ELECTRO-MECHANICAL EQUIPMENT – SELECTION, BEST PRACTICE AND USE OF CHECKLISTS CONTENTS

1

INTRODUCTION

1

2

TURBINES

2

2.1 TURBINES TYPE 2.2 ARRANGEMENT 2.2.1 AXIS ARRANGEMENT 2.2.2 BEARING ARRANGEMENT 2.3 NUMBER OF UNITS 2.4 GEARBOX 2.5 EXPECTED ENERGY OF THE PROJECT 2.6 MAIN TURBINE TYPES: DRAWINGS AND PICTURES

2 5 5 5 6 6 6 7

3

GENERATORS

14

4

GEARBOXES

15

5

VALVES

16

6

ELECTRIC PANELS

17

7

ADDITIONAL REMARKS AND CONCLUSIONS

18

8

REFERENCES

19

1

Introduction The main choices for the SHP electromechanical equipments are related to the following topics. 1. Turbine 2. Gear 3. Generator 4. Gates and valves 5. Control panels 6. Switch boards 7. Transformers 8. Crane 9. Screen cleaner In the present paper we discuss only the first 4 items, which constitute the more relevant ones.

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Turbines The turbines are the heart of the hydroelectric plants, as they transform the hydraulic energy in the mechanical one, which is a more easily usable form of energy. The choice about the turbines is related to: • type; • arrangement; • number of units; • gear; • expected energy of the project: • others peculiar aspects of the designed plant. The table resumes the above mentioned items and the main factors involved in the choice. In the following chapters each item will be discussed more deeply. Factors

2.1

Type

H; Qmax; Qmin

Arrangement

Power station; maintenance facilities

Nr. units

Qmin

Gear

Rotation speed; cost

Expected energy

Total investment

Others

Transport facilities; delivery time; waterhammer problems, etc.

Turbines type In the long history of the hydroelectric technology, a small number of turbine types survived to the field tests, so the choice is practically restricted in a small list, depending from the net head (H) and the rated flow (Q) of the installation. Although each turbine is designed taking into consideration both head and flow rate - which are the nominal data of the machine - a first classification is traditionally given by the head only. Turbine Type Impulse

Head Classification High (>50m)

Medium (10-50m)

Low (3.000 kW

Oil

Both

1.000 - 3.000 kW

Oil

Number of units The number of units basically depends of the design minimum flow which we want to exploit in efficient and safe (from the equipment point of view) way. Each turbine type has a typical range. Turbine type

Acceptance of Q variation

Acceptance of H variation

Pelton 1 jet

20% Qmax

Low

Pelton multi-jet

10% Qmax

Low

Francis

50% Qmax

Low

Kaplan double regulated

20% Qmax

High

Kaplan single regulated

50% Qmax

Medium

Cross-flow

20% Qmax

Medium

Qmax

Low

Propeller 2.4

Gearbox The gear is a device installed between the turbine and generator increasing the rotation speed of the generator in order to reduce its cost. Form the other side, the total unit efficiency decreases of a couple of point at least and the maintenances are more expensive and difficult, especially in the vertical axis arrangement. Moreover the gearbox usually increases the noise of the unit in a significant way. Additional details on the gearbox are presented in the § 0.

2.5

Expected energy of the project The plant performance, as annual energy production, is directly connected with the unit expected efficiency, which could be a choice parameter. Turbine type

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Best efficiency

Kaplan single regulated

0.91

Kaplan double regulated

0.93

Francis

0.94

Pelton multi-jet

0.90

Pelton 1 jet

0.89

Turgo

0.85

Cross-flow

0.80

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Moving from the design point (H and Q with the best efficiency), the turbine efficiency decreases following curves which are typical of each machine type [1].

2.6

Main turbine types: drawings and pictures In the following pages are presented drawings and pictures of typical arrangement of the main turbine types.

Main turbines types

Francis

Pelton

Kaplan

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Pelton turbine

[1]

Multi-jet Pelton : vertical arrangement

3

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Multi-jet Pelton: horizontal arrangement

4

Francis turbine: vertical arrangements

5

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Francis turbine: horizontal arrangements

[5]

e6

Pelton inlet flow

Turgo inlet flow

t er je wat

Runner blades

[1]

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Francis flow

Cross-flow (Banki) distributor

runner

blades

water flow

[1]

Francis and Banki horizontal arrangement

[5]

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Kaplan turbine

[1]

Small Kaplan (1 MW) draft tube

[3]

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Small Kaplan (1 MW) spiral case

[3]

Small Kaplan (1 MW) runner

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3

Generators In comparison with the turbines, the generators of the SHP are usually a more standard product. Nevertheless some option is possible to better adjust the machine to the specific characteristics of the designed plant. The first choice is between the asynchronous (also called induction) generators and synchronous ones. Basically, the induction generators, which are less expensive and easier to manage, don’t have any own excitation device so they are suitable only for plant connected with large electric grid and under additional conditions, quoted in the table, where other options are represented. Type

Pi 3.000 kW

> 500 rpm

=

=

< 300 kW

every

Weekly

Low

Conical (bevel gear)

< 1.000 kW

every

Expensive

High

Parallel axis

< 3.000 kW

every

Cheap

High

No gear Belt

Although the gearboxes allow some money saving, we must not forget that they add an efficiency penalization to the generation unit. Type

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Efficiency

Belt

95%

Parallel

98%

Bevel gear

96%

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5

Valves As they are very simple mechanical tools, the valves can play critical roles in the hydroelectric schemes both during the normal plant management and during extraordinary events. The table shows the main criteria in choosing the valves types. Type Gate

Head losses

Diameter [mm]

Pressure [m w.c.]

Cost

2

4m

Kaplan derived

3

200 m

Pelton (single jet or multi-jet)

100 - 200 m

Turgo; Pelton multi-jet

50 - 100

Cross-flow, Francis

In the Himalayan schemes, the basic option is the synchronous generators, as these plants generally work off-grid: the load control device is strongly recommended as much as possible.

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8

References 1

Layman’s Guidebook on how to develop a small hydro site - ESHA - 2004 http://www.esha.be 2

IEC International Standard - http://www.iec.ch

3

KÖSSLER Ges.m.b.H. - http://www.koessler.com

4

Studio Frosio - http://www.studiofrosio.it

5

Cink Hydro-Energy k.s. - http://www.cink-hydro-energy.com

6

Andriz VA TECH HYDRO - http://www.andritz.com

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