Switchgear Screw Connection Fault Detection via Thermal Time Constants
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Solution Overview
Problem
Existing methods for detecting faults in switchgear bolted connections, particularly those between busbars and high-voltage cables, are ineffective due to the need for symmetrical current load and sensitivity to ambient temperature and electrical losses, making error detection difficult.
Innovation Solution
A method that utilizes two temperature sensors to determine the ratio of thermal time constants for temperature changes, generating an alarm if the ratio falls within an error range, thereby minimizing noise and statistical influences, and is independent of ambient temperature and electrical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absolute temperature values are compared between phases to detect defects, then fault detection capability is improved, but the method requires symmetrical current load and is sensitive to ambient temperature variations, making error detection difficult
Solution Approach 1:
The patent changes the measured parameter from absolute temperature values to thermal time constants derived from temperature profiles. By fitting exponential functions to temperature curves and extracting time constants, the method transforms the measurement approach to one that is independent of ambient temperature and current symmetry, resolving the contradiction between detection precision and environmental adaptability
Solution Approach 2:
The patent introduces thermal time constants as an intermediary parameter between the raw temperature measurements and fault detection. This intermediary absorbs the influence of ambient temperature and loading conditions, allowing reliable fault detection without requiring symmetrical current load or precise knowledge of environmental conditions
2Reliability
If absolute temperature measurements are used for fault detection, then temperature information is obtained, but the measurements are influenced by ambient temperature and electrical losses, reducing reliability
Solution Approach 1:
The patent extracts the thermal time constant parameter from the complete temperature measurement, separating the fault-related thermal response from the ambient temperature and electrical loss influences. By focusing only on the time constant extracted from exponential fitting of temperature profiles, the method eliminates the harmful influences while retaining the diagnostic information
Solution Approach 2:
Instead of directly analyzing absolute temperature values and trying to compensate for environmental influences, the patent inverts the approach by analyzing the rate of temperature change and extracting time constants from the temporal behavior of temperature profiles. This inversion naturally eliminates the influence of steady-state ambient temperature and electrical losses
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 approach provides more reliable fault detection by simplifying the fitting process and reducing reliance on absolute temperature measurements, allowing for early identification of faults through the ratio of thermal time constants, even with small changes in thermal influences.
Implementation Method 1
signals from two temperature sensors arranged in the switchgear are recorded
Implementation Method 2
a function that models a ratio of the temperature profiles at the temperature sensors determines the ratio of two thermal time constants for temperature changes
Data Source
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AI summary
A fit of measurement values of at least two temperature sensors situated in the vicinity of a first and a second screw connection is used to determine the relationship of two time constants of the temperature adaptation to a step-like current change and from the deviation of the ratio from a value of 1 it is concluded that there is a failure in the region of one of the screw connections.