HVDC Cable Insulation Space Charge Diffusion via Polarity Reversal
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Solution Overview
Problem
In high-voltage direct current (HVDC) systems, space charge accumulation in extruded polymer cables leads to premature insulation breakdown and reduced cable rating due to constant electric field polarity, which existing methods fail to effectively mitigate.
Innovation Solution
A method and control system that temporarily modulate electrical properties of the cable, reducing voltage and increasing current to facilitate diffusion of space charge, thereby extending the cable's lifetime by reducing space charge accumulation and promoting its dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC power is transmitted through extruded polymer cables, then power transmission capability is improved, but space charge accumulation occurs leading to insulation breakdown
Solution Approach 1:
The patent applies periodic reversal of DC voltage polarity to enable space charge diffusion. By alternating between positive and negative DC voltage modes, the electric field direction changes periodically, allowing accumulated space charge to diffuse during polarity transitions. This periodic action prevents continuous space charge accumulation while maintaining DC power transmission capability.
Solution Approach 2:
The patent changes the voltage polarity parameter over time by switching between positive and negative DC voltage modes. This parameter change enables the electric field to reverse direction, facilitating space charge diffusion. The voltage magnitude and polarity are dynamically adjusted to balance power transmission requirements with space charge mitigation.
2Duration of action of stationary object
If maintenance mode is entered to diffuse space charge, then cable lifetime is extended, but power transmission efficiency is reduced
Solution Approach 1:
The system periodically enters maintenance modes where voltage polarity is reversed or modulated to facilitate space charge diffusion. These periodic maintenance actions extend cable lifetime by preventing space charge accumulation, while accepting temporary reductions in power transmission efficiency during the maintenance periods.
Solution Approach 2:
The control system proactively enters maintenance modes before critical space charge accumulation occurs. By performing preventive maintenance actions, the system extends cable lifetime and prevents insulation breakdown, while minimizing the impact on overall power transmission efficiency through optimized maintenance scheduling.
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 approach effectively extends the lifetime of extruded polymer cables by temporarily reducing space charge accumulation and allowing its diffusion, even if at the expense of lower power transmission efficiency, thereby mitigating premature insulation breakdown.
Implementation Method 1
the electrical properties applied to the cable are varied, or modulated, so as to facilitate diffusion of space charge accumulation in the extruded polymer insulation
Data Source
AI summary
The present invention provides methods and apparatus for controlling HVDC power transmission systems so as to increase the effective lifetime of cables carrying the DC power (and particularly the extruded polymer insulation of those cables). The method includes entering a maintenance mode in which the electrical properties applied to the cable are varied so as to facilitate diffusion of space charge accumulation in the extruded polymer insulation.