**9. Acknowledgments**

86 Power Quality Harmonics Analysis and Real Measurements Data

used. All the data were reliable in this case due to the high magnitude of the interharmonic

**IH freq (Hz) Customer 1 Customer 2 Customer 3 151 Hz** 100 100 100 **271 Hz** 100 100 100 Table 5. Reliable Snapshots [%] According to the Quantization Error Criterion for System #2 Table 6 shows the correlation results for the locations, revealing that the interharmonic

**IH freq (Hz) Customer 1 Customer 2 Customer 3** 

The power direction results are shown in Table 7. In this case, the data was deemed reliable

**Location of measurements IH frequency [Hz] Sign(***PIH***)** Customer 1 151 +

Customer 2 151 +

Customer 3 151 -

The information for sign(*PIH*) reveals that the sign(*PIH*) of Customer 3 is negative, so that Customer 3 was the source. In this case, the angle displacement between the voltage and current was not observed to fluctuate at around ±π/2 radians. Therefore, the power

This chapter investigated the reliability of the data used for the power quality disturbances assessment. The main applications were to estimate the network harmonic impedance and to determine the interharmonic source. A set of criteria to state about the data reliability was

Table 7. Power Direction (at Interharmonic Frequencies) Results for System #2

presented. They consisted in proposing thresholds for the following parameters:

271 +

271 +

271 -

voltage and current had a high degree of correlation at the three customer loads.

**151 Hz** 0.93 0.88 0.98 **271 Hz** 1.00 1.00 1.00

Table 6. Correlation Results for System #2

direction method can be used with full confidence.

components.

**7.2 Results** 

by all reliability criteria.

**8. Conclusions** 

 Frequency-domain coherence; Time-domain correlation; Quantization error; Standard deviation;

The author gratefully acknowledges the financial support provided by Hydro One to partially cover the publication of this chapter and also their encouragement into improving this research work.

The author also expresses his gratitude towards Mr. Edwin Enrique Nino from ATCO electric for providing the several data sets of the network harmonic impedance collected in many Canadian utility sites, for processing the data and providing the presented results. Thanks are also extended to Mr. Hooman Mazin for providing part of the statistical analysis used in the network harmonic impedance data filtering application.

Finally, the author expresses his appreciation to Prof. Wilsun Xu for his supervision, technical contributions and high-level advices.

## **10. References**


**3** 

Jarosław Łuszcz

*Poland* 

*Gdańsk University of Technology* 

**Voltage Harmonics Measuring** 

**Issues in Medium Voltage Systems** 

Voltage harmonic distortion level is one of the significant parameters of power quality in power system. Numerous problems related to voltage and current harmonic effects for contemporary power systems are commonly observed nowadays. Levels and spectral content of voltage distortions injected into electric power grids are tending to increase despite the fact that the acceptable levels are determined by numerous regulations. Voltage distortion assessments, especially in middle and high voltage grids, are usually based on measurements in which voltage transformers are commonly used. The transfer ratio of a voltage transformer fed by distorted primary voltage with harmonic components of frequency higher than fundamental can be different for high frequency components in

During the last decades primary problems related to voltage distortions have been usually encountered in frequency range up to 40th harmonic, mostly in LV grids. Nowadays, due to the evident increase of the overall power of nonlinear power electronic loads connected to grid and higher modulation frequencies widely used, distorted voltage propagates deeply

This chapter presents problems of voltage harmonic transfer accuracy through voltage transformers which are usually used for power quality monitoring in medium and high voltage grids (Kadar at al., 1997, Seljeseth at al., 1998, Shibuya at al., 2002, Mahesh at al., 2004, Yao Xiao at al., 2004, Klatt at al., 2010). A simplified lumped parameters circuit model of the voltage transformer is proposed and verified by simulation and experimental investigations. A number voltage transformers typically used in medium voltage grid have been tested in the conducted disturbances frequency range up to *30 MHz*. The obtained results prove that broadband voltage transfer function of the voltage transformer usually exhibits various irregularities, especially in high frequency range, which are primarily

Frequency dependant voltage transfer characteristic of voltage transformer induces extra measurement errors which have to be taken into account in order to achieve desired final

Classical voltage transformer (VT) is a two or three winding transformer with a relatively high transformation ratio and low rated power, intended to supply only measuring inputs

relatively high accuracy required for power quality monitoring systems.

**1. Introduction** 

comparison with the fundamental frequency.

associated with windings' parasitic capacitances.

**2. Circuit modelling of voltage transformers** 

into MV grids and goes evidently beyond frequency of 2 kHz.

