Analisis Koordinasi Isolasi Peralatan Tegangan Tinggi terhadap Sambaran Petir pada Gardu Induk 150 kV Mojoagung

Sambaran petir pada jaringan Saluran Udara Tegangan Tinggi (SUTT) 150 kV dapat menimbulkan tegangan lebih transien yang berpotensi merusak isolasi peralatan di gardu induk. Oleh karena itu, diperlukan sistem perlindungan dan koordinasi isolasi yang baik agar peralatan tetap aman dan andal. Penelitian ini bertujuan untuk menganalisis mekanisme perlindungan isolasi peralatan terhadap surja petir serta mengevaluasi kesesuaian Tingkat Isolasi Dasar (TID) atau Basic Insulation Level (BIL) peralatan pada Bay Trafo di Gardu Induk 150 kV Mojoagung. Adapun metode yang digunakan meliputi perhitungan teoritis koordinasi isolasi berdasarkan standar SPLN 7A:1978 dan IEC 71:1976, serta simulasi tegangan surja petir menggunakan software Alternative Transient Program (ATP). Selain itu, dilakukan evaluasi terhadap kinerja Lightning Arrester dan sistem pentanahan gardu induk. Hasil penelitian menunjukkan bahwa sistem perlindungan yang diterapkan, seperti pemasangan kawat tanah, nilai tahanan pentanahan yang rendah, serta penggunaan Lightning Arrester, telah memenuhi persyaratan teknis. Dampak sambaran petir pada jaringan SUTT 150 kV terhadap peralatan Bay Trafo 1, 2, dan 3 menimbulkan tegangan lebih transien pada PMT, CT, dan transformator. Berdasarkan simulasi, tegangan tertinggi yang sampai ke PMT sebesar 499 kV, dan CT sebesar 504 kV. Dengan spesifikasi tegangan pelepasan Lightning Arrester sebesar 380 kV dan arus 10 kA sudah mampu membatasi tegangan surja petir yang sampai ke transformator hingga sekitar 512 kV. Hasil perhitungan nilai Protective Margin sebesar 71,05% pada transformator dan 97,4% pada PMT dan CT menunjukkan bahwa koordinasi isolasi telah memenuhi standar IEEE C62.22. Dengan demikian, peralatan pada Bay Trafo Gardu Induk 150 kV Mojoagung dinyatakan terlindungi dari dampak tegangan lebih transien akibat surja petir.

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Lightning strikes on the 150 kV High Voltage Overhead Transmission Line (SUTT) network can cause transient overvoltage that has the potential to damage equipment insulation in substations. Therefore, a good protection and insulation coordination system is needed to keep the equipment safe and reliable. This study aims to analyze the insulation protection mechanism of equipment against lightning surges and evaluate the suitability of the Basic Insulation Level (BIL) of equipment at the Transformer Bay in the 150 kV Mojoagung Substation. The methods used include theoretical calculations of insulation coordination based on the SPLN 7A:1978 and IEC 71:1976 standards, as well as lightning surge voltage simulations using the Alternative Transient Program (ATP) software. In addition, the performance of the Lightning Arrester and the substation grounding system was evaluated. The results of the study show that the protection systems implemented, such as the installation of ground wires, low grounding resistance values, and the use of Lightning Arresters, have met the technical requirements. The impact of lightning strikes on the 150 kV SUTT network on Bay Transformer 1, 2, and 3 equipment caused transient overvoltage on the PMT, CT, and transformers. Based on simulations, the highest voltage reaching the PMT was 499 kV, and the CT was 504 kV. With the Lightning Arrester's discharge voltage specification of 380 kV and a current of 10 kA, it was able to limit the lightning surge voltage reaching the transformer to around 512 kV. The calculated Protective Margin values of 71.05% for the transformer and 97.4% for the PMT and CT indicate that the insulation coordination meets the IEEE C62.22 standard. Thus, the equipment in the 150 kV Mojoagung Substation Transformer Bay is protected from the effects of transient overvoltage due to lightning surges.