Interleaved Capacitor Divider Voltage Sensors for Circuit Breakers
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Solution Overview
Problem
Capacitive divider-type voltage sensors face challenges in minimizing electric field concentration, which can lead to dielectric breakdown, while also requiring a balance between compact size and ease of manufacture, as higher voltage line conductors increase electric field concentration and necessitate increased component spacing, thereby enlarging the device.
Innovation Solution
The design incorporates a plurality of interleaved conductive voltage sensor and ground layers with a first voltage sensor layer closest to the line conductor, separated by dielectric material, forming capacitors with capacitance proportional to interface area and inversely proportional to distance, and an outer ground layer to shield from external electric fields, using a flexible substrate with a rolled or wound configuration to maintain compactness and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between individual components of the capacitive divider is increased to minimize E-field concentration, then dielectric breakdown is prevented, but the overall size of the device increases
Solution Approach 1:
The voltage sensor is divided into multiple conductive layers (first conductive layer, second conductive layer, third conductive layer) with dielectric layers interspersed between them. This segmentation allows the E-field to be distributed across multiple smaller gaps rather than one large gap, preventing dielectric breakdown while maintaining a compact overall structure.
Solution Approach 2:
The capacitive divider structure is nested within a housing that contains multiple interleaved conductive and dielectric layers. The first conductive layer is positioned between the line conductor and the housing, the second conductive layer is positioned between the first and third conductive layers, creating a nested arrangement that minimizes E-field concentration without increasing external dimensions.
2Reliability
If multiple conductive layers are used to reduce E-field concentration, then dielectric breakdown is prevented, but the device complexity increases
Solution Approach 1:
The housing serves multiple functions: it provides mechanical support for the conductive and dielectric layers, acts as an E-field shield, and contains the entire capacitive divider structure. The first conductive layer serves both as an electrode and as the sensing element that outputs the divided voltage signal.
Solution Approach 2:
The first conductive layer, second conductive layer, and third conductive layer are electrically connected through conductive paths within the housing, merging them into a single functional unit. The dielectric layers are integrated between the conductive layers, combining insulation and structural support functions into a single compact assembly.
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 configuration effectively reduces the size and manufacturing cost of voltage sensors while minimizing electric field concentration, preventing dielectric breakdown and maintaining accuracy and reliability in voltage measurement.
Implementation Method 1
The voltage sensor defines a first capacitor Csc with capacitance from the voltage sensor to line conductor being proportional to the area of the interface surface between the first voltage sensor layer and the conductor and being inversely proportional to gsc. Each voltage sensor layer with the sensor to ground interface surface has a respective area and resides a distance gsg from a neighboring ground layer. The voltage sensor defines a second capacitor Csg with capacitance from the voltage sensor to ground being proportional to the area of the sensor layer to ground interface surfaces and the number of conductive layers with respective sensor to ground interface surfaces and is inversely proportional to gsg.
Data Source
AI summary
Multi-layer capacitor divider voltage sensors include a plurality of voltage sensor conductive layers having sensor to ground interface surfaces. Respective voltage sensor conductive layers are connected to each other and sensor output voltage Vs by continuations of material forming the interface surfaces extending therebetween. The voltage sensors also include a plurality of conductive ground layers connected to electrical ground, the ground layers interleaved with the voltage sensor conductive layers so that a conductive ground layer resides between adjacent conductive voltage sensor layers. A first voltage sensor conductive layer (closest to a line conductor) is electrically connected to the other conductive voltage sensor layers and output voltage Vs and has a sensor to conductor interface surface with a corresponding interface area. The interface areas and the gap distances are configured to provide desired capacitance for attenuation of conductor voltage Vc for a suitably sized Vs in a compact sensor package.