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NEWS CENTER
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Selection Principles of Welding Equipment
The selection of welding equipment is an important content in the formulation of welding technology, which involves many factors, but the following factors should be paid attention to.
1. Technical requirements for welded structures
The technical requirements of the welded structure include material characteristics, structural characteristics, dimensions, accuracy requirements and service conditions of the welded structure.
If the welding structure material is ordinary low carbon steel, the arc welding transformer can be used; if the welding structure requirements are high and low hydrogen electrode welding is required, the DC arc welding machine should be selected.
If it is heavy welding, you can use electroslag welding machine; if it is bar butt welding, you can choose cold press welding machine and resistance butt welding machine. For active metals or alloys, heat-resistant alloys and corrosion-resistant alloys, inert gas shielded welding machine, plasma arc welding machine and electron beam welding machine can be selected according to specific conditions.
Special welding machines can be used for welding structures with fixed structure and size in large quantities.
2. actual usage
Different welding equipments can weld the same welding piece, so we should choose the more suitable welding equipment according to the actual use.
If there is no overflow power source and gas source in field welding, arc welding generators such as diesel (steam) oil DC arc welding generators can only be selected as welding equipment.
For precise weldments that are not allowed to be reprocessed or heat treated after welding, an electron beam welding machine with concentrated energy, no filler metal, less heat affected zone and high precision should be selected.
3. economic benefits
When welding, the energy consumption of welding equipment is considerable. When choosing welding equipment, the welding equipment with less power consumption and high power factor should be selected as far as possible on the premise of meeting the technological requirements.
Tongwei Electric Haian Co., Ltd. is an enterprise specialized in welding automation complete sets of equipment, which integrates R&D, design, manufacture and sales. Our company has rich practical experience in various welding machines. We have designed and manufactured a number of high-quality and practical welding machines for various industries (power pipeline, medical pipeline, construction machinery, high-voltage switch, bellows welding, etc.).
2018-08-07
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Factors to be Considered in Selecting GIS Shell Material
(1) The steel with higher mechanical strength (e.g. boiler steel) should be selected as far as possible for GIS shell under operating impact; (2) the eddy current loss of bus barrel with three-phase common box is smaller than that of single-phase bus barrel; (3) the welding performance of steel shell is better than that of aluminum shell; (4) the air tightness of cast aluminum shell is more difficult to control; (5) the design and fabrication of aluminum shell Generally, the cost is about 20% higher than that of the same function steel (or tailor welded stainless steel) shell.
The dynamic sealing surface can be divided into rotating sealing surface and sliding sealing surface according to the action property. The rotating sealing surface is located on the transmission arm of the disconnector and the grounding knife gate. The rotating range of the sealing gasket on this kind of sealing surface is about 76 degrees. Three O-type sealing gaskets are used to strengthen the sealing. Seen from the situation of leakage detection in site installation, its sealing effect is satisfactory, but with the passage of time, the increase of operation times and the aging of rubber, the sealing condition of this kind of sealing surface needs to be noticed, especially the gasket on the disconnector or grounding knife gate with more operation times. The sliding sealing surface is located on the operating pull rod of the circuit breaker. Its sealing gasket section is "V" type, and the sealing surface is metal rod surface. It has four smooth "V" type sealing rings. The sealing is quite reliable and is not easy to leak.
There are many problems found when static sealing surface is installed and leaked on site. There are two main reasons for leakage of static sealing surface: defect of sealing gasket itself and bad combination of sealing surface.
2018-08-07
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The Concept of GIS and the Importance of Periodic Partial Discharge Detection
1.1 the concept of GIS
Sulfur hexafluoride enclosed combined electrical appliances, internationally known as "Gas lnsulated Switchgear" (GIS) for short, will be a transformer in a substation in addition to the primary equipment, including circuit breakers, disconnectors, grounding switches, voltage transformers, current transformers, arresters, buses, cable terminals. Through optimum design, the intake and outlet bushing can be organically combined into a whole.
1.2 the characteristics of GIS
Miniaturization: Because of the use of sulfur hexafluoride gas with excellent insulation performance as insulation and arc extinguishing medium, the volume of substation can be greatly reduced to achieve miniaturization.
2. High reliability: Because the live part is all sealed in inert SF6 gas, the reliability is greatly improved. In addition, it has excellent seismic performance.
3. Good safety: The live part is sealed in the grounded metal shell, so there is no electric shock danger. SF6 gas is non-combustible gas, so there is no fire risk.
4. Absolute external adverse effects: Because the charged part is enclosed by metal shell, shielding electromagnetic and static electricity, low noise, strong anti-radio interference ability.
5. Short installation period: Because of miniaturization, it can be assembled and tested in the factory, and then delivered to the site in the form of units or intervals. Therefore, it can shorten the construction period of site installation and improve the reliability.
6. Easy maintenance and long maintenance cycle: Because of its reasonable structure layout and advanced arc extinguishing system, the service life of the product is greatly improved, so the maintenance cycle is long, the maintenance workload is small, and because of the miniaturization, the ground is low, so the daily maintenance is convenient.
1.3 Significance of Partial Discharge Detection in GIS
With the development of urban power grid construction, the number of GIS substations is increasing.
- The internal space of GIS is very limited, the workfield strength is very high, and the insulation margin is relatively small.
Once insulation defects occur in GIS, it is very easy to cause equipment failure, resulting in a long blackout time and high maintenance costs.
- Several serious GIS accidents have occurred in China, and the view that GIS equipment is maintenance-free has not been accepted in the past.
GIGRE survey shows that more than 50% of GIS faults can be found in advance.
Monitoring partial discharge signal in GIS handover test and regular monitoring of GIS in operation are effective means to ensure safe operation.
2.1 Definition of Partial Discharge
Partial Discharge: Under the action of electric field, only part of the insulation between conductors is broken down (not between conductors with applied voltage).
Characteristic: Partial discharge is a kind of pulse discharge, which can produce a series of physical phenomena and chemical changes such as light, sound, electrical and mechanical vibration in the internal and surrounding space of power equipment. This provides a detection signal for monitoring the internal insulation status of power equipment.
Although the magnitude of these discharges is usually small, they can lead to gradual deterioration and eventual breakdown. Therefore, the existence of these discharges needs to be detected through non-destructive testing.
2.2 Causes of Partial Discharge
Cause: It is caused by partial electric field distortion and local electric field concentration, which leads to gas discharge or breakdown in partial range of insulating medium. It may occur at the edge of the conductor, or at the surface or inside of the insulator.
Several Typical Defects in GIS
Because of the pinpoint protrusion in the insulator or on the high voltage conductor, the electric field is not uniform, the dielectric is not uniform, there are bubbles and magazines and other reasons, the electric field strength in the local area of the insulator reaches the breakdown field strength.
2018-08-07
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