Asymmetry Detector Circuit for Multiphase Power Networks
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Solution Overview
Problem
Existing methods for detecting asymmetry or symmetry in multi-phase power networks, particularly during switching operations, fail to accurately determine when all phase voltages are stable, leading to potential false triggers of residual current circuit breakers due to leakage currents, which can occur even in the absence of insulation faults.
Innovation Solution
A method that analyzes the pulsating direct voltage generated by rectifying phase voltages to detect asymmetry or symmetry by comparing instantaneous values with a relative value of the peak voltage, ensuring that all phase voltages remain stable over a defined delay time before generating a detection signal, thus preventing false triggers of residual current circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the Y capacitor is connected with a time delay during switch-on, then leakage current is reduced, but false tripping may still occur during switch-off due to undetected phase voltage asymmetry
Solution Approach 1:
The patent applies preliminary action by detecting phase voltage asymmetry before the Y capacitor is connected during switch-on. The control device monitors phase voltages and only permits Y capacitor connection when symmetry is confirmed, preventing leakage current generation at switch-on. Additionally, the system continues monitoring during switch-off and detects asymmetry that may cause false tripping, allowing preventive disconnection of the Y capacitor before residual current device tripping occurs.
Solution Approach 2:
The patent implements feedback by continuously monitoring phase voltages and using this information to control Y capacitor connection. The control device receives feedback about phase voltage symmetry and adjusts Y capacitor connection accordingly - connecting only when symmetric and disconnecting when asymmetry is detected, thereby dynamically preventing both switch-on and switch-off leakage current problems.
2Reliability
If phase voltages are monitored continuously to detect asymmetry, then false tripping is prevented, but device complexity increases
Solution Approach 1:
The patent applies universality by using the existing rectifier circuit that generates DC voltage for power supply purposes and simultaneously utilizing its output voltage for phase asymmetry detection. This multi-functional use of the rectifier circuit allows asymmetry monitoring without adding separate monitoring hardware, thereby preventing false tripping while minimizing increase in device complexity.
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 allows for early and accurate detection of phase voltage stability, minimizing false triggers of residual current circuit breakers and ensuring safe operation of multi-phase power systems by immediately identifying asymmetry or symmetry, thereby preventing unnecessary shutdowns and reducing leakage currents.
Implementation Method 1
analyzing the pulsating direct voltage generated by rectifying phase voltages
Data Source
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AI summary
The invention relates to a method for detecting an asymmetry or symmetry of phase voltages (UL1, UL2, UL3) of a multiphase power network (SN), wherein the instantaneous values of the phase voltages (UL1, UL2, UL3) are detected by means of an asymmetry detector (AD) in that the asymmetry detector (AD) comprises a rectifier (BG) by means of which a pulsating DC voltage UDC is generated by rectifying the phase voltages (UL1, UL2, UL3). To achieve fast and reliable detection, the asymmetry or symmetry of the phase voltages (UL1, UL2, UL3) is detected by analyzing the pulsating DC voltage UDC, whereby an instantaneous value UDC(t) of the pulsating DC voltage UDC is acquired using an instantaneous value detector (MD), whereby a peak value U_Peak of the pulsating DC voltage UDC is determined, and whereby the instantaneous value UDC(t) is compared with the peak value U Peak using a comparator (K).where a detection signal indicating symmetry is generated only when the instantaneous values of all phase voltages (UL1, UL2, UL3) are continuously detected of approximately the same magnitude over a switch-on delay time dT_ev, such that the instantaneous value UDC(t) does not fall below the relative value U_Rel over the duration of the switch-on delay time dT_ev; and where, if the instantaneous value of only one of the phase voltages (UL1, UL2, UL3) falls below a setpoint such that the instantaneous value UDC(t) falls below a predetermined relative value U_Rel once, a detection signal DS indicating asymmetry is generated essentially without delay.