routine type tests

WELCOME

To

ELECTRICAL MACHINES

TESTING DEPARTMENT

TESTING OF TURBOGENERATORS

ROUTINE TESTS

AND

TYPE TESTS

ROUTINE TESTSDynamic TestsMechanical run testShort circuit characteristic and losses

measurementOpen circuit characteristic and losses

measurementPhase sequence checkShaft voltage measurementImpedance measurement at standstill, at 1/3,

2/3 and 3/3 of rated speeds.

ROUTINE TESTS

Static TestsInsulation Resistance measurement on

stator and Rotor winding; PI value measurement

High voltage Test on stator and rotor winding

RTDs ChecksDC Resistance measurement on stator and

rotor winding

TYPE TESTSDynamic TestsMechanical Heat run test.Short circuit heat run test.Open circuit heat run test.Wave form Analysis and THF measurementLine to line sustained short circuit test.Line to line and to neutral sustained short circuit test.Residual voltage measurement.GD2 measurement.3-phase sudden short circuit test.

Mechanical Run test(Scheme)

TURBOGENERATORDC DRIVE

MOTOR

OUTLET BOXESRV41/RV42

Ward-Leonard set in 86 Bldg

Or Thyristor convertors in

86 A Bldg

Mechanical Run test (Scheme)


MOTOR

RTD,TC measurement in HP 3852S DAS




86 A Bldg

Mechanical Run test (Scheme)


MOTOR


Vibration measurement in Bently 3300 Vibration

monitor




86 A Bldg

Mechanical Run test (Scheme)TURBOGENERATOR

DC DRIVE MOTOR


Vibration measurement in Bently 3300 Vibration

monitor

TDxnet

LAN HUB

Data Manager 2000Vibration monitoring &

Vibration plots in computer




86 A Bldg

Mechanical Run testBefore running the machine ensure

correctness of all the electrical connections Lube oil is flowing through bearings and gearbox All the instruments are working.

Roll the machine and check all the parameters.

Slowly raise the speed to 1/6 th rpm.

Give command for collecting samples if Data Manager is not collecting samples.

Observe slowroll vibrations,temperatures and oil flows.

Mechanical Run testRaise the speed to 1/3rd rpm slowly and record

vibrations,temperatures and oil flows.Let the machine warm up for bearing oil temperature to

around 40C.Now raise the speed to 2/3 rpm by observing all the

parameters and record all the parameters.Raise the speed to 3/3 rpm by observing all the

parameters,critical speed and record all the parameters.Roll the machine for stabilisation of bearing temperature

and record mechanical losses.

Mechanical Run test There are different conditions of the machine

Steady state condition Transient operating condition Slow roll condition Machine stopped condition

Vibration measurement : Overall vibrations Position Frequency nX amplitude and Phase Shape or form of the vibration

Mechanical Run test Vibration is The oscillatory (back and forth) motion of a physical object. The vibrations are measured in Velocity and in displacement Displacement - The change in distance or position of an object relative to a

reference. Machinery vibration displacement is typically a peak to peak measurement of the observed vibrational motion or position, and is usually expressed in units of mils or micrometres. Proximity probes measure displacement directly. Signal integration is required to convert a velocity signal to displacement, but does not provide the initial displacement (distance from a reference) measurement.

Velocity - The time rate of change of displacement. millimetres/second, zero to peak. Velocity measurements are used to evaluate machine housing and other structural response characteristics. Electronic integration of a velocity signal yields displacement, but not position.

Mechanical Run test(Vibration plots) Timebase - A presentation of the instantaneous amplitude of a signal as a

function of time. A vibration waveform can be observed on an oscilloscope in the time domain.

Orbit - The path of the shaft centerline motion during precession . The orbit can be observed with an oscilloscope connected to XY vibration-measuring transducers.

Amplitude Phase Vs Time - the trend plot of filtered vibration amplitude and phase lag angle data.

Shaft centreline trend - Transient or trend plot of the shaft average radial

centerline position within the bearing clearance. Spectrum - Commonly a presentation of the amplitudes of a signal's frequency

components versus their frequencies. Or the frequency content of a signal. Waterfall ( Spectrum plots at different time) Bode Plot - A pair of graphs in Cartesian format displaying the 1X vibration

vector (phase lag angle and amplitude) as a function of shaft rotative speed. Polar plot - Polar format presentation of the locus of the shaft 1X (or 2X,...)

filtered vibration vector from a single channel as a function of shaft rotative speed.

Cascade (Spectrum Plots at different speeds)

Short circuit characteristic (Scheme)

TURBOGENERATORDC DRIVE MOTOR

RTD,TC measurement in

HP 3852S DAS

Vibration measurement in Bently 3300 Vibration monitor

TDxnet

LAN HUB

Data Manager 2000Vibration monitoring & Vibration

plots in computer


Ward-Leonard set in 86 BldgOr Thyristor convertors in

86 A Bldg

NORMA 6200

OUTLET BOX

Thyristor Convertor C

In 86 Bldg

Generator Field

Shunt

If

Ia Ib

CTS

shunt

Id

Vd

Outlet box Outlet box

Short circuit characteristic (Scheme)


MOTOR

NORMA 6200

OUTLET BOX

Shunt

If

Ia Ib

CTS

shunt

Id

Vd

HP DAS

Computer

IEEE 488interface

Short circuit characteristic The machine is prepared for short circuit characteristic using current

transformers and shorting links

The machine is run at rated speed and drive motor input voltage and current are noted and m/c is excited gradually in steps, at 20%, 40%, 60%, 80%, 90% and 100% In (In: rated current of machine).

At each step the following parameters are noted:

a) Stator current (Ia & Ib).

b) Rotor current (If) corresponding to stator current.

c) Drive motor voltage(Vd) and current(Id) corresponding to stator current.

e) Bearing vibrations at rated stator current (100%In).

d) RTDs readings at rated stator current (100%In).

Short circuit characteristic(Log Format)

Ia Ib %In If Vd Id DMInputkW

Short circuit characteristic The excitation is reduced and cut off. The speed is reduced and the machine

is cooled at lower speed. The temperatures are checked from m/c RTDs. The machine is stopped when it is sufficiently cooled down. (The stator winding temperatures to be less than 60 0 C).

From the above data, the characteristic curves are plotted as follows:

a) %In v/s If.

b) %In v/s m/c looses in kW.

Short circuit characteristic(Graph)

Field current in Amps.

SCC

%In

100%

Ifk

Copper losses(Graph)

%In,%En

Los

ses

in

kW

Pcu1

Pmech

Drive motor losses

1

3

4

1.Copper Losses2.3.Mechanical losses4.Drive Motor losses

Open Circuit characteristic (Scheme)


MOTOR

NORMA 6200

Generator Field

Slip rings

Shunt

If

A B C

PTS

shunt

Id

Vd

Open circuit characteristic The machine is prepared for open circuit characteristic

The machine is run at rated speed and drive motor in put voltage and current are noted and m/c is excited gradually in steps, at 20%, 40%, 60%, 80%, 90%, 95%, 100%, 105%, 110% and 120%En (En: rated voltage of m/c).

At each step the following parameters are noted:

a) Stator Voltages (Vab, Vbc & Vca).

b) Rotor current (If) corresponding to stator voltage.

c) Drive motor voltage (Vd) and current (Id) corresponding to stator voltage.

Open characteristic(Log Format)

Vab Vbc Vca %In If Vd Id DMInputkW

Open circuit characteristic(Graph)


120

100

80

%En/%In

OCCAir Gap line

IfoAGLIfo

OCC & SCC (Graph)


120

100

80

%En/%In

OCCAir Gap line

IfoAGLIfo Ifk

Losses(Graph)

%In,%En

Los

ses

in k

W

Pcu1

Pfe

Pmech

Drive motor losses

1

2

3

4

1.Copper losses2.Iron losses3.Mechanical losses4.Drive Motor losses

Phase sequence check (Scheme)


MOTOR

Phase sequence Phase sequence indicatorindicator

Shaft voltage measurement (Scheme)


MOTOR

MultimeterMultimeter

Impedance measurementEquipment:

50 Hz (Power frequency) A.C source. AC/DC Power analyser. Current transformer (25/5 A or 50A/5A or 100A/5A). Connecting leads.

A variable 50 Hz A.C. voltage of single phase is applied across the slip rings / input leads and readings of voltage and current are noted down from ~ 50V to ~ 200 volts in steps of ~ 50 V.

This test is done at standstill and at 1/3rd,2/3rd and at 3/3 of rated rpm

Impedance measurementEvaluation of Impedance:Evaluation of Impedance is done by using formula :

Z = V/I .

where, Z : Impedance in ohms. V : Voltage in Volts.

I : Current in Amps.

The Impedance of rotor at

standstill and at rated speed is plotted as applied

voltage v/s Impedance.


MOTOR

VariableAC 50 Hz

source

NormaD6200

Power Analyser

CT

V

I

Impedance measurement1. At rated rpm (Rotor inside stator)

2. At Standstill (rotor inside stator)

3. At standstill (Rotor outside stator)

1

2

3

0

10

20

30

0 50 100 150 200 250

50 Hz AC voltage in Volts

Measurement of insulation resistances of stator and rotor windings before and after

high voltage test (m/c at rest): Equipment:

a) Megger (1000V/2500V).

b) Earthing Rod & earthing wire/cable.

Insulation resistance of the stator and rotor windings are measured separately before and after high voltage test using Megger of 2500 V for stator & 1000V for rotor windings.

Measurement of insulation resistances of stator and rotor windings before and after

high voltage test (m/c at rest):

IR values are measured at 15 sec. and at 60 sec. Absorption coefficient of insulation is found out as,

Absorption coefficient = IR at 60”/ IR at 15”

If insulation resistance values are quite high, the absorption co-efficient is not considered because of early saturation (often observed in low voltage windings like rotor etc.).

Measurement of insulation resistances of stator and rotor windings before and after high voltage test (m/c at rest):

Minimum I.R. value :

The minimum value of insulation resistance (Rm) at 60” is

recommended as:

Rm = (kV+1 ) M.

(where kV is voltage in kilovolts to be applied for test.)

In practice a fairly high value is obtained.

The winding is discharged to earth after each measurement.

High voltage test on stator and rotor winding (m/c at rest):Equipment:

a) 50 Hz A.C. High Voltage transformer and it’s Induction regulator/input autotransformer.

b) Potential transformer (35 or 100 kV/100V).

c) Volt meter.

d) Binding Wire.

e) Earthing Rod & earthing wire/cable.

The m/c is prepared for High voltage test

High voltage test on stator and rotor winding (m/c at rest):

When H.V. test is done on one phase winding, all other phase windings, rotor winding, instrumentation cables and stator body are earthed.

The high voltage is applied to winding by increasing gradually to required value and maintained for one min. and reduced gradually to minimum.

The transformer is switched off and winding is discharged to earth by shorting the terminal to earth using earthing rod connected to earthed wire/cable.

The test is conducted on all the phases and rotor winding separately.

High voltage test on stator and rotor winding (m/c at rest):

High voltage test levels : Stator winding : (2 Ut + 1) kV = 23 kV for 11kV m/cs.Rotor winding : (10 times Up) volts.

(with minimum of 1500V and maximum of 3500V.)

where, Ut : Rated voltage of the machine under test.

Up : Excitation voltage.

High voltage test on stator and rotor winding (m/c at rest): Scheme

* :H.V.T : High voltage transformer.

SPR : Series protective resistance.

P.R : Potential transformer.

C.T : Current transformer.

A : Ammeter.

V : Voltmeter.

Variable A.C.50 Hz

Supply fromAuto

transformer/Induction

regulator asInput to HVT A

SPR

H.V To Stator

winding & Earth to Frame

V

High voltage test on stator winding (m/c at rest): Scheme

* Arrangement of phases for High voltage test.

A B C A B C A B C

PI Value measurement (m/c at rest):Measurement of polarization index of stator winding:The polarization index of stator winding, all the three phases

together, is measured using 2500 V Megger after high voltage test. The insulation resistances are noted at 1’ and at 10’ from starting of measurement.

The polarization Index is evaluated as follows:Polarization Index (P.I.) = I.R. value at 10’ / I.R. value at 1’

The minimum allowable PI value is 2.0.

Measurement of D.C resistance of Stator and Rotor windings in cold condition:

Equipment :

a) Digital Micro ohmmeter & it’s measuring leads.

b) Thermometer (Hg in glass). DC resistances of stator and rotor windings are measured separately using

micro ohmmeter. The instrument terminals are connected to the m/c terminals and proper range in meter is selected. The stabilized reading is recorded.

Ambient temperature from Hg in glass thermometer is recorded. The stator RTDs values are noted and average value of stator winding temperature is evaluated.

Measurement of D.C resistance of Stator and Rotor windings in cold condition:

Evaluation of resistance values at 20 C:Evaluation of resistances at 20 °C (R20) is done by using formula:

R20 = Rt. (235+20) / (235+t) m.

where, R20 : Resistance at 20 C in m.

t : Average temperature of the stator winding in C.

Rt : Measured resistance of winding in m.Variation in maximum and minimum values of d.c. resistance of 3

phases of stator windings up to 5% is acceptable.

RTD ChecksMeasurement of d.c. resistances and insulation

resistance of RTDs:

The d.c. resistances and insulation resistances of RTDs are measured using multimeter and Megger respectively and recorded.

Evaluation of Efficiency: After completion of routine tests, efficiency of the

machine is evaluated. The following sequence of calculation is followed.Short circuit characteristic is plotted from S.C.C.

results by selecting X- axis as field current and Y-axis as % of rated current. Values of field current (Ifk) at 100%In is obtained from the curve.

Short circuit characteristic(Graph)


SCC

%In

100%

Ifk

Evaluation of Efficiency: Open circuit characteristic is plotted on a graph paper

from O.C.C results by selecting X- axis as field current and Y- axis as % of rated voltage. Values of field currents at 80%, 100%, 115% & 130%En are obtained from the curve.

Air gap line for OCC is drawn and field current for air gap line at 100 % En is obtained

OCC & SCC (Graph)


120

100

80

%En/%In

OCCAir Gap line

IfoAGLIfo Ifk

Evaluation of Efficiency TG losses: Copper loss characteristic is plotted from S.C.C results by

selecting X- axis as % of rated current and Y-axis as losses in kW. The value of copper loss(kWcu1) at 100%In is taken from the curve.

Iron loss characteristic is plotted from O.C.C results by selecting X- axis as % of rated voltage and Y-axis as losses in kW. The value of iron loss (kWfe) at 100%En is taken from the curve.

Losses(Graph)

%In,%En

Los

ses

in k

W

Pcu1

Pfe

Pmech

Drive motor losses

1

2

3

4

1.Copper losses2.Iron losses3.Mechanical losses4.Drive Motor losses

Evaluation of Efficiency Drive motor with gear box losses:

From calibration curves of drive motor used during testing following data is taken. Drive motor iron losses at voltage Vd = kw1 Drive motor copper losses at current Id = kw2 Drive motor loss kw3 = (kW1+kw2) Drive motor iron losses at 100%In = kw4 Drive motor copper losses at 100%In = kw5 Drive motor loss at 100% In (kW6) = kw4+kw5 Drive motor iron losses at 100%En = kw7 Drive motor copper losses at 100%En = kw8 Drive motor loss at 100% En (kW9) = kw7+Kw8

Evaluation of Efficiency Mechanical losses of the T.G + Drive unit:

Average mechanical losses (kWmech.) = average of Mech. losses before

SCC and OCC

Losses at 100 % In i.e.kW100%In mech.

= kW av mech + (kW6 - kW3)

Losses at 100 % En i.e. kW100%En mech.

= kW av mech + (kW9 - kW3)

Evaluation of Efficiency Machine losses:

i) Mechanical losses (Pmech) = kW av mech - kW3

ii) Stator copper losses at 100 % In (Pcu1)

= kWcu1 - kW100%In mech

iii) Stator iron losses at 100%En (Pfe)

= kWfe-kW100%Enmech iv) Rotor copper losses (Pcu2) = Ifn2 . R75

where

Ifn : Excitation at full load.

R75 : Rotor winding resistance at 75 C.

Evaluation of Efficiency

iv) Excitation losses : This shall be taken as 5% of rotor copper losses. Or static excitation losses ( Data furnished by Static excitation manufacturer)

v) Brush drop losses: In case of m/c with conventional excitation system with slip rings on rotor, the brush drop losses are calculated taking voltage drop of 1.0 volt each polarity multiplied by the rated excitation current.

Evaluation of Efficiency iv) After obtaining the machine losses i.e. mechanical losses including exciter

mechanical losses (if any), stator copper losses, stator iron losses, rotor copper losses, excitation losses, brush drop losses (if any); all the losses are added to get total loss. Percent Efficiency (%) is evaluated as follows:

% = {OUT PUT / (OUT PUT + Total Loss)} . 100

Evaluation of EfficiencyLOAD% 100 75 50 25

Stator current In A 394.00 295.50 197.00 98.50

Active Power Ps kW 6000.00 4500.00 3000.00 1500.00

Rotor current Ifn A 421.30 352.10 286.20 225.30

Mechanical Losses * Pmech kW 31.78 31.78 31.78 31.78

Iron Losses Pfe kW 46.10 46.10 46.10 46.10

Stator copper losses Pcu1 kW 44.30 23.71 10.11 2.52

Rotor copper losses $ PCu2 kW 33.22 23.20 15.33 9.50

Excitation losses # Pe kW 1.66 1.16 0.77 0.48

Total losses Pt kW 157.06 125.95 104.09 90.37

Input Ps+Pt kW 6157.06 4625.95 3104.09 1590.37

Efficiency % 97.45 97.28 96.65 94.32

Evaluation of short circuit ratio (S.C.R)

Evaluation of short circuit ratio (S.C.R):

From the test data S.C.R. is calculated using formula:

S.C.R = Field current at 100%En from OCC / Field current at 100%In from SCC

Thank YouThank You

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