M.S. Sachdev

A fault locator for radial subtransmission and distribution lines

This paper presents the design and development of a prototype fault locator that estimates the location of shunt faults on radial subtransmission and distribution lines. The fault location technique is based on the fundamental frequency component of voltages and currents measured at the line terminal. Extensive sensitivity studies of the fault location technique have been done-some of the results are included in the paper. Hardware and software of the fault locator are described. The fault locator was tested in the laboratory using simulated fault data and a real-time playback simulator. Some results from the tests are presented. Results indicate that the fault location technique has acceptable accuracy, is robust and can be implemented with the available technology.

Software models for relays

This paper reviews the past and present uses of relay models. It discusses the various types of models, what information is required to build such models and the model validation process. Examples of present and possible future use of software models are given.

A graphical electromagnetic simulation laboratory for power systems engineering programs

The recent availability of Electromagnetic Transient Programs with graphical front ends now makes it possible to put together models for circuits and systems in a manner similar to the connection of components in a laboratory, In the past, the nongraphical EMT Programs required considerable expertise in their use and thus distracted the students into the details of simulation. The introduction of a graphical simulation based laboratory into undergraduate and graduate power engineering education programs is presented, based on the PSCAD/EMTDC program. The philosophy behind the design of suitable example cases is presented within the framework of an Undergraduate Power Electronics Course, an HVDC Transmission Course and a course on Power System Protection.

Protection issues during system restoration

Power system blackouts are a very rare phenomenon in a well-planned interconnected power system. Nevertheless it is very important to have plans and systems in place to handle any eventuality even if it is remote. This report brings out various issues related to protection during a system restoration process. Power system protection is critical to a safe, efficient, and reliable power system. Protection engineers take every possible care to ensure that protection systems are designed considering all predictable eventualities and these constraints have grown over time. However, during system restoration, after a major blackout, it is possible for the protection elements to be presented with situations, which they can mistake for an unhealthy power system and the protection elements may operate. The prime concern during a power system blackout is to bring the system back to normalcy as fast as possible. At times, if proper care is not taken, the protection system can hinder and delay the restoration of the power system. This report discusses various such conditions that can occur during the blackstart of a power system and also suggests solutions to manage them without compromising the objectives of protection system i.e., to ensure a safe, efficient, and reliable power system.

A technique for estimating locations of shunt faults on distribution lines

Accurate estimation of the locations of line faults has been a subject of interest to electric power utility engineers and researchers for over twenty-five years. Almost all the research done so far has been aimed at finding the locations of transmission line faults. Lately, the location of faults on distribution lines has started receiving some attention because of public pressure on the utilities for improving the reliability of power supply. This paper presents the overview of a technique that estimates the location of a distribution line shunt fault. Some test results are also reported.

Issues and opportunities for testing numerical relays

This paper reviews the use of modern relay test sets, real-time playback simulators and real-time digital simulators for testing numerical relays. The issues concerning the generation of data for testing relays are examined. Types of tests that can be performed on numerical relays are also reviewed. A procedure for identifying critical tests is discussed. A procedure for testing relays by using recorded data is also described. The paper demonstrates that there is a need for the relay manufacturers to provide facilities in their relays for testing them by using the data acquired by numerical devices installed in the system.

An improved voltage phasor estimation technique to minimize the impact of CCVT transients in distance protection

This paper describes the impact of the transient response of coupling capacitor voltage transformers (CCVTs) on the performance of distance relays. Several factors that affect the frequency and time responses of CCVTs are considered. The effect of the transient response on phasor estimation is illustrated. A new least squares phasor estimation technique, which uses the knowledge of the frequency of the CCVT transients, is presented. A sample case, taken from a set of studies, is included to demonstrate the performance of the proposed approach

Modeling relays for use in power system protection studies

This paper presents a new approach for modeling numerical relays. The models are embedded in the code of the electromagnetic transient program PSCAD/EMTDC. The software for modeling distance and differential relays (PLSA) is described in the paper. The inclusion of the models in PSCAD/EMTDC and their use in power system protection studies are addressed as well

Artificial neural network applications for power system protection

The most commonly used systems for protecting transmission and subtransmission lines belong to the family of distance relays. Over the past eighty years, successful designs based on electromechanical, solid-state and digital electronics technologies have been produced and marketed. These relays implement various characteristics, such as impedance, offset-impedance, admittance, reactance and blinders. The artificial neural network based designs of distance relays proposed so far work well for ideal fault conditions but are not able to maintain the integrity of the boundaries of the relay characteristics of generic designs. This paper reviews ANN models that have been proposed in the past for protecting components of power systems and presents a methodology that fully exploits the potential of ANNs in designing generic distance relays that retain the integrity of the boundaries of their characteristics

A fast distance relay using adaptive data window filters

This paper describes the design of a distance relay that, uses adaptive data window filters to provide high speed tripping. The relay uses a fault detector to detect the inception of a fault. Starting from the fault detection, the data window size is progressively increased as new fault samples become available until the window size becomes one cycle of the fundamental frequency. At each instant, a suitable filter is used for estimating voltage and current phasors. This procedure improves the transient response of the relay and allows faster convergence of the impedance estimates and, therefore, reduces the trip time. The proposed relay was tested by using fault simulations on a sample power system. Results indicate that the proposed relay design reduces the trip times.