When the iron core and coil reach a certain temperature, the heat absorbed by the coil has decreased significantly, and a lot of heat energy is absorbed by the iron core with large heat capacity. Now turn on the vacuum pump to make the tank have a certain degree of vacuum, and the water on the surface and shallow layer begins to transpiration. Continuously improve the vacuum, so that part of the transpiration water is drawn out of the tank, and the other part participates in heat exchange as a heat transfer medium. As some heat is taken away by water transpiration and the pressure in the tank drops, the body temperature will drop. At this time, there should be enough heat to supplement the heat loss and keep the coil in a new heat balance to maintain a normal temperature rise. In order to make the drying tank not only have good heat transfer conditions, but also have ideal negative pressure transpiration effect; According to the physical characteristics of water under thermal vacuum, the pressure in the tank has an alternating process (suction pressure maintaining aeration pressure maintaining suction time).

Electronic control system

1) The power supply of the vacuum drying equipment with voltage transformation method shall be inserted and arranged for the special purpose of the equipment, and it is prohibited to connect any electrical equipment irrelevant to the equipment.

2) Do not connect other equipment or lines to the control cabinet or components of the equipment.

3) Do not place any objects in the control cabinet to avoid fire, short circuit, electric shock and other hazards.

4) Prevent non professionals from opening the door of the control cabinet during the operation of the equipment to avoid electric shock.

5) Stop changing the setting value of each time relay in the control cabinet.

If it is found that the heating ammeter still shows the value when the program does not command the system to heat, check whether the contactor is damaged immediately. If the contactor is damaged, replace it immediately; If one or two ammeters are found to have no value during heating, check whether the fuse is damaged immediately. If the fuse is damaged, replace it in time.

The heater terminal is located at the top of the heat transfer oil tank. It is forbidden to place objects. If it is necessary to move the cover plate, the heating cabinet is in a power-off state.

Check the operation condition of the heat transfer oil system frequently. The pressure gauge 910 should not be less than 0.2MPa to avoid the inactivity of the heat transfer oil in the oil tank caused by the idling or poor circulation of the oil pump and the overheating of the oil tank.

All manual valves of heat transfer oil system (except blowdown valve) shall be in normally open condition. It is forbidden to change the installation orientation and height of the thermal resistor on the heat transfer oil heating box to avoid temperature measurement deviation. It is prohibited to modify the set value of the temperature control meter on the control cabinet without permission, so as to avoid the failure of temperature measurement and protection functions or misoperation.

Note: if the tank needs to be in atmospheric condition during heating, turn over valve 203 before heating, and the tank door shall not be clamped. Avoid damage to the tank caused by pressure rise in the tank.

Check the condition of fuses, contactors and heater wires frequently. In case of damage or looseness, replace and fasten them in time.

In the initial stage of vacuum pumping, the vacuum degree shall be improved on average to meet the requirements of vacuum mechanical strength of oil tank. 66-110kv transformer shall reach the above vacuum requirements within at least 1 hour.

When the transformer body is considered to have traces of moisture due to long exposure time or other reasons, it is necessary to connect the long-term vacuum degree after leisure. The connection time depends on the moisture level, generally up to 8-24 hours, so as to facilitate the evaporation of water.

Information origin:

When filling oil, the air in the pipeline must be discharged. When the oil filling valve is full of oil, start to open the oil filling valve for oil filling. The oil filling shall be from bottom to top, and the oil filling speed shall be 2-3T / h, not more than 6t / h, so as to prevent the oil flow from being charged. When the oil level is 100-200mm from the top of the tank, stop oil injection and continuously connect the vacuum. The vacuum of 110kV transformer should be connected for more than 2 hours and 220kV transformer for more than 4 hours.