THE ANTAS RIVER HYDROPOWER COMPLEX - CERAN

Transcription

1 THE ANTAS RIVER HYDROPOWER COMPLEX - CERAN 14 DE JULHO HPP MONTE CLARO HPP CASTRO ALVES HPP Authors: Marco Aurélio Fernandes, Vendolino Fischer and Marcelo Wood Chiarello

2 THE ANTAS RIVER HYDROPOWER COMPLEX - CERAN 1. INTRODUCTION The Antas River Power Complex consists of the Castro Alves, Monte Claro and 14 de Julho HPP plants. It belongs to CERAN, the Antas River power company (Companhia Energética Rio das Antas), comprising the consortium of CPFL - GERAÇÃO DE ENERGIA S.A., Companhia Estadual de Geração e Transmissão de Energia Elétrica CEEE-GT RS and Desenvix S.A. The CERAN Complex consists of the Antas River water power project with the construction of three hydropower plants totalling 360 MW of installed capacity, and their step-up substations and power lines for their use and the 230 kv substation connecting to the national power grid. The power plants in the CERAN Complex will add 360 MW to the installed capacity of Rio Grande do Sul state, which means approximately ten percent of the current electricity demand in Rio Grande do Sul and helps the state achieve its goal of power self-sufficiency. During construction of the complex, CERAN is adopting groundbreaking and special solutions, constantly endeavouring to interfere as little as possible in the natural environment. An example of such innovations is the opening of tunnels to prevent the formation of large reservoirs and, thereby, substantially n o. 2 on 2 nd April and unit no. 3 on 6th June The 14 de Julho hydropower plant is under construction and it is expected to start commercial operation in December Since this article was written in mid-2008 some aspects of this plant described herein may not as closely represent the as built project Location The three hydropower plants are located on the Antas River, a drainage basin of the River Taquari-Antas in the state of Rio Grande do Sul (see Figure 1). Castro Alves HPP, the farthest upstream from the enterprise, has the dam located between the counties of Nova Padua and Nova Roma do Sul between the geographic coordinates of 29º 00' 30" South and 51º 22' 45" West. Monte Claro HPP dam, downstream from the Castro Alves HPP, is on the geographic coordinates 29º 01' of South latitude and 51º 30' West longitude between the counties of Veranópolis and Bento Gonçalves. The 14 de Julho HPP, downstream from Monte Claro HPP, lies between the counties of Bento Gonçalves and Cotiporã, with the powerhouse installed in Cotiporã Figure 1 - Location of CERAN Complex Plants County, on geographic coordinates 29o03' South and 51o40' West Suppliers Consórcio Fornecedor do Complexo Rio das Antas (COFRAN) is in charge of the enterprise, involving the companies Construções e Comércio Camargo Corrêa S.A., Alstom Brasil Ltda. and Engevix Engenharia S.A. These suppliers are responsible for the following: Construções e Comércio Camargo Correa S.A: Joint venture management, civil works construction, electromechanical installations and supply of 86

3 transmission lines and substations Alstom Brasil Ltda: Supply of turbines, generators, hydro-mechanical systems, lifting equipment, auxiliary power systems, transmission lines with upstreamdownstream connection and associated telecommunication systems Engevix Engenharia S.A.: Preliminary design, final design and supply of the mechanical auxiliary systems 2. GEOLOGICAL CHARACTERISTICS 2.1. Regional Geology The region where the plants are located is characterised by prevailing extrusive rocks of the Serra Geral Formation subdivided in basic (tholeitic basalts) and acid (riodacites) terms. These are associated with an intense diastrophic phenomenon, which enabled the emission of lava through fissural volcanism between the end of the Jurassic and Lower Cretacean. The works site is affected by structural lineaments with preferential directions to the NE and NW, which strongly condition the drainage in the region, including the course of the Antas River in many stretches, reflected in its bends and straight stretches Local Geology The foundation of the abutments of the dams in the complex lies on flows of sound and only slightly fractured basalt, reached after removing altered horizons associated with relief joints parallel to the ground surface. The foundation surface of the structures situated on the river bed, belonging to the 14 de Julho HPP, are dense basalt and basaltic breccia. Unlike the others, the 14 de Julho had a remarkable occurrence of an extensive alluvial deposit on the river bed, consisting of pebbles and gravel of basalt rock, associated with a paleochannel. A large part of the underground excavations were in good sound rock mass and mostly with few fractures, the surfaces receiving treatments stipulated by the Barton classification "Q". However, in several places of the projects the rock mass was affected by high in situ stresses characterised by occurrences of rock burst in stretches excavated in dense basalt. These rock bursts were found in the penstocks and powerhouse vault of 14 de Julho HPP and in the headrace tunnels of Monte Claro and Castro Alves HPPs, requiring special treatment for stabilising the excavated surfaces. The fracturing of the basalt rock is predominantly subvertical with spacing between the fractures varying from centimetres to various metres. Sometimes there are signs of persistent intense inclined and sub-horizontal, planar to conchoid jointing, with spacing in centimetres to decimetres, which associated with the sub-vertical fracturing conditioned the need for intense treatments to the excavation walls. 3. HYDROLOGY, HYDRAULICS AND ENERGY STUDIES 3.1. Physiographic Characterisation of Basin The Antas River drainage basin as far as the site of the dam axis of 14 de Julho HPP covers an area of around 12,664 km 2. The Antas River starts in the Serra Geral, approximately at elevation 1150 m, in São José dos Ausentes County, flowing westwards to meet the River Taquari. Until the Castro Alves dam axis, it is 260 km in length and a difference in level of 910 m. Then it flows to the Monte Claro dam axis over a distance of 270 km with a difference in level of 1000 m, and to the 14 de Julho dam axis flows for 280 km with a difference in level of around 1050 m Climate The headwaters of the Antas River drainage basin are situated in the Serra Geral, more precisely in the region of the county of São José dos Ausentes, over a distance of approximately 50 km from the coast, draining inland as far as the site of the CERAN hydropower plants. The climate studies undertaken for the Antas River basin and micro-climate in the region of the plants were based on the data of two climatological stations and twelve rain gauge stations. In the region where the CERAN hydropower plants are installed, the average temperatures vary from 8 o to 27º C during the year. The annual average total rainfall is approximately 1,630 mm, varying between a maximum of 2,240 mm in 1983 and minimum of 1,184 mm in Its spatial variation is not very accentuated, varying from 1,500 mm to 1,750 mm Streamflow characterisation The characterisation in monthly terms of the surface water potential of the Antas River for the sites of the power plants in the CERAN complex was based on data found in the Monte Claro streamflow station. The data of the streamflow stations of Passo São Bernardo and Ponte Rio das Antas were also used to provide more consistent studies of the station's data and to fill in gaps in the readings, Natural Flows The results of the studies undertaken are presented in the following tables, for each plant. 87

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5 3.5. Energy Studies Feasibility Studies The feasibility studies were based on data referring to head division proposed in the inventory studies of CEEE, the state power company of Rio Grande do Sul (Companhia Estadual de Energia Elétrica do Rio Grande do Sul) dated To determine the capacity to be installed in the plant, dimensioning studies of the structures and electromechanical plant affected by the variation in motorising the plant for installed capacities of 90, 110, 130, 150 and 170 MW were performed. These energy studies for each plant resulted in the following: Castro Alves HPP - total capacity of 130 MW, to be installed in a single step, assured energy of 64 MW. Monte Claro HPP - total capacity of 130 MW, to be installed in a single step, assured energy of 59 MW. 14 de Julho HPP - total capacity of 100 MW, to be installed in a single step, firm energy of 50 MW Revision of Type and Number of Units During the preliminary design stage the type and number of units of the CERAN power plant complex were optimised. When refining the studies the recommendation of the type and number of units to be installed at the Castro Alves HPP presented in the feasibility studies were confirmed; in other words, the three Francis turbines were kept. For Monte Claro HPP, considering the low head and limits imposed by the operating range of the Francis turbines, their substitution by two Kaplan machines, more flexible in operational terms, was more suitable, principally considering the operation coordinated with the Castro Alves HPP, in order to optimise the regulated flow in that plant. For the 14 de Julho HPP, however, the three generation units were reduced to two, so that the low hydraulicity situations are also compensated by the operation of the water stored in its reservoir and a coordinated operation with the upstream plants. Considering that the difference between the costs of equipment for adopting a Kaplan turbine is higher than the cost of the Francis turbine, but with lower costs in the civil works, and also considering the results of the 89

6 engineering and environmental studies undertaken, the plants are economically attractive. 4. DESCRIPTION OF LAYOUTS 4.1. Transmission System The Restricted Use Transmission System for integrating the Antas River Power Complex corresponds initially to access to the basic network of Monte Claro HPP, in the 230 KV configuration, by implementing the following facilities: Monte Claro HPP step-up substation /230 KV; Monte Claro interconnecting substation, 230 KV; and Transmission line, simple circuit, 230 kv, over a length of 1.0 km, connecting the Monte Claro HPP step-up substation to the Monte Claro interconnecting substation. The CERAN Complex power plants will be dispatched in three load levels - heavy, medium and light - to produce their assured energies, totalling 173 Mw. Monte Claro, Castro Alves and 14 de Julho HPPs are connected to the Monte Claro interconnecting substation individually by 230 KV transmission lines, with a 63 MCM cable simple circuit, which interconnect these plants individually to the Monte Claro interconnecting substation 4.2. General Description of Layout Castro Alves HPP The layout of the works made use of a bend in the Antas River, so that the dam, spillway and diversion structure are located in the upstream stretch of this bend (Figure 2). The hydraulic generation circuit intercepts the loop of the river on the right bank, so that the total difference in level to be used on the site is 92 m, around 40 m of which is obtained by the dam and the other 52 m by the natural difference in level of the river along the bend in that stretch. The layout consists of the following structures: Concrete gravity dam incorporating an overflow spillway; Diversion structure with four (4) sluices (4 x 10 m); Generation system consisting of an intake, headrace tunnel around 7,093 m long and a circular arch section m in diameter, surge chamber, three penstocks 4.00 m in diameter, power house with three machines totalling 130 MW of installed capacity and a tailrace channel for returning the water to the river (Figure 3, 4 and 5). Reservoir The Castro Alves hydropower plant reservoir has an area of approximately 5.1 km² and volume of hm³ at its normal maximum water level at El m. With the maximum flood level the reservoir area attains 5.95 km². River Diversion and Control and Cofferdams Diversion Sluices There are four sluices with a rectangular section of 4.00 m wide by m high and m long. Both the inflow and outflow sill are at El m. The sill of the inlet and outlet canals is at El m and m in width. The inlet channel is around 100 m and the outlet around 90 m long. Next to the inlet is the final closing structure of the sluices, with the top at El m. This structure has four openings, one corresponding to each sluice. Equipment The set of sluices for the final closure of the gates was installed in the inlet structure with the spillway at elevation m. They are closed by means of a sliding stop-log installed in the downstream slot. The upstream slot is designed to have a fixed wheel gate only if the stop-log jams. There was no plan to recover these stop-logs after plugging the sluices. Main Cofferdams Two rock-fill cofferdams with clay waterproofing were built upstream and downstream from the dam axis to divert the river. The upstream cofferdam, with its top at elevation m, protects the dam construction area against floods of 2174 m 3 /s, corresponding to the recurrence interval of 10 years in the dry season. The downstream cofferdam, with top at elevation m, protects the drained area against floods of up to 10 years, compatible with the upstream cofferdam. River Diversion Stages The river diversion occurred in two different stages, as follows: 1 st Stage - the river remains on the river bed without narrowing. The services for the hydraulic generation circuit structures on the right abutment of the river and the approach canal and sluices and closing structure on the left bank were undertaken with the river on its natural bed. 2 nd Stage - using the sluices. The 2 nd stage diversion was undertaken using four sluices (4 x 10 m). The dam/overflow spillway works on the river bed were protected against flooding with 10 years recurrence interval during the dry season, by an upstream cofferdam at elevation 215 m and one downstream at elevation m. After completing the works on the dam/spillway and in the generation circuit, the river was closed using the gates at the top of the sluice structure, at EL m by means of a travelling construction crane. 90

7 Figure 2 - Castro Alves HPP - Dam Dam and Spillway The dam with a built-in overflow spillway has a gravity section in roller-compacted concrete (RCC). The spillway stretch is 240 m in length and tops at El m. The maximum height on the river bed is around 47 m. Beyond the spillway stretch on both abutments, the dam crest is at El m, extending for m. The dam's geometry corresponds to a gravity structure using the RCC technique to El m and conventional concrete from there on. The upstream face is vertical. The downstream side of the dam stretch has a gradient of 1V:0.70H. On the downstream side, the embankment is confined by a zone of conventional concrete, with average width 91

8 Figure 3 - Castro Alves HPP - Downstream Layout Figure 4 - Castro Alves HPP - Downstream Layout - 3D View of 0.65 m raised jointly with the RCC layers. The drainage system and inspection of the RCC embankment has a longitudinal gallery. This gallery is equipped with a dewatering system for drained water by gravity and pumping. The main drainage curtain was built from this tunnel. The overflow spillway discharges into the river bed. It was conceived with a runoff capacity for a 10,000 flood with inflowing peak of 9,011 m³/s and the reservoir water level at El m. Photo 1 shows an aerial view of the dam. Photos 2 and 3 the overflow dam spilling. 92

9 Residual Discharge System In order to meet environmental requirements, the residual outflow was stipulated at 17 m³/s and on weekends and public holidays an extra flow of 83 m³/s, for a period to attend rafting now existing in this stretch of the river. Supply Circuit The hydraulic generation circuit consists of the following structures: The headrace was excavated in rock and is approximately 30 m long with a minimum width of 15 m at the canal base. The channel is designed for a maximum velocity of less than 1.50 m/s, considering the normal maximum level in the reservoir at El m. - Intake Headrace tunnel Penstocks Tailrace tunnel Tailrace excavated in rock and around 35 m in length and 30 m in width. This tailrace was dimensioned for a maximum velocity of 3.00 m/s, in the condition of maximum flow turbined by the three units. Figure 5 - Castro Alves HPP - Downstream Layout - 3D View Intake The Castro Alves HPP intake on the right bank of Antas River has a hollow gravity concrete structure. This structure connects to the headrace tunnel through a 5.50 m long transition. Photo 1 - Castro Alves HPP - Aerial View of the Dam 93

10 conditions defined the maximum and minimum water levels in the surge chamber at El. 252,00 m and m, respectively. Lined Penstocks The penstocks are built after the surge chamber, with a small horizontal stretch and vertical stretch descending to the level of the line of distributors. The concrete-coated stretch is 4 m in diameter and 180 m in length. The metalarmoured stretch has a diameter of 3.30 m and length of around 20 m. Photo 2 & 3 - Castro Alves HPP - Overflow Dam Spilling It was dimensioned for a rated flow of 176 m³/s in order to operate under a maximum depletion of 1.00 m of the reservoir's normal maximum water level, only for daily flow compensation. The hollow gravity concrete structure topping at El. 250 m will have total width of m. Closing the headrace tunnel for maintenance will be done by closing both openings with stop-logs 4.55 m wide by 8.00 m high. Headrace tunnel The water for the turbines is supplied using a tunnel connecting the intake to the surge chamber around m long. The maximum flow of this tunnel is 176 m 3 /s. The geometry of the tunnel has a lowered circular arch cross-section m in diameter. The headrace tunnel for turbine operations operates at speeds of 2.27 m/s, lined with shotcrete on the arches. Surge Chamber Due to the extent of the hydraulic supply circuit, it was considered necessary to implement a surge chamber. The surge chamber is located around 7090 m from the inlet of the headrace tunnel 149 m distant from the axis of the generator units. The 21 x 100 m dimensions of the chamber were also adopted based on checks on hydraulic stability of the oscillations. Load acceptance and rejection Powerhouse - Civil Works Access to the site is downstream through a road connected to the main access to the project. (Photo 4 and 5). The powerhouse is underground, with three blocks for the generator units, each block m in width and around m in the cross section (Figures 6 and 7). The total lengthwise section including an area for installation and multi-use spaces is 87.5 m. The galleries of electrical equipment, where the current limiting reactors, the supply circuit breaker of the auxiliary services, general service distribution boards, set of 13.8kV handlers and unit substations are located, were designed downstream from the generating unit blocks. The toilets, battery room, battery chargers, exhaustion plenum and sewage pumps and repair shops are situated in the block of the assembly area. One of the ventilation and exhaustion rooms was designed and built in the ventilation tunnel of the main nave of the engine room and the other in the ventilation tunnel of the electrical gallery. The local control rooms will be equipped to permit control of the generating units, containing the control boards and instrumentation required to fulfil the following tasks: digital control of the unit, regulation, protection of the unit and telecommunication systems. In the area outside the powerhouse are situated the air intake for the ventilation system, the drinking water reservoir, the track for the transformers, step-up transformers and the water-oil separation tank. Powerhouse - Mechanical Equipment Turbines The three hydraulic turbines are Francis vertical axis models, with rated capacity of MW adapted for direct coupling to three-phase synchronous generators of MVA. Overhead travelling crane An overhead travelling crane indoors was planned for shifting loads during assembly and maintenance operations of the turbines, generators and other equipment of the plant. 94

11 Photo 4 - Castro Alves HPP - Aerial View of Downstream Area Photo 5 - Castro Alves HPP - Aerial View of the Powerhouse 95

12 Figure 6 - Castro Alves HPP - Powerhouse - Longitudinal Section Figure 7 - Castro Alves HPP - Powerhouse - Cross-section Draft Tube Stop-log Two stop-logs for closing a generating unit were planned for maintenance activities of the turbines. Step-up Substation The Castro Alves step-up substation is divided into three sectors: the mid-voltage sector, transformation sector and the 230 kv sector. The transformation sector consists of three 13.8/130 kv single-phase step-up transformers, which will comprise a three-phase bench of 150 MVA. The transmission line between the step-up substation of the Castro Alves HPP and connecting substation of Monte Claro is in 230 kv, consisting of a three-phase circuit Monte Claro HPP General Description of Layout The layout of the Monte Claro HPP works (Figure 8) consists of the following structures: The dam is RCC roller-compacted concrete (Figure 9). Included in this dam structure is the overflow spillway. 96

13 On the right abutment is the surface spillway structure. A generation system consisting of intake, headrace tunnel with rectangular-arch section m in height, surge chamber, two penstocks 6.66 m in diameter, powerhouse housing two machines totalling 130 MW of installed capacity and a tailrace for returning the water to the river. In order to build this dam/spillway structure, the Antas River was diverted using the structures on the right bank: By the rectangular-arch section tunnel, 13 m in diameter and 324 m in length, to be installed on the right side of the spillway with gates, and therefore at the end of the right abutment. By the spillway structure with gates, but still without installing the ogee. Therefore, at the river diversion stage, this spillway had the sill lowered and the water ran off with the gates fully open. This ogee was concreted after concluding the dam/ spillway structure. Reservoir The Monte Claro HPP reservoir covers an approximate area of 1.4 km² and has a volume of around 12 hm³ at its normal maximum water level. The area of the reservoir for the water level with the inflow of the probable maximum flood is 2.5 km². River Diversion and Control The intake structures of the diversion tunnel, with slots for two stop-logs and two fixed wheel gates, a rectangular cross section 4.00 m wide by m high are set at El m in order to permit the river diversion with a little difference in level of 3.00 m between upstream/ downstream. The most frequent floods were discharged through the diversion tunnel jointly with the lowered sills of the spillway. After concluding the works of the overflow dam and the operating tests of the spillway equipment with radial gates, the stop-logs were placed at the inlet to the diversion tunnel and the tunnel plug was concreted. Main Cofferdams Two cofferdams were built for the diversion: one upstream and the other downstream from the dam axis. Both were in rockfill and waterproofed using clay material. The upstream cofferdam, with top at El m protected the construction area of the dam against floods of 3847 m 3 /s, corresponding to a 10-year recurrence interval during the dry season. The top of the cofferdam downstream was at El m. Figure 8 - Monte Claro HPP - Upstream Layout 97

14 Figure 9 - Monte Claro HPP - Overflow RCC Dam - Cross Section River diversion stages 1 st Stage - With the river continuing to flow in its natural course, the diversion tunnel and concrete structures were built on the right bank at the outlet for the positioning of the stop-logs and spillways structure with gates and a lowered sill during the river diversion stage. The structure of the inlet of the diversion tunnel on the right bank, with two openings with a rectangular cross section of 4.00 m wide by m high, and a sill at El m as designed to permit the discharge of the normal river flows. The spillway with lowered sill has two radial gates 12 m wide by m total height. This structure was built with a lowered sill at elevation m to permit its use during the second stage of the diversion. 2 nd Stage - At this stage, the water flowed through the diversion tunnel and lowered sill spillway, built during the first stage diversion on the right bank. After concluding the dam/overflow spillway works on the riverbed and abutments, the final concreting of the spillway sill on the right bank was finally done to El m. This activity was undertaken by installing a stop-log in each bay of this spillway. After finalising the concreting of the last bay, the corresponding stop-log was removed and all bays closed by lowering the radial gates. Dam and Spillway The dam in the stretch with the incorporated overflow spillway has a gravity section in roller-compacted concrete (RCC), over a total length of around 180 m and crest at El m. Outside this stretch, the dam on both abutments is 70 m total length with the top at El m. Its maximum height on the river bed is around 27 m. A spillway with two radial gates m wide and m total height, associated to the overflow spillway, was built on the right bank, with the crest at El m. The top of this spillway structure is at elevation m. A bridge was built upstream from the radial gates at El. 158 m, for access to the control room and stop-logs, and downstream from the radial gates another access bridge for placing stop-logs downstream for the construction of the ogee arches and protection for future repairs. The set with the overflow spillway and spillway with gates was designed for capacity to discharge the 10,000 flood. The peak outflow of this flood is 17,038 m³/s. Since the reservoir has reduced dimensions, 98

15 there is no reservoir flood routing and the exceptional maximum water level of the reservoir reaches El m. The geometry of the dam corresponds to a gravity structure, adopting the RCC technique to El m and in conventional concrete from there up. The upstream face is vertical. The downstream face of the non-overflow stretch has a slope of 1V:0.75H below El m, and vertical above this elevation. Residual Outflow System In order to meet the requirements during the plant's operation, an echological outflow system was installed Photo 6 - Monte Claro HPP - Dam (in the dam) with a capacity to discharge 5.50 m³/s. An increase of this flow can be achieved by partially opening the spillway's radial gate. Supply Circuit The hydraulic generation circuit consists of the following structures: The hollow gravity intake m wide, 30.0 m high and crest at El m, is fitted in the right abutment; Headrace tunnel around 1,170 m long and with a rectangular-arch cross-section of m in height and width; Surge chamber with area equal to 1250 m²; Two penstocks with internal diameter of 6.66 m and lengths of around m, with armouring in m each; Semi-indoor powerhouse, with maximum height of m and provided with two Kaplan units. The downstream and upstream layout is shown in Figure 10 and the powerhouse section in Figure 11. Headrace Canal The headrace canal is excavated in rock and is approximately 40 m long with a minimum width of m at the canal base. The canal is designed for a maximum velocity below 1.50 m/s, considering the normal maximum level at El m. Headrace Tunnel The water for the turbines will be supplied through a headrace tunnel connecting the intake to the surge chamber, approximately 1140 m in length. For the turbine operations the headrace tunnel will run at velocities of 2.70 m/s, and will be lined with shotcrete in the arch, floor in rolled concrete and the rest of the perimeter unlined rock. Tailrace Tunnel To return the turbined flows to the river, tailrace tunnels are built in excavated rock with shotcrete lining. Intake Civil Works The Monte Claro HPP intake consists of a rectangularsection structure directly connecting and separately to the headrace tunnel through a transition m in length. The hollow gravity concrete structure, with crest at El m, has a total width of m and height of around 30 m, from its foundation. It is planned to install in the intake two stop-logs to be used for maintenance of the emergency valves provided next to the powerhouse. Photo 7 & 8 - Monte Claro HPP - Overflow Dam Spilling Equipment Trashracks The intake water passages are provided with 99

16 Figure 10 - Monte Claro HPP - Downstream Layout Figure 11 - Monte Claro HPP - Surge Chamber & Powerhouse 100

17 trashracks panels installed next to the inlet, to retain large solid materials to prevent damage to the turbines. Stop-log Stop-logs are planned to close each span of the intake and that together with its fixed parts can withstand the hydrostatic pressures corresponding to the normal maximum water level (at El m) and the most frequent floods ( m), in normal and exceptional conditions, respectively. Low Pressure Power Tunnel The low pressure power tunnel in rectangular-arch section has a width and height of m. The m long transition in reinforced concrete is in its initial stretch of the pressure section of the tunnel. The power tunnel was treated using shotcrete on the arch and walls. The rock trap was installed to retain the stones that may loosen from the roof and walls of the tunnel. Surge Chamber Due to the extent of the hydraulic circuit, it was considered to build a surge chamber, located around 1,170 m from the headrace tunnel entrance, for the purpose of hydraulic stability of the generation circuit. Inside the chamber are two concrete structures in which will be installed the stop-logs and fixed wheel gate. The stop-log is shifted by using a lifting beam operated with the surge chamber gantry crane. The concrete structures are approximately 40 m in height and 10 m in width each. Powerhouse Monte Claro has an outdoor shaft powerhouse built in reinforced concrete and equipped with two Kaplan turbines, totalling an installed capacity of 130 MW. Access to the site of the installation area /powerhouse is through an access tunnel from El m in the transformer yard. The powerhouse, with two blocks for the generating units, is m wide and around m in the cross section. The total longitudinal section including the assembly and unload areas is m. Loads inside the powerhouse will be shifted by overhead travelling crane, with capacity for 200 kn, which will move over a rail track. Situated in the area outside the powerhouse are the air intake room, the drinking water reservoir, the transformer and step-up transformer transfer track, the water-oil separation tank and the insulating oil tanks. Access to the tunnels will be made by stairs or lift, which attends the floors and will descend from El m to El m. The electromechanical tunnels are downstream from the generating units and their levels are: m, m and m. Photo 9 shows an aerial view of the powerhouse and substation. Photo 9 - Monte Claro HPP - Powerhouse & Substation Powerhouse - Mechanical plant Turbines The two hydraulic turbines are Kaplan, with rated capacity of MW, under a rated head of m with flow of m³/s and performance of 94.10%. Rated velocity of rpm is suitable for direct coupling to three-phase synchronous generators of MVA. Overhead travelling crane An overhead travelling crane for working indoors was planned for shifting loads during installation and maintenance operations of the turbines, generators and other equipment of the plant. Draft Tube Stop-log Two stop-logs for closing a generating unit were planned for maintenance activities of the turbines. The stop-logs, interchangeable with each other, together with their fixed parts, will be able to withstand the hydrostatic pressures corresponding to the normal maximum water levels, El m, and maximum maximorum of the tailrace at El m, in normal and exceptional loading conditions, respectively. Powerhouse - Main electrical plant Generators The two generators are three-phase, synchronous, with vertical axis, for indoor installation, and each is installed in a chamber consisting of a concrete shaft, closed by steel covers at the top. Each generator is connected to the mid-voltage sector of 138 KV of the step-up substation by an insulatedphase busbar. Step-up Substation The step-up substation of Monte Claro HPP is divided into three sectors: one mid-voltage, one transformation sector and the 230 kv sector. The transmission line between the step-up substation and interconnecting substation is in 230 kv, simple circuit, one cable per phase. 101

18 Monte Claro Interconnecting Substation The interconnecting substation 230 kv has a layout and management scheme in double buses with fourswitch circuit breaker; the use of three modules for the transmission lines are restricted for the Castro Alves HPP, Monte Claro HPP and 14 de Julho HPP, one module of an interconnecting bus circuit breaker and four modules for the transmission lines to be sectioned next to the Monte Claro substation, Eletrosul Farroupilha-Nova Prata 2 and Eletrosul Farroupilha-Passo Fundo. The 230 kv transmission lines Eletrosul Farroupilha- Nova Prata 2 and Eletrosul Farroupilha-Passo Fundo will be sectioned and headed in four modules of the interconnecting substation de Julho HPP Description of Layout The layout of the 14 de Julho HPP has the following structures (Figures 12 and 13): Diversion by means of the lowered structure of the spillway with gates, and a flood outflow capacity of 4,055 m³/s; Gravity concrete dam with overflow spillway Surface spillway equipped with two fixed wheel gates; Generation system consisting of intake, two headrace tunnels with a rectangular-arch section and underground powerhouse housing two Kaplan machines with steel spiral casing, with a total installed capacity of 100 MW. Photo 10 shows an aerial view of the river bend and the hydro-power plant. Figure de Julho HPP - Upstream Layout 102

19 Figure de Julho HPP - Downstream Layout Photo de Julho HPP - Aerial View 103

20 Reservoir The 14 de Julho HPP reservoir covers an area of approximately 5.0 km² and has a volume of 55 hm³ at its normal maximum water level at El m. River Diversion and Control and Cofferdams Diversion Structure The river was diverted by using the lowered sills of the spillways with gates, on the left bank. Main Cofferdams For the river diversion, two clay-waterproofed rock-fill cofferdams were built. The upstream cofferdam was topped at El m and protected the dam construction area against incoming floods of 4,055 m 3 /s, corresponding to a 10-year recurrence interval during the dry season. River Diversion Stages The river was diverted in two different stages, as follows: 1 st Stage - With the river continuing to flow in its natural course, and with the protection of a 1 st stage cofferdam with crest at El m, the concrete structure was built on the left bank to place the stop-logs and spillway structure with gates and a lowered sill during the river diversion stage. 2 nd Stage - through the lowered sill of the spillway. The 2 nd stage diversion was undertaken using the lowered sill of the spillway at El m, consisting of the two bays of the radial gates m wide by m total height. The dam works on the river bed are protected against floods of approximately 10-year recurrence intervals (flow of 4,055 m³/s) during the dry season, by cofferdams with crest at El m (WL at El m). After building the dam works (sill on river bed and abutments) the radial gates were lowered and the sill concreted. Equipment The radial gate next to the lowered sill was first lowered to concrete the sill. After this operation, the water flow was interrupted and the stop-log panels were next inserted in the slots upstream and downstream. Then the gate was raised in order to concrete the sill to its final position. The maximum flow foreseen for the closing operation was in the range of m³/s. Dam and Overflow Spillway The dam with an incorporated overflow spillway has a gravity section in roller-compacted concrete (RCC), the overflow sill with a total length of around 240 m and crest at El The stretch in the actual dam tops at El m, while on the left bank it is m and m in length on the right bank. The maximum height, in the overflow stretch on the river bed is approximately 33 m. The dam geometry corresponds to a gravity structure, using the RCC technique to El m and in conventional concrete from there up. The upstream face is vertical. The downstream face of the non-overflow stretch has a slope of 1V:0.70H below El m, and vertical above this elevation. On the downstream face, the structure will be confined by a conventional concrete zone, with average width of 0.65 m raised together with the RCC layers. The drainage system and inspection of the RCC body has a longitudinal gallery. This gallery is equipped with a dewatering system for drained water by gravity and pumping. The main drainage curtain will be carried out from this gallery. The overflow spillway structure is incorporated in the body of the dam, occupying its entire extension on the river bed and a large part of both banks. It has a curving axis, taking into account the conditions of the discharging flow downstream. This structure presents a gravity section in roller-compacted concrete (RCC), and the overflow spillway extends for around 240 m with the crest at El m. The height of this structure on the river bed is 33 m. On both banks, the crest of the dam that is not part of the spillway is at El m The overflow spillway was designed discharging the flow directly downstream, without a stilling basin as such. Spillway with radial gate Associated to the overflow spillway, a spillway with two bays, controlled by radial gates m wide and m high with the sill at El m, is located on the left bank. The radial gates will be used to control the water level in the reservoir. The gates will be dimensioned to function by opening or stopping the flow corresponding to the maximum flow and will close under its own weight. In the chamber of the hydraulic unit, there is an emergency pumping set started by an internal combustion motor. The stop-logs for maintenance of these radial gates have a free span of m, sill at El m and height of m. The spillway was checked for the 10,000 flood condition with outflow peak equal to 17,958 m 3 /s, which resulted in a maximum level in the reservoir at El m Supply Circuit The hydraulic generation circuit consists of the following structures: Hollow gravity intake m long and m high; Two headrace tunnels around 220 m in length and a rectangular-arch cross-section 8 m wide and 10 m high; the armoured stretch has an internal diameter of m; Underground powerhouse, with two Kaplan generators, with maximum height of 40.0 m. 104

21 Headrace Canal The headrace canal was excavated in rock and has an approximate length of 40 m and width of m on the canal base. The canal is designed for a maximum velocity of less than 1.50 m/s, considering the canal bottom at El m. Penstocks The turbines are supplied through two penstocks connecting the intake to the powerhouse, approximately 220 m in length. The tunnel geometry has a rectangular-arch crosssection 8.80 m in diameter and 9.75 m in height. Therefore, the arch is 4.40 m high and below the arch the height is 5.35 m. Immediately below the arch, the width of the tunnel continues at 8,80 m with 2.10 m in height. In the remaining 3.25 m, the width of the tunnel is now 7.80 m. The penstocks, to meet the operating conditions of the turbine, have velocities of 2.50 m/s, and the arch is protected with shotcrete, with the floor covered with concrete and the rest of the perimeter unlined rock. Tailrace tunnel The return of the turbined flows to the river is through tailrace tunnels excavated in the rock with lining in shotcrete with steel mesh reinforcement. Intake Civil works The intake in the 14 de Julho HPP consists of a hollow gravity structure fitted with a rectangular-section opening connecting directly and separately to the power tunnels through a transition (Figure 14). It was dimensioned for a rated flow of m³/s and to operate under a maximum depletion of the reservoir's normal maximum water level of 1.00 m, only for daily flow compensation. A hydraulically operated fixed wheel gate is installed in the intake for each headrace tunnel to guarantee security for the powerhouse's generation equipment. Photos 11 and 12 show the dam, intake and powerhouse during construction. Figure de Julho HPP - Water Intake 105

22 Equipment Trashracks The six trashracks panels for each water passage are removable, interchangeable between each other, sliding in the guides installed upstream from the intake. Stop-log To close the intake, during maintenance of the emergency gate, two stop-logs were planned that are able, together with their fixed parts, to withstand the hydrostatic pressures corresponding to the normal maximum water level (at El m) and flood level of the reservoir (at El m), in normal and exceptional loading conditions, respectively. Fixed wheel gate There are two fixed wheel gates for each unit to close under normal conditions. The hydraulic oil centres for activating the gates consist of two motor-pump groups, one being a reserve. Gantry Crane The gantry crane on the intake crest is used to install and remove the gates and the stop-logs. Photo de Julho HPP - Dam & Powerhouse Powerhouse - Civil Works Access to the powerhouse is by a tunnel connected to the main access to the jobsite. It is underground, with two blocks allocated to the generator units, m wide, around m in the Photo de Julho HPP - Powerhouse 106

23 cross-section. The total longitudinal section including assembly, unload and multi-use areas is m. The loads inside the powerhouse are lifted by overhead travelling crane, with capacity for 2,000 kn moving over a rail track. The galleries for electrical equipment are situated downstream from the generating unit blocks, where the current restricting reactors, the cubicle for the supply circuit breaker of the auxiliary services, the general service distribution boards, the handling set of 13.8 kv and unit substations will be located. In the area outside the powerhouse are situated the air intake, drinking water reservoir, the transfer track for the transformers, step-up transformers, the water and oil separator tank and the insulating oil tanks. Figures 15, 16 and 17 show the plan and sections of the powerhouse. Powerhouse - Plant Turbines The two hydraulic turbines are Kaplan with a vertical axis, spiral steel casing, with rated capacity of MW, under a rated head of m with flow of m³/s and 94% performance. Rated velocity of rpm is suitable for direct coupling to three-phase synchronous generators of 56.1 MVA. Overhead Travelling Crane An overhead travelling crane for work indoors was planned for shifting loads during installation and maintenance operations of the turbines, generators and other equipment of the plant. Draft Tube Stop-Log Two stop-logs for closing a generating unit were planned for maintenance activities of the turbines. A monorail was installed for lifting the draft tube stop-log panels. Step-up Substation The step-up substation of 14 de Julho is divided into three sectors: mid-voltage sector, transformation sector and the 230 kv sector. The transmission line between the step-up substation of 14 de Julho HPP and the Monte Claro interconnecting substation will be in 230 kv, consisting of a three-phase circuit. Its total extension is 16, m, reaching the Bento Gonçalves County and Veranópolis, Rio Grande do Sul State. 5. CONSTRUCTION ORGANISATION OF THE JOBSITE AND INFRASTRUCTURE WORKS To implement the jobsite, excavations were made in soil, embankments, slope protection, utilities networks and infrastructure services (power network, sewage collection system, waste collection, laundry, etc.), with personnel responsible for operations and maintenance. The camp facilities of the complex permitted Figure de Julho HPP - Powerhouse Plan 107

24 Figure de Julho HPP - Powerhouse Longitudinal Section Figure de Julho HPP - Powerhouse Cross Section 108

25 accommodation for 3,390 employees, five dining rooms with capacity to provide 10,500 meals a day, six medical dispensaries, sufficient for support of the personnel on the job. For the three works, recreational areas were built for the live-in employees, with games room, satellite TV room and so on. Offices were built on the works of the complex, for the production, quality, occupational and environmental safety, engineering and planning, electromechanical installation, administrative and commercial personnel on site, plus field offices for support to the service fronts. Industrial facilities for a storeroom, mechanical repair shop, equipment and carpentry yards, fuelling, wash and lubrication station, transport and property security, to serve the civil and electromechanical installation works for Monte Claro, Castro Alves and 14 de Julho. An integrated environmental education centre was built in 14 de Julho HPP, with a nursery for seedlings native to the region. Crushing and Concrete Plant Facilities The crushing and concrete plant facilities are divided as follows: Monte Claro HPP: two crushing plants and two concrete plants; Castro Alves HPP: two crushing plants and two concrete plants; 14 de Julho HPP: one crushing plant and two concrete plants, one of which is specifically for roller-compacted concrete (RCC) production, for use in the dam of this power plant. Treatment plants were implemented for treating sewage from the jobsite installations and works camp. 6. QUALITY CONTROL Quality Control focusing on the Project The contractor companies Construções e Comércio Camargo Corrêa S.A., Alstom Brasil Ltda and Engevix Engenharia S.A. agreed on a quality system as well as management activities for its adoption in the sphere of the works, services and supplies of the project, along the lines of ISO 900 standards. This quality plan adopted in the complex was certified by the company BVQI (certifying agency) in the ISO 9001/2000, in the scope of civil works construction and electromechanical installation of hydropower plants. 7. PROBLEMS FACED DURING CONSTRUCTION / GROUNDBREAKING AND SPECIAL SOLUTIONS ADOPTED IN CONSTRUCTION Some problems were found during the construction of the plants. One of them worth mentioning is the occurrence of high in situ stresses and rock burst in the underground excavations of the headrace tunnels of Monte Claro and Castro Alves HPPs and principally in the penstocks and main nave of the powerhouse in 14 de Julho HPP. An other problem found as the constructions went ahead were the constant overtopping of the cofferdams in the works of Castro Alves and 14 de Julho, due to the occurrence of exceptionally greater inflows than those of the corresponding month of the historic period Shaft excavations The Raise Boring method was used to excavate the shafts, which is applied to vertical and sloping excavations in rock, usually tunnels and galleries. This equipment was used for the rock excavation of the power tunnels in a vertical stretch of the Castro Alves HPP. 8. ECONOMIC, ENVIRONMENTAL AND SOCIAL ASPECTS The characteristics of the 27 environmental programmes that form the Basic Environmental Design (Projeto Básico Ambiental - PBA) originate from the EIA-RIMA (Environmental Impact Assessment- Environmental Impact Report) and address the biotic, physical and socio-environmental aspects. One of the main programmes worth mentioning is the Climate Condition Monitoring, the principal results of which was to prove that the formation of the reservoirs does not cause impact on regional vineyards and wine making. The monitoring, still underway, also studies the ability to forecast the water in the river, in order to achieve efficient operations of the power plants. Concerning the studies of the water quality, it was found that, after forming the reservoirs, their physicochemical conditions were maintained, as in the pre-project status. The monitoring of the quality of the water will continue during the plant operations. The seismic activity monitoring studies indicated that there is no significant influence of the construction of the power plants and of the new reservoirs on the seismicity of the region. CERAN proceeds with studies and surveys relating to the aquatic fauna in the Antas River, since the start of the bidding process of the power plants, so that full and comprehensive knowledge can be gained about the regional ichthyofauna and to establish mitigation and management activities. The main conclusion of these studies is that the fish ladder would not be the best ichthyofauna management mechanism in the case of the CERAN Complex power plants. So far, no relevant damages have been confirmed to the ichthyofauna caused by implementing the power plants, since there already were natural barriers that restrict the movement of the ichthyofauna. With regard to land fauna in the region around the complex, the physical integrity of the animals when deforesting and filling the reservoirs was kept. Field records include 25 species of amphibians, 13 reptile, 202 birds and 45 mammals. Some of these species listed 109

26 as endangered species in Rio Grande do Sul ( are as follows: 9 mammals (7 families) and 3 birds (3 families), with the following endangered level: 6 mammals - vulnerable; 1 mammal - endangered; 2 mammals - critically endangered; and 3 birds - endangered. One strong point of the project was the low socioenvironmental impact compared to the size of the complex. In Castro Alves, no family was relocated; in Monte Claro HPP it was necessary to relocate only six families and 32 families in 14 de Julho HPP. In addition to actual relocation, CERAN followed up these families to help in adapting to the new location. Based on a study with the county secretariats of education, CERAN undertook an extensive program on environmental education, which includes capacity building of the teachers and instructions to the pupils. This program covered 88 schools and 175 teachers. 9. PERFORMANCE OF PROJECT The dams of the CERAN Complex plants were built in roller compacted concrete (RCC) and are monitored for supervision of their displacements, concrete temperature, uplifts in the foundation and seepage flows in the structure. The following instruments are used for this purpose: multiple strain gauges, triorthogonal jointmeters, foundation piezometers, thermometers for concrete and flow gauges. The powerhouses of the plants were instrumented using a triorthogonal jointmeter, rod extensometer; standpipe piezometer and flow gauge. The results obtained to date show that the measurements are within the technical design parameters. 10. TECHNICAL CHARACTERISTICS CASTRO ALVES HPP Location Nova Roma do Sul, Antonio Prado, Nova Padua and Flores da Cunha - Rio Grande do Sul. Owner CERAN - Cia, Energética Rio das Antas Design Engevix Engenharia S.A. Civil works construction, electromechanical installations and supply of transmission lines and substations - Construções e Comércio Camargo Correa S.A: Supply of turbines, generators, hydro-mechanical systems, lifting equipment, electric auxiliary systems and associated telecommunication systems Alstom Brasil Ltda: Commercial Generation of First Operating Unit 28/02/2008 Reservoir Upstream W.L. Normal Min m Normal Max m Flood Max m Downstream W.L. Minimum m Maximum m Flooded areas Flood W.L km 2 Normal Max. W.L km 2 Normal Min. W.L km 2 River Diversion By sluices Number of spans 4 Sluice dimensions 4.00 x m Diversion flow (10-year RI - dry) 2,174 m 3 /s Dam Gravity RCC Total length of crest Maximum height Crest elevation m m m Spillway Overflow Capacity 9,011 m 3 /s Sill elevation m Total length m Energy dissipation on river bed Intake Hollow gravity Total length m Number of bays 2 Fixed wheel gates Width 4.50 m Height m Supply system Headrace canal Length Width m m Lined Penstock Diameter 4.00 m Number of units 3 Average length m Powerhouse Underground Number of generating units 3 Width of generating unit blocks m Cross-section of generating unit blocks m Turbines Francis Rated unit capacity MW Rated rotation rpm Reference net head m Rated unit flow m 3 /s Maximum performance 93.5% 110

27 Generators Rated unit capacity MVA Rated voltage 13.8 kv Maximum performance 98.5% Rated power factor 0.9 MONTE CLARO HPP Location Nova Roma do Sul, Veranópolis and Bento Gonçalves. Design Engevix Engenharia S.A. Owner CERAN - Cia, Energética Rio das Antas Civil works construction, electromechanical installations and supply of transmission lines and substations - Construções e Comércio Camargo Correa S.A: Supply of turbines, generators, hydro-mechanical systems, lifting equipment, electric auxiliary systems and associated telecommunication systems - Alstom Brasil Ltda: Commercial Generation of First Operating Unit 29/12/2004. Reservoir Upstream W.L. Normal Min m Normal Max m Flood Max m Downstream W.L. Minimum m Maximum m Flooded areas Flood W.L km 2 Normal Max. W.L km 2 Normal Min. W.L km 2 River Diversion Diversion tunnel associated to spillway with radial gates and lowered sill Tunnel 2 Rectangular-arch section 13 x 13 m Length 300 m N o. spillway spans w/radial gates & lowered sill 2 Diversion flow (10-year RI - dry) 3,847 m 3 /s Dam Gravity RCC Total length of crest Maximum height Crest Elevation m m m Spillway Overflow associated with 2-bay spillway w/radial gate Capacity 17,038 m 3 /s Sill elevation m Total length m Energy dissipation on river bed Supply system Headrace canal Length Width m m Headrace tunnel Rectangular arch x m Number of units 1 Average length 1, m Intake Hollow gravity Total length m Number of bays 2 Stop-logs Width 4.00 m Height m Powerhouse Shaft Number of generating units 2 Width of generator blocks m Cross-section of generator blocks m Turbines Kaplan Rated unit capacity MW Rated rotation rpm Net reference head m Rated unit flow m 3 /s Maximum performance 93.5 % Generators Rated unit capacity MVA Rated voltage 13.8kV Maximum performance 98.5 % Rated power factor DE JULHO HPP Location Cotiporã, Veranópolis and Bento Gonçalves. Owner CERAN - Cia, Energética Rio das Antas Design Engevix Engenharia S.A. Construction of Civil Works, Electromechanical Installations and Supply of Transmission Lines and Substations - Construções e Comércio Camargo Correa S.A: Supply of turbines, generators, hydro-mechanical systems, lifting equipment, electrical auxiliary systems and associated telecommunication systems - Alstom Brasil Ltda: Commercial generation of first plant in operation 21/12/

28 Reservoir Upstream W.L. Normal Min m Normal Max m Flood Max m Downstream W.L. Minimum m Maximum m Flooded areas Flood W.L km 2 Normal Max. W.L km 2 Normal Min. W.L km 2 River Diversion Using the lowered sill of the spillway with radial gates Number of bays of spillway w/radial gates 2 Diversion flow (10-year RI - dry) 4,055 m 3 /s Dam Gravity RCC Total length of crest Maximum height Crest elevation m m m Spillway Overflow associated with spillway w/2 bays w/radial gate Capacity 17,958 m 3 /s Sill elevation m Total length of overflow stretch m Dimensions of radial gates 2 x x m Supply system Headrace Canal Length Width m m Penstock Rectangular arch 8.80 x 9.75 m Number of units 2 Average length m Intake Hollow gravity Total length m Number of spans 2 Fixed wheel gates Width 4.50 m Height m Powerhouse Underground Number of generating units 2 Width of generating unit blocks m Cross-section of generating units m Kaplan turbines Rated Unit Power MW Rated rotation m Net reference head m Rated unit flow m 3 /s Maximum performance 94% Generators Rated Unit Capacity MVA Rated voltage 13.8 kv Maximum performance 98.5% Rated power factor

29 CASTRO ALVES HPP Construction of the Dam Overflow Dam during Construction - View from Upstream Powerhouse - Electromechanical Gallery Headrace Tunnel during Construction Rock Trap and Surge Chamber Overflow Dam during Construction - View from Downstream Powerhouse during Construction 113

30 MONTE CLARO HPP Overflow Dam and Spillway at the End of Construction - View from Upstream Spillway -View from Upstream Intake Structure 114

31 MONTE CLARO HPP Powerhouse in the Construction Stage Powerhouse and Switchyard 115

32 14 DE JULHO HPP Excavation of the Powerhouse - Treatment of the Rock Wall Diversion through the Spillway Spillway and Radial Gates during the Diversion Stage - View from Downstream Power Tunnel in the Construction Stage 116