Select the residual current circuit breakers should be used in accordance with the purpose and according to operating conditions:
For protection purposes: ① to prevent personal shock for the purpose. Installed at the end of the line, the choice of high sensitivity, fast leakage protector. ② to prevent electric shock for the purpose of grounding and equipment used in the branch line, the choice of sensitivity, fast leakage circuit breaker. ③ to prevent residual current caused by the fire and the protection of lines, equipment for the purpose of the trunk, should be used in the sensitivity, delay type leakage circuit breakers.
According to the power supply options: ① protection of single-phase line (equipment), the choice of single-pole two-wire or two-pole residual current circuit breaker. ② protection of three-phase lines (equipment), the choice of three-pole products. ③ both three-phase and single-phase, the choice of three-pole four-wire or four-pole products.
When selecting the number of poles of the circuit breaker, it must be adapted to the number of lines to be protected. The number of poles of the circuit breaker means that the internal switch contacts can disconnect the number of wires, such as a three-pole circuit breaker, which means that the switch contacts can disconnect three wires. The single-pole two-wire, two-pole three-wire, three-pole four-wire circuit breakers, there is a direct through the leakage detection components without breaking the neutral line, in the protector housing terminal marked "N" Work zero line, this terminal is strictly prohibited with the PE line connection. It should be noted that the triode residual current protector should not be used for single-phase two-wire (or single-phase three-wire) electrical equipment. It is not advisable to use a four-pole residual current circuit breaker for three-phase three-wire electrical equipment. But also not allowed to use three-phase three-pole residual current protector instead of three-phase four-pole leakage circuit breaker.