TRANSFORMER
Name Plate: Indoor type
|
Make
|
Vijay
Elecricals Ltd (Hydrabad)
|
|
Type
|
Dry
type Resin Cast
|
|
Capacity
|
2500
KVA, 2.5 MVA
|
|
No load
Voltage
|
HV:
33000 volts, 33 KV
LV :
433 volts
|
|
Current:
|
HV:
43.738 Amps
LV :
3333.43 Amps
|
|
Type of
cooling
|
AN ( Air Natural)
|
|
Frequency
|
50Hz
|
|
Imp.
Voltage
|
8.76%
|
|
Core,
Coil Assy
|
9830 Kg
|
|
Enclosure
& fitting
|
2320 Kg
|
|
Total
Weight
|
12150
Kg
|
|
Off ckt
Tap changing links
|
+ in steps of 2.5 variation in HV
|
|
Phase
|
3
|
|
Scanner
|
total 8
channels. Alarm – 130oC, Trip 140oC
|
|
Class
of insulation
|
H (180o)
|
|
Vector
gr.(Connection symbol)
|
Dyn11
|
|
Yr of
manufacturing
|
2004
|
|
Insulation
Level
|
HV-Kv :
L1170/AC-70
LV55354-Kv:
AC-3
|
|
Serial No
|
|
|
Guaranteed
max. temperature rise in winding
|
over an
ambient of 45oC-95oC
|
|
Neutral
CT
|
4000/1
|
Dry type Resin cast: Advantage
1.
Improves
earth tracking resistance
2.
High
di-electric strength
3.
Moisture
repellent
4.
Flame
retardant
5.
High
insulation resistance
6.
Easy
for maintenance.
PROTECTION (AUXILIARY RELAY TYPE VAA-ALSTOM)
1.
Over
current
2.
Earth
Fault
3.
Restricted
Earth fault
4.
High
winding temperature protection. ALARM- 1000C, TRIP – 1100C
5.
Door
interlocking
6.
Neutral
displacement relay.
TYPES
OF TRANSFORMER
1.
CORE
type, 2. BERRY type, 3. SHELL type, 4. DISTRIBUTION, 5. Power, 6.
AUTO-TRANSFORMER, 7. SINGLE & THREE PHASE.
In
Transformer/Alternator, star point is earthed because to keep unbalance load
& line voltage constant. So, electrical equipment is safe.
PT PV
SI
Transformer
ratio: ---- =
-------- = --------
ST SV PS
PT:
Primary winding - high turns wire
small/high voltage 33Kv
Secondary winding – low turns wire
thick/low voltage 110 V
CT:
Primary winding – low turns wire max thick / high current 100 Amps
Secondary winding high turns wire thin/
low current 1 Amps
VECTOR GROUP Dyn11
Primary is Delta connected
and Secondary is Star connected. As per Watch minute pointer indicates Primary
Voltage & Hour pointer indicates Secondary voltage. When there is 11
o’clock in the watch it means there is 300 angle between two
pointers. i.e Secondary voltage leads by
300 to primary voltage. When primary voltage leads to Secondary
voltage, it is in anti-clockwise direction of the watch.
WHAT IS POWER FACTOR
Power factor is a cosine
angle between voltage & current.
Resistance is equal to
Impedance R=Z ie. True power = Apparent
power
In AC ckt. V x I is apparent
power & V x I x CosΦ is a true power
EFFECT OF LOW POWER FACTOR
Due to low power factor,
current will increase and so copper loss will increase. If affects in
decreasing the efficiency of the equipments.
Due to low power factor,
voltage regulation of transformers, generators, switches and transmission line
will increase but fault lever capacity will decrease. Due to this, loss of
electricity will take place and for require load we have to increase the
capacity of the equipments. To avoid this we have to provide capacitor bank in
the line which will increase the power factor of the system.
EQUIPMENTS WHICH DECREASES POWER FACTOR:
Pumps, motors which are
running on no load, Tube light, Fan i.e any inductive equipment.
Percentage impedance: 8.76
Ø If 33 Kv supply is give to HT side and
if 3333.33 amps full load current is
flowing then secondary voltage will be 400v in place of 433v ie 8.76% less.
Ø If secondary if short circuited , we are
giving 8.76 v in place of 33kv, then from secondary 3333.33 amp current will
flow.
MOTOR
SQUIRREL
CAGE MOTOR
Advantage Disadvantage
1.
Heavy
duty Low
starting torque
2.
No
rotor winding Starting
current high
3.
On
load, PF is strong on
no load, pf is low
4.
Self
start On
no load – slip decreases, speed decreases On
load, slip increases as stator & rotor speed
depends upon the difference.
VACUUME
CIRCUIT BREAKER (VCB)
|
MAKE
|
Jyoti
Ltd. Vadodara
|
|
Type
|
UY –
30M25
|
|
Rated
frequency
|
50Hz
|
|
Rated
Voltage
|
36000
Volts(36KV)
|
|
Rated
Current
|
1250
Amps
|
|
Ms Level
Imp
|
170KV
P, PF-75 kv
|
|
Rated
Breaking current
|
25 KA
|
|
Rated
Making Current
|
63 KA
peak
|
|
Sr. No.
|
B-242,
Year- 2001
|
|
Supply
Voltage Closing
|
110 VDC
|
|
Supply
Voltage Tripping
|
110 VDC
|
|
Rated
short time current
|
25 KA
|
|
Wt of
Beaker
|
375 Kg
|
|
Standard
|
IS:13118/IEC-56
|
|
Making
Capacity
|
2.55 x
symmetrical ÷ Breaking capacity
|
|
Breaking
Capacity
|
1000 x
106/√3 x 33000
|
ADVANTAGE
OF VCB
1.
They
are compact, reliable and have longer life
2.
There
are no fire hazards
3.
There
is no generation of gas during and after operation
4.
They can
interrupt any fault current. The outstanding feature of a VCB is that it can
break any heavy fault current perfectly just before the contacts reach the
definite ope position
5.
They
require little maintenance and are quiet in operation
6.
They
can successfully withstand lightening surge.
7.
They
have low arc energy
8.
They
have low inertia and hence require smaller power for control mechanism.
9.
DISADVANTAGE OF VCB
1.
Air
chopping/current chopping
2.
Vacuum
leakage cannot be indentified
3.
Costly
MAKING
CAPACITY: Breaker closes
on fault condition, contacts does not damage. Current on which a ckt breaker is
capable of breaking under specified condition.
BREAKING
CAPACITY: Breaking current
capacity of circuit breaker, is the highest value of short circuit current
which a circuit breaker is capable of breaking under specified condition.
In the circuit breaker, breaking capacity
is less than making capacity: When short circuit occurs, there will be voltage
drop. Thus voltage is less, current is also less. So Coil temperature in the
circuit breaker = 800.
We are having OCB.VCB with low resistance
zero common method. For zero method, contact, material is used.
When breaker is switching on & off,
spark takes place & due to hydrogen gas heat produced. To cool this heat
and quenching of arc, vacuum is used.
High Vacuum : 10-5 to 10-8 Tor
PRINCIPLE
OF VACUUM CIRCUIT BREAKER
The production of arc in vacuum circuit
breaker and its extinction can be explains as follows:
When the contacts of the Breaker are opened
in vacuum (10-7 – 10-5 torr) and arc is produced between
the contacts by ionization of metal vapour of contacts. However, the arc is
quickly extinguished because the metallic vapours, electrons and ions produced during arc rapidly
condenses on the surfaces of the circuit breaker contacts resulting in quick
recovery of di-electric strength. The reader May note that the salient feature
of vacuum as an arc quenching media. As soon as the arc is produced in vacuum,
it is quickly extinguished due to the fast rate of recovery of di-electric
strength in vacuum.
MCB ( MINIATURE CIRCUIT BREAKERS)
Ø “L” – SERIES : GREEN
KNOB MCB – FOR LIGHTING
Ø “G” – SERIES: BLUE KNOB
MCB - FOR MOTOR
Ø DC – SERIES : BLACK KNOB - FOR DC CIRCUIT
Ø ISOLATOR : RED KNOB -
Features:
1. At the short ckt, it does
not allow to flow fault current fully
2. Contacts get opened within
1 m/sec.
3. Operating time is less
that 5 m/sec.
ELCB
TYPES OF
BREAKERS
LOW VOLTAGE:
1. Miniature circuit breaker
2. Molded case circuit
breaker
3. Residual case circuit breaker
4. Power breakers
HIGH
VOLTAGE:
1. Air blast circuit breaker
2. SF6 – (sulfur) breaker
3. Vacuum circuit breaker
4. Oil circuit breaker
5. Minimum oil circuit
breakers.
NPCC
MAIN INCOMER BREAKER – USED RELAY NPCC – LV
1. Inverse type Under voltage
relay : Type: VAGM – 2 Nos, Range: 44 to 88 Volts
2. Over Current
Relay(Inverse): Type CDG – 2 Nos., Range: 2.5 to 10 Amps
3. Earth Fault
Relay(Inverse): Type CDG – 2 Nos., 0.5 to 2 Amps.
4. Instantaneous Earth Fault
Relay: Type CAG, Range: 0.5 to 2 Amps
5. Tripping Relay : Type:
VAJ, Range 110 to 125 Volts,
6. Trip Circuit Supervision
Relay: Type – VAX MK11
SIEMENS BREAKERS
BASIC PROTECTIVE FUNCTIONS
v The basic protective
functions of the over current release are ensured without additional auxiliary
voltage. The required power is supplied by internal transformer of the circuit
breaker.
v To evaluate arc current,
the electronic system of the over current release calculates the RMS value.
OVERLOAD PROTECTION
v The current setting Ir defines the maximum continuous
current. The circuit breaker can carry without tripping. The time lag class tr
determines the maximum duration of an over load without tripping
ETU – 45B – IR
(0.4/0.45/0.5/0.55/0.6/0.65/0.7/0.8/1.0) X In.
BASIC PROTECTIVE FUNCTIONS
OF ACB
v Over Load Protection – L Tripping
v Short Time Delay – Short
circuit protection – S Tripping
v Instantaneous short
circuit protection – I Tripping
v Neutral conductor
protection – N Tripping
v Earth fault tripping 1.
Alarm setting.
SHORT TIME DELAY:SHORT CIRCUIT TRIPPING – S TRIPPING
v Over current rrelease ETU 25-B-76B tripping due to the short
circuit current Isd can be delayed
by the time tsd.
This provides selectivity for the short circuit protection in switch gear
with several grading levels.
ETU – 25B, 45B – Isd
(1.25/1.5/2/2.5/3/4/6/8/10/12) X In.
SETTING FOR tsd
ETU – 45B –
tsd=0.02(M)/0.1/0.2/0.3/0.4 Si off
v The time delay 0.02s isnot
a grading time. In this protection, the motor protection function is activated.
v For setting tsd >0.4s the maximum possible
setting Isd is reduced automatically
according to frame size.
Frame size : 1.5 KA, 20 KA, 30KA.
with the setting “off”. For the over current release ETU 45B – 76B is provided to de-activate the short time delay short
circuit protection.
If zone selective inter locking ZSI
-> is used however, the setting for the time delay tsd is deactivated. If the circuit breaker does not receive any
blocking, signal from a down streak circuit breaker, it will trip after 50 ms regardless of the setting for tsd.
MOTOR PROTECTION FUNCTIONS
v In the circuit breaker
position tsd = (M) (0.02), a special
protection function for electromotive drive is activated. It prevents the short
time delay short circuit tripping. From being activated during the peak inrush
current of electric motors. At the same time phase failure protection is activated
and time constant for the internally calculated reproductive of the temperature
rise and cooling process is switched over from switch gear protection to motor
protection.
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