Switchgear Gas Quantity Estimation Using a Steady-State Thermal Model
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Solution Overview
Problem
Existing methods for determining the gas quantity in gas-insulated switchgear tanks face challenges in accuracy due to temperature measurement inaccuracies caused by thermal exchange between the gas and external environment, and the influence of ambient temperature and electrical current on pressure readings, making it difficult to detect small leaks.
Innovation Solution
A method using a gas temperature sensor and pressure sensor that acquires data at two different instants to determine a steady-state thermal model, correcting gas temperature measurements by integrating heat transfer models, and calculating gas quantity using the ideal gas law, allowing for more accurate gas quantity estimation without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If temperature and pressure sensors are fixed on the tank walls for gas quantity monitoring, then the device complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to thermal exchange between the sensor and external environment
Solution Approach 1:
The patent introduces a thermal model as an intermediary between the sensor reading and the actual gas temperature. The model includes thermal resistance parameters (R1 for sensor-to-gas interface, R2 for sensor-to-ambient interface) that mediate the relationship between measured temperature and actual gas temperature, allowing accurate gas quantity determination without direct thermal contact
Solution Approach 2:
The patent transforms the temperature measurement problem by changing from direct temperature measurement to indirect measurement through thermal model parameters. By measuring ambient temperature, sensor temperature, and pressure, the system calculates actual gas temperature using thermal resistance parameters, thereby achieving high precision without direct thermal contact
2Measurement precision
If sensors are placed inside the tank for accurate gas temperature measurement, then measurement precision is improved, but device complexity increases and reliability decreases due to additional penetration points
Solution Approach 1:
Instead of placing the sensor inside the tank to measure gas temperature directly, the patent inverts the approach by placing the sensor outside the tank and using thermal model calculations to determine the actual gas temperature. This inversion eliminates the need for internal sensor placement while achieving the same measurement objective
3Device complexity
If traditional pressure and temperature measurement methods are used, then device complexity is minimized, but measurement precision deteriorates making small leak detection difficult
Solution Approach 1:
The patent implements a feedback mechanism where the thermal model continuously uses ambient temperature measurements, sensor temperature readings, and pressure measurements to calculate and update the actual gas temperature. This feedback loop compensates for thermal effects and maintains high measurement precision for leak detection
Solution Approach 2:
The thermal model acts as an intermediary processing layer that takes simple sensor inputs (ambient temperature, sensor temperature, pressure) and transforms them into accurate gas quantity information, enabling small leak detection without increasing device complexity
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 method enhances the accuracy of gas quantity determination and leak detection by correcting temperature measurements and accounting for thermal exchanges, providing a robust and easy-to-calibrate solution for gas-insulated switchgear.
Implementation Method 1
the measured temperature may not be representative of the gas average temperature. In addition, because the thermal sensor is located on the wall of the tank and is not perfectly adiabatic, a thermal exchange between the inner gas in the sensor and the external environment exists
Implementation Method 2
a sensor with a pressure sensing probe and a temperature sensing probe are fixed in an interface plug fixed to a tank panel
Implementation Method 3
The quantity of the gas can therefore be calculated and monitored during the operation of the switchgear from the pressure and temperature measurements
Data Source
Figure 1
Figure 2
Figure 3(A)~3(B)
AI summary
The invention relates to a method for determining a quantity (n) of a gas (G) contained in a tank (1) of an insulated switchgear (2), the method comprising the steps : (i) acquiring a first temperature (T1) and a second temperature (T2) measured by a gas temperature sensor (3) respectively at a first instant (t1) and at a second instant (t2) during a calibration phase, (ii) acquiring a first pressure (P1) and a second pressure (P2) measured by a gas pressure sensor (4) at the first instant (t1) and at the second instant (t2), (iii) determining a steady-state model (M) of the tank thermal exchanges from the first and second acquired temperature (T1, T2) and from the first and second acquired pressure (P1, P2), (iv) acquiring a gas temperature (Tsens), a gas pressure (Psens) and an ambient temperature (Tamb) during a measurement phase, (vi) calculating the quantity (n) of the gas (G) contained in the tank (1) from the acquired gas temperature (Tsens), the acquired gas pressure (Psens), the acquired ambient temperature (Tamb) and from the determined steady state model (M).