Silicone Rubber Composition for HVDC Cable Joint Stress Grading
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Solution Overview
Problem
High voltage direct current (HVDC) applications require insulators with specific mechanical and electrical properties that traditional insulating materials cannot provide, as they fail under extreme electrical stress due to differences in electrical stress conditions between AC and DC, leading to spontaneous discharge and material failure.
Innovation Solution
A silicone composition with a balanced mechanical and electrical resistivity is developed, optimized with a specific amount of dielectric active compounds to minimize electrical stress, featuring a low temperature coefficient of resistivity and high elongation, suitable for cable joints and field grading assemblies, using a combination of polyorganopolysiloxanes, crosslinkers, fillers, and curing catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure silicone rubber with high volume resistivity (10^16-10^18 Ohm*cm) is used for HVDC cable joints, then electrical insulation performance is improved, but electrical stress distribution becomes nearly impossible due to extreme electrical stress
Solution Approach 1:
The patent changes the electrical parameters of silicone rubber by adding dielectric active fillers (TiO2, SiO2, Al2O3) to adjust volume resistivity from the original 10^16-10^18 Ohm*cm to an optimized range of 10^12-10^14 Ohm*cm. This parameter modification enables better electrical stress distribution while maintaining adequate insulation performance for HVDC applications.
Solution Approach 2:
The patent creates a composite material by combining silicone rubber base polymer with dielectric active fillers (TiO2, SiO2, Al2O3) and conventional fillers (carbon black, zinc oxide). This composite structure provides both the mechanical properties of silicone rubber and the electrical stress management capabilities of the dielectric fillers, resolving the contradiction between insulation performance and stress distribution.
2Object-affected harmful factors
If non-linear resistivity field gradient insulators are used for HVDC applications, then electrical stress distribution is improved, but handling and application becomes difficult and cost increases
Solution Approach 1:
The patent applies local quality by distributing dielectric active fillers throughout the silicone rubber matrix to create localized regions of different electrical properties. This provides field gradient effects for stress distribution while maintaining uniform material composition that is easy to handle and apply, unlike complex multi-layer non-linear resistivity structures.
3Object-affected harmful factors
If higher concentration of conductive or semi-conductive fillers (40 wt.% and more) is used to achieve non-linear resistivity, then electrical stress management is improved, but mechanical properties such as strength and elongation suffer significantly
Solution Approach 1:
The patent optimizes the concentration of dielectric active fillers to a moderate range (5-20 wt.%) rather than using high concentrations of conductive fillers. This parameter optimization achieves electrical stress management through the dielectric properties of TiO2, SiO2, and Al2O3 while preserving the mechanical strength and elongation properties of the silicone rubber matrix.
Solution Approach 2:
The patent uses a composite formulation combining silicone rubber with dielectric active fillers (TiO2, SiO2, Al2O3) and conventional fillers (carbon black, zinc oxide) in optimized proportions. This composite approach achieves electrical stress management without the mechanical property degradation associated with high concentrations of conductive fillers.
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
The silicone composition effectively reduces electrical stress in HVDC applications, increasing the lifespan of cable systems, providing high flame retardancy and tracking resistance while maintaining mechanical integrity under high voltage conditions.
Implementation Method 1
capacity of the electrical charges leads to a polarization in polymers on the electron or atom or molecular level and results in the formation of space and surface charges
Implementation Method 2
Materials currently used for construction of cable joints like liquid silicone rubbers are per se perfect electrical insulators with the bulk resistivity in the order of magnitude around 10^16-10^18 Ohm*cm
Data Source
AI summary
The invention relates to a silicone rubber composition having specific dielectric properties which can be used as insulator material in high voltage direct current applications and a method for the manufacture of cable accessories like cable joints. The invention comprises as well a method for the determination of the optimum dielectric properties and the related amount of dielectric active additives.