Earth Fault Localization in Power Grids via Zero-Sequence Admittance
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Solution Overview
Problem
Existing solutions for compensating earth fault currents in multiphase power grids quickly reduce fault currents to zero, but this rapid intervention limits the ability to locate the fault location safely, risking spark formation and potential fires, as they cannot distinguish between transient and permanent faults.
Innovation Solution
A system with detectors and a control unit that gradually adjusts the output voltage's amplitude and phase angle to measure zero-sequence current and admittance, allowing for fault detection without exceeding safe current thresholds, enabling localization of earth faults without risking excessive power current and allowing continued power transmission until the fault is identified.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fault current is rapidly reduced to zero, then safety and damage prevention are improved, but the ability to locate fault position is worsened due to insufficient time for measurement
Solution Approach 1:
The system performs preliminary fault detection by measuring zero-sequence current and admittance before the fault current is fully compensated. The control unit gradually adjusts the output voltage to enable measurement of changes in zero-sequence parameters, allowing fault location to be determined in advance before the compensation process completes, thus resolving the contradiction between rapid compensation and adequate measurement time
2Difficulty of detecting and measuring
If supply voltage is applied to detect error, then fault detection capability is improved, but the risk of spark formation and forest fire increases due to excessive current
Solution Approach 1:
The control unit gradually adjusts the output voltage amplitude and/or phase angle to change the electrical parameters of the system. By controlling the output current to remain below a safe threshold (e.g., 0.5 A) while still enabling detection of changes in zero-sequence current and admittance, the system maintains fault detection capability without exceeding safe current levels that could cause spark formation or forest fires
3Reliability
If fault current compensation is immediately activated, then power protection is improved, but fault location information is lost before compensation begins
Solution Approach 1:
The system uses feedback from the detectors that continuously monitor zero-sequence current and admittance. The control unit processes these measurement values to determine fault location, and this information is used to guide the compensation process. The feedback loop ensures that fault location information is obtained and utilized before and during the compensation activation, preventing information loss
Data Source
AI summary
In a multi-phase power grid fed by a power source, earth fault (460) is located by means of a power supply source synchronized with the power grid, which is connected between a zero point of the grid and earth. In a fault current compensation mode (420), a control unit controls the alternating voltage source to compensate for any ground fault current in the power grid to a value below a threshold level. In a fault detecting mode (430), the control unit gradually adjusts the output voltage of the alternating voltage source with respect to amplitude and/or phase angle (440). A change of zero-sequence current and zero-sequence admittance between the alternating voltage source and a fault location is measured (450) by means of at least one detector. The at least one detector is communicatively connected to the control unit and reports recorded measured values representing zero-sequence current and/or zero-sequence admittance to the control unit. In the fault detecting mode, the control unit localizes a ground fault (460) based on at least one of said measurement values representing changes of the zero-sequence current and/or zero-sequence admittance, upon which an affected branch is disconnected (470) or the system switches to the fault compensation mode (420).