Rogowski Coil Partial Corona Discharge Detection
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Solution Overview
Problem
Existing methods for detecting partial corona discharge in electrical circuitry, especially in reduced pressure environments, are inaccurate due to field strength variations and interference from electromagnetic sources, making it difficult to predict onset with current RF detection techniques.
Innovation Solution
A Rogowski coil is wrapped around a targeted circuit leg to generate a signal representing current rate of change, which is then coupled to a three-dimensional display device for monitoring deviations from a normal waveform, allowing for non-invasive detection of partial corona discharge with high frequency sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RF corona detection methods are used in reduced pressure environments, then detection capability is provided, but test results vary due to field strength and signal attenuation from EMI filters and shielded enclosures
Solution Approach 1:
The patent replaces RF electromagnetic field-based detection with a Rogowski coil that measures magnetic field-induced voltage. This substitution of detection mechanism eliminates sensitivity to EMI filter attenuation and shielded enclosure effects, providing consistent measurements regardless of equipment shielding or field strength variations.
Solution Approach 2:
The Rogowski coil acts as an intermediary measurement device that indirectly detects corona discharge through the magnetic field generated by discharge current, rather than directly measuring the RF electromagnetic field. This intermediary approach bypasses the attenuation problems associated with EMI filters and shielded enclosures.
2Measurement precision
If grounding is used for corona discharge detection through the ground line, then detection capability is provided, but grounding complications and masking signals from other ground line signals occur
Solution Approach 1:
The patent extracts the detection function from the ground line by placing the Rogowski coil around a live conductor. This separation eliminates the need for ground line access and removes the complexity of grounding issues while avoiding masking from other ground line signals.
Solution Approach 2:
The Rogowski coil serves as an intermediary that measures the magnetic field around a live conductor without requiring electrical connection to the ground or the circuit being tested. This non-invasive approach simplifies the testing setup by eliminating grounding requirements.
3Measurement precision
If computer analysis equipment is used to detect pulse current signals up to tens of MHz, then detection capability is provided, but equipment cost becomes extremely high
Solution Approach 1:
The patent employs a simple Rogowski coil that can be easily constructed and is much less expensive than computer-based analysis equipment capable of handling tens of MHz signals. The coil provides adequate detection capability without requiring costly high-frequency measurement systems.
Solution Approach 2:
The patent replaces complex computer-based electronic analysis systems with a simple magnetic field sensing coil. This substitution dramatically reduces equipment cost while maintaining the ability to detect high-frequency corona discharge signals through the Rogowski coil's natural frequency response characteristics.
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 method provides consistent and accurate detection of partial corona discharge with immunity to electromagnetic interference, enabling selective testing of individual circuits and high frequency signal detection up to tens of MHz.
Implementation Method 1
A Rogowski coil may serve as a current sensor that develops an electrical output potential that is proportional to the rate of change of electrical current in the circuit that it measures
Data Source
Figure 1
AI summary
A method of detecting partial corona discharge in a targeted circuit of an electrical apparatus, comprises the steps of: wrapping a Rogowski coil around a leg of the targeted circuit to produce a Rogowski coil signal that represents electrical current rate of change in the leg of the targeted circuit; coupling the Rogowski coil signal to a three-dimensional display device that may represent the dimension of time, the dimension of amplitude as a function of a time, and the dimension of duration of amplitude as a function of time in successive periods of that have a preselected duration; monitoring the display device to detect deviations of the duration of amplitude as a function of time from a normal waveform in the leg of the targeted circuit; and correlating ones of the detected deviations of the duration of amplitude as a function of time from a normal waveform that exceed a preselected deviation level as indicative of partial corona discharge within the targeted circuit.