Keandalan pada sistem distribusi tegangan menengah mudah sekali terpengaruh oleh gangguan-gangguan, seperti gangguan fasa ke tanah dan gangguan antar 2 fasa atau 3 fasa yang biasanya diakibatkan oleh petir, hewan, atau pepohonan. Akibat dari gangguan tersebut adalah besarnya arus gangguan melebihi batas arus nominal transformator. Untuk mengamankan jaringan dari gangguan antar fasa maka diperlukan over current relay (OCR) sehingga transformator tetap aman walau terjadi gangguan tersebut pada jaringan distribusi. Kata Kunci: Gangguan antar fasa, Sistem distribusi, OCR.

The reliability on distribution system of medium voltage is very easy to influenced from disturbances, such as phase to ground disturbance and phase to phase or amongst 3 phases which is actually caused by thunder, animals, or trees so that cause a fault of system which can damage the transformer or other component because enormity of disturbance current surpass the limit of nominal current of that component. To secur esystem from amongst phases disturbance so it's required a system of protection, namely overcurrent relay (OCR) which is used for securing system from short circuit disturbance, so the transformer or other component still safe although disturbance amongst phases occurs on system distribution. Keywords: Interphase Fault, Distribution System, OCR.

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