Resource-saving current protections for electrical installations with isolated phase busducts

Abstract

Protections are suggested on the basis of a current relay with two capacitors and a reed switch, which is mounted at a safe distance from a busbar inside the busduct enclosure. The relay does not need in current transformers thus saving copper, steel, and insulating materials. It differs from reed switch based analogs in the noise immunity due to signaling after two actuations of the reed switch; non-operation in the case of sealing (due to the control of duration of breaker contact); the presence of a reed switch fastening structure, and built-in test diagnostics by mean of current supply into the reed switch winding. A technique for selecting protection parameters and assessing their sensitivity is presented. The inductions of magnetic fields which affect the reed switch are calculated with the use of the simplest formulas for the shielding coefficient and of the Bio–Savart–Laplace law, where experimentally derived correcting coefficients are introduced. Examples of the calculation of the induction of protection operation and of reed switch selection are presented along with an oscillogram which confirms the cutoff operability and speed.

Keywords

• Reed switch protection
• Busduct enclosure
• Current
• Noise
• Experiment
• Magnetic field induction