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
  • Locked Locked
  • Replies 13 replies
  • Subscribers 26 subscribers
  • Views 1639 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

AFDDs - are they sensitive to upstream arcing?

AJJewsbury
It's occurred to me that if AFDDs work by spotting distortion in the a.c. current waveform that's passing through the device, then they're likely to see the same effect if series arcing is occurring upstream (with a decent sized load downstream).


If that's the case a decent DNO's crackle could trip out a significant number of final circuits if they happened to be loaded at the time.


Or are AFDDs cleverer than that? (e.g. do they look for an undistorted incoming voltage as well as a distorted current?)


As many of the dimming and flickering I've seen has been down to DNO loose connections, there could be a lot of nuisance tripping with these new devices if my worry is correct.


  - Andy.
Parents
  • 0
    Some commercial sensing systems have been designed use 23 -24MHz  as an internal frequency because it is supposed to be quiet - being midway between the two "free for all" ISM frequencies at 13.5 and 27MHz.(and another one at 6.7ish MHz is an ISM frequency in the US). In reality the HF band is anything but quiet, and this is the sort of assumption made by folk who cannot tell the difference between natural background noise, man made interference, or the noise floor of their own test-gear. (I've seen quite serious publications that have made both of these errors at different times, and concluded that there is either no interference or the band is not in  use)

    Such unlucky folk seem to be employed by proponents of RF over power line comms, and more recently wireless car charging, I wonder if- perhaps at some point they were involved in the RF part of AFDD design.


    You could  make a design that looks at the current and also for variation in the LN voltage and determine if a fault was up or down stream, but I'd be quite surprised if they do.

Reply
  • 0
    Some commercial sensing systems have been designed use 23 -24MHz  as an internal frequency because it is supposed to be quiet - being midway between the two "free for all" ISM frequencies at 13.5 and 27MHz.(and another one at 6.7ish MHz is an ISM frequency in the US). In reality the HF band is anything but quiet, and this is the sort of assumption made by folk who cannot tell the difference between natural background noise, man made interference, or the noise floor of their own test-gear. (I've seen quite serious publications that have made both of these errors at different times, and concluded that there is either no interference or the band is not in  use)

    Such unlucky folk seem to be employed by proponents of RF over power line comms, and more recently wireless car charging, I wonder if- perhaps at some point they were involved in the RF part of AFDD design.


    You could  make a design that looks at the current and also for variation in the LN voltage and determine if a fault was up or down stream, but I'd be quite surprised if they do.

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