55838398 Power Transformer

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Transcript of 55838398 Power Transformer

  • POWER TRANSFORMER

    1 Insulation Resistance MeasurementProcedurea. For LT systems, use only 500V or 1000V Megger.b. For MV & HV systems, use 2500V or 5000V Megger.c. Remove Earth from Transformer neutral.d. Measure as per table below.

    Circuit Megger UsedMV & HV

    1U - E 5kV2U - E 5kV1U - 2U 5kV

    2 Winding Resistance Measurement

    Circuit Tap No Resistance

    1U-1N All Taps1V-1N1W-1N

    2U-2N2V-2N2W-2N

    1U

    1V

    1W

    1N

    2U

    2V

    2W

    2N

    1U 1V 1W 1N

    2U 2V 2W 2N

    WINDING RESISTANCE METERI I I I

    I1 P1 P2 I2

  • 3 Magnetic Current Test

    Applied Voltage Measured Current1U-1V 1U1V-1W 1V1W-1U 1W1U-1N, 1V-1N,1W-1N 1N

    4 Magnetic Balance Test

    Applied Voltage Measured Voltage1U1N 1V1N 1W1N 1U1N 1V1N 1W1N 2U2N 2V2N 2W2N

    415 - - - - 415 - - - - 415 -

    Applied Voltage Measured Voltage1U1V 1V1W 1W1U 1U1V 1V1W 1W1U 2U2V 2V2W 2W2U

    415 - - - - 415 - - - - 415 -

    1U

    1V

    1W

    1N

    2U

    2V

    2W

    2NmA

    415 V AC

    mA

    mA

    mA

    1U

    1V

    1W

    1N

    2U

    2V

    2W

    2N

    415 V AC Measured voltage

  • 5 Vector Group Confirmation.

    Dyn1

    Conditions:1 -1U and 2u should be shorted.2 -Apply 415V to 1U,1V&1W3 -Satisfy the following conditions.

    1U1W = 1U2n + 1W2n1W2w = 1W2V1V2v < 1V2w

    Dyn11

    3 -Satisfy the following conditions.1U1V = 1U2n + 1V2n1V2w = 1V2v1W2w < 1W2v

    1U

    1V1W

    2W

    2U

    2V

    1U 2U

    1V1W

    2V

    2W 2n

    1U

    1V1W

    2W

    2U

    2V

    2U1U

    1V1W

    2W

    2V

    2n

  • 5 Vector Group Confirmation.

    Ynd1

    3 -Satisfy the following conditions.1U1N = 1U2v + 2v1N1W2v = 1V2v1V2v < 1V2w

    YNyn0

    3 -Satisfy the following conditions.1W2w = 1V2v1W2n = 1V2n1U1N = 1U2n + 1N2n

    6 Short Circuit Test and Differential Stability.7 REF Stability Test8 Cooler Circuits

    1U

    1V1W

    2W

    2V

    2U

    1N

    1U

    1V1W

    2W

    2V

    2U

    1U

    1V1W

    2W 2V

    2U

    1N2n

    1U

    1V1W

    2W 2V

    2U

    2n

    1N

  • 9 Temperature Indicators Calibration10 Auxilliary Protection Circuits

  • Measured voltage

  • 6 Short Circuit Test and Differential Stability.

    Stable Condition.

    Diff RelayP1 S1

    300/1 AS2 S1

    S2 S1

    P2 S2

    B-Ph

    Y-Ph

    R-Ph

    P1 S1

    500/1 AS1 S2

    S1 S2

    S2

    P2

    Apply 3-Ph AC Voltage

    N R Y B

    Temporary Short

    Id

    Id

    Id

  • Example:Short Circuit Current Calculation.

    Rating : 100MVAHV LV

    Voltage 220 kV 132kVCurrent 262.43 A 437.40 A% of Impedance (%Z) = 8.05%

    HV MVA = LV MVA = 100MVA

    3 x 220000 x I1 = 3 x 123000 x I2 = 100,000,0003 x 220000 x I1 = 100,000,000I1 = 100,000,000 / (3 x 220000)I1 = 262.43A

    3 x 123000 x I2 = 100,000,000I2 = 100,000,000 / (3 x 132000)I2 = 437.40A

    %Zv = 8.05% = 220kV x % of impedance = 220000 x (8.05/100)

    %Zv = 17,710 V

    If We may apply 415 V to HV sideHV I primary = (415 x 262.43) / 17710HV I primary = 6.15 AHV sec = 6.15 / 300HV sec = 0.0205A

    LV I primary = (415 x 437.4) / 17710LV I primary = 10.25 ALV sec = 10.25 / 500LV sec = 0.0205 A

  • Unstable Condition

    S1

    S2 S1

    S2 S1

    S2

    S1

    S1 S2

    S1 S2

    S2

    Id

    Apply 3-Ph AC Voltage

    Temporary Short

    Id

    Id

  • 7 REF Stability Test

    i) Stable Condition.

    R Y B

    P1 S1 S1 S1

    P2 S2 S2 S2

    S2 S1 N

    P2 P1P2 P1

    nS2 S1

    P1 S1 S1 S1

    P2 S2 S2 S2

    r y b

    Apply 3-Ph AC

    Fault

    HV REF

    LV REF

    SHORT

  • ii) Unstable Condition (Type 1)

    S1 S1 S1

    S2 S2 S2

    S2 S1

    S2 S1

    S1 S1 S1

    S2 S2 S2

    Apply 3-Ph AC

    SHORT

    LV REF

    HV REF

  • iii) Unstable Condition (Type 2)

    S1 S1 S1

    S2 S2 S2

    S2 S1

    S2 S1

    S1 S1 S1

    S2 S2 S2

    HV REF

    LV REF

    LOADING TRANSFORMER

    LOADING TRANSFORMER

  • TRF testingShort circuitREF