Current Measuring Converters Protection Against Single-Phase Earth Fault

The article is devoted to the development and analysis of current measuring converters (ZSCT) used to protect lines of two cables from single-phase earth fault in networks with an isolated neutral conductor. Two types of ZSCT designs are considered: with a counter- series connection of the secondary windings and with a common winding for two cores. It is shown that using a common housing for two cores with a winding makes it possible to reduce the cost of manufacturing the converter compared with two separate ZSCT. The principles of operation of such converters are described, based on the equality of currents in parallel cables of the line and compensation of magnetic fluxes in the cores, which ensures zero resultant EMF in normal network operation. The design of a detachable double ZSCT is proposed, which can be installed on lines already in operation, which increases the convenience of installation and operation. The possibility of replacing traditional electromagnetic relays with reed switches has also been considered, which reduces the cost of protection against SPEF. It is shown that the sensitivity of the protection can be increased due to the magnetization of the reed switch winding. The results of the work can be used to design and modernize protection systems in cable networks, improving their reliability, efficiency and ease of operation.