Insulation Fault Assessment via Common-Mode Current Measurement
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Solution Overview
Problem
Existing methods for evaluating insulation faults between an electrical circuit and ground require stopping the load and only assess faults relative to the rectifier side, limiting their effectiveness and scope.
Innovation Solution
An electrical system that measures a first common mode current entering the circuit via phase and neutral points, loops it back through the ground, and uses a compensation current to cancel out common mode currents, allowing for continuous fault evaluation without load interruption, and determines insulation fault representative quantities by multiplying current and voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the load is stopped to assess the insulation fault, then the measurement can be performed, but the productivity is reduced
Solution Approach 1:
The device performs preliminary measurements of common-mode current and voltage before the load requires interruption, continuously monitoring insulation conditions so that fault assessment is already available when needed, eliminating the need to stop the load for measurement
Solution Approach 2:
The insulation fault evaluation operates continuously during load operation by injecting test signals through the common-mode choke and measuring the resulting currents and voltages, maintaining both productivity and measurement capability simultaneously
2Measurement precision
If the insulation fault assessment is performed only on the battery side relative to the rectifier, then the device complexity is reduced, but the measurement precision is limited
Solution Approach 1:
The measurement device is designed to assess insulation faults throughout the entire electrical system including both battery-side and grid-side circuits by utilizing the common-mode current path that encompasses all electrical connections, making the single device universally applicable to the complete system rather than requiring separate measurement systems for different sections
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
Enables continuous, comprehensive insulation fault evaluation between the electrical circuit and ground without stopping the load, providing accurate and representative electrical quantities for fault assessment.
Implementation Method 1
a device for measuring a first common-mode current entering the electrical circuit through its phase entry point(s) and its neutral point and looping back through the electrical ground, in particular through the insulation fault
Implementation Method 2
a device for multiplying the measurement of the first common-mode current by the voltage measurement to obtain the power developed by the electrical generator to supply the first common-mode current
Implementation Method 3
a generator, from the measurement of the second common-mode current, of a compensating current flowing from the electrical ground to the phase and neutral conductors, and being substantially equal to the first common-mode current
Data Source
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AI summary
The electrical system (116) includes: an electrical circuit (118); an electrical ground (132); and a device (172) for evaluating an insulation fault (152) between the electrical circuit (118) and the electrical ground (132).The evaluation device (172) includes: a device (168) for measuring a first common-mode current (imc) supplied by an electrical generator (164); a device (174) for measuring a voltage (vcp) supplied by the electrical generator (164); a device (176) for multiplying the measurement of the first common-mode current (imc) by the measurement of the voltage (vcp) to obtain a power (p) developed by the electrical generator (164) to supply the first common-mode current (imc); a device (178) for determining an active part (P) of the power (p); a device (182) for determining at least one electrical quantity (R; IR_eff) representative of the insulation fault (152), from the active part (P) of the power (p).