Overcoming asymmetrical communication delays in line current differential protection circuits

Dortmans, Justin (2016) Overcoming asymmetrical communication delays in line current differential protection circuits. [USQ Project]

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Abstract

Communications asymmetry leads to current differential protection relay misoperation by causing relays at either end of a power line to sample load current waveforms at different moments in time. The increased use of current differential protection and developments in communication technologies in power systems has led to the increase likelihood of relay misoperation due to communication delay asymmetry.

The main cause of communication delay asymmetry is split-path-communications, whereby transmit and receive directions of a communications channel take separate paths with different delays. Split-path-communications are the result of faults in one direction of a communications channel, causing that direction only to switch from main to alternate paths.

This project studies AusNet Services’ communications network and those similar to it, to find the typical sources of communication delays. Delays are measured between a variety E1 interfaces in the AusNet Services network, and the results used to calculate the per unit delays through given types of cross-connections. These are used in conjunction with a current differential relay response calculator, to create a model that displays a relay’s response to a communications channel with specified attributes.

The chance of split-path-communications can be avoided by using communications equipment with bidirectional switching capabilities. The Avara DB4 family of branching E1 cards have this capability; however, this project reveals that a fault in the DB4 firmware code means that they may still cause protection relays to misoperate due to asymmetry. The DB4 firmware was updated, and further testing proved that it now prevented relay misoperation.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) Major Electrical & Electronic Engineering project
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Supervisors: Das, Narottam
Date Deposited: 20 Jul 2017 02:41
Last Modified: 20 Jul 2017 02:41
Uncontrolled Keywords: split-path-communications; asymmetrical communication; differential protection circuits
Fields of Research : 09 Engineering > 0906 Electrical and Electronic Engineering > 090601 Circuits and Systems
URI: http://eprints.usq.edu.au/id/eprint/31396

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