HANIFIAH, HABIB (2025) PENGARUH PENGGANTIAN DAN PENGUATAN ISOLASI NEUTRAL GROUNDING RESISTOR (NGR) 12 OHM TERHADAP GANGGUAN ARUS NETRAL TRAFO DAYA 60 MVA PADA GARDU INDUK TELUK NAGA. S1 thesis, Universitas Mercu Buana Jakarta.
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Abstract
Neutral Grounding Resistor (NGR) plays an important role in the electrical system to reduce neutral current disturbances (ground fault current) that will flow in the windings of power transformers. This study focuses on the effect of replacing and strengthening NGR insulation on the reliability of a 60 MVA power transformer at the Teluk Naga Substation. The problem found was the occurrence of a neutral current disturbance of 11.2 kA which caused a flashover, thus reducing the resistance value of the NGR element from 12 Ohm to 4.6 Ohm. This flashover was also caused by the low insulation resistance value, which was 41.9 Mohm, far below the standard of 100 Mohm and the high neutral current surge within 0.33 seconds. This study uses quantitative and descriptive methods by calculating the comparison of the resistance of the NGR element to the current entering the power transformer when a neutral current disturbance occurs using a new NGR, Flashover NGR, without NGR and explaining the effect of Isolation resistance on the NGR on NGR flashover and the mechanism for replacing the Flashover NGR with a new NGR by re-stabilizing the power transformer. The results of the study showed that replacing the new NGR with a resistance of 12 Ohm according to the PT PLN (Persero) standard was able to reduce the fault current entering the power transformer by up to 0.861 kA, compared to still using the NGR flashover of 2.135 kA, and without the NGR it was worth 13.135 kA. In addition, insulation reinforcement was carried out to increase the insulation resistance value of the NGR to 122 Mohm and testing the stability of the differential relay protection and REF to ensure the stability of the Current Transformer (CT) circuit. So the importance of element resistance and insulation reinforcement on the NGR as a step to improve the reliability of the power transformer protection system. The implementation of this strategy not only prevents flashover, but also reduces the impact of neutral current disturbances flowing in the power transformer windings, thereby increasing the durability and service life of the power transformer. Keywords: Neutral Current, Flashover, Neutral Grounding Resistor (NGR), Element Resistance, Insulation Resistance, Power Transformer. Neutral Grounding Resistor (NGR) berperan penting dalam sistem kelistrikan untuk meredam gangguan arus netral (ground fault current) yang akan mengalir pada belitan trafo daya. Penelitian ini berfokus pada pengaruh penggantian dan penguatan isolasi NGR terhadap keandalan trafo daya 60 MVA di Gardu Induk Teluk Naga. Permasalahan yang ditemukan adalah terjadinya gangguan arus netral sebesar 11,2 kA yang menyebabkan flashover sehingga menurunkan nilai resistansi elemen NGR dari 12 Ohm menjadi 4,6 Ohm. Flashover ini diakibatkan juga oleh nilai resistansi isolasi yang rendah, yaitu 41,9 Mohm, jauh di bawah standard yaitu 100 Mohm serta lonjakan arus netral gangguan yang tinggi dalam waktu 0,33 detik. Penelitian ini menggunakan metode kuantitatif dan deskriptif dengan cara menghitung perbandingan resistansi elemen NGR terhadap arus yang masuk ke trafo daya saat terjadi gangguan arus netral dengan menggunakan NGR baru, NGR Flashover, tanpa NGR serta menjelaskan pengaruh resistansi Isolasi pada NGR terhadap flashover NGR dan mekanisme penggantian NGR Flashover dengan NGR baru dengan cara stability ulang trafo daya. Hasil dari penelitian menunjukkan bahwa penggantian NGR baru dengan resistansi 12 Ohm sesuai standard PT PLN (Persero) mampu menurunkan arus gangguan yang masuk ke trafo daya hingga 0,861 kA, dibandingkan dengan masih menggunakan NGR flashover sebesar 2,135 kA, dan jika tanpa NGR bernilai 13,135 kA. Selain itu, dilakukan penguatan isolasi agar meningkatkan nilai resistansi isolasi NGR menjadi 122 Mohm dan pengujian stability proteksi relai diferensial dan REF untuk memastikan stabilitas rangkaian Current Transformer (CT). Sehingga pentingnya resistansi elemen dan penguatan isolasi pada NGR sebagai langkah untuk meningkatkan keandalan sistem proteksi trafo daya. Implementasi strategi ini tidak hanya mencegah flashover, tetapi juga mengurangi dampak gangguan arus netral yang mengalir pada belitan trafo daya, sehingga meningkatkan ketahanan dan umur pakai trafo daya. Kata Kunci: Arus Netral , Flashover, Neutral Grounding Resistor (NGR), Resistansi Elemen, Resistansi Isolasi, Trafo Daya.
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