Gero Di Piazza
Electricity in war-torn Macedonia is produced almost entirely from domestic natural resources lignite and hydropower. Six major hydropower plants, delivering 90 per cent of the hydropower and 30 per cent of the country’s installed generation base, were built in the 1950s and 60s. Although the plants have been well maintained, much of the equipment has deteriorated. This, along with the fact that no new parts are available, has spurred the state-owned Electric Power Company of Macedonia (Elektrostopanstvo na Makedonija ESM) to undertake a $44.6 million hydropower plant rehabilitation, energy management system and distribution project to avoid further system losses.
The project is divided into five packages, and Westinghouse International Process Control Corporation, part of Emerson Process Management, participated in the tender for package four, which involves revamping six hydroelectric generation plants. The US company was involved in a five-way battle with engineering experts such as VA Tech Hydro, a consortium of Koncar with ABB, Alstom Power, Voith Siemens and Tractebel Engineering International for the contract.
The Ovation Information and Control system will be installed to control data flow at the six Macedonian hydropower plants under the scope of ESM’s refurbishment project
The task in hand will require Westinghouse Process Control to carry out detailed project planning, engineering, co-ordination and management of the complete control system implementation. The company will design all equipment and integration in the control room, which will hold software installed and manufactured by Westinghouse. The responsibilities will extend as far as supplying all communication cables on local and plant level (field bus, plant bus) and all the auxiliary equipment and wiring.
The six power plants comprise Globocica (2×21 MW); Spilje (3×28 MW); Tikvesh (4×23 MW); and three in the Mavrovo Cascade Vrutok (4×37.5 MW), Raven (3×6.4 MW), and Vreben (2×6.4 MW). Mavrovo has a total of 18 units with a combined capacity of 400 MW (See Table 2), and is expected to be completed by 2004.
The modernization, funded by the World Bank along with grants from the Japanese and Swiss governments, will allow Macedonia to sell its energy to the European market while supplying its own resources. The reconstruction and revitalization of the existing hydropower plants will extend their operational life for a further 30-35 years by implementing up-to-date equipment and the company’s Ovation Control & Information System. This features vital equipment that monitors and controls the generation units at each site, external turbine and voltage controllers, and connection and co-operation with the National Dispatch Centre (NDC).
The system is designed to eliminate concerns about technological obsolescence and dependence on proprietary systems. Operating on a high-speed, high-capacity network, Ovation is the first system built completely to open industry standards, using commercially available desktop hardware and allowing easy integration of a customer’s existing IT products and components while maintaining process security. Hakan Erdamar, director, Westinghouse, Switzerland, adds: “[The Ovation system] performs automatic action of sequences for hydro-unit start-up, shut down, emergency shut down. The function for the automatic start/stop of the unit will be created in order to bring the unit from one operating condition to another, such as loading, synchronizing, running, but not synchronized, and standstill.
“Automatic loading and unloading of the unit will be built into the start/stop sequences. Start/stop sequences will consist of a number of steps and in each step the commands will be activated to different process objects. The next step will not be activated until the conditions of the previous one have been completely fulfilled.”
He continues: “Each step will be supervised and if any particular condition is not fulfilled within a specified time, an alarm will be activated and the actual step and the unfulfilled condition will be clearly indicated on the local VDU on the operator control station. Particular conditions and process status will be monitored and any missing condition will be indicated.”
Locally, PLC controllers located close to the process equipment are applied. They control the operation of dams and gates and communicate with distributed control system by radio modems. All new control systems communicate with National Dispatch System in Skopje using ICCP protocol. NDC receives information about the status of each power unit and generates load demand signals.
With this system, the operator can easily enter water management objectives. Based on market conditions and bidding activity, an hourly load schedule for the day ahead is established by Energy Supply and Marketing and entered into the system by the operator. Periods when automatic generation control operations are prescheduled also are entered. The optimization software accepts the water management objectives, hourly schedule, and dispatch mode, and continuously sets unit load demands.
An incremental/decremental loading application function addresses real-time dispatch, as called for by the market. The company’s software designs are platform independent, and easily upgraded, using standard-based networks and the latest computer technology. Through secure Internet-based channels, ESM plants and corporate personnel can access the system from any desktop, using familiar software tools to view site operation and performance data, thereby allowing site-wide co-ordinated control capabilities.
Many substations will be refurbished as part of the Macedonian overhaul programme, which will be completed by 2005
Officials at Westinghouse boast that as much as a 40 per cent reduction in maintenance costs, and as much as ten to 25 per cent reduction in the number of forced outages caused by control related events can be achieved in thermal power plants. The challenge now is to pass these statistics over to hydropower plants.
Erdamar notes: “At the moment there are no similar data for hydro applications of Ovation. We cannot simply transfer the numbers from thermal to hydro, especially those for process reliability.” He added: “Implementation of modern Distributed Control Systems like Ovation can not only reduce the system maintenance costs (even as much as 40 per cent), but also significantly increase the reliability of the control process. Both effects mean big savings to the plant.”
Also on the hydro agenda, but separated in a different project lot is Boskov Most, which is scheduled to have an installed capacity of 45 MW and an annual production of some 155 GWh. Costs of the project are put in the region of $54.5 million. Next will be the Matka 2 part of the complex of hydro power plants sited on the Treska River, which will include Kozjak, Matka 2 and Matka 1. The plant is due to have an installed capacity of 33 MW and an annual production of 53 GWh for a cost of approximately $40 million. The biggest hydropower project is Cebren, which will cost around $336 million, has an installed capacity of 245 MW, producing 300 GWh a year.
Data shows that Macedonia produces over 6.4 TWh of electricity per annum and consumes over 6 TWh. The country imports 75 GWh. But the one area that Macedonia is eager to improve on is its electricity exports, which is currently just over 30 GWh. Andrezej Chowanski, Director for Marketing and Sales, Westinghouse Process Control Europe, Poland said: “With Macedonia’s [war-savaged] situation, any progress is good progress in terms of export expansion. The war has made a big financial impact on what it can and cannot spend. The country will be targeting Yugoslavia, Kosovo and Bulgaria as the initial step after completion.”
The estimated two-year task will require an overhaul of technology. Starting with the units, replacements and construction is expected on the following equipment: HV and MV substations, AC/DC, uninterruptable power supply (UPS) auxiliaries, 0.4 kV equipment, dam hydraulic system, drainage system, fire protection system, cooling system and a security system. The plant control equipment will consist of one main computer, operator station, engineer station communication, plant communication network, clock-synchronization unit and mimic board.
ESM’s plant manager, Ivan Kukovski, made a basic three-point outline for the on-site equipment to be installed:
Replacement of the existing analogue control by modern, digital control systems to perform functions for:
- Data acquisition
- Unit control
- Plant control
- Substation control
- MMI (located at plant and unit levels) process optimization (load allocation, pond control)
- Communication with the NDC using
Replacement of the existing relay electrical protections by modern microprocessor protection equipment for:
- Generator-transformer unit protection
- Protection of 35 kV, 110 kV, 220 kV substations (bus-bar, breaker failure and line protections).
Replacement of the existing low voltage auxiliaries by new technical equipment:
- Batteries and rectifiers
- AC auxiliaries
- DC auxiliaries.
The first of Kukovski’s plan is the Vrutok unit, which will need a new 110 kV circuit breaker. The substations will consist of one 220 kV feeder, eight 110 kV feeders and twelve 35 kV feeders. An emergency hydro unit will also be supplied, which will consist of turbine governor, voltage regulation and inlet valve). The plant will hold three AC supply and control boards, two 220 V DC supply batteries and charger and a 48 V DC battery and charger. It will also have a 10 kVA UPS system in place. The project is expected to be completed by year-end.
The Ovation system will aid communication from the field sensors to the main computers and the plant operators
Raven will require a new 35 kV circuit breaker. The substation is to have three 35 kV feeders. Also supplied will be two AC supply and control boards, a 48 V DC with battery/charger and a UPS system. The completion stage will look at 2003.
Vreben will also take on a 35 kV circuit breaker; its substation will consist of three feeders. Two AC supply and control boards have been pencilled in along with a 220 V DC battery/charger, a 48 DC battery/charger and a 5 kVA UPS system. The finalization year is 2004.
Tikvesh will implement a 110 kV circuit breaker. The substation will need one 110 kV feeder and six 35 kV feeders. Three AC supply and control boards are required with one 220 V battery and two chargers, one 48 V battery with two chargers, and a 5 kVA UPS to be online by 2003.
Lastly, Spilje and Globocica are almost identical in terms of equipment needs. Both substations need six 110 kV feeders and seven 35 kV feeders. Three AC supply and control boards are needed for Spilje and two for Globocica. Both will need one 220 V battery with two chargers and one 48 V battery with two chargers along with a 5 kVA UPS system. Spilje is targeting 2004, while Globocica pinpoints 2003 as a completion date.
Because of the age of the equipment, outages are expected to increase unless the units are rehabilitated, says an official from ESM. She adds: “As a first approximation, EEF assumed that one power plant out of six would be out of operation one month per year, if no rehabilitation were undertaken and that this risk would be reduced by two thirds if the plants were rehabilitated.”
This implies that, as a result of rehabilitation, the lost generation from outages of hydropower plants would be reduced by about 7 GWh per year. If in fact this electricity was unserved energy (i.e. it resulted in brown outs or black outs) the value would be very high. This assumes that the electricity would have been replaced by electricity generated from thermal power plants or by swaps with neighbouring countries.
The reconstruction of the turbines at the hydropower plants add significantly to the generating capacity of these plants by increasing the efficiency with which the water from the penstocks is used. This additional capacity will add to system reserves and improve primary and secondary regulation. The entire five-packaged project, which started in 1998 and is on schedule to finish by 2005, would be seen as a world role model by countries that do not exploit their hydropower potential. Macedonia will be producing 90 per cent of its electricity output through hydropower alone, meaning an obvious reduction in carbon dioxide emissions due to reduced thermal generation.
Westinghouse’s $9 million contract, one of the biggest of its kind in Macedonia, will attempt to increase the reliability and efficiency of hydropower generation. The modernization will increase the generating capacity of the six plants thus helping to meet Macedonia’s electricity demand and avoiding the likelihood of brown and black-outs.
The increase in hydropower generation due to increased efficiency of the turbines is estimated to achieve as much as 13.7 GWh per year. This is a gain of 1.9 per cent on average for the six plants and assumes an average year with 730 GWh of hydropower generation from these plants. This additional power would be largely peaking power and generated in the winter when the demand for power in the Republic of Macedonia is at its peak due to the heating load. It would replace either power generated from thermal power plants in Macedonia or power swaps with neighbours.
The overall achievement, says James Moose, World Bank task team leader, is that the project will benefit largely from decreasing the cost of operation and increasing reliability and safety. He adds that the major benefits from the hydropower plant rehabilitation component is split into three sections. Firstly, the increased hydropower generating capacity will lead to improved primary and secondary regulation, lower costs and emissions, reduction in hydropower plant operating costs and reduced likelihood of hydropower plant and system outages.
Secondly, the major benefits from completing the energy management system will be improved generation scheduling, enhanced system reliability and security, reduced operating and maintenance costs. The system will also help to facilitate ESM’s reconnection to the West European Electricity network, UCPTE.
Finally, as the overall package deals with the distribution components, the main benefit is a reduction in the high losses the current distribution network is experiencing.