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The generation of electricity in modern power stations involves engineering of massive proportions. The power station is a world of its own, vastly different in scale from everything else. The race is on for greater efficiency and minimum costs. By BRYAN MAHER Prior to the early 1950s, Sydney's power stations were built close to the load centres. Predominant loads were the city buildings, electric trams, trains a nd inner suburban homes and industries. The power technology of that time could not transmit large quantities of electricity over great distances. Therefore, power stations at Pyrmont, Ultimo and White Bay were built almost under the shadow of the Harbour Bridge and supplied the city using short 6.6kV and 1 lkV cables . Bunnerong station extended the Sydney County Council's capacity, feeding power to the city and suburbs via llkV and 33kV mains. The sites chosen were close to ample supplies of cooling salt water: Sydney Harbour and Botany Bay. Fuel costs The drawback of these locations was that coal had to be carried by rail over great distances from mines at Lithgow and the Illawarra coast [any coal supplies below Sydney are at great depth - more than 1000 metres down). A similar situation appeared in other Australian cities . Brisbane had power stations built at the intersection of Ann and George Streets in 1899, at William Street in 32 SILICO N CHIP 1912 and New Farm in 1938 - all beside the Brisbane River. Coal was shipped to them by riverboat from Ipswich. In those days, the high cost of electricity was due to: (1). expensive transport of coal; and (2). the low thermal efficiency of boilers and turbines. There had to be a more economical way! The answers came in the development of long distance high voltage power lines, bigger and better boiler/turbo-alternator units, and cheaper and shorter coal transport. Today, very high voltage transmission lines can carry vast amounts of electrical energy far more cheaply than the raw energy in the form of coal can be carried by rail. This statement applies for distances of up to 1000km. The cost per kWh [kilowatt-hour) can be further reduced by using very large boilers, turbines and alternators. The resulting strategy has been to locate large power stations close to the coal mines and to send the generated electricity by overhead lines to the cities, whatever the distance. If a cooling water supply is also available, that's an extra bonus. If not, then a water supply and cooling towers must also be constructed. The thermal efficiency of these heat/steam/mechanical rotational energy conversions is increased by the use of very high steam pressures and temperatures - up to 600°C, which is well above the melting point of many common metals [tin, lead, zinc) and approaching that of magnesium or aluminium! To be economic, such installations must be on a vast scale. For minimum cost per generated kWh, modern power station design therefore favours having just a few very large turbo-alternators, with ratings of between 600MW (600 megawatts) and 1.5GW (1500 megawatts or 1.5 gigawatts) being common. Compared to these figures, older machines seem diminutive. The Ultimo power station had alternators as small as lOMW, while the four 50MW generators installed at Pyrmont in 1952/55 were considered huge in those days. The first Brisbane power station in 1899 was rated at 45kW and the 1912 William Street Plant at 2.5MW, while New Farm in 1928 contained units each rated at l0MW. As Australia grew, newer and bigger power stations were provided. And this trend shows no sign of stopping. Eraring power station When it was completed, Eraring was the largest power station in Australia, generating 2.64GW [gigawatts) of electricity which feeds into the NSW state grid system. Eraring on its own could supply 10 cities the size of Newcas- RIGHT: LOCATED NEAR MUSWELLBROOK in the Upper Hunter Valley of NSW, Bayswater Power Station generates 2.64GW of electricity from four 660MW turbo-generators. Along with Eraring, it is the biggest power station in Australia and uses four huge natural-draught cooling towers to cool recirculated fresh water. ' ' ERARING WAS THE FIRST power station in Australia to be fully equipped with 660MW generating units and, like Bayswater, has a capacity of 2.64GW. This station is situated on the western shore of Lake Macquarie near Newcastle and draws cooling water from the lake. tle, and in 1982 was the first station in NSW to be equipped entirely with 660MW turbo-alternators. Following seven years of planning and construction, generation commenced in March 1982 when the first turbo-alternator set came on line. The second and third units were completed in 1983, with the fourth placed in operation the following year. Eraring is situated on the western shores of Lake Macquarie, a large body of salt water about 28km long and up to 10km wide. Open to the ocean at Swansea, the lake consists of many bays and headlands and has almost 500km of foreshores. Many of Newcastle's suburbs nestle along the shores of this pleasant fishing and boating area. Such a large body of water also provides an excellent cooling supply for the power station's condensers. From Bonnell's Bay, water at 84,000 litres/s is drawn via a 5km long canal to a pumping station. To 34 SILICON CHIP avoid upsetting the local ecology, this inlet water passes under Dora Creek through a 260 metre long concrete tunnel which is 23 metres wide and 4.8 metres high. After being lifted to a high level storage dam, this salt cooling water descends through pipes to the powerhouse, there to be pumped through the condensers associated with each turbine. The cooling water is then returned to Lake Macquarie via a tunnel and canal to Myuna Bay. The immense scale of the cooling system may be judged by the civil engineering effort involved. The inlet canal required a 2,000,000 cubic metre excavation which was then lined with 160,000 tonnes of concrete. The Dora Creek underpass tunnel itself used 16,000 tonnes of concrete. The total canal system, inlet and outlet, runs for nearly 9km. Local mines The site chosen on Lake Macquarie, as well as affording ample cooling water, is situated in the midst of plentiful coal reserves. Myuna and Cooranbong collieries (4.5km and 1.8km distant) are captive mines, specially developed to supply the station. Eraring's total coal usage is 6,500,000 tonnes per year. Coal is delivered from the mines to the power station by conveyor belt. Additional supplies come by road from the nearby Newstand (close to Fassifern) and Awaba mines. By designing larger furnaces and providing appropriate forced and induced draft, power stations can successfully use cheaper low grade coal. This policy has for decades allowed the higher grades of steaming coal to be shipped overseas to produce export income for Australia. Low grade coal with an energy rating 23 . 3MJ/kg (megawattseconds per kg) is supplied to Eraring. Bayswater power station uses coal with an average rating of 22.4MJ/kg. Some coal is treated to remove impurities before use in the power station. In general, in the Newcastle region, the low gr9-de coal comes from shallower mines around Lake Macquarie and in the Muswellbrook area of the Hunter Valley. The higher grade export coal is obtained from very deep pits on the Cessnock field. Environmental impact Despite its enormous size, Eraring station is fairly inconspicuous on the lakeside, largely because it has no cooling towers. The four boiler houses blend with the lake and surrounds and the two slender 200-metre high emission stacks are virtually unnoticeable against a cloudy sky background. Smoke emissions are tightly controlled. The highly successful fabric flue filters trap 30,000 tonnes of fly ash annually. This byproduct is not wasted but is sold for concrete and roadmaking additives. Some key dimensions Eraring's boiler structures are each 80 metres tall. Each of the four turbo-alternators is 50 metres long and weighs 1342 tonnes. They THESE HUGE TRANSFORMERS at Eraring Power Station step up the generator outputs from 23kV to 500kV for transmission to the Kemps Creek Substation. The overall thermal efficiency from coal input to electrical output is 35.4%. WALLERAWANG POWER STATION, west of Lithgow, contains two 500MW turbo-alternators plus two 60MW units (the latter used in mid-winter peak periods) .. A large cooling tower cools the water from the condensers. each stand on a reinforced concrete foundation consisting of 24,000 tonnes of concrete and 1000 tonnes of steel. All four stand in the truly gargantuan turbine hall which is 418 metres long, 27 metres wide and 38 metres high. Approximately 7,400,000 litres of fresh water per day is supplied by Newcastle city for boiler make-up water and sundry purposes. Each of Eraring's four boilers generates 590kg/s of superheated steam at 15,860kPa (2200psi) and 538°C. The alternators, running at 3000rpm, each generate 3-phase 50Hz power at 23kV, 20.71kA, giving 660 megawatts at 0.8 power factor. Eraring's thermal efficiency is quite high, at 37.7% from coal input to alternator output. When the station load is added, the overall efficiency from coal input to station electrical output is slightly less at 35.4%. Tough enough to take it, wherever you take it Fluke 80 Series multimeters come in a rugged, water and dust resistant case. They can handle up to 1000 VAC (RMS)/DC on any terminal and have an "input alert"™ warning if test leads are in the current jacks and a non-current function is selected. They are shielded against electromagnetic interference and are protected against shock and vibration. Each Fluke 80 Series multimeter comes in a rugged pro~ tective holster, with a unique "Flex-Stand"™, which bends and holds to any shape, allowing the multimeter to be stood or hung almost anywhere. To find out just how tough a Fluke 80 Series multimeter can be ... call your local Fluke distributor today. FLUKE AND PHILIPS - THE T & M AL LIANCE ij PHILIPS AUGUST 1990 35 The Story of Electrical Energy - ctd ATMOSPHERIC CONDITIONS are constantly monitored around the Hunter Valley power stations and smoke emissions are tightly controlled. Bayswater power station The success of Eraring, together with the State's increasing demand for electrical energy, lead to the building of an almost identical station at Bayswater in the Upper Hunter River Valley. This was completed in 1986. Bayswater and Eraring now form the backbone of NSW's baseload energy supply and they are presently the two largest power stations in Australia. Coal from dedicated open cut mines at Ravensworth and Swamp Creek is carried by 13km long conveyor belt systems to the power station. Load cells built into certain belt support rollers weigh the coal on-the-run. Deep underground mines at Liddell and Muswellbrook together with open-cut mines at BP Howick, Bayswater-2 and Drayton supply coal by rail and road. Liddell power station Close to Bayswaster is the older Liddell power station. Built in 1971/73, this installation consists of four machines, each rated at 500MW. 36 SILICON CHIP Cooling towers and two fresh water lakes, Lake Plashett and Lake Liddell, provide fresh water coolant for the Liddell and Bayswater stations. Water comes from the Glenbourn dam which is kept filled by 20 gigalitres/year of fresh water pumped from the Barnard River. This water flows via a pipeline and pumping system over the Mt. Royal range into the Hunter River headwaters above Glenbourn Dam, supplementing the upper Hunter's catchment. Both Liddell and Bayswater are fed by conveyor belt from the same, six open-cut coal mines. These are the only NSW power stations receiving coal from open cut operations. The complex conveyor system allows coal to be sent from the mines to the stockpiles at either station. Coal transfer between stations by conveyor is also possible should the need arise. Dirt and impurities are washed out of the coal by washeries before the coal is crushed to the powder required by the station's furnaces. Liddell consumes 2,900,000 ton- nes of coal plus 13,200 tonnes of fuel oil annually. Before Eraring and Bayswater were operational, Liddell power station was the largest in the state, the backbone of the NSW Electricity Commission's generating system. Now it is third in size. Liddell's overall thermal efficiency is 29.1 % . Other lakeside stations Other large stations in the NSW system include Vales Point-B on Lake Macquarie where two 660MW units were installed in 1978/79. Also Munmorah, built in 1967/69 between Lake Munmorah and Lake Budgewoi, features four turbo-generators rated at 300MW each. The older W angi power station is now in dry storage. Wallerawang Wallerawang, west of Lithgow and about 160km from Sydney, is located on the western coalfields. The station consists of three parts. The older A section is now in dry storage as its small 30MW machines are less efficient than the newer additions. The B station has two 60MW units. These are classed as intermediate load plant and used only in mi_d -winter peak periods. The C station, with two 500MW turbo-alternators, was commissioned in 1980. The combined 1 gigawatt output of these machines is an essential component in the state's base load capability. Each 500MW turbo-alternator unit is 48 metres long and weighs 1300 tonnes. This is only fractionally smaller than the 660MW monsters at Eraring and Bayswater. Base load and peak load The six stations we have discussed so far - Eraring, Bayswater, Liddell, Munmorah, Vales Pt and Wallerawang-C are together capable of continuously generating 10.5 gigawatts as long as required. Normal system practice is to have the most economic stations, Bayswater and Eraring, supply the bulk of the continuous load. As domestic, industrial and traction electricity demands vary throughout each day, the other large power stations in the system take up the extra load. By base load we mean the normal electricity demand over a long period, neglecting the twice-daily peaks. Every morning and evening the state uses more electricity as people take showers and prepare meals. This adds considerably to the base load. The minimum power demand typically occurs at around 4am every morning. Included with this article is a On the alert, accurate and safe Fluke 80 Series multimeters come with a large number of "alert" functions designed to ensure safe, easy use. The "Input Alert" prevents accidental damage through wrong lead connection. An automatic power cut-off (after 30 minutes idle) extends battery life. This may be overridden in 36 hour record mode . And the readouts couldn't be easier. Fluke's patented "Touch Hold" ™ feature, when activated, captures, locks and displays each measurement, yet leaves you both hands free to position the probes. In the relative mode, measurements can be made relative to your own reference point Arid there's a maximum/minimum alert, plus automatic storage of max/min readings. And there's much more . Why not be alert to all the special features of Fluke 80 Series multimeters . .. call your local Fluke distributor today. FLUKE AND PHILIPS - THE T & M ALLIANCE MYUNA COLLIERY IS ONE of two specially developed underground mines supplying Eraring Power Station (background). The colliery is 4.5km from Eraring and delivers its output to the station by conveyor. Eraring's total coal usage is 6,500,000 tonnes per year. PHILIPS A UG UST 1990 37 Eraring was supplying exactly 100% of its rated capacity, while Bayswater was at 76%. Notice too that the sharp peaks of 1.3GW around 9am and 6pm were supplied by the Snowy Mountains hydroelectric system, where generators can be started and stopped at short notice. [But that's a story for another chapter). Big British ,b oilers Before closing this chapter, we should have a look at a modern overseas power station, to see how it compares with big Australian power plants. A good example is England's Littlebrook-D power station. Situated on the south bank of the Thames River, this installation features three 660MW oil fired boilers and turbo-alternators. It was built in 1981-2 by NEI (Northern Engineering Industries) Ltd of . Newcastle and the Central Electricity Generating Board (CEGB) of England, and it contributes almost 2GW to the British national grid. Steam at 16,560kPa pressure and 541 °C is generated by boilers which are oil-fired rather than using coal. The boilers are every bit as big as Australian units, containing thousands of tubes made from carbon-chromium-molybdenum steel. These tubes, totalling 480km in length, weigh a total of 6000 tonnes, two-thirds of which hangs suspended from a steel framework extending up to 68 metres high. THE STEAM DRUM for one of the 660MW boilers at Littlebrook Power Station, Englan_d, during construction. The drum is 35 metres long, 2.5 metres in diameter and weighs 250 tonnes. chart showing the winter load used by the whole state of NSW on a particular day (26th June, 1989). Notice the big peak in the morning as people are waking, heating themselves, cooking breakfast and travelling by electric train between 6am and 9am. By that time, industrial and business loads form a steady demand until around 4pm on weekdays. BELOW: THIS CHART shows the total load for NSW on the 26th June, 1989, together with the contribution of each station. Notice the evening and morning peaks and the contribution of the Snowy Mountains hydroelectric stations. Then as evening slides into night, the traction, cooking and heating requirements reach an all-day high, until around 11pm when the general populace tires of TV and goes to bed. Observe the evening peak of 8.943GW - a staggering quantity of electrical power. It is equivalent to the power drawn by almost 9 million lkW single bar radiators. The load chart also shows the contribution of each power station to that particular day's demand. Of this , Bayswater generated 2 gigwatts, Eraring 2.65 gigawatts, Vales Point 1 gigawatt, and Wallerawang and Munmorah 800MW each. That means that 10000 8943 MW' System load B E.C Pumps E3 Snowy [j 9000 8000 7000 SboalhaJ•en 6000 Other 5000 4000 3000 2000 .1000 0200 38 SILICON CHIP 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200 2400 ■ 111, THIS VIEW SHOWS one of the boilers at Littlebrook Power Station (England) during construction. Note the size of the steel girders needed to support the steam drum and the 6000 tonnes of economiser and reheater tubes. The station now contributes 2GW to the British national grid. All the tubes are joined to the steam drum above. Construction involved 70,000 pressure-tight welds of which 10,000 were made on site. Some of the photos in this article show the boiler in various stages of construction. Pre-heating and post-heating was a necessary part of each welding operation. Rigorous quality control, testing and inspection of all welds is necessary for reliability. 100% individual ultrasonic and magnetic particle analysis was used to con. firm that · every weld met the rigorous specifications necessary for long life reliability. During heating from cold to full temperature, the vertical hanging tubes extend their lengths by 225mm due to thermal and pressure expansion. That's a lot of expansion to cope with while still maintaining those extreme steam pressures. Also part of the suspended mass in the boilers are the main steam drums, fabricated from 125mm thick DucoL-W30 carbon manganese steel. Each drum is 35 metres long and 2.5 metres in diameter, and weighs 250 tonnes. Our photo, taken during construction of the boiler, shows the massive proportions and the hanging braces carry- ing the weight of the tubes. Upon completion, the drum, steam tubes and pipes were hydraulically pressure tested, with only 8 leaks being found in the 140,000 welds of two boilers - an excellent result! Each boiler at full load consumes 140 tonnes per hour of heavy residual oil fuel which is delivered by ocean going tankers. Oil firing allows quicker start-up compared with the use of coal. In · other respects, England's Littlebrook-D power station is quite similar to large Australian stations. It too does not need cooling towers, as it is sited right on the river. Acknowledgements Grateful thanks and acknowledgement to ASEA and ABB journals, Electricity Commission of NSW, C. A. Parsons & Co Ltd, Dr Habibulah, Electronics and Power Journal, IEEE, IEE, and NEI Newcastle-Upon-Tyne, for photos, data and permission to publish. Finally, the Electricity Commission of NSW advises that inspection parties are taken on conducted tours of certain power stations. Interested readers should ring the Commission on (049) 73 2933 or (02) 268 6800. ~ Count on them to measure up 1n more ways ■ Fluke multimeters are made in the USA, to the highest standards, offering accuracy you can depend on .. . and they are guaranteed for 3 years by Philips, the name you can trust Each measurement is clearly shown on the display, so you know exactly what you're measuring .. . without having to check connections or switch positions. Fluke Models 83 and 85 have bar graphs for analogue readings, while the Model 87 has a high resolution pointer. The 10-times zoom facility lets you enhance resolution. And your Fluke Multimeter comes comp lete with protective holster, safety leads, 9V battery and operating instructions . To find out why no other multimeter measures up . to the Fluke 80 Series ... ca ll your local Fluke distributor today. FLUKE AND PHILIPS - THE T & M ALLIANCE [e) PHILIPS AUGUST 1990 39