What caused the failure of transformer bushing
Writer： Hengfeng you electric Time：2023-04-21 views：times
This paper mainly analyzes the common faults of transformer bushing and the main causes of the faults. Let's have a look.
. Main insulation and turn to turn insulation failure of winding
1.The main insulation and turn to turn insulation of transformer windings are prone to failure. The main reasons are: due to long-term overload operation, poor heat dissipation conditions, or long service life, the insulation of transformer winding is aging and brittle, and the electrical strength is greatly reduced; The transformer has been impacted by short circuit for many times, which causes the winding to deform under force and hides insulation defects. Once there is voltage fluctuation, the insulation may be broken down; Water enters the transformer oil, which greatly reduces the insulation strength and cannot withstand the allowable voltage, resulting in insulation breakdown; At the reinforced section of the high-voltage winding or the low-voltage winding, the oil duct is blocked due to the expansion of the turnkey insulation, which affects the heat dissipation, so that the winding insulation is aged due to overheating, resulting in breakdown and short circuit; Due to imperfect lightning protection facilities, insulation breakdown occurs under the action of atmospheric overvoltage.
2. Lead insulation failure
The transformer lead is led out through the inner cavity of the transformer bushing and connected to the external circuit. The lead is supported and insulated by the bushing. Due to the loose sealing of the upper end cap (general cap) of the bushing, water enters, the main insulation of the lead is damaged by moisture, or the lead in the oil tank is exposed to the air due to the serious oil shortage of the transformer, resulting in internal flashover, which will cause faults at the lead.
3. Core insulation failure
The iron core of the transformer is made of silicon steel sheets, and there is an insulating paint film between the silicon steel sheets. Due to the poor fastening of silicon steel sheet, the paint film is damaged and eddy current is generated, resulting in local overheating. Similarly, if the insulation of the core clamping screws, pressure iron and other parts is damaged, overheating will also occur. In addition, if there is iron filings or welding slag left in the transformer, making the iron core grounded at two or more points will cause iron core failure.
4. Flashover and explosion of transformer bushing
Capacitor bushing is generally used on the high-voltage side of transformer (110kV and above), which has trachoma or crack due to poor porcelain quality; The capacitor core has defects in manufacturing, and there is free discharge inside; The casing is not well sealed and there is oil leakage; Serious casing fouling may cause flashover and explosion.
5. Tap changer failure
Transformer tap changer is one of the common fault parts of transformer. Tap changer is divided into no-load voltage regulation and on load voltage regulation. The causes of common faults are:
1) Off load tap changer: due to long-term pressure contact, there will be insufficient spring pressure and uneven roller pressure, which will reduce the effective contact area of the connecting part of the tap changer, and the silver plating of the contact part at the connection will be worn and fall off, causing the tap changer to be heated and damaged during operation; The tap changer has poor contact, poor connection and welding of outgoing lines, and cannot withstand the impact of short-circuit current, causing the tap changer to be burnt out by short-circuit current and failure; Due to poor management, the tap changer accident was caused by disordered tap changer or careless work.
2) On load tap changer: for transformers with on load tap changer, the oil tank of the tap changer and the oil tank of the transformer are generally not connected to each other. If the oil tank of the tap changer is seriously short of oil, a short circuit fault will occur during the switching of the tap changer, causing the tap changer to burn out.
During casing overhaul, incomplete vacuum pumping caused residual air between screens. After operation, partial discharge occurred under the action of high electric field, and even led to insulation breakdown, causing accidents.
The above is about what caused the transformer bushing failure. If you want to know more about the transformer, you can contact us. Hengfengyou Electric will provide you with the best electrical product solutions. 【WhatsApp：+86158 5325 2696（Jack） +86158 5326 5269（Alisa） info@hengfengyou.com https://www.hengfengyou.com 】
