Piezo Fill Level Sensor for Oil-Filled Transformers
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Solution Overview
Problem
Existing devices for monitoring the fill level and temperature dependency in electrical devices with insulating oil, such as power transformers, are expensive, imprecise, and temperature-dependent.
Innovation Solution
A measuring device with a piezoelectric element and an evaluation device that excites and detects vibrations to determine the fill level, reducing temperature dependency and improving accuracy, and can generate alarm signals based on predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric transducers are used for determining fill level, then measurement capability is provided, but the device becomes expensive and temperature-dependent
Solution Approach 1:
The patent uses a simplified piezoelectric sensor system that copies the essential measurement function without the complex accompanying electronics of prior art. The piezoelectric element directly converts acoustic signals from the liquid column into measurable electrical signals, eliminating the need for complex matching transformers and multiple detector systems, thereby reducing cost and temperature dependency while maintaining measurement capability
Solution Approach 2:
The patent changes the measurement parameter from direct acoustic impedance measurement (temperature-sensitive) to vibration frequency and amplitude analysis (temperature-insensitive). By exciting the piezoelectric element at its resonant frequency and analyzing the resulting vibration characteristics, the system achieves temperature-independent fill level measurement
2Measurement precision
If complex monitoring systems are used, then measurement capability is improved, but the device becomes expensive to build
Solution Approach 1:
The patent extracts only the essential piezoelectric sensing function from complex prior art systems, removing unnecessary matching transformers, multiple detectors, and complex evaluation electronics. The simplified system uses a single piezoelectric element excited by a simple oscillating voltage, with measurement based on direct analysis of vibration characteristics, significantly reducing building cost while maintaining monitoring accuracy
Solution Approach 2:
The patent employs inexpensive piezoelectric ceramic elements as the sensing component, replacing expensive specialized transducers. These simple piezoelectric disks or plates can be easily manufactured and replaced if needed, providing cost-effective monitoring without sacrificing measurement precision
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 high-accuracy monitoring with low temperature dependency, allowing for effective detection of fill levels and potential discharges in electrical devices.
Implementation Method 1
a piezoelectric element arranged in the housing at a minimum level of the insulating oil
Data Source
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AI summary
An electrical device (10, 13), in particular a power transformer (13), compensation choke, or on-load tap changer (10), comprises – a housing (101, 131) which is filled or can be filled with insulation oil (11, 11'), and – a measuring device (12) which comprises • a piezo element (16) which is arranged in the housing (101, 131) at the height of a minimum fill level (19, 19') of the insulation oil (11, 11'); and • an evaluation unit (18) which is connected to the piezo element (16); wherein – the evaluation unit (18) is designed in such a way that it • can induce the piezo element (16) to vibrate; • can determine the measurement value of a measured variable of the vibration dependent on the fill level, in particular the half-life of the amplitude of the vibration.