Switch State Detection Circuit Using Series Clamping and Comparator
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Solution Overview
Problem
Existing devices for monitoring the open or closed state of switches in transformer protection relays are complex and cannot safely determine the state without being under tension, and they fail to monitor electrically isolated switches effectively.
Innovation Solution
A device that uses a comparator to differentiate between open and closed switch states by comparing a reference voltage with a voltage delivered by a current limiting and voltage limiting circuit, connected in series, and includes a microprocessor to process signals from sensors, a channel selector, and a frequency control device to manage switch states and provide diagnostic information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary switch is mounted in parallel with the monitored switch and a contact bias voltage is supplied to the monitoring circuit, then the switch state can be continuously monitored, but the device complexity increases and electrically isolated switches cannot be monitored
Solution Approach 1:
The patent extracts the monitoring function from the main circuit by using a separate monitoring circuit that draws minimal current through the switch being monitored. This allows the monitoring function to be separated from the main power circuit, enabling monitoring without adding parallel auxiliary switches or complex bias voltage systems. The monitoring circuit can be electrically isolated while still detecting switch states through its own current path.
Solution Approach 2:
The patent introduces an intermediary monitoring circuit that detects switch states without directly interfering with the main circuit operation. The monitoring circuit acts as a mediator by using a small monitoring current that flows through the switch, allowing state detection without requiring parallel auxiliary switches or complex voltage biasing arrangements.
2Measurement precision
If the monitoring circuit is polarized by the voltage present at the switch terminals, then the switch state can be detected, but electrically isolated switches cannot be monitored
Solution Approach 1:
The monitoring circuit uses an intermediary current path that can be electrically isolated from the main circuit while still detecting switch states. The circuit incorporates isolation components that allow the monitoring function to operate independently, enabling detection of switch states even when the switch is electrically isolated from the main power system.
Solution Approach 2:
The patent segments the monitoring function from the main power circuit, creating a separate monitoring subsystem that can operate independently. This segmentation allows the monitoring circuit to be electrically isolated while maintaining its ability to detect switch states through its own dedicated current path and isolation components.
3Loss of information
If the device is used to diagnose malfunctions by restarting the electrical installation, then the malfunction can be reproduced for diagnosis, but the safety of goods and people is jeopardized
Solution Approach 1:
The patent implements preliminary monitoring that continuously tracks switch states and malfunctions before they require diagnosis. By maintaining continuous monitoring records and detecting anomalies in real-time, the system can diagnose malfunctions without requiring system restarts or interventions under tension, thereby preserving safety while maintaining diagnostic capability.
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
Enables safe and accurate determination of switch states without being under tension, allowing for reliable monitoring of transformer protection relays and other electrical contacts, and provides parameterized data for fault diagnosis and operational insights.
Implementation Method 1
a current limiting circuit (2) and a voltage limiting circuit (3) connected in series, an input of the current limiting circuit (2) being connected to a first terminal of the switch (I)
Implementation Method 2
a current limiting circuit (2) and a voltage limiting circuit (3) connected in series
Implementation Method 3
a comparator (4) for comparing the predetermined reference voltage with the voltage delivered by the voltage limiting circuit (3) and delivering a comparison signal having a different value depending on whether the switch (I) is open or closed
Implementation Method 4
an output connected to an input of a low-pass filter (5)
Implementation Method 5
a charge regulator circuit (1) connected between an output of the filter low pass and current limiting circuit input
Data Source
Figure 1
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Figure 3
AI summary
The device has a current clamping circuit (2) and a voltage clamping circuit (3) arranged in series. An input of the current clamping circuit is connected on a terminal of a switch, where another terminal of the switch is connected to a mass of the device. A comparator (4) comprises an input unit that is connected to an output unit of the voltage clamping circuit. A load regulating circuit (1) is arranged between an output of a low-pass filter (5) and the input unit of the current clamping circuit.