Rccd tripping

[pjelec]

I have been called out to a complex where a flat had a tripping Rccd. I have done an Insulation Resistance test and the readings were >999 on all circuits. The strange thing is that 7 other flats also had the same problem at the same time. Some were tripping every 10 minutes. None had problems before. The voltage in the flats are between 233v and 237v. Another electrician had been called out and he changed an Rccd. The one installed was a 40amp, 30ma, 230v. He changed for the same but 240v. I can not see the difference it would make, even though it had not tripped.
I went back today and managed to see three of the flats and they tell me none of the Rccds had tripped in 24hrs.

I am a little stuck and dont know what direction to go in.

 

[Darkwood]

If several flats from are tripping their own independant rcd's at similar times when its not been an issue before then its possible its not a fault as such but interference in the supply, were the flats on the same phase?.... is their anything that would generate harmonics local to the supply (Telephone masts on top of building etc), are the rcd's covering the power supply to the flats as 40amp sounds small but is plausible.
More info please?

 

[pjelec]

Thanks Darkwood. Something for me to look at about the phases. The flats are split between 3 phases although each flat is single phase. The rcd´s are in the consumer inside each flat. There is no rcd on the mains to each flat. There is no masts on top of the block. It is only a 3 storey building.

 

[Darkwood]

In respect of the info just given i would be looking at the likes of neutral mains connections are good and or the phase if all on same, poor, overheating or arcing in cables common to all flats, that or its a one off mains glitch.

 

[garysparky1]

is'nt the rcd tripping because of an imbalance between the line and neutral therefore earth leakage ?

 

[pjelec]

That was the first thing I checked. Using an insulation resistance tester the reading between Neutral & Earth and Live & Earth the reading was > 999megohms

is'nt the rcd tripping because of an imbalance between the line and neutral therefore earth leakage ?

 

[Darkwood]

is'nt the rcd tripping because of an imbalance between the line and neutral therefore earth leakage ?

if OP is correct in what he says and several rcd's tripped within a short period this goes out of the scope of normal rcd tripping circumstances as they all look at their own load and would be rare for a couple to trip never mind several.... question to OP is how old are these rccd/rcds unit as the old ones independantly monitored earth leakage and could be tripped from an external faults not related to monitored installation

 

[Top Cat]

In respect of the info just given i would be looking at the likes of neutral mains connections are good and or the phase if all on same, poor, overheating or arcing in cables common to all flats, that or its a one off mains glitch.

Agree 100% spot on.