RESIDUAL CURRENT DEVICES IN LV FOR THE LHC J. Gomez ST/EL-PM

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n Two ways of portecting againts earth faults Over current devices.Over current devices. – Compliance with IEC Residual current devices.Residual current devices. –Types according IEC A, AC, BA, AC, B

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n Types according IEC Over current devices. – Type A: For sinusoidal currents or pulsed DC currents. –Type AC: Detects only sinusoidal currents. –Type B: For DC currents.

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n 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.

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n Avoiding unwanted tripping. Normally due to capacitive transient leakage'sNormally due to capacitive transient leakage's Unknown behavior of the electronic devices.Unknown behavior of the electronic devices. This kind of tripping represent a lack of quality network and should be reduced to a maximum.This kind of tripping represent a lack of quality network and should be reduced to a maximum.

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n Avoiding unwanted tripping. These currents may be generated because of the following reasons: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.

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n Avoiding unwanted tripping. These currents may be generated because of the following reasons: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). RCB’s against this phenomena are mark with a particular symbol.RCB’s against this phenomena are mark with a particular symbol.

RESIDUAL CURRENT DEVICES IN LV FOR THE LHC n 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.No residual current devices for circuits feeding critical equipment. Accepted by TIS. Installation of unwanted tripping protected A type residual current devices.Installation of unwanted tripping protected A type residual current devices.