Protection & Control Relay (IED)
Protection relay evolution
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Electromechanical relay :
- Induction disc type
- Electromagnetic forcecauses mechanicaloperation of relay
- Fixed operatingcharacteristic
Static relay :
- Doesn’t have moving parts- Trip output is of attracted
armature type- Operating qty is generated
by discrete analog(generally) electroniccomponents
- Selectable operatingcharacteristic
Numeric relay, IED :
- Analog input is sampled andconverted to digital format.
- The digital quantity is managedfurther by microprocessor withmathematical algorithm to generatethe operating quantities andimplement the protection functions.
- Operating characteristic isadjustable.
- Having sophisticatedcommunication features.
Protection function
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Detectfaults
Isolate faults selectively andquickly from the network
To limit consequences, i.e.damaged equipment or loss ofproduction
Protection requirementLV MV 70kV…150kV 275kV…500kV
Fuse,MCB
Overcurrentrelays
- Main prot- Backup prot
- Main 1- Main 2
Shorter operating time
Protection applicationSystem topologyand characteristic
Protection zones, Fault detection,Suitable protection scheme andalgorithm
Protection relayselection & settings
Higher CT requirement
Fault clearing time
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Fault clearing time according to Aturan Jaringan PLN (Grid Code) :
1. For main protection
- 500 kV system ≤ 90 ms
- 275kV system ≤ 100 ms
- 150kV system ≤ 120 ms
- 70 kV system ≤ 150 ms
2. For backup protection ± 500 ms
3. Fault clearing time consists of :
- Relay operating time
- Circuit breaker break time
- Teleprotection transfer time
- CT performance
Example 1 : Unit protection zones
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OHL
Bus1
Bus2
Line protection :- Distance- Line diff.
Transformer prot. :- Diff.- REF
Busbar prot. :- Busbar Diff.
Example 2 : Unit protection zones
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OHL
Bus1 Bus2
Line protection :- Distance- Line diff.
Transformer prot. :- Diff.- REF
Busbar prot. :- Busbar Diff.
Example 3 : Unit protection zones
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OHL
Bus1 Bus2
Line protection :- Distance, or- Line diff.
Transformer prot. :- Diff.- REF
Busbar prot. :- Busbar Diff.
Tee zone prot :- Circulating
current
Fault detection :
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500 ohm
Ground fault currenttoo small…practicallynot feasible
Make use of open deltaVT to detect ground faultfor :- Neutral displacementprotection relay
Challenging areas :
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§ CT accuracy class
§ CT saturation
§ Transformer inrush
§ Zero-sequence block by deltawinding or ungrounded wye
§ Power swing
§ Communication scheme forline protection
§ Short zone/dead zone
§ High impedance differentialprotection
§ Asynchronous closing ofcapacitor or transformer
CT classes :
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§ Metering : 0.2S, 0.2, 0.5, 1
§ Protection : Class P, Class PX, TPX, TPY, TPZ
Power swing :
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Communication scheme for protection :
Short zone/dead zone :
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High impedance differential protection:
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Capacitor bank energization :
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§ High frequency inrush currentà protection failure§ Overvoltageà flashover
Transformer energization :
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§ V=L.di/dtà assymetrical inrush current for closing at zero crossing§ Voltage drop
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Contact PersonName : Ustika Anggono
Division : Power System
Position : Engineering Manager
Email : [email protected]
Mobile : 081514271512