Detection of loss of voltage phase

The loss of a single phase of a voltage can occur from multiple causes such as the loss of a fuse, failed connections or downed conductors. This condition will cause negative sequence current to flow in motor circuits and may damage those motors. It is desirable to detect the loss of a voltage phase from a utility source and trip an industrial facility before the unbalanced voltages can damage motors. This paper examines the amount of negative sequence voltage and current generated by the loss of a voltage phase by analyzing the sequence networks created by the open condition. The paper also describes when detection of this condition is most appropriate using negative sequence voltage techniques and negative sequence current elements.