Development of Hydropower & Renewable Energy (HRE) Project Khyber-Pakhtunkhwa (Phase-I) TECHNICAL GUIDELINES & REPORTS

Transcription

1 German Pakistan Financial Cooperation Development of Hydropower & Renewable Energy (HRE) Project Khyber-Pakhtunkhwa (Phase-I) TECHNICAL GUIDELINES & REPORTS VOLUME 3: SUMMARY OF DESIGN STANDARDS JULY 2013 DRAFT

2 Development and Usage of Hydropower and Renewable Energies in KhyberPakhtunkhwa, Pakistan Table of Content 1 Definition 3 2 General Requirements Specifications for Design, Fabrication and Installation of Civil, Mechanical, and Electrical Aspects 4 INTEGRATION Environment & Energy Ltd. Bahnhofstr Graefenberg / Germany Ulrich Frings July 2013 Summary of Design Standards page 2

3 Development and Usage of Hydropower and Renewable Energies in KhyberPakhtunkhwa, Pakistan 1 Definition Hydropower converts the energy in falling water into electric power. Micro-hydropower plants (MHP) are generally defined as isolated hydropower plants with capacities up to 500 kw that are managed by rural communities. The generating parameters of MHP are 230V / 400V, 50 HZ frequency Alternating Current (AC) systems. Such power plants provide electricity services to rural households and institutions that are not connected to the national or regional electricity grids. Lighting, agro-processing and electrically or mechanically (directly) driven equipment are the main uses of electricity generated from microhydropower plants. Typically, micro-hydropower installations include the following four major components: i) Civil works comprising intake/head works, water conveyance structures, penstock pipes, and powerhouse; Hydro-Mechanical equipment comprising penstock pipes and water control equipment like gates/valves. i Hydro Electro-mechanical equipment comprising turbine generator unit with electrical control and protection system Electrical transmission and distribution lines including transformers, protection equipment and service connections with rated (line to line) voltages up to 11 kv. All of the above four components are closely interlinked to form an integrated micro-hydropower plant. 2 General Requirements The purpose of the proposed technical standards and specifications is to improve the quality and ensure specified output, reliability and safety of the electricity services provided by micro-hydropower plants in a cost effective manner. The proposed standards are the first in an ongoing iterative process and can be improved over time as component manufacture and installation capability improves. The standards will be accompanied by a checklist to confirm adherence to them. The standards will be designed to ensure: 1. Guaranteed output: The MHP should be able to produce the installed capacity when the design discharge is available to the turbines. The suppliers/contractors should guarantee such power output. 2. Reliable operation: During the economic life of the MHP, it should be able to provide quality electricity services continuously. There should not be frequent outages or need for constant repairs. 3. Safety: Safety concerns shall be well addressed in all MHP installations. Uncontrolled water leakages, spillages and overflows can cause soil erosions and landslides resulting in loss of property and life. Furthermore, if adequate safety measures are not taken, electricity can be dangerous for people, equipment and property. Therefore, appropriate safety considerations shall be applied in the design and installation phases to the water conveyance system, associated structures, generating equipment, transmission and distribution lines, and at the consumer end. Summary of Design Standards page 3

4 Development and Usage of Hydropower and Renewable Energies in KhyberPakhtunkhwa, Pakistan 4. Cost-effectiveness: The above three requirements will be met in a cost effective manner so that MHP installations and the electricity services are affordable to the rural communities in Pakistan. 2.1 Specifications for Design, Fabrication and Installation of Civil, Mechanical, and Electrical Aspects The MHP Standards is aimed at meeting the basic technical requirements of a micro-hydro plant. Deviation from this standard is acceptable as long as there is proven evidence that the proposed alternatives can meet the above requirements in terms of output, safety, reliability and cost effectiveness. Summary of Design Standards page 4

5 A. CIVIL WORKS A.1 General Design Requirements A.1.1 Topographical Survey i) A topographical survey of the proposed MHP site shall include a general plan and longitudinal profile from the intake to the tailrace showing locations of key structures, slope stability, gullies, and other site-specific features. i The general layout plan shall include transmission/distribution lines plan from the powerhouse to the load centers Permanent markings shall be made along the waterways, especially at locations of key structures such that they can be identified during the implementation phase. Tthe topographical survey shall be detailed enough such that contours at 1 m intervals can be prepared (in topographical maps) from the intake to the forebay locations. v) For all sizes of MHP GPS data (location, elevation) at proposed transmission/distribution pole locations shall be provided. A.1.2 Hydrology and Design Discharge i) Unless river discharge data are available at the proposed intake site of the MHP, at least one spot measurement shall be made during the lean flow season to derive the minimum monthly flow. i A.1.3 In addition, a series of spot measurements shall be taken such that it will be possible to establish a Flow Duration Curve (FDC). The design discharge of the MHP should be at least 15% lower than the estimated minimum monthly flow to address environmental concerns, i.e., to ensure that some flows are always available in the river stretch between the intake and the tailrace of the MHP. Conveyance Capacity of Waterways The waterways from the intake to the forebay (i.e., intake, gravel trap, headrace pipe/canal, settling basin and forebay) shall be designed for 10% higher flows than the required design flow in order to ensure that normal design water level is maintained when the MHP is operating at full load. A.2 Diversion Intake Summary of Design Standards page 5

6 A.2.1 A.2.2 Unless the water source is from a tailrace of another upstream MHP or a spring that never floods, the diversion intake shall meet the conditions specified below Location The diversion intake shall be located such that it can divert the required design discharge at all times, reject bed load, and minimize entry of suspended sediments and excess flows during floods. Requirements i) If a weir across the river is required the weir height shall be kept as low as possible and still be able to raise the water levels adequately to allow the entry of the design flow into the intake. i Preference shall be given to an orifice intake which is submerged at design discharge so that entry of excess flow can be minimized during flood flows. Where the river topography and site conditions do not allow a submerged orifice intake, the second choice should be a side intake with the extension of the headrace For stream with gradients higher than 2.5%, a bottom intake (Tyrolean or streambed intake) may be selected if there are no significant boulder movements in the river during flood flows. Stop logs shall be provided at the intake so that total closure of the flows into the waterways system becomes possible when required, such as during emergencies to prevent damage to the downstream waterways and for repair work during the low flows. v) A coarse trashrack shall be placed at the intake opening to prevent the entry of logs, floating debris and large boulders in the system. v vi The intake and the weir (if it is a permanent structure) should be able to withstand flood flows with a return period of at least 50 years. Flood protection walls shall be provided along river banks to retain minimum 1/50 year floods in the river if overspills in such events can damage the initial waterways structures (e.g., headrace canal gravel trap and settling basin). A spillway with a capacity to discharge flows that enter through the intake during 1/50 year return period flood shall be incorporated as close to the intake as possible. A.3 Headrace Summary of Design Standards page 6

7 i) The headrace shall be able to convey the incoming flows along with the sediment/gravel to the downstream control structure such as the gravel trap or a settling basin. i An open channel headrace shall be used in stable and gently sloping terrain Any leakage from the headrace canal shall be limited to 10% of the flows conveyed Only lined headrace canals shall be used. Either stone masonry in cement mortar or concrete shall be used as lining. In case of stone masonry, the cement sand ratio in the mortar shall be at least 1:4. v) If the headrace alignment is long or is likely to be blocked such as due to rockfalls or landslides, a spillway shall be located to discharge the entire flows conveyed. The location of such spillway shall be such that the diverted flows can be safely diverted to a nearby gully or a stream without causing any damage to land or property. If additional runoffs (i.e., water entry during rains or snowmelts) are likely to enter the headrace canal, the spillways shall be sized to divert such additional flows along with the design discharge. v vi ix) Gravity flow pipe systems (low pressure) shall be used as headrace in steep terrains, along cliffs, gullies or landslide prone areas. In case of headrace pipe, no leakage shall be allowed. If plastic pipes (e.g., PVC, MDPE, HDPE) are used for the headrace these must be buried to a minimum dept of 1 m to avoid exposure to sunlight (which causes thermal degradation), risk of freezing during winter season as well as vandalism. Buried plastic pipes should be bedded with granular materials to avoid point loading. The thickness of such bedding shall be at least half the pipe diameter. x) A coarse trashrack with maximum 50 mm spacing or 1/6 of pipe diameter (whichever is lower) shall be provided at the inlets of all piped sections such as break pressure tanks. xi) x At high points along the headrace pipe alignments provisions shall be made to release trapped air such as by incorporating air valves. At low points along the headrace pipe alignment, drain valves shall be placed to periodically flush out the deposited sediments. A.4 Gravel Trap and Settling Basin If the water source is from a tailrace of another upstream MHP or a spring that never floods, gravel trap and settling basin are not required. In all other cases, the following conditions shall apply. Summary of Design Standards page 7

8 i) If the source stream carries heavy bed load and/or gravels during floods, a gravel trap shall be provided as close to the intake as possible. i The flushing gate/valve should be sufficiently large so that supercritical flow conditions occur during flushing to remove the trapped deposits. The flushing capacity should be such that it is possible to flush gravel size equal to the coarse trashrack spacing at the intake. If excess flows during flood events can reach the gravel trap, a spillway shall be incorporated to spill such excess flows. v) A settling basin shall be included in all MHPs v vi ix) The settling basin shall be designed to settle particles larger than 0.2mm carried by the flow. A flushing system shall be incorporated in the settling basin to flush out the sediments deposited. The discharge capacity of such flushing gates, valves or cylinder shall be large enough to completely lower the water level in the settling basin even with incoming design flows during flushing. If excess flows during flood events can reach the settling basin, a spillway shall be incorporated to spill such excess flows. x) Both the gravel trap and settling basin shall be constructed of either stone masonry or concrete. In case stone masonry is used to construct the gravel trap or the settling basin, the cement sand ratio in the mortar shall be minimum 1:4 and all water retaining surfaces shall be plastered to a thickness of 12 mm using 1:2 cement sand mortar A.5 Forebay i) A forebay tank shall be designed and built to connect the headrace to the penstock. i The forebay structure shall be constructed of either stone masonry or concrete. In case stone of masonry, the cement sand ratio in the mortar shall be minimum 1:4 and all water retaining surfaces shall be plastered to a thickness of 12 mm using 1:2 cement sand mortar The forebay shall include an overflow spillway with the capacity to spill the entire design flow, a drain valve or a gate to drain the water during repair and maintenance, and a fine trashrack to prevent entry of floating debris and coarse particles. The minimum volume of the forebay shall be such that at least 15 seconds of design flow can be stored above the penstock pipe level. Summary of Design Standards page 8

9 v) A minimum submergence depth of 1.5V 2 /2g shall be maintained from the normal water level to the penstock inlet at the forebay in order to avoid vortices or entry of air into the penstock pipe. Note that V is the velocity in the penstock pipe during design flow and g is the acceleration due to gravity (9.81 m/s 2 at sea level). v vi ix) In areas where water freezes in winter an additional 0.30m depth shall be added to the submergence depth calculated above. The penstock pipe invert level shall be at least 0.20m above the forebay floor so that accidental entry of debris and sediments can be avoided. Where the forebay acts as a final settling basin, sediment shall be hindered from entering the penstock by a sill that extends at least half the diameter above the penstock and a flushing system similar to the settling basin shall also be incorporated. The risk of leakage through the forebay wall facing the penstock pipe shall be minimized by incorporating a mild steel flange embedded in concrete. The minimum thickness of such concrete shall be equal to the pipe diameter or 0.30 m, whichever is higher. x) In case a plastic (e.g., PVC or HDPE) penstock pipe is used, the initial portion of the pipe shall be of mild steel and connected to such plastic penstock using standard flanges outside the forebay wall. A.6 Penstock The hydraulic performance and mechanical requirements for penstock pipes are specified in Section B.3. Civil works requirements for penstock pipes are specified below. i) An air release pipe (breather pipe) shall be located within 1.0 m from the start of the penstock pipe to avoid negative pressure in case the penstock inlet gets blocked. The diameter of the air release pipe shall be such that air velocities remain below 30m/s. i Penstock pipes made of plastic such as PVC or HDPE shall be buried to a depth of at least 1.0 m from the ground surface to the top of the pipe. Mild steel pipes that are joined by welding may be buried (if required due to site conditions) only after applying corrosion protection paint. Flange connected mild steel pipes shall not be buried in any case as the gaskets between the flanges need to be changed during the economic life of the MHP. Buried pipes (either plastic or mild steel) should be bedded with granular materials to avoid point loading. The thickness of such bedding Summary of Design Standards page 9

10 shall be at least half the pipe diameter. v) No leakages shall be allowed from the penstock pipes. v vi ix) Supports blocks and saddles made of masonry, concrete or mild steel for above-ground pipes shall be provided along the length of penstock to adequately support the weight of the pipe and water. A minimum ground clearance of 0.3 m shall be maintained along the entire exposed penstock pipe alignment. Penstock support blocks or saddles shall allow longitudinal movement of the pipe due to expansion and contraction with minimum friction such as by providing layers of bitumen or asphalt sheets or other low friction materials along the contact surface between the penstock and the supports. Hydraulic forces in bends, contractions, and forces from friction on saddles and temperature differences as well as from pipe and water shall be securely anchored and transmitted into the ground at adequate distances. Concrete anchor blocks encasing the penstock pipe maybe used for this purpose. Such anchor blocks shall be placed at all penstock pipe bends, and at 30 m plan length along the alignment even if there are no bends One expansion joint shall be incorporated between two anchor blocks to allow longitudinal pipe movement (contraction/expansion) due to variations in the ambient temperature. A.7 Powerhouse i) A powerhouse shall be designed and built to protect the generating and control equipment from adverse weather conditions and prevent access by unauthorized persons and shall be at minimum similar to a rural residential house with lockable door, adequate number of windows for ventilation, and a water proof roof. i The powerhouse plinth area shall be based on space requirements for the generating units and control panel, ease of access for operators to such equipment, additional floor space for future repair and maintenance work and to store spare parts and tools. Adequate drainage shall be provided around the powerhouse building. The elevation of the powerhouse floor shall be above at least a 100 year return period flood level v) The foundation for the MHP equipment shall be made of reinforced concrete and shall be designed to withstand at least the short-circuit torque of the generator in addition to the static loading. Forces from the penstock and turbine isolation valve shall be taken up and transferred into the ground by a powerhouse anchor block Summary of Design Standards page 10

11 v A.8 Tailrace and shall not be loaded onto the turbine casing. Cable ducts in the powerhouse shall be provided with adequate drainage. Slope of the powerhouse floor shall prevent water from entering into cable ducts. The requirements for the tailrace are similar to that of the headrace (canal or pipes may be used), except that the longitudinal slopes may be steeper. i) For Pelton and Cross-flow installations, the tailrace shall be designed in such a way that the water level at the start (sump pit) is at least two times the runner diameter below the turbine centerline during full flow. i The tailrace outlet shall terminate either in the river bank or upstream at a safe location (e.g., stable rock outcrop) such that powerhouse foundations and adjacent land and properties are not damaged. Energy dissipating measures shall be provided at the end of the tailrace if it is likely to erode the river bank or damage land and properties nearby. Provision shall be made for at least temporary installation of a V notch weir for efficiency verification of the generating unit. A.9 Electric line poles and foundations Specification of electric line poles, ground clearance, distances and other technical parameters are discussed in Section D. The installation requirements (civil works) are specified herein i) Electric line poles shall be designed to withstand wind forces on conductors and poles with prevailing wind speeds and ice loads in Pakistan. i Electric line poles shall be treated wooden poles, local hard wood poles, concrete poles, or metallic poles. In case of metallic poles, a minimum 2 mm thick galvanized pole or minimum 3 mm thick mild steel pole red oxide primed and painted shall be used. Untreated wooden poles kept 0.3m free above ground and supported by a section of metal of reinforced concrete buried in the ground are allowed. Steel poles shall be encased in concrete from the ground surface to a height of 0.3 m (concrete thickness = 0.5 x bottom diameter). All metal poles shall have top cap and bottom plate welded to it. Thickness of top cap and bottom plate shall be minimum 2 mm and 4 mm respectively. Summary of Design Standards page 11

12 Guy wires shall be used to accommodate any unbalanced forces from conductor tensioning or change in the direction of the transmission or distribution line. The guy wires shall be anchored in the ground by steel plates treated with anti-corrosion paint or concrete blocks and buried to such a depth that the guy wire forces are balanced solely by the weight of the soil above the anchor. v) The setting depth of poles in the ground shall be at least 0.6m plus 10% of the pole length. B HYDRO-MECHANICAL EQUIPMENT B.1 Trash-rack i) Bar spacing of the coarse trashrack shall be between 50mm to 100 mm based on average gravel size that the river carries and the flushing capacity of the gravel trap, i.e., maximum gravel size that can be flushed from the gravel trap;. i B.2 Gates The fine trashrack shall comprise vertical steel bars or rods with a clear bar spacing not larger than 0.5 times the nozzle diameter in case of a Pelton turbine and 0.5 times the distance between runner blades for cross flow turbines. In any case it should not exceed 20 mm to prevent entrance of fishes into the penstock pipe. The size (length and width) of the trashrack shall be such that the flow velocity through the trashrack at design flow shall not exceed 0.5m/s. The trash racks shall be placed at 1:3 (V:H) slope for ease of cleaning and a suitable cleaning rack shall be provided. i) Sluice gates shall be structurally designed to withstand full water pressure on the upstream face when there is no water downstream. i B.3 Penstock Stop log gates shall not be used as main intake gates since they may have to be closed under flowing water and emergency situations. For sluice gates larger than 0.5m wide and 0.5m deep spindles or other mechanical hoisting system shall be provided for gate operation. Simple gates without mechanical hoisting system are acceptable for gates with both sides less than 0.5 m. i) Unless justified by detailed financial calculations penstock pipe diameters shall be sized such that the total head loss at design flow is within 5% to 10% of gross head including bend, inlet and other local losses. Summary of Design Standards page 12

13 i The pressure rating of pipe or pipe thickness and other fittings shall be selected in such a way that the static head plus anticipated surge head as determined by turbine valve closing time or nozzle blockage can be safely accommodated at any point. In case of corrosive pipe materials such as mild steel, a corrosion allowance of at least 1.5 mm. C C.1 General Hydro ELECTRO-MECHANICAL EQUIPMENT i) The equipment must be packed in such a way that transport to the site is possible and safe. Finished & machined surfaces of large parts shall be applied with anti-corrosive paints and protected with rubber sheet and wooden pads or other suitable means against damages during handling and transportation. Un-assembled pins or bolts shall be oiled or greased. i All as-built drawings must be prepared and must be kept for 20 years. An operation and maintenance manual shall be prepared and submitted in English as well as in Urdu at the time of putting the plant into operation including the following- - Plant characteristics with as build data, summary specifications, key settings of protection systems and fittings - Normal and emergency operating processes - Maintenance schedules A technical manual shall be compiled and submitted within 2 weeks of putting the plant into service including the following- - As built construction drawings of civil works, hydro-mechanical, electro-mechanical and transmission / distribution lines - Copies of catalogues of all major components supplied by third parties. C.2 Turbine Isolation Valve (Main Valve) i) A straight-through type turbine isolation valve such as gate or wedge valves or butterfly valves shall be provided in all MHP installations. i Pressure rating of the main valve shall be sufficient to withstand maximum hydraulic pressure including anticipated surge pressure. When using butterfly or spherical valves, the use of a manually operated lever-type actuating mechanism without gearing is not allowed. Summary of Design Standards page 13

14 A by-pass around the main valve shall be provided to equalise the pressure at pressure heads above 40m and valve nominal bores of 250mm and above. v) A drainpipe and valve of suitable diameter shall be provided to allow for draining the penstock at closed / blocked main valve or turbine valve. At pressure heads above 40m, an orifice plate downstream of the drain valve shall be provided to reduce the water velocity and wear in the drain valve. C.3 Turbine and Accessories i) Turbines shall be equipped with flow regulating valve/s. i The efficiencies of all turbines at rated output to be used shall be as follows: Pelton >70% Cross-flow >65% Francis >85% Efficiencies will be spot checked at actual installations by measuring power output, accurate head and flow and assuming realistic estimates of efficiencies for other components. The bearings of the turbine must be selected and maintained to provide a minimum service life of 100,000 hours at the normal intended operating condition. The turbine runner and associated flow regulating devices and nozzles shall be of abrasion resistant materials. v) All turbine surfaces made of steel shall be corrosion protected by coating with zinc rich primer and two finish coats of tar epoxy or equivalent. v vi The turbine must be fully assembled at works. All flanges must be fitted using water resistant grease to avoid corrosion. It is recommended that the turbine be driven by a motor at rated speed for 24 hours in the workshop. The bearing temperature must be below 60 o during this time. The turbine runner shall be at least statically balanced at manufacturer s works before dispatch. Cross-Flow Turbines: The clearance between the runner and nozzle should be less than 0.5 mm Summary of Design Standards page 14

15 ix) Pelton Turbines: The maximum misalignment from nozzle axis to the PCD (Pitch Circle Diameter) shall not be more than 3% of the nozzle diameter. x) Turbine steel casings shall have adequate thickness. The turbine should not be noisy nor vibrate in a way that threatens progressive damage. C.4 Speed Increaser/Reducer and Couplings i) Increasing the speed between turbine and generator (where required) will be done through the use of pulleys linked by synthetic belts (flat, toothed or V-belts). i When using direct coupling between turbine and generator, the short circuit torque shall determine the capacity of the flexible coupling. Drive ratios shall be less than 3:1 for pulleys. Coupling alignment resulting in Axial and Radial displacement of more than 0.3 mm shall be rejected. v) Belt drives shall have mechanical safety cover. v The pulley diameters used must not be smaller than those recommended by the belt and generator manufacturers, in order to prevent over-tensioning of the belt and over-loading of bearings. C.5 Generator Pulleys shall be at least statically balanced at the workshop. i) The specified generator shall be able to continuously supply the desired output under the intended site conditions (altitude, ambient temperature, user load/power factor). - Derating due to main load power factor (applicable to synchronous generator only): PF lag Derating Derating due to altitude Alt, masl Derating Summary of Design Standards page 15

16 i - Derating due to ambient temperature Temp o C By class F of insulation By one class lower All synchronous generators shall be self-excited self-regulated type rated at 0.8 pf. Unity pf synchronous generators shall not be allowed. Generator efficiency (peak and as a function of cosphi 1.0 and 0.8) shall be stated by the supplier/manufacturer in the quotation and the specifications. Generators must have an efficiency of more than 90% at full load. Generator enclosure protection should conform to IP 23 or better. v) It is recommended that the generator has a class F insulation or higher. v vi ix) The over speed capability of the generator must correspond to the duration of runaway conditions of the turbine. The turbine and generator shall be mounted on a single steel fabrication, the base frame. This shall be fabricated from angle iron or channel section. The bearings of the generator shall have a minimum service life of more than 100,000 hours at the intended normal operating condition. Synchronous Generator: Any electronic voltage regulator (AVR) shall be compatible with electronic load controller system (when applied) and shall have frequency roll-off feature to protect generator under low speed. Surge suppressor shall be provided where necessary to protect electronic and semi-conductor devices used in generator from voltage surges. x) The generator must be capable to provide a permanent overload of 10% of nominal load) xi) The generator shall either be short circuit protected by appropriate protection device (shutdown or over current trip) or de-excited under SC. Maximum current setting of any short circuit protection devise shall be not more than 400% of the site rated current. C.6 Electronic Load Controller Summary of Design Standards page 16

17 i) The use of Electronic Load Controllers is recommended for all micro-hydro plants to generate well regulated power and facilitate the use of electric motors and other industrial loads. i Ballast dump load shall be in the form of resistive water and/or air heaters. Ballast size shall be at least the size of the plant. In case of Thyristor type ELC, the ballast load shall be at least 20% higher than the plant capacity. Water heaters shall be placed in a large water tank with water supplied from the penstock (minimum size 25 lit / kw) or in an enlargement of the tailrace. v) Surge arrestor must be provided (Varistor) as part of the ELC. v vi ix) It shall be possible to fine tune voltage/frequency and stability. All functions of ELC and IGC shall be tested at the works (except short-circuiting). Under all normal loading conditions the voltage/frequency regulation shall be within ELC: -5% to +5% of nominal voltage and frequency IGC: 5% to +5% of nominal voltage and 5% to +10% of the nominal frequency, with the load power factor not worse than 0.8. Transient voltage and frequency deviations due to sudden load changes shall be maximum 15% and 20% of the nominal values respectively. Prolonged transient condition due to sudden load changes is not acceptable. Provision shall be made to adequately cool/ventilate ballast heaters at all loading condition such that the temperature rise is not detrimental to the heater itself and/or the objects/surfaces that come in contact with the hot water/air. Water immersion resistors if used must be totally submerged in water by min. 10cm. Immersion heaters cable connection compartment shall have drain holes to continuously drain out any seeping-in or condensed water. x) Heater connections must not be placed outside the powerhouse and must always be accessible. C.7 Flow Controlling Governor Summary of Design Standards page 17

18 A hydraulic flow-control governor is only required in larger stations and where water saving and storage requirements prevail. In case of PURE applications and water saving is required an electronic controlled flow control governor which operates at constant water level at forebay is a more economic option. C.8 Control Panel and Switch-gear i) The control panel shall incorporate instruments to monitor at least generated voltage / frequency, load current, ballast voltage or ballastload indicators kwh generation. i The switchgear shall comprise feeder MCCB or MCB. The rated breaking capacity of the switchgear shall be higher than the maximum possible fault current. Mild steel panel box shall have corrosion protection, double coat enamel painting with adequate ventilation at the bottom and at the top confirming to IP21 or better. Cable terminations should be marked / numbered and recorded in wiring diagram to be supplied. All incoming / outgoing cables should end up at properly rated rail mounted terminal connectors or standard terminal blocks. v) All power and control cables within the powerhouse shall be laid in covered ducts or on trays along the wall / ceiling as appropriate. v All regularly operated emergency and control switches (not feeder breaker) shall be accessible from the front of the panel without having to open the door. Control panel shall not be mounted on the generator. An insulation test of the control panel shall be performed at the works. C.9 Protection Equipment in Powerhouse i) Minimum provision for protection devices shall include. - OV, UV, UF, OF, OC, SC, bearing temperature, cooling water availability and temperature. i The protection devices for the induction generator shall include OV as a minimum requirement (OC breaker in the excitation circuit). Breaking capacity of line break switch/mcb/mccb should be higher than the maximum possible fault current that the generator can supply. OL tripping limit shall be set lower than generator OL capacity. Summary of Design Standards page 18

19 v) Protection level setting for generated parameters shall be as follows. OV at 5%; UV 10%; OF 15%; UF 10%. v D All exposed metal parts (control box, penstock) shall be connected to the system grounding. Equi-potential bondage shall be provided within the powerhouse. Lightning protection electrodes shall be installed next to the powerhouse and connected to the star point of lightning protection conductor from the first pole near powerhouse. Grounding should be done at adequate depth, fill material and maintenance provisions (soaking, tightening connections, provision for periodic earth resistance measurement) to obtain minimum earth resistance (not more than 10 ohms). All joints along the earth path shall be brazed or soldered. Pressure compression cable shoes / lugs and its connecting nut / bolts should be of non-corrosive material. The overall efficiencies (water to wire) to be reached during commissioning shall be at least that quoted by supplier in his offer. Failure to meet the quoted efficiency or to produce required kw at designed head and flow may result in penalty as will be stipulated in the purchase agreement between the buyer and the supplier. TRANSMISSION AND DISTRIBUTION LINES i) For overhead lines in systems where neutral is connected to ground, the neutral wire must be placed on top. i ACSR and / or Aerial Bundled Cables are to be used for overhead lines. Underground LT lines shall use armoured cables. Un-armoured cables in protective conduit may be used for short LT lines, service lines and overhead DB connections. Holes / brackets made for insulator fittings shall allow a minimum of 300 mm conductor spacing LT line. v) All un-galvanized parts of metallic poles shall be treated with corrosion protection paint. v vi Unless metal distribution boards are grounded, these shall be installed at sufficient height (at least 3.5 m from ground). All DBs shall be lockable. Trees along ACSR overhead lines shall be trimmed to ensure that any falling tree will not touch the current carrying conductors. Over head LT lines shall observe following minimum clearance from ground Line to ground 4.5m off-road, 5m along motor-road side and 5.5m across motor-road Horizontal clearance - 1.2m minimum in all cases Summary of Design Standards page 19

20 ix) Underground LT lines shall observe following minimum depth of burial 0.5m along non-cultivated land; 0.75m along cultivated land x) Receiving end voltage shall be limited to within - 8% of nominal value at any end of distribution lines. xi) x xi x xv) x xv xvi xix) Maximum allowable transmission line-to-line voltage 400V under all normal circumstances. Back-up breaker shall be provided along distribution lines in order to discriminate faults and protect thinner cables/wires. Lightning protection shall be provided for all current carrying conductors at the start and at the end of overhead transmission and distribution lines. They shall be placed at 1 km intervals for longer transmission lines. Overhead service connection shall be PVC cable (concentric or multi-core outdoor type) and the additional voltage drop shall not exceed 2%. Lightning arresters at the first overhead line pole outside shall be connected to a common ground along with ground wires of neutral and equi-potential grounding wire from the powerhouse. Pressure compression cable shoes / lugs and its connecting nut / bolts should be non-corrosive material. In a 3-phase system, load to be balanced to within a variation of 20% between phases. The neutral shall be grounded at least every 10 th pole and at every end pole. In three phase connections neutral shall be grounded at the machine side House connections should be done using at minimum 8 mm² Al cable; combined RCBOs (30 ma) and MCBs should be installed at the consumer premises. Summary of Design Standards page 20