Rotary Switch Transformer Protection
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Solution Overview
Problem
Current protection systems for medium-voltage/low-voltage transformers are inadequate in preventing damage from overloads, leading to high failure rates and safety risks for operators, as they often rely on inefficient circuit breakers and do not effectively prevent re-energization of faulty transformers.
Innovation Solution
A method and device that utilize thermal detection to interrupt medium-voltage supply current by a polyphase rotary switch integrated within the liquid dielectric, triggered by a bimetallic thermal probe, ensuring safe disconnection and preventing re-energization of overloaded transformers, while also providing protection against internal faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuit breakers are used to protect transformers against overloads, then protection function is provided, but reliability is insufficient with failure rate greater than 5% per year
Solution Approach 1:
The patent changes the protection parameter from electrical current intensity to thermal effect accumulation. The thermal element responds to the integrated thermal effect of overload current over time, rather than just instantaneous current magnitude, enabling more accurate detection of damaging thermal conditions that circuit breakers miss.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic circuit breaker system with a thermal-mechanical system. A thermal element subjected to the thermal effect of overload current mechanically actuates a switch mechanism, providing more reliable protection based on actual thermal damage accumulation rather than electrical parameters alone.
2Ease of operation
If circuit breakers allow closing operation after tripping, then operational flexibility is maintained, but safety risk increases due to potential re-energization of faulty transformers
Solution Approach 1:
The patent applies preliminary anti-action by preventing the closing operation before the harmful re-energization can occur. The thermal element maintains the switch in the open position until sufficient cooling time has elapsed, proactively blocking potential unsafe re-energization attempts rather than reacting after damage occurs.
Solution Approach 2:
The patent implements feedback through the thermal element that continuously monitors the thermal state of the transformer. This thermal feedback mechanism provides real-time information about the transformer's condition, automatically preventing closing operations when thermal conditions indicate potential damage or insufficient cooling.
3Reliability
If protection devices are integrated into the transformer, then protection effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent merges the protection function with the existing transformer structure by integrating the switch mechanism and thermal element directly into the transformer assembly. This combination eliminates separate external protection devices and their associated complexity while maintaining effective protection functionality.
Solution Approach 2:
The patent creates a multi-functional device where the integrated switch mechanism serves both as a protection device and as the main switching element for the transformer. The thermal element simultaneously provides overload protection and operates the switch, reducing the need for separate components and simplifying the overall system.
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 effectively reduces transformer damage from overloads, ensures operator safety by preventing re-energization of faulty transformers, and provides comprehensive protection against internal faults, significantly lowering failure rates and operational risks.
Implementation Method 1
triggered by a bimetallic thermal probe
Implementation Method 2
immersed in a liquid dielectric
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
The method involves interrupting average voltage power supply current by a rotative average voltage switch (20) according to thermal detection of variation of temperature of an active part (4) in an electrical average voltage/low voltage transformation apparatus to be protected e.g. multiphase average voltage/low voltage transformer (1), where the interruption is directly carried out in liquid dielectric i.e. mineral oil, in which the transformation apparatus is immersed. The switch is actuated by a control device (3) that is triggered by a temperature sensor (9) subjected to the temperature. An independent claim is also included for a system for protecting an electrical average voltage/low voltage transformation apparatus against overload.