**5. Conclusions**

The capacitive coupling models lead to an accurate approximation to the response of distribution network against the frequency spectrum imposed by the switching action of the converters at DG. This approximation is not feasible using simplified models because of the bandwidth limitation for high frequencies.

According to the distribution network under study, a high ground current contribution to grid provided by DG has been detected. Therefore, some preventive actions can be applied to network design stage in order to solve this problem, such as:


Fig. 15. Simulation result of the distribution network: (a) current waveform and (b) FFT analysis of the waveform obtained, at node 5.


#### **6. References**

276 Power Quality Harmonics Analysis and Real Measurements Data

Although voltage waveform meets standard regulations, it has been observed an important ground current contribution through the admittance of the underground cables. The ground voltage waveform has a considerable magnitude with peaks reaching 7 V, as shown in Fig. 14. Likewise, the ground current measurement due to the capacitive coupling of these

The fundamental component of the current waveform is 313 mA, and the THD of this waveform is 190.78%. The most predominant harmonic components are harmonic 72 with 145.22% of the fundamental component, followed by harmonic 70 and 76 with 98.29% and

3.80 3.81 3.82 3.83 3.84 3.85 3.86

Time (s)

Fig. 14. Simulation result of the distribution network ground voltage waveform at node 5. These observations point to the importance of controlling the capacitive coupling in load installations connected to networks with DG. Otherwise, end users equipments can be exposed to malfunctioning and lifetime reduction due to the capacitive ground current.

The capacitive coupling models lead to an accurate approximation to the response of distribution network against the frequency spectrum imposed by the switching action of the converters at DG. This approximation is not feasible using simplified models because of the

According to the distribution network under study, a high ground current contribution to grid provided by DG has been detected. Therefore, some preventive actions can be applied



underground cables is also significant as shown in Fig. 15.

Moreover, GPR can reach values of unsafe work conditions.

to network design stage in order to solve this problem, such as:

reduces the capacitive ground current in the installation.

GPR between PV modules and ground is minimized.

bandwidth limitation for high frequencies.

58.75%, respectively, as shown in Fig. 15a.


**5. Conclusions** 

Voltage (kV)


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*Edited by Gregorio Romero Rey and Luisa Martinez Muneta*

Nowadays, the increasing use of power electronics equipment origins important distortions. The perfect AC power systems are a pure sinusoidal wave, both voltage and current, but the ever-increasing existence of non-linear loads modify the characteristics of voltage and current from the ideal sinusoidal wave. This deviation from the ideal wave is reflected by the harmonics and, although its effects vary depending on the type of load, it affects the efficiency of an electrical system and can cause considerable damage to the systems and infrastructures. Ensuring optimal power quality after a good design and devices means productivity, efficiency, competitiveness and profitability. Nevertheless, nobody can assure the optimal power quality when there is a good design if the correct testing and working process from the obtained data is not properly assured at every instant; this entails processing the real data correctly. In this book the reader will be introduced to the harmonics analysis from the real measurement data and to the study of different industrial environments and electronic devices.

Photo by FactoryTh / iStock

Power Quality Harmonics Analysis and Real Measurements Data

Power Quality Harmonics

Analysis and Real

Measurements Data

*Edited by Gregorio Romero Rey* 

*and Luisa Martinez Muneta*