Proses Assessment dan Diagnosis Trafo Tenaga 150/20 kV Gardu Induk PT. PLN (Persero) masih dilaksanakan secara konvensional. Asisten manajer beserta staf engineering harus menerima form pemeliharaan dari tim pemeliharaan basecamp yang sudah terisi dengan data hasil uji pemeliharaan yang berikutnya akan diassessment dan didiagnosis melalui excel. Hal tersebut memerlukan waktu yang lama. Dalam Penelitian ini proses yang bersifat konvensional, diubah menjadi terkomputerisasi berbasis web. Aplikasi Assessment dan Diagnosis Trafo Tenaga 150/20 kV Gardu Induk PT. PLN (Persero) TJBT APP Salatiga dibuat denggan menggunakan metode Extreme Programming sebagai sistem pengembangan perangkat lunak. Beberapa data uji pemeliharaan pada penelitian ini adalah pengujian SFRA, Tahanan Isolasi, Furan dan Tan Delta Bushing. Pada proses assessment dan diagnosis trafo tenaga 150/20 kV akan diterapkan metode Weighting Factor. Namun pada pengujian Tan Delta Bushing akan diterapkan dengan metode Fuzzy Sugeno sebagai pembanding dengan metode Weighting Factor. Hasil penelitian menyebutkan bahwa Aplikasi Assessment dan Diagnosis Trafo Tenaga 150/20 kV Gardu Induk PT. PLN (Persero) TJBT APP Salatiga membantu dalam proses pendataan inventaris trafo tenaga 150/20 kV sampai proses assessment dan diagnosis trafo tenaga 150/20 kV sehingga lebih efisien dan mempersingkat waktu.

The process of the assessment and diagnosis of the power transformer of 150/20 kV in the PLN’s electrical relay station is still done conventionally. The manager’s assistants along with the engineering staff are given the maintenance forms by the basecamp maintenance team containing data of the maintenance experimental result which then will be assessed and diagnosed using the excel. This certainly takes much time. In this study, this conventional process will be converted into computerized system of web based. The assessment and diagnosis application on the power transformer of 150/20 kV in the PLN’s electrical relay station TJBT APP Salatiga is made using Extreme Programming method as the software development system. The data of maintenance test in this study are based on the testing of the SFRA, Isolating Resistor, Furan and Tan Delta Bushing. The Weighting Factor method will be applied for the process of assessment and diagnosis of the power transformer of 150/20 kV. For the testing of the Tan Delta Bushing, the Fuzzy Sugeno method is applied as a comparison to the Weighting Factor. The result shows that the assessment and diagnosis application on the power transformer of 150/20 kV in the PLN’s electrical relay station TJBT APP Salatiga is very helpful in the process of inventory recording assessing and diagnosing of the 150/20 kV power transformer so it is efficient and takes less time.