Neutral Pole Current Transformer Module for Circuit Breakers
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Solution Overview
Problem
Current circuit breakers face high manufacturing costs and noise interference issues when detecting neutral pole currents due to the use of Rogowski coils, which require multiple sizes and shielding, and the installation of additional components like differential circuit sections to compensate for phase delays, leading to increased costs and complexity.
Innovation Solution
A neutral pole transformer module comprising a zero-phase current transformer, a printed circuit board, and an enclosure that converts and differentiates current signals into voltage signals, reducing noise interference and allowing for cost-effective detection without modifying existing overcurrent relays or adding components, using a current transformer to output a current signal rather than a voltage signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Rogowski coil is used to detect neutral pole current, then current detection is achieved, but manufacturing cost increases and noise interference occurs
Solution Approach 1:
The patent extracts the differential circuit section from the overcurrent relay and relocates it to the neutral pole transformer module. This separation allows the transformer module to independently handle signal conditioning (differentiation and phase shift), eliminating the need for complex shielding and multiple transformer sizes while maintaining accurate neutral pole current detection.
Solution Approach 2:
The neutral pole transformer module is designed as a universal component that can be applied across different circuit breaker models. By integrating the differentiation circuit and phase shift functionality into this single module, the invention eliminates the need for model-specific configurations and reduces manufacturing costs associated with producing multiple sizes of Rogowski coils and shields.
2Measurement precision
If a Rogowski coil is used for neutral pole current detection, then current signal is obtained, but phase delay occurs requiring additional compensation components
Solution Approach 1:
The patent combines the differentiation circuit and phase shift functionality into a single integrated neutral pole transformer module. This merging of functions eliminates the need for separate compensation components in the overcurrent relay, reducing overall device complexity while maintaining accurate phase alignment for neutral pole current detection.
3Measurement precision
If additional components are added to compensate for phase delay, then detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring the differentiation circuit and phase shift network within the neutral pole transformer module during manufacturing. This preliminary setup ensures that the phase alignment is automatically corrected without requiring additional components or complex configurations in the overcurrent relay, thereby reducing device complexity while maintaining detection accuracy.
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 solution minimizes external noise interference and reduces manufacturing costs by using a current transformer to detect neutral pole currents, allowing for efficient and economical detection without additional components or configuration changes, enabling effective protection of neutral pole circuits.
Implementation Method 1
a zero-phase current transformer configured to allow a transmission line of a neutral pole detection current output from the current transformer to pass therethrough and to provide a secondary output current signal obtained by reducing the neutral pole detection current in a predetermined ratio
Implementation Method 2
a printed circuit board connected to an output terminal of the zero-phase current transformer, configured to convert the secondary output current signal into a voltage signal, and to differentiate and output the converted voltage signal
Data Source
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AI summary
There is provided a neutral pole transformer module for a circuit breaker capable of minimizing an influence of external noise, detecting a neutral pole current at low manufacturing cost, and detecting a neutral pole current without modifying a configuration of an existing overcurrent relay or without installing an additional component in the existing overcurrent relay. The neutral pole transformer module for a circuit breaker comprises a ZCT configured to allow a transmission line of a neutral pole detection current output from the current transformer to pass therethrough and to provide a secondary output current signal obtained by reducing the neutral pole detection current in a predetermined ratio; a printed circuit board configured to convert the secondary output current signal into a voltage signal, and to differentiate the converted voltage signal and output the same; and an enclosure formed of an electrical insulator and enclosing the ZCT and the PCB.