Sarah Rönnberg

Standards for supraharmonics (2 to 150 kHz)

There is a serious interest from the international standard-setting community in knowledge about voltage and current distortion in the frequency range 2 to 150 kHz, referred to as supraharmonics. At the same time, research is ongoing at a number of locations, but the knowledge about supraharmonics remains limited. This paper compares some of the properties of harmonics and supraharmonics. An increase in supraharmonics for individual devices is observed in association with a decrease in harmonic emission (i.e. below 2 kHz). A proposal is made for setting limits in this frequency range. The proposal is based on existing standards and is meant to be for discussion. The authors strongly encourage an open discussion about the proposed limits. There are a number of differences between harmonics and supraharmonics that are not covered by the proposed set of limits. A substantial amount of further research is needed to extend the standard framework for supraharmonics such that this can be covered by standards.

Interaction Between Narrowband Power-Line Communication and End-User Equipment

This paper discusses some of the electromagnetic-compatibility issues concerning the use of power lines for communication. Based on a series of measurements performed in a laboratory environment and in the field, five different types of interactions between communication and end-user equipment are distinguished. Measurement examples are shown for several of these types. It is concluded that the creation of a low-impedance path by end-user equipment is the main cause of interference.

Harmonic emission before and after changing to LED and CFL — Part I: Laboratory measurements for a domestic customer

This paper presents an investigation after the impact on a number of power-quality parameters due to the change from incandescent lamps to energy saving lamps like CFL and LED. The measurements were conducted in a full-scale laboratory model with ordinary household equipment connected, thus simulating an ordinary domestic customer. Incandescent lamps have been replaced in stages by CFL and LED lamps. The CFLs and LED lamps will contribute to an increase in current distortion but the amplitude of the harmonics is quite low so the change of lighting will only have a minor effect on the total current harmonic distortion. It is also shown that the (total) power factor is not a good indicator to compare the impact of different loads on the system.

Future work on harmonics - some expert opinions Part II - supraharmonics, standards and measurements

A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. Some of the issues discussed at that workshop are presented in this paper and its companion paper. In this paper the following issues will be addressed: the appearance of emission at higher frequencies (supraharmonics); the need for new and improved standards; measurement issues and data analysis.

Harmonic emission before and after changing to LED and CFL — Part II: Field measurements for a hotel

This paper shows the results of measurements performed with a medium-sized hotel in the North of Sweden. The harmonic emission and other parameters were measured before, during and after a replacement of all incandescent lamps with energy saving lamps, both compact fluorescent lamps (CFLs) and light emitting diodes (LEDs). it was not possible to see any major difference in harmonic spectrum before and after the replacement. The reduction in power factor that was observed was completely due to the reduction in active power.

Future work on harmonics - some expert opinions Part I - wind and solar power

A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. The results of this discussion are summarized in this paper and some of the issues are discussed in more detail in this paper and in its companion paper. This paper discusses emission from wind and solar power as well as advantages and disadvantages of active and passive filters.

Harmonic and interharmonic distortion due to a windpark

This paper discusses two aspects of the impact of windparks on the waveform distortion in the power system: emission and resonances. The paper gives a general overview of the emission and shows measurement results from a small but modern windpark connected to a 10-kV feeder and estimates the need for network strength to limit the resulting voltage distortion. The paper also gives a general overview of harmonic resonances associated with windparks and illustrates this by means of two numerical examples. Important conclusions from this paper are than harmonic resonances are more likely to be a concern that the emission from windparks, and that the interharmonic emission and the emission at non-characteristic harmonics are more prominent than with existing installations.

Harmonic emission before and after changing to LED lamps — Field measurements for an urban area

The paper presents measurements performed in an urban area in the north of Sweden with two individual houses and on LV side of the distribution transformer supplying these two and ten more houses. Measurements of harmonic and interharmonic groups were performed before and after replacing all existing (mainly incandescent) lamps in all 12 houses with LED lamps. The total power of all lamps was reduced from approximately 2300 W to approximately 450 W, per house. All new lamps were low-power-factor lamps. The paper shows the variations of the most important harmonics with time and relevant spectra before and after the replacement. The emission during the evening hours is studied in specific detail. Despite the low power factor of the individual lamps, no change in emission due to the lamps has been observed, neither for any of the two individual houses nor the distribution transformer supplying all 12 houses.

A study about harmonic interaction between devices

This paper presents an analysis of current emission from low-voltage appliances in the frequency range from 2 to 150 kHz. The current to an electric vehicle is measured for different connection of other devices (LED lamp, microwave oven, TV) showing the presence of primary and secondary emission. The paper shows that the presence of a neighboring device can have a strong influence on the emission.

Power Quality Concerns in Implementing Smart Distribution-Grid Applications

This paper maps the expected and possible adverse consequences for power quality of introducing several smart distribution-grid technologies and applications. The material presented in this paper is the result of discussions in an international CIGRE-CIRED joint working group. The following technologies and applications are discussed: 1) microgrids; 2) advanced voltage control; 3) feeder reconfiguration; and 4) demand-side management. Recommendations are given based on the mapping.