A practical on-line zone substation busbar load and power factor estimator

Abstract

In Hongkong Electric, electricity is transmitted from power station to zone substations and distributed from zone substation busbars to customers through a number of feeders and distribution transformers Zone substation busbar splitting is frequently carried out as one of the steps of parallel switching operations for such purposes as equipment outage, supply source re-arrangement or load transfers. However, voltage fluctuation will be caused due to the re-distribution of reactive power between zone transformers. Therefore, a practical and fast method has been developed to estimate zone substation busbar load and power factor as a simple but useful online tool. The principle of the zone substation busbar load and power factor estimation is based on the fundamental rule that total injection and load within a parallel transformer group must balance. Using telemetry providing partial measurements on boundaries of the concerned busbars, the most likely solution is identified by the proposed method. This paper describes the on-line estimation of zone substation busbar loads and their power factors without installing any additional transducers directly to the busbars. The estimation is accurate enough to assist System Control Engineers to maintain power supply quality by preventing significant voltage fluctuation caused by reactive power re-distribution during day-to-day busbar interconnector switches operations. The results also improve quality of data used in advanced network applications. (5 pages)