Corona Resistant High Voltage Bushing with Semiconductive Glaze
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High voltage bushing assemblies in hydrogen-cooled large turbo generators face challenges in corona resistance and flashover, particularly due to high electric fields that can trigger discharges, compromising the integrity and accuracy of current monitoring systems.
Innovation Solution
The bushing assembly incorporates semiconductive glaze bands with varying resistivities on the outer surface of the insulating sleeve, forming a resistivity gradient, which enhances corona and flashover resistance, and includes an electrically conductive adhesive to connect the flange to the semiconductive glaze, reducing electric field interference with current transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage is provided to the conductor in the bushing assembly, then power transmission capability is improved, but corona discharge and flashover tendency increases
Solution Approach 1:
The patent applies semiconductive glaze with varying resistivities at specific locations on the insulating sleeve surface. The glaze has different resistivity values at different radial positions, creating local electrical property variations that control electric field distribution. This local quality modification reduces corona discharge and flashover tendency at critical high-voltage regions while maintaining overall power transmission capability.
Solution Approach 2:
The patent changes the electrical resistivity parameter of the glaze layer by incorporating semiconductive materials with specific resistivity values. The glaze resistivity is controlled to be between 10^6 to 10^9 ohm-cm, which is significantly lower than conventional non-semiconductive glaze. This parameter change allows better control of surface electric field distribution, reducing corona discharge and flashover while maintaining high voltage transmission.
2Ease of manufacture
If conventional non-semiconductive glaze is used on the insulating sleeve, then manufacturing simplicity is maintained, but electric field control and corona resistance are insufficient
Solution Approach 1:
The patent uses composite glaze material that combines conventional ceramic glaze with semiconductive additives such as metal oxides (manganese oxide, cobalt oxide, nickel oxide) or carbon black. This composite material maintains the mechanical properties and ease of application of traditional glaze while introducing controlled electrical conductivity. The semiconductive properties are achieved through the additive composition, allowing simple manufacturing processes to produce corona-resistant bushings.
3Power
If electric field intensity is increased to improve power transmission, then power capability is improved, but interference with current transformers increases
Solution Approach 1:
The semiconductive glaze acts as an intermediary layer between the high-voltage conductor and the external environment including current transformers. This intermediate layer with controlled resistivity (10^6 to 10^9 ohm-cm) modifies and redistributes the electric field, preventing direct high-intensity field interaction with surrounding components. The glaze serves as a buffer that maintains power transmission while reducing electromagnetic interference with measurement devices.
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 solution significantly reduces the tendency of corona discharge and flashover, maintaining the integrity of the bushing and ensuring accurate current monitoring by deflecting electric fields away from critical components, thereby improving overall system reliability.
Implementation Method 1
a first band of semiconductive glaze located on the outer surface of the insulating sleeve spaced apart from a first end of the insulating sleeve, the first band of semiconductive glaze including a plurality of sub-bands having different resistivities
Implementation Method 2
The solution significantly reduces the tendency of corona discharge and flashover, maintaining the integrity of the bushing and ensuring accurate current monitoring by deflecting electric fields away from critical components
Data Source
AI summary
A corona resistant high voltage bushing assembly includes an insulating sleeve to surround a conductor, a flange located on an outside surface of the insulating sleeve, and a first band of semiconductive glaze located on the outer surface of the insulating sleeve spaced apart from an end of the insulating sleeve.