scope:

Scope and object

This standard is applicable to dependent specified time electrical measuring relays which protect equipment from electrical thermal damage by the measurement of current flowing in the protected equipment.

This standard covers the following two types of relays:

a) thermal electrical relays having a total memory function of the load-current conditions before the conditions which caused the switching of the relay;

b) thermal electrical relays having a partial memory function, i.e. of the overload current conditions only.

This standard also covers the particular requirements for thermal electrical relays used for motor protection.

The object of this standard is to state the particular requirements for thermal electrical relays. It is to be read in conjunction with higher level documents in the IEC Publication 255 series.