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  • Users: power2020
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  1. power2020

    Three winding transformer regulation

    If three winding transformer is loaded differently in two secondaries, the unregulated secondary winding voltages cannot be managed with OLTC. If, both PT and CT of both secondaries are connected to AVR, and AVR is programmed such that it should choose optimum tap position for both secondary...
  2. power2020

    Three winding transformer regulation

    Dear Folks, I am looking for an AVR, which can able to regulate the voltages at both secondaries of three winding transformer. OLTC is located on primary winding of the transformer If such AVR available, please suggest me. Advanced thanks.
  3. power2020

    Surge Arrestor Rating

    Dear Folks, Pl. clarify the different ratings of surge arrestor given in brackets (for 13800V system) as per IEEE C62.22-1997, table No.7 attached herewith. Advanced thanks...
  4. power2020

    Low Voltage ACB, Breaking current

    Thank you wbd for your response. Is there any co-relation between LV ACB 3-pole breaking current and 1-pole breaking current? or both are same?
  5. power2020

    Low Voltage ACB, Breaking current

    Dear Folks, Pl. clarify regarding breaking current selection of LV ACB, if L-G fault current is more than 3-ph bolted current , which current needs to be considered for LV ACB breaking capacity? I read somewhere that we need to consider 3-ph bolted fault current to select LV ACB breaking...
  6. power2020

    Power factor for VFD drives

    Thank you Skogsgurra for reply. It is useful info for me. If we provide APFC (Automatic power factor control) devices with CT and PT connections, which power factor it follows? And how can I get the information about VFD motor fault current contribution? Once again thanks...
  7. power2020

    Power factor for VFD drives

    Dear Folks, Two issues are confusing me in regard of VFDs. 1. What is the Power factor of PWM type VFD type with Line choke (source side)? As DC link capacitor is there, and motor always take reactive power from capacitor, I assume unity power will maintain at line side. Anyone pl. confirm. 2...
  8. power2020

    Harmonics -Softstarter

    Thanks Marke for information. In addition, could you pl. clarify that what is the fault current contribution of Softstarter drives and VFD if there is a fault on line side? Advanced Thanks...
  9. power2020

    Harmonics -Softstarter

    Dear Marke, So, Softstarter will act like a back-to-back doides during running and no harmonics will be generated if there is no energy saving algorithm. Thanks for your information. How energy saving algrorithm works for soft-starter without frequency control (v/f control)?
  10. power2020

    Harmonics -Softstarter

    Dear Folks, Pl. clear the doubt on softstarters. Does soft-starter for motor generate harmonics, if it operates at full output voltage (no voltage reducing condition)and without by-pass contactors? Advanced thanks..
  11. power2020

    Open Delta for 3-winding VT

    Hi Raghun, It is a three winding VT (star/star/delta). One secondary star winding for metering and protection (27) AND another secondary broken delta winding is connected to anti-ferroresonance resistor
  12. power2020

    Open Delta for 3-winding VT

    Thank you Slavag for Summarizing. In our system, only resistor is connected across the broken delta terminals for protection against ferro-resonance. Broken delta connection is not used for ground fault detection in system.
  13. power2020

    Cable de-rating factors

    Thank you cuky2000 for your reply, As of my knowledge, Protective device rating will depend on cable short-circuit capacity but not on ambient temp of the cable. But one of the leading cable manufacturer given different de-rating factors for using different protective devices for the same...
  14. power2020

    Cable de-rating factors

    Dear Folks, Please clarify the following: How power Cable "ambient temperature de-rating factor" will depend on different protection systems? In one of the cable catalogues it is given as follows: for Example: Ambient temp: 50 deg.C Semi enclosed fuse to BS 3036 : 0.91 (Derating factor) Fuse to...
  15. power2020

    Open Delta for 3-winding VT

    Hi prc, Application No.1 :Broken delta connection with resistor is for protection against ferro-resonance. Pl. go through from beginning of this post for more details. Application No.2: Broken delta connection with E/F protection relay is for detecting earth faults.
  16. power2020

    Open Delta for 3-winding VT

    Thanks for information. Sorry!In my previous post, I supposed to ask "the consequences if broken delta winding with resistor is NOT considered in PTs of Star winding of power transformer (Power transformer neutrals (Y/Y/Y/D) are solid grounded)" PT details: 13800:1.73/100:1.73/100:3V...
  17. power2020

    Open Delta for 3-winding VT

    Dear Davidbeach and Slavag, Thanks a lot for your information. Slavag is correct that resistor i.e.27 ohms,370W, is connected across the broken delta terminals and I understood the same. As the system is refurbishing, what will be the consequences if broken delta winding with resistor is...
  18. power2020

    Fault current on system

    Thanks a lot Marmite for supporting doc.
  19. power2020

    X/R ratio of Generator

    Thank you QBplanner, I will ask manufacturer, the reason for increasing trend of L-L and L-G fault over a period of time. W.r.t. typical attached curve, what is the reason for increasing fault current after approx.0.1 sec.
  20. power2020

    Open Delta for 3-winding VT

    Hi Slavag, Could you please specify any IEC/IEEE standard dealing this? B'cas we are refurbishing the system. In existing system, resistors are connected across open-delta terminals of VT. All Power transformer windings are solidly grounded. Thanks a lot

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