Nonconformance in electromechanical output relays of microprocessor-based protection devices under actual operating conditions

Abstract

Microprocessor-based protection relays are gradually driving out traditional electromechanical and even electronic protection devices from virtually all fields of power and electrical engineering. In this paper, one of many problems of microprocessor-based relays is discussed: nonconformance of miniature electromechanical output relays under actual operation conditions: switching inductive loads (with tripping CB coils or lockout relay coils) at 220 VDC, and "dry" switching of some control circuits. We suggest a simple and very reliable solution to this problem: an electronic amplifier for increase in switching ability of the output relays.