Switchgear Current Sensing via Integrated Conductor and Thermocouple
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Solution Overview
Problem
Existing current sensors in electrical switching and protection devices, such as current transformers and Rogowski toroids, are bulky, difficult to implement, and costly, and are not suitable for direct current applications, while shunts introduce resistive parts that increase dissipation and complicate the arrangement of phase current lines.
Innovation Solution
An electrical cut-off device that integrates a segment of the phase metal conductor between connection points, using a measuring unit with conductors, a temperature sensor, and a thermocouple cable to measure voltage differences and temperature, allowing current measurement without additional resistive parts, suitable for both alternating and direct current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current transformers or Rogowski toroids are used for current measurement, then galvanic isolation and low impedance are achieved, but the device becomes bulky and production costs increase
Solution Approach 1:
The patent extracts the current measurement function from the phase conductor itself by integrating a measuring segment directly into the conductor structure. This eliminates the need for separate external sensors like current transformers or Rogowski toroids, thereby reducing device volume while maintaining measurement capability through the integrated voltage drop measurement across the conductor segment.
Solution Approach 2:
The patent merges the current carrying function and the measurement function into a single integrated structure. The phase conductor serves dual purposes: transporting current and enabling current measurement through its inherent resistance. This consolidation eliminates bulky external sensors and reduces overall device complexity while maintaining galvanic isolation properties.
2Measurement precision
If current transformers or Rogowski toroids are used for current measurement, then accurate current sensing is achieved, but implementation difficulty and production complexity increase
Solution Approach 1:
The phase conductor serves its own measurement function by utilizing its inherent electrical resistance. The measuring segment is an integral part of the conductor that automatically provides the voltage drop signal needed for current measurement without requiring separate sensor components. This self-service approach simplifies manufacturing and improves production repeatability while maintaining measurement precision.
3Measurement precision
If a shunt is used for current measurement, then current sensing is enabled, but resistive dissipation increases and phase current line arrangement becomes complicated
Solution Approach 1:
The phase conductor is given multiple functions: it serves as both the current carrying path and the measurement element. By integrating the measuring segment into the conductor itself, the system eliminates the need for separate shunt components that would add extra resistance. The conductor's inherent resistance is utilized for measurement purposes, avoiding additional energy losses while maintaining current measurement capability.
4Measurement precision
If a shunt is used for current measurement, then current sensing is achieved, but device complexity and assembly difficulty increase
Solution Approach 1:
The patent extracts the measurement function from external shunt components and integrates it directly into the phase conductor structure. This integration eliminates the need for separate shunt elements and complex wiring arrangements, thereby reducing device complexity and simplifying assembly while preserving current measurement capability through the integrated voltage drop measurement.
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 solution provides a compact, easy-to-implement, and cost-effective current measurement method with improved linearity and accuracy, suitable for both alternating and direct current applications, avoiding the addition of resistive parts and facilitating assembly.
Implementation Method 1
at least one thermocouple cable (18) comprising a third conductor (19) and a fourth conductor (20) connected to each other at a so-called cold junction and a so-called hot junction
Implementation Method 2
said measurement unit is configured at least to measure the value of the voltage difference between the first conductor (10) and the second conductor (13)... so as to determine the value of the current flowing in the phase metal conductor (1)
Data Source
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AI summary
The invention relates to an electrical switching apparatus comprising: a phase current line (L) comprising a phase metal conductor (1), a switching unit (2), a measuring unit (6) comprising a current sensor (7) and a current measuring circuit (8), characterized in that: the current sensor (7) integrates a segment (9) of said phase metal conductor (1) located between a first connection point (P1) and a second connection point (P2) spaced apart from each other by a predefined distance (D) and in that the measuring unit (6) comprises a first conductor (10) and a second conductor (13), a temperature sensor (16) and a temperature measuring circuit (17) and a thermocouple cable (18), said measuring unit (6) is configured to measure the value of the voltage difference (Vshunt) between the first conductor (10) and the second conductor (13),the value of the voltage difference of the thermocouple cable (18) (VthC) and the value of the absolute temperature (VΘRef) near the so-called cold junction using the temperature sensor (16), so as to determine the value of the current flowing in the phase metal conductor (1).,