DETECTION AND REMEDIATION OF CRITICAL NODES AND BRANCHES IN AN INTERCONNECTED POWER SYSTEM NETWORK

Abstract

ABSTRACT Voltage instability has been a major concern to power supply utilities and its effect has resulted into system voltage collapse and high power losses. This study employed the fast voltage stability index technique (FVSI) to detect critical nodes and branches in an interconnected power system network, considering the IEEE 57-node and Nigeria 34-node electricity grids as case studies.The detected critical branches were corrected using static var compensator (SVC). Load flow modelling and simulation were carried out to determine the node voltage, phase angle and active power loss along the network lines. Simulations were done for the base case and the contingency-variation of the reactive loads in the network until the FVSI value approaches one (1) to determine the maximum permissible load of each load nodes. The ranking in the system was done by sorting the maximum permissible load, of the load nodes in ascending order. The smallest maximum permissible load was ranked highest implying that the node is the weakest in the system. Thereafter, the node voltage magnitudes and branch active power losses were computed and compared for the two case networks. The results revealed that, for IEEE 57-node power system, 43 node voltages out of 57 node voltages were outside the statutory limit of ± 5%. The total active power loss was 65.303 MW. The inclusion of SVC in the system corrected the voltage limit violations on the critical nodes while the total active power loss was reduced by 43.29% amount to 37.039 MW. In the case of Nigeria’s 34-node power network, voltage limit violations occurred at two nodes which were node 2 (BirninKebbi) and node 13 (Kano T.S). The voltages at the two buses were outside the acceptable limit of ± 5%. The total active power loss was 134.920 MW. The SVC introduction into the system normalized the voltages on the critical nodes with the total active power loss reduced by 52.95% amount iv to 63.481 MW. These results were indications that FVSI when appropriately applied can aid the detection of critical nodes and branches in power system network while the SVC installation can minimize the power loss and improve the voltage magnitude of the system. This study established the suitability of fast voltage stability index technique for the weak nodes and branches detection in a power system and static var compensator (SVC) for possible remedial action.