Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current

Child Classifications

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• H01H 83/02 operated by earth fault currents (H01H83/14 takes precedence)
• H01H 83/06 operated by current falling below a predetermined value
• H01H 83/08 operated by reversal of DC
• H01H 83/10 operated by excess voltage, e.g. for lightning protection
• H01H 83/12 operated by voltage falling below a predetermined value, e.g. for no-volt protection
• H01H 83/14 operated by imbalance of two or more currents or voltages, e.g. for differential protection
• H01H 83/16 operated by abnormal ratio of voltage and current, e.g. distance relay
• H01H 83/18 operated by abnormal product of, or abnormal phase angle between, voltage and current, e.g. directional relay
• H01H 83/20 operated by excess current as well as by some other abnormal electrical condition