HVDC Cable Insulation Space Charge Measurement Using Cut Specimens
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Solution Overview
Problem
Existing validation tests for space charge accumulation in high-voltage direct current (HVDC) cables are time-consuming, costly, and face challenges in separating space charge signals from environmental noise, especially in real-life cable measurements.
Innovation Solution
A device comprising a DC voltage source, voltage step generator, electrodes, piezoelectric sensor, and electrical-signal amplifier, which measures space charge in laboratory-cut specimens of cable insulation, allowing for quicker and more economical tests by correlating signal amplitude with charge density and position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If validation tests are carried out on real electrical insulation systems and real life-size cables, then the measurement represents actual cable behavior, but the measurement time and cost increase considerably
Solution Approach 1:
The invention segments the cable insulation system by taking specimens at predetermined depths (e.g., 10mm, 20mm, 30mm from the surface) rather than measuring the entire cable. This allows multiple depth-specific measurements to be conducted quickly in the laboratory, representing different regions of the insulation system without requiring time-consuming full-cable measurements.
Solution Approach 2:
The invention creates laboratory specimens that copy and represent specific regions of the actual cable insulation system. These specimens are taken at predetermined depths and replicate the insulation material properties, allowing rapid measurement of space charge distribution patterns that would otherwise require lengthy field measurements on complete cables.
2Reliability
If validation tests are carried out on real electrical insulation systems and real life-size cables, then the measurement represents actual cable behavior, but the measurement cost increases considerably
Solution Approach 1:
By segmenting the cable into small specimens at predetermined depths, the invention reduces the material and equipment requirements for measurement. Instead of requiring expensive full-cable testing facilities and equipment, the laboratory can use smaller, more affordable measurement setups for each specimen, significantly reducing overall measurement cost while maintaining representativeness through systematic depth sampling.
Solution Approach 2:
The invention creates simplified laboratory copies (specimens) that represent specific regions of the cable insulation system. These specimens can be measured using cost-effective laboratory equipment rather than requiring expensive field measurement systems, thereby reducing measurement cost while maintaining the ability to represent actual cable behavior through properly selected depth samples.
3Measurement precision
If measurements are carried out on cable specimens in a controlled environment, then the space charge signal can be clearly measured without environmental noise, but the measurement does not directly represent the noisy field environment
Solution Approach 1:
The invention applies local quality by measuring specific regions (predetermined depths) of the insulation system that are representative of the overall space charge distribution patterns. By selecting depths that capture the essential characteristics of charge accumulation in different regions, the laboratory measurements of individual specimens can clearly show signal patterns while still representing the broader field environment conditions.
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
Enables rapid and cost-effective laboratory tests on cable cuts, effectively isolating space charge signals from environmental noise, and considering temperature and electric field gradients, thus improving the evaluation of cable insulation degradation.
Implementation Method 1
The space charge and the charges at the electrodes in response to this electrical pulse launch acoustic waves that propagate through the material. These waves are detected by a piezoelectric sensor attached to one of the electrodes. The piezoelectric sensor acts as a converter that converts the acoustic signal into an electrical signal.
Implementation Method 2
a DC voltage source; a voltage step generator; a first electrode connected to the DC voltage source and to the voltage step generator
Implementation Method 3
the pulsed electro-acoustic (PEA) method is known, which consists in applying a voltage pulse to a material placed between two electrodes. The space charge and the charges at the electrodes in response to this electrical pulse launch acoustic waves that propagate through the material.
Data Source
AI summary
A device (10) for measuring space charge in a high-voltage direct current electric cable includes a DC voltage source (12), a voltage step generator (14), a first electrode (16) connected to the DC voltage source (12) and to the voltage step generator (14), a second electrode (18) that is grounded, a piezoelectric sensor (20) connected to the second electrode (18), an electrical-signal amplifier (22) connected to the piezoelectric sensor (20), and at least one specimen (24) of the electric cable placed between the first and second electrodes (16, 18) and including a cut of the cable made to a predetermined depth in the electrical insulation system of the cable. The amplitude of the signal measured at the output of the amplifier (22) is related to the charge density in the specimen (24) and the delay related to the distance of the charges from the piezoelectric sensor (20) giving the position of the charges.