1. SIX MONTHS INDUSTRIAL TRAINING
UNDERTAKEN
AT
33/11 KV SUBSTATION
IN
JUBILANT LIFE SCIENCES LIMITED
Bhagwanpur ,Rookee,Haridwar

2. 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
steps.

3. 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.

5. 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.

6. EQUIPMENTS AT THE
SUBSTATION
1.MAJOR
EQUIPMENT:
POWER TRANSFORMERS
2.MEASURING
INSTRUMENTS:
A) CURRENT TRANSFORMER
B) POTENTIAL TRANSFORMER
3.PROTECTING DEVICES:
A)
B)
C)
D)
ISOLATOR
CIRCUIT BREAKER
RELAY
LIGHTNING ARRESTOR

7. OTHER ELEMENTS:
A)
B)
C)
D)
E)
CONDUCTORS AND CABLES
CAPACITOR BANK
CONTROL BATTRIES
BUS BARS
WAVE TRAP

8. POWER TRANSFORMER
The substation has the two 220/66 KV step down power transformers (100
MVA) installed made by BHEL and ABB and two 66/11 KV step down power
transformer (20 MVA) made by ECE and TA.
WHAT IS A POWER TRANSFORMER ?
Transformer is a vital link in a power system which has made possible the
power generated at low voltages (6600 to 22000 volts) to be stepped up to
extra high voltages for transmission over long distances and then
transformed to low voltages for utilization at proper load centers.
With this tool in hands it has become possible to harness the energy
resources at far off places from the load centers and connect the same
through long extra high voltage transmission lines working on high
efficiencies. At that, it may be said to be the simplest equipment with no
motive parts. Nevertheless it has its own problems associated with
insulation, dimensions and weights because of demands for ever rising
voltages and capacities.

9. PARTS OF THE TRANSFORMER
1. Transformer Tank
2.High Voltage Bushing
3. Low Voltage Bushing
4.Cooling Fins/Radiator
5. Cooling Fans
6. Conservator Tank
7. System Ground Terminal
8. Drain Valve
9.Dehydrating breather
10. Oil
Temperature/Pressure
gauges
11. Bushing Current
Transformers
12. Control Panel
13. Surge Arresters

10. 2. ISOLAOTRS
It is just like a switch is
used to make sure that
an electrical circuit can
be completely deenergized for service or
maintenance.
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
control device.

11. CIRCUIT BREAKER
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
transformers.
High-voltage breakers are broadly classified by the medium used to
extinguish the arc.
1.Bulk oil
2.Minimum oil
3.Air blast
4.Vacuum
5.SF6
Sulfur hexafluoride (SF6) high-voltage circuit-breakers
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 gasinsulated switchgear.

12. RELAY
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.
DISTANCE RELAY
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
determined.

13. LIGHTNING ARRESTOR
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.

14. CURRENT TRANSFORMER AND POTENTIAL
TRANSFORMER
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
recording instruments.
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.

15. CAPACITOR BANK
A capacitor bank is a grouping of several
identical capacitors interconnected in
parallel or in series with one another.
These groups of capacitors are typically
used
to
correct
or
counteract
undesirable
characteristics,
such
as power factor lag or phase shifts
inherent in alternating current (AC)
electrical power supplies.
CONTROL BATTERIES
Generally we gave dc supply to the
all protective equipment like
relays ,indicators , and for all
controlling devices through
batteries in substation .

17. the
Transformer
"the heart of the alternating current system"
- William Stanley
Jr.

19. POWER
TRANSFORMERS

20. PARTS OF THE TRANSFORMER
1. Transformer Tank
2.High Voltage Bushing
3. Low Voltage Bushing
4.Cooling Fins/Radiator
5. Cooling Fans
6. Conservator Tank
7. System Ground Terminal
8. Drain Valve
9.Dehydrating breather
10. Oil
Temperature/Pressure
gauges
11. Bushing Current
Transformers
12. Control Panel
13. Surge Arresters

21. Main components of a
transformer are:
•Magnetic core
•Primary and secondary windings
•Insulation of windings
•Expansion tank or conservator
•Tank , oil , cooling arrangement ,
temperature gauge, oil gauge
•Buchholz relay
•Silica gel breather

22. (1) MAGNETIC CORE
•Magnetic core consists of an iron core. The core is laminated and made of
silicon steel.
•Thickness varies from 0.35mm to 0.5mm.
•Laminations are insulated from each other by coating then with a thin coat
of varnish.
•Various types of stampings and laminations employed in the construction
of transformers.
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
flux.
Core type- Has two limbs for two windings and is made up of two L-type
stampings. Has only one magnetic path.

23. (2) Winding
•There are two windings in a transformer.
•They are primary and secondary windings.
•Made up of copper.
(3) Insulation
•Paper is still used as basic conductor insulation.
•For power transformers enamelled copper with paper insulation is also used.
(4) 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
the tank
instead of holding it.

24. (5)EXPANSION TANK or Conservator
•A small auxiliary oil tank mounted above
the
transformer and connected to main tank by a
pipe.
•Its function is to keep transformer tank full
of oil.
(6)TEMPERATURE GAUGE
•Is to indicate hot oil or hottest spot temperature.
•It is self contained weather proof unit made of
alarm contacts.

25. (7) OIL GAUGE
•Every transformer is fitted with an oil gauge to indicate
the oil level
present inside the tank.
•It is provided with an alarm contact which gives an
alarm when the
oil level drops beyond permissible height due to oil leak
or due to any
other reason.
(8) BUCHHOLZ RELAY
•First warning that fault is present is given by
presence of bubbles in oil.
•It gives an alarm in case of minor fault and to
disconnect transformer
From the supply mains in case of severe faults.

26. (9) Breather
•It is a chamber which prevents entry of moisture
inside the transformer tank.
•It is filled with drying agent such as calcium chloride or silica gel.
•This absorbs moisture and allows dry air to enter transformer tank. It
is replaced regularly.

27. CLASSIFICATION OF TRANSFORMERS
Transformers are classified on basis of
1.Duty they perform
2.Construction
3.Voltage output
4.Application
5.Cooling
6.Input supply
Duty they perform
I.Power transformer – from transmission and distribution
II.Current transformer- instrument transformers
III.Potential transformer- instrument transformers
Construction
I.Core type transformer
II.Shell type transformer
III.Berry type transformer
Voltage output
I.Step down transformer(Higher to Lower)
II.Step up transformer(Lower to Higher)
III.Auto transformer(Variable from ‘0’ to rated value)

28. Application
I.Welding transformer
II.Furnace transformer
Cooling
I.Duct type transformer
II.Oil immersed transformer
self cooled
Forced air cooled
Water cooled
Forced oil cooled
Input supply
I.Single phase transformer
II.Three phase transformer
star- star
Star-delta
Delta-delta
Delta-Star
Open- Delta
Scott connection

29. EMF EQUATION OF TRANSFORMER
Wkt, T=1/f
Average emf (e)= dΦ/dt
dΦ = Φm
dt = 1/4f
Average rate of change of flux= Φm / (1/4f) = 4f Φm volts
Average emf induced per turn = Average rate of change of flux= 4f Φm
volts
Form factor = RMS value/ Average value = 1.11
RMS value= Form factor x Average value
=1.11 x Average value
RMS value of emf induced/turn = 1.11 x 4f Φm = 4.44 f Φm volts
Primary and Secondary winding having N1 and N2 turns.
RMS value of emf induced Primary winding, E1 = 4.44 f Φm N1 volts
RMS value of emf induced Secondary winding, E1 = 4.44 f Φm N2 volts

30. TRANSFORMER RATIO
For an ideal transformer, E1 = V1 and E2 = V2
There is no voltage drop in the windings.
V1 I1 = V2 I2
V2 / V1 = E2 / E1 = I1 / I2 = N2 / N1 = K
V2 / V1 = K -> Voltage ratio
E2 / E1 = K -> Transformation ratio
N2 / N1 = K -> Turns ratio
I1 / I2 = K -> Current ratio
(i)If K > 1 , then the transformer is called step-up transformer.
(ii) If K < 1 , then the transformer is called step-down transformer.

31. RATING OF TRANSFORMER
•The rating of transformer is expressed by Volt- Ampere (VA)
•Cu loss depends on Current (A)
•Iron loss depends on Voltage (V)
•Total loss depends upon Volt- Ampere (VA)
•It is independent of Load power factor cos Φ.

32. Ideal transformer
Ideal transformer has following properties :
•No winding resistance i.e., purely inductive
•No magnetic leakage flux
•No cu loss
•No core loss
•Ideal transformer secondary is open. Ac supply is connected to primary
winding. Current flows through primary winding. This current is called
MAGNETISING CURRENT (Iμ).
•Value of Magnetising current is small. The Magnetising current produces an
alternating flux (Φ).
•Iμ and Φ are in-phase. This changing flux links primary with secondary
winding.
•Due to alternating flux a self-induced emf (E1) is produced in primary
winding which is equal to and in opposition with V1. It is known as counter
emf or back emf of primary winding.
•Induced emf E2 is produced in secondary winding because of alternating flux
linking with secondary winding. This emf is known as mutually induced emf.

33. PRACTICAL TRANSFORMER ON NOLOAD
If the primary winding is connected to alternating voltage and
secondary winding is left open then transformer is said to be on NOLOAD. Since secondary is open this current is called no-load primary
current (Io).
No load input power, P0= V1 I0 cos Φ0
Active or working or iron loss or wattful component (Iw) which is inphase with ‘V1’ and supplies iron loss and small amount of primary cu
loss.
Iw = I0 cos Φ0
Where, cos Φ0 is no load power factor.
Reactive or magnetizing or wattles component Iμ
which is in quadrature with V1 and its function is to sustain flux in core.
Iμ= I0 Sin Φ0

34. TRANSFORMER ON LOAD
When the secondary winding is connected to load then the transformer
is said to be on load.
Phase angle between V2 and I2 depends on type of load.
Resistive = I2 in-phase with V2
Load Inductive = I2 will lag V2
capacitive= I2 will lead V2
When transformer is loaded,
Flux is constant at no-load as well as at loaded condition, therefore
transformer is called as constant flux apparatus.
Total primary current will be vector sum of I0 and I2’

35. Transformer winding resistance
In practical transformer the winding have some resistances. Primary winding has
primary resistance(R2).
Transformer winding leakage reactance
Primary leakage flux(ΦL1) – All the flux generated by the
primary winding does not link with secondary winding. Some part of flux passes
through air rather than around the core. This flux is in-phase with I1.
Secondary leakage flux(ΦL2) – Leakage flux is set up in
secondary winding. This flux induces eL2 in secondary winding. This flux ΦL2 does
not link with primary is also in-phase with I2.

37. OPEN CIRCUIT / NO-LOAD TEST ON TRANSFORMER
PURPOSE OF THIS TEST IS TO DETERMINE
•Core loss or Iron loss Or Magnetic loss (Pi)
•No load current (I0)
•Shunt branch parameters R0 and X0
One of the winding is kept open.
•Rated voltage at rated frequency is applied to other(LV) winding.
•A voltmeter, wattmeter, and an ammeter are connected in LV side of the
transformer.
Ammeter > Reads No-Load Current, I0
Voltmeter > Reads Applied Voltage, V0
Wattmeter> Reads No-Load Input Power, W0 or P0

38. DETERMINATION OF EQUIVALENT CIRCUIT CONSTANTS
THROUGH NO- LOAD TEST
No load power factor, CosΦ0 = W0 / V0 I0
Core loss component, Iw = I0 CosΦ0
Magnetising component, Im = I0 SinΦ0
Core Loss, Pi = No load power (W0)
Core loss resistance, R0 = V0 / Iw = V0 / I0 CosΦ0
Magnetising reactance, X0= V0 / Im = V0 / I0 SinΦ0

39. SHORT CIRCUIT / IMPEDANCE TEST ON
TRANSFORMER
PURPOSE OF THIS TEST IS TO DETERMINE
•Z01 or Z02 – Total impedance referred to either primary or secondary side
•R01 or R02- Total resistance referred to either primary or secondary side
•X01 or X02- Total reactance referred to either primary or secondary side
•Full load cu loss I22 R02
In this test one of the winding is short circuited by thick conductor.
Current rating of HV side is low compared with LV side.
Power input gives total cu loss at rated load.
Unity power factor wattmeter is used for measuring power in SC test.

40. DETERMINATION OF EQUIVALENT CIRCUIT CONSTANTS THROUGH
LOAD TEST
SC power factor, CosΦsc = Wsc / Vsc Isc
Resistance of transformer referred to primary side , R01 =
Wsc / (Isc)2
Impedance of transformer referred to primary side, Z01 =
Z01 Cos Φsc= Vsc / Isc