Advanced Residual Current Compensation System

Abstract

Minimizing the risk of wildfires caused by electrical failures in overhead lines has become an increasingly important topic due to global warming. Most electrical faults in distribution networks are single line to ground faults. If the energy impact at the fault location is minimized, the probability of ignition of dry vegetation can be significantly reduced. The fault current at single line to ground faults depends on the treatment of the neutral point. In ungrounded networks the fault current is determined by line to ground capacitance of the network. In compensated networks the main part of this capacitive current is compensated by an opposite directed inductive current, generated by a stepless adjustable coil between the neutral and ground. This coil is called a Ground Fault Neutralizer (GFN) [7], Arc Suppression Coil (ASC) or Petersen coil. In compensated networks only a small residual, mainly active current remains. This small fault current allows self-extinction of faults at overhead lines and continuation of power supply, if allowed by the grid code. The novel Advanced Residual Current Compensation (ARCC®) system together with a GFN can be used in such compensated networks to also rapidly compensate the remaining residual fault current and do so with high accuracy. The BoostPro® function additionally speeds up the residual current compensation. The ground fault itself can be detected with the admittance method, which works reliably also for high impedance ground faults. In case of changes of the network capacitance for example due to feeder switching operations, the GFN needs to be tuned quickly again, which is enabled by a new frequency adaptive trigger criterion.