RCCB help

"The case is that, a fault occurred at data server that supply by the power socket of circuit A(1). The 32A RCBO was tripped. When I tried to reset the RCBO, it tripped again immediately."

So what did you do to determine and correct the cause of the 32A RCBO trip? Nothing? Did you just attempt to reset the breaker without knowing why it tripped? If so, that alone could be the base cause of the additional trips. You were closing into a fault and that brief current surge caused a momentary imbalance that was detected by the other RCCBs as non-return current.

Dear JRaef, thank you so much. The cause had been found and isolated. Could you explain more on "current surge caused a momentary imbalance that was detected by the other RCCBs as non-return current". Thank you

current surge when highly inductive in nature can cause imbalance i.e. current going in may be higher than the current going out. This may have caused operation of RCCB.

There is an earth fault which is causing the RCBO & RCCBs tripping,Find out the fault by check your all cables & their insulations.I am sure there is an earth leakage in the system.

What about the voltage is it stable?

Thank you so much. The cause had been found and isolated, but I haven't check the voltage level, will it cause the RCD tripped?

No MCCB or MCB was tripped, only the the RCCBs were affected. That caused around 7 nos. of servers downed. Finally, a fault equipment at circuit A(1) had been isolated, and all circuits had been reset. My question is that ;

1) Why the other RCCBs at the final circuit of the separated circuits were tripped during I reset aforesaid RCBO?

2) How the fault affect separated circuits?

Circuit diagram is attached

A1) Because as the circuit with the true fault was reconnected without being corrected, the protective devices on the other 7 circuits also saw that fault momentarily and did what they are designed to do.

A2) Because the current appearing in the circuit protective conductor on the circuit with the true fault found its way back to the supply via the line conductors of the other 7 circuits during the reconnection event.

Dear Marcolao,

1/ I am inclined to think the breakers that tripped tripped on residual current, 30 mA??, not overcurrent. Did the equipment fault found on the faulted circuit suggest this?

2/ The circuit diagram does not tell you everything about the real circuit. In particular, there are safety earthings/groundings of all the panel metalwork and all the cases of all the electrical/electronic equipment. All the panels may be bonded to each other. The impedance of all this may be lower than the apparent earth wire of an individual RCD/RCBO and most of the current of an earth fault may go via multiple routes not apparent from a circuit diagram. What information I have on the impedance of wires in conduit states that the impedance of an earth return on the outside of a conduit is always lower than DC measure.

3/ My own testing of RCDs at hardly more than the nominal maximum of 30mA finds that they trip far faster than half a cycle, although the standard requirement may be 0.2 seconds. It is quite possible they could respond to a capacitance charge/discharge surge driven by the 340 peak of nominal 230V at the instant of an earth fault. Note that the EMC filters on good equipment will have their capacitors returned to the metalwork of the equipment.

4/ I would wonder if the 6 circuits spuriously tripped shared a 3 phase or other cable or conduit /trunking with the faulted RCD/RCCB??

5/ RCCB/RCBO devices do not usually have a time delay to allow discrimination or indication of if trip was overcurrent or residual.

6/ It is not clear if there are any sub-circuits beyond the 32 Amp "final" breakers which could be made to discriminate by time and/or current to avoid the spurious tripping.

7/ Wiring regulations do warn about the build up of standing residual currents due to capacitance currents of electronic equipment EMC filters. Note that imbalance is inherent because the voltage to earth of neutral is normally low while live is at line voltage, EMC capacitors from live and neutral to earth are always of equal nanofarads. This can make apparently separate circuits more sensitive than their residual nameplate.

8/ 32 A single phase devices are often DIN rail mount and easy to change to another make.

9/ I would suggest consulting the makers of the breakers that tripped about how sensitive they are and if there is an alternative.

10/ Also contact the premium breaker makers about the problem, of which they may have experience and a solution. Siemens and Brown Boveri come to mind.

67model

Further circuit diagrams are attached for your reference. Thank you so much.

http://www.engineeringexchange.com/forum/topics/help-rcd-trip