally not adjustable. It operates on the basic function of
thermal or thermal- magnetic operation.
2. MCCB (Molded Case Circuit Breaker): The rated current for this type is up to 1000
A. It also operates on the basic function of thermal or thermal - magnetic
Operation. Trip current in this case may be adjustable.
3. VCB (Vacuum Circuit Breaker): It has current ratings up to 3000 A. These
breakers interrupt the current by creating and extinguishing the arc in a vacuum
container. These can only be practically applied for voltages up to about 35000 V,
which corresponds roughly to the medium – voltage range of power systems,
vacuum circuit breaker tend to have longer life expectancies between overhaul than
do air circuit breakers.
4. AIR CIRCUIT BREAKERS: It has a rated current of up to10; 000A.Trip
characteristics are often fully adjustable including configuring trip thresholds and delays.
Usually electronically controlled, though some models are microprocessor
Controlled via an integral electronic trip unit. Often used for main power distribution in
large industrial plant, where the breakers are arranged in draw-out Enclosures for ease
5. THERMOMAGNETIC CIRCUIT BREAKERS : This is the type which is found in
most distribution boards, incorporate board techniques with the electromagnetic
Responding instantaneously to large surges in current and the bimetallic strip
responding to less extreme over current conditions.
A lightening arrester is a device used on electric power system to protect the
insulation on the system from the damaging effect of lightening. Lightening
arresters (L.A.) are provided in the line before and after the apparatus to protect the
equipment from lightening. The typical Lightening Arrester also known as Surge
Arrester has a high voltage terminal. When a lightening surge or switching surge
travels down the power system to the arrester, the current from the surge is
diverted around the protected insulation in most cases to earth.
Lightening Arresters or Surge Arresters are always connected in shunt to the
equipment to be protected; they provide a low impedance path for the surge
current to the ground. Whenever the lightening occurs, there is a voltage around some
thousands of voltage appear on line for a fraction of second (25 to 30 Micro
seconds) which is more than enough to damage all the equipment in the Grid connected
to it, so when a lightening arrester is connected then it provides low resistance path
such that all that high voltage is directed towards the earth resulting the protection of all
the equipments connected to the grid
BUS – BAR
A bus- bar is electrical power distribution refers to thick strips of copper or
aluminum that conduct electricity within a switch board, distribution board, sub-station or
other electric apparatus. Bus-Bar are typically either flat strips or hollow tubes as
these allow heat to dissipate more efficiently due to their high surface area to cross-
sectional area Ratio. The skin effect makes AC bus - bars more than about 8 mm
thick in efficient, so hollow or flat shapes are prevented in higher current applications. A
hollow section ha higher stiffness than a solid rod, which allows a greater span
between bus-bar in outdoor switchyard.
VARIOUS ARRANGEMENTS OF BUS-BAR:
There are several bus-bar arrangement that can be used in a substation. The choice of
particular type depends upon various factors such as system, voltage, position of sub-
station, degree of reliability cost etc; the most commonly used bus-bar arrangement in
sub-station are :
1. Single Bus-Bar Arrangement
2. Single Bus-Bar System with Sectionlization
3. Double Bus-Br Arrangement
1. SINGLE BUS-BAR ARRANGEMENT:
This arrangement consists of a single (or three phase) bus-bar to which various feeders
and all incoming and outgoing are connected. The chief advantages of this arrangement
are its low initial cost, less maintenance and its simple operation. This arrangement is
not used for voltage exceeding 33 Kv. The indoor 11 Kv sub-stations often use single
bus-bar arrangement. It however suffers from four drawbacks:
a) If repair is done on bus-bar or a fault occurs in bus, there is a complete
interruption of the supply.
b) Extension of the sub-station without shutdown is not possible.
c) Any fault on the system is fed by all the generating capacity, results in very
d) The bus can’t be cleaned, repaired or tested without de-energizing the whole System.
2. SINGLE BUS-BAR SYSTEM WITH SECTIONISATION:
In this arrangement, single bus-bar is divided into two sections.
Advantage of this section is as under:
a) Repair, maintenance etc on any section, can be carries out by Dee-energizing that
section only, eliminating the possibility of complete shutdown.
b) If the fault occurs on any feeders, the fault current is much lower than with
unsectionized bus-bar, this permits the use circuit breakers of low capacity in feeders.
c) If the fault occurs on any section of the bus-bar that section can be isolated without
affecting the supply from other sections.
3. DOUBLE BUS-BAR ARRANGEMENT:
This arrangement is also known as Duplicate Bus-Bar Arrangement. In large stations, it
is important that breakdown and maintenance should be avoided.
INTRODUCTION TO TRANSFORMER
A transformer is an electrical device which transfers electrical power from one
circuit to another of same frequency. It can raise or lower the voltage in circuit, but
corresponding decrease or increase the current. It consists of two independent
winding wound over r laminated iron core. The winding which is connected to the
source of supply is called primary and other from which the power is delivered is
called secondary. If the voltage of secondary winding is higher than primary, it
is called STEP-UP Transformer. On the other hand, if the voltage of the secondary is
lower than primary, it is called STEP-DOWN Transformer.
Transformer should never be connected to direct current source because if the
primary winding of transformer is connected to a direct current supply mains, the flux
produced will not vary but remain constant in magnitude and therefore no e.g. Will be
induced in secondary winding except at the moment of switching on. Thus the
transformer cannot be employed for raising or lowering the direct current voltage. Also
there will be no back induced e.g. in the primary winding and therefore, a heavy
current will be drawn from the supply mains which may result in the burning of
the burning of the winding. Thus transformer employed on alternate
MAIN PARTS OF TRANSFORMER
1. TRANSFORMER TANK: The tank is used to contain for insulation and core with
winding is called transformer tank.
2. CORE : The core of the transformed r is constructed from laminated sheet or
silicon steel assembled to provide continuous magnetic path. The winding are
placed on the core.
3. CONSERVATIVE TANK : Conservator tank is like a hollow cylinder which is
attached to the transformer body on the top side. Conservator tank is attached to
The transformer body of the transformer through a pipe and contraction of all oil
changes the level in the conservator.
4. OIL LEVEL INDICATOR : With the help of oil indicator we see the level of oil in
transformer tank and conservator without bring away its cover plate of tank always
contacts with the conservator.
5. DRAIN COCK: Drain cock looks like a tap (valve). It is used for bringing oil from tank.
It is attached with tank at its bottom on one side, so that all oil of the tank takes out from
tank with opening the drain.
6. COOLING TUBES: Cooling tubes are always attached to tank by its oil sides to
cooling of transformer. Heating oil flow from its upper hole through it and cools down
with the help of air and through its end bring into tank. Usually, in sub-station summer
days are very hot, so fan pressure air is used for cooling of oil.
7. HIGH VOLTAGES BUSHES: These are insulated gripped with tank. These are used
to give high voltage 220 Kv in sub-station from transmission line from generating
8. LOW VOLTAGE BUSHES : These are used for taking 132Kv, 66Kv etc; for next
transmission to sub-station.
9. EXPLOSION VANT: It is attached next to the top side of transformer body. It is
made in the same way as breather of transformer. If at any time transformer calls
Short circuit because of gases produced in it; it helps in exhaling out the gases.
10. TEMPERATURE GUAGE: It is used for measuring the temperature of transformer
oil time to time.
11. BUCHHOLZ RELAY : This is installed in between the main tank and the oil
conservator. It is a gas relay which gives warning of any fault developing inside the
Transformer and if fault is dangerous, relay disconnects the transformer circuit.
12. WINDING TEMPERATURE GAUGE: It is use to measure the winding
temperature of the transformer. It is further of two type’s i.e. One is L.V. Winding
gauge and other is H.V.Gauge. These measure the temperature of respective windings.
13. BREATHER TANK: It is used to breathe out the moisture from oil circulating in the
transformer windings i.e. it soaks the water content from the oil. It contains
Silica gel , whose color remains blue till it doesn’t contain any moisture and its color
changes from blue to pink when it contains water and this shows that the silica gel has
to be changed from the breather tank.
14. TAP CHANGER: Tap changer is used to regulate the low voltage winding at
accurate level of 11 Kv. When sometimes the voltage from the generating end gets
lowered due to some reasons then the OLTC ( On Load Tap Changer) tap is
changed to regulate that voltage at transmission end by increasing the tap.
It consists of a large number of capacitors in series and parallel combination. They are
installed in sub-station at bus-bar for improving the power factor and removing
the reactive power. Shunt capacitor banks at sub-stations improve power factor and
voltage conditions by supplying leading clovers to transmission and distribution system.
The cause of lagging power factor is used for induction motors, transformers and other
domestic and industrial equipment which draw reactive power and due to it the
receiving of power is decreased and to remove this effect the capacitor bank is used
in the sub-stations so that the whole power factor of line is improved. Thus,
capacitor bank improves the efficiency of sub-station. For a good conditioning of the line
voltage, the power factor is unity.
D.C. supply is very necessary for sub-station. For it is also called “BRAIN OF THE SUB-
STATION”. In human body brain controls the whole process in similar way battery
controls whole process in sub-station. With this supply all tripping circuit work. D.C.
Supply is given to various types of relays and circuit breaker. Equipments in
sub-station have the D.C. supply for their working. If the battery is damaged, so the
various means are provided to protect the battery.
Battery Room in Sub-Station
This sub-station has a battery of 220 volt. It has 110 cells and each has a voltage of 2
volt and a capacity of each cell is 300 A.H. The battery is of lead acid type, the
dielectric strength of battery should be 1200 (27 D.C.). The specific gravity is checked
by hydrometer. If the temperature increases, specific gravity decreases. So the specific
gravity decreases. So the specific gravity measured at particular temperature should be
converted to room temperature by taking p.f. of 0.007 e.g. If we are calculating
specific gravity at 30 degrees is 1100 then temperature difference is 30-24=6
degree. This is then multiplied by 0.00711’s and is added into specific gravity at 30
degrees and in this way die specific gravity at 30 degrees is 1100 at any particular
temperature specific gravity is calculated. If it is less than that is require then it should
S. NO. TEMPERATURE SPECIFIC GRAVITY
1. 20 1204.9
2. 21 1204.2
3. 22 1203.5
4. 23 1202.6
POWER LINE COMMUNICATION
The power system of an organization like PSEB, comprising power Houses, HT Lines &
sub-stations is so complex & expensive that to control the same, an equally large &
complex tele-communication system of high reliability is required. For PSEB, its own
Power Line Carrier (PLC) channel provides the tele-communication system.
The main purpose of PLC is to transmit speech or to convey messages from
one sub-station to a another sub-station through transmission lines at high
frequency. However, power line communication serves other purposes also like tele-
metering, tele-printing etc .A PLC channel consists of two PLC terminals at two PLC
stations A&B connected Together with the help of HT transmission line & coupling
equipments like coupling capacitors, coupling devices & H.F. cable.
Information for the above listed facilities is accepted by one PLC terminals &
passed on its counterparts at remote station in the form of H.F. signals. The
remote PLC terminal delivers the same. In original form , to local users or passers on
the same to adjoining PLC terminal for transmission to next station over the next line
section. Thus, two PLC terminals at two stations communicate with each other.
Equipment Used In Power Line Carrier Communications:
1. WAVE TRAP: Wave Trap contains a main coil, lightening arrestor and a tuning
device. All these are connected in parallel. It offers very low impedance to the power
frequency signal or wave. The lightening arrestors are used to protect the main coil from
high voltages surges. The tuning device is used to block the signal of narrow band
carrier frequency. All the three components of wave trap Immersed in oil and are
enclosed in drum type porcelain container. The waves trap most of them are of hanging
2. COUPLING CAPACITORS: The coupling capacitors used for power line
communication have capacitance ranging from 2200 pf to 10,000 pf. It offers high
Frequency carrier signal and allow them to enter the line matching unit. However,
It offers a high impedance path to low frequency signal or wave and blocks.
Standard lead numbers
J series- J1, J2…………………………… D.C Incoming
K series-K1, K2.K3, K5………………… D.C control circuitry
L series-L1, L2, L3, L4…………………. Alarm & indication
H series-H1, H2, H3, H4………………. L.T a.c supply
E series-E11, E31, E51…………………….. P.T sec circuitry
A series A11,A31, A51……………….. C.T sec. Sp.Prot(Diff/REF)
B series B11,B31,B51………………… “ LBB/Bus-bar
C series C11,C31,C51………………… “ Back-up protc.
D series D31,D31,D51……………….. “ Metering
U series U1,U2,U3……………………… Spare/auxiliary contacts
Relays based on logic
Neutral displacement Relays (NDR)
Restricted E/F (REF) Relays
Over fluxing (O/F) Relays
Distance Protection Relays (DPR)
Local Circuit Breaker Back Up (LBB)
Reverse Power relays
Devices & their nomenclature
2- Time delay relay 51-IDMT O/C relay
3-Inter-locking relay 52-Circuit Breaker
21-Distence relay: Main-1 52a-CB aux N/O (a cont)
121- “ “ Main-2 52b- “ “ N/C (b cont)
25-Check sync. Relay 55-Power factor relay
26T-Oil Temperature trip 59-Over voltage relay
27-Under Voltage relay 60-Voltage or current relay
30-Annunciator 63T-Bucholz relay
46-Negative phase seq.relay 64-Instantaneous E/F
49-Thermal relay 67-Directional relay
50-Instant. O/C (HSU) 74- Alarm relay
81-Frequency relay 163T-OLTC Bucholz relay
86-Master relay 49T-Wdg. Temperature trip
87NT-REF relay 26A-Oil Temperature Alarm
95,195,295-Trip ckt/Master relay supervision96-Bus Bar differential
99-Over-Flux relay 162-Pole discrepancy relay
186A &B-Auto reclose relay 85-Carrier receive relay
Nomenclature for panels
C&R panel Control &Relay
DCDB D.C distribution board
ACDB A.C distribution board
Duplex Two parts e.g.-control & relay panel sept.
OLTC On load tap change
RTCC Remote tap changer control panel for OLTC
A Represents 220kv voltage
B “ “ 132kv voltage
C “ “ 66kv voltage
D “ “ 33kv voltage