RAJKIYA ENGINEERING COLLEGE,
SUMMER TRAINING FROM UPPCL
33/11 KV SUB-STATION BASTI (U.P.)
PRESENTED BY : SUBMITTED TO :
DIGVIJAY PAL MR. NITISH KR. YADAV
ROLL NO.-1473720014 (ASST. PROF. EE DEPT.)
SINGLE LINE DIAGRAM
CONCEPT OF BUS
EQUIPMENTS AT BUS STATION
PARTS OF TRANSFORMER
TESTING IN TRANSFORMER
WHAT IS A SUBSTATION ?
A substation is a part of an electrical generation,
transmission, and distribution system. Substations
transform voltage from high to low, or the reverse,
or perform any of several other important
functions. Electric power may flow through several
substations between generating plant and
consumer, and its voltage may change in several
SINGLE LINE DIAGRAM
Single Line Diagrams do not show the exact
electrical connections of the circuits. As the
name suggests, SLDs use a single line to represent
all three phases. They show the relative electrical
interconnections of generators, transformers,
transmission and distribution lines, loads, circuit
breakers, etc., used in assembling the power
system. The amount of information included in
an SLD depends on the purpose for which the
diagram is used.
CONCEPT OF BUS
1. The concept of bus is Same as the
concept of a node in an electrical circuit.
2. There is one bus for each phase.
3. Shown in SLDs as lines connecting
equipment to the buses.
4. Made of aluminum or copper bars or
pipes and can be several meters long.
5. The impedance of buses is very low,
practically zero, so electrically the whole
bus is at the same potential.
EQUIPMENTS AT THE
A) CURRENT TRANSFORMER
B) POTENTIAL TRANSFORMER
B) CIRCUIT BREAKER
D) LIGHTNING ARRESTOR
1. Transformer Tank
2.High Voltage Bushing
3. Low Voltage Bushing
5. Cooling Fans
6. Conservator Tank
7. System Ground Terminal
8. Drain Valve
11. Bushing Current
12. Control Panel
13. Surge Arresters
PARTS OF THE TRANSFORMER
It is just like a switch is
used to make sure that
an electrical circuit can
be completely de-
energized for service or
Difference b/w Isolator
and circuit Breaker
The major difference
between an isolator and a
circuit breaker is that an
isolator is an off-load device
intended to be opened only
after current has been
interrupted by some other
1.The basic functions of circuit breaker is protection, which is
interruption of short-circuit and overload fault currents.
2. High-voltage breakers are nearly always solenoid-operated, with
current sensing protective relays operated through current
High-voltage breakers are broadly classified by the medium used to
extinguish the arc.
A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur
hexafluoride gas to quench the arc. They are most often used for
transmission-level voltages and may be incorporated into compact gas-
Sulfur hexafluoride (SF6) high-voltage circuit-breakers
A protective relay is an
electromechanical apparatus, often
with more than one coil, designed to
calculate operating conditions on an
electrical circuit and trip circuit
breakers when a fault is detected.
The most common form of protection
on high voltage transmission systems is
distance relay protection. Power lines
have set impedance per km. and using
this value and comparing voltage and
current the distance to a fault can be
1. A lightning arrester is a device used on electrical power systems to
protect the insulation and conductors of the system from the damaging
effects of lightning.
2. When a lightning surge travels along the power line to the arrester,
the current from the surge is diverted through the arrestor, in most
cases to earth.
CURRENT TRANSFORMER AND POTENTIAL
1. Current transformers, together with potential transformers (PT) are
known as instrument transformers.
2. When current in a circuit is too high to
directly apply to measuring instruments,
a current transformer produces a reduced
current accurately proportional to the
current in the circuit, which can be
conveniently connected to measuring and
Potential Transformer or Voltage
Transformer are used in electrical power
system for stepping down the system
voltage to a safe value which can be fed
to low ratings meters and relays.
Commercially available relays and
meters used for protection and
metering, are designed for low voltage.
Main components of a
•Primary and secondary windings
•Insulation of windings
•Expansion tank or conservator
•Tank , oil , cooling arrangement ,
temperature gauge, oil gauge
•Silica gel breather
(1) MAGNETIC CORE
•Magnetic core consists of an iron core. The core is laminated and made of
•Thickness varies from 0.35mm to 0.5mm.
•Laminations are insulated from each other by coating then with a thin coat
•Various types of stampings and laminations employed in the construction
There are two types of transformer cores ,they are
(a) Shell type (b)Core type
Shell type – Two windings are carried by central limb. Core is made up of E
and I stampings and has three limbs. Has two parallel paths for magnetic
Core type- Has two limbs for two windings and is made up of two L-type
stampings. Has only one magnetic path.
•There are two windings in a transformer.
•They are primary and secondary windings.
•Made up of copper.
(3) Insulating oil
•The coil used in transformer protects the paper from dirt and moisture and
removes the heat
produced in the core and coils,
•It also acts as insulating medium.
Oil must possess following properties:
•High dielectric strength
•Free from inorganic acid , alkali and corrosive sulphur.
•Low viscosity to provide good heat transfer.
• Good resistance to emulsion so that the oil may throw down any moisture entering
instead of holding it.
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