New Applications Requiring Solid State Protective Relay Characteristics

• Main Author: Zocholl, Stanley E.
• Format: Conference Proceeding
• Language: English
• Subjects: Circuit faults; Current transformers; Harmonic analysis; Relays; Voltage; Windings; Wires
• ISSN: 2576-702X; 2576-702X

Solid state relays now provide the full range of conventional protection characteristics. At the same time they provide design aspects which benefit the user but which may not be readily apparent. This paper covers a number of these aspects which lead to new appli cations. The first is the ability to construct time current characteristics free of overshoot and impulse response. The second is the ability to provide three phase relays using sequence networks. These are illustrated by applications in motor protection. The third is ability to tailor frequency characteristics. These characteristics are not well defined for conventional relays. However, both flat and selective frequency response possible in solid state relays are Illustrated with generator protection application. A fourth is the ability to provide high continuous current ratings without loss of sensitivity. Two applications for substation protection are given; a new harmonic restraint relay useful in pilot wire schemes and current detectors in breaker failure schemes. A fifth aspect useful in line protection are three phase direction relays with variable sector as well as variable characteristic angle. These relays used in conjunction with three phase torque controlled overcurrent relays provide flexible characteristics at reduced cost.