Insulation Resistance Measurement via Dual Switch Cycling
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Solution Overview
Problem
Existing methods for measuring insulation resistance in electrical systems with multiple ground faults or faults at intermediate potentials suffer from low accuracy and fail to detect faults promptly, especially in ungrounded systems, leading to potential safety hazards and system damage.
Innovation Solution
A modified measuring arrangement that includes a measurement cycle with open switch S1 and closed switch S2, and vice versa, allowing for precise calculation of insulation resistance using differential current measurements, reducing the influence of measurement errors and enabling detection of faults at any potential, including intermediate positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single high-impedance resistor is connected to one pole for insulation resistance measurement, then the measurement is simple, but it cannot detect faults at both poles or intermediate potentials simultaneously
Solution Approach 1:
The measurement arrangement is segmented into two separate measurement paths: one path connects a first high-impedance resistor to the positive pole, and another path connects a second high-impedance resistor to the negative pole. This segmentation allows independent measurement of insulation resistance at each pole, enabling detection of faults at both poles and intermediate potentials simultaneously while maintaining measurement accuracy.
2Productivity
If measurement is performed with both switches open to avoid interference, then system operation is continuous, but faults at intermediate potentials cannot be detected
Solution Approach 1:
The system performs periodic insulation resistance measurements by alternating the switching states of S1 and S2. During normal operation, both switches remain open. At measurement intervals, the controller sequentially closes S1 (with S2 open) to measure positive pole insulation, then closes S2 (with S1 open) to measure negative pole insulation. This periodic action enables continuous system operation while maintaining accurate fault detection capability at all potentials.
3Adaptability or versatility
If a known resistance is connected in parallel during extended measurement method, then measurement range is extended, but measurement accuracy decreases due to small voltage changes
Solution Approach 1:
The system changes the measurement parameters by using high-impedance resistors (≥1 GΩ) connected to both poles simultaneously, rather than using low-impedance resistors or adding known resistances in parallel. This parameter change maintains the original voltage levels and ratios, avoiding the small voltage changes that degrade accuracy in extended measurement methods. The high-impedance configuration allows measurement of insulation resistance across the full range while maintaining precision.
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 high-precision insulation resistance measurement, even with simultaneous leakage resistances, reducing safety margins and system failure frequency, thus enhancing system availability and safety.
Implementation Method 1
determining the insulation resistance (R iso) of a live electrical device or a system with an operating voltage (U B)
Data Source
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Figure 5
AI summary
The equipment has two switches (S1, S2) such as relay switches, to produce a current path between one of positive or negative terminals and a ground point to determine total resultant insulation resistance during occurrence of isolation errors with arbitrary potential supply. A microcontroller measures the insulation resistance by two successive measurements, where the switch (S1) is closed and the switch (S2) is opened during one measurement, and vice versa in the other measurement.