Residual Current Circuit Breakers (RCCBÆs) - Problem 3

[claver]

We have a stange problem involving RCCB. We have 6 battery chargers connected to a 3ph supply – 240V line to line (2 Chargers on phase 1, 2 chargers on phase 2 and 2 chargers on phase 3 .. All chargers are 240 so we have had to connect them line to line to get the correct voltage, Each charger can pull 3.5kW … We use a 50A 3ph supply.
We have a 30mA RCCB on each phase (

http://www.hager.com.sg/menu/produc...ircuit-breakers---rccbs---elcbs/800-1483.htm)

. The equipment has been working fine in New York. We then move the equipment to Chicago and we now have constant problems with 2 RCCB’s tripping almost immediately. The chargers and cabling is fine, no damage …

Is it possible that the supply (which is obviously upstream of the RCCB’s) can have any influence on a RCCB ?? The only thing that has changed is the electrical supply …from one geographical location to another … My understanding of RCCB’s is that any problem before (upstream) the RCCB’s is irrelevant … it only measures what is downstream ….

Would much appreciate if anyone could put some light on this …

 

[claver]

Thanks for that info - I will upload a sketch of the circuit we use over the weekend.

Have a good weekend !!

 

[waross]

Is it possible that the supply (which is obviously upstream of the RCCB’s) can have any influence on a RCCB ?? The only thing that has changed is the electrical supply …from one geographical location to another … My understanding of RCCB’s is that any problem before (upstream) the RCCB’s is irrelevant … it only measures what is downstream ….

As far as cable leakage and capacitive currents, if these are upstream of the Ground Fault Interrupting breaker they will have no effect.
However harmonic distortion on the supply system may have an effect on GFIs.
Uneven voltages to ground that may occur with different systems may have an effect on GFIs.
Another possible cause is that you do have ground leakage in your chargers but there was a bad ground connection somewhere in the system that was not allowing leakage current to flow and trip the breaker. If you then moved to a location with good quality grounding the breaker would then trip.
A quick test that we should have mentioned earlier is to "roll"the chargers. Move the chargers on phase "A" to phase "B". move the chargers on phase "B" to phase "C" and move the chargers on phase "C" to phase "A".
If the same breakers trip, measure the voltages to ground. Look for a supply problem.
If different breakers now trip check the chargers that cause the trip.
Please do this simple test and report back to us, and we may be able to help you further.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[claver]

Very good point Bill !

I have just received email that our equipment have arrived in California ... Will check on Monday and let you all know the outcome. The 8 hour time difference makes it all a bit difficult.

 

[waross]

No problem. This is an international forum and we work together well with +/-12 hour time differences.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[slavag]

O.K.
I read several documents on the topic and start understand, that possible also other problem. In Claverh's scheme RCCB's are protected on chargers. Possible DC components in the residual current. I surprised to know , that possible order several types of RCCB's. please see attached document.
Maybe this type of RCCB not applicable to this scheme.
Best Regards.
Slava

 

[slavag]

Keith. You are right. Please see Hager's comments:

"To prevent nuisance tripping all the RCCB's are protected against transient voltages (lightning, line disturbances) and transient currents (from high capacitive circuits). RCCB's Type A for DC-pulsating faults or time delay devices are available, please consult us."
Regards.
Slava

 

[itsmoked]

transient currents (from high capacitive circuits)

Though that is most definitely not what I'm referring to.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[claver]

Hi All who have provided valuable help on this subject... Just to let you know that our machine have been in California for a week now... and NO problem with the RCCB on the machine!!

We have made no change to the equipment ...Same extension cable.. The supply we are connected to now is in a new building.

So it looks clear that the SUPPLY (upstream) was the problem ....

Have a great weekend !

 

[gepman]

As I said before, the electrons out here in California are better!

Probably as waross and others said that the harmonics were a problem at your previous location.

 

[slavag]

Gepman.
Not only electrons are better, I'm hope, weather is better too.
Claver , thank you for the feed back.
Regards.
Slava

 

[itsmoked]

slavag; It's rained here everyday for two weeks... Been in low 40s.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[claver]

Thanks ! Glad to hear that the electrons are better behaved in California..

On the question of Harmonics ... This is outside my expertise, Can you "measure" this ? I am concerned if we ship the gear to another part US and have similar problems... I was even thinking about removing the RCCB.... Not a good idea for safety I know... So that is not really an option...

 

[EddyWirbelstrom]

Does the installation have only one neutral-to-earth ( ground ) connection and is this neutral-to-earth connection upstream from the RCCB ?
A neutral-to-earth connection downstream from the RCCB would result in healthy single phase current returning to the source via the earth conductor which is external to the RCCB toroid CT, this would be seen by the RCCB as earthfault current. Conversley an earthfault would result in some of the earthfault current returning to the source via the neutral conductor, this would result in the RCCB sensing an earthfault current lower than the actual earthfault current.

The three phase conductors plus neutral must pass through the toroid CT. Slavag's attached file demonstrates the required connection.

 

[gepman]

Yes you can measure voltage and current harmonics. I carry a small inexpensive Amprobe 41PQ which measures voltage and current Total Harmonic Distortion up to 600V and 1000A to the 51st fundamental frequency on 60Hz systems. It also measures power, power factor, reactive, and apparent power besides volts, amps, ohms, and frequency.

For more detailed investigation I use a Fluke 433 which has been replaced by the Fluke 434. This gives a measurement of each fundamental frequency out to the 51st fundamental.