Motor branch circuit health monitoring method

An apparatus, comprising:

• at least one processor;
• at least one memory including computer program code, wherein the computer program code, when executed by operation of the at least one processor, performs an operation comprising:
• calculating, by a three-phase protective device, an expected current unbalance, as a product of a measured voltage unbalance times an expected ratio of current unbalance to voltage unbalance for a three-phase load;
• calculating, by the three-phase protective device, an expected threshold current unbalance indicating a potential fault caused by unbalanced currents, as the expected current unbalance plus a value of unbalance tolerance/sensitivity;
• determining, by the three-phase protective device, whether a measured current unbalance exceeds at least one of the expected current unbalance or the expected threshold current unbalance;
• and
• providing, by the three-phase protective device, an action for the three-phase load, based on the determination.

A computer program product comprising computer executable program code recorded on a computer readable non-transitory storage medium, the computer executable program code comprising:

• code for calculating, by a three-phase protective device, an expected current unbalance, as a product of a measured voltage unbalance times an expected ratio of current unbalance to voltage unbalance for a three-phase load;
• code for calculating, by the three-phase protective device, an expected threshold current unbalance indicating a potential fault caused by unbalanced currents, as the expected current unbalance plus a value of unbalance tolerance/sensitivity;
• code for determining, by the three-phase protective device, whether a measured current unbalance exceeds at least one of the expected current unbalance or the expected threshold current unbalance;
• and
• code for providing, by the three-phase protective device, an action for the three-phase load, based on the determination.