Abstract
The power transmission line is the conduit for connecting power stations and substations to transmit electrical energy over long distances. This network is an important component of the electrical grid system and requires attention. A failure on the transmission line reduces the system’s reliability and causes serious economic losses. These interruptions occur often on the transmission lines and eventually require time and effort to restore the system.
Reliability evaluation is one of the most preferred methods considered to assess the efficiency and effectiveness of electric transmission lines. In this study, three different approaches are used to evaluate the steady state of the portion of the Liberia Electricity Corporation network and its dependable performance based on the component outage and network configuration.
In this study, four power transmission lines of different distances (1x9 km, 2x27 km and 1x56 km), all of 66 kV, twelve busbars (1x11 kV, 3x22 kV and 8x66 kV), six power transformers (1x11/66 kV and 5x66/22 kV), and thirty-three circuit breakers were analysed using the ETAP software. Through the evaluation, Load Flow Analysis was performed to determine the voltage magnitude, real and reactive power losses and voltage drops in the system using the Adaptive Newton-Raphson method. Reliability Analysis was used to determine the total system Expected Energy Not Supplied (EENS) and the monetary value of the EENS is identified through the Expected Interruption Cost (ECOST) using a simulation approach. The contingency Analysis model was implemented to identify the impact of outages on the system should any of the transmission lines fails using the Decoupled method.
It can be seen from the results obtained that the approach used has significantly reduced the active power loss by 38.23% (from 665.0 to 410.8 kW) and reactive power loss by 99.68% (from 2819.5 to 9.0 kVAR). It is shown that the methods are efficient for transmission line reliability improvement, voltage stability, active and reactive power loss reduction and increase the system efficiency and sustainability.