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Table 41.1 Assumed Touch Voltage
Former Community Member
I am a bit confused by this. Why do the disconnection times in Table 41.1 appear to be based on a touch voltage of 100 volts rather than a touch voltage of 125 volts?
For example, 110% of 230= 253 volts. Assuming L and PE are of the same size and material, indirect contact touch voltage is 126.5 volts. Would 0.33 seconds not appear more realistic?
The 13th Edition of the Regulations for the Electrical Equipment of Buildings, 1955, required the use of Voltage Operated Earth Leakage Breakers if the loop impedance was too high to allow reliable operation of fuses or circuit breakers. Reg.410.
Reg. 406 recommended that a maximum Voltage of 40 Volts be tolerated on exposed earthed metal and consumer's earth terminal under fault conditions.
Edit. Add. The 1975 edition of the booklet by Crabtree entitled "The Protection of Domestic and Industrial Installations" 1975, 6th edition, mentions both Voltage and current operated earth leakage circuit breakers for protection of hand held appliances and reduced fire risk. (B.S. 842; 1965 and B.S. 4293 1968. respectively). The normal out of balance operating current for current operated devices was typically 500mA at the time. 25mA high sensitivity devices were also available.
Mention in the Crabtree publication of 50mA being the lower limit of lethal current.
Edit 2. Add. The 14th Edition 1966 I.E.E. Regs. mentions current operated earth leakage circuit breakers. My copy is dated 1976.
Reg. D.24 required that a current operated earth leakage circuit breaker should only be used where the product its operating current in Amps. and earth loop impedance in Ohms does not exceed 40.
The 13th Edition of the Regulations for the Electrical Equipment of Buildings, 1955, required the use of Voltage Operated Earth Leakage Breakers if the loop impedance was too high to allow reliable operation of fuses or circuit breakers. Reg.410.
Reg. 406 recommended that a maximum Voltage of 40 Volts be tolerated on exposed earthed metal and consumer's earth terminal under fault conditions.
Edit. Add. The 1975 edition of the booklet by Crabtree entitled "The Protection of Domestic and Industrial Installations" 1975, 6th edition, mentions both Voltage and current operated earth leakage circuit breakers for protection of hand held appliances and reduced fire risk. (B.S. 842; 1965 and B.S. 4293 1968. respectively). The normal out of balance operating current for current operated devices was typically 500mA at the time. 25mA high sensitivity devices were also available.
Mention in the Crabtree publication of 50mA being the lower limit of lethal current.
Edit 2. Add. The 14th Edition 1966 I.E.E. Regs. mentions current operated earth leakage circuit breakers. My copy is dated 1976.
Reg. D.24 required that a current operated earth leakage circuit breaker should only be used where the product its operating current in Amps. and earth loop impedance in Ohms does not exceed 40.
