A Method for Calculating Capacitive Currents, with a Single-Phase Earth Fault, Using the Parameters of Emergency and Pre-Emergency Modes

Single-phase earth faults are the most common problem in networks with isolated neutral. The development and improvement of the hardware of modern microprocessor relay protection devices and measuring transformers make it possible to implement new and more advanced algorithms. The concept of development of the electric power industry - “digital transformation-2030”, developed by Rosseti, involves the introduction of communication channels, including on lines 6-35kV. In addition, optoelectronic measuring transformers with high measurement accuracy are being actively developed and put into operation [1]. This makes it possible to implement two-way relay protection and automation algorithms on 6-35kV lines and, above all, the function of determining the location of damage (FL). To organize the operation of such relay protection and automation algorithms designed to eliminate single-phase earth faults in networks with an isolated neutral, it is necessary to calculate the capacitive currents flowing in intact phases relative to the ground and in phase-to-phase capacitances. The article describes in detail the method developed by the authors for calculating capacitive currents in single-phase earth faults using the parameters of emergency and pre-emergency modes.