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.

A self-organizing fuzzy logic based protective relay-an application to power transformer protection

Recent progress in monolithic waveguide-photodetector integration on III-V semiconductors for applications in the 0.8-1.6- mu m wavelength range is reviewed. Critical issues for device performance and fabrication are discussed, followed by a description of the underlying optical coupling mechanisms. Tradeoffs between performance and integrability are assessed in detail for vertical and butt coupling and their variants. It is shown how appropriately chosen integration techniques have led to a variety of monolithic devices for advanced lightwave receivers. >

Monolithic integration of optical waveguide circuitry with III-V photodetectors for advanced lightwave receivers

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.

An Adaptive Operating Characteristic to Improve the Operation Stability of Percentage Differential Protection

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. >

A comparative analysis of digital relaying algorithms for the differential protection of three phase transformers

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.

Advances in Transformer Protection: A Review

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.

A New Techniques of Differential Relaying the Differential Relay

Measurements were made of the noise suppression and signal enhancement properties of dual In/sub 0.53/Ga/sub 0.47/As-InP metal-semiconductor-metal (MSM) photodiodes integrated with a leaky mode In/sub 0.52/Al/sub 0.48/As waveguide directional coupler, and an electro-optic phase shifter. The experiments were done with a 1.3- mu m laser as the local oscillator. A noise suppression of 11 dB and signal enhancement of 1.3 dB were recorded for the MSM photodiodes. >

Noise suppression characteristics of InP-based monolithically integrated guided wave balanced photodiodes

An iterative procedure for obtaining two-carrier dc solutions in regions of rapidly varying carrier concentration is presented The procedure uses an analytic solution for the carrier concentrations in a region of linear spatial electric field variation Field-dependent diffusion and field-dependent velocities are assumed A single-carrier small-signal model for a drift region with a spatially varying field and field-dependent transport properties is presented When applied to a BARITT device, results consistent with published experimental data are obtained The importance of momentum relaxation effects in Si BARITT drift regions is discussed

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Analytic modeling of transit-time device drift regions with field-dependent transport coefficients

This paper develops state models for estimating the optimum performance of analog and computer impedance relays in the presence of noise due to non-fundamental frequency components. An Extended Kalman filter is used to determine the optimum estimates and error covariance of impedance magnitude and phase angle. lt is shown that impedance relays have performance limits dependent upon the amount of noise present. The effects of sampling rate of input signals, data-window used for fault detection, and cut-off frequency of anti-aliasing filter on the performance of a computer relay are also investigated. Digital computer simulation results for both analog and computer impedance relays are presented.

Simulation Methods for Optimum Performance Estimation of Analog and Computer Impedance Relays

This paper describes a coherent detection receiver (CDR) with adaptive image rejection capability which is also compatible with existing monolithic integrated optics and MMIC technology. It details the component selection and circuit layout tradeoffs that were considered for the design and fabrication of the CDR in monolithic IC format. An optical `half receiver' IC with waveguides, phase shifter, 3 dB coupler, and balanced mixer diodes has been constructed and tested. Measurements and results for this chip are given and discussed. An initial design and simulated results for the microwave (intermediate frequency) IC are also given and discussed.

Patrick J. McCleer

Papers

A New Techniques of Differential Relaying the Differential Relay

Noise suppression characteristics of InP-based monolithically integrated guided wave balanced photodiodes

Analytic modeling of transit-time device drift regions with field-dependent transport coefficients

Simulation Methods for Optimum Performance Estimation of Analog and Computer Impedance Relays

Integration of a coherent optical receiver with adaptive image rejection capability