Transformer Short-Circuit Protection via Voltage Analysis
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Solution Overview
Problem
Conventional short-circuit protection methods for transformers with multiple secondary windings are costly and unreliable, as they require multiple circuit breakers and current sensors, and fail to detect short circuits occurring inside the transformer or between output terminals and circuit breakers.
Innovation Solution
A method and device that detect short circuits by analyzing output voltages across multiple windings, using voltage sensors to determine short-circuit characteristics such as amplitude and phase variations, and sending a protection signal to a controllable circuit breaker on the high-voltage side to disconnect the transformer from the power grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current-based protection with multiple circuit breakers and current sensors is used for transformers with multiple secondary windings, then short-circuit protection coverage is improved, but protection cost is greatly increased
Solution Approach 1:
The patent replaces current-based protection (requiring current sensors and multiple circuit breakers) with voltage-based protection. By monitoring voltage changes at the transformer output terminals, the system can detect short circuits without needing current sensors or additional circuit breakers for each winding, significantly reducing protection cost while maintaining coverage.
Solution Approach 2:
The voltage-based protection method serves multiple windings simultaneously with a single detection system. Instead of requiring separate current sensors and circuit breakers for each of the N windings, one voltage detection system can monitor all windings, making the protection system universal and cost-effective for transformers with any number of secondary windings.
2Ease of operation
If circuit breakers and current sensors are installed on distribution terminals, then protection is provided for downstream faults, but short circuits inside the transformer or between output terminals and circuit breakers cannot be detected
Solution Approach 1:
The patent places voltage detection at the transformer output terminals, which is upstream of the distribution terminals where conventional current sensors are installed. This preliminary positioning allows the system to detect short circuits before they occur downstream, including faults inside the transformer windings or between the output terminals and the distribution terminals, providing comprehensive protection coverage.
Solution Approach 2:
The patent uses voltage as an intermediary parameter to detect short circuits. Instead of directly measuring current (which requires sensors at distribution terminals), the system measures voltage at the output terminals, which changes characteristically during short-circuit conditions. This intermediary measurement approach enables detection of faults that would be invisible to current sensors installed downstream.
3Device complexity
If voltage-based detection is used instead of current-based methods, then protection cost is reduced and detection sensitivity is improved, but detection of certain fault types may be challenging
Solution Approach 1:
The patent employs feedback by continuously monitoring voltage changes and comparing them against characteristic patterns of short-circuit faults. The system analyzes the feedback signal (voltage waveform changes) to distinguish between normal operation and various fault conditions, maintaining high detection capability while using simpler voltage-based sensors instead of expensive current sensors.
Data Source
AI summary
The invention provides a transformer short-circuit protection method and a transformer short-circuit protection device. The transformer short-circuit protection method includes: acquiring output voltages of a plurality of output lines of at least one winding on a low-voltage side of a transformer; and determining a short circuit according to the output voltages, and sending a protection signal when the short circuit is determined.