Characterisation of Power Quality Problems on the 11kV Distribution Network in Port Harcourt, Rivers State

This study characterises the power quality problems prevalent on the 11kV distribution network serving industrial and commercial consumers in Port Harcourt, Rivers State, South South Nigeria. Poor power quality, encompassing voltage sags, swells, harmonics, and supply interruptions, imposes significant costs on industrial consumers through equipment damage, process disruptions, and increased energy consumption. Field measurements were conducted at ten 11kV feeder termination points across three distribution substations in the Trans-Amadi and Rumuola industrial areas over a four-week monitoring period using a calibrated power quality analyser compliant with IEC 61000-4-30. Measurements recorded voltage magnitude variations, total harmonic distortion, power factor, and interruption frequency. Results indicate that voltage sags below 90 percent of nominal occur an average of 14 times per day per feeder, significantly exceeding the acceptable threshold defined in the Nigerian Electricity Regulatory Commission's quality of supply regulations. Total harmonic distortion at bus level averages 8.6 percent, predominantly driven by the 5th and 7th harmonic orders associated with variable speed drives and uninterruptible power supply loads within the industrial estate. Power factor at all monitored feeders falls below 0.85, indicating reactive power compensation deficiency. The study maps the spatial distribution of power quality problems across the monitored network and identifies loading imbalance and ageing transformer impedances as contributing factors. Recommendations include the installation of passive harmonic filters, power factor correction capacitor banks, and on-load tap changers at the identified substations. Keywords: power quality, voltage sag, harmonics, distribution network, Port Harcourt.