V-3- MHP standards draft 03-07-13.pdf

8/20/2019 V-3- MHP standards draft 03-07-13.pdf

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German – Pakistan Financial Cooperation

Development of Hydropower & Renewable Energy(HRE) Project Khyber-Pakhtunkhwa

(Phase-I)

TECHNICAL GUIDELINES & REPORTS

VOLUME 3: SUMMARY OF DESIGN STANDARDS


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Development and Usage of Hydropower and Renewable Energies inKhyberPakhtunkhwa, Pakistan

Technical Guidelines&ReportsVolume 3: Summary of Design Standards

Table of Content

1 Definition 3

2 General Requirements 3

2.1 Specifications for Design, Fabrication and Installation of Civil, Mechanical, and Electrical Aspects ______________________________________________________________ 4


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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 managedby 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 arenot connected to the national or regional electricity grids. Lighting, agro-processing and electrically ormechanically (directly) driven equipment are the main uses of electricity generated from micro-hydropower plants. Typically, micro-hydropower installations include the following four majorcomponents:

i) Civil works comprising intake/head works, water conveyance structures, penstock pipes, andpowerhouse;

ii) Hydro-Mechanical equipment comprising penstock pipes and water control equipment likegates/valves.

iii) Hydro Electro-mechanical equipment comprising turbine generator unit with electrical controland protection system

iv) Electrical transmission and distribution lines including transformers, protection equipment andservice 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-hydropowerplant.

2 General Requirements

The purpose of the proposed technical standards and specifications is to improve the quality andensure specified output, reliability and safety of the electricity services provided by micro-hydropowerplants in a cost effective manner. The proposed standards are the first in an ongoing iterative processand can be improved over time as component manufacture and installation capability improves. Thestandards will be accompanied by a checklist to confirm adherence to them. The standards will bedesigned to ensure:

1. Guaranteed output: The MHP should be able to produce the installed capacity when the


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4. Cost-effectiveness : The above three requirements will be met in a cost effective mannerso that MHP installations and the electricity services are affordable to the ruralcommunities in Pakistan.

2.1 Specific ations 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 proposedalternatives can meet the above requirements in terms of output, safety, reliability and costeffectiveness.


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Development and Usage of Hydropower and Renewable Energies in KhyberPakhtunkhwa, Pakistan


Summary of Design Standards page 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 tailraceshowing locations of key structures, slope stability, gullies, and other site-specific features.

ii) The general layout plan shall include transmission/distribution lines plan from the powerhouse to the load centers

iii) Permanent markings shall be made along the waterways, especially at locations of key structures such that they can be identified duringthe implementation phase.

iv) 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 duringthe lean flow season to derive the minimum monthly flow.

ii) In addition, a series of spot measurements shall be taken such that it will be possible to establish a Flow Duration Curve (FDC).

iii) The design discharge of the MHP should be at least 15% lower than the estimated minimum monthly flow to address environmentalconcerns, i.e., to ensure that some flows are always available in the river stretch between the intake and the tailrace of the MHP.

A.1.3 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 bedesigned for 10% higher flows than the required design flow in order to ensure that normal design water level is maintained when theMHP is operating at full load.

A.2 Diversion Intake


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Unless the water source is from a tailrace of another upstream MHP or a spring that never floods, the diversion intake shall meet theconditions specified below

A.2.1 Location

The diversion intake shall be located such that it can divert the required design discharge at all times, reject bed load, and minimizeentry of suspended sediments and excess flows during floods.

A.2.2 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 adequatelyto allow the entry of the design flow into the intake.

ii) Preference shall be given to an orifice intake which is submerged at design discharge so that entry of excess flow can be minimizedduring flood flows. Where the river topography and site conditions do not allow a submerged orifice intake, the second choice should bea side intake with the extension of the headrace

iii) For stream with gradients higher than 2.5%, a bottom intake (Tyrolean or streambed intake) may be selected if there are no significantboulder movements in the river during flood flows.

iv) 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.

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.

vii) Flood protection walls shall be provided along river banks to retain minimum 1/50 year floods in the river if overspills in such events candamage the initial waterways structures (e.g., headrace canal gravel trap and settling basin).

viii) A spillway with a capacity to discharge flows that enter through the intake during 1/50 year return period flood shall be incorporated asclose to the intake as possible.

A.3 Headrace


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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 aspossible.

ii) The flushing gate/valve should be sufficiently large so that supercritical flow conditions occur during flushing to remove the trappeddeposits.

iii) The flushing capacity should be such that it is possible to flush gravel size equal to the coarse trashrack spacing at the intake.iv) 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

vi) The settling basin shall be designed to settle particles larger than 0.2mm carried by the flow.

vii) A flushing system shall be incorporated in the settling basin to flush out the sediments deposited.

viii) The discharge capacity of such flushing gates, valves or cylinder shall be large enough to completely lower the water level in the settlingbasin even with incoming design flows during flushing.

ix) 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 toconstruct the gravel trap or the settling basin, the cement sand ratio in the mortar shall be minimum 1:4 and all water retaining surfacesshall 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.

ii) The forebay structure shall be constructed of either stone masonry or concrete. In case stone of masonry, the cement sand ratio in themortar 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

iii) 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 waterduring repair and maintenance, and a fine trashrack to prevent entry of floating debris and coarse particles.

iv) 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.


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and shall not be loaded onto the turbine casing.

vii) Cable ducts in the powerhouse shall be provided with adequate drainage. Slope of the powerhouse floor shall prevent water fromentering into cable ducts.

A.8 Tailrace

The requirements for the tailrace are similar to that of the headrace (canal or pipes may be used), except that the longitudinal slopesmay 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 leasttwo times the runner diameter below the turbine centerline during full flow.

ii) The tailrace outlet shall terminate either in the river bank or upstream at a safe location (e.g., stable rock outcrop) such that powerhousefoundations and adjacent land and properties are not damaged.

iii) Energy dissipating measures shall be provided at the end of the tailrace if it is likely to erode the river bank or damage land andproperties nearby.

iv) 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. Theinstallation 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 inPakistan.

ii) Electric line poles shall be treated wooden poles, local hard wood poles, concrete poles, or metallic poles. In case of metallic poles, aminimum 2 mm thick galvanized pole or minimum 3 mm thick mild steel pole red oxide primed and painted shall be used. Untreatedwooden poles kept 0.3m free above ground and supported by a section of metal of reinforced concrete buried in the ground are allowed.

iii) 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). Allmetal 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 mmrespectively .


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iv) Guy wires shall be used to accommodate any unbalanced forces from conductor tensioning or change in the direction of thetransmission or distribution line. The guy wires shall be anchored in the ground by steel plates treated with anti-corrosion paint orconcrete 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 theflushing capacity of the gravel trap, i.e., maximum gravel size that can be flushed from the gravel trap;.

ii) The fine trashrack shall comprise vertical steel bars or rods with a clear bar spacing not larger than 0.5 times the nozzle diameter incase of a Pelton turbine and 0.5 times the distance between runner blades for cross flow turbines. In any case it should not exceed 20mm to prevent entrance of fishes into the penstock pipe.

iii) The size (length and width) of the trashrack shall be such that the flow velocity through the trashrack at design flow shall not exceed0.5m/s.

iv) The trash racks shall be placed at 1:3 (V:H) slope for ease of cleaning and a suitable cleaning rack shall be provided.

B.2 Gates

i) Sluice gates shall be structurally designed to withstand full water pressure on the upstream face when there is no water downstream.

ii) Stop log gates shall not be used as main intake gates since they may have to be closed under flowing water and emergency situations.

iii) For sluice gates larger than 0.5m wide and 0.5m deep spindles or other mechanical hoisting system shall be provided for gateoperation. Simple gates without mechanical hoisting system are acceptable for gates with both sides less than 0.5 m.

B.3 Penstock

i) Unless justified by detailed financial calculations penstock pipe diameters shall be sized such that the total head loss at design flow iswithin 5% to 10% of gross head including bend, inlet and other local losses.


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iv) A by-pass around the main valve shall be provided to equalise the pressure at pressure heads above 40m and valve nominal bores of250mm 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 turbinevalve. At pressure heads above 40m, an orifice plate downstream of the drain valve shall be provided to reduce the water velocity andwear in the drain valve.

C.3 Turbine and Accessor ies

i) Turbines shall be equipped with flow regulating valve/s.

ii) 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 realisticestimates of efficiencies for other components.

iii) The bearings of the turbine must be selected and maintained to provide a minimum service life of 100,000 hours at the normal intendedoperating condition.

iv) 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 orequivalent.

vi) The turbine must be fully assembled at works. All flanges must be fitted using water resistant grease to avoid corrosion. It isrecommended that the turbine be driven by a motor at rated speed for 24 hours in the workshop. The bearing temperature must bebelow 60 o during this time.

vii) The turbine runner shall be at least statically balanced at manufacturer’s works before dispatch.

viii) Cross-Flow Turbines: The clearance between the runner and nozzle should be less than 0.5 mm


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ix) Pelton Turbines: The maximum misalignment from nozzle axis to the PCD (Pitch Circle Diameter) shall not be more than 3% of thenozzle diameter.

x) Turbine steel casings shall have adequate thickness. The turbine should not be noisy nor vibrate in a way that threatens progressivedamage.

C.4 Speed Increaser/Reducer and Couplingsi) 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).

ii) When using direct coupling between turbine and generator, the short circuit torque shall determine the capacity of the flexible coupling.

iii) Drive ratios shall be less than 3:1 for pulleys.

iv) 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.

vi) The pulley diameters used must not be smaller than those recommended by the belt and generator manufacturers, in order to preventover-tensioning of the belt and over-loading of bearings.

vii) Pulleys shall be at least statically balanced at the workshop.

C.5 Generator

i) The specified generator shall be able to continuously supply the desired output under the intended site conditions (altitude, ambienttemperature, user load/power factor).- Derating due to main load power factor (applicable to synchronous generator only):

PF lag 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

Derating 1 0.95 0.91 0.89 0.87 0.86 0.85 0.84 0.83

- Derating due to altitude

Alt, masl 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000

Derating 1 0.988 0.976 0.964 0.952 0.94 0.94 0.916 0.904 0.892 0.88 0.868 0.856 0.844 0.832 0.82


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- Derating due to ambient temperature

Temp oC 40 45 50 55 60

By class ‘F’ of insulation 1.0 0.97 0.94 0.91 0.88

By one class lower 1.0 1.0 1.0 0.97 0.94

ii) All synchronous generators shall be self-excited self-regulated type rated at 0.8 pf. Unity pf synchronous generators shall not beallowed.

iii) 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 thespecifications. Generators must have an efficiency of more than 90% at full load.

iv) Generator enclosure protection should conform to IP 23 or better.

v) It is recommended that the generator has a class F insulation – or higher.

vi) The over speed capability of the generator must correspond to the duration of runaway conditions of the turbine.

vii) The turbine and generator shall be mounted on a single steel fabrication, the base frame. This shall be fabricated from angle iron orchannel section.

viii) The bearings of the generator shall have a minimum service life of more than 100,000 hours at the intended normal operating condition.

ix) 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 voltagesurges.

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 underSC. 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


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i) The use of Electronic Load Controllers is recommended for all micro-hydro plants to generate well regulated power and facilitate theuse of electric motors and other industrial loads.

ii) Ballast dump load shall be in the form of resistive water and/or air heaters.

iii) 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.iv) 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.

vi) It shall be possible to fine tune voltage/frequency and stability.

vii) All functions of ELC and IGC shall be tested at the works (except short-circuiting).

viii) Under all normal loading conditions the voltage/frequency regulation shall be withinELC: -5% to +5% of nominal voltage and frequencyIGC: –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 valuesrespectively. Prolonged transient condition due to sudden load changes is not acceptable.

ix) Provision shall be made to adequately cool/ventilate ballast heaters at all loading condition such that the temperature rise is notdetrimental to the heater itself and/or the objects/surfaces that come in contact with the hot water/air. Water immersion resistors if usedmust be totally submerged in water by min. 10cm. Immersion heaters cable connection compartment shall have drain holes tocontinuously 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


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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 constantwater 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 ballast-load indicators kWh generation.

ii) The switchgear shall comprise feeder MCCB or MCB. The rated breaking capacity of the switchgear shall be higher than the maximumpossible fault current.

iii) Mild steel panel box shall have corrosion protection, double coat enamel painting with adequate ventilation at the bottom and at the topconfirming to IP21 or better.

iv) Cable terminations should be marked / numbered and recorded in wiring diagram to be supplied. All incoming / outgoing cables shouldend 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.

vi) All regularly operated emergency and control switches (not feeder breaker) shall be accessible from the front of the panel withouthaving to open the door.

vii) 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.

ii) The protection devices for the induction generator shall include OV as a minimum requirement (OC breaker in the excitation circuit).

iii) Breaking capacity of line break switch/MCB/MCCB should be higher than the maximum possible fault current that the generator cansupply.

iv) OL tripping limit shall be set lower than generator OL capacity.


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v) Protection level setting for generated parameters shall be as follows.OV at 5%; UV 10%; OF 15%; UF 10%.

vi) All exposed metal parts (control box, penstock) shall be connected to the system grounding. Equi-potential bondage shall be providedwithin 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 andmaintenance provisions (soaking, tightening connections, provision for periodic earth resistance measurement) to obtain minimum earthresistance (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.

vii) The overall efficiencies (water to wire) to be reached during commissioning shall be at least that quoted by supplier in his offer. Failureto meet the quoted efficiency or to produce required kW at designed head and flow may result in penalty as will be stipulated in thepurchase agreement between the buyer and the supplier.

D TRANSMISSION AND DISTRIBUTION LINES

i) For overhead lines in systems where neutral is connected to ground, the neutral wire must be placed on top.

ii) ACSR and / or Aerial Bundled Cables are to be used for overhead lines.

iii) Underground LT lines shall use armoured cables. Un-armoured cables in protective conduit may be used for short LT lines, servicelines and overhead DB connections.

iv) 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.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.

vii) Trees along ACSR overhead lines shall be trimmed to ensure that any falling tree will not touch the current carrying conductors.

viii) Over head LT lines shall observe following minimum clearance from groundLine to ground – 4.5m off-road, 5m along motor-road side and 5.5m across motor-roadHorizontal clearance - 1.2m minimum in all cases


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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) Maximum allowable transmission line-to-line voltage 400V under all normal circumstances.

xii) Back-up breaker shall be provided along distribution lines in order to discriminate faults and protect thinner cables/wires.

xiii) Lightning protection shall be provided for all current carrying conductors at the start and at the end of overhead transmission anddistribution lines. They shall be placed at 1 km intervals for longer transmission lines.

xiv) Overhead service connection shall be PVC cable (concentric or multi-core outdoor type) and the additional voltage drop shall notexceed 2%.

xv) 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.xvi) Pressure compression cable shoes / lugs and its connecting nut / bolts should be non-corrosive material.

xvii) In a 3-phase system, load to be balanced to within a variation of 20% between phases.

xviii) The neutral shall be grounded at least every 10 th pole and at every end pole. In three phase connections neutral shall be grounded atthe machine side

xix) 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.

V-3- MHP standards draft 03-07-13.pdf

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