Dear Mohammed,

According to IEEE-519 standard, for current THD (THDi) it is depending on short circuit current and for voltage THD (THDv) it is depending on voltage level. you can find them in literature (e.g. POWER ELECTRONICS HANDBOOK, by Prof. Rashid)

Best Regards

Mohammed,

Saeed has mentioned the IEEE standards. But individual countries may have different standards to meet, and that too for different load types.

Better check for the specific national standard with reference to type of load.

-Sanjay