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It consists of overvoltage WITHSTAND test of POWER frequency LIGHTNING and impulse voltages.Testa are done for both internal and external insulation with SWITCH in both open and closed conditions.

It consists of overvoltage withstand test of power frequency lightning and impulse voltages.Testa are done for both internal and external insulation with switch in both open and closed conditions.

• USING a short CIRCUIT GENERATOR as the source.
• Using the power utility SYSTEM or NETWORK as the source.

Fuse is a low current interrupting device. It is a COPPER or an ALUMINIUM wire.Circuit breaker is a HIGH current interrupting device and it act as a switch under normal OPERATING conditions.

Fuse is a low current interrupting device. It is a copper or an aluminium wire.Circuit breaker is a high current interrupting device and it act as a switch under normal operating conditions.

Representation of various power SYSTEM COMPONENTS in a SINGLE line is defined as single line DIAGRAM.

Representation of various power system components in a single line is defined as single line diagram.

It is DEFINED as the RATIO of ACTUAL value to its base value. 96. Mention the inductance value of the peterson’s COIL.

L=1/3ωc2

It is defined as the ratio of actual value to its base value. 96. Mention the inductance value of the peterson’s coil.

L=1/3ωc2

AIR ,OIL,VACUUM CIRCUIT BREAKERS.

Air ,oil,vacuum circuit breakers.

9mA

9mA

Symmetrical faults and unsymmetrical faults and open conductor faults. 92. State the VARIOUS TYPES of unsymmetrical faults.

Line to GROUND ,line to line and DOUBLE line to ground faults

Symmetrical faults and unsymmetrical faults and open conductor faults. 92. State the various types of unsymmetrical faults.

Line to ground ,line to line and double line to ground faults

It has 3 vectors equal in MAGNITUDE and DISPLACED from each other by an angle 120 degrees and has the PHASE sequence in OPPOSITE to its original phasors.

It has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and has the phase sequence in opposite to its original phasors.

It has no zero sequence COMPONENT and the positive and negative sequence NETWORKS are connected in parallel.

It has no zero sequence component and the positive and negative sequence networks are connected in parallel.

They has 3 vectors having EQUAL MAGNITUDES and DISPLACED from each other by an ANGLE ZERO degees.

They has 3 vectors having equal magnitudes and displaced from each other by an angle zero degees.

has 3 vectors equal in magnitude and DISPLACED from each other by an angle 120 degrees and having the PHASE SEQUENCE as ORIGINAL vectors.

has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and having the phase sequence as original vectors.

POSITIVE SEQUENCE COMPONENTS, NEGATIVE sequence components and ZERO sequence components.

Positive sequence components, negative sequence components and zero sequence components.

It is a mathematical TOOL to RESOLVE unbalanced COMPONENTS into BALANCED components.

It is a mathematical tool to resolve unbalanced components into balanced components.

In SINGLE line to ground fault all the sequence networks are connected in series. All the sequence CURRENTS are EQUAL and the fault CURRENT magnitude is THREE times its sequence currents.

In single line to ground fault all the sequence networks are connected in series. All the sequence currents are equal and the fault current magnitude is three times its sequence currents.

A METHOD of reactance GROUNDING used to suppress the ARC due to arcing GROUNDS.

A method of reactance grounding used to suppress the arc due to arcing grounds.

The presence of inductive and capacitive currents in the isolated NEUTRAL SYSTEM leads to FORMATION of ARCS called as arcing grounds.

The presence of inductive and capacitive currents in the isolated neutral system leads to formation of arcs called as arcing grounds.

SOLID earthing, RESISTANCE earthing , REACTANCE earthing , VOLTAGE TRANSFORMER earthing and zig-zag transformer earthing.

Solid earthing, resistance earthing , reactance earthing , voltage transformer earthing and zig-zag transformer earthing.

In this method the breaker is first tested for its RATED breaking capacity at a reduced VOLTAGE and afterwards for rated voltage at a low current.This method does not give a PROPER ESTIMATE of the breaker PERFORMANCE.

In this method the breaker is first tested for its rated breaking capacity at a reduced voltage and afterwards for rated voltage at a low current.This method does not give a proper estimate of the breaker performance.

1. The CIRCUIT breaker can be tested at only a given rated voltage and network capacity.
2. The necessity to interrupt the normal services and to TEST only at light LOAD conditions.
3. EXTRA inconvenience and expenses in installation of controlling and measuring equipment in the FIELD.

The circuit breaker is tested under actual conditions LIKE those that occur in the network. Special occasions like breaking of charging currents of long LINES ,very SHORT line faults ,interruption of small INDUCTIVE currents etc. can be tested by direct testing only.

The circuit breaker is tested under actual conditions like those that occur in the network. Special occasions like breaking of charging currents of long lines ,very short line faults ,interruption of small inductive currents etc. can be tested by direct testing only.

Protection of GENERATOR and generator-transformer unit: protection of LARGE motors and BUS BARS

Protection of generator and generator-transformer unit: protection of large motors and bus bars

Relays which operates WHENEVER the CURRENT in a circuit drops below a predetermined VALUE.

Relays which operates whenever the current in a circuit drops below a predetermined value.

Relay which operates when the current ia a LINE EXCEEDS a PREDETERMINED VALUE.

Relay which operates when the current ia a line exceeds a predetermined value.

It MEANS preventing the RELAY from tripping due to its own CHARACTERISTICS or due to ADDITIONAL relays.

It means preventing the relay from tripping due to its own characteristics or due to additional relays.

It is the DISTANCE UPTO which the RELAY will COVER for PROTECTION.

It is the distance upto which the relay will cover for protection.

It is the INDICATOR USED for SHOWING the OPERATION of the RELAY.

It is the indicator used for showing the operation of the relay.

It is the MINIMUM CURRENT in the RELAY coil at which the relay starts to operate.

It is the minimum current in the relay coil at which the relay starts to operate.

The over voltage of the power system LEADS to insulation breakdown of the equipments. It causes the LINE insulation to flash over and MAY ALSO damage the nearby transformer, generators and the other EQUIPMENT connected to the line.

The over voltage of the power system leads to insulation breakdown of the equipments. It causes the line insulation to flash over and may also damage the nearby transformer, generators and the other equipment connected to the line.

1. The breaker can be tested for DESIRED transient recovery voltage and RRRV.
2. Both test CURRENT and test voltage can be INDEPENDENTLY varied. This gives FLEXIBILITY to the test
3. The method is simple With this method a breaker capacity (MVA) of five time of that of the capacity of the test plant can be tested.

• UNIT TEST
• SYNTHETIC test
• Substitution testing o COMPENSATION testing o Capacitance testing

• TYPE TEST
• ROUTINE test RELIABILITY test
• COMMISSIONING test

It has GOOD dielectric strength and excellent arc quenching PROPERTY. It is inert, non-toxic, noninflammable and heavy. At ATMOSPHERIC pressure, its dielectric strength is 2.5 times that of AIR. At THREE times atmospheric pressure, its dielectric strength is equal to that of the transformer oil.

It has good dielectric strength and excellent arc quenching property. It is inert, non-toxic, noninflammable and heavy. At atmospheric pressure, its dielectric strength is 2.5 times that of air. At three times atmospheric pressure, its dielectric strength is equal to that of the transformer oil.

SF6 has high affinity for ELECTRONS. When a free ELECTRON comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed. This is called as ELECTRO negativity of SF6 gas.

SF6 has high affinity for electrons. When a free electron comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed. This is called as electro negativity of SF6 gas.

The air has RELATIVELY inferior arc quenching properties

The air BLAST circuit breakers are very sensitive to variations in the rate of rise of restriking voltage

Maintenance is REQUIRED for the COMPRESSION plant which supplies the air blast

The air has relatively inferior arc quenching properties

The air blast circuit breakers are very sensitive to variations in the rate of rise of restriking voltage

Maintenance is required for the compression plant which supplies the air blast

• The risk of fire is diminished
• The arcing time is very small due to RAPID buildup of dielectric STRENGTH between contacts
• The arcing PRODUCTS are completely removed by the BLAST WHEREAS oil deteriorates with successive operations

• Arial-BLAST TYPE
• CROSS blast Radial-blast

• The DEGREE of carbonization is increased due to smaller quantity of oil
• There is difficulty of removing the GASES from the contact space in time
• The dielectric strength of the oil DETERIORATES RAPIDLY due to HIGH degree of carbonization.

• It requires lesser quantity of oil
• It requires SMALLER SPACE
• There is a reduced RISK of FIRE
• Maintenance PROBLEM are reduced

with ARC. So OIL is PREFERRED as an arc QUENCHING MEDIUM.

with arc. So oil is preferred as an arc quenching medium.

It ABSORBS the ARC energy to DECOMPOSE the oil into GASES, which have excellent cooling properties

It acts as an insulator and permits smaller clearance between line conductors and EARTHED components

It absorbs the arc energy to decompose the oil into gases, which have excellent cooling properties

It acts as an insulator and permits smaller clearance between line conductors and earthed components

Short contact life

Frequent MAINTENANCE POSSIBILITY of EXPLOSION

Larger arcing time for small currents PRONE to RESTRICTS

Short contact life

Frequent maintenance Possibility of explosion

Larger arcing time for small currents Prone to restricts

When the contacts of the breaker are separated, an arc is struck between them. This arc delays the current INTERRUPTION process and also generates ENORMOUS heat which MAY cause damage to the system or to the breaker itself. This is the main PROBLEM.

When the contacts of the breaker are separated, an arc is struck between them. This arc delays the current interruption process and also generates enormous heat which may cause damage to the system or to the breaker itself. This is the main problem.

• Air break CIRCUIT BREAKER OIL circuit breaker
• Minimum oil circuit breaker Air blast circuit breaker
• SF6 circuit breaker
• VACUUM circuit breaker

It is a PIECE of equipment USED to BREAK a CIRCUIT automatically under fault conditions. It BREAKS a circuit either manually or by remote control under normal conditions and under fault conditions.

It is a piece of equipment used to break a circuit automatically under fault conditions. It breaks a circuit either manually or by remote control under normal conditions and under fault conditions.

It is the rate of rise of restriking voltage, expressed in volts per microsecond. It is CLOSELY associated with NATURAL FREQUENCY of OSCILLATION.

It is the rate of rise of restriking voltage, expressed in volts per microsecond. It is closely associated with natural frequency of oscillation.

The POWER FREQUENCY RMS voltage appearing across the breaker contacts after the arc is extinguished and transient oscillations DIE out is called RECOVERY voltage.

The power frequency rms voltage appearing across the breaker contacts after the arc is extinguished and transient oscillations die out is called recovery voltage.

It is the TRANSIENT voltage appearing across the breaker contacts at the INSTANT of arc being EXTINGUISHED.

It is the transient voltage appearing across the breaker contacts at the instant of arc being extinguished.

HIGH resistance interruption:-the arc resistance is increased by ELONGATING, and splitting the arc so that the arc is fully extinguished

Current ZERO method:-The arc is INTERRUPTED at current zero position that occurs100 times a second in case of 50Hz power SYSTEM frequency in ac.

High resistance interruption:-the arc resistance is increased by elongating, and splitting the arc so that the arc is fully extinguished

Current zero method:-The arc is interrupted at current zero position that occurs100 times a second in case of 50Hz power system frequency in ac.

ARC is a phenomenon occurring when the two contacts of a circuit BREAKER separate under heavy load or FAULT or short circuit condition.

Arc is a phenomenon occurring when the two contacts of a circuit breaker separate under heavy load or fault or short circuit condition.