Differential Fault Protection Circuit for High-Frequency Leakage Detection
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Solution Overview
Problem
Existing differential protection devices are unable to effectively detect and protect against fire outbreaks caused by fault currents beyond 20 kHz, as they become complex, expensive, and bulky due to the need for multiple circuits, and their fire protection function is inoperative during power failures.
Innovation Solution
A differential protection device with a passive circuit comprising inductance, resistance, and capacitance connected in series or parallel with the secondary winding of a transformer, which compensates for parasitic capacitances and losses, allowing detection of high-frequency fault currents and providing a lower triggering threshold for enhanced safety and fire protection beyond 20 kHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple independent circuits are implemented to detect high-frequency fault currents beyond 20 kHz, then detection capability is improved, but device complexity increases and construction becomes bulky
Solution Approach 1:
The patent combines multiple circuit functions into a single integrated circuit that can detect both low-frequency (up to 20 kHz) and high-frequency (up to 100 kHz) fault currents. The circuit uses a single transformer with secondary winding connected to a control circuit that processes both frequency ranges, eliminating the need for separate parallel circuits and reducing overall device complexity while maintaining comprehensive detection capability.
Solution Approach 2:
The control circuit is designed with universal functionality to handle multiple detection tasks: it processes signals from the transformer secondary winding for both low-frequency and high-frequency ranges, and can activate different protection mechanisms (electromagnetic actuator for low-frequency, pyrotechnic charge for high-frequency) based on the detected fault type, thereby serving multiple purposes with a single circuit design.
2Measurement precision
If active electronic assemblies are used to achieve type B+ frequency response, then detection sensitivity is improved, but the device becomes costly and the fire-break function becomes inoperative during power failures
Solution Approach 1:
The circuit uses a pyrotechnic charge that is automatically activated by the detection circuit when high-frequency fault currents are detected. The pyrotechnic charge creates a physical fire-break in the conductor without requiring continuous external power, making the fire-break function self-sufficient and operational even during power failures. The system serves itself by using the detected fault signal to trigger the physical separation mechanism.
Solution Approach 2:
The patent replaces the need for continuous active electronic control with a pyrotechnic mechanism that provides mechanical/fire-based separation. Instead of relying on powered electronic actuators for fire-break functionality, the system uses a chemically-powered pyrotechnic charge that converts electrical detection signal into mechanical expansion and physical conductor separation, eliminating dependence on continuous mains power for the fire-break function.
3Reliability
If the detection threshold is lowered to enhance safety against cardiac fibrillation, then protection sensitivity is improved, but false triggering increases
Solution Approach 1:
The control circuit implements different detection thresholds and processing characteristics for different frequency ranges. For low-frequency signals (up to 20 kHz), one threshold level is applied, while for high-frequency signals (up to 100 kHz), a different threshold and processing approach is used. This localized quality adjustment allows the system to be highly sensitive to dangerous low-frequency faults while remaining selective against high-frequency noise, reducing false triggering without compromising protection sensitivity.
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 a compact, inexpensive, and electromechanical device capable of detecting fault currents beyond 20 kHz, enhancing safety and protection against fires while meeting regulatory standards for cardiac fibrillation and thermal runaway risks.
Implementation Method 1
at least one of the or all of the conductors of the circuit to be protected, or one of the conductors of the supply line of this circuit, pass(s) through a toroid of ferromagnetic material of a transformer of which the aforementioned conductor(s) form(s) the primary and which comprises one or more secondary winding(s)... in the event of a leakage, resulting in an imbalance of the input and output currents in the conductors of the lines to be protected, the flux created in the toroid by this imbalance at the primary level, induces a voltage in the secondary winding
Implementation Method 2
a pyrotechnic charge (13) adapted to be activated by said control circuit in the event of a fault current of a frequency comprised between 20 kHz and 100 kHz, said pyrotechnic charge (13) comprising an expansion element (131) adapted to expand in order to separate said conductors (P1, P2, P3, N)
Data Source
Figure 1~2
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AI summary
The subject of the present invention is a differential protection device (1) for detecting a leakage or fault current in an electrical installation. Said device (1) comprises, on the one hand, a transformer with a ferromagnetic core (T), with a primary consisting of at least two of the aforementioned conductors (P1, P2, P3, N) and with at least one secondary winding (BS), and, on the other hand, at least one processing and control circuit (ETC) suitable for processing the signal induced across the terminals of the secondary in the event of a fault and for controlling an electromagnetic actuator (MC). Differential protection device (1) characterized in that a passive circuit (CP) comprising at least one inductor (L) as well as at least one resistor and/or at least one capacitor (C) in series is connected to the terminals of the secondary winding (BS), in parallel thereto.