Transformer Interturn Short Circuit Detection via Voltage Differential
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Solution Overview
Problem
Current detectors for transformer interturn short circuits in transformers less than 6300 KVA lack effective protection mechanisms, leading to delayed detection of initial failures, which can escalate into severe accidents, and existing solutions face challenges with signal extraction and precision due to load variations and iron core comparisons.
Innovation Solution
A single-phase transformer with potential transformers and independent converters is used to compare voltage differentials from high and low voltage windings, allowing for precise detection of interturn short circuits without being affected by load performances, and triggering protective actions when thresholds are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a third coil is installed in transformer body for detection, then interturn short circuit detection capability is provided, but installation difficulty increases and signal extraction becomes problematic
Solution Approach 1:
The patent extracts the detection function from the transformer body by using existing windings and external conversion circuits. Instead of installing a third coil inside the transformer, the invention uses the original high and low voltage windings combined with external potential transformers and conversion circuits to achieve detection, thereby avoiding the installation difficulty of internal coil placement.
Solution Approach 2:
The patent introduces external conversion circuits and potential transformers as intermediaries between the transformer windings and the detection system. These intermediaries convert the voltage signals from the existing windings into comparable signals without requiring direct internal access or additional coils within the transformer body.
2Reliability
If signal is extracted from third coil for differential protection, then protection capability is achieved, but signal accuracy deteriorates due to load variations
Solution Approach 1:
The patent employs feedback mechanisms through the potential transformers and conversion circuits to continuously monitor and compare voltage signals. The system uses the relationship between high and low voltage winding signals to detect changes in transformation ratio, providing feedback that compensates for load variations and maintains detection accuracy.
Solution Approach 2:
The patent changes the detection parameter from direct current measurement to voltage differential measurement. By converting the detection basis to voltage differential between high and low voltage windings, the system becomes less sensitive to load variations and achieves more stable detection results.
3Device complexity
If same iron core is used for voltage signal comparison, then device complexity is reduced, but short circuit risk increases and precision decreases
Solution Approach 1:
The patent segments the voltage conversion function by using separate potential transformers for high and low voltage sides. This segmentation isolates the sampling signal paths, preventing short circuits between different voltage levels while maintaining the ability to compare voltages through the conversion circuits.
Solution Approach 2:
The patent introduces independent conversion circuits as intermediaries between the high and low voltage windings. These intermediaries enable voltage comparison without direct connection, thereby eliminating the short circuit risk associated with using the same iron core for both voltage signals.
4Device complexity
If no protective circuit is installed for interturn short circuit detection, then device complexity is minimized, but failure detection timing deteriorates
Solution Approach 1:
The patent implements preliminary detection by continuously monitoring voltage differentials between high and low voltage windings through the conversion circuits. This preliminary action enables early detection of interturn short circuits before they escalate into severe failures, providing advance warning while maintaining relatively simple device architecture.
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
The solution provides high precision and effective differential protection, unaffected by load variations, enabling early detection and prevention of transformer failures, thus enhancing safety and reliability of power supply.
Implementation Method 1
A potential transformer (PT) is provided on the high voltage side of the single-phase transformer (TM)
Implementation Method 2
The tap (K1) of the high voltage winding (K) is connected to the input end of a first converter (Q') and the voltage at output end of said first converter (Q') is the first voltage (U1')
Data Source
AI summary
An improved internturn short circuit detection device of transformer via differential voltage comprises a single-phase transformer (TM). The single-phase transformer (TM) comprises a high-voltage coil (K) and a low-voltage coil (N). A voltage transformer (PT) is positioned at the high voltage side of the single-phase transformer (TM). Two branches of a tap (K1) of the high-voltage coil (K) are connected with the input of a first converter (Q′), and a first voltage (U1′) is obtained. The secondary side of the voltage transformer (PT) is connected with the input of a second converter (Q), and a second voltage (U1) is obtained, and the first voltage (U1′) and the second voltage (U1) are compared, and when the voltage difference is above a predetermined primary threshold value, an interturn short circuit failure of the primary side is determined. A tap (N1) of the low-voltage coil (N) and one terminal of the low-voltage coil (N) are connected with the input of a third converter (M′), and a third voltage (U2′) is obtained, and two terminals of the low-voltage (N) are connected with the input of a fourth converter (M), and a fourth voltage (U2) is obtained, and the third voltage (U2′) and the fourth voltage (U2) are compared, and when the voltage difference is above a predetermine secondary threshold value, an interturn short circuit failure of the secondary side is determined.