Detection of Open-circuit Fault in 11kV Ring Circuits by Unbalanced Current Measurement

A novel method is introduced for the detection of single- or two-phase open-circuit cable joint defect in CLP Power´s 11 kV ring circuits. This method utilizes the existing secondary neutral wiring of 11 kV protection relays to detect any unbalanced circuit currents resulting from open-circuit faults. Alarms are connected to the system control centre alerting control engineers for any detection of unbalance currents. It could facilitate prompt investigation thus enhancing the serviceability of the network. Sophisticated 3-phase simulation study by PSCAD/EMTDC was conducted to identify the optimal installation location and settings of the detection device. Various balanced and unbalanced loading scenarios as well as the impacts of harmonics were taken into consideration to ensure effective detection of the open-circuit fault. This paper provides useful references to power system engineers in improving supply reliability in power distribution systems