Residual Current Device Dual Zero-Sequence Transformers
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Solution Overview
Problem
Existing residual current devices struggle to detect residual currents with a broad range of frequencies, particularly high-frequency AC waveforms, which poses a significant risk in electrical systems and can lead to fires and electrocution.
Innovation Solution
The proposed residual current device incorporates a first zero-sequence current transformer for passive detection and a first processing circuit for active processing, along with a second zero-sequence current transformer and processing circuit for active detection, enabling the device to detect residual currents across a wide frequency range, including high-frequency AC, through the use of precision rectification, amplification, and filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single zero-sequence current transformer and processing circuit are used, then the device complexity is low, but the detection frequency range is limited and cannot detect high-frequency AC residual currents
Solution Approach 1:
The patent divides the detection system into two separate channels: one for passive detection (first zero-sequence current transformer) and one for active detection (second zero-sequence current transformer). Each channel is independently designed to detect specific frequency ranges, allowing the system to cover a broader frequency spectrum while maintaining manageable complexity in each individual channel.
Solution Approach 2:
The patent creates a multi-functional detection system where the first zero-sequence current transformer handles passive detection for certain frequency ranges, while the second zero-sequence current transformer handles active detection for other frequency ranges. This universal approach allows a single device to detect multiple types of residual currents (smooth DC, mains frequency AC, and high-frequency AC) using different detection mechanisms.
2Reliability
If passive detection only is used, then the device structure is simple, but high-frequency AC residual currents cannot be detected
Solution Approach 1:
The patent segments the detection functionality into passive and active detection modes using two different zero-sequence current transformers. The first transformer implements passive detection for baseline coverage, while the second transformer implements active detection specifically for high-frequency AC residual currents, ensuring comprehensive detection capability.
Solution Approach 2:
The patent changes the operational parameters of the zero-sequence current transformers by implementing both passive and active detection modes. The active detection mode uses excitation signals at specific frequencies to detect high-frequency AC residual currents, while passive detection operates without external excitation, allowing the system to adapt to different detection requirements.
3Reliability
If multiple processing circuits are added to expand detection frequency, then the detection frequency range increases, but the device complexity and cost increase
Solution Approach 1:
The patent segments the processing functionality into dedicated circuits for passive detection and active detection. Each processing circuit is optimized for its specific detection mode, allowing independent design and optimization without requiring a single complex circuit to handle all detection types simultaneously.
Solution Approach 2:
The patent implements dynamic switching between passive and active detection modes through control circuits that can activate or deactivate specific detection channels based on operational requirements. This dynamic approach allows the system to use only the necessary detection mode at any given time, reducing the effective complexity while maintaining comprehensive detection 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
This configuration enhances the detection frequency of residual currents to hundreds of kilohertz, providing a better frequency response characteristic and ensuring reliable protection against various types of residual currents, including smooth DC, mains frequency AC, and high-frequency AC.
Implementation Method 1
a first zero-sequence current transformer, for passively detecting a residual current signal in a current-carrying conductor
Implementation Method 2
a second zero-sequence current transformer, for actively detecting a residual current signal in the current-carrying conductor
Data Source
AI summary
Embodiments of the present invention disclose a Residual Current Device (RCD). The RCD includes: a first zero-sequence current transformer, used for passively detecting a residual current signal of a current-carrying conductor; a first processing circuit connected to the first zero-sequence current transformer, used for acquiring the residual current signal from the first zero-sequence current transformer, and actively processing the residual current signal, where the first processing circuit is connected to a power source; a second zero-sequence current transformer, used for actively detecting the residual current signal appearing on the current-carrying conductor; and a second processing circuit connected to the second zero-sequence current transformer, used for acquiring the residual current signal from the second zero-sequence current transformer, and actively processing the residual current signal, where the second processing circuit is connected to the power source. The RCD can make a very good response within a wide frequency range, and achieve better frequency response characteristics.