AC / DC Earth Leakage
Residual current detection
An AC / DC earth leakage unit detects current imbalance in trainborne and wayside cabling. Early detection of cable and equipment degradation can prevent further damage. In addition it can stop potential hazards associated with these types of faults.
What do AC / DC Earth Leakage units do?
The AC / DC Earth Leakage Unit is a residual current detection unit which is powered from the vehicle’s battery or AC supply and measures the sum of the current in the primary ‘supply and return’ conductors passing through its aperture.
During normal operation when there is no earth fault or imbalance present in the system, the current in the conductors cancel each other out so no fault is triggered.
The measured residual current signal is filtered and rectified before it is fed into a comparator circuit. If the current is greater than a set detection level, then a fault is signalled via volt-free relay contacts. The fault output may reset after a delay if residual current falls below the desired detection level or remain latched in the fault state until the unit is powered off and on again.
Rowe Hankins’s has developed a new dual trip AC Earth Leakage Unit that is digitally programmable and forms the next evolution of current imbalance detection products and systems.