The Nynas Nitro Libra Oil Testing as an Isolator on the 150 kV Transformer Using Colour, Water Content, and Breakdown Voltage Testing Method in Bantul Substation - Ardianta, Dimas Septe; Department of Electrical Engineering, Universitas Muhammadiyah Yogyakarta (Universitas Muhammadiyah Yogyakarta, 2019)