Transformer

POWER TRANSFORMER

SUMIT DASH1203248ELECTRICAL ENGINEERING

•What is a transformer?

•Why to use a transformer?

•Where to use transformer?

CONSTRUCTION

TESTS

COMISSIONING

PROTECTION

POWER TRANSFOR

MER

CLASSIFICATION

PHASE CORE WINDING INSULATION VOLTAGELEVEL

PROTECTION AT THE SITE

3 PHASE1 PHASE

oCore typeoShell type

AutoTwoThree/Tertiary

Oil cooledAir cooled

Step upStep down

CTPT

G.T.P.T.D.T.

DIFFERENT PARTS OF A TRANSFORMER

1.Electrical Parts2.Mechanical Parts3.Insulation PartElectrical parts :

1. WINDING

2. BUSHING

3. OLTC

4. Fan and pump

MECHANICHAL PARTS

Insulation Parts1. Oil2. Insulation Between windings

DIFFERENT PARTS OF A TRANSFORMER

1.Core

2.Tank3. Conservator4. Radiator

5. Breather

6. Buchholz Relay

CONSTRUCTION

MATERIAL

WIDTH

CORE

HEIGHT

STACKING

FACTOR

CORE STEP

CORE LOSS

EMF/TURN

Current Density

Coil diameter

Resi

st

ance

at

75’

cLoss

at

75’

C

WINDING

TESTS ON A TRANSFORMER

Tests Done by Manufacturer

Routinetest

Type test

SpecialTest

Tests done at site

Pre-commissioningtest

Condition monitoring test

Emergency test

4/5/2016

ROUTINE TESTInsulation resistance/P.I. Test

Winding resistance

Voltage Ratio

Vector group

Magnetic balance

TYPE TEST

Dielectric strength test

Temperature rise test

Lightening impulse test

SPECIAL TESTZero sequence impedance test

Frequency Response analysis on a transformer

Testing of noise level

Harmonics on no load current

TESTS BY MANUFACTURE

R

TEST AT SITEPRECOMMISSIONI

NG TEST

Polarity Test

No load test

Vector Group Test

Transformer Oil Test

CONDITION MONITORING TEST

o Gas and Moisture content in Oil

o OLTC Health

o Conservator Health

o Hot spot temprature

EMERGENCY TEST

•PRV

•Gas content in Oil

PROTECTION OF TRANSFORMER

EXTERNAL FAULTS

INTERNAL FAULTS

INCIPIENT FAULTS

SHORT CIRCUITS

HIGH VOLTAGE, HIGH FREQUNCY DISTURBANCE

EARTH FAULTS OVER LOAD

CONDITION OVER

EXCITATION

PHASE TO EARTH

PHASE TO PHASE

INTER TURN PROBLEM IN

TAP CHANGER

SHORT CIRCUIT IN LAMINATIONS

CORE BOLT INSULATION FAILURE

LOCAL HEATING DUE TO CLOGGING OF OIL

COOLENT FAILURE EXCESS INGRESS OF

AIR IN OIL SYSTEM

Chart Title

WHY PROTECTION OF TRANSFORMER?1. To minimize the damage and interruption of

service 2. Loss of revenue due to outage3. Down time for replacement is very high.4. Inconvenience to the consumers,

CLASSIFICATION OF PROTECTION FUNCTIONElectrical failure Abnormal condition

Protective device

1. Unit protection

Differential protection

REF protection

2. Non unit protection

•Overload protection

•Overvoltage protection

•Over fluxing protection

•Switching/Surge protection

Buchholz Relay

PRV

Oil level indicator

Winding temperature indicator

DIFFERENTIAL PROTECTION

RESTRICTED EARTH FAULT PROTECTION

PROTECTION FOR ABNORMAL CONDITION

OVER FLUXING:

Principle : Comparison of voltage in the system to the frequency available, decides the nature of flux in the core and accordingly the over flux setting is decided and causes the tripping for the value above the setting adopted. Over Voltage:

Voltage Transformers are used to measure the voltage. When ever the voltage exceeds the setting value , then it is tripped. Over voltages are mainly due to switching surges and lightening strokes

Switching Surge and Lightening Protection:

Surge arresters are used for this. There is a surge counter in this to count the no. of surges it has successfully arrested.

PROTECTIVE DEVICE Pressure Releasing Valve:

For the case of Serious faults inside the transformer, oil pressure rises beyond the certain limit. Hence a pressure relief device provided on top of the transformer opens to allow discharge of oil and extends the tripping command. This device automatically closes as soon as the internal pressure falls below the critical level.

Buchholz RelayWorking Principle:- This relay being filled with oil, displaces the oil for the case of gas collection due to internal fault and issues alarm contact and as per the severity of gas collection, tripping results.

Oil Level Gauges / Indicators

This device contains a float attached to the indicator knob in the dial. It is floated in the conservator oil tank and indicates the level of oil. For the case of leakage of oil or problem in the air cell system, this float indicates the level with close of an alarm contact.

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