Insulation Resistance Measurement for Large Ground Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large photovoltaic generator systems with high ground capacitance values require extended time for insulation resistance measurement due to slow charging currents, making existing methods inefficient for determining insulation resistance in live circuits.
Innovation Solution
A method and device that utilize a higher voltage pulse to charge the ground capacitance to a level equivalent to a lower voltage, then switch to the lower voltage, stabilizing the current and allowing for faster measurement of insulation resistance using Ohm's law, with optional reversed polarity measurements for increased precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bipolar DC voltage pulse is injected to measure insulation resistance in a PV generator, then the measurement can be performed on a live circuit, but the measurement time becomes excessively long due to the large ground capacitance requiring extended charging time
Solution Approach 1:
The patent applies preliminary action by first charging the ground capacitance to a predetermined voltage level before the actual insulation resistance measurement begins. This pre-charging step (equipping phase) prepares the system in advance so that when the measurement pulse is applied, the capacitance is already ready, eliminating the need to wait for charging during the measurement process itself. This resolves the contradiction by separating the charging function from the measurement function in time.
Solution Approach 2:
The measurement process is segmented into distinct phases: an equipping phase where capacitance is charged to a predetermined voltage, and a measurement phase where insulation resistance is actually measured. This segmentation allows each phase to be optimized independently - the equipping phase prepares the system quickly, and the measurement phase captures data during the stable period, thereby reducing total measurement time while maintaining accuracy.
2Measurement precision
If the ground capacitance is charged to the injected voltage level, then the current stabilizes for accurate measurement, but the exponential charging curve causes significant delay even with increased power rating
Solution Approach 1:
The patent changes the voltage parameter dynamically - first charging the capacitance to a higher predetermined voltage level during the equipping phase, then using this pre-charged state during measurement. By changing the voltage parameter to a higher level temporarily for charging, then maintaining it during measurement, the system achieves both fast charging and accurate measurement, improving productivity without sacrificing precision.
Solution Approach 2:
The system performs preliminary charging of the ground capacitance to a predetermined voltage level before the measurement pulse is applied. This advance preparation ensures that when measurement begins, the capacitance is already charged and current has stabilized, allowing immediate accurate measurement without waiting for the exponential charging curve to complete, thus improving measurement throughput.
3Speed
If a higher voltage pulse is used to charge the ground capacitance faster, then the charging time is reduced, but the current magnitude increases which may affect measurement accuracy
Solution Approach 1:
The patent uses a higher voltage pulse in advance during the equipping phase to quickly charge the ground capacitance to the required level. After this preliminary high-voltage charging completes the capacitance charging rapidly, the system switches to the measurement phase where insulation resistance is measured during the stable current period. This temporal separation allows high voltage to be used for speed without compromising measurement precision.
Solution Approach 2:
The process is divided into an equipping phase using higher voltage for fast charging, and a measurement phase using the pre-charged state for accurate measurement. This segmentation allows the system to use high voltage temporarily when needed for speed, then switch to measurement conditions that ensure accuracy, resolving the contradiction between charging speed and measurement 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
Significantly reduces the measurement time by eliminating charging current influence, allowing for quicker and more accurate determination of insulation resistance in systems with large ground capacitance.
Implementation Method 1
the ground capacitance (15) of the system (10) to be measured is charged by a higher voltage level (U1) until a boundary condition is met, wherein the determined charging state of the ground capacitance (15) at the higher voltage level (U1) has a value which corresponds to a fully charged state of the ground capacitance (15) at the lower voltage level (U2)
Implementation Method 2
allowing for quicker and more accurate determination of insulation resistance using Ohm's law
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A method for the measurement of an insulation resistance of a system having a ground capacitance is provided. The method comprises providing a DC voltage generator, and connecting it to the system to be measured; supplying a first, higher voltage level to the system, thereby injecting a current into the system and charging the ground capacitance; frequently or continuously determining the charging state of the ground capacitance; and when a boundary condition is met, switching the DC voltage generator from supplying the higher voltage level to supplying a second, lower voltage level to the system; measuring the current injected into the system at the lower voltage level; and determining the insulation resistance of the device, based on the measured injected current at the lower voltage level.