Transformer Coil Insulation Casting to Prevent Voids and Partial Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing medium voltage instrument transformers often result in partial discharges due to voids and cracks, which are difficult to prevent with multiple casting steps and inadequate insulation materials.
Innovation Solution
A method involving a single casting step using insulation materials with encapsulated chemical initiators, where the temperature is increased to reduce viscosity and initiate cross-linking of epoxy or silicone resins, ensuring precise impregnation and preventing partial discharges, while also using poly(ethylene terephthalate) non-woven porous fabric or fiberglass for improved insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple casting steps are used to produce transformer insulation, then the insulation quality can be improved, but the production process becomes more complex and time-consuming
Solution Approach 1:
The patent combines multiple casting steps into a single casting operation by using a two-component epoxy resin system where Component A (resin) and Component B (hardener) are mixed and applied simultaneously. This merging of steps simplifies the production process while maintaining insulation quality through the chemical cross-linking mechanism that occurs during a single curing cycle.
Solution Approach 2:
The patent applies insulation material to the coil windings before the final curing step, ensuring proper positioning and distribution of the insulation layers. The two-component resin system is prepared and applied in advance, allowing the insulation structure to be established before cross-linking begins, which prevents void formation and ensures uniform insulation quality.
2Strength
If the impregnation material viscosity is high during casting, then the material maintains structural integrity, but the impregnation precision and penetration into insulation material is reduced
Solution Approach 1:
The patent controls the viscosity of the two-component epoxy resin system by adjusting the mixing ratio of Component A and Component B, and by controlling the temperature during application. The resin is applied at a temperature and viscosity that allows optimal penetration into the insulation material, then curing begins as the cross-linking reaction progresses, maintaining structural integrity while ensuring precise impregnation.
Solution Approach 2:
The patent employs a time-dependent viscosity change during the casting process. Initially, the resin mixture has lower viscosity to facilitate penetration and impregnation of the insulation material. As the cross-linking reaction progresses, the viscosity increases naturally, providing structural integrity. This periodic change in viscosity ensures both precise impregnation and structural strength.
3Duration of action of stationary object
If cross-linking is initiated immediately upon mixing the impregnation material, then the curing process begins, but the viscosity reduction and impregnation precision are compromised
Solution Approach 1:
The patent applies the two-component epoxy resin mixture to the insulation material first, allowing it to penetrate and impregnate the material while the viscosity is still low. Only after the impregnation is complete does the cross-linking process begin to proceed, ensuring that the resin has already distributed itself properly throughout the insulation structure before curing locks the structure in place.
Solution Approach 2:
The patent maintains a continuous process where the two-component resin is mixed and applied, followed immediately by the initiation of cross-linking without interruption. This continuous action ensures that the resin remains in a workable state during application and transitions smoothly into curing, maintaining both impregnation precision and curing efficiency throughout the process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method simplifies the transformer production process, reduces the occurrence of cracks and voids, enhances mechanical and dielectric properties, and extends the transformer's lifespan by ensuring a void-free and crack-free structure, thus improving its reliability and durability.
Implementation Method 1
a temperature of the active part of the transformer is increased to release chemical initiator from capsules to allow cross-linking
Implementation Method 2
cross-linking is carried out until curing of the impregnation material
Implementation Method 3
a temperature of the active part of the transformer is increased to reduce the viscosity of the impregnation material
Data Source
Figure 1
Figure 2~3
AI summary
A method for producing a transformer (1), in particular a medium voltage instrument transformer, comprising the steps of winding (101) a coil of a transformer (1) with an insulation material (2) comprising capsules (3) with a chemical initiator (4), preparing (102) an active part of the transformer (1), wherein the active part comprises the wound coil, casting (103) the active part of the transformer (1) with an impregnation material (7), wherein the impregnation material (7) is an epoxy resin or a silicone; increasing (105) a temperature of the active part of the transformer (1) to release chemical initiator (4) from the capsules (3) to allow cross-linking, while the cross-linking is carried out until curing of the impregnation material (7); and cooling (106) the transformer (1). Further, after the step of casting (103) the active part of the transformer (1) and before the step of increasing (105) the temperature of said active part to allow cross-linking, a temperature of the active part of the transformer (1) is increased (104) to reduce the viscosity of the impregnation material (7), and said cross-linking is initiated by a temperature higher than the activation temperature of the chemical initiator (4) to release the chemical initiator (4) from the capsules (3). Furthermore, the insulation material (2) is poly(ethylene terephthalate) non-woven porous fabric, polypropylene non-woven fabric, fiberglass or crepe paper. The insulation material (2) has distributed on its surface the chemical initiator (4) encapsulated in capsules (3). The capsules (3) are adapted to release the chemical initiator (4) in a temperature higher than an activation temperature of the chemical initiator (4).