Field Performance Evaluation of Hydro Power Stations

Performance Evaluation / Efficiency Test of over 240 hydropower plants of various capacities in different terrain and states have been carried out.

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Developed capability to carry out Field performance/efficiency testing as per IEC 60041:1991, IEC 62006:2010 and AHEC-IITR: Oct.2012.

Performance evaluation/ efficiency test of over 240 hydropower plants of various capacities in different terrain and states have been carried out.

Various methods applied for discharge measurement and head measurement.

Providing technical consultancy and efficiency testing of pump/turbine.

Scope of Testing

Visual Inspection

Functional Checks

Measurements and Tests

Visual Inspection

General inspection

Inspection of civil works (diversion, water conductor system, power house and tailrace).

Inspection of electrical equipment (control panels, power transformers etc.)

Inspection of mechanical equipment (turbine, governor system, cooling system)

Measurements and Tests

Unit Efficiency Test

Error Test on Measuring Instruments

Operational Tests on Protective Relays

Vibration Measurements

Sound Level Measurements

Load Rejection Test

Maximum Power Output Test

Functional Checks

Verification of the operation functioning of the component's subsystems and shortcomings defects, if any, are recorded.

Control Panels: Functional checks on external accessories (lamps, push buttons, switches, digital indicators, buzzers, hooters etc.) and internal accessories (panel lights, panel light switches, space heaters, thermostats etc.).

Fault / Status Annunciators: Component check, test, accept and reset functions.

Circuit Breakers: Trip and close functions.

Master / Trip / Auxiliary Relays: Operate and reset functions.

Control / Regulating Devices: Flow / head regulating devices, excitation voltage control, speed governor control, power factor control, manual start / stop operations, manual / auto synchronization, local / remote control of transformer tap changer, etc.

Methods of Unit Efficiency Measurement by Discharge Head Method

Absolute value of the discharge through the turbine.

Net water head available at the turbine, and

Electrical power output of the machine.

Uncertainty in the measurement by this method is ±2% to ±4% depends on type of instrument used.

Absolute Discharge

Current-meter method (Uncertainty ±2.5%)

PCM mounting frame could be installed at intake channel, tailrace channel, Intake duct for discharge measurement.

Point velocities of measurement section are recorded.

Discharge is calculated by velocity area integration method.

Acoustic Method for Discharge Measurement

Clamp-on Transit Time flow-meter (Uncertainty ±2.5% to ±3.5%)

Intrusive Type transit flow meter (Uncertainty ±1% to ±2%)

Ultrasonic sensors are clamped outside/ inserted (intrusive type) of the penstock.

Mounting of sensor depends on the diameter of penstock.

Acoustic Doppler Current Profiler (Uncertainty ±1.5% - ±3%)

ADCP transmit and receive Acoustic signals. Sound waves scattered back from particles within the water column.

The frequency shift of the echo is proportional to the water velocity along the acoustic path.

Measurement of Net Head

Measurement of net head requires measurement of total head at the inlet and that at the outlet, respectively, of the turbine and using their difference.

Head Measurement in Pressure Channels (Uncertainty ±0.5%)

Electronic pressure gauge is connected to the pressure manifold which is required to fabricate as per IEC 60041:1991 at intake of turbine.

Free Water-Surface-Level Measurement in Open Channels (Uncertainty ±0.5%)

Free water surface is measured separately near the intake point and the opening of the draft tube from ultrasonic level sensors (ULS).

Measurement of Electrical Power Output (Uncertainty ±1%)

A reference digital wattmeter with an accuracy class of 0.2 or better is connected in parallel with the panel wattmeter of the generator.

A test terminal block (TTB) or sliding-link type terminals, if provided in the metering panel, would facilitate connecting the reference wattmeter without shutting down the machine.

The electrical power output of the generator is calculated by multiplying the reference wattmeter reading with CT ratio and VT ratio.

Vibration Measurements (Uncertainty ±5%)

Vibrations measured at each bearing of the generating units on no-load condition.

Both rms displacement and rms velocity of the vibrations in the frequency band of the 1 Hz to 1 kHz are measured.

Measurement is done at four mutually perpendicular locations on the bearing, and both along axial and radial directions.

Sound Level Measurement (Uncertainty ±1.5 dB)

Sound level measured in "weighting factor A" mode near the machines at no-load conditions.

Readings are taken 1 m away from the surface of generator, turbine, flywheel and gear box (as applicable) at right angle to the machine shaft, both on upstream and downstream sides of the machine.

Load Rejection Test

The generating unit under test is initially loaded to its rated value and its speed is noted down.

The maximum sound level near the machine is also recorded on the basis of a sound level test.

The load on the machine is then suddenly rejected using the emergency shutdown push-button switch and the peak values of the speed and sound level (at the same point) attained consequently are noted.

The maximum rise in the speed is compared with run-away speed of the generator as specified by its manufacturer.

Maximum Power Output Test (Uncertainty ±1%)

Test conducted to check whether the maximum electrical power output actually available from the generating unit matches with the value specified by the manufacturer.

Test conducted at the rated head or at the head / discharge specified for maximum output of the generating unit.

Turbine Efficiency Measurement by Thermodynamic Method (Uncertainty ±1%)

In the case of SHP stations of high heads (100 m and above), the hydraulic efficiency of the turbine can be measured by thermodynamic method.

It involves accurate measurement of the small temperature rise of water that takes place between intake and outlet of the turbine due to losses from inlet to outlet. Pressure measurement is also conducted to determine the head, but discharge is not required being one of the major advantages of this method.

The overall efficiency of the generating unit is determined by assessing the hydraulic & mechanical losses in the turbine and in its auxiliaries and all losses including electrical and mechanical in the generator.

Thus, the method is suitable when the efficiency of the turbine alone is required and not the complete generating unit. Thermodynamic method has lesser uncertainty as compared to efficiency measured by any other discharge measurement method.

Instrument Used for Field Performance Evaluation of Hydro Power Plants

Performance evaluation / efficiency test of over 240 hydropower stations of different capacities in different terrain and states using different methods of discharge measurement and head measurement.

Time Line for Testing

Details about Hydro Power Stations from Owner

03-04 days

Data will be reviewed and suggested method

05-07 days

Pre test visit if required

01-02 days

Advise for Provision to be made at site for testing

15-20 days

Testing at Project

02-05 days

Report

10-15 days

Papers published in Research Journals

Arun Kumar, R.P.Saini, B.K.Gandhi, R.K.Srivastava, Pradeep Chandra and A.K. Dubey | Flow Measurement and Instrumentation | 69 (2019).

Experiences in Discharge Measurements at Small Hydropower Stations in India

Rahul K. Srivastava, Arun Kumar, B.K. Gandhi and R.P. Saini | IGHEM 2018 | 2018.

Experience with Ultrasonic Transit Time Flow Meter for Hydro Power Plant Efficiency Measurement

Arun Kumar, B.K. Gandhi and R.P. Saini | IGHEM 2018 | 2018.

Comparative Discharge Measurement in Small Hydro Power Plant using different Methods

Arun Kumar, B.K. Gandhi, and Pradeep Chandra | IGHEM 2016 | 2016.

Experience of Vibration and Noise Measurement of Small Hydro Power Plants

B.K. Gandhi, Arun Kumar and Rahul Kumar Srivastava | IGHEM 2016 | 2016.

Discharge Measurement Through Multiple Gates of Low Head Power Plants Under Unfavorable Conditions

B.K. Gandhi, Arun Kumar and H.K. Verma | IGHEM 2014 | 2014.

Discharge and Efficiency Measurement in Bassi Hydro Power Station in India

Shantaram S. Patil, H.K. Verma and Arun Kumar | IGHEM 2010 | 2010.

Efficiency Measurement of Hydro Machine by Thermodynamic Method

B.K. Gandhi, H.K. Verma and S.S. Patnaik | IGHEM 2008 | 2008.

Discharge Measurement in Small Hydropower Stations Using Acoustic Doppler Current Profiler

H.K. Verma and Arun Kumar | International Conference on Advances in Hydraulic Efficiency Measurements | 2004.

Instrument Networking for Efficiency Measurement in Small Hydro Power Stations