Indirect Transformer Fluid Temperature Estimation via Wall Sensors
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Solution Overview
Problem
Existing methods for estimating the internal oil temperature of electrical transformers are inaccurate due to deviations caused by temperature measurements taken from external locations, which are affected by heat transfer methods and environmental conditions, leading to potential transformer failure if not addressed.
Innovation Solution
A method and system that estimate the internal fluid temperature of a transformer by measuring the temperature of its housing wall and ambient conditions, incorporating heat transfer properties and relative humidity to calculate the internal temperature using external sensors, thereby avoiding direct fluid contact and simplifying device construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wet RTD is used to directly measure dielectric fluid temperature, then measurement precision is improved, but device complexity and risk of dielectric fluid leaks increase
Solution Approach 1:
The patent uses the transformer housing wall as an intermediary medium to transfer thermal information from the dielectric fluid to the RTD sensor. The RTD is mounted on the external surface of the housing wall, which conducts heat from the internal dielectric fluid through the wall material to the sensor, enabling indirect temperature measurement without direct fluid contact.
2Reliability
If a dry RTD is used on the external housing surface, then device complexity is reduced and reliability is improved, but measurement precision deteriorates due to heat transfer deviations
Solution Approach 1:
The patent incorporates an algorithm that processes the raw temperature signal from the external RTD by applying heat transfer corrections. The system uses measured ambient temperature, relative humidity, and wind speed data to calculate heat transfer coefficients and compensate for environmental effects, providing feedback correction to the temperature measurement.
Solution Approach 2:
The patent changes the measurement parameters by incorporating environmental conditions (ambient temperature, relative humidity, wind speed) into the temperature calculation process. These additional parameters are used to adjust the heat transfer model and compensate for environmental effects on the external housing surface temperature measurement.
3Device complexity
If theoretical parameters are used to calculate dielectric fluid temperature, then device complexity is reduced, but measurement precision cannot be verified until transformer testing
Solution Approach 1:
The system uses the transformer's own housing structure and ambient environmental conditions to provide self-correction of the temperature measurement. The housing wall serves as both the container and the heat transfer medium, while ambient sensors provide data for automatic compensation, allowing the system to self-adjust without external calibration equipment.
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 approach provides a surprisingly accurate estimation of internal dielectric fluid temperature, closely correlating with actual measurements, enhancing transformer thermal performance modeling and operational reliability.
Implementation Method 1
Resistance thermometers, also called resistance temperature detectors or resistive thermal devices (RTD's), are sensors that measure temperature by correlating the resistance of the RTD element with temperature
Implementation Method 2
convection of the heat from the transformer dielectric fluid to the inner tank wall
Implementation Method 3
conduction of heat through the tank wall
Implementation Method 4
radiation from the outside tank wall to the outside air
Data Source
AI summary
A system and method for estimating a temperature of a fluid contained in an electrical device such as a transformer, circuit breaker, or reactor without direct thermal communication with the fluid is disclosed. The method includes measuring a temperature of an exterior wall of a housing of the electrical device, measuring an ambient temperature around the housing, and estimating a temperature of the fluid within the housing using the measured wall temperature and the measured ambient temperature. In a preferred aspect, the method also adjusts the estimated fluid temperature for one or more of ambient humidity conditions, conductive, convective, and radiation heat transfer properties associated with operation of the underlying electrical device.