MV Voltage Phasor Determination via LV Measurements
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Solution Overview
Problem
Medium voltage networks face challenges in accurate voltage and current phasor determination and power monitoring due to the lack of sophisticated sensors, with existing solutions being costly and intrusive, making it difficult to update existing networks and achieve precise measurements.
Innovation Solution
A method and device that determine three-phase voltage and power measurements in MV/LV substations using measured voltage information from the LV side, coupled with transformer parameters, to calculate and reconstitute accurate MV voltage phasors, and pair current and voltage phasors based on power factor criteria, allowing for efficient monitoring without expensive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage sensors are installed on the MV network, then voltage measurement accuracy is improved, but installation complexity and cost increase due to insulation requirements and intrusive installation
Solution Approach 1:
The patent uses the LV network as an intermediary to measure MV voltage indirectly. By measuring voltage on the LV side of the transformer and using transformer parameters, the system obtains MV voltage information without direct MV sensing, thus avoiding insulation and installation complexity issues
Solution Approach 2:
The patent replaces direct electrical measurement on the MV side with a computational approach using LV measurements and transformer model. This substitution eliminates the need for complex MV voltage sensors and their associated insulation requirements
2Measurement precision
If sophisticated sensors are used for accurate power monitoring, then measurement precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent creates a virtual model of the MV network by copying and scaling LV measurements through transformer parameters. This virtual representation provides accurate power monitoring data without requiring sophisticated MV sensors
Solution Approach 2:
The patent transforms LV voltage and current measurements into MV equivalent parameters using transformer ratios and impedance transformations. This parameter transformation enables accurate MV power monitoring through simpler LV measurements
3Productivity
If existing networks are updated with advanced monitoring equipment, then monitoring capability is improved, but accessibility and installation difficulty worsen
Solution Approach 1:
The patent inverts the conventional approach by measuring on the LV side (easier access) rather than the MV side (difficult access). This inversion enables monitoring capability improvement while maintaining installation accessibility
Data Source
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Figure 2A
Figure 2B
AI summary
The current parameters of the medium-voltage network, namely the current and voltage phasors and the power values, are determined based on measurements taken by sensors (12, 14, 16) commonly installed on the network (5, 7) at the transformer (8). In particular, the voltage phasor on each conductor of the medium-voltage network (5) is determined using the amplitude derived from that measured on the low-voltage network (7) and the phase angle measured on the medium-voltage network (5). The pairing of the medium-voltage current phasors, the angle measured at medium voltage, and the amplitude derived from low voltage is performed by comparison with the power factor cos ϕ of the network.