Analysis of a new voltage stability pointer for line contingency ranking in a power network (original) (raw)
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The numerous power system blackouts in the past decade and in recent times attest to the fact that more work still needs to be done to tackle the problem of voltage instability and the resultant voltage collapse. This research work proposes a new line stability index that is suitable for the prediction of voltage collapse in Power System Networks (PSNs). This index code-named the New Line Stability Index-1 (NLSI_1) was obtained by deriving from first principles equivalent expressions for the Line Stability Index (Lmn) and the Fast Voltage Stability Index (FVSI) and combining them through a switching logic based on the voltage angle difference since it can signal the imminence of voltage collapse. This new index (NLSI_1) was tested on the IEEE 14-bus system and it gives the same results as the other indices (Lmn and FVSI). For the base case, the IEEE 14-bus test system was found to be stable with all the three indices having approximately equal values (< 1) for all the lines. The contingency case reveals that bus 14 ranks as the weakest bus in the system with the smallest maximum permissible reactive load of 74.6 Mvar and the critical line with respect to bus 14, is the line connecting bus 13 to bus 14. The values of the three indices, Lmn, FVSI and NSLI_1, are approximately equal thereby further validating the accuracy of the new line stability index-1 (NLSI_1).
Ranking of Line Contingency for Voltage Stability Assessment
2019
Excessive reactive power loading results in bus voltage instability and outage of power transmission lines, which leads to instability of the entire power network. For stable operation, finding the stability margin of buses and lines by identifying and ranking unstable lines under contingency is needed. The aim of contingency ranking is to recommend the stability improvement mechanisms for a secure and stable power network operation. This paper introduces a new line stability index that is used to rank lines to identify unstable lines based on the severity of load contingency. In addition, another new technique called Aggregated-Variance Stability Index (AVSI) in combination with adaptive neuro-fuzzy inference system is used to rank the lines based on the severity of line outage contingency due to excessive reactive power loading. Further, to account for the effect of inductive load on bus voltage and power transmission line stability, only load reactive power is increased up to its...
Voltage Stability Index Based on Multi-bus Reactive Power Loading
2021 IEEE PES/IAS PowerAfrica
Voltage stability analysis provides an assessment of the weak, unstable or uncontrollable sections of the power system network that may pose a risk for future load growth due to unexpected voltage collapse. Different methods of determining susceptible buses have been demonstrated over the decades, with V-Q curves being used to determine the critical point and stable operating region of a particular load bus. However, the underlying mutual influences that result from how buses are interconnected, haven’t been correlated directly to the voltage profile and stability of load buses. This paper aims to exploit the combined effect that interconnected load buses have on each other under uniformly distributed multi-bus loading conditions and the conventional method of the sole bus loading analysis to predict better the strength of a load bus by using a V-Q curve-based index. This variable-state-based approach was compared with the inherent network structural-based method giving a broader scope of the system characteristics under various loading states.
Bus voltage ranking and voltage stability enhancement for unbalanced multiphase networks
2012
Voltage instabilities and subsequent system collapses are considered as growing concerns in modern multiphase distribution networks as they are progressively forced to operate closer to their stability limits due to many factors such as increasing load level, lack of reactive power sources, high installation of single-phase shunt capacitors and reverse action of voltage control devices. System operators must be able to quickly identify trouble spots and take corrective steps to avoid critical voltage collapses. To achieve this, suitable indices must be defined to assess system security and take corrective control actions when predefined thresholds are reached. In this regard, the identification and ranking of weak buses in a power system is an important research area. The existing conventional bus voltage ranking indices are only defined for singlephase and balanced three-phase networks. This thesis proposes a new bus voltage ranking index (VRI) to identify the weakest single-, twoa...
Voltage Stability Assessment and Loss Minimisation by Power System Reconfiguration
https://www.ijrrjournal.com/IJRR\_Vol.6\_Issue.8\_Aug2019/Abstract\_IJRR0062.html, 2019
This paper represents a circuit theory approach for voltage stability assessment in an interconnected power system network. The basic methodology implied in this technique is the investigation of each line of the system by calculating line stability indices. Here, an interconnected IEEE 14-bus network has been reconfigured into 12-, 10-and 8-bus networks using graph theory. The line stability index and fast voltage stability indicators have been used for voltage stability assessment under normal and faulted conditions for the original IEEE 14-bus network and the reconfigured i.e. 12-bus, 10-bus and 8-bus networks. Genetic algorithm has been used to determine the optimal operating condition i.e. optimum value of line stability index and fast voltage stability index with best voltage stability for the original and the reconfigured networks. The voltage stability assessment under normal and faulted conditions can be efficiently determined for the reconfigured networks compared with the original network, this has been shown by the results. It analyses the performance of line stability indices. These indices were tested in IEEE 14 bus bar test systems, with satisfactory results. The effect of reconfiguration of 14 bus power system network on power losses in branches and computation time required for finding stability indices has been observed. Also the effect of reactive load variation on stability indices of respective buses and maximum allowable load or maximum loadability of bus is found.
A simple novel method for considering static voltage stability indicator in a power system
The International Conference on Electrical Engineering, 2012
The voltage stability is the ability of the power system to provide adequate reactive power under all operating conditions and to maintain stable load voltage magnitude within specified operating limits. The voltage instability leading to collapse appears to be due to the inability of networks to meet a demand for reactive power at certain critical or weak buses. It can be recognized by noting excessive fall in voltage for small increase in load and increasing difficulty in controlling system voltage. Therefore voltage collapse prediction must take in consideration in power system planning and operation. In this paper a novel indicator from a parallel algorithm will be presented to predict the voltage instability or the proximity of a collapse. The indicator uses the obtained data of a normal load flow to identify the weak buses in the power system. This method has carried out over changing the load power factor. Obtained results for the IEEE 5 bus system considering the effects of STATCOM on voltage stability are presented and discussed.
European Journal of Science and Technology, 2021
There are many situations that cause voltage instability in power systems. One of these situations is line contingency that may occur in power systems. In this study, the effects of line contingency on the steady state are investigated in the IEEE 9 buses power system. Firstly, the static and dynamic analyses of the power system are made in normal operating condition. Continuous power flow analysis was used as static analysis and time domain simulation method were used as dynamic analysis. Then each transmission line is deactivated and the analyses are repeated. The changes in the maximum loading capacity and voltage stability of the system are investigated in case of each transmission line contingency. Finally, Static Var Compensator (SVC) is connected to the power system to improve the stability level. When the SVC is connected to the power system, the maximum loading capacity of the system is examined and the effects of this situation on the voltage stability are analyzed. All an...
Stability analysis of power system under n-1 contingency condition
Bulletin of Electrical Engineering and Informatics, 2024
Several voltage stability indices (VSIs) have been developed to assess the potential for voltage collapse. However, certain indexes are computationally costly. Meanwhile, some have been noted to underperform across various conditions. This work proposes a novel line index called the super voltage stability index (SVSI) to calculate the system's voltage stability margin (VSM). The suggested approach is based on the transmission system's two bus systems. The reactive power loss and N-1 contingency conditions to voltage sensitivity is a unique calculation approach used in this study to identify voltage instability. Day to day, the demand for electric power is being increased due to incessant increments in technology and population growth. Therefore, the power system networks are under pressure. The operational conditions of transmission system networks are affected at this point, which may result in voltage collapse. Regular monitoring of power supply is essential to avert voltage collapse. The effectiveness of the suggested index has been assessed using the IEEE 5 and 30-bus systems across diverse operating scenarios, including variations in active and reactive power loading as well as single line losses. The findings indicate that SVSI provides a more reliable indication of the proximity to voltage collapse when compared to conventional line VSIs.
New method for indicating voltage stability condition in power system
1997
The tendency towards maximising economic benefits has led power systems utilities to run close to the limits of stable operation. This has necessitated thi: study of the stressed situation of the power system network to accomplish efficient energy management without losing its reliability. On-line monitoring of power system stability has become a vital factor for electric utilities. An effective method for real-time monitoring of sy:item status and thus voltage collapse prediction is described. The proposed technique investigstes each line of the system through calculating an indicator that varies from 0 (no load condition) to 1 (maximum permissible loading conditiotl). The basic concept of maximum power transfer through a line is utilised. The proposed contingency evaluation technique is applied on the IEEE 24 bus and IEEE 6 bus reliability test system and is found to be accurate in assessing the stressful status of the lines.