Recloser

A recloser, also called an autorecloser or automatic circuit recloser, is switchgear used on overhead electricity distribution networks to detect and interrupt transient faults. It is essentially a rated circuit breaker fitted with integrated current and voltage sensors and a protection relay, purpose-built as a protection asset and governed by IEC and IEEE standards, with four major voltage classes of 15.5, 27, 38 and 72 kilovolts. Most faults on overhead distribution networks, an estimated 80 to 87 percent, are transient, caused by lightning, a voltage surge or a foreign object briefly touching an exposed line, and the resulting arc ionizes the surrounding air enough to sustain itself even after the original cause is gone; such faults can be cleared simply by reclosing the circuit once the ionization dissipates, a minimum of three tenths of a second. Reclosers are built for a rapid open-close duty cycle, allowing engineers to configure up to four reclose attempts before the device locks out, and a rapid trip curve can interrupt a fault current in as little as 1.5 cycles.