Test Procedure for AC Generators

BRIEF TEST PROCEDURE FOR AC GENERATORS ROUTINE TEST SL.NO TEST 1.1

1.2a.

1.2b. 1.3

1.4 1.5

1.6

1.7

1.8

1.9

PROCEDURE

REF.STANDA RD IEC 34/ IS 4722

Resistance measurement on main stator, exciter stator and exciter rotor. Insulation resistance test before and after HV test on main stator, main rotor, exciter stator and exciter rotor. Polarization Index Test. High voltage test on main stator.

Resistance of windings is measured by using Kelvin bridge/micro ohmmeter and resistance of accessories like RTD, BTD, ATD, and space heater by using digital multi meter. Ambient temperature is also recorded. a) Insulation res. of winding and space heater is IEC 34/ IS 4722 measured w.r.t to earth by using a meggar (500 V for LT, 1000 V for HT). b) Insulation resistance of stator winding using 1000 V meggar. The value recorded at the end of 1minute and 10 minute. PI value of the machine = 10 minute value / 1 minute value.

High voltage test on main rotor, exciter stator and rotor. Open circuit characteristic (shall be done during O.C. heat run test 2.2) Short circuit characteristic (shall be done during S.C. heat run test 2.3) Phase sequence test w.r.t the direction of rotation (shall be done during O.C. heat run test 2.2).

IEC 34/ IS 4722

Voltage balance test (shall be done during O.C. heat run test 2.2). Vibration measurement test (shall be done during O.C. heat run test 2.2).

Prepared by: R.Stanley Date: 24.03.2005

High voltage of 23 KV (i.e. Twice the rated voltage + 1 KV) is applied between each phase and ground, the other two phases are connected to ground. Test is conducted for 1 minute for each phase. High voltage of 1.5 KV (i.e. Twice the rated voltage + 1 KV) is applied to windings w.r.t. ground. Test is conducted for 1 minute. The generator is run at rated speed from prime mover in open circuit condition. Generator voltage, excitation current and voltage are recorded from 120% of rated voltage at equal intervals till residual voltage attained. The generator stator terminal is shorted and is run at rated speed from prime mover. The short circuit current reading at 25%, 50%, 75% and 100% are taken w.r.t excitation volts and current. The generator is run in specified direction at rated speed in open circuit condition. The phase sequence meter is connected to the generator PT terminal (U, V, W to connected to R, Y, B of the meter). The direction of meter is recorded.

All the 3 phase voltages are checked for balance in open circuit condition at rated Voltage and speed. Generator is run at rated voltage and speed. Vibration is measured at vertical, horizontal and axial directions on both DE and NDE bearings.

IEC 34/ IS 4722

IEC 34/ IS 4722

IEC 34/ IS 4722

IEC 34/ IS 4722

IEC 34/ IS 4722 IEC 34/ IS 12075

1.10

1.11 1.12

BRIEF TEST PROCEDURE FOR AC GENERATORS

Shaft voltage measurement (shall be done during O.C. heat run test 2.2). Impedance test of rotor

Momentary overload test (shall be done during S.C. heat run test 2.3).

TYPE TEST 2.1 Mechanical heat run test

2.2

Open circuit heat run test

2.3

Short circuit heat run test

2.4

Efficiency test by summation of losses method

Prepared by: R.Stanley Date: 24.03.2005

Voltage induced in between the shaft drive end and non-drive end by using digital multimeter.

IEC 34/ IS 4722

A 1 phase variable voltage is applied to the rotor field winding and current is measured. Readings are recorded at 25%, 50%, 75% and 100% of the rated field voltage. The generator is run at rated speed with its stator terminals shorted. Generator is excited to 150% of the rated current. The condition is passed for 30 seconds.

IEC 34/ IS 4722

The generator is run at rated speed. In this condition at equal intervals the power input to prime mover, generator RTD, BTD, ATD, ambient and body temperature are recorded till thermal equilibrium is reached. Then machine is stopped and hot resistance of all windings is measured. The generator is run at rated speed and voltage. In this condition at equal intervals the power input to prime mover, generator voltage, exciter voltage and current, generator RTD, BTD, ATD, ambient and body temperature are recorded till thermal equilibrium is reached. Then machine is stopped and hot resistance of all windings is measured.

IEC 34/ IS 4722/ IS 7132

The generator terminal is shorted and run at rated speed and rated current. In this condition at equal intervals the power input to prime mover, generator current, exciter voltage and current, generator RTD, BTD, ATD, ambient and body temperature are recorded till thermal stability is reached. Then machine is stopped and hot resistance of all windings is measured. From the above heat run test readings the temperature rise of the core and windings is calculated. The prime mover dc motor power input is measured at Gen. Running at rated speed at zero excitation. Gen. Running at rated speed and rated voltage in O.C. condition. Gen. Running at rated speed and rated current in short circuit condition. Prime mover running at rated speed in un coupled condition. From these readings efficiency is calculated by summation of

IEC 34/ IS 4722/ IS 7132

IEC 34/ IS 4722

IEC 34/ IS 4722/ IS 7132

IEC 34/ IS 4722

BRIEF TEST PROCEDURE FOR AC GENERATORS losses method.

2.5

Harmonic analysis (shall be done during O.C. heat run test 2.2) Noise level test (shall be done during O.C. heat run test).

2.6

2.7

Over speed test (shall be done during mechanical heat run test 2.1). Wave form measurement (shall be done during O.C. heat run test 2.2)

2.8

The generator is run at rated speed and voltage in open IEC 34/ IS 4722 th circuit condition, up to 50 harmonic is measured with power analyser. Then the THF is calculated. Machine is run at rated speed and voltage on no load and IEC 34/ IS 12065 noise is measured at different locations of the machine at 1 mt. Distance using noise level meter. Then the machine is stopped and background noise level is measured. From the both values the noise level of machine is calculated. The generator is run at 120% of rated speed for 2 minutes, no IEC 34/ IS 4722 abnormalities should be noticed during testing. Machine is run at rated speed and voltage. The sine wave of the 3 phase voltage is recorded by using C.R.O.

GENERAL CHECKS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Painting thickness. Air gap between exciter stator and rotor at different angles. Main and neutral terminal box dimension and suitability for the rated cable size. Auxiliary terminal box dimension, gland plate area suitable for required number of cables. Provision, mounting arrangement and polarity of the neutral side CTs. Foundation dimensions as per drawing. Shaft measurement check, key way dimension check. Slip ring and carbon brush check. Operational check of space heaters, local temperature gauges, water leakage detector etc. Carbon brush resistance.

Prepared by: R.Stanley Date: 24.03.2005

IEC 34/ IS 4722