56 | Pumps Valves and Systems | July-Aug 2011

Abstract

Hydro-turbines are rotary machines which convert the

mechanical energy o the rotating element into electrical

energy. Te mechanical energy is imparted to the rotating

element by a high speed jet o water stored at a height in a

reservoir which is brought through a pipe; known as a pen-

stock, to the machine. Te rotating element o the machine

is connected through a shat to the generator, which in turn

 produces electricity. More the fow through the machine,

more the power generated. A turbine is designed or a spe-

cic output at the rated net head and fow. A turbine must

meet these guarantee conditions in order to deliver the

rated output. Tis paper deals in discussing the actual eld

 perormance data o a Francis turbine o 10 MW capacity 

tested using thermodynamic method.

Introduction

Te test was conducted on the turbine using thermo-

dynamic method adhering to the code IEC - 60041. Te

test was conducted to guarantee the perormance o the

machine at the then prevailing operating condition. A tur-

bine is controlled automatically or variation in demand

by governor. Governor is a device which controls the

needle valve or guide vane opening to vary the fow rate

through the turbine. A variation in fow rate changes the

 power output o the turbine. For example, when the load

on the turbine is reduced due to reduced consumption

on the distribution side, the turbine starts to rotate at a

higher speed, which in turn orces the governor to partial-

ly reduce the fow to match the speed to the rated speed.

Tis reduces the power output rom the machine to match

the demand. Te machine tested was manually control-

led in order to generate the turbine perormance curve.

Te controlling was achieved by changing the Guide Vane

opening positions, which changed the load. Due to site

constraints, the turbine could not be operated at ull load

and hence maximum guide vane opening position o 88%

 was used to certiy the guarantee condition.

Guarantee Condition

Te guarantee condition o the turbine is as shown in the

table A. Since, the turbine could only be operated at 88%

Hydro Turbines PerformanceMonitoring - A Case StudyBy Juned Ansari, Secure Meters Limited

Guide vane opening, the guarantee point or the said condi-

tion have been deduced rom the hill chart o the turbine.

able : A

Test Setup

High Pressure Side (Penstock)

wo pressure transducers and two temperature probes were

used on the penstock or HP side energy measurement.

Low Pressure Side (ail Race)

On the tail race side, a 2 x 3 rame was used with 6 tem-

 perature probes and one submersible pressure transducer.

Outliers were rejected and only those temperature read-

ings were accepted which were ound consistent in mutual

agreement with the client.

Te arrangement is as shown under:

Power Measurement

Power measurement was done using two wattmeter meth-

od on the generator side. Te generator was producing

 power at 11KV and 1000 RPM.

   G  u   i   d  e   V  a  n  e

   O  p  e  n   i  n  g   (   %   )

   D  e  s   i  g  n  e   d

   N  e   t   H  e  a   d   (  m   )

   R  u  n  n  e  r   O  u   t  p  u   t

   A   t   T  u  r   b   i  n  e

   S   h  a      t   (   k   W   )

   T  u  r   b   i  n  e

   E      f  c   i  e  n  c  y   (   %   )

   D   i  s  c   h  a  r  g  e

   (  m   3   /  s   )

100% - Full Load 326.43 10,304.00 92.30 3.49

88.0% 324.84 8,800.82 91.79 3.01

Rated Speed o urbine (RPM) 1000

Temperature Probes

Submersible Transducer

View towards Turbine Side View

Y

 

58 | Pumps Valves and Systems | July-Aug 2011

Please see the ollowing chart generated rom site testing.

Manuacturer provided generator efciency curve was used to evaluate the generator efciency in order to calculate the

turbine shat output.

Results

Te table 1 below shows the results obtained rom the turbine test using thermodynamic method. Te calculated data

 was corrected to the net head; 324.84m, corresponding to the 88% guide vane opening. Simultaneously, the ow was also

measured using an ultrasonic ow meter. Te results o which are shown in able 2.

NetHead(m)

TurbineEfciency

(%)

GeneratorPower (kW)

GeneratorEfciency

(%)

TurbineShatPower(kW)

TurbineDischarge

(m3 /s)

GVOpening

(%)

Corrected to 324.84m

Turbine ShatPower (kW)

TurbineDischarge

(m3 /s)

329.14 87.60 7284.73 97.43 7476.88 2.643 72.20 7625.78 2.660

328.53 88.21 7498.37 97.47 7693.03 2.705 77.30 7824.36 2.720

327.73 88.94 7773.54 97.52 7971.55 2.787 79.90 8077.99 2.799

326.19 90.66 8251.55 97.58 8455.82 2.914 84.00 8508.52 2.920

324.84 91.43 8653.55 97.63 8863.65 3.041 88.00 8863.59 3.041

able 2 USFM Flow data

Te uncertainty in ow measurement (thermodynamic) is

between 1.15 to 1.16% only, which is quite acceptable. Ef-

ciency evaluation using conventional method has a ten-

dency to make an efcient unit appear inefcient and vice

 versa.

Te uncertainty in efciency evaluation was ound to be

only 0.45% at 88% guide vane opening condition. Tis is

acceptable. Te turbine satises the guarantee condition.

650075

77

79

81

83

85

87

89

91

93

95

2.05

2.3

2.55

2.8

3.05

3.3

3.55

3.8 DUTY POINT

Turbine No: 1 Tester: AW/MAY/SP Test date: 01-Feb-2011AEMS TEST DATA

7100 7700 8300 8900

TURBINE SHAFT OUTPUT - kW

   T   U   R   B   I   N   E   E   F   F   I   C   I   E   N   C   Y  -   %

   D   I   S   C   H   A   R   G   E  -  m

         3   /  s

9500 10100 10700 11300

Hydro Power Station At Net Head of 326.43m

able 1 est Results rom Termodynamic est

   S  r .   N  o

   T   h  e  r  m  o   d  y  n  a  m   i  c

   F   l  o  w  m

   3   /  s

   U   S   F   M

    F   l  o  w

  m   3   /  s

   U  n  c  e  r   t  a   i  n   t  y   i  n   F   l  o  w

   T   h  e  r  m  o   d  y  n  a  m   i  c

  m  e   t   h  o   d   %

   U  n  c  e  r   t  a   i  n   t  y   i  n

   E      f  c   i  e  n  c  y   %

P1 2.643 2.320 1.1587 0.4685

P2 2.705 2.390 1.1572 0.4654

P3 2.787 2.460 1.1559 0.4621

P4 2.914 2.600 1.1532 0.4551

P5 3.041 2.730 1.1516 0.4511

 

July-Aug 2011 | Pumps Valves and Systems | 59

Conclusion

1. he turbine satisies the guarantee condition at 88%

Guide Vane Opening. he turbine is operating at

91.43% eiciency generating 8863 kW.

2. he turbine was ound to be producing slightly more

 power (63kW) under present condition than expected

rom the guarantee condition.

3. It is important to keep a watch on the turbine

 perormance as silt/scale deposition on the turbine

blades drastically aects the operational efciency.

Tis also unnecessarily aects the lie o bearings,

seals, rotor etc besides requiring more water to

 produce same amount o electricity.

4. It is recommended to get the hydro turbines

tested. hey are a green source o energy. esting

reveals any extra generation potential lying with

the turbine by suitable modiication in operating

schedule.

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