A Voltage Based Optimal Relay Coordination in Distributed Generation Penetrated Distribution Network Using Particle Swarm Optimization.

Abstract

The distribution system is the most visible part of the power supply chain. Most of the distribution lines are overhead in nature and thus have high chances of occurring different types of fault on the system. The distribution system (DS) has always some degree of unsafety. The proper protection in DS is one of the biggest challenges before the power engineer. Any type of fault that may occur on the DS should be cleared as soon as possible to prevent the supply outage for healthy part of the system. There are different types of safety equipment for own purposes in the distribution network. Each equipment has their assigned job. So depending upon the nature of fault, Location of fault and mode of operation of the distribution system, each equipment should operate in the right time at right condition. This becomes more complex when overcurrent based protection is used in DS having distributed generation of different topology, specifically the inverter based type. This thesis presents the use of particle swarm optimization (PSO) technique to achieve the objective of the development of effective protection coordination in distribution system using the fault voltage as a relay actuating quantity. DIgSILENT Power Factory tool and MATLAB platform are used for fault analysis and development of coordination program respectively. The developed program was tested for 6 node low voltage (LV) distribution network and 95 node medium voltage (MV) distribution network with injection of distributed generation at various nodes. In addition, the coordination between line primary relays and DG unit is analyzed and conclusion is drawn for the method that can be used for the better protection coordination between them. In the research the sum of operating time for LV distribution system is found to be only 2.99 seconds for islanded mode and 4.6 seconds for grid connected mode holding the coordination time interval of 0.2 second. Similarly for MV distribution system the sum of operating time of relays is found to be 3.4919 second for islanded mode and 4.1821 second for grid connected mode. However the same for other algorithm like Firefly Algorithm (FA) is found to be 3.7789 second for islanded mode and 4.763 second for grid connected mode. Hence from this result it has been found that the PSO algorithm provides the faster operating time of the primary relays for both 6 node LV and 95 node MV DS iv resulting lower value of the objective function than the other methods FA. The rate of convergence for proposed method is faster and smooth than FA method. Hence the developed protection coordination algorithm of voltage based relay with PSO is found to be practically, the more efficient, sensitive and discriminative method for relay coordination in both low and medium voltage of distribution system. The proposed voltage based method is compared with the current based method for the Canadian Distribution Network with all the technical data same for both method. The sum of operating time of primary relays for voltage based method is found to be 7.363 seconds whereas the same for over current based method is 11. 239 seconds. Therefore, it has been found that the voltage based protection system is faster than current based protection system in distribution system with distributed generations.