ELECTROMAGNETIC COMPATIBILITY OF CONTROL AND MEASURING CABLES IN NON-STATIONARY MODES

Abstract

The article deals with questions of researching and analysis of voltages induced in protective shields of three-phase shielded conductor in modes of asymmetric short circuits external to generators of power station. The development of recommendations and measures to ensure electromagnetic compatibility of measuring circuits of microprocessor devices is an urgent research task, since it is generally determined by the electrophysical properties of the interference source and the analog-digital element base of the measuring part of the devices. The scientific novelty of the work consists in the development of measures to eliminate the induced electromagnetic influence on control and measuring cables switched to current and voltage measuring transformers. The purpose of the study is to assess the electromagnetic effect of the industrial frequency field on control and measuring cables laid near a phase-shielded current pipeline, as well as to develop measures to ensure their electromagnetic compatibility. The paper presents a method for calculating the distribution of the intensity modulus H of a magnetic field induced by an industrial frequency current from a generator at an electric power station. For the modes of single-phase, two-phase and two-phase short circuits to the ground, patterns of the distribution of the magnetic field intensity modulus H are constructed, a stiffness class is assigned according to the magnetic field effect on control and measuring cables in accordance with the classification. Recommendations to reduce the level of exposure to the magnetic field intensity H are given. In case of using the screen, a repeated calculation was performed to compare and determine the effectiveness of this event. As a result of numerical experiments, the effectiveness of the use of an additional screen as one of the measures to ensure electromagnetic compatibility is justified. The use of an additional steel shield makes it possible to reduce the magnetic field strength on the surface of control and measuring cables to acceptable values and, as a result, ensure reliable operation of microprocessor control, protection and automation devices.