Current Peak Limiting Device for High Voltage Networks
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Solution Overview
Problem
High-voltage electrical networks face challenges in managing short-duration short-circuit currents, particularly in networks with simplified architectures where standard equipment cannot handle peak currents exceeding 50kA, and are affected by high DC components and transient recovery voltages.
Innovation Solution
A method and device that utilize a detection and control module to anticipate and manage current peaks by diverting current through a resistor, reducing the DC component, and employing an electronic cut-off circuit with thyristors to protect the resistor from overheating, allowing for ultra-fast reaction and peak current limitation without requiring new switchgear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple sources are connected to the main bar to increase power supply capacity, then the power supply capability is improved, but the short-circuit peak current increases beyond what standard equipment can handle
Solution Approach 1:
The system performs preliminary detection of the derivative of short-circuit current (dl/dt) to anticipate the upcoming current peak before it reaches maximum value. This early detection enables the fast switch to open at the optimal moment, limiting the peak current to a safe level while maintaining the benefit of multiple connected sources for power supply capability.
Solution Approach 2:
A fast switch is introduced as an intermediary device between the power sources and the load. This switch acts as a mediator that can rapidly open to limit the short-circuit peak current while allowing normal operation during non-fault conditions, thus enabling the system to accommodate multiple sources without being constrained by standard equipment ratings.
2Object-affected harmful factors
If a fast switch is used to limit peak current, then the peak current limitation is achieved, but the switch may overheat due to the high current
Solution Approach 1:
The electronic cut-off circuit using thyristors is triggered periodically or in response to the current waveform characteristics to divert the high current away from the fast switch. The thyristors are turned on at specific moments in the AC cycle to bypass the fast switch during high current periods, preventing overheating while maintaining peak current limitation.
Solution Approach 2:
The electronic cut-off circuit with thyristors serves as a secondary intermediary that activates when the fast switch needs protection from excessive current. This additional mediator diverts the high current through an alternative path, protecting the fast switch from thermal damage while maintaining the overall current limitation function.
3Loss of time
If the derivative of current (dl/dt) is measured to anticipate current peak, then the reaction time is reduced, but the measurement precision requirements increase
Solution Approach 1:
The system replaces complex high-precision measurement systems with a simplified electronic derivative detection circuit. By using electronic signal processing to detect the rate of change of current (dl/dt), the system achieves ultra-fast reaction times without requiring extremely precise measurement equipment, as the derivative detection can be implemented with standard electronic components and circuits.
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
Effectively limits peak currents within 10-8ms of fault occurrence, reducing the risk of equipment overload and extending the lifespan of existing switchboards by rapidly decreasing the DC component and peak current, thus enabling safe operation of high-voltage networks with short-circuit currents up to 63kA.
Implementation Method 1
the measurement module is suitable for measuring the derivative of the current as a function of time dl/dt
Implementation Method 2
open the fast switch so as to deflect the current in electrical resistor (16) so as to reduce the peak current
Implementation Method 3
absorb said first current peak so as to protect said fast switch and said resistor against overheating
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a device for limiting an initial current peak resulting from a fault in a medium or high voltage electrical network. The device according to the invention comprises: - a current peak detection module (20) for the current peak in said electrical network, - an electrical circuit (12) comprising, in parallel, a fast switch (14), an electrical resistor (16) and an electronic switching circuit (18), - a detection and control module (10, 20) configured to, firstly, open the fast switch (14) before the occurrence of said current peak to divert the current to the electrical resistor (16) so as to reduce the peak current in devices located downstream of said electrical circuit and, secondly, to successively close the electronic switching circuit (18) so as to protect the resistor (16) against overheating and then the fast switch after absorption of the initial current peak by said resistor.