Recently NMi started a new project to examine whether smart electricity meters are possibly affected by wideband disturbances in the grid, in the frequency range 2-150 kHz. This project is ordered by Netbeheer Nederland, the organisation of Dutch grid operators and it is executed together with the Dutch national metrology institute VSL.
End 2016 the University of Twente published results of an investigation with smart electricity meters in the IEEE Electromagnetic Compatibility Magazine. The article presented results of static electricity meters being sensitive to exposure of specific wideband disturbances in the current, which may be caused by power electronics in commonly used equipment. The investigation was performed in a laboratory while using a power supply, dimmers and different types of lamps to generate disturbed conditions.
Although the Dutch grid operators are convinced that the real conditions in the grid are much better than the simulated lab conditions by the University of Twente, Netbeheer has decided to start a separate project to do further examination. This project has the following 3 objectives:
1) Determination of the real disturbances in the grid
2) Determination of the possible effects to meters accuracy under those real conditions
3) Root cause analysis of the effects
Disturbances in the grid
During the first stage measurements are performed in order to determine how the real disturbances look in the grid. This will be executed at various places in the network, where also various types of electronic equipment are used, which may cause local disturbances. After that, the measurement data will be analysed, which will result in a set of reference signals which reflect specific characteristics of the disturbances.
During the second phase a setup in the laboratory is developed, which is able to reproduce the set of disturbance signals simulating the situation in the field. Then, a number of electricity meters will be exposed to those disturbance signals. The influence on the meter accuracy will be determined. Also a recommendation to standardisation committees will be prepared, in order to arrange a standardised test which can be applied commonly.
Root cause analysis
During the third stage possible error mechanisms for different measuring principles in electricity meters will be investigated. A possible root cause analysis will be performed with several types of electricity meters.
For this project both NMi and VSL cooperate closely together with the grid operators Stedin, Liander and Enexis. It will lead to more precise knowledge about the real disturbances being present in the grid and whether electricity meters function accurately indeed under those conditions.