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  1. Islander1

    Why there is a negative current flowing into solar panels

    I understand that shaded panels will have lower output voltages and that will create some current to flow towards a panel with lower voltage from the other panels with higher voltage. But in my case, the current fluctuation happens too fast and I cannot really justify it cloud coverage. Also it...
  2. Islander1

    Why there is a negative current flowing into solar panels

    Yes, it is a new installation. Was it constantly negative current or fluctuating between negative and positive?
  3. Islander1

    Why there is a negative current flowing into solar panels

    Hi, I have a big solar farm with multiple combiner boxes are connected to a big inverter. The inverter has a number of combiner boxes that are connected to the same DC (+) bus in the inverter. Each combiner box has 20 strings connected to it. Let's say I have 10 combiner boxes that are...
  4. Islander1

    Ground/Neutral Overcurrent Protection Settings

    Hi David, Yes, you are I'm using recent SEL 751 relay. I'm actually using typical phase and neutral current connection for a feeder application, please see the attached picture (it is the Figure 2.19 in SEL751A instruction manual). I've wired the residual connection back into IN terminals. Do...
  5. Islander1

    Ground/Neutral Overcurrent Protection Settings

    Thank you for your reply RRaghunath, In my system we have only phase CTs, so I should be using only 50/51N in that case. am I right? Do you have any suggestion regarding the 51N delay curve? Currently I set it to U4, (extremely inverse) with time delay of 5.0 seconds. Thanks,
  6. Islander1

    Ground/Neutral Overcurrent Protection Settings

    Hello All, I'm trying to provide ground/neutral overcurrent setting for a land based microgrid system (The microgrid is connected to utility via Delta/Wye-grounded transformer and I have a SEL 751 relay for my protection), but I don't have much experience in ground fault protection. Therefore I...
  7. Islander1

    AC Thruster Motor Short Circuit Current Contribution back to DC bus via VFD

    Hi folks, I have a hybrid marine power system, in which there is a 550kW thruster motor fed via VFD from 1000VDC bus. My question is that: can I neglect the short circuit current contribution from thruster motor back to DC bus through VFD or not in case of fault on DC bus? Any help will be...
  8. Islander1

    How to get pu reactance values from % reactance for synchronous generators

    Thanks Crshears and Xnuke for the answers. I was not sure whether that percentage is of actual value or of pu value. SO it is the percentage of pu value.
  9. Islander1

    How to get pu reactance values from % reactance for synchronous generators

    Hi All, I'm trying to model a synchronous generator in SKM PTW using synchronous generator datasheet. I need to put saturated reactances values in pu, however the datasheet provides me reactances in percentage values. Does anyone know how to convert % values into pu values? Here is my values in...

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