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Highlights: [•] Study on directional over-current and earth-fault for biomass micro grid. [•] The delta side of the transformer cannot be cleared by earth-fault relay for single phase to earth fault. [•] Under voltage relay is adopted at the delta side of the transformer. [•] Simulation shows good coordination at all possible locations. [Copyright &y& Elsevier]

Abstract: This paper presents a study on flashover patterns due to double tripping using EMTP software. The simulation was performed on a 132kV line double circuit for economic installation of transmission line arresters (TLAs). The simulation results were validated with the field data of 132kV transmission line in Malaysia. A vertically configured double circuit transmission line was modelled and the effects of tower footing resistance, lighting current values, power frequency voltage and the coupling effect of the phase conductors study were taken into account. A good agreement between the simulation and field data was obtained. A specific back flashover phase of the double circuit line can be determined by considering the effects that have been mentioned. Through determination of the tripping pattern, a suitable installation of line arresters and mitigation of line tripping due to back flashover can be achieved. [Copyright &y& Elsevier]

Abstract: Differential protection scheme is based on comparison of measured variables such as current and voltage at the two ends of a line via a communication channel such as pilot wire. This scheme is preferred and extensively used in distribution feeder protection system in Malaysia due to its fast operation. However pilot-wire differential scheme has its own drawbacks especially on the maintenance of the pilot-wire. Once the plot-wire is out of service, the feeder protection is jeopardised. One of the options to overcome such maintenance issue is to adopt directional relay as the feeder protection. This paper investigates a suitable relay connection and the maximum torque angle for the directional relay for 33kV underground network. In this study, a section of 33kV underground network in Kuala Lumpur (KL) city has been analysed. All faults types have been simulated at all possible location in the network. The obtained voltage and current were then used to determine the operation of directional overcurrent and earth-fault relay. The simulation results indicate that 30° relay connection with 0° maximum torque angle (30°/0°) is the most suitable setting to be applied for 33kV underground network in KL, as against the best general and most versatile setting, 45°/90°. [Copyright &y& Elsevier]