Transformer is responsible for power system voltage conversion, power transmission and distribution of electrical equipment terminal. If the high and low voltage side of the Transformer company casing defects or failure, will directly endanger the safe operation of the transformer and power supply can be *. For the low down tube, because of its simple structure, needs an overhaul time is short, relatively easy to maintain. The overwhelming casing for high (oil-paper capacitor bushing), because of its complex structure, long maintenance cycle, maintenance more difficult. Therefore, the oil-paper capacitor bushing timely repair and maintenance, reduce and eliminate accidents casing is very important.
Casing failures of the past through the analysis, summarized in the following main reasons:
Sewage pipe surface will absorb moisture wins, the insulation resistance is lowered, the consequences are prone to flash, resulting in tripping. Meanwhile, the flashover will damage the casing surface. Dirt to absorb moisture, the conductivity increase, not only caused by the surface flashover may also be due to leakage current increases, the insulating ceramic tube heat and cause damage, or even breakdown.
As the pad casing seal failure, oil-paper capacitor bushing seal the top of bad, cause water to insulation breakdown, poor sealing the casing lower permeability, resulting in decreased oil.
Casing seal failure for two main reasons: First, lack of experience as maintenance personnel, tightening force is not enough; two super-cycle is due to the quality of running or cushion defects. Others, such as, ground small casing failure, screen tubes to produce sets of floating potential, the occurrence of partial discharge; casing structure is irrational in itself, and there flaws. For example, some substation main transformer will bother, because the use of lead solder with lead soldering head, 220 kV tube voltage of phase A guide for the aluminum casing, head of copper wire, aluminum rain phase, the copper connection resulting in increased contact resistance of aluminum, so that rain rate and the first conductive sintered, conductive leads and the first boil.
In addition, the battalion oil standard tube dirty, can not see the oil level in the pre-test sample to form an annual loss of oil.
Man-made causes such as. Casing overhaul, vacuum is not complete, so that the air remaining between the screen, running at high electric field, the occurrence of partial discharge, insulation and even lead to breakdown, causing the accident. Again, the battalion head structure installation unreasonable. For example, thread and rain cap stone I do not close contacts; rain hat and nose close connection; wiring terminal board nose and poor contact, resulting in increased contact resistance, heat sintered wire connector.
Run through the analysis of transformer bushing, not difficult to find defects in the formation of two ways: First, there are weaknesses in the design casing itself; second is the human factor is the casing installation and maintenance personnel in operations caused. Analysis of casing failures in the main, we can care, and transportation. Installation, repair maintenance, etc. to develop appropriate countermeasures.
First, the transport should pay attention to. Lifting speed should be slow to avoid the collision other object; vertical hoists should be used when the flange of the lug, and the upper casing with a rope lashing to prevent dumping; careful not to lift the casing porcelain skirts to prevent the wire rope and porcelain sets collide damage; put up the casing, should avoid any part of the floor; casing lying place and transport, should be placed on a dedicated box. Two support points should be installed at the flange, the upper parts of non-porcelain skirt set that support, the tail should be set up anchor, and with a soft material to anchor the whole good. Tube should be fixed in the box to avoid damage in transit traverse.
Secondly, the installation should pay attention to. The casing will be placed directly on the bracket, remove the rear cover are pressed.
Finally, related work should pay attention to. Table pre-trial investigation officer, disconnect the end of the small screen tube leads should be granted to prevent the guide rod turning off the ground or bow Fu.
Oil samples for casing failure. With acetylene gas and other defects. Measures taken are: the New casing to rigorous testing, to avoid human-induced failures.
Bad for the casing seal, or have access to oil leakage phenomenon. Measures are: by replacing the pads remain sealed, so that no leakage casing.
Casing head for defects such as overheating. Specific measures may change the transition to a copper-aluminum-silver-copper contact, thus reducing oxidation. So as to prevent its overheating.
Frequency Transformer in operation, due to various reasons, the oil-paper capacitor bushing sometimes malfunction or defect.