D.R. Sevcik

Experimental evaluation of EMTP-based current transformer models for protective relay transient study

This paper describes an EPRI study of current transformer (CT) digital models intended for protective relay transient performance analysis. Experimental evaluation of CT models implemented using the Electromagnetic Transient Program (EMTP) was carried out. Two relaying CTs with 600/5 and 2000/5 ratios were used in the study. Experiments in a high power laboratory were performed to obtain transient responses. Simulation of the CT response to the same transient events was set up using three different CT models. They were implemented based on the saturable transformer and nonlinear reactor models available in an EMTP. Comparison of laboratory and simulation results indicates that CT models developed based on the EMTP program give satisfactory results for most of the cases. It has also been discovered that in some instances EMTP models need further improvements. >

Digital models of coupling capacitor voltage transformers for protective relay transient studies

The authors describe the development by EPRI of digital coupling capacitor voltage transformer (CCVT) models that are intended for digital simulation of fault transients. Experimental techniques for laboratory measurements of the CCVT parameters are outlined. A sensitivity study was performed to identify the influence of various CCVT parameters on the transient behavior relevant for the relaying studies. Digital models of three different CCVTs are given and their transient behavior is compared to the behavior of the actual transformers. >

An expert system for transmission substation event analysis

Digital fault recorders (DFRs) are used in substations to capture recordings of various disturbances and fault events. Protection engineers use these recordings to identify reasons for particular operation of protection relays and circuit breakers. In performing this task protection engineers use their expertise related to specific power system conditions, equipment and operations. This paper describes implementation of an expert system which performs fault detection and diagnosis automatically and can aid operators in their task of analyzing disturbances and fault events. >

DYNA-TEST simulator for relay testing. I. Design characteristics

The authors describe a new digital dynamic testing (DYNA-TEST) simulator developed for protection relay applications. This simulator is capable of producing voltage and current transients that correspond to actual fault events in the power systems. Fault transients are generated either by simulating power system faults using an electromagnetic transient program or by replaying records of fault signals captured in substations by digital fault recorders. These signals are used to test protection relays. Such an approach to relay testing represents a major improvement over steady-state testing. >

Distance Relay Application Testing Using a Digital Simulator

This paper reports on power transmission distance relay application testing using simulated transient waveforms. Power system modeling and test procedures using modern digital simulators are presented. An extensive study of five commercial relays, comparing their application for a 345 kV transmission line, is carried out by performing thousands of one-terminal and synchronized two-terminal transient tests. The digital simulation approach has proved to be an efficient technique. This paper presents a methodology for evaluating distance relay transient performance based on extensive laboratory testing. Important issues regarding application testing are also addressed and investigated in this paper.

Expert system reasoning streamlines disturbance analysis

Houston Lighting & Power funded Texas A&M to develop an expert system based automatic disturbance analysis system that would satisfy the following requirements: PC-based system for substation application; direct interface to the existing digital fault recorder (DFR) system; graphical user interface (GUI) for viewing of results; database management for storing results; and a modem interface to the protection engineer. The system was developed and extensively tested using Electromagnetic Transient Program (EMTP) simulations and actual disturbance records captured by DFRs at various substations. Since then, the system has been connected to a substation DFR for online monitoring of disturbances. This article points out some design and implementation issues and highlights performance validation and operating experience related to the expert system.<<ETX>>

Automated circuit breaker monitoring and analysis

The automated circuit breaker diagnostic system described in this paper is an extension of the widely used portable circuit breaker testing device concept. The testing devices can be connected to the circuit breakers control circuit to record analog and digital signals. The automated system consists of a signal processing module and an expert system module. The two modules process the voltage and current signals recorded by the testing device, diagnose and report any abnormalities that are discovered. The paper describes the system requirements, the implementation of the two system modules, and provides an example that demonstrates the entire process. Real data recorded in a substation has been used to test the system.

An advanced method for testing of distance relay operating characteristic

This paper describes a test method for distance relays using an advanced open-loop digital simulator. Derivation of test signals during prefault and fault, and test procedure are introduced. It is demonstrated that the method of generating test signals and the procedure of applying them to a relay under test directly affect test results. Prefault voltage and current are also a very important factor. The decaying DC offset is considered as well. Test results for five different relays using this new method are presented in this paper. The results demonstrate practical benefits of the test method.

DYNA-TEST simulator for relay testing. II. Performance evaluation

For pt.I see ibid., vol.6, no.4, p.1427 (1991). Evaluation steps undertaken in the analysis of the DYNA-TEST simulator performance are described. The evaluation assumes comparison of the simulator output waveforms obtained using simulated data with the reference waveforms obtained through recording of an actual fault event. Tests are done using specific utility data. Particular attention is given to the system and instrument transformer modeling as well as to the D/A (digital-to-analog) conversion signal reconstruction subsystem characteristics. Particular reference is made to the Houston Lighting and Power (HL&P) system modeling approach. >

A novel method for transmission network fault location using genetic algorithms and sparse field recordings

The paper presents an approach to locate a fault in a transmission network based on waveform matching. Matching during-fault recorded phasor with the during fault simulated phasor is used to determine the fault location. The search process to find the best waveform match is actually an optimization problem. The genetic algorithm (GA) is introduced to find the optimal solution. The proposed approach is suitable for the situations where only the data recorded sparsely is available. Under such circumstances, it can offer more accurate results than other known techniques.