Protection of Hexagon Connections Using Reed Switches and Microprocessors with Majority Scheme and Functional Diagnostics

The necessity to improve the reliability of relay protection for connections at open switchgear with voltages of 110–750 kV is substantiated. It is shown that to achieve this, it is advisable to use the majority method, duplicating current transformers with reed switches. The properties of reed switches are described, and their advantages are highlighted in comparison with the use of other magnetic-sensitive elements. For connections of open switchgear configured in a hexagon scheme, a general backup protection is proposed, with one of the sets based on the principle of comparing the power sign on a microprocessor and current transformers, and the other two based on the use of Kirchhoff's law, a microprocessor, and reed switches, but without current transformers. The protection scheme is provided, and its behavior in various operating modes is examined. It is shown that such protection will be much more reliable and economical than previously proposed solutions.