4 ms·
This must be a European design. In the USA, governed by NFPA 70 - The National Electric Code, the ground rod's purpose is to establish the ground voltage refer
by rainbowzootsuit 4y ago
This must be a European design. In the USA, governed by NFPA 70 - The National Electric Code, the ground rod's purpose is to establish the ground voltage reference to reference the electrical systems of a building to it and to dissipate any charge buildup on the circuits.
The ground rod is not there to carry current to interrupt a fault to "protective earth" - the green or green/yellow. The circuit breaker interrupts a short as you bring the protective earth wire back to the main disconnect of a building where it bonds to the neutral wire.
If a fault occurs, an unregulated amount of current flows on the protective earth wire to the breaker panel and a circuit breaker interrupts the circuit.
- magicalhippo 4y agoI'm no expert, but here in Norway we predominantly have IT systems[1], though new installations are mainly TN. In the IT systems, the protective earth is not bonded to the neutral. Thus in case of a fault, the protective earth should be low impedance to ground so that the circuit breakers trip. At least that's my understanding. [1]: https://aktif.net/en/types-of-earthing-systems/#IT_System https://aktif.net/en/types-of-earthing-systems/#IT_System
- rainbowzootsuit 4y agoThanks for the link. I don't know all the symbology there so it will take some reading up.
- taneq 4y agoTechnical nitpick, if it detects earth leakage and trips based on that, it's an RCD, not just a circuit breaker. Otherwise yeah, there's different approaches to earthing - in Australia for domestic stuff we have mandatory RCDs which work as you describe above, but then also in industrial/mining settings we have the big green/yellow cables which will directly sink current (potentially hundreds of amps) to ground, hopefully stopping you from getting bitten.
- rainbowzootsuit 4y agoA thermal breaker won't trip on leakage current or arc faults either. I was trying to describe the classic "dead short" that will trip a thermal circuit breaker or fuse without the circuitry for arc or leakage detection.