RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• J. Gomez ST/EL-PM

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Two ways of portecting againts earth faults
• Over current devices.
• Compliance with IEC 364-4
• Residual current devices.
• Types according IEC 60755
• A, AC, B

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Types according IEC 60755 Over current devices.
• Type A For sinusoidal currents or pulsed DC
  currents.
• Type AC Detects only sinusoidal currents.
• Type B For DC currents.

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• An eventual earth fault, in an electronic device,
  with a high DC component might deceive a
  standard residual circuit breaker preventing it
  from opening and consequently creating a
  dangerous situation.

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Avoiding unwanted tripping.
• Normally due to capacitive transient leakage's
• Unknown behavior of the electronic devices.
• This kind of tripping represent a lack of quality
  network and should be reduced to a maximum.

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Avoiding unwanted tripping.
• These currents may be generated because of the
  following reasons
• Long power lines. (62mA per Km)
• Equipment containing capacitive earthed devices.
  Interference filters (ECM) placed in
  microcomputers generate permanent leakages
  currents at 50Hz of the order of 0.5 to 1.5 mA
  per device.

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Avoiding unwanted tripping.
• These currents may be generated because of the
  following reasons
• Transient leakage currents.
• High frequency leakage currents.
• Lightning currents. Peak value 250A (8/20
  microseconds).
• RCBs against this phenomena are mark with a
  particular symbol.

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RESIDUAL CURRENT DEVICES IN LV FOR THE LHC

• Conclusion
• In many cases electronic equipment are of the
  highest importance for the future safety of the
  new accelerator. A quality non-stop supply is
  absolutely necessary.
• Two possibilities
• No residual current devices for circuits feeding
  critical equipment. Accepted by TIS.
• Installation of unwanted tripping protected A
  type residual current devices.