1DISTRIBUTED GENERATION, BENEFICIAL OR DETRIMENTAL TO GRID SECURITY, FROM THE SOUTH AFRICAN SYSTEM OPERATORS PERSPECTIVE Written and published for 5th South African Cigre Regional Conference 2005 by J H Muller, National Control, System Operator, Eskom Holdings, P O Box 103, Germiston, 1400, South Africa

1. SUMMARY The South African System Operator, which forms part of Eskom Transmission Division, is responsible for the management of the South African Interconnected Power System. This power system currently consist of more than 27300 km of transmission lines, not taking into account the underlying distribution system and 20 PowerStation’s with the generating capacity of +-36000 MW. The role of the System Operator is to ensure continues quality supply of power to a range of customers, through managing the system in an economically, reliable, stabile and secure manner. Due to unpreceded load growth and a shift in focus to environmental issues in South Africa and the surrounding regions, as well as the long distances power needs to be transported, the current Interconnected Power System is becoming severely strained. This situation makes the effective management and operating thereof a complicated and difficult task. This is worsened by the fact that some terminal equipment is coming to the end of its effective life span and would need replacement or upgrading within the near future. Well planned, well placed Distributed Generation, connected to the Grid near load centres, forming part of an Energy Market, will make it possible to not only relief the ageing power system, but also offer effective solutions to current constraints on the South African Interconnected Power System. The System Operator due to its world class experience and skills in effectively managing one of the biggest interconnections in the world, has an important role to play in co-ordinating the development, implementation and operation of this South African Interconnected Power System, so that it supports the successful introduction of these new forms of generation. 2. DEFINITION FOR DISTRIBUTED GENERATION For the purpose of this paper and in part based on the Cigre Definition, Distributed Generation can be seen as generation from 10 to 100 MW. This can be an individual generator or modules with a combined power output of 10 MW and more, installed at or near the load centres, connected to the transmission or distribution grid and could be synchronised with the system at a frequency of 50 HZ. This does not include any Demand Side Management load reduction agreements or contracts. The responsibility of the System Operator is to ensure continuity of supply to its customers. Demand Side Management agreements result in un-served energy, which lead to the sum of the loss of income from not delivering the supply and the payment to customers for reducing their load in times of high load, which of course affects the price of electricity to the consumer. This paper will focus on Distributed Generation and not Distributed Resources, which includes Demand Side Management. 3. SOUTH AFRICAN INTERCONNECTED POWER SYSTEM

Power System Profile The South African Interconnected Power System is a combination of generation, transmission, distribution and rural electrical networks. The majority of the present generation capacity is concentrated in the Mpumalanga area due to high deposits of coal. This generation hub is situated to the north east of where most of the load is situated known as the Central region. Additionally power is transferred over long distances southwards to supply the Eastern, Southern and Western regions, which makes up approximately a third of the total system demand. Figure 1 indicates the load centres on the Interconnected Power System and relevant transmission corridors between them.

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Taking the maximum demand of the South African IPS as 34210 MW (measured 13/07/2004), this means that +- 11000 MW needs to be transferred south to supply this remote load. Transferring this power over distances of up to 1500 km on 275, 400 and 765 kV transmission lines results in losses equal to and higher than a 615 MW generator, depending on the generation profile on the Power System at the time. This is close to 2% of the total demand on the Power System. Although some generation units are situated in the Eastern and Western regions, it is not enough to satisfy the required demand in these distant areas, and power needs to be transported in from Mpumalanga generation hub. Whenever there is a change in the generation that is situated in these distant regions or some of the interconnections are on outage or lost, it severely impacts on the ability of the transmission network to transport power due to stability constraint conditions that exist. This decrease in generation or the loss of an interconnection will increase the transfer in power on the remaining lines, which in turn will increase the need for reactive power, which may cause voltage instability. Voltage instability may then be the cause of a voltage slide or collapse of the relevant network. Voltage collapse takes place over a period of time, ranging from a few minutes to a couple of hours, and can give clear warning signals. The System Operator may have a limited amount of time to implement corrective actions, such as starting generation, returning the interconnection back to service, or reducing load in the effected areas to relieve transfers on transmission lines. A further problem when additional generation is lost in these remote regions is angle instability. Angle instability will move the effective network into an unstable condition. This unstable condition could be aggravated by any disturbance, which may result in the separation of the region from the Interconnected Power System. Normally such an incident will take place within a few seconds, with little or no warning, giving the System Operator, no or very little time for corrective actions. So the current practice is to implement preventive measures before the system moves into a angle unstable condition, through the use of generation, load reduction or load shedding, which will ensure the system operates within previously established stability margins. Currently there is a very limited amount of Distributed Generation connected to the Interconnected Power System. These are mostly neighbouring countries, municipalities and big consumers. Some of the Distributed Generation that is operated in parallel with the IPS is found at Cape Town City Council, Tswane City Council, Sasol Chemical Industries, Transkei, Lesotho and Mozambique. These range from standby units, self-supply, peaking, co-generation (steam) and grid supply. Types of generation currently in use range from diesel, gas, coal and hydro, with an almost insignificant amount of wind and solar. Another important factor is the current economic growth in South Africa and neighbouring regions. This can almost be directly linked to the growth in electrical demand, and it has definitely contributed to reducing the excess generating reserve and is constraining the transfer capability of the South Africa Interconnected Power System drastically. It is predicted that Eskom may run out of capacity by 2007, but it may be more probable that Eskom will be unable to meet peak demand in 2006. Presuming that it takes between 10 to 15 years to build a new base load power station, it seems very unlikely that a new station will be build within the near future, and it may be a viable option to start looking at alternative solutions. It needs to be mentioned that some of the mothballed power stations will be returned to service during the next 2 to 3

3years. But at that time the returned generation will simply help reduce the shortage that may exist at that time. 4. DRIVERS FROM ELECTRICAL GRID FOR DISTRIBUTED GENERATION IN SOUTH AFRICA As can be deducted from above the South African Interconnected Power System needs to be strengthened and additional generating capacity will be needed within the 1 to 2 years, to ensure a reliable and secure electrical supply to facilitate further economic development. Without taking the Governments stand on renewable energy or world drive for alternative and clean energies into consideration, and just looking at the current and future challenges that Eskom will be facing. It is almost without doubt that Distributed Generation could become an important and viable solution to current and future challenges facing the South African power industry.

Distributed Generation can have many faces and work with a wide range of prime movers, such as gas, fuel-oil, nuclear, wind, hydro, tidal wave, ocean currents and heat from the sun. When looking at the geographic’s of South Africa it becomes clear that we have an abundance of renewable energies in the regions where we actually experience transmission and generation constraints. If this potential could be further developed it may not only defer the strengthening of the transmission system but also the building of new power stations.

As can be seen from figure 2, the South African wind map there is prevalent wind conditions in the Eastern, Southern and Western regions of South Africa. If this proved technology could be further developed in this regions in large enough combinations of 50 to 100 MW, it will not only help reduce transfers on the

4transmission lines, but reduce losses by a large margin. Which in turn will mean a saving of generating capacity that was normally allocated to cater for these losses. Additionally it is becoming apparent on the Interconnected Power System with the unexpected high load growth that additional reactive resources will be needed within the near future to help support the transfer of the power to the consumer. Lack of reactive power impact on customer’s ability to maintain production processes and decrease the power factor of delivered power. It also influences the System Operators ability to ensure a secure and stable power system. As no margin for error is left, and the system may not be able to handle more than a single contingency successfully. By putting correctly designed Distributed Generation technologies in large enough quantities close to the main load centres, it will be able to supply the load with the required reactive power during high peak periods, relieving the main transmission system and ensuring that the most severe contingency could be managed successfully. 5. BENEFITS OF DISTRIBUTED GENERATION Over the last two decades the requirements of the Interconnected Power System has changed significantly. From a grid with a large margin of spare capacity supplying customers with the most basic of electrical needs, to a highly interconnected power system, supplying customers with the highest power quality requirements. Currently the Interconnected Power System with generation located far from its large load centres, have lost a large part of its ability to deliver quality electrical supply to the point the customer take their supply. This is where the benefits of Distributed Generation can be realised. The benefits of Distributed Generation in a well-developed Grid can be seen as:

• It is modular by design and does not rely on the economy of scale to be viable. • Lead-time from planning to commercial stage of Distributed Generation is short. • The advances in technology have resulted in much more energy efficient Distributed Generation

systems, some able to utilise renewable energy sources that can not be depleted. • Reduction or zero emissions, reducing pollution considerably. • When Distributed Generation is installed at or near the load centre, it reduces the power transfer on

the transmission or distribution lines. • When well designed Distributed Generation is close to the load it will improve the quality of supply

delivered to the customer. • Distributed Generation may also have the ability to prevent blackouts, or to reduce restoration time

in a blackout situation. • Distributed Generation near sensitive loads may reduce flicker, spikes and dips from system faults.

6. RISK THAT COULD BE ASSOCIATED WITH POORLY DESIGNED DISTRIBUTED GENERATION It should also be realised that poorly designed Distributed Generation can weaken the Interconnected Power System, or even contribute to an ensuing blackout. When Distributed Generation is installed in a weak network which use induction, rather than synchronous generators, it will not relieve the system, but put a considerable strain on the required power resources. In a case where such a weak system experiences a disturbance, the Distributed Generation itself may cause the collapse or blackout of the surrounding network. The reason being that induction generators consume reactive power when brought on line, and will amplify voltage depressions in peak times or during fault conditions (12). In most utilities world-wide Distributed Generation interconnection standards will require the Distributed Generation protection to be set so that it will disconnect from the grid when large disturbances occur. This negates any help such Distributed Generation could have had in helping to stabilise or relief a grid in disturbance or post-disturbance conditions (12). Another problem that is becoming evident is that many Distributed Generation owners on international grids do not take part in the energy market and is this not dispatched as per system or market requirements. We can take an example such as a large quantity of independent small windpower owners on an Interconnected Power System with mostly big coal-fired base load stations. Due to the winds intermittent prevalence, base load stations will have to be either pulled back or taken of load when al these small wind

5generators start supplying the grid when the wind is blowing. Most base load stations in South Africa is coal fired and takes a while to ramp up or down, and even longer to come on load after it has been taken off. This may result in low frequencies, which in turn may result in brownouts and in the worst case blackouts if the wind suddenly dies down. 7. MARKET AND MARKET BARRIERS FOR DISTRIBUTED GENERATION IN SOUTH AFRICA South Africa with its concentration of PowerStation’s around the coalfields in Mpumalanga and the necessity to transport power over long distances to load centres in the Eastern, Southern and Western regions of the country, offers viable opportunities to investors. The installation of Distributed Generation in these regions will reinforce and improve the security and reliability of the South African Interconnected Power System. Markets for DISTRIBUTED GENERATION In South Africa Markets can be created for Distributed Generation in the following sectors:

• Black-starting Capability • Island supply to essential loads, • Reactive power supply (ancillary service), • Peak shaving, • Deferred expansion saving payments, • Line loss reduction payments, • Transmission line transfer reduction payments, • Carbon credits payments, • Tax incentives for Alternative Energy generation, • Quality of supply payments.

MARKET BARRIERS The tree primary barriers internationally to the near term penetration of distributed power can be seen as cost and development status; lack of infrastructure; and lack of market conditioning and knowledge (9). In South Africa as in the rest of the world, the greatest barrier to the development of distributed power market, can be seen as the lack of awareness and understanding of the real advantages of Distributed Generation technologies among the government, energy planners, regulators, utilities and end-users (9). 8. CONCLUSION Distributed Generation could enhance the security and reliability of the South African Interconnected Power System, if the System Operator is allowed to be involved from the initial planning stage of future projects. The System Operator could help in advising on types and location of Distributed Generation according to system requirements. This will ensure the installed Distributed Generation have the biggest influence in reducing losses, improving security and reliability and help to defer some of the required expansions needed to enforce the Interconnected Power System to cater for the imminent load growth.

Additionally all the players in the South African energy market need to not only look at current incentives scheme’s, but also at tax breaks for Alternative Energies, payment to Distributed Generation owners for ancillary services and the change of current permitting requirements, procedures and regulations with regards to grid connections. It is with certainty that South Africa will have a shortage of generation in the next few years and this could be the best opportunity for introducing a bigger part of South Africa’s current generation mix with Alternative Energy technologies. Although thorough planning and co-operation from all involved is essential, an environment conducive to Distributed Generation investment, based on sound business and technological sense must first be created.

6 Lastly it is proposed that when such an environment is created and Distributed Generation projects are being build, that the Grid Code be amended to ensure Regional Control Centres appoint energy Schedulers for each regions installed Distributed Generation. These Regional Energy Schedulers will then need to work in close co-operation with the System Operator’s Load Dispatcher, to ensure a stable and secure South African Interconnected Power System is maintained and optimally managed.