**2.4. Harmonic distortion limits according to Oman's national regulations**

Allowable harmonic distortion levels in Oman are dictated by the grid code [5] and the distribution code [6] for high-voltage and medium-voltage networks, respectively. The grid code specifies that the maximum THD should not exceed 2% with no individual harmonic greater than 1.5% for transmission networks (220 and 132 kV). The distribution code dictates that the maximum THD in distribution networks (66, 33 and 11 kV) systems should not exceed 2.0% with no individual harmonic greater than 1.5%. For low voltage line (415 V), the total harmonic distortion limit is 2.5%. Individual harmonic distortion level should be below 1.5% for both transmission and distribution networks (**Table 4**).
