Abdullah Asuhaimi Mohd Zin

A novel method for ATC computations in a large-scale power system

In a restructured power system, it is the responsibility of the independent system operator (ISO) to control the power transactions and avoid overloading of the transmission lines beyond their thermal loading megavolt-ampere (MVA) limits. For this, ISO has to update periodically a real-time index termed available transfer capability (ATC). The methods reported to date for ATC determination are unable to cater to either the accuracy or the online CPU time requirements when the system is a large one. This paper proposes a novel method with the full details for determining ATC in a large power system from only three input variables through fuzzy modeling. The method is validated through extensive simulation tests on the standard IEEE 24-bus reliability test system (RTS), and comparison with an ac load flow-based conventional method using the same array of transactions, base cases, and generation/line outages.

Reconfiguration of Radial Electrical Distribution Network Through Minimum-Current Circular-Updating-Mechanism Method

Reconfiguration of the Radial Electrical Distribution Network (ROREDN) is one vital analysis to optimize and control the electrical distribution system. This paper presents a new heuristic method for ROREDN based on minimum branch current in the system. A circular updating mechanism is presented in which every open switch is acquired and updated. The proposed technique has been tested and compared to other existing ones on four hypothetical electrical distribution networks. The method has remarkably solved the problems accurately with fast computational times.

Two Circular-Updating Hybrid Heuristic Methods for Minimum-Loss Reconfiguration of Electrical Distribution Network

This paper presents two hybrid heuristic methods for reconfiguration of the radial electrical distribution system. The first stage of the proposed techniques is a circular minimum-branch-current updating mechanism to bypass the local optimum points. Then, by a circular neighbor-chain updating technique, the best known configuration is obtained. The proposed approaches have been tested on the six well-known electrical distribution networks. The results show that the proposed methods have remarkably achieved the best-known optimum solution with more reliability, accuracy and efficiency than many other published methods.

New algorithm for detection and fault classification on parallel transmission line using DWT and BPNN based on Clarke's transformation

This paper presents a new algorithm for fault detection and classification using discrete wavelet transform (DWT) and back-propagation neural network (BPNN) based on Clarkes transformation on parallel transmission. Alpha and beta (mode) currents generated by Clarkes transformation were used to convert the signal of discrete wavelet transform (DWT) to get the wavelet transform coefficients (WTC) and the wavelet energy coefficient (WEC). Daubechies4 (Db4) was used as a mother wavelet to decompose the high frequency components of the signal error. The simulation was performed using PSCAD/EMTDC for transmission system modeling. Simulation was performed at different locations along the transmission line with different types of fault and fault resistance, fault location and fault initial angle on a given power system model. Four statistic methods utilized are in the present study to determine the accuracy of detection and classification faults. The results show that the best Clarke transformation occurred on the configuration of 12-24-48-4, respectively. For instance, the errors using mean square error method, the errors of BPNN, Pattern Recognition Network and Fit Network are 0.03721, 0.13115 and 0.03728, respectively. This indicates that the BPNN results are the lowest error.

Fuzzy Timing Petri Net for Fault Diagnosis in Power System

A model-based system for fault diagnosis in power system is presented in this paper. It is based on fuzzy timing Petri net (FTPN). The ordinary Petri net (PN) tool is used to model the protective components, relays, and circuit breakers. In addition, fuzzy timing is associated with places (token)/transition to handle the uncertain information of relays and circuits breakers. The received delay time information of relays and breakers is mapped to fuzzy timestamps, π(τ), as initial marking of the backward FTPN. The diagnosis process starts by marking the backward sub-FTPNs. The final marking is found by going through the firing sequence, σ, of each sub-FTPN and updating fuzzy timestamp in each state of σ. The final marking indicates the estimated fault section. This information is then in turn used in forward FTPN to evaluate the fault hypothesis. The FTPN will increase the speed of the inference engine because of the ability of Petri net to describe parallel processing, and the use of time-tag data will cause the inference procedure to be more accurate.

A review on reconfiguration of radial electrical distribution network through heuristic methods

Reconfiguration of Radial Electrical Distribution Network (ROREDN) is one vital analysis to optimize and control the electrical distribution system. This paper explained the application and objectives of ROREDN. There are considerable Heuristic Methods (HMs) presented by researcher for ROREDN as optimization approaches. This paper also reviewed some important strategies of HMs. The research represents that in the case of optimization methods, HMs could have remarkably solved the problems simple with fast computational times.

A comparison of voltage stability indices

The stressful condition of power system and high transmission losses leads to voltage security and reliability problems of system operation. If the voltage stability is not assessed and the problems occurred are not mitigated properly, cascading events may occur and this may lead to voltage collapse or blackout events. Therefore, there is a need to assess the voltage stability in order to detect the voltage collapse point and mitigate it when it occurs. This paper aims to compare four existing voltage stability index performance towards reactive and real power load changes. The performances are analyzed theoretically, and using simulation on IEEE 30-bus test system. Total power loss is also observed for each case. The comparison shows that all indices are prone to either reactive or real load power changes only. None of the indices are sensitive towards both power loads changes. Meanwhile, the total power loss is mostly contributed by reactive power losses.

Optimal Sizing and Siting of Distributed Generators by a Weighted Exhaustive Search

Abstract Dispersed generation generally refers to power generation on the customer side of the power network. This article demonstrates the improvement in network parameters that could be achieved by the usage of single and multiple distributed generation (DG) units in three selected standard networks. A reliable multi-variable method is suggested for finding the optimal installation point and size of distributed generation units. Their sites and sizes are recognized by the implementation of the proposed method with an exhaustive search. Optimization is applied on network total active and reactive losses together with voltage variation. IEEE 6-, 14-, and 30-bus standard networks are selected as study cases. The total active and reactive power losses are minimized, while the voltage profile is improved by installing distributed generation units on the recognized optimal points with the achieved optimal size.

The Application of Fault Signature Analysis in Tenaga Nasional Berhad Malaysia

Unplanned electrical power outages are a major concern to power utilities throughout the whole world. Unfortunately, power outages will continue to occur and they cannot be fully prevented. It could be the result of lightning strikes, tree encroachment, or equipment failure. However, the impact can be reduced if power system operators are equipped with the appropriate tools to analyze the root cause of the failure. Without sufficient tools to identify the nature of a fault, the restoration process could be delayed because the operator does not know whether it is safe to normalize the isolated line. This paper describes the new and simplified fault signature analysis approach on Tenaga Nasional Berhad using a digital fault recorder. The research focuses on the contribution of the lightning strike and tree encroachment to the overhead line tripping in Malaysia.

The Utilization of Digital Fault Recorders in Protection System Analysis on Tenaga Nasional Berhad Transmission System

The protection system is a very critical element in a power system. It is security to the power system for isolating only the faulty plant as fast as possible. A simple fault can lead to a cascade of tripping if it is not isolated accurately and fast enough by the protection system. Furthermore, protection system analysis is a complicated task for inexperienced engineers. Most of the analysis relied mainly on the relay indications which could lead to incorrect analysis due to the uncertainty of the correct relay operations and time tagging. Therefore, it is an urgent requirement to explore protection system analysis to improve system reliability. This paper describes a method of early detection of protection system failures in Tenaga Nasional Berhads Transmission Grid using digital fault recorders. The method has demonstrated to be more accurate, thus enabling faster decision making and shorter interruption time.