1. Why is the switch cabinet called "complete set", and what cabinet is it composed of?
The switch cabinet is composed of inlet line, metering, PT, outlet line and so on. The cabinet is equipped with primary and secondary components, which must be matched when purchased, so it is called "complete set".
2, how many levels of continental power voltage, and say the role of grading.
It is divided into 500KV, 220KV, 110KV, 35KV, 10KV, 380V, 220V and other levels.
Since the level of the voltage is related to the line loss, the higher the voltage, the lower the line loss. In this way, the farther the distance of electricity transmission, the higher the voltage level that needs to be delivered.
3. Why should I unload the voltage (10KV level)? What methods can be used to safely remove the voltage?
In the event of a power outage, in order to prevent the capacitor from having residual electricity and injuring the person, the voltage must be removed.
Method for safe voltage removal: When opening the cabinet door or screen plate, do not directly touch the busbar with your hand. First use the 10KV test pen to check whether there is electricity, and then find a wire, one end is grounded, one end is connected to the front end of the test pen, and the front end of the test pen is used to contact the busbar discharge, and only after completion can it be repaired to ensure personal safety. Keep this in mind.
4. What should be the voltage of 10KV test electricity? What is the difference between domestic and international standards?
Domestic: cabinet 42,000 volts, fracture 48,000 volts;
International: 36,000 volts
5. How to understand the meaning of KYN letters in switchgear model?
K—Metal-enclosed armored type
Y—Move away
N—Indoors
6. What is the role of the pressure relief channel?
If the cabinet explodes, it will produce a strong air wave. At this time, if there is a pressure relief channel at the top of the cabinet, the air wave can be discharged from the top without affecting the normal work of other parts; if there is no pressure relief channel, the air wave will rush to the weakest place.
7. What are the main primary components of the switch cabinet?
Circuit breakers, contact holders, lightning arresters, zero-sequence transformers, current transformers (CT), voltage transformers (PT), high-voltage fuses, etc.
8. What is the role of the ring network switch cabinet? What protects the transformer?
The role is to divide and close the gate with load, and he relies on a high-voltage fuse to protect the transformer.
9. What is the national standard for air insulation distance?
The relative air distance between phases, 10KV requires 125mm.
10. What is the climbing distance of insulators?
The high-voltage live side to ground, along the surface of the insulation crawling through the conduction distance is called the insulation crawling distance. 10KV requires 235mm.
11. What method is used to check whether the vacuum switch is vacuum?
Tested with a pressure test. The fracture is detected with 48,000 volts.
12. What is the role of isolation plug and isolation switch, and what kind of cabinet is used?
Isolated plug for handcart cabinets; disconnectors for fixing cabinets. Its role is to close the gate without load, which is convenient for maintenance.
13. What are the currents of the high-voltage cabinet roughly divided into? What level does the load switch belong to?
It is divided into large, medium and small, that is, 3150A, 1250A, 630A three levels. The load switch is 630A class.
14. What is the role of high-voltage fuses?
For the protection of transformers, PT belongs to the small transformer class.
15. What is the function of the live display?
Acts as an indicator to show whether there is a high voltage in the cabinet.
16. What is the role of the program lock? Where is it installed?
The order of operation of cabinets and cabinets is chained according to the prescribed procedures, which plays a role in preventing misoperation.
17. What is the role of the ground switch?
The grounding switch is installed at the outlet end, which can prevent the reverse supply of high voltage electricity during maintenance and ensure personal safety.
18. What is the function of the trapdoor?
When the handcart pulls away from the cabinet, it prevents people or metals from touching static contacts with high voltage electricity.
19. Why should the busbar be glued?
It plays an insulating role, which can reduce the air insulation distance and prevent small animals from entering the cabinet and causing short-circuit accidents.
20. What is the role of the lightning arrester? Why does every cabinet have at least one arrester?
The lightning arrester is designed according to the voltage level and must not be misfitted. Some are also designed differently depending on the purpose. Such as: power plant output electricity, line operation, capacitance.
The lightning arrester is mainly when an excessive voltage is generated in a certain section of the line, which can be absorbed to achieve the purpose of safe operation of the line. For example: the inlet cabinet has a set of lightning arresters, which can protect the safety of the line in the cabinet; and the external power supply has been equipped with a lightning arrester when entering the cabinet, so if the external power supply generates high voltage, due to the lightning arrester as protection, it is safer to enter the cabinet; the lower end of the outlet cabinet is equipped with a lightning arrester, mainly considering the overvoltage phenomenon that will occur when the vacuum circuit breaker is split, so it is necessary to install a lightning arrester instead of an overvoltage absorber.
21, how to distinguish between phase color and phase arrangement.
| yellow | green | red | blue | Yellow and green |
| A | B | C | neuter | |
| left | middle | right | Far left | |
| after | former | First | ||
| above | under | bottom |
22. Talk about the role of current transformers and zero-sequence transformers.
Current transformer plays a role in metering protection;
Zero-sequence transformers play a protective role.
23. Can the current transformer be rewound and assembled? Why?
Normal flow to L1→ L2, if L2 → L1, the quadratic line design needs to be modified.
24. What is the difference between VE cabinet and ring network cabinet?
The VE cabinet (hand model) is broken with a circuit breaker and protects the transformer for 0.2 seconds
Ring network cabinet (fixed type) with a high voltage fuse to protect the transformer for 0.02 seconds
25. What is the role of the wet controller?
The humidity is detected by the induction probe, if it exceeds the normal humidity, and the heat is adjusted by the heating plate. There are two ways of operation: automatic and manual.
26. What is the role of the primary scheme diagram?
Represents the original and direction assembled on the main loop route
27. What do PT and CT names represent?
PT—Voltage Transformer, CT—Current Transformer
28. What do ac and DC names represent?
AC-AC, DC-DC
29. How many operating mechanisms are there for circuit breakers?
Manual, automatic power separation, magnetic, spring, contactor magnetic suction. Such as: low-pressure air switch with manual
CD10 or CD17 for high-pressure vacuum switches (electromagnetic mechanism)
With CT8 or CT19 (spring mechanism)
30. What is the role of the empty switchgear, and what does it rely on to protect the transformer?
Its role is vacuum arc extinguishing, can be divided and closed with load, for transmission of electricity, relying on current transformers and instruments to cut off the current to protect the transformer. It can also be equipped with other components for other purposes.
31. What is the role of the vacuum circuit breaker?
Can be closed with load, with vacuum to extinguish the arc.
32. What should be the vacuum switch stroke?
Stroke: 11±1 Spring compression: 4±1 VE: 8±0.5
33. Classification of circuit breakers:
(1) Vacuum circuit breaker: the use of vacuum (vacuum degree of 100,000 mercury column or less) as the arc extinguishing medium and the main insulating medium. The dynamic and static contacts of the arc extinguishing are sealed in the vacuum arc extinguishing chamber. There are mainly 10VK. 35KV voltage rating.
(2) Sulfur hexafluoride circuit breaker: came out late. It was only widely used in the early 1970s and is now an advanced device in the power system, with SF6 gas as the arc extinguishing medium. The cutting capacity is about 10 times higher than that of general circuit breakers. Low arc voltage. The short arc time contacts burn out less and can be operated frequently. DisadvantageSavery SF6 is more expensive. Recycling devices are required and the structure is more complex. Continental has manufactured fully enclosed combination electrical appliances with an attendance rate of 220KV and SF6 as the main body. Put the circuit breaker, the disconnector. Instrument transformers, lightning arresters. The main equipment of the busbar and other substations is all installed in a sealed container with SF6 gas, which greatly reduces the space occupied by the substation. It is the main direction of the development of ultra-high voltage electrical appliances. It has been widely used abroad.
(3) Circuit breaker: compressed air as the arc extinguishing medium. In terms of ultra-high pressure, it is currently the main generator. 380KV is produced in mainland China. It has produced 765KV abroad.
(4) Self-produced circuit breaker: the use of fixed medium by arcing decomposition into gas for arcing so that the arc is extinguished. Low voltage and low current interruption. Suitable for agricultural electronic systems.
(5) Magnetic blowing circuit breaker: the use of magnetic field to blow the arc into the arc extinguishing grid.
34. Power transformer
A transformer is an electrical device that converts voltage (current). It cannot convert power.
Basic structure: mainly composed of a closed iron core and wound on the iron core two turns of different numbers and insulation of the coil (that is, winding), in order to reduce the eddy current and hysteresis loss, the core is coated with insulation paint, the thickness of 0.35-0.5mm magnetic conductivity of the silicon steel sheet is stacked, it constitutes the closed magnetic circuit in the transformer Primary coil called thick coil type primary side, the secondary coil is called the pay coil pay edge, with a three-point single-phase transformer connected into a three-phase transformer group, is a three-phase transformer.
35. Current transformer
Basic structure: A current transformer is a converter used to expand the range.
The basic structure is the same as the ordinary voltage device, but also by the iron core and the original coil wrapped around the iron core, when used, the main side and the tested circuit load in series, the pay side is connected to the 5A ammeter and the protection relay current coil because of its original side with a thick wire, the number of turns is only one turn or a few turns, solid and its electric cathode is small, the voltage is very low, after stringing into the circuit under test, it does not change the supplementary measurement current, the pay side wire is very thin, the number of turns is many, but its induction potential is not high (only a few volts) The pay-edge ammeter and relay coil resistance are very small When working, the fu edge can be regarded as a short-circuit state, according to the operation principle of the transformer: the ratio of the primary current of the electric charging transformer should be inversely proportional to the number of turns:
L1/L2=W2/W1 or L1=W2/W1L2. W2/W1=K2 ratio.
36. Voltage transformer
Basic structure: It is a special transformer that expands the voltage range, and the basic structure is the same as that of ordinary transformers. Therefore, the voltage relationship between the primary side of the voltage transformer and the paid voltage U1/U2 =W1/W2.
37. Lightning arrester
Rationale: When an overvoltage is transmitted. Internal and external clearance S1, S2 simultaneous breakdown. The powerful lightning current flowing into the earth through the grounding device limits the amplitude of the overvoltage.
One of the largest lightning accidents in China: 1989.8.12 Shandong Huangdao Oil Depot extraordinarily large fire. Nineteen people died and 78 were injured. 3。 60,000 tons of crude oil were circumvented by the fire. Direct loss of hundreds of millions of yuan.
38. High voltage insulator
High voltage insulator function: used to support and fix the busbar and the charged conductor, and so that there is enough distance and insulation between the live conductor or between the conductor and the earth; the insulator insulation is obtained by the surface shape.
Insulators of different voltage levels. In addition to having different effective heights. The surface is also different. Its surface is made of high and low skirts. to increase its surface length.
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