Recloser

In electric power distribution, automatic circuit reclosers (ACRs) are a class of switchgear which is designed for use on overhead electricity distribution networks to detect and interrupt momentary faults. Also known as reclosers or autoreclosers, ACRs are essentially high voltage rated circuit breakers with integrated current and voltage sensors and a protection relay, optimized for use as an overhead network distribution protection asset. Commercial ACRs are governed by the ANSI/IEEE C37.60, IEC 62271-111 and IEC 62271-200 standards. The three major classes of operating voltage are 15.5 kV, 27 kV and 38 kV. In electric power distribution, automatic circuit reclosers (ACRs) are a class of switchgear which is designed for use on overhead electricity distribution networks to detect and interrupt momentary faults. Also known as reclosers or autoreclosers, ACRs are essentially high voltage rated circuit breakers with integrated current and voltage sensors and a protection relay, optimized for use as an overhead network distribution protection asset. Commercial ACRs are governed by the ANSI/IEEE C37.60, IEC 62271-111 and IEC 62271-200 standards. The three major classes of operating voltage are 15.5 kV, 27 kV and 38 kV. For overhead distribution networks, the majority of faults are transient, such as lightning strike, surges or foreign objects coming into contact with the exposed distribution lines. By this logic, 80% of outages can be resolved by a simple close operation. Reclosers are designed to handle a short close-open duty cycle, where electrical engineers can optionally configure the number of attempted close operations prior to transitioning to a lockout stage. Reclosers were invented in the mid 1900s in the USA. Some of the earliest reclosers were introduced by Kyle Corporation (which was acquired by Cooper Power Systems - part of the Eaton family) in the early 1940s. The brand was the industry leader in reclosers, sectionalizers and switchgear until the 2000s when many other manufacturers entered the market. Reclosers were originally oil filled hydraulic devices with rudimentary mechanical protection relaying capabilities. Modern automatic circuit reclosers are significantly more advanced than the original hydraulic units. The advent of semiconductor based electronic protective relays in the 1980s resulted in increased sophistication, allowing for differing responses to the various cases of abnormal operation or fault on a distribution networks. The high voltage insulation and interrupting device in modern reclosers typically consist of solid dielectric insulation with vacuum interrupters for current interruption and arc quenching. Reclosers are often used as a key component in a smart grid, as they are effectively computer controlled switchgear which can be remotely operated and interrogated using SCADA or other communications. This capability allows utilities to aggregate data about their network performance, and develop automation schemes for power restoration. This automation can either be distributed (executed at the remote recloser level) or centralized (close and open commands issued by a central control room to be executed by remotely controlled ACRs). In order to prevent damage, each station along the network is protected with circuit breakers or fuses which will turn off power in the event of a short circuit. This presents a major problem when dealing with transient events. For instance, a tree limb blown off a tree during a windstorm that lands on the power line may cause a short circuit that could cause damage. However, the fault could quickly clear itself as the limb falls to the ground. If the only protection system is provided by breakers at distribution substations, large areas of the distribution network could be blacked out while repair crews reset the breakers. Reclosers are programmed to automate the reset process and allow a more granular approach to service restoration. The result is increased availability of supply.