The Southern African Power Quality Initiative:
Renewable Energy Integration- The Network Impact
The South African Government opened the renewable energy market in August 2011, with an associated flurry in activity. Shortly after opening the renewable energy market, the Grid Connection Code for Renewable Power Plants (RPPs) Connected to the Electricity Transmission System (TS) or the Distribution System (DS) in South Africa (RPP Grid Code) was published. This living document contains the requirements that RPPs must meet in order to connect to the South African power system and receive payment for power generated.
What is different when connecting RPPs?
On the surface, it appears that the connection and integration of renewable energy is a simple matter, since utilities have been designing and operating their networks for customers for many years. RPPs connect to utility networks just like customers do. Although the power flow has now reversed, the primary function of utility networks is to transmit and distribute electrical energy. However, the RPP Grid Code is a legal document applicable to RPPs. In the past, legal requirements were given to the utilities via licensing conditions and requirements were passed onto customers via connection agreements and contracts. These new “customers” now have licensing conditions of their own to meet.
This shift in the legislative requirements has changed the electricity market in South Africa drastically. There are now requirements for both the utility as well as the RPP.
Can utilities not do it alone?
Similar to the development of loads over the years, generators have also evolved from rotating machines to power electronics. Loads evolved from incandescent light bulbs, resistive heating elements and basic machines that are tolerant of potential poor power quality and have negligible impact there-on, to sophisticated power electronics and control systems that are very susceptible to poor power quality and cause power quality deviations.
Along with this, the power supply system has evolved into one of the most complex and interconnected systems that man has built.
Managing the performance of this system and quality of electricity provided is the responsibility of the utility (power system owner). However, they cannot do it alone; they need cooperation of all users as well, including RPPs.
Does South Africa not follow the same rules and processes as Europe?
No, they do not. Southern African networks have developed under different circumstances to the typical European network, very often with less capital available and significantly larger distances to cover. South Africa was a leader in the PQ field in the early days; just look at the NRS048-2 dip chart and definitions, which is still regarded as the best in the world. The South African PQ management principles are sound and intended to promote cooperation between utilities and their customers.
The SA Grid Code, as the legal framework, was developed with significant European influence, resulting in a more complex environment where RPPs become involved. Along with the financial and economic framework used for e.g. the REIPPPP, Grid Code compliance implies that the long-term evolution of the network is also taken into account. The expected future network developments are included using simplified network generalisation in order to limit technical and financial risks to both parties.
Do Utilities take any responsibility?
The power quality section of the SA Grid Code for RPPs has had a major overhaul in 2015. The requirements are spelt out much clearer now and embody the intention of optimal solutions whilst working together. It requires that all parties play an active role in specifying additional and specific requirements (such as the apportioned emission limits) and assessing the expected impact both pre- and post-connection over the longer term. Grey areas still exist, which necessitates close cooperation by technical personnel.