Analysis of the Conducted Interfering Mechanism within SVC-based substations

Wide applications of large capacity FACTS (Flexible AC Transmission Systems) equipment within nowadays high voltage substations result in large amount of broadband electromagnetic emissions, which brings electromagnetic contamination to power grids and the environment, and even causes self-malfunction or unaccepted response of victim devices positioned nearby. The interfering mechanism needs to be clarified before sufficient applicable immunity measures can be taken. In this paper, a simulation model is established to investigate on the conducted mechanism in substations installed with SVC (Static Var Compensator) devices with a view to characterizing the main causes of the conducted interference. The high-frequency macro model for thyristors is established with a nonlinear time-varying resistor to simulate the switching characteristics of the thyristors. Based on the above macro model for thyristors, a concrete model of SVC including TSC (Thyristor-switched Capacitor) and TCR (Thyristor-controlled Reactor) is further proposed. In addition, high-frequency equivalent models for frequency-domain compensation of both CT and PT, based on their calibrated non-flat amplitude-frequency characteristics, are adopted to rectify the emissions levels from the SVC switching. The conducted interferences by simulations are correlated with that from on-site measurements, which indicates that the high-frequency switching characteristics of thyristors are the main causes of conducted emissions.