Test method of ultrasonic cleaning

Provides the future purchaser with information allowing him to prepare the required documents, from the call for tenders up to acceptance tests and operation of electromechanical equipment. Applies to installations having outputs of less than 5 MW and turbines with diameters less than 3 m.

Guide pour l'équipement électromécanique des petits aménagements hydro-électriques

Donne au futur acquéreur des renseignements lui permettant de préparer les documents nécessaires depuis l'appel d'offres jusqu'à la réception et l'exploitation des équipements électromécaniques. S'applique aux aménagements de puissance unitaire inférieure à 5 MW avec des turbines dont le diamètre n'excède pas 3 m.

Electromechanical equipment guide for small hydroelectric installations

General Information

Status
Published
Publication Date
30-Dec-1995
Current Stage
DEL - Deleted items
Completion Date
31-Dec-1995

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SLOVENSKI STANDARD
SIST IEC 61116:1999
01-april-1999
Electromechanical equipment guide for small hydroelectric installations
Electromechanical equipment guide for small hydroelectric installations

Guide pour l'équipement électromécanique des petits aménagements hydro-électriques

Ta slovenski standard je istoveten z: IEC 61116
ICS:
27.140 Vodna energija Hydraulic energy engineering
SIST IEC 61116:1999 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST IEC 61116:1999
---------------------- Page: 2 ----------------------
SIST IEC 61116:1999
NORME CEI
IEC
INTERNATIONALE
1116
INTERNATIONAL
Première édition
STANDARD
First edition
1992-10
l'équipement électromécanique
Guide pour
électriques
des petits aménagements hydro-
Electromechanical equipment guide
for small hydroelectric installations
réservés — Copyright — all rights reserved
© CEI 1992 Droits de reproduction

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized

utilisée sous quelque forme que ce soit et par aucun procédé, in any form or by any means, electronic or mechanical,

électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission

microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher
Bureau central de la Commission Electrotechnique Inte rn Genève Suisse
ationale 3, rue de Varembé
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission PRICE CODE
IEC
MemayHapomiaa 3neKrporexHHVecKan HOMHCCHA
Pour prix, voir catalogue en vigueur
• •
For price, see current catalogue
---------------------- Page: 3 ----------------------
SIST IEC 61116:1999
-3-
1116©IEC
CONTENTS
Page
FOREWORD 7
SECTION 1 - GENERAL
Clause
1.1 Scope and object 9
11
1.2 Normative references
13
1.3 Nomenclature
13
1.4 Methodology
SECTION 2 - DESCRIPTION OF INSTALLATION AND
OPERATING CONDITIONS OF POWER STATION
13
2.1 Site conditions
15
2.2 Hydraulic conditions for plant and design criteria for the units
17 2.3 Electrical conditions for plant operation
17 2.3.1 The plant is intended to operate in isolated network
2.3.2 The plant is intended to operate in parallel with a grid which
19
imposes the frequency
19 2.3.3 Energy transport and distribution
21 2.4 Types of regulation and modes of operation
21
2.4.1 Frequency regulation
21
2.4.2 Level control
21 2.4.3 Flow regulation
21
2.4.4 Simplified governing
21 2.5 Automation, telemetry, remote control, alarms
SECTION 3 - EQUIPMENT SPECIFICATIONS
23
3.1 Technical requirements
23
3.2 Limits of the supply
23
3.2.1 For the hydraulic system
23
3.2.2 For the electric system
23 3.2.3 Elements not normally included in the supply
23 3.3 Specifications of the elements of the plant
3.3.1 Trashrack and rack cleaner 25
25
3.3.2 Water-level control
25
3.3.3 Discharge closure devices (see figure 7)
27
3.3.4 Penstock
3.3.5 Turbine (see figure 8) 29
35
3.3.6 Generator
39
3.3.7 Automatic control system
41 3.3.8 Main transformers (reference can be made to IEC 76)
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SIST IEC 61116:1999
1116©IEC
Page
Clause
41 3.3.9 Auxiliary equipment
45 3.3.10 Spare parts and special tools
45 3.3.11 Mechanical handling
45
3.3.12 Corrosion protection
45
3.4 Guarantees
45
3.4.1 General
3.4.2 Discharge closure devices 49
3.4.3 Turbine 49
3.4.4 Generator 49
49 3.4.5 Governor
51 3.4.6 Speed increaser
51 3.4.7 Comments concerning the complete generating set
51 3.4.8 Main transformer
51
3.5 General conditions for tender enquiries and comparison of tenders
53
3.5.1 Instructions to tenderers
53 3.5.2 General conditions of contract
53 3.5.3 Technical comparison of tenders
SECTION 4 – INSPECTION, DELIVERY, OPERATION
AND MAINTENANCE
55
4.1 Approval of the design and inspection of the work
55
4.1.1 Approval of design documents
55
4.1.2 Inspection of materials and sub-assemblies
55 4.1.3 Inspection at manufacturer's works
57 4.1.4 Delivery
57
4.1.5 Assembly at site
59
4.2 Commissioning
59 4.2.1 Preliminary checks before watering-up
61
4.2.2 Watering-up
61 4.2.3 Unit rotation
63 4.2.4 Preliminary checks and electrical load tests
63 4.3 Operation
63 4.3.1 Probationary period
65 4.3.2 Guarantee period
4.3.3 Normal operation 69
69
4.4 Training of personnel
4.5 Checking and maintenance 69
74 Annex A (informative) – Definitions and nomenclature
83
Tables
Figures 89
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SIST IEC 61116:1999
-7-
1116©IEC
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTROMECHANICAL EQUIPMENT GUIDE
FOR SMALL HYDROELECTRIC INSTALLATIONS
FOREWORD

The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on

which all the National Committees having a special interest therein are represented, express, as nearly as

possible, an international consensus of opinion on the subjects dealt with.

They have the form of recommendations for international use and they are accepted by the National

Committees in that sense.

In order to promote international unification, the IEC expresses the wish that all National Committees

should adopt the text of the IEC recommendation for their national rules in so far as national conditions will

permit. Any divergence between the IEC recommendation and the corresponding national rules should, as

far as possible, be clearly indicated in the latter.
This International Standard has been prepared by IEC Technical Committee No. 4:
Hydraulic turbines.
The text of this standard is based on the following documents:
Six Months' Rule Repo rt on Voting
4(CO)51
4(CO)46

Full information on the voting for the approval of this standard can be found in the Voting

rt indicated in the above table.
Repo
Annex A is for information only.
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SIST IEC 61116:1999
1116©IEC - 9 -
ELECTROMECHANICAL EQUIPMENT GUIDE
FOR SMALL HYDROELECTRIC INSTALLATIONS
SECTION 1 - GENERAL
1.1 Scope and object

This International Standard is used as a guide that applies to hydroelectric installations

with units having power outputs less than 5 MW and turbines with nominal runner
diameters less than 3 m. These figures do not represent absolute limits.

This guide deals only with the direct relations between the purchaser or the consulting

engineer and the supplier. It does not deal with civil works, administrative conditions or

commercial conditions.

This guide is intended to be used by all concerned in the installation of electromechanical

equipment for small hydroelectric plants.

This guide, based essentially on practical information, aims specifically at supplying the

purchaser of the equipment with information which will assist him with the following:

preparation of the call for tenders;
- evaluation of the tenders;
- contact with the supplier during the design and manufacture of equipment;
- quality control during the manufacture and shop-testing;
- follow-up of site erection;
- commissioning;
- acceptance tests;
- operation and maintenance.
The guide comprises the following:

a) general requirements for the electromechanical equipment of small hydroelectric

installations;

b) technical specifications for the electromechanical equipment, excluding its dimen-

sioning and standardization;
c) requirements for acceptance, operation and maintenance.

Bearing in mind the type of installation considered, the documents shall be as simple as

possible but must satisfactorily define the particular operation conditions. Over-speci-

fication is harmful to the economy of the project.
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SIST IEC 61116:1999
1116©IEC -11 -
1.2 Normative references

The following standards contain provisions which, through reference in this text, constitute

provisions of this International Standard. At the time of publication of this standard,

rties to
the editions indicated were valid. All standards are subject to revision, and pa

agreements based on this International Standard are encouraged to investigate the

possibility of applying the most recent editions of the standards indicated below. Members

of IEC and ISO maintain registers of currently valid International Standards.
rt 1: Rating and performance.
IEC 34-1: 1983, Rotating electrical machines - Pa
rt 2: Methods for determining losses and
IEC 34-2: 1972, Rotating electrical machines - Pa

efficiency of rotating electrical machinery from tests (excluding machines for traction

vehicles).
First supplement: Measurement of losses by the calorimetric method.
IEC 34-2A: 1974,
rt 5: Classification of degrees of
Rotating electrical machines - Pa
IEC 34-5: 1991,
protection provided by enclosures of rotating electrical machines (IP Code).
Field acceptance tests to determine the hydraulic performance of hydraulic
IEC 41: 1991,
turbines, storage pumps and pump-turbines.
International Electrotechnical Vocabulary (lEV), Chapter 602:
IEC 50(602): 1983,
Generation, transmission and distribution of electricity - Generation.
High-voltage alternating-current circuit-breakers.
IEC 56: 1987,
Power capacitors.
IEC 70: 1967,
rt 1: General.
IEC 76-1: 1976, Power transformers - Pa
Alternating current disconnectors (isolators) and earthing switches.
IEC 129: 1984,
Current transformers.
IEC 185: 1987,
Voltage transformers.
IEC 186: 1987,
International code for model acceptance tests of hydraulic turbines.
IEC 193: 1965,
Amendment No. 1 (1977).
First supplement to IEC 193 (1965).
IEC 193A: 1972,
International code for testing of speed governing systems for hydraulic
IEC 308: 1970,
turbines.
Guide for commissioning, operation and maintenance of hydraulic turbines.
IEC 545: 1976,
Cavitation pitting evaluation in hydraulic turbines, storage pumps and
IEC 609: 1978,
pump-turbines.

Considering the scope of this guide, it does not cover the initial stage of investigations,

that is to say the preliminary study and feasibility study. Neither does it deal with the

economic study concerning the supply and demand of energy.
---------------------- Page: 8 ----------------------
SIST IEC 61116:1999
- 13 -
1116©IEC

To conclude, the guide does not replace the necessary engineering studies for the selec-

tion, design, manufacture, installation and testing of the equipment. It is intended only to

make the purchaser aware of the important points and data to be furnished, specified and

kept in due consideration in the construction of small hydroelectric plants.
NOTES

1 The IEC standards applicable for the preparation of technical documents are given in clause 1.2. In the

case of small hydro developments, the necessary simplification relevant to the type of installation shall

be made.

2 Where IEC standards do not cover all areas of the equipment, ISO Standards concerning specific

items can be consulted, although where there is conflict between the IEC codes and the ISO Standards

those of the IEC will prevail.
1.3 Nomenclature
See annex A.
1.4 Methodology

In the interests of clarity, the sequence of the necessary steps for the construction of a

small hydroelectric power plant is represented diagrammatically in figure 1.

It principally covers the preparation of technical specifications, the examination of tenders,

the manufacture, and finally the commercial operation and maintenance of equipment.

This sequence also shows the relationship between the different phases and areas of

responsibility of all the parties concerned (consulting engineer, chief resident engineer,

and users).
ices of a
If the purchaser does not have in-house engineering capabilities or the se

consulting engineer he may call for, to facilitate relations with contractors, a "turn-key"

of the

supply, or have at least a leading contractor responsible for the supply of all or pa

electromechanical equipment (e.g. the turbine/generator package, or a "water-to-wire"

package).
SECTION 2 - DESCRIPTION OF INSTALLATION AND
OPERATING CONDITIONS OF POWER STATION

The following data is generally required by the equipment supplier and should appear in

the enquiry. In some cases, all these data are not always readily available. Nevertheless,

it must be emphasized that the more information that is given the better will the project be

understood and therefore the better the technical solution which will result.
2.1 Site conditions

2.1.1 Supply a topographic survey (plan and profile) giving the altitude of the points in-

dicated and the position desired for the main works (see figure 4), water intake, reservoir,

channel, surge tank or head pond, penstock, power plant, headwater, tailwater and their

main characteristics (sections, lengths, materials of the channels and penstocks, etc.).

Indicate the foundation conditions (sand, rock, soft ground, etc.).
2.1.2 Attach numbered pictures with cross-references to the topographic survey
described in 2.1.1, showing the setting and location of the main works.
---------------------- Page: 9 ----------------------
SIST IEC 61116:1999
1116©IEC - 15 -

2.1.3 Supply the chemical analysis of the water with extremes of temperature and, if

necessary, the amount and size of sediments carried by the water in the area around the

water intake or downstream of the sand trap, if any.
Indicate the presence of any living organisms or floating debris, etc.

2.1.4 Specify the local conditions; extremes of air temperature, humidity, occurrence of

strong winds, earthquakes, etc.
2.1.5 Indicate any transport or access limitations.

2.1.6 Certain information mentioned in 4.1.5.1 and 4.1.5.3 (erection) may also be shown

in the tender enquiry if this reflects a particular feature of the purchaser's own country.

2.1.7 State if it is run-of-river (see figure 3) or a scheme with a reservoir.

Indicate if there exist any particular operational constraints: e.g. multi-purpose scheme,

environmental, fisheries, etc.

State and describe (with drawings) those elements of the plant which are part of an exist-

ing installation which it is foreseen will eventually be put back into use.
2.1.8 State if the plant will be manned or unmanned.
2.2 Hydraulic conditions for plant and design criteria for the units
2.2.1 Specify the maximum allowable up or down surges in the channels.

2.2.2 Provide a flow duration curve (see figure 2) with an indication of the limiting flows

(guaranteed water supply, irrigation, drinking-water).
in cubic metres per second, and the availability
Qa ,
2.2.3 Specify the chosen design flow,
in days per year.

2.2.4 Specify the extreme water-levels at the intake and at the tail-race in metres (m)

above sea-level, as follows.
a) upstream max ... m
min... m
b) downstream max ... m
min... m
c) operational range allowed: ... m
and give the curves for:
level versus discharge (upstream and downstream)
level versus volume of the upstream reservoir or head pond (essential for a
reservoir scheme).

2.2.5 Specify the desired outputs and the duration of the corresponding operations.

The net heads are defined as in IEC 41. The crossflow turbines with diffusers being

considered as reaction turbines.
---------------------- Page: 10 ----------------------
SIST IEC 61116:1999
1116©IEC – 17 –
2.2.6 State the number of units suggested.

2.2.7 Define the evaluation criteria for efficiency over the full range of operation as well

as overload conditions (weighting the efficiency according to the amount of energy

produced at different heads and flows). The weight to be given to a particular efficiency or

overload depends on the time of utilization at the point of operation considered and the

energy thus recovered from the installation. For general instructions to tenderers see

clause 3.5.
NOTES

For low head plants with short intakes, care must be taken in the design of the intake in order to obvi-

ate hydraulic problems such as vortices and air admission.

2 The proper design of the waterways is essential in order to minimize the head losses (difference

between gross and net head).
2.3 Electrical conditions for plant operation

The plant electrical conditions and requirements listed under either 2.3.1 or 2.3.2.

The plant is intended to operate in isolated network
2.3.1
a) Without any other energy supply on the network
For isolated load networks, black-start capability is essential.
i) Required network voltage
- ...%
+ ... % Tolerance (under steady-state conditions)
Hz
ii) Network frequency
+ ... % – ... Tolerance (under steady-state conditions)
kW
Minimum output required all year round by the network
iii)
iv) Load acceptance rate of the network (to determine
kW/s
whether or not a flywheel is required)
Value of the maximum step-change in load which the
+ ... kW – ... kW
network can accept
vi) Power factor (cos 0)

With permanent connection to another electrical energy supply defined as follows:

type i) Hydroelectric unit:
min output ... kW
type ii) Thermoelectric unit:
iii) Generator characteristics (synchronous or asynchronous):
• rated voltage V
Hz
• rated frequency
kVA
• rated output
kg - m2
2 of rotating pa rts • inertia GD
power factor (cos 4)
iv) Turbine governor characteristics
The network conditions are to be defined as in 2.3.1 a), items i) to iv).
Voltage regulator characteristics (distribution of reactive power).
---------------------- Page: 11 ----------------------
SIST IEC 61116:1999
1116©IEC - 19 -
Energy utilization: daily and seasonal load variations
average maximum
minimum Output (kW)
Passive loads
(lighting, heating, drying, ...)
Active loads
(electric motors)
Total

In order to decide the method of regulation and the design of the governor, it is necessary

to give an indication of the load variations (load curve):
daily;
b) weekly;
seasonal.

Indicate the priority and non-priority loads (load shedding) as this is useful for designing

the governor.

The plant is intended to operate in parallel with a grid which imposes the frequency

2.3.2
a) Characteristics of the grid
V
i) Voltage
+ % -...%
Tolerance
Hz
ii) Frequency
+ % - ... %
Tolerance
iii) Short-circuit power (at the point where the
kVA
new scheme is linked to the grid)
iv) Power factor (cos 4)
Apparent output of the largest generator working
kVA
on the network
2.3.3 Energy transport and distribution
Provide the following drawings:

a general layout drawing of the entire proposed network, in the case of isolated load

operation;

a drawing showing the link to the grid, in the case of operation in parallel with a

large grid.
The layout should also show the main centres of energy consumption and supply.
Also provide information on any possible developments of the grid.
---------------------- Page: 12 ----------------------
SIST IEC 61116:1999
1116©IEC –21 –
2.4 Types of regulation and modes of operation
2.4.1 Frequency regulation
ant part of the
If the unit or the plant operates in an isolated network, or is an impo

network, a governor is required to maintain the network frequency during load changes.

For units with low output and where hydraulic energy is abundant, simplified governors

could also be used by producing a constant output at full load and dumping the unused

power.
2.4.2 Level control

Specify if it is necessary to maintain the upstream or downstream level constant, or within

a working range using the generating sets or some other discharge device. If this is so,

the turbine opening must then be governed with level feedback. This is generally the case

with run-of-river plants (in the river itself or in a bypass channel) or when linked to an

irrigation canal.
NOTE - On isolated load, level or frequency may be controlled but not both.
2.4.3 Flow regulation

Specify if the units are to provide a constant flow or a variable programmed flow.

NOTE - On isolated load, flow or frequency may be controlled but not both.
2.4.4 Simplified governing

If the plant is to operate on a large network which imposes the frequency, its units can

be fitted with simplified governors (positioners) having level feedback or load feedback.

rt of a large grid becomes accidentally
Stability may be affected in the case where pa
detached and simplified governors are used.
2.5 Automation, telemetry, remote control, alarms

a) Indicate if staff are available for the starting and shut-down sequences or if it is

required to minimize the use of operators.
b) If the plant is unattended, specify where the alarms are to be located.
c) Specify whether the starting sequence, synchronization, loading and shut-down
operations shall be:
i) manual;
ii) and/or automatic;

and/or telecontrolled (in this case, indicate the location of the control centre, the

iii)
carrier and the type and method of transmission of the signals).

d) Where a scheme has a reservoir, and there are several units, specify if manual or

automatic control of the reservoir water is required (operation according to a
programme).

e) Specify if the plant is to be the control centre for other energy supply sources in the

network.
---------------------- Page: 13 ----------------------
SIST IEC 61116:1999
1116©IEC –23
SECTION 3 – EQUIPMENT SPECIFICATIONS

The information given below is useful in establishing technical specifications and compar-

ing the technical offers for the most important items in a small hydroelectric development.

3.1 Technical requirements

In addition to supplying the equipment, the supplier should provide the following:

a) Suitability of the proposed technical solutions with regard to the hydraulic charac-

teristics and the operational requirements.
The supplier should inform the purchaser of the necessary civil work data at an

early stage so that the civil work can be designed in accordance with the requirements

of the equipment. Verification of the compatibility between the civil work and the electro-

mechanical equipment (overall dimensions, floor loads, supply and verification of the

preliminary civil work layout drawings, etc.).
c) Information required for erecting, starting-up, operating and maintaining the
equipment.
3.2 Limits of the supply

These limits should be clearly and physically defined for each item. It should be checked

that no equipment has been excluded.
3.2.1 For the hydraulic system

On the upstream side the limit could be trashrack and the rack cleaning machine, if

installed, or the first hydraulic closure device (stop-logs, gate or valve), or any other

suitable section.

On the downstream side the limit could be defined as the end of the draft tube or of the

stop-logs or gate, or any other suitable section.
3.2.2 For the electric system

This may include all the electrical equipment, up to the first point of connection with the

grid to be defined by the purchaser.
Elements not normally included in the supply
3.2.3
Generally the following are not included:
a) civil works,
b) telemetry and remote control.
3.3 Specifications of the elements of the plant

Without overlooking the criterion of simplicity which this type of installation requires, the

selection of good quality materials, suitable technology and good machine characteristics

has the advantage of affording reliability and prolonged life of the plant.
---------------------- Page: 14 ----------------------
SIST IEC 61116:1999
1116©IEC – 25 –
3.3.1 Trashrack and rack cleaner

The opening between the bars of the grating should be as large as possible, but less than

the minimum dimension of the hydraulic circuit downstream (e.g. in Francis turbines, the

minimum opening between the blades of the runner). Specify that the racks should be able

to suppo rt the loads which can be produced when they are completely obstructed.

The rack cleaning machine, if it is required, could be manual or automatic, but in any

event, the clearing away, transporting and dumping of the debris should be taken into

account.
3.3.2 Water-level control

According to the operation of the plant, the control of level could be for information, and

also for protection and auxiliary regulation.

The elements of level control are generally placed upstream of the unit (intake, dam, etc.)

although in some cases it might be necessary to control the downstream level (flow

requirements, downstream plant, etc.).

If the level measuring equipment is very remote from the power station, it shall be

protected, together with the connecting line, against electrical surge. This is particularly

impo rtant when electronic devices are used.
Moreover, the level control equipment (and other associated equipment) should be
protected against damage from environmental causes or caused by a third party.

For low head stations, in most instances, the level control can be tapped at turbine inlet

inside the power station.
3.3.3 Discharge closure devices (see figure 7)

The unit should be protected by at least one closure device, which in an emergency would

close due to lack of electrical signal (this could be the admission of air in a siphon-type

turbine) or activation by electrical signal. This device may be the guide vanes.

The opening of the gates and valves is generally performed by means of an actuator and

with balanced upstream and downstream pressures. The actuator shall have sufficient

power to enable it to open the device under unbalanced pressures.
The closure should be guaranteed under any circumstances for reasons of safety:
a) for gates, closure should be affected by their own weight;

b) while for valves and guide vanes acting as safety closing devices and not having a

closing tendency, closure should be effected by a counterweight or any other device

having an equivalent effect.

For the correct and lasting operation of the stop-logs and gates, it is necessary to maintain

the parallelism of the fixed guides.

The valves and the gates should be designed to withstand a test pressure of 1,5 times the

maximum total pressure, including surge, and to be capable of stopping the maximum

discharge, including broken penstock flow conditions.
---------------------- Page: 15 ----------------------
SIST IEC 61116:1999
1116©IEC – 27 –

It is important to study the sealing systems and to specify the guaranteed limit of leakage

to be permitted (e.g. in litres/minute). It is recommended that the seals be replaceable.

3.3.3.1 Stop-logs or maintenance gates

In certain cases, these could act as a secondary closure device, independent of the

turbine.
3.3.3.2
Intake and head gates and valves

If these devices are necessary, it is essential to study their closing rates and conse-

quences on closing to avoid unfavourable disturbances in the waterway and hydraulic

units. Suitable venting of the penstock downstream of the closure device is necessary to

prevent the collapse of the penstock or serious damage to the water conveying structure.

3.3.3.3 Inlet valves for unit protection

If the penstock is short and there is an intake gate, inlet valves are not always necessary.

If several units are fed by the same penstock, it is recommended that separate valves for

each unit be installed.

In the case of Bulb or Kaplan turbines, the use of a value on the tail-race side can in some

cases, be more conductive.

The effective rate of closure should be studied with care, establishing the optimum relation

between the overspeed of the unit and the overpressure in the penstock in accordance

with the relevant equipment.

It is especially impo ant that the closure of the inlet valve be slow, with the aim of

reducing the overpressure caused by the "water hammer" effect (and thus influencing the

design of the hydraulic pipeline), but it may result in an increased overspeed.
3.3.4 Penstock

It is advisable to use standard diameter and thickness pipes for the penstock. It should be

verified that penstocks can withstand 1,5 times the maximum total pressure including

surge to which it is subjected, taking into account the "water hammer" effect produced by

a hydraulic shut-off device or sometimes when the unit goes to runaway. The presence of

a surge chamber at an appropriate position in the hydraulic pipeline will help to reduce

pressure rises and pressure drops.

In some cases, it may be necessary to bury the penstock to protect it against rock fall,

avalanches or ice. It should be studied whether an anti-vacuum device is required.

Once the turbine is defined, the calculations for the "water hammer" effect may be

confirmed by the supplier. It is very important to bear in mind that overpressures affect the

design of the penstock, and vice versa. Depending on the penstock length and unit power

output, pressure rises may be decreased at the cost of increasing the overspeed of the

unit.
---------------------- Page: 16 ----------------------
SIST IEC 61116:1999
1116©IEC – 29 –

For the case of long penstocks and low discharge, the use of pressure relief valves

(discharge valve) is to be taken into consideration. Since this is a safety device, it calls for

careful checking and maintenance.

The use of materials other than steel for manufacturing the penstock may be considered.

3.3.5 Turbine (see figure 8)

Without wishing to exclude any particular type of construction, it should be noted that the

majority of turbines are of the impulse or reaction type.

Figure 5 gives some indication of the range covered by the largest family of turbines

(Pelton, Francis, Kaplan, propeller, and cross-flow) as a function of head and discharge.

The limits of operation of these turbines vary according to the supplier.

In all cases it is necessary that the turbines have good resistance to fatigue, cavitation,

erosion and corrosion according to the conditions imposed by the quality of the water.

The material of the unit, especially the runner and other parts subject to wear, should be

...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.