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In the name of ALLAH the mostbeneficent the most merciful
1
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POWER GENERATION SOURCE
• HYDEL• THERAML• NEUCLEAR• SOLAR• WIND
• SEA WAVE
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POWER SYSTEM
Power system is consist of
• Generation•
Transmission• Distribution
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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
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TYPES OF SUBSTATIONS
• G.I.S GAS
INSULATION
SUBSTATION/SWITCHGEAR
• A.I.S AIR
INSULATION
SUBSTATION/SWITCHGEAR
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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
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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
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Bus Bar Schemes in our Power system
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
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Bus Bar Schemes in our Power system
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
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Bus Bar Schemes in our Power system
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
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Bus Bar Schemes in our Power system
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
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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
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FUNDAMENTALOF PROTECTION
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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
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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.
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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.
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• 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
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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
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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
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Over Current Relay Ph to Ground Fault
R Ø Y Ø B Ø
E/F
RelayCoil
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Over Current Relay Ph to Ph Fault
R Ø Y Ø B Ø
E/F
RelayCoil
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9/14/13 Technical ServicesGroup Rana Tahir
22
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
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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
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RESTRICTED EARTH FAULT RELAY
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Trip
RESTRICTED EARTH FAULT RELAY
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RESTRICTED EARTH FAULT RELAY
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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
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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.
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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
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HVCONNECTION ORCURRENT CIRCULATION RELAY
220/132 KV
Transformer
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LVCONNECTION ORCURRENT CIRCULATION RELAY
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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.
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THE END
Jazak Allah Khair
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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
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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