Capacitive Voltage Sensor with Shielded Sensing Electrode
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Solution Overview
Problem
Environmental pollution, such as snow or salt deposits, on capacitive voltage sensors can significantly affect their accuracy by altering internal capacitances, making them unreliable for voltage measurement applications.
Innovation Solution
A capacitive voltage sensor design featuring a capacitive network with a first conductor forming a boundary around a first interior space, a second conductor forming a boundary around a second interior space, and a third conductor shielded from external conductive material by an external insulator, preventing pollution deposits from affecting the capacitances between the conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensing electrode is exposed to measure voltage, then voltage measurement capability is achieved, but pollution deposits on the insulator affect measurement accuracy
Solution Approach 1:
A shielding electrode is introduced as an intermediary element between the sensing electrode and the polluted insulator surface. The shielding electrode forms a capacitive divider that blocks the harmful capacitive coupling between pollution deposits and the sensing electrode, while still allowing the sensing electrode to measure the voltage potential accurately.
Solution Approach 2:
The electrical field and capacitive coupling path are segmented into multiple stages. The shielding electrode creates an intermediate capacitive stage that separates the sensing electrode from the polluted surface, dividing the harmful capacitive effect into manageable segments that can be compensated for or blocked.
2Reliability
If shielding structure is added to protect sensing electrode, then pollution resistance is improved, but device complexity increases
Solution Approach 1:
The shielding electrode serves multiple functions simultaneously: it acts as a shield against pollution deposits, forms part of the capacitive voltage divider network, and provides a reference potential. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
Solution Approach 2:
The shielding function is merged with the voltage division function. The shielding electrode is integrated into the capacitive network rather than being a separate protective component, combining two functions (shielding and voltage measurement) into a unified structure.
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 design ensures that capacitance measurements remain unaffected by pollution deposits, enhancing the accuracy and reliability of voltage sensors and allowing them to be used in smart power distribution systems without the need for bulky voltage transformers.
Implementation Method 1
a third conductor shielded from external conductive material by an external insulator
Implementation Method 2
capacitive voltage sensor that is molded in a polymeric post insulator and that has a voltage measuring accuracy that is not changed by pollution deposits
Data Source
AI summary
A capacitive network for use in a voltage sensor includes a first conductor shaped to form a boundary that separates a first interior space and a first exterior space; a second conductor shaped to form a boundary that encircles a second interior space and separates the second interior space from a second exterior space; a third conductor disposed in the second interior space and having a line of sight to the first conductor through an opening in the second conductor; and an external insulator formed around the first conductor and the second conductor in the first exterior space and the second exterior space. A first capacitance is formed between the first conductor and the third conductor, a second capacitance is formed between the second conductor and the third conductor, and conductive material that may collect on the external insulator has negligible effect on the first capacitance and the second capacitance.