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Power Quality Guideline for Renewable Power Producers

At the South African Grid Code Industry Expert Team (IET) meeting on 13 December 2015, the long-awaited Power Quality (PQ) Guideline for Renewable Power Producers (RPPs) was finally approved.

Development started in 2013, when it became clear that the Grid Code requirements for PQ was unclear. It focuses on harmonics, but unbalance and flicker aspects were added towards the end of the development.

Key changes are the following:

  • The three-times impedance rule is demonstrated a bit more clearly, showing the relationship between voltage and current harmonics.

  • Harmonic current is regarded as the compliance measure for harmonic emissions.

  • Harmonic current that is absorbed by the RPP installation will not be regarded as an exceedence, even if it exceeds the emission limit.

  • Very little guidance is provided on proving that harmonic current is absorbed, but the CIGRE C4-109 method seems to be acceptable.

  • A Group Harmonic Distortion criterion was added, allowing some harmonics to exceed the limit by up to 50%.

  • Generic emission limits have been provided for RPP smaller than 5 MVA.

NOTE: The CIGRE C4-109 method does not always give clear-cut answers.

Some concerns still remain, e.g. the enforcement of the three-times impedance rule, especially in view of the low fault levels at many installations. I do expect further developments will happen as we gain more experience.

For now, it is a massive step forward for the Renewable Energy sector in South Africa. Well done to all who participated in die working group!

Contact us if you have any comments on questions.