Practical Case Study of Electrical Safety Issues within an Imbalanced Three-Phase Power System

Electrical safety is generally referred to when it comes to implementing policies, procedures and the use of Personal Protection Equipment in the execution of any work activity in relation to electrical power and equipment. The above assumes a fully functional protection system and an acceptable quality of supply within the working environment in such a way that in case all the relevant measures are adhered to, personnel would remain in a safe condition. Surprisingly, we have been involved in a specific context - in Southern Africa where, all the above measures were existent but the power supply system from the utility suddenly became imbalanced thus causing some unthought issues such as a considerable difference of potential between transformers’ secondary star point, known as neutral point, and the earth bars. As a result, maintenance personnel became subject to potential electrical shock despite the established safety policies such as the isolation and lockout procedure which mostly consists of isolating live phase conductors only. In addition, switchgears and cables earthing not being a common practice for Low Voltage unlike Medium and High Voltage Systems, the hazard was maintained and correspond risk unchanged. Therefore, using a practical case, this paper aims to highlight the identification of an imbalanced high voltage power system, its probable consequences to the low voltage level and how best they could possibly be mitigated in case users are not in position to fully address the root cause.