Rana Tahir

7/29/2019 Rana Tahir

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In the name of ALLAH the mostbeneficent the most merciful

1



POWER GENERATION SOURCE

• HYDEL• THERAML• NEUCLEAR• SOLAR• WIND

• SEA WAVE



POWER SYSTEM

Power system is consist of

• Generation•

Transmission• Distribution



P. Trans 11/132KV

Generator

132 KV Busbar

132 KV T.Line

132 KV Busbar

P. Trans 132/11KV

11 KV Busbar

Dis. Trans

11/.44 KV

P. Trans 11/220KV

P. Trans 11/500KV

220 KV T.Line

500 KV T.Line

POWER SYSTEM



TYPES OF SUBSTATIONS

• G.I.S GAS

INSULATION

SUBSTATION/SWITCHGEAR

• A.I.S AIR

INSULATION

SUBSTATION/SWITCHGEAR



Air Insulated Substations

Various factors affect the reliability of a substation, one of which is the arrangement of the switching devices.

Arrangement of the switching devices will impact

maintenance, protection, initial substation development,

and cost. There are six types of substation bus switching

arrangements commonly used in air insulated substations:1. Single bus

2. Double bus, double breaker

3. Main and transfer (inspection) bus

4. Double bus, single breaker 5. Ring bus

6. One and a half



Bus Bar Schemes in our Power system

Single Bus Configuration

Reliability : Least reliable — single failure can cause complete outage

Cost: Least cost — fewer components

Available area: Least area — fewer components




Double Bus, Double Breaker Configuration

Reliability : Highly reliable — duplicated components; single

failure normally isolates single component

Cost: High cost — duplicated components

Available area: Greater area — twice as many components




Main and transfer bus configuration

Reliability : Least reliable — same as Single bus, but flexibility in

operating and maintenance with transfer bus

Cost: Moderate cost — fewer components

Available area: Low area requirement — fewer components




Double Bus, Single Breaker Configuration

Reliability : Moderately reliable — depends on arrangement of

components and bus

Cost: Moderate cost — more components

Available area: Moderate area — more components




Ring bus configuration

Reliability : High reliability — single failure isolates single

component

Cost: Moderate cost — more components

Available area: Moderate area — increases with number of circuits



9/14/13 Technical Services 12

CB

CB

CB

CB

CB

CB

Isolator

Isolator

Isolator

Isolator

Isolator

Isolator

Isolator

Isolator

Isolator

IsolatorIsolator

Isolator

LineIsolator

LineIsolator

EarthIsolator

EarthIsolator

CT

CT

CT

CT

CT

CT

BB 1 PT

L

/

Arrester

L

/

Arrester

P. Transformer

L

/

Arrester

L

/

Arrester

P. Transformer

Bus Bar # 1(A)

Bus Bar # 2(B)

O n e a n d H a l f

B r e a

k e r

S c h e m

e

BB 2 PT



FUNDAMENTALOF PROTECTION



FUNDAMENTALS OF PROTECTION

REQUIRMENT OF PROTECTION

Basically the hazards that the plant or grid station must be protected

against are external hazards, equipment failure, and operator error.

One example of an external hazard is lightning prevented, but we must

protect our equipment from their effects.

Equipment failure results from faults in machinery. For example, electrical

short-circuit in the generator or Power Transformer.

Failure to control the cooling water supply to the hydrogen coolers is one

example of operator error. This increases winding temperature and can damage

the generator insulation. Failure to start equipment in the proper sequence is

another example of operator error. Fitting interlocks (permissive circuits) canprevent this.

Continue

!!



FUNDAMENTALS OF PROTECTION

• Automatic controls assist the operator and reduce the probability of error.

Operating procedures must be strictly followed.

• Protective devices prevent damage to the plant and protect personnel from

injury.

MECHANICAL CONDITIONS

• Equipment failures due to mechanical conditions include conditions such as

dangerous physical occurrences, machine over speed, machine vibration, and

material failure.

DANGEROUS PHYSICAL OCCURRENCES

• An obvious example of a hazardous physical occurrence is a turbine crane

running off its track. Installing a limit switch, to prevents this. When the limit

position is reached, the limit switch opens the circuit contacts, thereby

preventing further current flow to the motor that drives the crane toward its

limit position. Limit switches are used to indicate open and closed limits on

motorized valves.



PROTECTIVE TERMS• Reliability

The term’s reliability covers the correct design, installation and maintenance all CTs,

PTs, relays, AC and DC wiring.

In the event of a fault in zone, the protection relays should initiate tripping of the

circuit breakers to isolate only that zone from all live Supplies.

There is no such thing as partial reliability with protection schemes. They are 100%reliable or not reliable. Only 100% reliability is acceptable.

• Selectivity

The protection for a zone is said to selectivity when it only operates for a fault within

that zone.

• Sensitivity

A protection scheme with good sensitivity will operate correctly for very small fault

currents.

Continue!!



• Stability

A protection scheme is stable when it restrains from operating forlarge external faults (outside the zone).

In many cases, the protection relays must be stable for through-faultcurrents of twenty times the rated primary current of the CTs.

• Characteristic Quantity

This is the quantity, which determines how a relay operates. An overcurrent relay’s characteristic quantity is current, while an under-voltagerelay’s characteristic quantity is voltage.

• Rated Value

This is the value of the characteristic quantity on which the relayperformance is based.

It is marked on the relay’s rating plate. For an over current relay, therated value is the secondary current of the CT (1 A or 5A).

PROTECTIVE TERMS

Continue

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• Setting Value (Plug Setting)

The percentage of rated value at which the relay has been set.

• Pick-Up Value

For an over current relay, this is the minimum current which is just sufficientto operate the relay.

• Operating Time

The time taken for a relay to operate after a fault occurs.

• Reset (Drop-Off) Value

For an over current relay, which has operated, this is the maximum current atwhich the relay resets. For a good relay, the reset value is only slightly lessthan the pick-up values.

• Main Protection

This is the relay(s), which normally operates for a fault within its zone.

• Backup Protection

This operates if the main protection fails to clear the fault. It is usually slower(time discrimination) and trips out more of the system than main protection.

PROTECTIVE TERMS



Transformer Protection• HV Over current relay

• LV Over current relay

• Ground fault relay

• Thermal Over Load Relay

• Differential relay

• Current circulating relay

• Restricted earth fault relay

• Over excitation relay

• Buchholz relay• Oil temperature relay

• Winding temperature relay

• Gas release relay



Over Current Relay Ph to Ground Fault

R Ø Y Ø B Ø

E/F

RelayCoil



Over Current Relay Ph to Ph Fault

R Ø Y Ø B Ø

E/F

RelayCoil



9/14/13 Technical ServicesGroup Rana Tahir

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1 2 3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18 19 20

R E B

CDG AC Series Trip Earth Fault

Tripping Coils



9/14/13 Technical ServicesGroup Rana Tahir

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1 2 3 4 5 6 7 8 9 10

11 12 13 14 15 16 17 18 19 20

R E B

CDG AC Series Trip R & Earth Fault

Tripping Coils



RESTRICTED EARTH FAULT RELAY



Trip







DIFFERENTAL RELAY

Differential protection is a very reliable method of protecting generators, transformers, buses, andtransmission lines from the effects of internal faults.

APPLICATION

– Generator

– Transformer

– Circulating or connection point

– Generator Transformer

– Buss Bar

– Line



CIRCULATING CURRENT SCHEME

•There are two main types of unit protection scheme - circulating current and balanced voltage. Balanced voltage schemes are not discussed, as they are quite specialized and are mainly used on long feeder cables. This type of protection is quite rare in our system.

•Circulating current schemes are very common, however. They are used to protect generators, transformers, bus-bars and the short cables connecting them. The advantage of any circulating current scheme over IDMT relays is that it is very fast to operate - almost

instantaneous. This means that the fault in the main equipment is not allowed to extend and damage is minimized, making repairs easier, quicker and cheaper.



DIFFERENTIAL RELAY

Circulating Current Principle

9/14/13 29 Technical Services

Relay Stable

Fig. (A) shows whathappens when there is

normal load current flowing,or an external fault. EachCT produces the samesecondary current. Thesystem is thereforebalanced and no current

can flow through the relay. This type of protectionscheme is therefore verystable and the relay can beset to be very sensitive.

Fig. (B) shows whathappens when a short-circuit occurs inside the

zone. The both CTproduces a large secondarycurrent in same directiondue to fault. Therefore all of IS flows through the relay -as spill current. So the

relay operates and trips thecircuit breaker s .

TRIP



HVCONNECTION ORCURRENT CIRCULATION RELAY

220/132 KV

Transformer



LVCONNECTION ORCURRENT CIRCULATION RELAY



TRANSFORMER TEST

• Continuity test.

• Winding resistance test.

• Insulation test (megger test).

• TTR, Transformer turn ratio test.

• Short circuit test.

• Open circuit test.

• C&DF, Capacitance & Dissipation test.

• Dia electric strength of oil test.

• DGA, Dissolve Gas Analyzer test.



THE END

Jazak Allah Khair



C.T CURRENT TRANSFORMER

It is type of transformer whichtransform/ reduce the system current toa value low enough for safe and

convenient use in protection andmetering. It isolate the relay/meter fromthe primary system current. It is

connected in series with system.Usually its out put one ampere or five

ampere.Go Back



POTENTIAL TRANSFORMER

It is type of transformer which is use totransform/reduce the system high voltage toa low value for safe handling, to use in

protection, metering and energymeasurement.

These are two type.

1) Electromagnetic voltage T/F2)Capacitive Voltage Transformer. CVT and

CCVT. Go Back

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Rana Tahir