Abstract
In recent years, the Kenyan Power Network has witnessed large growths in load demand. Although the increased load demand has somewhat been matched with an increase in transmission and generation capacity, the rate of expansion has not been matched with the rate of increase in load demand due to economic, environmental, and geographical constraints. This has led to the system being prone to instability since it is being operated under stressed conditions. In the recent past, several studies have been carried out on voltage stability analysis and improvement using various conventional methods. However, conventional methods have various limitations in their utilization for voltage stability analysis. One solution to overcome these limitations is to employ a combination of one or more methods so as to get more information and greater degree of accuracy in voltage stability studies. In this paper, a methodology is proposed involving the combination of QV modal analysis, sensitivity analysis (VQ) and power-voltage curves in assessing the static voltage stability analysis taking a case study of the Kenyan Power Network. V-Q sensitivity analysis and QV modal analysis have been used to identify the load regions most susceptible to voltage instability and the corresponding weak buses in the network for various V-Q responses. Reactive power loss sensitivities for branches in the network have been used to determine the critical (weak) lines in the network. Loading margins (LM) and voltage stability margins (VSM) have then been used to determine the proximity to voltage collapse of the voltage weak buses identified by QV modal analysis. The effect of tripping one the critical lines on the voltage weak buses is also investigated. The current high voltage power network under the average peak loading conditions during the year 2019 is considered for the study. The paper also reviews existing voltage stability analysis methods and their limitations.
Highlights
Due to economic and environmental constraints, bulk power systems are increasingly being operated close to their limits which have made them more prone to instability and power quality challenges
A methodology is proposed involving the combination of QV modal analysis, sensitivity analysis (VQ), and power-voltage curves used to assess the static voltage stability status of the Kenyan Power Network
A methodology is proposed for carrying out static voltage stability assessment in bulk power systems. e methodology is employed in the assessment of the static voltage stability status of the Kenyan Power Network based on a model of the system as of 2019 has been carried out
Summary
Due to economic and environmental constraints, bulk power systems are increasingly being operated close to their limits which have made them more prone to instability and power quality challenges. Voltage instability is one of the problems that has gained notoriety in recent years. It has been recognized as one of the major sources of power system insecurity and has been responsible for several partial or full power interruptions over the past decades. More than 50 cases of voltage collapse have been reported around the world in the past 50 years. Notable incidents of interruptions that arose from voltage instability include the ones of France (1978), Belgium (Aug 1982), Sweden (Dec 1983), Tokyo, Japan (July 1987), USA Tennessee (Aug 1987), Canada (March 1989), and the USA’s WSCC power grid blackouts (July 2 and Aug. 10 1996). Some of the incidents reported over the years are presented in Table 1 together with the time frames and total load interruptions reported [2,3,4,5,6,7,8,9,10]
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