**2.3. IEC standard 61000-3-6 harmonic distortion limits**

IEC Standard 61000-3-6 specifies the allowable harmonic distortion limits as shown in **Table 3** [4].



**Table 1.** Voltage THD limits according to IEEE 519-2014 [3].

**Table 2.** Current distortion limits according to IEEE 519-2014 [3].


**Table 3.** IEC 61000-3-6 voltage harmonic limits [4].


Measurements were conducted using Hioki 3196 Power Quality Analyzer Meter [8]. The current clamps were installed on transformer one (TX1). Ten-minute average values were recoded over a period of 1 week starting from 17th of January 2012. This study was part of power quality study in MIS [9–12]. A summary of measurements is presented in **Figure 2**.

Harmonics Temporal Profile in High-Voltage Networks: Case Study

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**Figure 2.** Summary of THD measurements at grid station a. (a) Voltage THD (b) current THD.

**Figure 1.** Main interconnected system [7].

**Table 4.** Voltage THD limits according to national Omani codes.
