Tahanan pentanahan dengan menggunakan elektroda pentanah dipengaruhi oleh jenis tanah, struktur tanah, unsur kimia dalam tanah, ukuran dan cara penempatan elektroda pentanah. Tahanan pentanahan sedapatnya memiliki nilai sekecil mungkin dan memenuhi standar aman (PUIL 2000) agar dapat mengalirkan arus gangguan sebaik-baiknya ke tanah. Dalam penelitian ini dilakukan usaha untuk mereduksi tahanan pentanahan pada tahanan jenis tanah seragam berdasarkan metode parit melingkar yaitu memperdalam kedalaman penanaman elektroda batang tunggal 0.5 m, 0.75 m dan 1.15 m dan merubah komposisi kimia tanah menggunakan dengan memberi bahan pereduksi bentonit type Na di sekeliling elektroda pentanah dengan memvariasi tinggi parit bentonit dari 0.1 m sampai dengan 0.5 m. Pengukuran tahanan pentanahan dilakukan tanpa bentonit dan dengan bentonit. Dari hasil pengukuran menunjukkan dengan memperdalam elektroda pentanah menghasilkan penurunan nilai tahanan pentanahan, pada kedalaman elektroda pentanah 0.5 m dihasilkan tahanan pentanahan 96.47 ohm, kedalaman elektroda pentanah 0.75 m tahanan pentanahannya 65.17 ohm dan kedalaman elektroda pentanah 1.15 menghasilkan tahanan pentanahan 25.96 ohm. Sedangkan dari hasil perhitungan untuk tiap kedalaman elektrodanya didapatkan tahanan pentanahan 96.01 ohm, 68.77 ohm, dan 48.13 ohm. Setelah pemberian bentonit parit melingkar dengan variasi tinggi paritnya berdasarkan hasil pengukuran untuk tiap kedalaman elektroda pentanahan didapatkan penurunan nilai tahanan pentanahannya 43.94% sampai dengan 62.6 %, 44.15% sampai dengan 57.53% dan 25.35% sampai dengan 41.68%. Berdasarkan hasil perhitungannya untuk setiap kedalam elektroda didapatkan penurunan tahanan pentanahan sebesar 28.3% sampai dengan 77.39%, 47.05% sampai dengan 72.55%, dan 38.52% sampai dengan 64.78%. Hasil pengukuran maupun hasil perhitungan telah sesuai dengan IEEE standart 141-1993 yaitu nilai penurunan tahanan pentanahan berkisar antara 15% sampai dengan 90% bila diberi bahan kimia.

Grounding resistance uses ground rod electrode is influenced soil condition, soil structure, soil chemical composition, size and ground rod electrode placement. The grounding resistance should be made as small as possible and fulfill its standard ( PUIL 2000) in order to flows fault current as well to ground. In this research to reduce grounding resistance at homogeneous kind of grounding resistance according trench method that is deepended on single rod electrode having the length of 0.5, 0.75 m, and 1.15 m, so changed soil chemical composition was done by varying trench raise which having the value of 0.1 m up to 0.5 m. The measurement of grounding resistance were done with and without bentonite. From measurement results, we know by deepening of single rod electrode, resulted the reduction of grounding resistance . For deepening of 0.5 m, resulted grounding resistance was 96.47 ohm, deepening of 0.75 m resulted grounding resistance was 65.17 ohm, and deepening of 1.15 m resulted grounding resistance was 25.96 ohm. From calculation results for each deepening of electrode the resulted of resistance grounding were 96.01 ohm, 68.77 ohm, and 48.13 ohm. After was gave bentonite in trench caused reduction of grounding resistance. Based on measurement results for each ground rod electrode, reduction of resistance grounding value were 43.94% up to 62.6%, 44.15% up to 57.53%, and 25.35% up to 41.68%. Based on calculation results for each ground rod electrode, reduction of resistance grounding value were 28.3% up to 77.39%, 47.05% up to 72.55%, and 38.52% up to 64.78%. The resulted of measurement and calculation agree with IEEE Standard 141-1993. This standard shows that the decrement of grounding resistance of one ground rod with chemical treatment will be in the range of 15% up to 90%.

Kata Kunci : Pentanahan,Tahanan pentanahan,Elektroda batang tunggal,Parit melingkar,Bentonit, grounding resistance, single rod electrode, trench method, bentonite