Zeolite System for Power Cable Insulation Degassing
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Solution Overview
Problem
The degassing process of power cables with crosslinked insulating systems, which involves the removal of crosslinking by-products, is lengthy and costly due to the need for high temperatures and prolonged times, and introduces moisture that can compromise insulation properties.
Innovation Solution
Incorporating a zeolite system with two types of zeolites into the cable core, where one type effectively absorbs crosslinking by-products and the other type absorbs water molecules formed during these reactions, allowing for efficient and irreversible removal without affecting the insulating system's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a prolonged degassing process is used to remove crosslinking by-products, then the by-products are effectively removed, but the production time and costs increase significantly
Solution Approach 1:
The patent introduces a hygroscopic substance as an intermediary agent that facilitates the removal of crosslinking by-products. This substance absorbs the by-products (acetophenone and cumyl alcohol) during the degassing process, enabling more effective removal in a shorter time frame without directly heating the by-products to their evaporation temperatures.
Solution Approach 2:
The patent changes the parameters of the degassing process by introducing a hygroscopic substance that alters the mechanism of by-product removal. Instead of relying solely on thermal evaporation at high temperatures over extended periods, the process utilizes absorption by the hygroscopic substance, allowing for reduced time and potentially lower temperatures while maintaining or improving removal effectiveness.
2Reliability
If high temperature is applied to remove heavy by-products, then the by-products are eliminated, but moisture is introduced that compromises insulation properties
Solution Approach 1:
The hygroscopic substance serves as a mediator that addresses the moisture issue. It has the dual function of absorbing crosslinking by-products while also managing moisture content. The substance captures moisture that would otherwise be introduced during the degassing process, thereby preventing the harmful effect of increased moisture on the insulating system's electrical properties.
Solution Approach 2:
The patent converts the harmful effect of moisture introduction into a beneficial outcome. The hygroscopic substance, which would normally be expected to absorb moisture and potentially worsen the moisture problem, is instead used to control and manage moisture levels. By strategically placing and dosing the hygroscopic substance, the process transforms the potential harm of moisture introduction into a benefit where the substance acts as a moisture trap, protecting the insulating system from excessive moisture accumulation.
3Reliability
If batch-wise degassing is performed, then by-products are removed, but production efficiency decreases due to inability to process continuously
Solution Approach 1:
The patent enables continuous processing by introducing a hygroscopic substance that allows for ongoing degassing operations. The substance remains active throughout the process, continuously absorbing by-products as they migrate from the insulating system. This eliminates the need to stop and restart operations between batches, maintaining continuous useful action and significantly improving production efficiency while preserving by-product removal effectiveness.
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 approach significantly reduces the degassing time and temperature, preventing space charge accumulation and water-tree formation, thereby enhancing the cable's insulation properties and reducing manufacturing costs.
Implementation Method 1
a first zeolite having a SiO2/Al2O3 ratio higher than 5 and equal to or lower than 20... capable of effectively absorbing the crosslinking by-products
Implementation Method 2
a second zeolite having a SiO2/Al2O3 ratio of 5 at most... capable of effectively absorbing the water molecules
Data Source
Figure 1~2
AI summary
The present disclosure relates to an energy cable comprising at least one cable core comprising an electric conductor, a crosslinked electrically insulating layer, and particles of a zeolite system comprising at least a first zeolite and a second zeolite placed in the cable core. The particles of the first zeolite are able to extract and absorb, very efficiently and irreversibly, the by-products deriving from the crosslinking reaction, so as to avoid space charge accumulation in the insulating material during cable lifespan. The particles of the second zeolite are able to absorb the water molecules that unexpectedly form from the dimerization/oligomerization and decomposition reaction of the crosslinking by-products upon their absorption on the first zeolite, so as to avoid the formation of water-trees in the insulating material. Moreover, the present invention relates to a method for extracting crosslinking by-products from a cross-linked electrically insulating layer of an energy cable core, which comprises manufacturing the energy cable core comprising particles of the above-said zeolite system, heating the energy cable core up to a temperature causing migration of the crosslinking by-products from the crosslinked electrically insulating layer; and then placing a metal screen around the energy cable core.