Current Transformers – How to specify them?

Protection, control and monitoring

Electrical power management requires implementation of data processing units able to monitor networks or equipment and, as applicable, to initiate the appropriate actions…

The protection plan must specify the operating or non-operating conditions for all the protections during a fault and during normal operation (transients). It must indicate the protection settings.

However, the plan rarely indicates the characteristics of the protection input circuit and other data necessary to specify the current transformers (CT). This is because it is often very hard for the designer to collect all the necessary data.

The consequences on industrial start-up can be serious: unsuitability, overrating, non-standard specifications and high costs, addition of matching CTs, last minute CT changes, postponement of delivery, commissioning, production times, etc.

More serious still, incorrect definition can lead to malfunctions in the protection channel causing destruction of equipment or, worse still, danger for the operator.

AUTHOR: Schneider Electric expert | Paola FONTI