work fuse box breakers trip sometimes, including rcd plug. (uk electrics question)

[jimmyhackers]

intermittant problem at work. wanted some clarification

at the warehouse at work....there is a larger fuse box with a single large breaker feeding a fuse box inside a portacabin.

most/all of the sockets in the portcabin have a built in rcd (LN trip delta of 30ma).

some of the test equipment also has an rcd plug with a LN delta of 30ma.

the fuseboard rcds/breakers that are tripping are also all LN delta 30ma

ive forgotten thier overcurrent trip values....but will clarify on monday

there are numerous extension leads plugged into the portacabin rcd plugs and various tools and test equipment gets use at times..... needless to say sometimes breakers get tripped.

however, sometimes the main breaker/rcd feeding the portacabin will trip and not the portcabin one.... sometimes both will trip.....sometimes only the rcd plug sockets or rcd plug on the test equipment will trip.
sometimes the rcd plug will trip as well as the two breakers.

sometimes the non rcd plugs or quick connects will blow thier 3a fuses and still trip the main fuseboard and portacabin breakers.

my question is about their tripping order and if more than one should trip at a time.
mainly why sometimes the portacabin breaker doesnt trip but the the breaker feeding the portacabin in the main fuseboard will?

basically.....i want advice on how to make them not all trip at once....ideally id only ever want the one closest in the "chain" to the end user (me) to be the only one that trips.

 

[fechter]

That's a tough one. If a load has a fault that is over the RCD limit, both breakers will see the same fault and both will want to trip. The fastest one will trip first. What you want would is a short delay on the main one, but not sure if that's an option.

 

[marty]

Better way to solve the problem. Stop doing whatever ya doing to make breakers pop.

Example - If running the toaster and microwave pops the breaker. Make toast then heat coffee in the microwave. If you want to run toaster and microwave at the same time? They need to be plugged into separate circuits.

Overloading electrical stuff can cause a fire.

 

[jimmyhackers]

im the rma person there (returned merchandise authorization)

i test/fix the returned products (led street lights) some trip and/or pop stuff.

also the testers (essentially live mains prongs) pump mains voltage into the new lights other staff use, and i guess sometimes they miss :S.

tripping the breakers is kind-of unavoidable.

i was thinking some some of power isolator.....ie a 1:1 transformer... with a trip on the mains out side.

are they a thing?