Varistor-Thyristor Overvoltage Protection for Temporary Surge Clamping
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Solution Overview
Problem
Conventional surge protection devices fail to provide effective protection against temporary overvoltages and surge currents, especially at voltage levels close to nominal system voltage, and often lack a safe end-of-life mode of operation, leading to potential equipment damage and downtime.
Innovation Solution
An active energy absorber is introduced, comprising an overvoltage protection module with thyristors and a metal oxide varistor connected in series, along with an inductor and a trigger circuit, which selectively conducts fault current in response to overvoltage conditions, ensuring safe operation and energy absorption capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surge protection devices are used, then basic overvoltage protection is provided, but they fail to provide effective protection against temporary overvoltages and surge currents at voltage levels close to nominal system voltage
Solution Approach 1:
The patent employs a trigger circuit that dynamically activates the series combination of varistor and thyristor only when overvoltage conditions are detected. This dynamic switching enables the device to adapt its protection characteristics based on real-time voltage conditions, providing effective protection at voltage levels close to nominal system voltage while maintaining normal operation during standard conditions.
Solution Approach 2:
The invention changes the electrical parameters of the protection circuit by introducing a thyristor that can switch between non-conducting and conducting states. This parameter change allows the varistor to operate effectively at different voltage levels, particularly improving protection capability at voltage levels close to nominal system voltage where conventional devices fail.
2Reliability
If conventional surge protection devices conduct limited current for prolonged periods during overvoltage conditions, then protection is maintained, but the devices overheat and may fail
Solution Approach 1:
The trigger circuit acts as an intermediary that controls when the varistor-thyristor series combination conducts current. By detecting overvoltage conditions and selectively activating the protection circuit, the trigger circuit prevents prolonged current conduction that would cause overheating, while still providing necessary protection during actual surge events.
Solution Approach 2:
The protection circuit operates in periodic cycles: the trigger circuit continuously monitors voltage conditions, activates the varistor-thyristor combination when overvoltage is detected, and deactivates it when normal conditions resume. This periodic on-off operation prevents continuous current flow and associated overheating while maintaining protection readiness.
3Reliability
If conventional surge protection devices are used, then some overvoltage protection is provided, but they lack a safe end-of-life mode of operation, leading to potential equipment damage and downtime
Solution Approach 1:
The patent incorporates a fail-safe design where the series combination of varistor and thyristor, controlled by the trigger circuit, ensures that even at end-of-life, the device transitions to a safe state. The trigger circuit's continuous monitoring and the series configuration prevent uncontrolled current flow, cushioning against potential equipment damage that could occur with conventional devices lacking defined end-of-life behavior.
4Reliability
If an active energy absorber with thyristors and varistors is introduced, then effective protection against temporary overvoltages and surge currents is achieved, but device complexity increases
Solution Approach 1:
The protection device is segmented into distinct functional modules: a trigger circuit for detection, a varistor for voltage clamping, and a thyristor for current control. This segmentation allows each component to perform its specific function efficiently while making the overall complex device more manageable and maintainable through modular 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 active energy absorber effectively clamps overvoltage conditions to a specific voltage limit, providing reliable protection against temporary overvoltages and surge currents while ensuring a safe end-of-life mode, reducing equipment damage and downtime.
Implementation Method 1
an active energy absorber, comprising an overvoltage protection module with thyristors and a metal oxide varistor connected in series
Implementation Method 2
an overvoltage protection module with thyristors and a metal oxide varistor connected in series, along with an inductor and a trigger circuit, which selectively conducts fault current
Data Source
AI summary
A circuit protection device is provided. The circuit protection device includes an active energy absorber that is coupled between two power lines in an electrical power distribution system and is configured to selectively conduct fault current responsive to overvoltage conditions. The active energy absorber includes an overvoltage protection module that includes two thyristors that are connected in anti-parallel with one another and a varistor that is connected with the overvoltage protection module as a series circuit. The series circuit including the varistor and the overvoltage protection module is connected between the power lines.