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A simple oil-immersed transformer is used to change the control line. It is equivalent to a switch, and the other is to increase the role of the current. In fact, the role of the oil-immersed transformer and the function of the general oil-immersed transformer is consistent, mainly playing the role of "switch" dry transformer.

① Protection control switch: The control switch only controls the on-off of the oil-immersed transformer coil, and the force generated by the oil-immersed transformer coil is used to break the circuit controlled by the control switch. After the oil immersed transformer is added, the control switch only flows through a small oil immersed transformer coil current, so the switch is not easy to damage and the service life is extended.

2 Automatic control: some oil-immersed transformer coil current is controlled by a certain working voltage in the circuit, when the controlled voltage in the circuit reaches the set oil-immersed transformer action voltage, the oil-immersed transformer contact changes the working state, so as to achieve automatic control. For example, the starter drive protection oil-immersed transformer can be generated after the engine starts, the generator generates electricity, and the midpoint voltage of the generator makes the oil-immersed transformer contact open and automatically disconnect the circuit of the starter switch.

(1) The function of the transformer to prevent stray live spacing makes the opening and closing of the transformer cabinet door and the grounding switch have a locking relationship, that is, only after closing the grounding switch can the transformer door be opened, and the accident has exposed the imperfect problem of the "five prevention" mechanical locking device of the old model transformer.

(2) Transformer electrical inspection problem is a problem that has plagued power safety production for many years, and the mechanical "five defenses" locking device of the fully enclosed "five defenses" transformer is now promoted, which cannot meet the requirements of the safety regulations "transformer manufacturers prior electricity and rear grounding wire". Because when performing power outage work, it must be verified that the equipment has no voltage before closing the ground switch. However, the closed transformer is in a fully closed state, and according to the normal operation method, the portable electroscope cannot be used to test the equipment, so there is a way to forcibly unlock the transformer cabinet door to test the electricity.

(3) A large number of on-line display devices using neon lights as display elements are used on transformers. After a long period of operation, it is found that the blindness rate is high and a large number of neon bubbles are damaged. In order to make up for the defect, a neon light running/off switch is installed on the live display device, which is normally off, so that the whole live display device is temporarily out of operation. This processing method loses the role of the live display device as monitoring whether the line side is live or not.

(4) Low brightness of neon lamps, especially in bright environments, the brightness is washed, and the display is poor.

(5) The old live display device with mandatory transformer locking, the locking principle is too simple, only the A.B.C three-phase sensor output signals are directly combined after half wave rectification, to control the locking circuit. In this way, when the system has the abnormal situation of single-phase grounding or phase absence, the device can not be reliably blocked due to the drift of the blocking control voltage, and the on-line grounding switch accident will occur.

(6) Most of the neon type live display devices installed in the project adopt plastic shell and are installed in the equipment spacing. Once the transformer is short circuiting and releasing arc during operation, the high-temperature arc may melt the plastic shell of the device and injure the operation or maintenance personnel.