# How to stop current originating from common ground wire?

A building has all the apartments' electric panels connected to a common ground wire. Theoretical situation:

1. one of the building's electric panels has its differential circuit breaker broken
2. it also has a broken appliance that is permanently sending current to the ground wire

Therefore, the building's common ground wire has current flowing permanently. How can an apartment owner stop current from getting in his apartment through the common ground wire but allow current to flow out?

• Why hasn't the broken breaker been replaced? – longneck Nov 27 '19 at 19:08
• Are the individual unit (apartment) distribution boards (electrical panels) connected to some sort of metering/main-cutoff assembly that provides cutoffs for the apartments? Or are they all equipped with individual main cutoffs, and tied directly to their meters? – ThreePhaseEel Nov 27 '19 at 22:06
• Are the apartment feeders 3 wire or 4 wire? – Ed Beal Nov 27 '19 at 22:31
• Also, where on this planet are you, anyway? – ThreePhaseEel Nov 28 '19 at 5:52
• @EdBeal 3 wire: phase, neutral and ground – Keisuke Nov 28 '19 at 9:32

## 3 Answers

There should be another breaker upstream of the broken breaker.

• I don't think this answers the original question, as they want to continue using their electricity. – Daniel Griscom Nov 27 '19 at 20:37
• There is a breaker for that apartment but that does not solve the problem. See my reply to Edward Kirton's answer. – Keisuke Nov 28 '19 at 9:36

Sounds like an unsafe situation. To find the offending circuit, monitor the ground while opening/closing each breaker.

• But how can an apartment owner protect his apartment from this kind of situation happening again. How can he prevent current from the ground wire from entering his apartment while allowing current to flow out? – Keisuke Nov 28 '19 at 9:35

With a 3 wire system the only way I would know to find the problem would to add an impeadance (resistor) in each apartments ground and measure the voltage. The only way to prevent the problem is to ass a rcd to each apartments supply and when the current on their ground raises to 50 ma it will trip the offending apartments breaker (I believe RCD breakers are set at 50).