Modelling Transposed-150kV-HVTLsWest Kalimantan Subsystemand 275kV SEB-PLN InterconnectionVoltage Unbalance Mitigation

The 275kV regional interconnection HVTL Mambong (Sarawak) to Bengkayang (West Kalimantan) imposes challenges to the GSO (Grid System Operators) to maintain the voltage levels and voltage unbalance within limits. We suggest how to design the strategies for stable operations under unbalance system situations for the power system interconnection. According to the existing concept, the transposition of transmission line phases is intended to reduce the current and voltage unbalance in the normal electrical system operating mode and to limit the obstructive influence of transmission lines on the transmission channel of low frequency. The length of the transposition process for lines with horizontal phase allocation should not exceed 24 km, and should not exceed 48 km at triangle allocation. The discrepancy in its parameter at one transposition interval is not completely balanced over the entire process, since the line is distributed at different conditions at one of the intervals. For a period in total the resulting parameters of line phases are different. Thus, even at the exact symmetry current and voltage systems at one end of the full transposition cycle, these systems at the other end become imbalances. This paper provides an analysis by applying the EMT Evaluation (Electromagnetic Transients Analysis) of the transposed 150 kV (Tayan-Sandai) transmission line of 162 km length. In this way, the findings obtained attest to the continuity of the inquiries and can also be used to address the problems of the specification of acceptable unbalance rates in longer lines.