Low Voltage Electrical Operator Certificate Exam Question Papers

Low-voltage electrical operation certificate examination paper (1)

Hello, you can the following topics look familiar, the teacher together with the past paper, basically, there is no difficulty. Transportation energy, generally the larger the capacity, the longer the transmission distance, the transmission voltage should be reduced security.

Voltage transformer metal core and secondary side of one end of the shell should be firmly connected to ground or zero.

Current transformer meter exchange should be in the operation process, to prevent secondary short circuit.

High and low high-voltage disconnect switches can not be used to turn on and off load currents, but can turn on short-circuit currents.

Is the high and low voltage disconnect switch must be the corresponding high and low voltage circuit breaker, power supply, you should first turn off the disconnect switch and turn off the circuit breaker when the power supply works in the same order.

Under normal circumstances, substation blackout, close the first sub of each load switch, break up after the capacitor bank switch.

The temperature of the oil on the transformer tank should not exceed 55 ° C, and must be protected by the use of

Capacitor bank discharge circuit breakers and fuses. Artificial methods of compensation

Improve the power factor is usually enough capacity with inductive loads in series with capacitors.

Shanghai regulations: point of entry into the home grounding should not be small, 2.7M

Shanghai region requires: minimum cross-sectional area of entry into the home line 4M square meters.

Shanghai requirements: good insulation copper or aluminum hard wired into the home line should be used.

Distribution room should be well ventilated to ensure safe and reliable lighting system, indoor lighting power switch should be located within the distribution room.

Current transformer secondary circuit shall be installed in the fuse short circuit protection.

In Shanghai regulations: the center of the billing energy meter should be located 1.4-1.8M from the ground

The ratio of the upper and lower fuse rated current of the fuse should be less than 2 times.

Insertion of fuses should be installed vertically and the rated current of the fuse should be not less than the rated current of the fuse.

The ambient temperature of the capacitor room shall not exceed 35 ° C.

Wire equipment should have sufficient insulation strength, indoor wires, cables should be not less than AC 450/750

The maximum current allowed for wires and cables depends on the cross-sectional area on which the material structure of the way it runs.

The choice of cross-sectional area of the conductor, the splitter requirements must be met by the distribution of the branch line, the number of lights illuminating each single-phase parallel connection lamps should not exceed 15.

The number of single-phase parallel-connected lamps for building profile lighting should not exceed 50.

Distribution branch line, each electric shunt maximum load current does not exceed 25A. main cycle / & gt; gas discharge lamps, N wire cross section should not be larger than the phase line cross section.

Plastic sheathed cable laying minimum cross-section? Copper, indoor 1.5 m square meters, head self-tapping head or in the junction box.

Sheathed cable grounding conductor is not hot pipe in the cross, plus steel protection place vulnerable to mechanical damage should be added insulation protection.

Through the pipe wire rated voltage should not be less than AC 400V wire pipe, no joints.

The minimum cross-section of the conductor through the tube should not be 1 million square meters, aluminum wire insulation wire insulation copper cable should not be 1.5 m ㎡. /> Steel pipe, connected to the beam section of the application of round or flat steel across the ground at both ends, become a good electrical path in any two of the resistance value should be less than 4 ohms /> Tube bending angle of the surface line radius should be not less than 6 times the diameter of the pipe conduit pipe. /> Pipe bending should not exceed 90 ° between the angle of bending diameter should not bend narrow.

Laying cables to a depth of not more than 0.7 meters

Metal trunking, control, signaling or similar wires, wires or cables should not exceed the total cross-section of the conduit 40 ‰ cross-section of the number of wires and cables there is no limit.

Use yellow/green wire jumper at both ends, wire trough metal wire trough inner connection should be firmly grounded or connected to zero, and at the same time it can be used as equipment grounding conductor. The set of /> temporary line up, should be connected to the power supply at one end, by the end of the electrical equipment, and then in reverse order, when the line is removed.

Temporary power switches, outlets, fuses and leakage protection for outdoor electrical equipment should be installed in the switch box.

Crowded areas must use a separate local lighting.

Chandeliers weighing more than 1 kg, metal chains or other means to support the force of the chandelier online.

Lighthouse fluorescent lamps are not closed in flammable building planes, flat-top fluorescent ballasts, should be kept sealed.

Halogen lamps should be installed horizontally, not more than 10 ° tilt, otherwise it will shorten the life of the bulb.

Moving household appliances, electrical switches must be broken.

Common areas of business should be as far as possible, I like it, and the use of Class II tools, equipment requires leakage protector or isolation transformer.

Boilers, metal containers, piping and other confined spaces, should use Class II tools.

Protective conductors are connected to the ground or zero system with insulated copper wires, the section should not be 1,5 mm

Lightning protection consists of a flashover, a lead wire and a ground wire.

The protective radius of the lightning rod 0,5 times the height of the lightning rod on the ground.

Equipment with lightning rod of the building or structure, allowing electrical equipment grounding *** the same point, but *** the same grounding device grounding resistance is less than 4 ohms.

Equipment lightning arrester to prevent lightning wave intrusion, installed as close as possible to the protected, independent grounding device resistance is small, should be 4 ohms

All portable electronic equipment and hand-held power tools residual current must be installed to protect the device. /> To avoid failure, leakage protection, the inoperative current is 1/2 of the operating current is less than

Wires and cables in the current will heat up, but through the normal maximum load current of the heating temperature of the normal operation is lower than the maximum allowable temperature. />Three-phase four-wire or two-phase three-wire distribution lines, when most of the single-phase electrical equipment power loads, the cross-section of the N wire or PEN wire is not readily greater than the phase line cross-section.

Tube wiring, moisture-proof, fire-resistant, corrosion-resistant moths, etc., you can use it in places with severe rotting metal termites.

AC circuits in the wire should be threaded through the steel pipe, plastic pipe is not allowed to wear monofilament, but DC circuits and protective grounding wire. /> Semi-rigid plastic pipe can only be used for six years below the ordinary residential, the minimum diameter should not be less than the inner diameter of 10mm /> AC single-core cables can not be threaded in steel, but the same cycle, a single cable is threaded into a steel pipe with the same.

Metal wireway connections should be uninterrupted, from the outside to the inside of the fixing and locking device of the connecting bolts. />Low-voltage circuit breakers are widely used as protection for electrical low-voltage distribution lines, and can also be used as control switches for frequently starting motors. />Installation of open-type load switches, mounted vertically, should be done so that each direction from the top to the bottom of the receipt, from the bottom of the switching operation of the tap to prevent accidental closure.

In the same power system, power equipment should be protected to zero, lighting and sockets can be used to protect the ground.

Ammeters shall be connected to the measured load circuit and voltmeters shall be connected in series to the measured load circuit. Read

Insulation resistance meter to measure the insulation resistance of electrical equipment should stop shaking. /> Multimeter to measure the AC voltage, DC voltage, current, resistance of electrical equipment in the state of charge.

As long as more than 4 to 6 minutes, cerebral hypoxia can cause irreversible damage, so once found, it is "clinical death", it is necessary to immediately carry out artificial respiration mouth-to-mouth artificial respiration.

"Clinical death" occurs when electrocution of tissue cells in the body of severe hypoxia, very urgent, time is life, must be immediately sent to the hospital.

In vitro cardiac massage, your hands, heels should be placed on the part of the clamp holding the right, it is the left side of the chest exposed head.

Not get a special operations license electrician, maintenance work can only be in all electrical equipment or lines.