Auxiliary relay devices support protective relays by extending contact capacity, amplifying signals, and enabling remote control. Common in switchgear and automation, they enhance fault detection, interlocking, and the reliability of electrical protection schemes. Tripping circuit breakers and operating alarms in control and protection applications usually require more than one relay contact. In. Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. High voltage systems, like a high-voltage battery in an electric vehicle, need solid-state relays to control a high voltage load with a low voltage signal.
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