UR 56 The UR 56 transformers are designed for installation in connector heads and surge arresters, including:
UR 66 The UR 66 transformers are intended for installation in connector, coupling heads, and surge arresters, such as:
UR 90 The UR 90 transformers are designed for installation in connector heads compliant with PN-EN 50180 and PN-EN 50181 standards, Interface C, 630 A.