Research has been carried out on the load imbalance analysis on the transformer with the aim of knowing the percentage of load imbalance on the transformer. From the results of the analysis that has been carried out, it is known that the percentage of transformer loading is unbalanced and is in bad condition because it exceeds the balance standard that has been set, which is above 25% with a percentage for line 1 of 60% during the day and 80% at night. While on line 2 has a percentage of 35% during the day and 33% during the day.

In the process of distributing electricity from the generator to the consumer, it goes through many processes and passes through several parts. Starting from the electric power distribution system, one of which is the distribution system. Considering that the scope of this distribution network is directly related and is located in an inhabited area, in addition to meeting technical quality requirements, it must also meet the requirements for being safe for users and familiar with the environment. In this distribution system there is a very important equipment in distributing electric power, namely the distribution substation. Because of the important role of the distribution substation, it must be protected from disturbances that may occur. One of them is the load imbalance between phases. In practice and in reality, in various locations of electric power distribution, a completely balanced load condition is obtained, mainly because of the large number of single-phase load groups that are serviced by a low-voltage three-phase distribution system. This is because the characteristics and types of electrical power user equipment vary with different consumer conditions and activities. To obtain load balance, load balancing is carried out between phases for load distribution so that load adjustments occur at distribution substations.

Penurunan tegangan secara cepat dan dengan waktu sesaat yang disebabkan oleh hubung singkat dan starting motor dapat menyebabkan terjadinya penurunan tegangan atau yang biasa di sebut dengan voltage sag.Selain penurunan kualitas tegangan sering pula terjadi gangguan tegangan berlebih yang sering di akibatkan oleh gangguan surja hubung, fasa to fasa serta kebocoran pada isolator.Jika tidak diproteksi dengan baik dapat menyebabkan kerusakan pada peralatan. Berdasarkan standar 1159-1995 IEEE,merekomendasikan untuk memonitoring kualitas daya listrik baik tegangan rendah dan tegangan lebih yakni  penurunan dan kenaikan rms pada pergeseran 10- 90% untuk nilai amplitude selama 0,5 cycle hingga kurang dari satu menit. Oleh sebab itu untuk meningkatkan performa sistem proteksi perlu dilakukan analisis terhadap setelan dan hubungan relay  yang ada khususnya relay proteksi arus lebih dan relay proteksi tegangan.Metode yang digunakan pada penelitian ini adalah eksperimental dengan membuat rancang bangun sistem proteksi tegangan 220 volt menggunakan relay proteksi tegangan kemudian melakukan analisis menggunakan fishbone dan SWOT. Hasil dari penelitian ini diperoleh bahwa rangkaian ini dapat bekerja memutuskan arus gangguan ketika relay telah membaca arus gangguan tersebut sesuai dengan persentase pada masukan relay berdasarkan nominal tegangan gangguan. Jenis relay yang digunakan pada rangkaian ini mempunyai karateristik time delay dengan jenis definite time yang berguna untuk memproteksi berbagai gangguan yang dapat menyebabkan kerusakan.