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Comment by baybal2 | Hacker News Reader

> A fused neutral design would leave all of the bulb electronics hot. Strange.

Depends on what country you are living in.

It's not new for me to see a product passing safety certification in one country, failing in another, but still ending up in it because of messup by people running the OEM industry.

Second to it, in a normal country, for an electrical appliance, failing short, and triggering a short circuit protection is a relatively safe alternative to having a dedicated fail safe circuit, but in countries with building codes not saying anything about wiring safety, it often means a fire.

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Anyway European Schuko plugs are not even polarized, there is no way to know which wire is hot.

Honestly, I think it's better that we view polarization as a historical oddity. So many people don't understand the concept.

Even I have trouble understanding the real difference between ground and neutral, because neutral connects to ground in the breaker panel. I'm not even sure if neutral goes through the breaker?

Note, the below will be for the US -- rules will be different in other countries.

> Even I have trouble understanding the real difference between ground and neutral,

Neutral is the normal return path for current. Under normal operation power is delivered to a device via the "hot" conductor, and travels back from the device to the source over the neutral conductor.

The ground conductor is present for safety purposes. Under normal operation no current should flow over the ground conductor at all. The only time the ground should have a current flow is during a safety event (i.e. a short from hot to the case of a device with a metal case).

> I'm not even sure if neutral goes through the breaker?

It does not, the breaker is present in the "hot" conductor path, and tripping the breaker disconnects just the hot conductor from the power source.

Power flows opposite current, doesn't it?

I've never heard of that description in all my years as an EE. Do you have a citation or reference to that description?

Power = I^2*R so power is positive regardless of which way the current is flowing. (rms current in the case AC, not accounting for power factor)

Right, power can be extracted from flow of electrons/holes, regardless of the direction...

(usually) electrons moving.

The purpose of separate wires is twofold:

1. It's to provide protection in case of neutral failure. If you have an appliance with the case grounded via neutral and the neutral wiring fails, you now have the case connected to live (through any appliance that is switched on). With separate ground, nothing happens as you are only allowed to connect ground to neutral at a point where failure of the upstream wiring is practically impossible (i.e., wires so thick that they practically won't break).

2. It's to provide a path for ground fault currents that does not pass through the RCD, if you have an RCD. While neutral doesn't go through the circuit breaker, it does go through the RCD, so as to measure the difference in current between live and neutral. If your appliance is grounded vial neutral, any ground fault (connection from live to the case) looks like regular load current to the RCD, if it is grounded via separate ground, the fault current bypasses the RCD and thus causes it to trigger, even for a small current that would not trigger over current protection.

Neutral exists separately from ground only because if there is some residual resistance in the line, there will be voltage on the neutral.

So you have a separate ground that normally sees no voltage at all.

You are correct, the neutral does not go through the breaker. It is usually wired inside the breaker panel though.

Some localities want the neutral and ground wired separately (to separate bus bars), with a single point connecting them, but most don't care and the neutral and ground are attached to the exact same place inside the breaker panel.

Electrically, the neutral and ground are at the same potential, assuming magic wires with zero resistance, but in the real world the wire does have resistance, especially if it was poorly installed, so they are not always at the same potential. There could also be capacitance in the line.

The neutral handles the expected load, while the ground is designed specifically to be an alternate current path from the case (assuming it is conductive) that has low resistance and will immediately flow enough current to trip the breaker in case the hot somehow comes into contact with the case.

Neutral does not go through the breaker, correct.

Considering how popular unpolarized plugs are all over the world I don't think a fused neutral is much of a problem in a lamp.

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