Main Article Content
This case study presents the working, testing and commissioning of the 220 kV backup distance protection schemes employed on the Pipri West Grid of Karachi Electric Limited (KEL). The paper discusses protection systems in transmission lines and the technical issues with electromechanical and static relays. Current status of relays in Pakistani transmission network and the need for their up gradation to modern numerical relays have been emphasized. The 220 kV backup distance project of Karachi Electric (KE) uses LZ96 static relay that has been replaced with Siemens Siprotec 4 7SA522 numeric distance relay. These newly replaced relays has features of telecommunication, monitoring, control, and power swing blocking functions. This paper also present the problems encountered in conventional distance protection. Desirable features of distance protection are obtained via tele-protection. Information transmitted from one end to the other end of the line via tele-protection is also analyzed. The parameterizing of numerical relays is done with Digitalizer Simulator (DIGSI) software and finally testing results are reported using Instrumentation System Automation (ISA) TEST SET.
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