Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Replies 21 replies
  • Subscribers 30 subscribers
  • Views 2092 views
  • Users 0 members are here
Options
You may also be interested in

Disconnection times on a system if a stand by generator is used

Anthony Smith

On a fully designed power distribution system, clearly the fault levels, earth loop impedances and ultimately fuse disconnection times are determined by the system parameters Transformer %Z etc one or two in parallel for min and max fault levels levels. What needs to be considered when bringing on a stand-by generator, clearly all Fault levels, Earth loop impedances and consequently fuse disconnection times would change because of the Generator parameters. How would you design in these new parameters, bearing in mind that disconnection times on a large system may no longer be achievable 

Parents
  • 0

    UPS - indeed any inverter supplied system - poses interesting challenges. The current that most electronic inverters can supply into a fault is extremely limited - perhaps only 2 or 3 times their nominal output. Obviously that's going to call into question using conventional overcurrent protective devices for fault disconnection. In some circumstances a fault of negligible impedance (or even an approximation to that) will cause the output voltage to collapse to such a low level that the dangers from shock are removed anyway. Maintaining a supply to fault-free circuits is challenging. If sufficient supply remains to operate RCDs you could have something like RCBOs (rather than 5A fuses) on each final circuit - or if that won't work, have multiple UPSs - so a single failure only affect a subset of all the lighting circuits.

       - Andy.

Reply
  • 0

    UPS - indeed any inverter supplied system - poses interesting challenges. The current that most electronic inverters can supply into a fault is extremely limited - perhaps only 2 or 3 times their nominal output. Obviously that's going to call into question using conventional overcurrent protective devices for fault disconnection. In some circumstances a fault of negligible impedance (or even an approximation to that) will cause the output voltage to collapse to such a low level that the dangers from shock are removed anyway. Maintaining a supply to fault-free circuits is challenging. If sufficient supply remains to operate RCDs you could have something like RCBOs (rather than 5A fuses) on each final circuit - or if that won't work, have multiple UPSs - so a single failure only affect a subset of all the lighting circuits.

       - Andy.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines