Detection and isolation of faulty line in an active distribution network using intelligent numerical relay

Abstract

• The Intelligent Numerical Relay (INR) placed at substation majorly performs three functions, i.e., Over Current Relay (OCR), Distribution System State Estimator (DSSER) and Faulty Line Locator (FLL) to identify exact faulty line. • In OCR operation, it collects all possible supply current data from substation CT as well as PMUs at DG buses. it compares the total supply current with pickup value and identify the fault as well as faulty phase. • In DSSER operation, it collects data from optimal PMUs and estimates the states of entire system using linear Weighted Least Square (WLS) algorithm. • In FLL operation, it observes the voltage magnitudes at each bus based on estimated voltages. FLL identifies the exact faulty line which is in between maximum change in voltage bus and second maximum change in voltage bus. • After identification of faulty line, the INR remotely operates the intelligent switchgear of faulty line to isolate it. This method could detect the exact faulty line almost instantaneously, i.e., before the fuse melts. • The proposed technique is tested and validated for IEEE 33 bus active distribution network under different types of faults at various locations. In recent days Passive distribution networks are being transformed to Active Distribution Networks. The operation of Active Distribution Networks is becoming more complex with increasing energy demand and integration of distributed generations. Currently, identifying a faulty line in the distribution system is a tedious task which causes long interruptions to the consumers. Therefore, a real-time system is mandatory to monitor and control distribution network. This paper presents a novel method to detect the exact faulty line in Active Distribution Networks using an Intelligent Numerical Relay. The Intelligent Numerical Relay placed at substation collects the data from optimally placed Phasor Measurement Units and performs several functions. It operates as Over Current Relay to identify the fault, acts as Distribution System State Estimator to estimate the state of the system, and also acts as Faulty Line Locator to identify the faulty line. This Intelligent Numerical Relay placed at substation acquires all-possible supply currents data from substation current transformers as well as Phasor Measurement Units at Distributed Generator buses. In its Over Current Relay operation, it detects the fault by comparing total supply current with pick up value. The faulty line detection is performed by Faulty Line Locator using estimated voltages from Distribution System State Estimator based on optimal Phasor Measurement Units data. Faulty Line Locator observes the estimated voltages at each bus, it identifies the exact faulty line which is in between the buses with maximum change in voltage and second maximum change in voltage. After the identification of faulty line, the Intelligent Numerical Relay remotely operates the intelligent switchgear present at the faulty line to isolate it. The main advantage of this method is that, it could detect the exact faulty line almost instantaneously, i.e., before the fuse blows. IEEE 33 bus active distribution system is considered for testing and validation of the proposed method.