The VT3 series of voltage transformers-sensors are designed for pole top use and intended to use for low power remote control- measurement applications in medium Voltage networks from 3-27kV. It has one phase to phase connected transformer and three Y-Y connected resistive voltage dividers.  
Modern oil-insulated voltage transformers are suitable for power supply of various remote controlled switches, autoreclosers, motor actuators, remote terminals, radio equipment, etc.
Oil-insulated transformers are most suitable for AMS work, as the fault risk is very limited.
They are made of SIS 2333 stainless steel for best corrosion protection.
The transformer has a core of composite material and an outer shell of silicone rubber. Silicone rubber protects very effectively against UV light and ensures long durability for many years of operation.