ASSESSMENT OF PROTECTION SCHEMES: A KEY FACTOR FOR RELIABILITY

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ASSESSMENT OF PROTECTION SCHEMES A KEY FACTOR
FOR RELIABILITY

• Alain SCHENK
• David ORZAN
• Fritz GANTENBEIN
• Markus VON ARX
• BKW FMB Energy Ltd.
• Switzerland

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Assessement of protection Why ?

• Liberalization
• Cost reduction
• High quality of supply (reliability)
• risk management, condition based maintenance
• Less security margin ? More faults are expected
  than before

• New possibilities improve the reliability of
  protection
• Numerical relays (new schemes for specific
  situations)
• Calculation programs
• Testing devices

3
Assessement of protection How ?

• Tools
• Event of fault recorders
• Periodic relay testing
• Calculation programs
• Dynamic relay testing

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Simulation for a mutliterminal line

• Problems
• Relatively short line (15 km)? selectivity
• High short circuit currents and quite well
  interconnected network
• No signalling equipment
• Inhomogeneous lines
• Industrial plants? own generation capabilities
  or supply by other networks

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Simulation for a mutliterminal line
With embedded generator(Industry customer)
Without embedded generator(Industry customer)
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Dynamic relay testing

• Incorrect relay operation
• Did the relay maloperate or were the settings
  incorrect ?? check of relay behaviour? check of
  relay settings

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Dynamic relay testing
Voltage (faulted phase)
Voltage (healthy phase)
Current
? Unstable operation of the relay could be
confirmed
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Dynamic relay testing
Problem

• Does the relay trip when a short circuit occurs
  between the two systems ?

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Dynamic relay testing

• Tripping unreliable without earth contact ?
  teleprotection

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Conclusion

• Situation
• Protection assessment is necessary because of the
  reduced security margin due to cost pressure
• Protection assessment can be significantly
  improved through simulations and dynamic testing

• Advantages of the proposed approach
• Reduced investigation time ? low cost
• Consideration of all scenario and aspects ? high
  quality
• Study of complicated situations ? deep
  understanding