© Acta hydrotechnica 18/29 (2000), Ljubljana
ISSN 1581-0267
69
UDK: 621.311.212.004.69 UDC: 621.311.212.004.69
Strokovni prispevek Professional paper
CELOVITA OBNOV A MALE HIDROELEKTRARNE
(PRIMER RUDNIŠKE ELEKTRARNE MEŽICA)
INTEGRAL REFURBISHMENT OF MINI HYDRO POWER PLANTS
(CASE STUDY OF A MINE HPP)
Miha PIŠLJAR, Jože TROHA, Darko BENIGAR
Glavni cilj obnove  hidroelektrarne  po 30 ali več letih obratovanja je, da se oprema elektrarne
obnovi tako, da  bo zagotavljeno nemoteno obratovanje elektrarne naslednjih 30 ali več let.
Istoč asno pa je obnova priložnost, da se poveč ata moč in proizvodnja energije, zmanjšajo stroški
delovanja elektrarne z vgradnjo sistema daljinskega vodenja. V č lanku je opisan primer celovite
obnove hidroelektrarne v nekdanjem rudniku Mežica. Po petinpetdesetih letih neprekinjenega
obratovanja  je bila obnovljena elektrarna z dvema agregatoma. Prva enota je bila v celoti
zamenjana, medtem ko je bil na drugi razvit nov turbinski rotor, druga strojna oprema pa je bila
obnovljena.  Vgrajena sta bila popolnoma nova turbinska regulatorja  in dodan nov sistem
avtomatike posamezne enote. Obnova malih hidroelektrarn je vč asih celovitejši in zahtevnejši
projekt kot obnova več jih. Izhodišč ne toč ke so enake: boljši izkoristek, več ja moč , popolna
avtomatizacija, daljinsko vodenje, minmalno vzdrževanje. Lepi cilji, ampak težko dosegljivi z
omejenimi sredstvi namenjenimi obnovi elektrarne.
Ključ ne besede: obnova, orodje CFD, sistem upravljanja, regulator
The purpose of the integral refurbishment of old power plants is to bring the power plants into a
condition that will enable them to work for the next 30 or 40 years without needing new
expenditure. At the same time, a refurbished power plant has to produce more energy, operate
automatically and require less maintenance work. A case study of such an integral refurbishment of
the ex-mine power plant is presented in the article. A two-unit power plant was refurbished after 55
years of uninterrupted operation. The first unit was totally exchanged with a new one. On the
second machine, a new runner was developed and other mechanical equipment was renovated.
Also, on both units, new governors were built, and a full automatic system was created.
Key words: Refurbishment, CFD tool, Control system, governor
1.  UVOD
Glavni namen celovite obnove elektrarn je
podaljšati življenjsko dobo elektrarn za 30 do
40 let. Obnova male hidroelektrarne je
podobna obnovi velike hidroelektrarne, vendar
z bistveno manj denarja. Polega tega so male
hidroelektrarne spremenile svojo vlogo v
elektroenergetskem sistemu. V č asu izgradnje
so bile projektirane za vzdrževanje lastnega
električ nega omrežja, danes pa so pretoč ne in
morajo optimalno “predelati” razpoložljivo
vodno energijo
Obnova obič ajno ni le obnova ali
zamenjava  obstoječ e opreme, ampak tudi
preprojektiranje agregata. Vsaka obnova  se
mora zač eti s kratko študijo o izplač ljivosti
obnove in preprojektiranja elektrarne. Pri tem
je treba:
1.  INTRODUCTION
The purpose of the integral refurbishment
of old power plants is to bring them into
condition to work for the next 30 or 40 years
without any greater later investment. he
refurbishment of small hydro units is generally
similar to the refurbishment of larger ones, but
can be accomplished with a relatively smaller
budget. Small units also change their role in
the electrical system. When they were first
assembled, some 40 or more years ago, they
were relatively large units and very often they
had to maintain an island net.
Refurbishment today does not mean only
the renovation of existing electro-mechanical
and hydraulic equipment, but also the
redesigning of units. Every refurbishment has
to begin with a short feasibility study in which
the next points have to be executed:

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
70
− ugotoviti podrobno stanje obstoječ e
opreme.
− raziskati vodne razmere
− poiskati in prebrskati obstoječ o
dokumentacijo!
− izmeriti karakteristike stare turbine!
− ugotoviti, pod kakšnimi pogoji je varno
obratovanje  elektrarne brez posadke?
− kam z obstoječ o posadko?
− ugotoviti posebnosti posamezne elektrarne,
ki vplivajo na obratovanje, proizvodnjo,..
Č e študija da pozitivne odgovore na
navedena vprašanja, potem sledi izdelava
projekta, ki mora  zagotoviti:
− boljšo izrabo potencialne vodne energije
− varno in zanesljivo  delovanje agregatov in
elektrarne
− visok in sodoben  nivo tehnič nih rešitev
− za okolje prijazne rešitve
− avtomatsko delovanje agregatov in druge
opreme v elektrarni nadzorovano preko
sistema daljinskega nadzora.
Danes obnova ne pomeni samo vnovič ne
izdelave delov, ki so poškodovani ali
obrabljeni, temveč je treba upoštevati nova
spoznanja in tehnič ne rešitve s področ ja
hidravlič nih strojev in hidroelektrarn. Tako
oprema ne bo samo obnovljena, ampak se
dvigne na višjo tehnič no raven. Obstoječ i
vodni potencial je bolje izkorišč en na podlagi
višjega izkoristka obnovljene opreme in
poveč anega pretoka. Rezultat je več ja moč agregata kot celote in več ja proizvodnja
energije
Poveč an pretok in več ja izhodna moč agregata zahtevata poglobljeno študijo drugih
delov opreme s stališča hidravlič nih,
mehanskih in električnih možnosti,
stabilnosti,… Sprememba glavnih parametrov
agregata ne sme imeti nobenega vpliva na
varno in stabilno delo celotnega sistema
agregata in elektrarne.
 2. TEHNIČ NI PROBLEMI
OBNOVE
 
Obnova izpostavlja množico specifič nih
problemov. Na agregatu se največ krat
pojavijo problemi z možnimi rešitvami,
predstavljenimi v preglednici 1.
− Α detailed examination of the existing
equipment condition.
− Ascertain the water power  conditions.
− Perform a survey of available
documentation!
− Measurement of old turbine and generator
characteristics!
− Determine how safe the operation of the
power plant will be in the future without a
staff?
− Decide how to solve the problem of
employees after the refurbishment?
− Solve many other case-to-case specific
problems.
If the feasibility study gives the proper
answers, the refurbishment of power plant
equipment enables:
− Better exploitation of water energy
potential
− Safe and reliable operation of each unit and
of the entire power plant
− Α higher level of particular technical
solutions
− Safer technical solutions for the
environment
− Units and power plant automation and
remote control operation.
Following the rule of technical updating,
new components should not only include the
remaking of the old ones, but also feature up-
to-date technical achievements in the field of
water units design and manufacturing. In this
way, the equipment will not be only
refurbished, but its technical level will also be
upgraded. This leads to better exploitation of
the existing catchment. Better exploitation is
based on better efficiency and increased
discharge, which results in higher turbine and
unit power output, higher energy production
and a shift of production to the field of peak
demand.
Increased discharge and unit output requires
an intensive investigation of all unit elements
in the sense of hydraulic, mechanical and
electrical ability and stability. A change of one
parameter must not have undesirable results
limiting the ability and stability of the whole
unit and system.
 2. TECHNICAL PROBLEMS OF
REFURBISHMENT
 
The refurbishment of units presents many
specific problems. Within the unit, the next
problems appear, and possible solutions are
given in Table 1.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
71
Preglednica 1.  Pregled delov agregata in dela na njih. 
Del agregata Stara oprema Obnova
Gonilnik Stari gonilnik je obrabljen,
poškodovan zaradi kavitacije,
erozije, pojavljajo se razpoke.
Novi gonilnik ima novo hidravlič no  obliko.
Izpolniti mora vse zahteve po višjem
izkoristku in poveč anem pretoku.
Da se zniža cena, se uporabi poenostavljena
izdelava varjene izvedbe gonilnika.
Turbinska gred Utrujen material, razpoke Nova gred omogoč a poveč ano moč agregata
Nosilni ležaj Obič ajno je obrabljen Obnova (bele kovina) ali vč asih zamenjava
Vodilne lopatice Stare lopatice puščajo (v
zaprtem položaju) in ne
dovoljujejo poveč anega odprtja.
Skrajšane vodilne lopatice (po popravilu)
rešijo oba problema.
Gonilnikov
labirint
Relativno velike volumetrič ne
izgube
Zmanjšanje izgub
Drsne puše Stalno mazanje in onesnaževanje
vode.
Samomazalne puše – ni več potrebnega
vzdrževanja in ni onesnaževanja okolja.
Tesnilka Usnjene tesnilke  pušč ajo Nova tesnilka ne pušč a
Regulacijski
obroč Dvojni obroč togo povezan z
regulatorjem. Omejeno
odpiranje
Podaljšan obroč, povezan z novim
servomotorjem, delujoč im na visokem tlaku
olja.
Regulator Obič ajno dotrajan s težavami pri
vzdrževanju (ni več rezervnih
delov, slaba natanč nost
regulacije, nizek tlak olja.
Hidravlična naprava z zrač nim
akumulatorjem, standardnimi hidravlič nimi
elementi, visok obratovalni tlak, procesorski
turbinski regulator vgrajen v opremo
avtomatike agregata.
Predturbinski
ventil
Pušč a, roč no upravljanje Nova tesnila, obnovljen z mehanizmom za
avtomatsko odpiranje/zapiranje.
Generator Izolacije razreda B, izstrošeni
ležaji
Nova izolacije razreda F omogoč a
poveč anje moč i. Obnova ležajev enako kot
pri turbinskih ležajih.
Vzbujalni
sistem
Dinamič ni vzbujalnik z roč no
regulacijo napetosti
Novo statič no vzbujanje z avtomatskim
primarnim napetostnim  regulatorjem..
Mehanske
meritve
Nekaj membranskih
manometrov in termometrov
Novi elektronski pretvorniki za merjenje
nivojev, tlakov, temperatur
Električ ne
meritve
Klasič ni instrumenti Pretvorniki električ nih velič in z instrumenti
in signali, pripeljanimi na sistem  vodenja
agregata.
Mehanske
zašč ite
Ni posebnih zašč it Sistem zašč it agregata, ki obsega:
− varnostni hitrostnik
− merjenje temperatur na ležajih, navitju
generatorja
− kontrolo tlakov v oljetlač nem sistemu.
Sistem vodenja Ni sistema vodenja. Roč no
obratovanje
Novi PLC sistem, ki zagotavlja avtomatski
zagon in zaustavljanje agregata, turbinsko
regulacijo, sekundarno regualcijo faktorja
moči, električne in mehanske meritve,
signalizacijo in daljinski nadzor.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
72
Table 1. List of the turbine unit parts and measures.
Unit  part Old Refurbish
Runner Old runner is worn out and
suffers from  fatigue crack.
New runner has new hydraulic shape. It has
to fulfil new requirements  due to efficiency
needs and greater flow.
To lower costs, a simplified construction by
welding the blades between the hub and the
rim is applied.
Turbine shaft Fatigue problems and damaged
shaft.
New turbine shaft also allows greater power
output and meets other requirements.
Radial axial
turbine bearing
Is usually worn out. Repair, or maybe replacement.
Guide vanes Old guide vanes leak and do not
afford an increase in the
opening.
Shorter guide vanes (by repair) solve both
problems.
Runner band
labyrinth
Relatively large volumetric
loses.
Reduces  volumetric loses.
Sliding bushes Periodically greasing and grease
in water (pollution).
Self-lubricated bushes – no maintenance and
no environmental problems.
Shaft seals Leather seals had great leakage. New rubber seals -  no leakage.
Regulating ring Double arm, connected to
governor. Limiting opening.
Extended regulating ring with new actuator,
prepared for higher oil pressure.
Governor Usually worn out; difficult to
maintain (no spare parts),
inaccurate, low pressure.
High pressure with standard hydraulic
elements, hydro pack with air accumulator,
digital governor integrated into main
START/STOP automation.
Turbine valve Leakage, manual drive. New seals,  automated with new hydraulic
actuator.
Generator Class B insulation, exhausted
bearings.
New class F insulation, which also allows
greater output power. Bearing repairn as
turbine bearing.
Excitation
system
Dynamic exciter with manual
voltage control.
New static excitation system with automatic
primary voltage control system. Secondary
control from Unit control system.
Mechanical
measurement
Some  piston  manometers. New pressure, level and temperature
transducers.
Electrical
measurement
Classical instruments. Transducers for electric values.
Mechanical
protection
No special protection systems. New overspeed device, level, pressure and
temperature protection in bearing, hydraulic
pack and generator stator wire.
Control system No control system. Manual
operation.
New PLC control system, which includes
Start/Stop sequence automation, turbine
governor, secondary reactive power control,
electrical and mechanical measurement and
annunciation.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
73
Vsaka obnova opreme je povezana z
mnogimi problemi  in vprašanji, posebno v
povezavi z omejitvami stroškov, č asa, prostora
gradbenimi deli. Optimizacija med vsemi
omejitvami, željami, možnostmi je eden
najpomebnejših korakov v procesu obnove
hidroelektrarne.
 
 3. OBNOV A STROJNE OPREME
 
Strojna oprema agregata zajema
predturbinski ventil, turbino s špiralo, sesalno
cevjo, vodilnikom in gonilnikom ter turbinski
regulator. V č lanku je  predstavljen postopek
izrač una novega gonilnika, numerič na analiza
toka in zamenjava regulatorja.
 
 3.1 NOVI GONILNIK
 
Geometrijske danosti stare opreme vključ no
s hidravličnimi oblikami  (špirala s
predvodilnikom, vodilnik, premer, spodnji
turbinski pokrov in sesalna cev)  so omejitve
pri hidravličnem projektiranju novega
gonilnika. Splošna priporoč ila so:
− Poveč a se vstopni premer. Na ta nač in se
zmanjša vstopni kot.
− Podaljša se dolžina venca, tako se  posredno
podaljša lopatica. Zmanjša se okavitacijska
obč utljivost.
− Manjši vstopni kot in daljše lopatice
obič ajno dajejo boljše lastnosti.
− Po pravilu ostaneta višina  vodilnika in
vstopni premer sesalne cevi
nespremenjena.
 
Oblikovanje površine lopatice  je izvedeno
z navidezno tridimenzijsko inverzno metodo
(Q3D). Lopatice so oblikovane s konstantno
debelino na prveh dveh tretjinah površine, na
zadnji tretjini pa se tanjšajo. Stari in predlog za
novi gonilnik sta se analizirala z uporabo
orodij numerič ne analize (CFD). Na podlagi
analize toka skozi vodilne lopatice in gonilnik,
je bil optimiran vstopni kot lopatic gonilnika.
 
 
 
 
Any refurbishment of the equipment is
connected with many problems and questions,
particularly due to the limitations of cost, time,
space, and civil works.  Optimising among all
the limitations is the most important step in the
process of refurbishment of the power plant.
 
 3. MECHANICAL EQUIPMENT
REFURBISHMENT
 
The mechanical equipment of the hydro
unit consists of a valve, a turbine with a spiral
case, a draft tube, and a wicket gate and
runner. In the paper, we present the procedure
in more detail, with new runner calculations, a
numerical flow analysis and a change of the
governor.
 
 3.1 REDESIGN OF RUNNER
 
The geometrical constraint of the old
hydraulic shape (a spiral case with stay vanes,
guide vanes, a pitch diameter and control
mechanism, a bottom turbine cover and a draft
tube inlet) limits the possibilities of the free
hydraulic design of the spare runner. In
general, the following is recommended:
− Increase the inlet diameter. It reduces the
inlet angles according to an up-to-date
praxis.
− Extend the length of the rim, and
consequently, the length of blade. It reduces
the cavitational susceptibility.
− Smaller inlet angles and longer blades
usually give better results.
− As a rule, the guide vane height and draft
tube inlet diameter remain unchanged.
 
The design of the blade surface is obtained
by using a quasi three dimensional (Q3D)
inverse method. The blade is profiled with
constant thickness over the first two thirds, and
thinning is profiled in the last third. The old
runner and the proposals for the up-graded
runner are analysed using the CFD tool. On
the basis of flow analyses through the guide
vanes and runner, inlet angles of the blade are
adjusted. Other modifications are feasible as
well, but all of them have to be verified by
using a CFD tool.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
74
 3.2 NUMERIČ NA ANALIZA TOKA
 
Priporoč ljiva je analiza vseh turbinskih
delov: špirale s predvodilnikom, vodilnika,
gonilnika in sesalne cevi pri različ nih pretokih-
odprtjih vodilnih lopatic. V opisanem primeru
je bil uporabljen program TASC FLOW.
Glavni namen analize je bil predvideti
pretoč ne razmere in izgube v vsakem delu
tubine in zagotoviti mejne vrednosti za
nadaljnje izrač une.
Natoč ne razmere na vodilnik so določ ene za
obliko špirale.  Nova oblika vodilnih lopatic pa
zagotavlja boljše  pogoje za natok na gonilnik.
Novo oblikovani gonilnik se primerja s
starim. Najprej se analizira stari gonilnik pri
različ nih odprtjih vodilnika. Nato pa določ i
novi in analizira pri istih odprtjih, tako da se
primerjajo primerljivi rezultati.
Rezultat pretoč nih prerač unov so prostorske
razporeditve hitrosti, tlakov in vektorji hitrosti
vzolž lopatice.
Da se dobi optimalna oblika lopatice se  za
različ ne modifikacije gonilnika ponovi analiza,
dokler se ne dosežejo željeni parametri
(izkoristek in kavitacija).
Sesalna cev se obič ajno ne spreminja.
 
 3.3 REGULATOR
 
V starih agregatih so mehanski
centrifugalni regulatorji, ki jih je nemogoč e
vključ iti v avtomatsko obratovanje agregata,
poleg tega jih je vedno teže vzdrževati in ne
zagotavljajo kakovostnega obratovanja.
Modernizacija starih regulatorjev je mogoč a
na dva nač ina:
1. Samo z obnovo obstoječ ega centrifugalnega
regulatorja, ki se obnovi, opremi z
elektromotorji in električ nimi merilnimi
pretvorniki ter s senzorji. Servomotor
ostane isti. Regulator še vedno regulira
hitrost, vendar je mogoč e z njim upravljati
preko nadzornega sistema upravljanja
agregata. Obič ajno v takem primeru
regulator regulira frekvenco do uspešne
sinhronizacije, zatem pa prevzame
regulacijo moči ali nivoja sistem
upravljanja agregata.
 3.2 NUMERICAL FLOW ANALYSIS
 
Analysing all turbine parts is
recommended: the spiral case with stay vanes,
different openings of guide vanes, the runner
and draft tube. In the  Turboinstitut, a
computer code TASC flow is used.
The main purpose of the flow analysis is to
predict the flow properties and losses in each
part of the turbine and to obtain boundary
conditions for further calculations.
The shape of the spiral case dictates the
inlet angle to the distributor. A new guide vane
profile has to provide the improved runner
inlet conditions.
The newly designed runners are compared
with the old ones. First, a flow through the old
runner is analysed for several operating points
pertaining to the appropriate guide vane
openings.
The result of the flow calculation is a fully
3D-velocity vector field, and streamlining and
pressure distribution along the blade,
predicting the runner cavitational behaviour.
To obtain a better runner design, the
proposed new runner blade is modified where
necessary and numerically analysed for the
same operating points. The procedure is
repeated more times until a runner with the
required performances (efficiency and
cavitation) is obtained.
Usually the draft tube remains unchanged.
 3.3 GOVERNOR
 
Existing governors on old hydro power
plants are generally still centrifugal
mechanical governors without the possibility
of being included in the remote control system
and they have numerous accuracy and
maintenance problems. Modernisation of the
old governors is possible in two ways:
1. Refurbishing only the existing centrifugal
governor and furnishing it with
electrometers and sensors. The actuator
remains the same. The governor still
controls the unit speed, but it is possible to
manipulate it with the remote control
system.  Usually the governor controls
speed only during the synchronisation
period. After synchronisation, the remote
control system controls the unit power or
water intake level.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
75
2. Zamenjava regulatorja in servomotorja z
novo oljetlačno napravo, zrač nim
akumulatorjem in novim visokotlač nim
servomotorjem.  Nova oljetlač na naprava je
skupna tudi za krmiljenje druge opreme
agregata - predturbinski ventil, zavoro.
Digitalni turbinski regulator je lahko
samostojna enota, pri manjših agregatih pa
je elektronska oprema skupna s sistemom
vodenja agregata. Novi regulator mora
zadostiti naslednjim zahtevam:
− Zanesljivost - vsi elementi morajo biti
zanesljivi. Zanesljivost se poveč a z
zmanjševanjem vgrajenih elementov
(integrirani sistem vodenja).
− Uporaba standardnih industrijskih
elementov hidravlike, merilnih
pretvornikov, PLC. Na ta nač in se
znižajo stroški vzdrževanja, ki mora biti
hitro in preprosto.
− Uporaba visokih tlakov-  danes se
obratovalni tlaki hidravličnih naprav
gibljejo od 60 do100 barov.  Z višanjem
obratovalnega tlaka se manjšajo
dimenzije ventilov, povezovalnih cevi in
druge opreme.
− Za vse uporabnike  v okviru agregata ena
sama oljetlačna naprava- vodilnik,
predturbinska loputa, obtočni ventil,
zavora,..
− Nizka poraba energje - zrač ni
akumulator se polni le obč asno, ko pade
tlak v sistemu.
− Vzdrževanja je malo in je preprosto. Z
digitalnim regulatorjem in elektronskimi
pretvorniki  se zgradi sistem, ki ne
zahteva  posebnih nastavitev.
− Inteligentni komunikacijski vmesniki, ki
zagotavljajo komunikacijo z nadzornim
sistemom. Ni več potrebnih posebnih
koncentratorjev signalov.
− Možnost roč nega upravljanja s turbino.
− Vgrajene mehanske zaščite- visoka
temperatura, nizek tlak. previsoka hitrost
2. Changing of the governor and actuator with
a new hydraulic pack, an air accumulator
and a new high-pressure servomotor. An oil
hydraulic pack and a digital governor
control the other governor equipment. In
smaller units, a digital governor can be a
part of the software in the Unit PLC. The
new governor has to fulfil following
requirements:
− High reliability - all elements have to
have high reliability.  Reliability also
increases if the number of elements
decreases (integrated unit control
system).
− Use of standard hydraulic, sensor and
control elements. The term “standard”
means market wide spread elements.  In
this case, maintenance is simple and
cheap.
− High-pressure hydraulics  - today
utilised oil pressure is normally 60 bars,
but for smaller units, can be also 100
bars. When the pressure is higher, all
dimensions of pipes and actuators are
reduced.
− Same hydraulic pack for all actuators of
the unit – by-pass valve, main turbine
valve, brake, and wickets gate.
− Low power consumption-air
accumulator needs only intermittent
pump work and has lower energy
consumption.
− Simple maintenance and simple
adjusting procedure. Standard elements
allow simple and infrequent
maintenance. With a digital governor
and new transmitters it is also possible to
build a governor with no adjustment.
− Direct connection with remote control
system and supervising system. A stand-
alone governor has to have a standard
intelligent interface with all data, and be
prepared to transmit and to receive
commands from the Unit control system.
− Possibility of manual operation with the
unit.
− Integrated mechanical protections -
level, pressure temperature, etc.
 
 
 
 
 

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
76
 4. OBNOV A SISTEMA
UPRA VLJANJA
 
Upravljanje s starimi elektrarnami je
zaslužilo svoje ime - res se je rokovalo – vse
se je upravljalo roč no. Meritve, signalizacija
sta bila izvedena s klasič nimi instrumenti in z
žarnicami. Sinhronizacija je izključ no roč na.
Stalna prisotnost posadke je bila obvezna.
Novi sistemi upravljanja pa mora imeti
vgrajene nasledne funkcije:
− popolni avtomatski zagon/zaustavljanje
agregata
− vgrajen mora biti merilni sistem za merjenje
mehanskih in električ nih velič in.
− sistem signalizacije
− komunikacija na nadzorni sistem
− avtomatska sinhronizacija (z možnostjo
roč ne).
 
Sodobni PLC sistemi z ustrezno
programsko opremo omogoč ajo realizacijo
vseh zgoraj naštetih zahtev v okviru enega
samega integriranega sistema upravljanja. Za
manjše enote je lahko vgrajen tudi turbinski
regulator v isto strojno opremo. Takšen sistem
je:
− zanesljiv
− preprost za uporabo in vzdrževanje
− cenovno ugoden
− zagotavljati mora delovanje brez posadke.
 
Pri projektiranju obnove elektro-strojne
opreme, je pomebno, da se predvidijo vsa
potrebna dela za pripravo agregata za
avtomatizacijo:
− vgrajeni morajo biti vsi senzorji in merilni
pretvorniki
− predvideni morajo biti vsi izvršni elementi
(motorji, ventili,…).
V integrirani sistem PLC vsak signal vstopa
samo enkrat. Informacija se potem uporabi v
več namenov - enkrat za zagon/zaustavitev, za
turbinsko regulacijo, signalizacijo, daljinski
sistem vodenja,...
Električ ne zašč ite generatorja so loč ene  in
delujejo neposredno na generatorsko stikalo.
Nekatere mehanske zašč ite so  izvedene preko
PLC (na primer temperatura ležajev,
generatorskega navitja,)...
Izhodni signali- ukazi delujejo neposredno
na elektromehanske č lene.
Roč no upravljane je omogoč eno v dveh
režimih - testnem, kjer se deluje neposredno na
izvršne č lene, in roč nem, kjer se upravlja
preko PLC sistema posredno.
 4. CONTROL EQUIPMENT
RENOV ATION
 
Old small (and also larger) hydro units have
only manual or perhaps a sort of semi-
automatic control system.  Other functions
such as measurement and annunciation were
realised with stand-alone instruments, panel
lamps. Synchronisation is, in most cases, only
manual. A permanent staff is required.
A new control system has to realise the next
functions:
− start/stop unit completely automated
− electrical and mechanical measurement
system
− annunciation system
− communication  interface to remote
supervision  system
− automatic synchronisation
 
Recent PLC systems, with proper software,
carry out all upper functions in only a single
hardware system-integrated control system.
For small units, the turbine governor can also
be incorporated in the same hardware. Such a
system is:
− highly reliable
− simple to  use and maintain
− simple to adjust
− price/performance optimal
− allows a no-staff power plant operation
 
When designing the unit refurbishment, it is
important to provide all the necessary work to
prepare the unit for full automation:
− All sensors and transducers have to be built
in.
− Control elements, such as motors and
solenoid valves have to be prepared.
Due to the integrated system, each input
(digital or analogue) enters into the PLC only
once. Information is later used for all the
necessary purposes - start/stop automation, the
governor, annunciation, supervision, etc.
Electrical generator protections are separated
and act directly on the generator circuit
breaker. Some mechanical protections, such as
the bearing and winding temperature are
realised with the PLC system.
Output commands act upon the proper
electromechanical actuators.
Manual control is also possible in test and
normal manual mode.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
77
5. ELEKTRARNE V OPUŠČ ENEM
RUDNIKU SVINCA MEŽICA
Leta 1940 je lastnik rudnika svinca v
Mežici zač el izkorišč ati vodni potencial reke
Meže. Med vojno, leta 1 941 , je bila vgrajena
prva enota - dvojna Francis turbina in
generator, ki sta bila izdelana pri Ganzu v
Budimpešti. Drugi agregat - Francis turbina je
bila izdelana pri Voithu, medtem ko je
generator Brown Boveri zač el obratovati leta
1948 (slika 1, preglednica 2).
5. HYDRO POWER PLANTS OF
THE LEAD MINE MEŽICA
In 1 940 an owner of the Mežica mine »The
Central European Mines Ltd« began
projecting for the exploitation of the Meža
stream. During the war in 1941, the first unit –
a twin Francis turbine and generator - were
manufactured by Ganz, Budapest, and installed
(PE1/1). The second unit - a Francis turbine
made by Voith St. Poelten in 1942 and a
generator Brown Boveri - were installed after
the war in 1948 (Figure1, Table 2).
Preglednica 2. Parametri stare in nove turbine.
Table 2. Parameters of old and new turbines.
PE1/1 Prej / Old Potem / New
Padec / Head 65 m 65 m
Pretok / Flow 1.3 m
3
/s 1.5 m
3
/s
Hitrost / Speed 750 rpm 750 rpm
Moč / Power 1100 kW 1450 kW
Leto izdelave / Year of erection 1943 1998
PE1/2 Prej / Old Potem /New
Padec / Head 65 m 65 m
Pretok / Flow 0.7 m
3
/s 0.8 m
3
/s
Hitrost / Speed 750 rpm 750 rpm
Moč / Power 700 kW 800 kW
Leto izdelave  / Year of erection 1948 1998
Slika 1. Enota  PE2/1  (izdelava  Voith/Brown Boveri) pred obnovo.
Figure 1. Unit PE2/1  (produced by Voith/Brown Boveri) before refurbishment.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
78
Oba  turbinska regulatorja sta bila izdelana
pri VOITH St. Poelten.  Zaradi nezanesljivosti
delovanja, oteženega vzdrževanja in
predvidene popolne avtomatizacije elektrarne
je bila potrebna celotna zamenjava
regulatorjev.
Na obeh agregatih sta bila turbinska
regulatorja zamenjana. Slika 2 prikazuje
hidravlič no shemo obeh regulatorjev. Zaradi
bližine obeh  turbin  je bila izbrana ena sama
oljetlačna naprava, s skupnim  zrač nim
akumulatorjem, vendar z ločenim nizom
krmilnih ventilov. Za krmiljenje vodilnika je
bil izbran proporcionalni ventil. Elektronski
del regulatorja je bil vgrajen v  PLC sistem
upravljanja. PLC sistem z ustrezno
programsko opremo zagotavlja, avtomatsko
delovanje agregata, turbinsko regulacijo,
merjenje, regulacijo nivoja, moč i in pretoka ter
komunikacijo z nadzornim sistemom. Vsi
podatki in  zahtevani parametri so dostopni na
zaslonu, vgrajenem na prednjih vratih
upravljalne omare.
Na generatorju ni bilo potrebnih posebnih
del. Sam generator je bil obnovljen nekaj let
pred obnovo. Stari roč ni sistem vzbujanja  je
zamenjal novi statič ni vzbujalni sistem z
elektronskim regulatorjem napetosti.
Obnova prvega agregata je bila uspešna, Na
sliki 3 sta prikazani krivulji izkoristka in moč i
stare in  nove turbine. Fotografija na sliki 4 pa
prikazuje novi agregat.
VOITH St. Poelten made all three
mechanical governors. In spite of permanent
maintenance, the turbine equipment needed
extensive refurbishment. The owner’s goal - to
introduce remote control - has dictated
considerable modernisation.
New governors were created on both units.
Figure 2 shows the hydraulic scheme of both
the hydraulic parts of the governors.   There is
only one oil reservoir and one air accumulator
with two separate sets of control valves. A
proportional valve is used for wicket gate
control.  The electronic digital part of the
governor was realised as a part of an integrated
PLC control system. The PLC, with proper
software, executes all start/stop automation
functions, level and power control, speed
control, and measurement of all electrical
parameters. All information is presented on an
MMI monitor on the front cubicle doors.
There were no special works on the
generator, except excitation. There was a new
static excitation system.
Refurbishment of first unit was very
successful. Figure 3 shows the old and the new
efficiency and power results. On Figure 4, the
upgrading unit is shown.
Slika 2. Hidravlič na shema regulatorja.
Figure 2. Hydraulic scheme of governor.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
79
0
10
20
30
40
50
60
70
80
90
100
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8
Discharge Q (m
3
/s)
Efficiency η η η η (%)
0
100
200
300
400
500
600
700
800
900
Turbine power P
t
 (kW)
η - new
η - old
P
t
 - new
P
t
 - old
Slika 3. Karakteristike stare in nove turbine.
Figure 3. Old and new runner characteristics.
Slika 4. Poveč ani agregat PE1 /1 .
Figure 4. Upgraded  and refurbished unit PE2/1.

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
80
Slika 5. Novi agregat  PE1 /1 moč i 1 .45 MW.
Figure 5. New unit PE1/1 of 1.45 MW.
Stari agregat PE1 /1 je imel več je poškodbe
na ležajih in gredi. Turbinska oprema je bila
dotrajana, generator pa ni dovoljeval
poveč anja moč i. Stari agregat je bil v celoti
zamenjan z novo horizontalno Francis turbino,
s sinhronim generatorjem z drsnimi ležaji,
predturbinsko loputo z avtomatskim
upravljanjem in z varnostno utežjo za
zapiranja. Turbina nima lastnih ležajev, pač pa
je rotor turbine prevesno nameščen na
Unit PE1/1 suffered serious injuries on its
bearings and shafts. The turbine equipment
was worn out and the generator did not allow
for upgrading. The old Unit was substituted
with a modern single Francis unit with a
horizontal axis spiral a Frances turbine, a
synchronous generator with slide bearings, a
butterfly valve with an 0,8 m diameter, and a
bifurcation of 1,4/0,8 m diameter, a flywheel
and an over-speed device. The turbine does not
have its own bearings. The runner is directly

Pišljar, M., Troha, J., Benigar, D.: Celovita obnova male hidroelektrarne (primer rudniške elektrarne Mežica) -
Integral Refurbishment of Mini Hydro Power Plants (Case Study of a Mine HPP)
© Acta hydrotechnica 18/29 (2000), 69-81, Ljubljana
81
podaljšano gred generatorja. Turbinski
regulator je v celoti nov. Sistem upravljanja je
enak sistemu upravljanja obnovljenega
agregata PE1/2. Na sliki 5 je prikazan novi
agregat.
mounted on the generator shaft.  The governor
is completely new. The control system is the
same as in the refurbished unit PE2/1. It is also
a voltage control system. Figure 5 shows the
new unit.
5. ZAKLJUČ KI
Obnova in povečanje moči malih
hidroelektrarn je zahteven poseg, tako kot pri
velikih elektrarnah. Obnova male
hidroelektrarne je lahko temeljitejša kot
obnova velikih enot. Dosežki pri poveč anju
izkoristka so  opazni in uporaba CFD orodij
daje uporabne rezultate. Izkušnje in rezultati
modelnih raziskav in preizkusov ter CFD
orodje skupaj dajeta dobro  in zanesljivo
napoved poveč anja izkoristka.
Turbinski regulatorji, sistemi vodenja,
napetostni regulatorji predstavljajo opremo, ki
mora biti zamenjana. Sodobni  sistemi so
zanesljivejši, potrebujejo manj vzdrževanja in
omogoč ajo daljinski nadzor.
5. CONCLUSIONS
The upgrading and refurbishment of a small
hydro plant is as considerable as that of larger
ones. The refurbishment of a small hydro plant
can be more radical than a large one. The
achievement in efficiency and power is
notable.  Experiences with CFD tools are
good. Together with experience and support
from the existing model, experiments give
reliable and good results.
Equipment such as the governor, control
system, and voltage control must be changed.
Recent technology and development enable a
new, effective, reliable approach in the field of
control and hydraulics. New systems have to
be more reliable, simple to operate, able to be
maintained infrequently and supervised
remotely.
Naslov avtorjev - Authors' Address
mag. Miha PIŠLJAR
Jože TROHA
Darko BENIGAR
Turboinštitut
Rovšnikova 7, SI - 1120 Ljubljana