[Engineering Version] Daily Question 20180122
Thread Content
A certain group is responsible for constructing an experimental building project located in a densely populated area. The total construction area is 30,000㎡, with 16 floors above ground and 2 floors below ground; the structure uses a frame-shear wall system. The construction site employs a three-level power distribution system; the main power supply lines are overhead, while the branch lines and power supplies entering the building are laid using buried cables. During design and construction, fuses are used in the lighting distribution box for circuit protection. When wiring, the protective neutral wire is red and single-stranded, while the power supply wires are connected from the outside of the box. Both cable lines and indoor lines are equipped with short-circuit protection. The on-site rebar cutter is directly controlled by a switch box located 5 meters away from it. Questions: (1) What is a “three-level power distribution” system? (2) During the use of power distribution boxes and switch boxes, what are the sequences for turning power on and turning it off respectively? (3) Identify the issues in this case and explain the reasons. Correct answer: (1) A three-level power distribution system refers to a power distribution method that consists of a main distribution cabinet or box, distribution boxes, and switch boxes at three levels. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
A certain group is responsible for constructing an experimental building project located in a densely populated area. The total construction area is 30,000㎡, with 16 floors above ground and 2 floors below ground; the structure uses a frame-shear wall system. The construction site employs a three-level power distribution system; the main power supply lines are overhead, while the branch lines and power supplies entering the building are laid using buried cables. During design and construction, fuses are used in the lighting distribution box for circuit protection. When wiring, the protective neutral wire is red and single-stranded, while the power supply wires are connected from the outside of the box. Both cable lines and indoor lines are equipped with short-circuit protection. The on-site rebar cutter is directly controlled by a switch box located 5 meters away from it. Questions: (1) What is a “three-level power distribution” system? (2) During the use of power distribution boxes and switch boxes, what are the sequences for turning power on and turning it off respectively? (3) Identify the issues in this case and explain the reasons. Correct answer: (1) A three-level power distribution system refers to a power distribution method that consists of a main distribution cabinet or box, distribution boxes, and switch boxes at three levels. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
Answer: (1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During use, the sequence for supplying power to distribution boxes and switch boxes is: main distribution box – distribution box – switch box; the sequence for shutting off power is: switch box – distribution box – main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection devices for lighting distribution boxes; instead, low-voltage circuit breakers should be employed, and the cross-sectional area of the wires must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations stipulate that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 m.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used for circuit protection in lighting distribution boxes; low-voltage circuit breakers should be employed, and the cross-sectional area of the circuits must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 m.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 m.
(1) A three-level power distribution system refers to a power distribution method that consists of a distribution cabinet or main power distribution box, a sub-distribution box, and a switch box. (2) During the use of distribution boxes and switch boxes, the sequence for supplying power is as follows: main distribution box – distribution box – switch box ； The power supply sequence is: switch box—distribution box—main distribution box. (3) The issues are as follows: ① Fuses should not be used as protection for the wiring in the lighting distribution box; low-voltage circuit breakers should be employed, and the cross-sectional area of the wiring must be compatible with those circuit breakers. ②The protective neutral wire should be a green/yellow dual-colored wire with multiple conductors, and the power cable should be connected at the inlet at the bottom of the electrical box. ③In addition to short-circuit protection, cable circuits and indoor circuits should also have overload protection. ④It is inappropriate for the on-site rebar cutting machine to be directly controlled by a switch box located 5 meters away from it. The regulations specify that the horizontal distance between the switch box and the fixed electrical equipment it directly controls should not exceed 3 meters.