Outdoor Oil cooled Current Transformer Oil cooled transformers are made for use on various systems ranging from 11kv to 33kv. the basic construction of the CT is similar to CT of all voltage classes in that the core is placed in a tank mounted on top of the bushing and adequate paper insulation is provided on it. The secondary leads are run through the bushing to the secondary terminal box placed at the bottom of the bushing. Typical specification for a 11 kV CT System voltage:11 kV Insulation level voltage (ILV) : 12/28/75 kV Ratio: 200/1 - 1 - 0.577 A Core 1: 1A, metering, 15 VA/class 1, ISF<10 Core 2: 1 A, protection, 15 VA/5P10 Core 3: 0.577 A, Class PS, KPV>= 150 V, Imag at Vk/2 <=30 mA, RCT at 75 C<=2 ohms Short time rating:20 kA for 1 second