Bangunan menara Radio PRO 1 LPP RRI Tarakan yang terletak di Jl.Gn.Amal setinggi 70 m sangat rentan tersambar petir secara langsung yang dapat menyebabkan kenaikan tegangan yang dapat merusak peralataan radio. Sambaran tak langsung juga dapat mengakibatkan timbulnya induksi yang dapat merusak peralatan elektronik pada daerah tersebut.Dengan analisa perhitungan menggunakan metode sudut proteksi didapatkan hasil perhitungan kepadatan sambaran petir 8,77 sambaran /km2-tahun, arus petir maksimum sebesar 4.527,88 kA, kecuraman maksimum arus petir sebesar 434,80 kA/µs. kemampuan finial melindungi sejauh 441,1 m. dari hasil perhitungan didapatkan nilai pembumian menara telekomunikasi ini sudah rendah yaitu sebesar 0,995 ohm . Dengan arus petir yang menyambar finial dan disalurkan melalui down conductor maka di sekitar down conductor terjadi tegangan induksi ke peralatan BTS yang nilainya sebesar 38,697kV.

Kata kunci : Sistem Proteksi Petir, Sistem Pembumian, Menara Radio PRO 1 RRI Tarakan.

Lightning is a common natural phenomenon in Indonesia. It is an unpredictable natural phenomenon. Lightning is an important problem to deal with, because it can damage and even kill living creatures. A telecommunication tower building on J1. Gn. Amal Tarakan is the tallest tower in the area. It is 70 m tall, standing on a hill and the area is densely populated. This tower is very vulnerable to a direct lightning strikes which potentially cause a sudden voltage hike. This can damage the devices. Indirect strikes can cause induction which damage electronic equipment in the area. With a lightning strike density of 8.77 strikes/km2-year, the maximum lightning current is 4,527.88 kA, the maximum steepness of the lightning current is 434.80 kA/gs. A finial ability to protect is as far as 441.1 m. The calculation results, the grounding value of the tower is already low, which is 0.995 ohms. With the lightning current that strikes the finial, channeled through the down conductor. By which around down conductor, there is an induced voltage to the BTS equipment with a value of 38.697kV.. Keywords: Lightning Protection System, Grounding System, Telecommunication Tower.