Power transformer installation procedure
1. Transformer unloading and seating
After the transformer foundation acceptance and handover, the surrounding construction site will be leveled and compacted, and the unloading platform and hauling track will be arranged.
The transformer should be inspected again before the main transformer is hauled to the installation point.
Check the high and low pressure side of the transformer to determine the direction of the unloading.
The main transformer unloading and consignment plan refers to the third section, "Large hoisting and transportation".
Once the transformer is in place, it must be reliably grounded before any other work begins.
2. Body inspection
There are two ways to choose from the inspection of the hood and the internal inspection of the body. Which method is adopted depends on the actual situation of the site and the requirements of the manufacturer and the owner.
Regardless of the method used, it should be chosen in good weather and minimize the exposure time of the body in the air. It should be satisfied that the ambient air temperature is not lower than 0 °C, and the temperature of the body is not lower than the ambient air temperature; When the temperature of the body is lower than the ambient air temperature, the body should be heated by the hot oil circulation method to make the temperature higher than the ambient air temperature; second, the relative humidity of the air is not more than 75; 3. The surrounding area should be clean and dustproof. Three conditions.
3. Hanging cover inspection method
When the bell is hoisted, it should be balanced and hoisted. The angle between the sling and the plumb line should not be greater than 30 degrees. The lifting process should be slow. It is strictly forbidden to collide with the box wall.
Nitrogen-loaded transformers must be exposed to air for more than 15 minutes before the nitrogen can be diffused.
4. Enter the internal inspection mode of the body
Before the inspection of the nitrogen-transported transformer body, the nitrogen is exhausted by means of oil-filling and nitrogen-discharging. Before draining the nitrogen, the residual oil in the fuel tank must be drained. The oil injected into the fuel tank must be qualified insulating oil. The oil level should be higher than 100mm above the iron core. After standing for 12h, the oil can be drained for internal inspection.
5. Attachment installation
High-voltage bushing installation: first remove the terminal block and the conductive head, and use a nylon rope with a length of 20m and a diameter of 8~10mm to penetrate into the casing. The upper end is pulled by the staff through the pulley hanging on the hook, and the casing is lifted by the crane. Slowly hoist and move to the top of the riser. The other end of the rope is connected to the lead connector of the transformer with a lifting eye screw. The casing is lifted into position, and the lead joint is lifted beyond the top of the casing. The tube is securely fastened. Installation of other accessories: After the installation of high and low casings is completed, the manhole door can be sealed to install other accessories such as oil conservator and cooler.
6. Vacuum oiling
After the attachment is basically completed, you can start vacuuming and prepare for oiling.
When vacuuming, the accessories that cannot withstand mechanical strength should be isolated from the fuel tank according to the manufacturer's requirements.
The deformation of the tank wall should be closely monitored when vacuuming.
When vacuuming, first draw the fuel tank into 0.02Mpa, and then increase the average evenly by 0.0067Mpa to 0.101Mpa (or manufacturer's requirement), then start oiling. The oil should be injected from the lower butterfly valve. The injected oil should be a qualified transformer insulating oil, and the temperature of the oil must be higher than the temperature of the body.
The oil filling should be stable and the speed should not exceed 100L/min.
The vacuum should be maintained throughout the filling process. After the oil filling is finished, the vacuum should be kept for more than 4 hours.
7. Hot oil circulation
In order to completely remove moisture and residual gas, the oil must be circulated after the oil is injected.
The hot oil circulation can be carried out under full oil condition after vacuum filling to the rated oil level of the oil conservator, or when the oil is injected to the top of the body cover 200mm. It is recommended to perform hot oil circulation in the full oil state.
The technical requirements for hot oil circulation are determined according to the manufacturer's instructions.
When hot oil is circulated, it should be deflated regularly.
Power transformer installation precautions 11
1. Reasonably choose the installation location of the distribution transformer
The installation of distribution transformers must meet the requirements of the user's voltage, and try to avoid installing the distribution transformers in the barren hills, which are vulnerable to lightning strikes and away from the residential areas. This is not convenient for the maintenance personnel to maintain regularly, and it is not convenient for staff management. .
2. Reasonably choose the capacity of the distribution transformer
It is also very important to choose the capacity of the distribution transformer reasonably. It can neither cause the overload of the distribution transformer to burn out, nor can it cause the waste of the big horse type. According to the user load situation, the capacity should be counted and the distribution transformer capacity should be reasonably selected. Such as: a 100kV·A distribution transformer with a power factor of 0.85, it can carry a load of 85kW.
3. Strengthen the measurement of power load
During the peak period of power load, the load of each distribution transformer should be strengthened. If necessary, increase the number of measurements. The distribution transformer with unbalanced three-phase current should be adjusted in time to prevent the neutral current from being too large and easy to blow the lead. Causes the user equipment to burn out.
4. Avoid installing a low-voltage metering box on the distribution transformer.
The low-voltage metering box installed on the distribution transformer station area of ​​the remote mountainous area should be gradually removed, and it should be changed to indoor installation as much as possible. For example, in the past few years when the bureau destroyed the non-powered township, in order to facilitate management and prevent power loss, low-voltage mountain areas were installed. Due to long-term operation, the metering box glass is damaged or the low-voltage pile head of the distribution transformer cannot be replaced in time, causing damage to the distribution transformer caused by burning the electric energy meter due to rain or the like.
5, reasonable allocation of distribution transformer high and low voltage fuse melt
The distribution of the high and low voltage fuses of the distribution transformer is unreasonable, which is likely to cause serious overload of the distribution transformer and burn out the distribution transformer. The high and low pressure melt configuration shall be followed by: a fuse body with a capacity of 100 kV·A or less and a fuse body with a rated current of 2.0 to 3.0 times; and a transformer with a capacity of 100 kV·A or more with a melt of 1.5 to 2.0 times the rated current; The low-voltage side fuse should be configured slightly larger than the rated current.
6, should not adjust the tap changer privately
Due to the difference in power load between winter and summer, the voltage level is slightly different. In order to meet the voltage demand, some rural electricians randomly adjust the tap changer without performing related tests, causing the tap changer to be out of position, causing phase-to-phase short-circuit and burnout. Electric transformer.
7, distribution transformer high and low installed insulation cover
In order to prevent natural disasters and external damage, if necessary, install high and low voltage insulation covers for the narrow roads and forest protection areas to prevent the low voltage short circuit from burning the transformer on the distribution transformer.
8. The arrester should be installed on the high and low voltage sides of the distribution transformer.
Lightning arresters should be installed on the distribution transformers in the multi-mine area. If the quality of the arrester is unqualified or failed in time, it will be easily attacked by lightning. During the thunderstorm season, the arrester should be sent to the repair department for testing and timely installation. It is forbidden to use unqualified products.
9. Regularly measure the grounding resistance of the distribution transformer
After long-term operation of the distribution transformer (especially the grounding lead is replaced by aluminum wire), severe oxidation occurs, the grounding resistance increases, and the grounding body is corroded and broken, causing the neutral point potential to shift. When lightning strikes or overvoltages It is easy to cause an accident. According to the regulations, the grounding device should meet: the grounding resistance of the distribution transformer below 100kV·A is not more than 10Ω, and the grounding resistance of the distribution transformer above 100kV·A is not more than 4Ω.
10. Strengthen daily management
Regular inspections of the line, cutting down trees, preventing the branches from hitting the wires and causing a low voltage short circuit to burn the distribution transformer. The lack of daily management of the distribution transformer makes the transformer run out of oil for a long time. The end of the respirator is installed or the silica gel is not replaced in time, so that the distribution transformer is flooded and easily caused accidents. There are quality problems in the distribution transformer itself. Because the installation location of the distribution transformer is far away, some construction personnel arbitrarily put the untested distribution transformer into operation, temporarily using electricity, and burning the transformer.
11, regularly check the distribution transformer low voltage lead
It is strictly forbidden to use the wire itself to make the wire nose directly to the low-voltage pile head of the distribution transformer. It is necessary to regularly check and strengthen the joint between the lead wire and the distribution transformer pile head to prevent the low-voltage pile head of the distribution transformer from being burnt due to loosening.
In order to make the distribution transformer operate safely for a long time and have fewer failures, as the operation management personnel, it is necessary to do diligent inspection, diligent maintenance, and diligent measurement, timely find problems and deal with them in time to avoid the expansion of the fault and burn out the distribution transformer.
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