Due to advancements in the field of electronics, relay designers are able to implement practical microprocessor-based relay designs which are being used more and more by utilities. With the increasing number of digital overcurrent relays being developed for use in electrical power systems need has arisen for the development of directional relays. In many situations, the magnitudes of fault currents do not provide enough information for correctly discriminating faults in a power system where the lines form loops, rings or grids. As power systems have become increasingly complex and interconnected, this scenario occurs more often. Directional relays can sense the direction of power flow and often act as sensors and logical switches for activating other types of relays. An example of this type of monitoring is the directional overcurrent relay. This thesis is concerned with the design and implementation of a versatile microprocessor-based directional overcurrent relay for phase and ground fault detection. The user is able to specify various design parameters at the time of commissioning the relay so that it may be used in distribution networks, transmission networks or other power flow applications. Some of these parameters are the maximum torque angles, torque offsets, directional sensing voltage-current pairs, pickup settings, time multiplier settings, current-time characteristics and configuration of the relay. The relay design is implemented on an Ariel Corporation's PC-C25 DSP Coprocessor Board which contains a Texas Instruments TMS320C25 digital signal processor.

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A Study of Directional Element Connections for Phase Relays

The design and implementation of a versatile microprocessor-based directional overcurrent relay

Over current relays are usually used for protecting the power system to alleviate the pressure on electrical equipment. This paper presents a proposed optimal method for coordinating the Over current relays based on genetic algorithm. The objective is minimizing the operating current of relays subjected to relay characteristic curves, the limits of the relay settings and coordination constraints. The impact of the proposed optimization technique is tested on IEEE-33 distribution system. The results are compared with those obtained by applying the commonly used method that uses the time setting of the relay as an objective function.

Optimal Relay Setting for Utilitydistribution Feeders

DOCR can be used to efficiently increase the reliability and to protect the bi-directional D/L(Distribution Lines). As more DG(Distributed Generation)s attempt to connect the bi-directional D/L, there is an increasing need for studies of how to use DOCR installed in the D/L. This paper investigates the operating principles of DOCR and presents the results an effect of sequence and fault impedance in L-L(Line to Line) fault. An advanced DOCR operating algorithm is proposed to reduce the mal-operation of conventional DOCR. The proposed algorithm is applied to the bi-directional power flow system and shows that it decreases the mal-operation of DOCR through the computer simulation.

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A Study of Directional Element Connections for Phase Relays

Citations

The design and implementation of a versatile microprocessor-based directional overcurrent relay

Optimal Relay Setting for Utilitydistribution Feeders

A New Algorithm to Reduce the Mal-Operation of DOCR in Bi-directional Power Distribution Systems

An Analysis of Polyphase Directional Relay Torques [includes discussion]

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