VQI – System for Aggregation of Voltage Quality Parameters “Voltage Quality Index”
What is it used for?
- Automatic downloading, processing, and aggregation of voltage quality data.
- Introduction of a continuous function to evaluate how close each parameter (voltage, frequency, unbalance, etc.) is to acceptable voltage compatibility limits.
- Implementation of aggregation techniques for each measurement point, quality parameter, and time interval – providing the distribution system operator with a meaningful index representing voltage quality (VQI).
- Individual measurement point indices can be further aggregated to create a global index for a specific area of interest (substation, MV feeder, supply transformer, etc.).
- User-configurable data visualization enabling gradual localization of problem areas in the network.
How does the system work?
- Automated downloading of voltage quality records from measurement stations in the distribution network, or import of data already downloaded by another system.
- Aggregation algorithms:
- for a specific point in the distribution network,
- for an area of interest,
- for defined time resolution.
- The goal is to interpret characteristic voltage parameters using the VQI index ranging from 1 to -1. A value of 1 indicates ideal parameters, values decreasing toward zero indicate deteriorated parameters (still within limits), and values below 0 indicate voltage quality parameters outside compatibility limits.
- Central database for storage and statistical evaluation of all data.
- Visualization via a web portal on map backgrounds, with secure access.
Currently implemented indices
- VQIU – index evaluating supply voltage magnitude
- VQIU2 – index evaluating voltage unbalance (voltage unbalance factor)
- VQITHD – index evaluating total harmonic distortion
- VQIflicker – index evaluating flicker
- VQIfrequency – index evaluating frequency
- VQIAll – index aggregating all active voltage quality parameters
What do you need to have or purchase?
- Voltage quality analyzers recording data at defined time intervals.
- Communication infrastructure for data transfer from analyzers to the data center.
- Server platform for running the VQI system (can also run as a virtual machine or shared with Vdip or FRA systems), OS MS Windows Server, database typically PostgreSQL (free), optionally MS SQL.
What are the approximate costs?
- VQI system license for small deployments with data from dozens of measurement points starts at approximately CZK 10,000 per analyzer and may decrease to about CZK 1,200 per analyzer with larger deployments.
- Costs for implementation work.
- Simultaneous acquisition with Vdip or FRA systems significantly reduces both license costs and VQI implementation costs.
What benefits does it bring you?
- Simple presentation of voltage quality status over large areas of the distribution system.
- Definition of areas with problematic voltage quality.
- Identification of emission sources and severity of their interference.
- Ability to optimize tap settings of distribution transformers.
- Data source for efficient network optimization and development.
- Efficient use of data from any voltage quality analyzers or databases where continuously measured voltage quality parameters are concentrated.
