The principles of energy conservation by managing facility voltage levels and reactive power flow

Abstract

Reactive power optimization and voltage control are essential for the efficient operation of power systems. Effective management of these factors reduces energy losses and improves both economic performance and system security. In South Africa, the nominal phase voltage level is set at 220V, with an allowable range between 209V and 231V (±5 %). To ensure that the supply voltage stays within this acceptable range, the grid often provides a voltage higher than the nominal 220V at which most electrical equipment is designed to operate. Consequently, the equipment consumes more power without any improvement in performance. Additionally, while the grid supplies both real and reactive power, only the real power consumed is billed. To address the cost of unbillable reactive power, a power factor penalty is implemented. The practice of controlling supply voltage levels and enhancing the power factor is known as volt-var optimization. This approach involves regulating voltage levels and reactive power to maximize energy efficiency. This paper employs a model-based Volt-var optimization technique to illustrate how facilities can reduce energy waste. The findings indicate that, for facility system losses estimated at 5 %, reducing the useable voltage from 400V nominal to 380V can achieve a percentage loss reduction of 0.487 %. This saving is directly proportional to the difference between the useable and nominal voltages. Furthermore, optimizing the power factor from 0.85 lagging to unity results in a percentage loss reduction of 1.388 %. This saving is indirectly proportional to how closely the inherent power factor approaches unity.