High-Voltage Insulation Resistance Measurement with Current Correction
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Solution Overview
Problem
In high-voltage systems, determining insulation resistance is hindered by parasitic current components and voltage drifts, especially in systems with large capacitances, leading to inaccurate measurements of small leakage currents.
Innovation Solution
A method and device that corrects measurement current by estimating capacitance during test voltage ramp-up, using integration to determine electrical charge, and compensates for voltage drifts with a correction current to derive accurate insulation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant DC test voltage is applied to measure insulation resistance, then the leakage current can be measured to determine insulation resistance, but parasitic current components (capacitive charging current and absorptive current) interfere with the measurement, especially in systems with large capacitances
Solution Approach 1:
The patent applies preliminary action by measuring the test voltage during the ramp-up phase before the steady-state measurement. This allows the system to capture voltage drift information in advance, enabling subsequent compensation of parasitic current components during the actual insulation resistance measurement phase.
Solution Approach 2:
The patent implements feedback by continuously monitoring the test voltage during ramp-up and using this information to generate correction current components. The measured voltage drift is fed back to calculate compensation values that are applied during the measurement phase to eliminate parasitic current interference.
2Measurement precision
If the test voltage is ramped up to a predefined target value, then the measurement can be performed, but voltage drifts and fluctuations occur, especially in systems with large capacitances, leading to inaccurate leakage current measurements
Solution Approach 1:
The patent measures voltage drift during the ramp-up phase before steady-state operation is reached. This preliminary measurement of voltage behavior allows the system to predict and compensate for expected drifts during the actual measurement phase, maintaining voltage stability without requiring complex real-time regulation.
Solution Approach 2:
The patent changes the measurement approach by introducing correction current components that dynamically adjust the effective test voltage. By calculating compensation values based on measured voltage drift and applying correction currents, the system maintains stable voltage conditions despite inherent drifts and fluctuations.
3Measurement precision
If a regulated voltage source is used to generate test voltage, then the target voltage value can be maintained, but low-frequency noise (1/f noise) in feedback control causes drift voltages and fluctuations that interfere with small leakage current measurements
Solution Approach 1:
The patent uses feedback by measuring the actual test voltage during ramp-up and comparing it with the target value. This feedback information is used to calculate correction currents that compensate for drifts and fluctuations, effectively canceling out the harmful effects of 1/f noise in the feedback control system.
Solution Approach 2:
The patent converts the harmful voltage drifts and fluctuations into useful information by measuring them during the ramp-up phase. The measured drifts are then used to calculate compensation values that eliminate their harmful effects during the measurement phase, turning the problem into a solution.
4Measurement precision
If the measurement is performed after capacitance charging is complete, then parasitic current components have decayed, but voltage drifts during the ramp-up phase have already occurred, affecting measurement accuracy
Solution Approach 1:
The patent performs preliminary measurement of voltage drift during the ramp-up phase before the steady-state measurement begins. This allows the system to capture voltage behavior information in advance, enabling compensation during the actual measurement without requiring additional time after charging completion.
Solution Approach 2:
The patent maintains continuous measurement throughout the ramp-up phase to capture voltage drift information continuously. This continuous action allows the system to accumulate compensation data during the charging process itself, eliminating the need for separate post-charging measurement phases and reducing overall measurement time.
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 minimizing the influence of charging currents and voltage fluctuations, ensuring precise measurement of leakage currents in high-voltage systems.
Implementation Method 1
a measurement current caused by the test voltage and a measurement voltage currently applied to the high-voltage system to be tested and/or to the component to be tested are measured
Implementation Method 2
an electrical charge of the high-voltage system to be tested and/or of the component to be tested is determined during a ramp-up of the test voltage to a predefined constant target value
Implementation Method 3
a capacitance value for the high-voltage system to be tested and/or for the component to be tested is also estimated from the determined charge
Implementation Method 4
a correction current is then determined during a measuring phase from the estimated capacitance value and from a temporal deviation of the measured measurement voltage from the predefined target value of the test voltage
Data Source
AI summary
To significantly and effectively reduce the effects of fluctuations in a measurement current on the determination of an insulation resistance in a high-voltage system, a method for determining an insulation resistance in a high-voltage system and an associated measuring system are proposed, in which, during a ramp-up of a test voltage to a predefined target value, first an electrical charge of the high-voltage system to be tested and/or the component to be tested is determined and then a capacitance value for the high-voltage system to be tested and/or the component to be tested is estimated from the determined charge, and in which, a correction current is determined from the estimated capacitance value and from a temporal deviation of a measured measurement voltage from the predefined target value of the test voltage during a measuring phase, in which the predefined target value is reached and approximately maintained by the test voltage, the correction current being used to correct the respective measured measurement current, and then the insulation resistance is derived from the corrected measurement current and the measured voltage. At least the derived insulation resistance can then be output and displayed.