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  1. AntonioPerez

    Current asymmetry

    I've been asked for some grid quality requirements in a project. One of those parameters is current asymmetry. I'm trying to find any regulation or standard about it but I can't find. Does anyone know? Thanks in advance.
  2. AntonioPerez

    "Audio frequency" in electrical engineering

    Thanks for your comments. I think I discovered what it is. It seems to be some kind of system for data transmission by means of overlayed audio frequency signal to voltage wave from power grid to power plants. It is used, for example, to switch between day and night power-tariffs...
  3. AntonioPerez

    Converting TT to TNS earthing system to avoid untimely RCD tripping

    Thanks for your answers. che12345: I mean than just converting the TT to TN-S wouldn't solve the problem because RCDs will be still untimely tripping anyway. I had guessed that converting TT to TN-S was just a maneuver to be able to eliminate RCDs. Regulations let that circuit breakers be the...
  4. AntonioPerez

    Converting TT to TNS earthing system to avoid untimely RCD tripping

    Hi all, An industrial facility owner who suffers from frecuent untimely RCDs tripping in his facility was adviced to convert the existing TT earthing system into TNS. We've been asked to quote the engineering project for that. I've never seen this done before but I guess it is not quite...
  5. AntonioPerez

    Insufficient breaking capacity

    Thanks for your comments. Upstream breaker is new and has enough breaking capacity. Actually I was plannign to replace the downstream underrated breaker by a switch disconnector. My concern is that the downsream breaker could try to break the shortcircuit current and not be able, causing and arc...
  6. AntonioPerez

    Insufficient breaking capacity

    I'm working on a project of an existing facility. There is a main switchboard with a molded case circuit breaker in the incoming whose breaking capacity is insufficient for the calculated short-circuit current. That incoming circuit will be properly protected in its beginning, by a new circuit...
  7. AntonioPerez

    Measure multiple polyline length

    Is there any way of getting the sum of the lengths of multiple polylines selected in Draftsight? I used to do it in AutoCAD with a LISP macro. Thanks in advance.
  8. AntonioPerez

    HVAC in substation while main power supply loss

    Thanks EnergyProfessional. There is an alternative power supply in case of main power loss, but the consumption in this case is substantially reduced at about 7%. The alternative power supply has an autonomy of 8 hours, and often power losses are not expected. Equipment is designed to work at...
  9. AntonioPerez

    HVAC in substation while main power supply loss

    Hi, I was wondering if there is some standard that considers the situation of an HVAC system for a substation building during a main power supply loss. I'm participating in a project where ventilation was considered to be fed by a backup power supply but no air conditioning is posible while...
  10. AntonioPerez

    Distance between overhead power line and hazardous (ATEX) area

    I've been searching for any european standard that stablishes the required distance between overhead power line and hazardous (ATEX) area but I couldn`t find anything. In my case I have a 66 kV line over an outdoor propane/butane bottles storagement rack in Spain. I'd appreciate any help.
  11. AntonioPerez

    Short-circuit impedance tolerance

    Thanks. It is what I thought but I wanted to be sure. I guess this thread should be closed but I don't know how or even if I'm allowed to do that.
  12. AntonioPerez

    Short-circuit impedance tolerance

    IEC 60076-1 and other standards detail a concept of a tolerance in short-circuit impedance value. As I understand this tolerance must be taken into account during the process of manufacturing the transformer, as it is hard to define initialy the parameters to achieve the required impedance and...
  13. AntonioPerez

    Power transformer derating

    I would like to know if your understanding about this issue is the same as mine. I'm calculating the current for the incomming cable to the transformer and I need to know if I have to consider the nominal power or the derated power. Thanks.
  14. AntonioPerez

    Power transformer derating

    According to IEEE standard and others a derating factor must be applied to consider the effect of worse ambient and site conditions (altitude, ambient temperature) over an oil immersed power transfomer. As I understand, to assure the transformer won't suffer any damage, the transformer...
  15. AntonioPerez

    Protections included in VSD

    Hello, I'm designing an electrical facility to feed some motors (>75 kW) through VSD. We consider some ANSI proteccion functions in the switchgear (50, 51, 86) as if it was a feeder possition and we consider the specific motor protection functions in the engineered VSD. Some of the vendors in...
  16. AntonioPerez

    Copy to clipboard failed

    Thanks felix7502. I tried to run the program as Administrator but nothing changed. It doesn't seem to be related with writing rights. As for the Proxy Objects I searched in my file with Smart select but couldn't find any proxy object. Anyway I explode everything in the file three times, cleaned...
  17. AntonioPerez

    Copy to clipboard failed

    In some specific files I got the error "Copy to clipboard failed" when I try to copy any object, so I cant copy no object to another file. There should be some problema with those files. I cleaned them and audit them but it did't solve the problem. Any idea? Thanks.
  18. AntonioPerez

    Can't edit the snap point of a poligonal window

    In presentation mode I cant' edit the snap points of a poligonal window. When I try to click on a snap point the windows just get deselected so I can't find a way to edit the dimensions of the window. Any idea? Thanks
  19. AntonioPerez

    COM Surrogate error

    Sometimes when I open a file an when I close a file with draftsight I get the next error: "COM Surrogate stopped working". Draftsight works perfectly but it's a little anoying. Any idea?
  20. AntonioPerez

    How to insert an OLE object

    Yes, I know, but I've to do it manually every time. Thanks again.

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