Reed Switch and Magneto Resistor-Based Differential Protection Featuring Test Diagnostics for Converters

This paper states that constructing relay protections without current transformers is a relevant undertaking. To address this, the paper proposes using reed switches. Notably, the principles and some protection devices based on reed switches have already been developed, including differential protection of reed switch and magneto resistor-based converters; these solutions use the majority principle and functional diagnostics blocks. It should be emphasized that such protections lack test diagnostics, which means it cannot timely detect damaged majority elements or output relays, resulting in false positives or failure to trigger protections. This paper proposes a circuit for test diagnostics that, unlike other known designs, has three to six interconnected control windings on magneto resistors as well as button switches. The authors hereof discuss how protections act in a variety of converter operations as well as how to detect faults in three redundant protection kits, the majority element, or the output relay. To mount magneto resistors near the busbars of closed DC conductors, this paper proposes a simple and convenient mount that contains an L-shaped plate and angled fixtures. The paper further defines the applications of such protection.