Indoor Current Transformer Cable Type
Transformers KOLMA_ are suitable for the measurement of the sum of three-phase currents in a 3-phase cable. Under normal operating conditions this sum is zero. In the event of an earth-fault the sum of the currents is equal to the earth-faul current and a corresponding current flows in the secondary.
These transformers are used together with static earth-fault relays. The cable current transformers can generally be used when measuring the residual current e.g. to prewarn of, or locate an earth-fault. An uninsulated busbar or low voltage cable serves as the primary conductor.