Optical Current Measurement Resistor for HVDC Isolation
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Solution Overview
Problem
Existing high-voltage current measurement devices face limitations in frequency range, accuracy, and cost due to inductance and complex isolation requirements, particularly for high-voltage direct current (HVDC) and alternating current (HVAC) systems, and are prone to inaccuracies with DC and high-frequency components.
Innovation Solution
A measuring device utilizing a measuring resistor with an electro-optical unit to convert current-dependent electrical signals into optical signals, transmitted via optical fibers, and converted back to electrical signals at ground potential for evaluation, enabling reliable current measurement across a wide range of voltages, including ultra-high voltages, with simplified insulation and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current transformers are used for high-voltage current measurement, then measurement capability in high-voltage range is achieved, but measurement frequency is limited by inductance and measurement accuracy depends on frequency
Solution Approach 1:
The patent replaces the traditional electromagnetic current transformer with a measuring resistor that generates a voltage signal proportional to the current. This electrical measurement system is then converted to an optical signal for transmission, eliminating the inductance limitations of current transformers and enabling accurate measurement across a wide frequency range including DC and high-frequency components.
Solution Approach 2:
The patent introduces an optical signal as an intermediary between the high-voltage measuring resistor and the ground-potential evaluation system. The optical converter transforms the electrical measurement signal into an optical signal that can be transmitted through an optical cable, serving as a mediator that isolates the high-voltage side from the low-voltage side while preserving measurement accuracy.
2Temperature
If zero-flux measuring systems with magnetic fields are used, then current measurement in high-voltage lines is achieved, but costs increase due to complex insulation requirements
Solution Approach 1:
The patent replaces complex magnetic field-based zero-flux measuring systems with a simple voltage measurement approach using a measuring resistor. By measuring the voltage across the resistor and converting it to an optical signal, the system eliminates the need for complex magnetic shielding and insulation structures, significantly reducing device complexity and cost.
Solution Approach 2:
The optical signal serves as an intermediary that transmits measurement data from the high-voltage side to the ground side without requiring complex electrical insulation. The optical cable provides simple galvanic isolation, replacing the complex insulation requirements of electromagnetic coupling systems.
3Loss of information
If traditional electrical signal transmission is used from high-voltage potential to ground, then signal transmission is achieved, but insulation complexity and cost increase significantly
Solution Approach 1:
The patent uses an optical signal as an intermediary to transmit the measurement signal from high-voltage potential to ground. The optical converter transforms the electrical signal into an optical signal that can be transmitted through an optical cable, providing simple galvanic isolation without requiring complex high-voltage insulation structures.
Solution Approach 2:
The patent replaces traditional electrical signal transmission requiring complex high-voltage insulation with optical signal transmission. This substitution eliminates the need for complex insulation systems while maintaining signal integrity over long distances and providing inherent electromagnetic immunity.
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 provides reliable and accurate current measurement for both HVAC and HVDC systems, extending application fields, improving frequency range, and reducing costs, while maintaining signal integrity over long distances and complex voltage conditions.
Implementation Method 1
The electro-optical unit converts the measurement signal, which is present as an electrical signal, into an optical signal, for example, using a light-emitting diode
Implementation Method 2
The optoelectronic unit receives the measurement signal and converts it, for example... It is converted back into an electrical signal using a photodiode
Implementation Method 3
an optical transmission line for transmitting the optical measurement signal from the high voltage potential to ground
Data Source
AI summary
The invention relates to a measuring apparatus (1) for measuring an electrical current in an electrical line (3) with a measuring resistor (2) which can be inserted into the electrical line. The invention is distinguished by an electro-optical unit (44) which is arranged at high-voltage potential and is intended to convert a current-dependent electrical measurement signal produced at the measuring resistor (2) into an optical measurement signal, an optical transmission line (5) for transmitting the optical measurement signal from the high-voltage potential to earth potential level, and an opto-electrical unit (8) which is arranged close to the earth potential and is intended to convert the transmitted optical measurement signal into an electrical output signal. The invention also relates to a method for measuring current by means of the measuring apparatus and to a converter arrangement having a converter and the measuring apparatus.