A new loss-of-excitation protection based on fuzzy set theory has been presented. It makes use of conventional concepts of loss-of-excitation protection in synchronous generators (i.e., the behavior of internal voltage and apparent impedance trajectory). Instead of crisp values, a fuzzy inference mechanism is applied. To show the effectiveness of the proposed technique, comparisons are made with traditional protection methods by considering different generators sizes. The protection scheme proposed displays a secure and effective high-speed loss-of-excitation detection during power swings. Furthermore, the performance of the proposed method was not affected by generator parameters.

An Innovative Loss-of-Excitation Protection Based on the Fuzzy Inference Mechanism

The loss-of-excitation (LOE) event threatens the generator and power system stability. Several methods have been proposed for LOE detection, most of which are based on the impedance trajectory. These approaches may not be able to distinguish between LOE and the stable generator swing (SGS). Thus, allocating an operation time delay is usually used to overcome the LOE relay misoperation due to SGS. This paper presents a new approach for the LOE relay. The proposed strategy exploits a combined scheme based on the derivative of the terminal voltage and the output reactive power of the generator. Comprehensive simulation studies are accomplished for various generator conditions and system disturbances to determine the relay setting and to evaluate its performance. The performed studies demonstrate that the proposed strategy enhances security and operation time of the LOE relay, compared with some existing methods.

A Novel Approach to Detect the Synchronous Generator Loss of Excitation

Conventional loss-of-excitation relay for a turbo alternator is an offset mho relay and has been reported to maloperate on stable power swings under certain conditions. The documented solution to this problem is to intentionally delay the operation of LOE relay, which the authors believe is not an ideal solution. This paper, basically, reports an adaptive or dynamic LOE relay, augmented by suitably selected time-derivatives of impedance seen by the relay, to ensure correct discrimination between genuine loss of excitation and power swing.

A new adaptive loss of excitation relay augmented by rate of change of reactance

SUMMARY

This contribution deals with the analysis of synchronous generator loss of excitation (LOE) protection. This paper presents a new method for detecting LOE in synchronous generator based on the variation of the magnetic flux linkage in the air gap. To show the effectiveness of the proposed protection, comparisons are made with the conventional LOE protection methods by considering different generator sizes. The simulation results show that the proposed method is useful and effective to detect LOE conditions. The main advantage of this method is its speed and sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.

Study on application of flux linkage of synchronous generator for loss of excitation detection

Loss of excitation (LOE) event threatens both the generator and power system stability. Numerous approaches have been proposed for LOE detection, most of which use the impedance trajectory. Such methods may maloperate under system disturbances, especially power swings. This study presents a new approach for LOE detection by estimating the field flux linkage participation (FFLP) in the stator flux linkage. Intrinsically, this newly defined index mainly depends on the generator excitation system and thus highly reduces when an LOE takes place. The FFLP parameter can easily be calculated using stator voltage and current signals. All kinds of LOE events cannot be studied using most available simulation software. To cover all of them, utilising state variables, a generator model connected to a power system is implemented. Performed simulation studies demonstrate that the proposed strategy not only considerably decreases the LOE relay operation time, but also improves the LOE relay security against system disturbances. In addition, the proposed approach is experimentally evaluated on a 10 kVA synchronous generator.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-gtd.2016.1009

Flux linkage estimation based loss of excitation relay for synchronous generator

The IEEE Working Group on Generator Protection with Digital Computers surveyed power industry engineers to determine what problems are generally encountered and for which adequate protective devices are not available. Two surveys were conducted: one to identify the problems; and the other to determine how prevalent they are. The industry responses are briefly reported, the problems identified are described, and the feasibility of using digital processors to alleviate them is examined. >

J.R. Latham

Papers

Survey of experience with generator protection and prospects for improvements using digital computers