详情描述
Common fault analysis and solutions for the recycling and reuse of oil-immersed power transformers are as follows:
Section 1: Common Fault Analysis of Oil-Immersed Power Transformer Recycling and Reuse
Common faults in transformers during operation include issues with windings, bushings, tap changers, cores, oil tanks, and other accessories.
1. Winding fault
Main issues include inter-turn short circuits, winding ground faults, phase-to-phase short circuits, broken wires, and soldered joint failures.
2. Tubing Failure
Transformer bushing scaling can lead to pollution flashovers during heavy fog or light rain, causing single-phase grounding or inter-phase short circuits on the transformer's high-voltage side.
3. Severe leakage
Transformer severe oil leakage or continuous overflow from damaged spots, causing the oil level gauge to be invisible. In this case, the transformer should be immediately shut down for leak repair and oil refilling. Causes of transformer oil leakage include cracked welds or failed sealing components, severe vibration and external impact causing oil tank corrosion and damage, etc.
4. Tap Changer Fault
Common issues include poor contact or incorrect positioning of tap switches, melting and scorching of the contact surface, and discharge between contacts or at each tap.
5. Overvoltage-induced failures
When an operating transformer is struck by lightning, the potential of the lightning can cause external overvoltage of the transformer. When certain parameters of the power system change, internal overvoltage in the transformer can be induced due to electromagnetic oscillations. The transformer damage caused by these two types of overvoltage is mostly due to the breakdown of the main insulation of the windings, leading to transformer failure.
6. Core Fault
Faults in the iron core are mostly caused by the insulation damage of the through-bolts in the iron core column or the clamping bolts of the iron core.
7. Oil leakage phenomenon
Low oil level in transformer oil exposes the bushing leads and tap changers to air, significantly reducing insulation levels, thus making it prone to breakdown and discharge.
Section II: Common Fault Solutions for Oil-Immersed Power Transformer Recycling and Reuse
Weld joint oil leakage
Primarily, poor welding quality exists, with issues like cold welds, loose joints, pinholes, and sand holes in the welds. Oil-immersed transformers, due to the presence of flux and paint upon manufacture, reveal hidden problems upon operation. Additionally, electromagnetic vibration can cause welding cracks, leading to leaks. For leaks that have already occurred, locate the leak points without omission. For severe leak areas, use flat chisels or pointed punches to secure the leak points, then clean the treated surface. Currently, high polymer composite materials are often used for curing, which can achieve long-term leak control after curing.
2. Sealed part oil leakage
Poor sealing causes, usually the seal between the box rim and lid is achieved with oil-resistant rubber rods or rubber pads. Poorly handled joints can lead to oil leakage. Some use plastic straps to tie them, while others simply press the two ends together, but due to rolling during installation, the joints cannot be securely pressed and fail to seal, still resulting in oil leakage. Using Fushilan material for bonding can integrate the joints, greatly controlling the oil leakage; if convenient, the metal shell can also be bonded simultaneously to achieve the purpose of leakage treatment.
3. Leaking oil at flange connection
Flange surface is uneven, bolts are loose, incorrect installation technique leads to poor bolt tightness and oil leakage. After securing the loose bolts, apply sealing treatment to the flange and also address the bolts that may leak. This ensures complete remediation. Bolts must be tightened strictly according to the operational procedure.
4. Bolt or tube thread oil leakage
The transformers have rough machining and poor sealing at the factory, leading to oil leakage after a period of oil immersion. Sealing treatment is applied to the bolts using high polymer materials to address the leakage issue. Alternatively, the bolts (nuts) can be unscrewed, coated with Fushilan demolding agent on the surface, then re-coated with material before tightening. After curing, this method also achieves the leakage control.
5. Cast Iron Parts Oil Leak
Leakage oil is mainly caused by sand holes and cracks in cast iron parts. For crack leakage, drilling stress relief holes is a method to prevent extension. During treatment, depending on the crack condition, lead wire can be inserted into the leak point or the crack can be riveted shut with a hammer. Then, clean the leakage point thoroughly and seal it with appropriate material. Sand holes in casting can be sealed directly with material.
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