Recloser

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In electric power distribution, a recloser, also known as autorecloser or automatic circuit recloser (ACR), is a switchgear designed for use on overhead electricity distribution networks to detect and interrupt transient faults. Reclosers are essentially rated circuit breakers with integrated current and voltage sensors and a protection relay, optimized for use as a protection asset. Reclosers are governed by the IEC 62271-111/IEEE Std C37.60 and IEC 62271-200 standards. The four major classes of operating maximum voltage are 15.5 kV, 27 kV, 38 kV and 72 kV. For overhead electric power distribution networks, up to 80-87% of faults are transient. Transient faults can occur due to various causes, such as lightning strikes, voltage surges, or foreign objects coming into contact with exposed distribution lines. When a transient fault occurs, the resulting arc will ionize the air. The ionized air will maintain the arc even after the material that caused the short circuit is removed. Consequently, these transient faults can be resolved by a simple reclose operation. The minimum reclose time allowed for any operation is .3 seconds. This is the minimum amount of time required for the ionization to dissipate from the arc path. Reclosers are designed to handle a rapid open-close duty cycle, where electrical engineers can optionally configure the number and timing of attempted close operations prior to transitioning to a lockout stage. The number of reclose attempts is limited to a maximum of four by recloser standards noted above. At two multiples of the rated current, the recloser's rapid trip curve can cause a trip (off circuit) in as little as 1.5 cycles (or 30 milliseconds). During those 1.5 cycles, other separate circuits can see voltage dips or blinks until the affected circuit opens to stop the fault current. Automatically closing the breaker after it has tripped and...