A New Techniques of Differential Relaying the Differential Relay
TL;DR: In this paper, a new technique of differential protection is proposed which considers only fault contribution currents through the use of microcomputer cancellation of the prefault through currents, which is substantially more sensitive to high impedance faults than the standard arrangement.
Abstract: Standard percentage differential relaying with through current restraint is insensitive to high impedance (i.e. low fault current) faults when applied to apparatus which experience substantial, near 1.0 pu, prefault through currents. A new technique of differential protection is proposed which considers only fault contribution currents through the use of microcomputer cancellation of the prefault through currents. This new form of differential relaying maintains the external fault selectivity of standard percentage differential relaying, has a large buffer zone between the tripping and restraint zones of relay operation, and is substantially more sensitive to high impedance faults than the standard arrangement. This paper presents the theory for this relay, a simplified analysis of the effects of CT errors on the relay operation, and the experimental results for a real time laboratory version of the relay using a 16-bit single- board microcomputer.
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TL;DR: The fuzzy logic based multi-criteria protective relay for a three-phase power transformer is presented and shows significant gains in both sensitivity and selectivity of the self-organized relay compared with traditional approaches.
Abstract: In the paper the fuzzy logic based multi-criteria protective relay for a three-phase power transformer is presented. Twelve criteria used to stabilize the relay are introduced and integrated by means of multi-objective decision-making methods. The introduced protection scheme contains several internal functions and coefficients which are subject to off-line pre-installation self-setting. Three unique procedures are delivered for self-adjusting the relay, and thus, making it self-organized. The results of testing show significant gains in both sensitivity and selectivity of the self-organized relay compared with traditional approaches.
66 citations
TL;DR: Based on the comprehensive analyses of the existing current differential protection criterion, a new type of adaptive restraint coefficient-based criterion is put forward in line with a variety of fault conditions in this paper.
Abstract: Based on the comprehensive analyses of the existing current differential protection criterion, a new type of adaptive restraint coefficient-based criterion is put forward in line with a variety of fault conditions. The restraint coefficient of this criterion can be adaptively adjusted according to the operation and fault conditions of the system. In this case, this criterion can guarantee the stability of the protection during external faults. Taking into account the increasing applications of current differential protection in the extremely high voltage or even ultra-high voltage transmission systems, the work performed in this paper is provided with better performance in the case of external faults and various high-resistance internal faults than the existing criterion. Hence, it is promising to apply the current differential protection for 750-kV and above transmission lines. Using Electromagnetic Transients Program software, a simulation model based on 750-kV transmission lines in the Northwest China power grid is established to validate the proposed scheme. All of the real data are provided by the utility of the Northwest China power grid and China Northwest Electric Power Design Institute. The simulation results show that the proposed scheme has satisfactory operation performance.
44 citations
TL;DR: The authors present a survey and a comparative analysis of various algorithms introduced for the differential protection of three-phase transformers and assesses how well they address the two subproblems of differential protection per se and exciting-current detection.
Abstract: The authors present a survey and a comparative analysis of various algorithms introduced for the differential protection of three-phase transformers. After a brief review of the concept, the problems associated with the differential protection of transformers, and the existing solutions as implemented with conventional (electromagnetic) relays, the algorithms introduced for digital relaying are outlined. Some of these algorithms are derived from conventional protection methods while others represent novel methods. They are analyzed in view of how well they address the two subproblems of differential protection per se and exciting-current detection. Finally, a simple ranking procedure is introduced. Two optimality performance indices, based on time and frequency, are defined and used as a basis for a comparison of the algorithm presented. >
44 citations
TL;DR: In this article, an attempt is made to put together developments in digital relays for protection of power transformer, which includes the most recent techniques, like artificial neural network (ANN) and fuzzy logic concepts, as well as other conventional methods used for transformer protection.
Abstract: In this article, an attempt is made to put together developments in digital relays for protection of power transformer. Efforts have been made to include all the techniques and philosophies used to that end. The article includes the most recent techniques, like artificial neural network (ANN) and fuzzy logic concepts, as well as other conventional methods used for transformer protection. Only a brief mention is made about conventional methods, while more emphasis is given on the application of ANN and fuzzy techniques for the protection of power transformer. This article presents a set of references of all concerned papers and provides a brief summary of the work presented in them. It also presents the results of these techniques as provided in the respective references.
39 citations
TL;DR: In this paper, a novel adaptive protection criterion is proposed, which can self-regulate the parameters of percentage differential characteristic (e.g., pickup current, restraint coefficient and restraint current at the knee point of the slope characteristic) on the basis of operating conditions of power transformers.
Abstract: Setting the pickup current and slope of differential relays of power transformer protection is a well-known compromise. It has been the focus of study to improve both the security and sensitivity of transformer differential protection recently. However, it is difficult to achieve a high degree of security and sensitivity at the same time by conventional percentage restraint differential criteria based on a fixed predetermined characteristic curve. Therefore a novel adaptive protection criterion is proposed in this study, which can self-regulate the parameters of percentage differential characteristic (e.g. pickup current, restraint coefficient and restraint current at the knee point of the slope characteristic) on the basis of operating conditions of power transformers. The test results show that the proposed scheme provides a high operating sensitivity on internal faults, while retaining higher security on all external faults. Furthermore, because of self-regulation of the setting values of relays, it is more convenient for engineers in the field who only need to give the upper and lower limits but not the exact value of the settings of protective relay.
32 citations
References
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TL;DR: In this article, the authors derived the performance equation of a high speed distance relay which is based upon the theory of symmetrical components, and a single equation was shown to be adequate for handling all types of faults which are likely to occur on a three-phase power system.
Abstract: The paper derives the performance equation of a high speed distance relay which is based upon the theory of symmetrical components. A single equation is shown to be adequate for handling all types of faults which are likely to occur on a three-phase power system. Errors created by system loading and fault-path resistance are considered. A numerical example illustrates the principle of operation of the relay. The relay is especially suited to a digital computer based protection system.
185 citations
TL;DR: In this article, a fundamental approach for detecting the direction to a power system fault within the first milliseconds following the fault inception is described, based on a combined evaluation of the voltage and current deviations generated by the fault occurrence.
Abstract: This paper describes a fundamental approach for detecting the direction to a power system fault within the first milliseconds following the fault inception. The method is based on a combined evaluation of the voltage and current deviations generated by the fault occurrence. Design considerations and test results based on numerical simulations and on a transient network analyser are presented. The method solves several problems occurring in conventional relaying and is suitable for use in ultra high speed protection systems which employ a fast telecommunication channel between the ends of the protected network
125 citations
TL;DR: In this article, an on-line digital computer technique is used for differential protection of a synchronous generator, which provides fault detection and tripping well within half a cycle and is also capable of discriminating between internal and external faults.
Abstract: This paper presents an on-line digital computer technique used for differential protection of a synchronous generator. It provides fault detection and tripping well within half a cycle and is also capable of discriminating between internal and external faults. In the latter case, sufficient restraint signals are generated to overcome maloperation. Further, the scheme is highly reliable even with CT saturation due to heavy through faults on the generating unit. On-line tests using a laboratory synchronous generator show the results for different types of internal and external faults with varying fault incidence inception.
27 citations