1. Please briefly describe what are the conditions for parallel operation of transformers? (5 marks)
1. same rated voltage
2. Ud% difference not more than 10%
3. same grouping
2. What should be checked before installation of transformer? (5 points)
1, transformer oil leakage phenomenon
2, transformer vials have broken crack phenomenon
3, transformer characteristics test, including (direct resistance, insulation, withstand voltage, ratio, capacity)
4, to remove the dust
3, ordinary microcomputer line protection of the three-stage protection refers to what? (5 pts)
Current flow interruption,
Time-limited current flow interruption
Overcurrent protection
4. What is the role of shunt capacitors in a power system? (5 marks)
1. to compensate inductive current
2. to increase the grid voltage
3. to suppress harmonics
5. What are the roles of conductive paste? What are the main applications? What are the precautions for using conductive paste? (5 points)
Conductive paste can protect the contact surface of the conductor from oxidation, mainly used in the copper row lap surface, isolation switch bite. Conductive paste should be applied evenly, not too thick, pay attention to the aesthetic.
6. A 500kVA 10kV ohmic transformer, if you choose the frame switch of Zin low as the main incoming switch, how should the parameters and models be selected? (5 points)
ATW30-1000 Drawer switch 3P, operating power AC220V, standard control module.
7. In what order are the trip buttons and indicators on the switchgear instrumentation door? What are the respective colors? (5 points)
Indicator lamps Yellow Red Green Storage, closing position, splitting position
Buttons Green Red Closing, splitting
8. What are the five precautions in a switchgear cabinet? (5 points)
1. preventing pulling the disconnecting switch with load;
2. preventing pulling the circuit breaker by mistake;
3. preventing hanging the ground wire with electricity;
4. preventing closing the gate with the ground wire;
5. preventing entering into the energized interval by mistake.
9. Draw a schematic diagram of the AC contactor control loop for the two-button method. (5 marks)
10. What is the difference between European type cable branch box and American type cable branch box? (5 points)
1, the difference between the rated current: European cable branch box for 630A, American cable branch box for 600A.
2, the difference between the cable head: European cable branch box with European cable head, European cable head can be touched and can not be touched two kinds of cable head, the American cable branch box with American cable head, only touchable.
3, installation: European cable branch box using the mother row for the wall casing form, American cable branch box using the mother row for the shaped mother row.
11. two main transformer 35kV substation, if the protection device of Antoni, how should the main transformer protection be configured? How many protection devices are required? (5 points)
Set up a high backup, transformer differential, switching signals of the measurement and control of the measurement and control device, but also add a low backup
ASB225B high backup AST211 differential ASR-221 measurement and control, if necessary, you can add a low backup
ASB225B
12. 10kV and 35kV What are the safety distances (describe phase-to-phase, phase-to-ground, and disconnect, respectively)? (5 marks)
Voltage level Phase-to-phase Relative ground Fault
10kV 125mm 125mm 125mm 125mm
35 kV 300 mm 300 mm 300 mm 300 mm
13. Briefly state the value of the frequency withstand voltage of the main circuit of the 10 kV and 35 kV switchgear and the transformer (describe the phase-to-phase, ground-to-ground, and fault respectively)? (5 marks)
Voltage level Main circuit phase-to-phase Main circuit relative ground Main circuit interruption Transformer
10kV 42 kV 42 kV 48 kV 35kV
35 kV 95 kV 95 kV 118 kV 65 kV
14. Briefly describe the difference between a circuit breaker, a load switch, and an isolating switch? (5 points)
Circuit breakers are used to separate the short-circuit current and more frequent operation of the place, the price is high
Load switches can only separate the rated current, used in infrequent operation and can be the normal break current place, in the fuse with the protection of transformers and so on
Disconnecting switches are only used for the separation of the line role, to give the person to operate a clear point of disconnection
15. substation "five remote" are what? (5 points)
Remote control, telemetry, telemetry, telecommunication, remote control, remote vision
16. What are the power system grounding methods? (5 points)
Low voltage is generally directly grounded, 10kV is generally not grounded, 35kV is not grounded or grounded by high resistance, as well as through the arc arc-absorbing coil grounding (or grounding variable)
17. Please briefly explain the meaning of the accuracy level of the current transformer, 0.2S/0.5/10P10? (5 points)
0.2S refers to the accuracy of 0.2% and can meet certain 0.2S refers to 0.2% accuracy and can meet a certain amount of magnetic through the saturation margin
0.5 refers to the accuracy of 0.5%
10P10 accuracy of 10% overload multiplier of 10 times
18. What is the protection level of the company's ordinary European-style box variable? What is the meaning? (5 points)
IP33
19. What should I pay attention to when using current transformer wiring? (5 marks)
Current transformer wiring should not be open to prevent high voltage
20. Briefly describe the types of protection that should be configured in a 35kV conventional substation? (5 marks)
1. The substation should be equipped with transformer protection differential, high backup, low backup, transformer measurement and control of voltage regulation
2. 35kV inlet line protection or inlet line ready to throw device
3. 10kV or 35kV with sectionalized section of sectionalized section of ready to throw device
4. 10kV with line protection
5, 10kV capacitor protection
6, 35kV or 10kV with station variable protection
Mechanical test questions (100 points)
21. XGN-12 cable feeder cabinet (with the upper and lower isolation and grounding switches), briefly describe the sequence of blackout operations? (5 points)
Shutdown sequence: button or switch to split the circuit breaker, the operating panel lower isolation, upper isolation, upper grounding, lower grounding, the operation is completed after locking the opening of the lower door, open the lower door, the straight toggle locks open after opening the back door, (can also be the back door sealed)
22. Design of cold stamping parts, you have comprehensively considered the material utilization of the steel plate? How much should be achieved? (2 points)
23. Label the general hardening requirements (Rockwell hardness) for No. 45 steel using drafting symbols. (2 marks)
HRC52~60 is required
24. What is the approximate height of an ordinary M10 nut (GB41-86)? What is the thickness of the ordinary flat washer? What is the thickness of spring washer? (3 points)
25. mechanical parts design: switchgear interlock design. Known: door width: 750mm, door height: 820mm, curved height of 30mm. requires three points of contraction, open and lock the door is convenient, please draw a sketch (please pay attention to the drawing specifications, with CAXA in the air under the paste figure). (5 points)
26. 10kV European box variable, frame total height of 2050mm inside the box, what is the maximum height of the cabinet can be installed? How is it calculated? (5 marks)
1800, 2050 - top and bottom channel 100 = 1950 - turn over 2*25 = 1900
So the maximum height should not be greater than 1800
27. State the tonnage of the two CNC punching machines used by my company? What is the number of workstations? (8 marks)
28. Please state the tonnage of the two bending machines used by my company? (4 marks)
10 tons and 6 tons
29. Briefly describe the nut orientation requirements for bolting? (2 marks)
Nut facing towards the operating side
30. Briefly describe the problems with the handle locks currently used in our Eurochange products and how they can be improved? (5 points)
Lock box volume is large, occupies the space of the box variable, easy to touch the high and low voltage cabinets, compression of the thickness of the lock box, improve the installation of the lock rod, as far as possible, hidden to the door panel
31. Briefly describe the working principle of argon arc welding? (2 points)
The argon gas is sprayed on the welding surface to protect the weld from air oxidation,
32. What drawings and documents do you think you should output to do a project of Eurochange box body? (5 marks)
1. drawing catalog 2. chassis drawings 3. frame drawings 4. door panel drawings (there are generic drawings for door panels, which need to be illustrated)
5. partition drawings 6. mounting plate drawings for special units such as metering boxes
33. Explain the significance of the following notations? (5 marks)
14. There is an existing 4000A incoming switchgear cabinet with a width of 1400 and a hard busbar overhead feeder. Due to the eddy current effect of the current, it is necessary to provide anti-eddy current treatment at the inlet. Please provide the busbar specifications and explain how many layers of busbar and eddy current treatment material type and specification. (3 points)
15. Briefly describe the characteristics of armored metal-enclosed switchgear and box-type metal-enclosed switchgear. (6 points)
Switchgear made entirely of steel plate is metal-enclosed switchgear, such as XGN cabinets
Cabinet-type metal-enclosed switchgear requires a box to be provided outside the switchgear cabinet, such as box-type ring network cabinets
16. What are the principles of weld size symbols and data labeling? (5 points)
17.Carbon structural steel national standard grade? What is the grade of carbon structural steel commonly used in our company? (6 points)
Q235
18. The main busbar is TMY2 (120*10), and the lower lead busbar is TMY60*10. Write down the specification of the connecting bolts used, and what is the size of the connecting holes on the busbar and what is the distance between them? (3 points)
19.SPCC - indicates the general cold-rolled carbon steel sheet and strip, equivalent to the Chinese brand name, SPCC is the brand name. (4 points)
20. If you set out to design 1 European box variable, what information would you expect the electrical designer to give you? (5 points)
Primary drawings, floor plans, accessory requirements (number of fans, transformer mounting dimensions and requirements)
21. Disconnecting switch installation design considerations required? (5 points)
1, the disconnecting switch should be easy to operate, the disconnecting operation mechanism changes the operation flexibility
2, the disconnecting switch installation should be able to see the obvious disconnecting point on the operation side
3, the disconnecting switch static knife knife should be able to maintain good contact with a certain inrush of the current requirements
4, the disconnecting switch insulation to meet the requirements of the national standard
22. /p>
22. Please design your mind the best use, the most beautiful locking rod bracket CAXA in the air under the posting (10 points)
Description: 1, the installation method using the door to pull the nut, increase the pad level appropriate adjustment will be mounted on the top of the bracket
2, the bracket in the middle of the empty can be encircled by pulling the nut more than a portion of the
3, the use of cast iron Cast iron or high-strength nylon production