High-Voltage Insulation Resistance Measurement with Current Correction
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Solution Overview
Problem
In high-voltage systems, the determination of insulation resistance is distorted by parasitic current components, particularly capacitive charging currents caused by voltage drifts and fluctuations, which mask the small leakage currents, leading to inaccurate insulation resistance measurements.
Innovation Solution
A method and device that estimates capacitance values during test voltage ramp-up, corrects the measured current using a correction current derived from capacitance and voltage deviation, and calculates insulation resistance from the corrected current, effectively reducing the influence of charging currents and voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant DC voltage is applied as test voltage to the HV system, then the insulation resistance can be determined, but parasitic current components (capacitive charging currents and absorptive currents) mask the small leakage currents, leading to inaccurate measurements
Solution Approach 1:
The patent applies preliminary action by performing a ramp-up phase before the actual measurement. During this phase, the test voltage is gradually increased to the target value, allowing capacitive charging currents to decay before the measurement begins. This preliminary voltage application prepares the system by reducing parasitic currents, enabling more accurate leakage current measurement in the subsequent constant voltage phase.
Solution Approach 2:
The patent implements the skipping principle by rapidly increasing the test voltage to the target value during the ramp-up phase. This quick voltage transition minimizes the time during which large capacitive charging currents are present, allowing the measurement to start after these transient currents have decayed. The rapid voltage application 'skips' through the problematic transient period, enabling faster and more accurate measurements.
2Measurement precision
If the test voltage is ramped up to a predetermined constant target value, then the capacitive charging currents decay, but the ramp-up process takes time, reducing measurement efficiency
Solution Approach 1:
The patent applies partial action by performing the full voltage ramp-up to the target value and then maintaining it for a predetermined time before measurement. This ensures that parasitic currents have sufficiently decayed while avoiding excessive measurement time. The measurement is performed at an optimal point where accuracy is achieved without unnecessary delay, balancing precision and productivity.
Solution Approach 2:
The patent maintains continuous useful action by automatically transitioning through the ramp-up phase, decay period, and measurement phase without manual intervention. The system continuously monitors the voltage and current, automatically starting the measurement at the optimal moment when parasitic currents have decayed sufficiently. This continuous automated process maximizes measurement efficiency while ensuring accuracy.
3Measurement precision
If voltage drifts and fluctuations occur during measurement, then capacitive charging currents are generated that mask the leakage current, but increasing voltage stability requires more complex voltage regulation
Solution Approach 1:
The patent implements feedback by continuously monitoring the test voltage during measurement and using this information to correct for voltage drifts. The system measures the actual voltage applied to the HV system and uses this feedback to compensate for deviations from the target value, ensuring accurate insulation resistance measurement without requiring overly complex voltage regulation hardware.
Solution Approach 2:
The patent introduces an intermediary calculation step where the measured voltage is used to correct the current measurement. Instead of directly measuring insulation resistance from raw current data, the system uses the voltage measurement as an intermediary to calculate and apply corrections for voltage drift effects. This intermediary approach simplifies the overall system while maintaining measurement 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
Accurately determines insulation resistance by compensating for capacitive charging currents and voltage drifts, ensuring precise measurement of insulation resistance in high-voltage systems.
Implementation Method 1
a capacitive current component or charging current, which particularly includes a current for charging or recharging the capacitances in the HV system or the insulation
Implementation Method 2
an electrical charge of the high-voltage system to be tested and/or the component to be tested is determined while the test voltage is ramped up
Implementation Method 3
the insulation resistance is derived from the corrected measurement current and the measured measurement voltage
Data Source
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AI summary
In order to significantly and effectively reduce the effects of fluctuations in a measuring current (im) on the determination of an insulation resistance (R) in a high-voltage system, a method for determining an insulation resistance (R) in a high-voltage system (2) and an associated measuring system are proposed, in which during a run-up (LP) of a test voltage to a predetermined target value (Ut), first an electrical charge of the high-voltage system (2) to be tested and/or the component to be tested is determined (101) and then a capacitance value (C) for the high-voltage system (2) to be tested and/or the component to be tested is estimated from the determined charge (102), and in which during a measuring phase (MP), in which the predetermined target value (Ut) is reached and approximately maintained by the test voltage,From the estimated capacitance value (C) and from a temporal deviation of a measured measurement voltage (um) from the specified target value (Ut) of the test voltage, a correction current (idr) is determined (103), with which the respectively measured measurement current (im) is corrected. Then, from the corrected measurement current (ikorr) and the measured measurement voltage (um), the insulation resistance (R) is derived (104). At least the derived insulation resistance (R) can then be output and displayed (105).