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 54 replies
  • Subscribers 30 subscribers
  • Views 4697 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

Caravan RCD trip power connections

Paul R
Dear all , a holiday question


I have an acquaintance who asks why his IET 18th Edition RCD tester when plugs it in to the Local RCD (<30mA/300mS) , the primary supply RCD trips (that is further up the AC supply line) , rather than the caravan’s, so in effect nullifying the test.

Is this because the Primary Supply RCD  is monitoring a small standing current from other connections and the Local RCD needs to be tested by using the Local Earth at the unit ? ( which is not so easily accessible). 


Are there any other thoughts please ? 


Paul , Swindon LN IET. 



Parents
  • 0
    When you clamp a ring of magnetic material around a current carrying wire  you are in circuit diagram terms adding a small inductance in series - a few microhenries for a typical clamp meter.  When you open the jaws, this equivalent inductance drops sharply, so if there was current flowing at the time, as LI  has to be conserved, you create a small voltage spike. This induced transient may or may not be equal in L and N conductors, and an RCD near the edge of tripping, or susceptible to short duration signals (and some electronic ones are over sensitive to fast edges/ high frequency) could just be set off.
Reply
  • 0
    When you clamp a ring of magnetic material around a current carrying wire  you are in circuit diagram terms adding a small inductance in series - a few microhenries for a typical clamp meter.  When you open the jaws, this equivalent inductance drops sharply, so if there was current flowing at the time, as LI  has to be conserved, you create a small voltage spike. This induced transient may or may not be equal in L and N conductors, and an RCD near the edge of tripping, or susceptible to short duration signals (and some electronic ones are over sensitive to fast edges/ high frequency) could just be set off.
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