How much knowledge do you have to know about the electrical industry?

1.Oil switch operation precautions

① When operating the remote control switch of the oil switch, do not use too much force to prevent damage to the control switch or return too fast to prevent the switch mechanism from closing.

② Manual slow division and slow down switching are prohibited during operation.

③ After the switch is operated, the relevant signal light and measuring instrument instructions should be checked to determine the correctness of the switch operation, but the actual splitting position of the switch should not be used as a basis to prove the actual splitting position of the switch. The mechanical position indicator of the switch should also be checked on site to determine the actual split gate position.


  1. How to deal with oil seeping into the oil switch and no oil level?

① Remove the DC control fuse

② Hang the “Do not pull the door” sign on the operating handle of the switch

③ Try to shift the load to deactivate this switch


  1. Inspection during the operation of the isolator switch?

① The porcelain part should be clean, without damage, cracks, or discharge

② The dynamic and static contacts are in close contact, and there is no overheating or loosening

③ The transmission mechanism should be intact, and the pin screws should not be loose


  1. What operations are performed with an isolating switch?

① Cooperate with the switch to perform reverse operation

② Pull in trouble-free voltage PT and lightning arrester

③ Connect and cut off an impedance-free parallel branch


  1. How to treat heat from the isolation switch?

According to the importance of the location of the isolation switch, lower the load current or ventilation cooling is used to reduce its heat generation. If the above treatment is not effective, report the relevant leadership to apply for power outage treatment.


  1. Why use oil as an arc extinguishing medium?

When the AB-3S Outdoor Permanent Magnet Vacuum Circuit Breaker cuts off the current, an electric arc is generated between the moving and static contacts. Due to the high temperature effect of the arc, the oil is violently decomposed into gas. Hydrogen accounts for about% in the gas, which can quickly lower the arc temperature and increase the insulation strength between the poles. At this time, extinguishing the arc is extremely beneficial .


  1. Why is the vacuum circuit breaker small in size and long in service life?

The AB-3S Outdoor Permanent Magnet Vacuum Circuit Breaker has a simple structure. A pair of contacts are placed in a vacuum-vacuumed glass. Due to the insulation of the vacuum, its arc extinguishing performance is particularly good. The opening distance between the moving and static contacts is very small (10kV is about 10mm, and the oil switch is about 10mm), so the vacuum breaks off The road device is very small in size and weight. Since the contacts of vacuum circuit breakers do not oxidize and stop the arc quickly, the contacts do not burn out easily, so they have a long service life (about four times that of an oil switch).


  1. The role of high voltage circuit breakers

① No-load current and load current of the circuit on or off during normal operation.

② When the electrical equipment or line fails, the high-voltage circuit breaker cooperates with the protection device to quickly and automatically remove the fault current.


  1. “Five defenses” to prevent misoperation

① Prevent accidental pulling and close the circuit breaker

② Prevent accidental pulling and separation switch with load

③ Prevent live joint ground isolation switch

④ Prevent the grounding wire from closing

⑤ Prevents accidental entry into the charging interval


  1. The order of picking and discharging the power fuse

When taking, take the middle first, back sides or top and bottom, the opposite when delivering


  1. Amps characteristics of fuses

The length of melt fusing time depends on the amount of current flowing through it. The relationship curve between current and fusing time is called protection characteristics, also known as amp-second characteristics.


  1. Selection of melt capacity of a single direct start motor

≥2-3 times the amount


  1. The role of the fuse

Protect electrical equipment from overload current and short circuit current damage.


  1. The role of DC systems

It provides reliable DC current for control, signal, relay protection, automatic devices, accident lighting, etc. It also provides reliable operating current for operation.


  1. Relevant regulations on DC systems

① The DC line voltage is kept at 230V, and the allowable range of variation is 22V-23V.

② When the battery is operated in a floating charge mode, each battery should be kept at 2.23V, the allowable range of changes is 2.1-2.2V, and stop discharging when the battery discharge voltage drops to 1.V.

③ The battery can be used normally at -1- 4 ℃. If used at the optimum ambient temperature of -30℃, the life can be extended.


  1. Differential protection effect and scope

As the main protection for the same fault inside the generator or transformer, the reaction acts by the difference in the secondary current of the current transformer installed on both sides of the equipment.


  1. Should I do work with high vibration, such as punching the eye with an electric drill on the switchboard?

① Obtain the consent of the manager to withdraw protection that may have been misspent

② Prevent short circuit errors or grounding caused by falling iron chips

③ Remove the secondary line etc. on the back of the eye position to prevent puncture or damage

④ Pay attention to the vibration of the disc on both sides of the eye plate

⑤ Personal supervision


  1. What is the cause of insulation aging?

During operation, the insulation of equipment is affected by electric fields, magnetic fields, temperature, and chemicals to make it hard, brittle, lose elasticity, and weaken the insulation strength and performance. This is normal aging, but unreasonable operation, such as overload, corona overvoltage, etc., can accelerate aging.


  1. How to delay insulation aging?

Choose proper operating methods, enhance cooling and ventilation, reduce equipment temperature rise, and isolate insulation from air or chemicals.


  1. What are the reasons that cause the CT in operation to have abnormal sound?

CT overload, secondary side opening, and discharge due to internal insulation damage can all cause abnormal noise. In addition, internal corona formed by uneven semiconductor paint and loosening of the clamping screws can also cause CT to produce loud sound.


  1. What are the placement standards for high-voltage electrical equipment?

The placement standards for high-voltage equipment are divided into three categories: the first and second categories are intact equipment, and the third category is non-intact equipment.

Class I equipment: It is equipment that has been tested in operation, is in good technical condition, has complete technical data, and can ensure safety, economy, full distribution, and supply.

Class II equipment: The technical condition of the equipment is basically good, and the individual components have general defects, but it can guarantee safe operation normally.

Three types of equipment: major defects, no guarantee of safe operation or reduced output, poor efficiency or oil leakage, serious steam and water.


  1. Why should operational analysis be carried out?

Operation analysis is mainly a comprehensive or thematic analysis of the operation status, safe operation, economic operation, and operation management of power generation and supply equipment. Through analysis, operation rules can be discovered, weak links can be identified, and preventive measures can be formulated in a targeted manner.


  1. Low voltage electric shock safety device

It is an effective protection device to prevent low voltage electric shock. If an electric shock accident occurs or insulation damage leaks, it will immediately cause an alarm or command to cut off the current, so that people and equipment can be protected.


  1. How to maintain and store safety equipment?

① The insulation rod should be stored vertically, placed on a stand or hung indoors, not against a wall.

② Insulating gloves and shoes are positioned in a cabinet and separated from other tools.

③ Rubber products for safety equipment must not come into contact with petroleum grease.

④ After use, the high-voltage tester is stored in the box and placed in a dry place.

⑤ The safe and secure storage location should be clearly marked so that it can be “seated in the right seat” for easy access.

⑥ Safety equipment must not be removed for other purposes.

⑦ Regular inspections and tests must be carried out.


  1. What is protective grounding and protection zeroing?

Protective grounding: In a system where the neutral point of the power supply is not grounded, the metal shell frame, etc. of electrical equipment is reliably connected to the earth through a grounding device.

Protection connection: In the power supply neutral point grounding system, connect the metal housing frame of the electrical equipment to the center line leading out of the neutral point.


  1. No-load current of asynchronous motors

Generally 20-3% Ie, maximum 0% Ie.


  1. What are the conditions to ensure that the motor starts and rises to the rated speed?

When the motor is running, there are two torques: one is the electromagnetic moment that causes the motor to rotate, which is generated after a three-phase current flows through the stator winding, and the other is the resistance moment that blocks the motor from rotating. It is generated by the mechanical load of the motor, and its direction is opposite to the direction of the rotor. In order for the motor to start up to the rated speed, the electromagnetic torque of the motor must be greater than the resistance moment in the entire range from zero to the rated speed of the unit. In a stable operating state, the electromagnetic moment is equal to the moment of resistance.


  1. How to test the voltage of the equipment before the maintenance work is completed?

①Evacuation of all staff from their duty stations.

② Withdraw all work tickets for the system, remove the temporary fencing, grounding wires and signs, and restore the permanent fence.

③The duty officer shall conduct a pressurization test after a thorough inspection by the person in charge of work and the duty officer.


  1. What safety tools should be used to operate high-voltage equipment?


Use an insulating rod to pull the isolation switch (knife brake) or pull the isolation switch (knife brake) and circuit breaker (switch) through a transmission mechanism, wear insulating gloves. When operating outdoor high-voltage equipment on rainy days, the insulation rod should have a rain cover, and insulation boots should also be worn. If the grounding grid resistance does not meet the requirements, insulation boots should also be worn on sunny days. To load and unload high-voltage fusible safes, wear goggles and insulating gloves, use insulating clamps if necessary, and stand on an insulating pad or insulating table.


  1. What causes the asynchronous motor to have too much no-load current?

① The power supply voltage is too high. At this time, the motor core magnetism is saturated, causing the no-load current to be too large

② Improper assembly, or the air gap is too large

③ The number of turns of the stator winding is insufficient

④ Silicon steel sheet corrosion or aging, or damage to intersheet insulation, etc.


  1. What are the reasons for the severe imbalance in the three-phase no-load current of asynchronous motors?

① Power supply voltage three-phase imbalance

② Stator winding disconnection

③ Short circuit between stator windings

④ The stator windings are one phase and reverse


  1. Why do some parts of the power plant need to use DC motors?

① The DC motor has good adjustment smoothness and a large speed regulation range.

② At the same output power, DC motors are lighter and more efficient than AC motors.


  1. Why is the protective grounding pin of an ordinary single-phase three-phase plug slightly longer than the others?

The purpose is that when the three-phase plug is inserted into a three-pole socket, the grounding pin is inserted into the socket before the other two pins, and the opposite is true when unplugged. This long foot always protects the grounding.


  1. What is the role of installing ground wires during equipment maintenance?

Reliable safety measures to protect workers from sudden calls at the workplace. At the same time, the remaining charge in the disconnected portion of the device can also be exhausted by grounding.


  1. Electrical testing procedures and precautions for electrical testing of high-voltage equipment?

When testing electricity, an electric tester with a suitable and qualified voltage rating must be used to test the electricity separately on both sides of the inlet and outlet of the equipment. Before the electric test, you must first verify that the electroscope is good on the electrical equipment. When there is no suitable electroscope, an insulating rod can be used to determine the presence or absence of voltage based on whether there is a spark at the end of the rod and the sound of discharge.


  1. What should I do if an electrical device catches fire?

Cut off the power supply of the relevant equipment and then fight the fire. Use dry fire extinguishers for live equipment, do not use foam fire extinguishers, and use foam fire extinguishers or dry sand to extinguish the fire for oil injection equipment.


  1. The phenomenon of self-perception and mutual understanding

Self-sensing phenomenon: The phenomenon of inducing electric potential in a coil due to changes in its own current

Mutual sensing phenomenon: The phenomenon in which one coil induces electric potential due to a change in the current of the other coil


  1. What is the skin collection effect?

When alternating current passes through a conductor, the current distribution is uneven everywhere on the conductor cross section. The density at the center of the conductor is minimal, and the closer to the conductor, the greater the surface density. This tendency to distribute current along the surface of the conductor is called the skin collection effect.


  1. What is the function of the automatic generator demagnetization device?

An automatic demagnetization device is an automatic device used to eliminate the generator’s magnetic field and the excitator’s magnetic field after the generator’s main switch and excitation switch trip. The purpose is to remove the generator voltage as soon as possible after the generator is disconnected to mitigate the consequences of the fault.


  1. What are the hazards of a dirty surface of a transformer casing?

Flasher is easy to occur when the surface of the casing is dirty, because the pressure-resistant strength of the air is not as strong as the casing. When the voltage reaches a certain value, if the surface of the casing is dirty, discharge occurs first on its surface. From weak to strong, the lowest voltage at which flashover occurs is called flasher voltage. If the surface of the casing is still wet, the flasher voltage is lower.


  1. What is the role of the grounded carbon brush on the main shaft of the steam turbine generator?

It is used to eliminate the electrostatic voltage of the large shaft to the ground.


  1. Motor step-down starting method

Y-Δ, autocoupled step-down, series reactor (in stator windings)


  1. What is the difference between a voltage transformer and an ordinary transformer?

PT is actually a step-down transformer. Since it has many turns of the coil at one time, few turns of the secondary coil, and the high impedance of the secondary load, the current that passes through is very small, so the working state of PT is equivalent to the no-load situation of the transformer.


  1. What are inductance, capacitance resistance, electrical resistance, and impedance?

When the AC current exceeds the inductance element, the inductor element’s ability to limit the AC current is called inductance; when the AC current exceeds the capacitive element, the capacitive element’s ability to limit AC is called resistance; the difference between inductance and resistance is called resistance; in a circuit with resistors, inductors, and capacitors in series, the overall blocking effect on AC is called impedance.


  1. In a DC circuit, how much is the inductance of an inductor and the capacitance of a capacitor?

In a DC circuit. The frequency of the current is equal to 0, so: the inductance is 0, which is equivalent to a short circuit, and the tolerance is infinite, which is equivalent to opening a circuit.


  1. What is series resonance? What are the characteristics of series resonance?

In P, L, and L series circuits, there is a phenomenon where the end voltage of the circuit and the total current of the circuit are in the same phase. At this time, the AC power supply only supplies the energy lost by the resistors in the circuit, and no longer exchanges energy with the inductor and capacitor. We call this series resonance.


  • The circuit has the smallest impedance and maximum current;
  • A very high resonant overvoltage may be generated on the inductor and capacitor.
  • Why should capacitors be connected in series in transmission lines?
  • Transmission lines have resistors and inductors. When the line transmits power, not only does it lose active power, but it also causes a voltage drop. In long-distance, high-capacity transmission lines, part of the inductance is offset by capacitive resistance, which can reduce voltage drop and improve voltage quality.


  1. What are the reasons that cause the transformer to run out of oil?

① Long-term oil seeping or massive oil leakage from the transformer;

② After the transformer is oiled, the oil is not filled in time;

③ The oil pillow has a small capacity and cannot meet the operating requirements;

④ The temperature is too low;

⑤ Oil storage in the oil pillow; the amount is insufficient.


  1. What harm does lack of oil in the transformer cause to operation?

Too low oil level of the transformer will cause light gas protection. The heat dissipation capacity of the transformer will decrease. When there is a severe shortage of oil, the iron core and coil will be exposed to the air and may cause insulation to break down.


The above is the basic common sense compiled by us for you. Is it helpful to you? Follow our official website to get more information about ZW32-12 Outdoor High Voltage Intelligent Vacuum Circuit Breaker, ZW32-24 Outdoor High Voltage Vacuum Breaker, etc.!

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