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Recent content by anggapra

  1. anggapra

    Debris on Transformer Base Tank

    [s]prc, "After closer observation, smaller-sized debris is also visible on the core." stevenal, the DETC hasn't been operated for years
  2. anggapra

    Debris on Transformer Base Tank

    Is it possible that this debris circulating inside the tank then leading to the fault at the tap changer?
  3. anggapra

    Debris on Transformer Base Tank

    Thank you for your response, Waross and PRC. I believe the debris resembles rust scale and sand, but I couldn't find any signs of rust or overheating on the tank, terminals, or windings. After bypassing the DETC, the TTR and WRM readings are good. However, there appears to be a deformation...
  4. anggapra

    Debris on Transformer Base Tank

    Hi, Recently, there was a failure in one of our transformers in the field. Based on the relay protection records, there was an LL fault in the transformer and confirmed after untaking the transformer that there was a fault between 2 phases in its Deenergized Tap changer. Debris was found...
  5. anggapra

    Zero Sequence Impedance of Autotransformer with Tertiary Winding

    Thanks prc, IEC 60076-8 is such a good read. Based on that table, I think X0 = 0.85 * X1 is a good estimation
  6. anggapra

    Zero Sequence Impedance of Autotransformer with Tertiary Winding

    Thanks David, Does the construction of an autotransformer winding affect its zero sequence impedance? The transformer above consists of 2 different cores, here is the drawing and photo below Meanwhile, we have another autotransformer with a drawing like this, unfortunately, there is no...
  7. anggapra

    Zero Sequence Impedance of Autotransformer with Tertiary Winding

    Hi, How to determine the zero sequence impedance of an autotransformer with a tertiary winding? The following are the specifications I received from the manufacturer, the positive sequence impedance is stated as 0.2%, but there is no data for zero sequence impedance, is there a rule of thumb...
  8. anggapra

    VSD Current and Voltage Input Measurement

    After the two previously mentioned trip events, there was another trip event due to IGBT over temperature. This VSD unit was installed only at the end of last year and has never been run for a long time. The problems varied. Initially, there was a high running ampere as previously described...
  9. anggapra

    VSD Current and Voltage Input Measurement

    I have checked, and confirmed that the VSD is using a 6-pulse rectifier The use of VSDs is actually relatively new in our field, and harmonics have never been a concern, so there are no company regulations regulating VSDs and the harmonics generated by loads, especially VSDs. What standards...
  10. anggapra

    VSD Current and Voltage Input Measurement

    Thank you all for your responses. Here is the event record of the recent IGBT Over Temp trip that was recorded by the VSD: The VSD was able to record some parameters with a sampling time of 5 minutes. Below is the trend prior to the IGBT over-temp trip. The trend for the events is quite...
  11. anggapra

    Negative Sequence Directional Overcurrent

    Thank you, David. Why does it need to be rated at 34.5 kV? Is it because of voltage shifting during LG fault? There were Wye-connected PTs at the WIDP01 bus, but they are only rated at 20 kV. However, during a fault at another location, the insulation failed at a voltage level of 34.5 kV. I...
  12. anggapra

    VSD Current and Voltage Input Measurement

    So initially, we conducted measurements because this VSD kept tripping with the indication of "IGBT high temp", the pattern was the same, the motor could run for approximately 24 hours or more, but it would trip with the indication of IGBT high temp. We have checked the VSD's cooling fan unit...
  13. anggapra

    VSD Current and Voltage Input Measurement

    Thank you all for your input. To give more context, here is the measurement diagram. DRANETZ is the power quality analyzer: In response to your questions: Yes, the distorted voltage is not when the VSD is truly off, but when the motor is set at zero speed. Please see below the voltage...
  14. anggapra

    Negative Sequence Directional Overcurrent

    Thank you all for your input. I forgot to mention that there are no Wye-connected PTs at the WIDP01 bus. Therefore, I think there is no way to measure the 3V0 without purchasing a new set of PTs. The only available PTs at the WIDP01 bus are open delta-connected PTs. I think we will purchase new...
  15. anggapra

    VSD Current and Voltage Input Measurement

    Hi, I tried to measure the current and voltage of an induction motor driven by a VSD. The measurement was taken at the input of the VSD, and the results are as follows: Voltage: Current: The waveforms are heavily distorted, especially the current waveform. Is this normal? Could it be...
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