The differential earth relays ELR can be connected to the following toroidal current transformers:

• CTD-1/28 Ø hole 28mm
• CTD-2/29 Ø hole 29mm
• CT-1/22 Ø hole 22mm
• CT-1/35 Ø hole 35mm
• CT-1/60 Ø hole 60mm
• CT-1/80 Ø hole 80mm
• CT-1/110 Ø hole 110mm
• CT-1/160 Ø hole 160mm
• CT-1/210 Ø hole 210mm
• CT-1/300 Ø hole 300mm
• CT-1/280R Ø hole 280mm
• CT-1/350R Ø hole 350mm
• CT-1/415R Ø hole 400mm
• CTA-1/110 Ø hole 110mm (openable)
• CTA-1/160 Ø hole 160mm (openable)
• CTA-1/210 Ø hole 210mm (openable)
• CTA-1/300 Ø hole 300mm (openable)

They must be crossed by the cables of the line to be controlled; insert the phases and neutral if present. The earth cable must NOT cross the current transformer.

NOTE: Twist the connection wires between the toroid and the relay, keep them away from the power cables, and in the presence of strong electromagnetic fields use a shielded lead. Separately twist the pair of signal cables (terminals 1-2) from the control circuit pair (terminals 3-4) where present. Reduce the distance between the toroid and the relay to the minimum.