GB3906 and GB7251, the book can see "set of electrical switchgear design" (upper and lower). The secondary schematic diagram can refer to the product drawings produced by the company and the schematic diagram of the circuit breaker manufacturer. For you, you can see "How to read the secondary electrical schematic diagram" (books and drawings can be borrowed from your data room), electrical drawings Designed by the design unit, you must design and change the design unit to sign and seal, because you are not qualified. Your role is to turn design requirements into products that meet dimensional, functional, temperature rise and technical performance requirements.
Experience of practical technical articles voltage switchgear 35KV and 10KV high-voltage switchgear designed to explore the 35kV, l0kV High Voltage Switchgear manufacture the design in protection class, insulation distance, creepage distances, five anti-interlock function, temperature, grounding problem .
At present, the rapid growth of power installation has promoted the rapid expansion of the high-voltage switch market, especially the 35KV, l0kV medium voltage switchgear is widely used in power systems. Therefore, the author of this article focuses on the design of the medium voltage switchgear to write his own experience, write a glimpse, for peer reference only, and please correct me.
Some experience
1About the structural requirements of the cabinet. The housing of all switchgear cabinets must be metal casing and have certain mechanical strength. The circuit breaker room, busbar room and cable room in the cabinet are equipped with pressure release channels. The secondary line is beautifully laid and easy to inspect. The mounting beams of all primary electrical components in the switchgear must be metallic and should be reliably grounded.
2 Requirements regarding the degree of protection. 10KV, 35KV high-voltage switchgear is a high-voltage live device. In order to prevent the human body from approaching the high-voltage live part of the high-voltage switchgear and touching the moving part, when designing the switchgear, we must consider the requirements of the cabinet protection level. For 10KV fixed switchgear, GG-1A-10, XGN2-10, must meet the requirements of protection class IP3X, remove type
JYN and KYN series such as JYN2-10, KYN1-10, KYN11-10, KYN28-10, etc. must meet the requirements of protection class IP4X, for 35KV fixed switchgear such as XGN17-40.5, etc. must meet the requirements of protection class IP3X, remove Cabinets such as GBC-40.5, JYN-40.5 must meet the requirements of protection class IP3X, removable KYN series switchgear such as KYN10-40.5, KYN61-40.5 must meet the requirements of protection class IP4X.
Of course, when designing the switchgear, we can pursue a higher level of protection, but the problem is that as the degree of protection increases, the production cost increases accordingly, and the heat dissipation conditions become worse, so we cannot blindly pursue a high degree of protection, generally with IP3X and IP4X is suitable.
3 insulation distance. Because 10Kv, 35KV switchgear is used to distribute three-phase AC power, so a certain insulation distance must be guaranteed between the phase and the opposite ground, otherwise it will cause short circuit and cause harm to the whole power system. Therefore, we must meet the requirements of insulation distance when designing the switchgear: if air is used as the insulating medium and the altitude is 1000m, for 10kV relative, and the phase and phase satisfy the ratio of 125MM, 35kV, and phase If the altitude is more than or equal to 300mm, the insulation distance shall be corrected according to the requirements of GB3906. However, sometimes due to the limitations of the power distribution room, the dimensions of the switchgear we made often cannot meet the insulation distance requirements, so the following methods can be used to solve the insulation problem:
First, in the metal-enclosed high-voltage switchgear, non-metallic insulating spacers are used to strengthen the phase-to-phase or relative insulation to reduce the requirement for insulation distance. However, it must be noted that the bare conductor between 10kV and the insulating plate should be kept at least 30m, and the bare conductor between 4kkv and the insulating plate should be kept at least 60mm. The disadvantage of this method is that the insulating spacer is greatly affected by the use environment, and there is a problem of insulation aging.
Secondly, the heat-shrinkable sleeve is used to heat-shrink the high-voltage live conductor. In practice, the insulation distance of 10KV should be no less than 100mm, and the insulation distance of 35kV should be no less than 200mm. The disadvantage is that the heat shrinkable sleeve also has the problem of insulation aging. The dielectric strength will decrease over time.
In summary, air insulation is used as much as possible to meet the insulation requirements in the case of design approval.
4 creepage distance. Power system is the core system of the power supply department, can not have the slightest sloppy, users often pursue high reliability, in the creepage distance, we have very strict requirements for our manufacturers, in practice we have to meet the following conditions : The ratio of the creepage distance to the rated voltage of the external insulation creepage of the components and their supporting insulating parts (pure porcelain and organic insulating parts) in the high-voltage switchgear is higher than that of the high-voltage electrical components. 18mm/kV, 20mm/kV for organic insulation. In order to meet the above requirements, the measures we have taken are: requiring the supporting manufacturers to increase the umbrella group to increase the insulator, and in the place where the switchgear is used in a humid environment, in order to prevent condensation, the cable room in the switchgear, the circuit breaker room Add a heater with a temperature control unit.
5 five anti-interlock function. Whether the switchgear can operate reliably and safely, the five-proof interlock is very important. The national standard has clear requirements for the five-proof interlock of the switchgear. Therefore, we must observe the following principles when designing and manufacturing the switchgear: high-voltage switchgear It has the function of preventing accidental pull-in of the circuit breaker, preventing the load- disconnecting isolating switch , preventing the grounding knife gate (or grounding wire) from transmitting power, preventing the grounding of the grounding knife gate (or hanging the grounding wire), preventing the mis-entry of the dot interval, etc. Kind of anti-error measures. At present, in order to realize the five-proof function, various manufacturers of various types of switchgear, such as GG-1A, XGN2, JYN, KYN cabinet mechanical interlocking production have their own characteristics, and complete functions. The purpose is to prevent misuse of field workers.
6 temperature rise. In the power system switchgear, all electrical components have different degrees of heat during normal operation. Therefore, in GB3906, the temperature rise of each component of the switchgear cabinet is clearly defined, that is, the temperature rise of each component in the cabinet must not exceed The corresponding standard of the component shall not exceed 20K for the accessible outer casing and cover. The temperature rise of the main circuit shall comply with the provisions of GB763 "Fever of high-voltage electrical equipment during long-term operation" at rated current and frequency. . In order to meet the temperature rise limit conditions, the following points must be made: manufacturing process to strengthen the switchgear cabinet (such as silver plating on the busbar lap joint, hot tin); avoid eddy current phenomenon in design or use non-magnetic material; The current increases the air cooling device.
7 Grounding of high-voltage switchgear: All electrical components in the switchgear are charged. In order to ensure the safety of personnel during maintenance, all electrical components must be grounded safely and reliably. When designing and manufacturing the switchgear, the following points must be made: a dedicated grounding busbar is provided along the width direction of all switchgear cabinets. The grounding busbar is connected to the grounding grid; the grounding of each electrical component in the switchgear must be connected to a dedicated grounding busbar. Connected.
Conclusion
With the development of China's electric power industry, the design of the switchgear is endless. We need to constantly learn the national standards and learn from the advanced experience of large foreign companies to contribute to the development of China's electric power industry.
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