Transformer Coil Temperature Display Circuit Using CT Signal Power
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for simulating and displaying the winding temperature of electrical power transformers require a separate energy source for the evaluation circuits, leading to increased costs and risks of electromagnetic interference.
Innovation Solution
The use of a CT signal current to power a heating resistor and decouple energy via an electronic limiting circuit, eliminating the need for an additional energy source by employing an extraction transformer with a triac and diodes to manage energy flow, ensuring galvanic isolation and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate energy source is used to power evaluation circuits for measuring and displaying transformer winding temperature, then the measurement and display functions can be performed, but additional power lines and energy sources are required, increasing costs and electromagnetic interference risks
Solution Approach 1:
The CT signal current is utilized for multiple purposes: it serves both as the measurement signal for determining transformer load and as the power source for the evaluation circuit. This multi-functional use eliminates the need for separate power lines and energy sources, reducing system complexity while maintaining measurement reliability
Solution Approach 2:
The evaluation circuit powers itself by drawing energy from the CT signal current that is already present in the system for measurement purposes. The circuit extracts and utilizes its own power requirement from the existing signal path, eliminating dependency on external power sources and reducing electromagnetic interference risks
2Ease of operation
If additional power lines and energy sources are installed for evaluation circuits, then the circuits can be powered, but costs increase and electromagnetic interference risks increase
Solution Approach 1:
The harmful element (separate power supply system with its associated electromagnetic interference risks and costs) is extracted and eliminated. The evaluation circuit is made to operate using only the existing CT signal current, removing the need for additional power lines and external energy sources that would introduce electromagnetic interference
Solution Approach 2:
The CT signal current acts as an intermediary that serves dual purposes: it carries the measurement information about transformer load and simultaneously provides the energy required to power the evaluation circuit. This intermediary approach eliminates the need for separate power transmission paths that would be susceptible to electromagnetic interference
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 solution eliminates the need for additional power lines and energy sources, enhancing the reliability and longevity of components while reducing costs and interference risks.
Implementation Method 1
an additional measuring pressure corresponding to the winding temperature of the power transformer is generated by direct heating of the medium to be measured, which is separate from the measurement of the temperature of the coolant, using the electric heater immersed in the medium to be measured
Implementation Method 2
the interconnected cavities of the probe, capillary tube and transducer forming a closed pressure space which is filled with a measuring medium whose volume changes depending on the temperature
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a device for representing and displaying the coil temperature of an electrical power transformer and to an electrical circuit suitable therefor. The invention is based on the general concept of using the CT-signal current not only for supplying the heating resistor of a sensor, for example, but also for decoupling energy from the CT-signal current by transformation via an electronic circuit according to the invention in order to supply energy to the connected measurement devices, so that a separate energy source can thus be ultimately omitted. According to the invention, the primary coil of a transformer, hereinafter referred to as removal transformer, is inserted into the CT-signal current and the voltage sloping via the primary coil and secondary coil of the removal transformer is limited in that a triac triggered by two diodes connected in parallel short-circuits as soon as the corresponding half-cycle reaches a threshold value and does not open again until the next current zero-crossing of the CT-signal current.