Assessment and modeling of grid related factors that influence quality of supply to industrial customers

Abstract

Industrial development is directly linked to the growth of a country’s economy. As Uganda claims to approach middle income status by 2020, it was imperative to look at grid related factors that influence quality of supply to industrial customers. This is because industrial customers constitute 9% of the customer base but consume 74% of the power produced. Hence when the quality of supply improves for the minority group of customers, then this will ensure sustainable economic growth.

The research involved soliciting responses from customers using questionnaires, observation of network assets in the field and analysis of existing data on the performance of the power supply. An electrical model was developed to simulate the impact of changes in asset management practices on power quality. Reliability of power supply was analysed using Monte Carlo Simulation in Matlab programme. The research was conducted on Umeme Limited network of Natete District. Findings from the research revealed that 19% of the transformers were leaking and required preventive maintenance and 18% had one or more surge arrestors missing hence not properly protected against lightning. Of all the structures inspected, 2% had rotten poles and 11% required line clearance due to tree branches approaching or touching the power lines. These findings reveal signs of poor asset management practices which negatively affects the quality of supply to industrial customers.

It was demonstrated that poor asset management practices due to inadequate maintenance negatively impact on power quality for industrial customers due to increase in contact resistance as a result of poor fusing, poorly made jumpers and joints. When resistances changes by 0.01ohms, voltage for medium industrial customer changes from 237.8V to 234.5V representing 1% drop in voltage. However further increase in resistance is likely to cause the voltage to drop below 6% which is the grid code threshold. The change in resistance significantly affect medium industrial and commercial customers compared to heavy industrial customers. Poor asset management practices reduce the mean time to failure of electrical components which reduces the overall reliability of the supply. A component which takes 1 year (8760 hours) to operate without breaking down will have a reliability of 0.977. However due to poor asset management practices, the component may break down say after 6000 hours which then reduces its reliability to 0.964. Good asset management practices therefore improves power quality by minimizing contact resistance and reliability by good maintenance practices for industrial customers.