Current Transformer Transient Suppression in Switchgear
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Solution Overview
Problem
Existing medium and high voltage switchgears face damage from very fast transients during switching operations, which are not effectively suppressed by current solutions that require modification to the switchgear construction, particularly in gas insulated systems.
Innovation Solution
A method that utilizes the secondary winding of a current transformer and its equivalent resistance, along with a suppressing module, to form a suppressing circuit that is activated before and after the switching operation, allowing for transient suppression without altering the main components or insulating gas in the switchgear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ferromagnetic rings are put directly on the GIS busbar to suppress very fast transients, then transient suppression is achieved, but the insulating distance between the inner part of the switchgear enclosure and the live element is reduced
Solution Approach 1:
The patent uses the measuring circuit as an intermediary component to suppress very fast transients. Instead of directly modifying the busbar with ferromagnetic rings, the invention utilizes the existing measuring circuit (which is already present in the switchgear) and transforms its function to provide transient suppression. The measuring circuit acts as a mediator between the transient disturbance and the system, providing suppression without requiring direct contact with or modification of the live busbar elements, thus preserving insulating distances.
2Object-affected harmful factors
If a high-frequency capacitor is embedded in a current transformer enclosure to suppress very fast transients, then transient suppression is achieved, but the construction of the current transformer is interfered with
Solution Approach 1:
The patent makes the measuring circuit multi-functional by enabling it to perform both its original measurement function and an additional transient suppression function. The same measuring circuit that measures current in the switchgear is also configured to suppress very fast transients during switching operations. This eliminates the need for separate suppression devices and avoids interfering with current transformer construction, as the existing measuring circuit is simply repurposed to provide dual functionality.
3Measurement precision
If the measuring module is connected during switching operations, then current measurement is available, but very fast transients are not suppressed
Solution Approach 1:
The patent dynamically changes the configuration of the measuring circuit based on the operational state of the switchgear. During normal operation, the measuring circuit is connected to provide current measurement functionality. During switching operations when very fast transients occur, the measuring circuit is dynamically disconnected or reconfigured to provide transient suppression instead. This dynamic switching of function ensures that the system adapts to different operational conditions, providing measurement when needed and suppression when needed, without compromising either function permanently.
4Object-affected harmful factors
If special suppression equipment is installed in gas insulated systems, then very fast transients are suppressed, but the switchgear construction is interfered with
Solution Approach 1:
The patent enables the measuring circuit to serve itself by transforming its own function to provide transient suppression. Instead of requiring external special suppression equipment to be installed in the gas insulated switchgear, the existing measuring circuit is reconfigured to provide the suppression function autonomously. The measuring circuit uses its own components (such as the secondary winding and associated circuitry) to generate the suppression effect, eliminating the need for additional specialized equipment and avoiding interference with the switchgear's gas-insulated construction.
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 suppresses very fast transients without interfering with the switchgear's construction, ensuring equipment safety and preventing damage to transformers and cables, while maintaining the integrity of the switchgear's insulation and operational functionality.
Implementation Method 1
A signal generated by the secondary winding 2 of a current transformer in response to transients occurring during switching operations of the switching device 8
Implementation Method 2
Magnetic coupling of the primary winding 1 and of any secondary winding is realized by the toroidal magnetic core of the current transformer, nor shown in the drawing. The magnetic core is made of a material of a broad-band frequency characteristic, e.g. of nanocrystalline or amorphous tape
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention deals with a method and system for suppressing very fast transients during opening/closing a switching device (8) in medium and high voltage switchgear. The method and system uses the secondary winding (2) and nanocrystalline or amorphous cores of a current transformer installed in the switchgear. The method is characterized in that the measuring function of the measuring circuit (3) is periodically changed into a function of a suppressor of very fast transients by in-series connection of a switching-over module (9) or (9') into the measuring circuit. Before activation of the switching device (8) a control signal is sent to the switching-over module which disconnects the measuring module (4) from the measuring circuit (3). Next, after disconnecting the measuring module (4) a control signal is sent to the switching device (8) and the opening/closing process is carried out. At the moment of opening/closing the switching device (8) a signal is again sent to the switching-over module (9) or (9') and again the measuring module (4) is connected to the measuring circuit (3).