Is there any standard or norm for this situation?

Question

Considering a metallic enclosure(which has PSU and electronics in it) with an IEC mains socket, an example shown below:

And it uses an IEC power socket such as:

For this kind of enclosure is there any standard about the order of connecting the enclosure to AC mains? Should the mains cable to IEC socket of the enclosure connected first and then the plug should be connected to the AC wall outlet? Or first the mains cable should be connected to the AC wall outlet and then to the IEC socket of the enclosure? Which has more risk of electric arc or safety?

By mains cable I mean this cable which powers the enclosure:

Answer 1

Theroetically speaking: Both connectors have roughly the same specification, so they are capable of bearing same loads, withstand the same voltages etc. It doesn't make any difference which to connect or disconnect first, even arcing should be controlled likewise by creeping distances selected accordingly. Both connectors will ensure that the protective earth is connected first an disconnected last. The geometry prevents touching live parts for both. So there is no theoretical order for establishing connections.

Practically speaking: It's no good to use one of these as a switch. It will increase wear due to limited arcing. So concerning the design of devices connected via both of these connectors there should be another component like a switch which connects the circuit after plugging in both connectors and disconnecting the circuit before unplugging any of them. However as you can see for all appliances, there is no lockout mechanism to ensure a switching by proper switch or relay before plugging. It's nearly impossible to build such a switch.

Both plugs are meant to survive a plugging operation under full rated current (typically 16 A) and survive arcing in case of short circuits. However this is valid only if lines they are connected to are properly fused or equipped with breakers.

Edit For your headline whether there's a standard or norm. A standard or norm is something which can be an obligation to either a manufacturing industry or trained personnel only. But both connectors can be found on household appliances so there is no applicable rule like standard or norm. If one had wanted to ensure a proper connection order by untrained personnel then it had to be implemented by technical means like some sort of lockout mechanism.

Answer 2

The cable is ok, but the connector is "wrong end", you should use a receptacle instead. The cable ensures that the ground connection is made first, while the other contacts it doesn't matter, as the user might plug it either way in the socket, so they are effectively the same.

There is no regulation on which end of the power cable needs to be plugged first, but if you have a capacitor in your device it needs circuitry to make sure the power cord doesn't present a voltage when disconnected.

More details are needed to point any standards (mainly application and which geographical areas you plan to sell to). But a few basic things that come from some regulations and make your life easier for passing global regulatory testing/evaluation:

1. Grounding should be done to one point, bus bar or screw

2. Areas near connectors with mains voltages need to be insulated. A plastic sheet or such will suffice for insulating the chassis and a plastic cover on top to prevent touching the parts or the wires from escaping if they come loose might be needed. Now you have the screws exposed and with metallic case you would need to protect the surface where the connector may touch in case it comes loose. Having the ground pin in the inlet is not enough, as not everyone might have an RCD.

3. Input fuse right after the input connector is required by many regulations

4. You need to ground all exposed conductive parts if you are aiming for class I device