Modernization of the Martigny-Bourg HPP of the Martigny-Bourg HPP ... • Maintainability becoming...

SHF - Enhancing Hydropower plants Grenoble, April 9-11, 2014

Modernization of the Martigny-Bourg HPP

Forces Motrices Martigny-Bourg SA

The Martigny-Bourg HPP

• Located in the Valais canton (Switzerland)

• Owners: the conceding communes, Forces Motrices Valaisannes SA

(FMV) and ALPIQ Suisse SA

• Operator: HYDRO Exploitation SA

• Commissioned in 1908 then modernized for the first time in the 1940’s

• 3 generating units: 8 MW, 200 m-head, double Francis turbine

• One generating unit used as a back-up

• Run of the river

• 70 millions kWh

• No major works since 1940’s except replacement of the original

penstock

• In remarkably good condition due to high quality maintenance


• Increasing doubts about the safety and reliability of the existing

turbines, spherical valves and generators (in particular highly worn

spiral case in cast iron) -> important technical and financial risks

• Maintainability becoming more and more a question due to gradual

obsolescence (unavailability of spare parts and loss of maintenance

personnel skills)

• Increasing costs of the turbine maintenance due to water heavily

loaded with suspended abrasive materials (silt), particularly during

springtime and causing significant wear of the turbine wetted areas

• Outdated turbine efficiency

• Conclusion: decision by the Owner in 2005 to proceed with

complete modernization of the power station


Initial evaluation of the condition of the power plant

by the Owner and Operator

Project managed jointly by

• The Owner: FMMB with Steering Committee chaired by ALPIQ

Suisse SA

• The Operator: HYDRO Exploitation SA

• The Engineer: Groupement d'Ingénieurs pour la reconstruction de

la centrale de Martigny-Bourg (GIMB), a contracting entity made

up of the engineering departments of PRA, kbm, Bonnard &

Gardel, Stucky SA and EDF-CIH


Organisation of the project

4 alternatives of modernisation were investigated:

• Alternative Nr.1: Rehabilitation of the current power station

mainly:

– Replacement of the 3 Francis turbines and their spherical

main inlet valves

– Reconstruction of the generators (stator core and stator and

rotor windings) including replacement of the excitation

systems

– Installation of a modern control and protection system

– Modernization of the auxiliary services (electrical and

mechanical)


Feasibility stage

• Alternative Nr.2: installation of a new Francis turbine set in the

existing building together with rehabilitation of one of the existing

units (same lines as in Alternative 1)


Feasibility stage

• An alternative Nr.3: complete construction of a

new power plant equipped with two Francis units

on grounds next to the current power plant

including demolition of the current power station.


Feasibility stage


Existing power plant

Can

ton

al

road

to be demolished

New Francis power plant

• Alternative Nr.4: complete construction of a new

power plant equipped with two Pelton units on

grounds next to the current power plant including demolition of the current power plant


Feasibility stage

The 4 alternatives were compared from economic and technical

points of view


Feasibility stage


Economic comparison

Feasibility stage


Economic comparison Clear advantage to alternative Nr.1

“Rehabilitation of the current power station”

• Considerably lower initial investment (savings from

5.5 to 11.5 MCHF)

• Considerable gain in terms of NPV (between 2.4

and 4.4 MCHF)

• Clear advantage in terms of “NPV/I” and “IRR”

(criteria that can compare projects with widely

differing capital costs, which is the case here)

Feasibility stage


• Lower construction risks: no work on the penstock nor on

the civil structures as opposed to the three other solutions

• Lower risks on the generation losses

• The only one that could allow keeping three units in

operation keeping one unit as a back-up as an insurance

against loss of production (a major financial benefit)

As a conclusion the Owners chose rehabilitation of the existing

power station as the best trade-off in terms of capital cost, risk and

performance

Feasibility stage

Technical comparison Clear advantage to alternative Nr.1

“Rehabilitation of the current power station”


Detailed design and construction works

Rehabilitation project subdivided into five lots

• Hydromechanical lot consisting of complete replacement of the three

turbines and the three spherical valves (lot awarded to RAINPOWER)

• Electrical lot consisting of rebuilding the three generators and replacement of

their excitation systems (lot awarded to CEGELEC)

• Auxiliaries, control and protection lot consisting of modernization

of electrical auxiliary services and installation of a modern control and protection

system (lot awarded to the COSTRONIC / FMO consortium)

• Civil works lot consisting of work required to adapt the new equipment to

existing civil structures (lot awarded to PRADER LOSINGER SA)

• Roofing lot consisted of rebuilding the power station roof (lot awarded to

CAROPPO METAL SA)


Time schedule

• 2006 and 2007: basic design

• 2008: bidding process

• Early in 2009: award of the 5 contracts

• 2009: replacement of the roof

• September 2010 -> July 2011: modernisation of the unit Nr.3 and

auxiliaries services

• October 2011 -> June 2012: modernisation of the unit Nr.2

• November 2012 -> June 2013: modernisation of the unit Nr.1

Detailed design and construction works


• No minor or major incident since beginning of the commercial

operation

• Turbine efficiency has exceeded the guaranteed value

• Completely satisfactory general condition of the unit Nr.3

inspected at the end of the warranty period during the autumn of

2013 (after 14,000 hours and 85,000 GWh)

• In particular excellent behaviour of the hard coating of wetted

areas (“hard-coating HVOF” by TECHNOLAB) -> Better

resistance to silt wear will reduce the general turbine overhaul

frequency from every third year (before rehabilitation) to every

five years or even every six years

Complete technical success for the project


• Increase of the mean yearly generation output by 5.4% (3.5

million kW-h) may be anticipated: 1% due to increase of

turbine efficiency and 4.4% due to increased maximum unit

power (for 3 summer months discharge that was before

spilled out can be now used for generation)

• Evolution of the budget

– at the end of the feasibility study: 15,9 MCHF

– Cost estimate at the end of the basic design study: 16,8

MCHF

– Contract award: 19,7 MCHF

– Actual project cost at its conclusion: 19.9 MCHF

Financial results


• Between rebuilding and rehabilitation the second solution in general the

most interesting in terms of risk control and capital cost

• Demanding technical specifications is an efficient means to guarantee

very high levels of longevity, reliability and performance. Financial

analysis showing that the additional investment cost (CAPEX) is quickly

compensated by the extra operating revenue (OPEX)

• Another key factor for success : an engineer with enough budget to be

able to control quality at the design, manufacturing and site installation

stages

• An engineer with enough budget to play the role of coordinator to

manage the interfaces and thus smaller lots could be specified, more in

tune with the skills of the suppliers that did not force them to hire large

numbers of subcontractors as is often the case with the so-called “turn-

key” contracts

Main lessons learnt from the project

in terms of management


• Project = good opportunity to remind of the significant

advantages of the double Francis turbines

– higher settings above tailwater level

– better cavitation requirements

– better efficiency

– wider operating range including with better part load behaviour

– limited hydraulic thrust

• As near-surgical cuts in this concrete were required to

remove the old spiral case and intake piping hydraulic

hydrodemolition was successfully used

Main lessons learnt from the project

in terms of technical aspects


Turbine before

Ateliers des Charmilles (1942) Turbine after

Rainpower (2011)

BEFORE AFTER


Spherical valve before

Ateliers des Charmilles (1942) Spherical valve after

Rainpower-D2FC (2011)

BEFORE AFTER

Modernization of the Martigny-Bourg HPP of the Martigny-Bourg HPP ... • Maintainability becoming...

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