Kontinyuitas sangat dibutuhkan dalam menyalurkan tenaga listrik. Untuk mengurangi terjadinya durasi pemadaman pada pelanggan di PT. PLN (Persero) UP3 Area Kramat Jati yaitu dengan menerapkan kubikel Automatic Change Over (ACO). Tujuan pada penelitian ini untuk mengetahui simulasi pengujian pada kubikel Automatic Change Over (ACO), keandalan sebelum penerapan dan sesudah penerapan kubikel Automatic Change Over (ACO) dimana hal ini membutuhkan data gangguan sebelum penerapan kubikel ACO dan gangguan sesudah penerapan kubikel ACO, dan durasi lama pemadaman. Metode yang digunakan untuk menetapkan suatu indeks keandalan. Metode Sistem Average Interruption Duration Index (SAIDI), Sistem Average Interruption Frequency Index (SAIFI), Customer Average Interruption Duration Index (CAIDI). Hasil perhitungan pada gardu E325 N sebelum penerapan ACO nilai SAIDI 333 menit/pelanggan/tahun SAIFI 6 kali/tahun CAIDI 55,5 menit/tahun dan sesudah penerapan ACO nilai SAIDI 0,6 detik/pelanggan/tahun/ SAIFI 3 kali/tahun CAIDI 0,2 detik/tahun. Pada gardu E70 sebelum penerapan ACO nilai SAIDI 365 menit/tahun/pelanggan SAIFI 5 kali/tahun CAIDI 73 menit/tahun dan sesudah penerapan ACO nilai SAIDI 0,6 detik/ pelanggan/tahun SAIFI 3 kali/tahun CAIDI 0,2 detik/tahun. Pada gardu K155 N sebelum penerapan ACO nilai SAIDI 423 menit/pelanggan/tahun SAIFI 6 kali/tahun CAIDI 70,5 menit/tahun dan sesudah penerapan ACO nilai SAIDI 0,6 detik/pelanggan/tahun SAIFI 3 kali/tahun CAIDI 0,2 detik/tahun.

Continuity is needed in distributing electric power. To reduce the duration of blackouts for customers at PT. PLN (Persero) UP3 Kramat Jati Area, namely by applying the Automatic Change Over (ACO) cubicle. The purpose of this study is to determine the simulation of testing on Automatic Change Over (ACO) cubicles, reliability before and after application of Automatic Change Over (ACO) cubicles where this requires disturbance data before application of ACO cubicles and disturbances after application of ACO cubicles, and long duration. blackout. The method used to establish a reliability index. Average Interruption Duration Index (SAIDI) System Method, Average Interruption Frequency Index (SAIFI) System, Customer Average Interruption Duration Index (CAIDI) method. Calculation results at the E325 N substation before the application of ACO the SAIDI value of 333 minutes/customer/year SAIFI 6 times/year CAIDI 55.5 minutes/year and after the application of ACO the value of SAIDI 0.6 seconds/customer/year/ SAIFI 3 times/year CAIDI 0.2 seconds/year. At the E70 substation before the application of ACO the SAIDI value of 365 minutes/year/SAIFI customers 5 times/year CAIDI 73 minutes/year and after the application of ACO the SAIDI value of 0.6 seconds/customer/year SAIFI 3 times/year CAIDI 0.2 seconds/year . At the K155 N substation before the application of ACO the SAIDI value of 423 minutes/customer/year SAIFI 6 times/year CAIDI 70.5 minutes/year and after the application of ACO the SAIDI value of 0.6 seconds/customer/year SAIFI 3 times/year CAIDI 0.2 seconds/year.