Zero-Sequence Voltage Angle Estimation for Single-Phase Earth Faults
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for locating single-phase earth faults in distribution networks with decentralized generating devices are inaccurate due to bidirectional energy flow, and current solutions like Low Power Voltage Transformers are costly and not widely used, while Voltage Presence Indication Systems provide inaccurate voltage magnitudes leading to angular errors in zero-sequence voltage calculations.
Innovation Solution
A method and device that estimate the angle of zero-sequence voltage using detected phase voltage angles without the need for a voltage sensor, by determining the neutral earthing type and calculating real and imaginary parts of phase voltages, allowing for accurate single-phase earth fault detection with existing Voltage Presence Indication Systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Low Power Voltage Transformer (LPVT) is used to provide accurate voltage magnitude and angle, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the voltage angle information from the three-phase voltages, which is sufficient for zero-sequence voltage angle calculation. By using existing VPIS that provides accurate voltage angles without requiring full voltage magnitude measurement, the solution eliminates the need for expensive LPVT while maintaining sufficient measurement precision for fault detection
Solution Approach 2:
The patent replaces the expensive LPVT with a cheaper alternative approach using existing VPIS infrastructure. The VPIS provides voltage angle information at minimal cost, and the patent demonstrates that this cheaper information source is sufficient when combined with the proposed calculation method for estimating zero-sequence voltage angle
2Device complexity
If a Voltage Presence Indication System (VPIS) is used to provide voltage angle information, then device cost is reduced, but measurement precision deteriorates due to inaccurate voltage magnitude
Solution Approach 1:
The patent extracts only the voltage angle information from the three-phase voltages provided by VPIS, ignoring the inaccurate voltage magnitude. By formulating calculation methods that depend only on voltage angles (which VPIS provides accurately), the solution eliminates the impact of voltage magnitude measurement errors on the final zero-sequence voltage angle calculation
Solution Approach 2:
The patent changes the calculation approach from using voltage magnitudes (which are inaccurate in VPIS) to using voltage angles (which are accurate in VPIS). The proposed methods calculate zero-sequence voltage angle through trigonometric relationships involving only phase voltage angles, thereby transforming the problem from one受制 by magnitude accuracy to one that utilizes the strength of angle accuracy
3Device complexity
If direct summation of three phase voltages from VPIS is used to obtain residual voltage, then device complexity is reduced, but measurement precision deteriorates with unacceptable angular error
Solution Approach 1:
The patent replaces the direct mechanical summation approach (which assumes accurate voltage magnitudes) with a trigonometric calculation system that uses voltage angles. The proposed methods calculate the zero-sequence voltage angle through arctangent functions of sine and cosine components derived from phase voltage angles, thereby substituting a flawed mechanical addition approach with a mathematically rigorous angular calculation approach
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3~4
AI summary
Embodiments of the present disclosure provide a method and a device for estimating an angle of a zero-sequence voltage when a single-phase earth fault occurs in a distribution network with decentralized generating devices. The method for estimating an angle of a zero-sequence voltage comprises: detecting angles of respective phase voltages in three phase voltages; determining a neutral earthing type of the distribution network; and estimating the angle of the zero-sequence voltage when the single-phase earth fault occurs in the distribution network with the detected angles of the respective phase voltages, according to the neutral earthing type of the distribution network. The angle of the zero-sequence voltage may be estimated with the angles of the three phase voltages provided by the existing VPIS without accurate magnitudes of the three phase voltages, so that the detection for the single-phase earth fault is simpler and easier, and the cost of the earth fault detection device is reduced.