Current Transformer Temperature Sensing via DC Injection
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Solution Overview
Problem
Current transformers (CTs) face accuracy issues due to varying temperatures, especially in critical applications where additional temperature sensing devices are costly and may not provide accurate local readings when installed far from the CT, leading to potential equipment damage and downtime.
Innovation Solution
Modifying current transformers to incorporate a DC current circuit and voltage measuring circuit, allowing the device to function as both a current transformer and a temperature sensor, using a processor to calculate resistance and determine temperature for diagnostic purposes, including detecting loose connections or arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensing device is installed near the CT to provide local temperature information, then temperature measurement accuracy is improved, but device complexity and installation cost increase
Solution Approach 1:
The patent combines the temperature sensing function with the existing current transformer by utilizing its secondary winding. The CT's secondary winding serves dual purposes: maintaining its current transformation function while also acting as the sensing element for temperature measurement through resistance-based temperature detection, thereby eliminating the need for separate temperature sensing devices
Solution Approach 2:
The secondary winding of the current transformer is made multi-functional by enabling it to perform both its traditional current sensing role and a new temperature sensing role. By measuring the resistance of the secondary winding at different temperatures and correlating resistance changes to temperature changes, the single component achieves universal functionality
2Ease of operation
If a temperature sensing device is installed far from the CT due to space constraints, then ease of installation is improved, but temperature measurement accuracy deteriorates
Solution Approach 1:
The temperature sensing capability is merged directly into the CT structure through the secondary winding, ensuring the sensing element is always at the optimal location (inside or on the CT) regardless of external space constraints. This eliminates the installation location problem entirely
3Measurement precision
If additional temperature sensing equipment and installation are added to the CT system, then temperature measurement capability is improved, but installation cost increases
Solution Approach 1:
The patent merges temperature sensing functionality into the existing CT by utilizing its secondary winding, eliminating the need for separate temperature sensing equipment. This approach reduces installation costs while maintaining temperature measurement capability
Solution Approach 2:
The secondary winding is made multi-functional to perform both current transformation and temperature sensing, maximizing the utility of existing components and avoiding additional equipment purchases
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 accurate temperature compensation and early detection of potential electrical issues, maintaining reliable current readings and preventing equipment damage by integrating temperature sensing within the CT, reducing the need for external temperature sensing devices.
Implementation Method 1
a circuit for injecting a DC current into the secondary winding; a circuit for measuring a voltage across the secondary winding; a processor for calculating a resistance of the secondary winding from the measured voltage
Implementation Method 2
determining, by the processor, a temperature of the secondary winding; storing the determined temperature of the secondary winding in the memory for diagnostic use
Data Source
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AI summary
The present invention provides a method of using a current transformer for a temperature sensing device. The method determines the temperature of the current transformer's secondary winding by injecting a DC current into the secondary winding, measuring a voltage across the secondary winding, calculating the resistance of the secondary winding from the voltage induced into the secondary winding by the injected DC current and determining the secondary winding temperature by calculations or a comparison with verified resistance/temperature combinations.