Power cable connection on a mobile installation to External equipment using a MIL-DTL-38999 connector.

This all rather depends on what it is used for and how,
As one who designs a lot of green (or beige) equipment with Mil Std 38999 connectors, I'd consider that they are not anything special, except that the power handling and robustness for a given size is a bit better than the average IEC mains inlet ;-)  (NB some of the socket pin patterns are not touch-proof - do you know insert which pattern is it - there are far too many variants for comfort ?) 

They are however  very strong against being trodden on and even run over  (well by tyres at least), and  depending on the back shell arrangements and if they are gel filled or not, they can be very good in the wet as well, and are available in a selection of non-shiny finishes that dont attract sniper fire ;-)
But in terms of domestic mains, where none of that applies, they are not really ideal and not normally the first choice, as well as being very expensive and needing special crimp tools to fit.

So ---
Are the connectors intended only to be disconnected  as part of equipment breakdown for transport, i.e. when in use is the mains lead remains essentially captive when fitted ?
Is the cable a kind that could be easily damaged in a way that exposes a mains live core, or is the cable provided with an earthed braid or armour.

If the answer is that it gets unplugged regularly by untrained/unskilled personnel, or that the lead is soft skinned and vulnerable to trapping or puncture, then if it is carrying mains, some additional protection really is needed and the RCD uplift is unwise.
If the kit is to be used outdoors in all weathers then that is a further risk compounding factor.

Of course if the lead only carries a much lower voltage or is essentially protected along its length or indoors the risk is probably quite acceptable.

A bit more info may help clarify where between the extremes this lies.

Mike.

The regulations  say "Socket-outlet. A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to receive a plug. A luminaire track system is not regarded as a socket-outlet system.", is it part of the fixed wiring?

Strictly it may also not really be part of the fixed installation either - in some sense it may be classified as a product, or as a piece of machinery.. But an ambiguous legal position does not justify not evaluating the risk technically. 

Note that some of the 38999 socket patterns are have contacts you can touch with a finger  exposed at the mating face - while others are deeply recessed and meet clearance requirements.

Here is a catalogue page showing just  a few and a photo that illustrates the point.

Mike

Sorry to be so generic but there is only so much I can say. The connector is TV07ZN13-E4P and it's mating half. I've done a risk assessment and there is no risk of electrocution by touching the pins. The personnel are trained on the equipment so they are skilled up to a point. It is set up used then torn down. Protocol is to turn all power off for that connection before it is disconnected. There is also a continuity monitoring system that will cause the breaker to trip should the connection be lost in any way.

it's 230VAC.

Sorry to be so vague, there is only so much I can say. The installation is mobile, and yes I agree re the risk assessment hence a full risk assessment was done. My problem is that regulation 411.3.3 clause (iii) state that mobile equipment not exceeding a current rating of 32A for use outdoors has to use a current rating not exceeding 30mA for socket outlets and the risk assessment exception clause does not apply to it. Hence the question as to if we can class it a part of the installation.

The connector is a series 3 connector and is designed so that the pins cannot be touched accidentally and for extreme weather conditions.

 It connects on the front of one of the installations  power system units to provide power to the control systems that have to be dismounted a given distance away for safety reasons. So when you look at the system as a whole it is one system. Frustratingly I think we fall into a grey area when it comes to classifying it as a socket or part of the installation.

If you mean BS7671, then sockets that are part of the fixed wiring installation that supply mobile equipment have to be RCD protected.  But I am presuming this whole rig does not connect to the mains that way ? Can you say if it has a built in generator - and so is powered while mobile, and not just when parked up.

Those 'wiring' regs do not generally apply to any sockets that are part of the equipment itself - that would probably fall under the machinery directive instead, unless we are looking at 13A sockets in a caravan or a Portakabin type thing , when it is sort of a fixed installation for use by ordinary folk again. 

A 30mA instant RCD may not work but if it is really just an inrush issue, then a delay type of programmable earth fault relay example  operating a contactor in the supply might, and still afford adequate and regs compliant protection, as you can meet the 30mA requirement safety of life thing with up to a 0.2 second delay ( or 0.4 secs in some cases)

Mike.

yes it has an onboard generator, no it is not powered up while on the move, just when stationary.

We discovered recently that the designer of the generator unit used a 1/500 winding current transformer when they should have used a 1/1000. This means it was actually tripping at just under 15mA  - no surprise it couldn't take the inrush. (Long and tedious story. Please don't suggest the supplier changes it, been there done that still have a bleeding forehead from repeatedly banging my head against the wall.)

None of the RCD setting adjustment process from the Dev stage was written down (before my time), so I don't know if they gradually turned it up or just went straight to 300mA. Whether they tried a time delay I really couldn't say. The RCD does have detents at 100mA etc, and an adjustable time delay. We are going to have to go through that process now to determine if a lower setting would work. The lower the better in my opinion. 

I think in the mean time I'm going to have to go with 'It's not a general use socket and is a specialised connector supply one aspect of the system only' for now. Therefore not a socket in the sense that the regs mean.

I'd also play the for use by  'skilled and instructed persons only' card as well if you can. It is really not after all anything like a socket for use by ordinary/unskilled persons.
Indeed it is not being plugged and unplugged at all while genset is on I imagine? 

Fully understand the difficulty of changing the plans after something has been built and delivered - concession forms and engineering change costs etc. 

Mike.

Newfutile said:

The regulations  say "Socket-outlet. A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to receive a plug. A luminaire track system is not regarded as a socket-outlet system.", is it part of the fixed wiring?

BS 7671 also defines a cable coupler. This pairing has a 'plug' and a 'connector' ... however, this connector doesn't have an IEC, CENELEC or British standard ... so, to use them in an electrical installation for which BS 7671 applies (including those to BS 7909) would require a declaration of some sort (see BS 7671, Regulation 133.1.1 and Section 511).

Samantha Rendell said:

Given that it uses the 38999 connectors and it is solely dedicated to the dismounted control systems that form part of the system is this a valid assessment? 

Are the 'control systems' part of an electrical installation, or Machinery as defined in the Supply of Machinery (Safety) Regulations? If the latter, then BS EN 60204-1 might apply, rather than BS 7671?

gkenyon said:

The regulations  say "Socket-outlet. A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to receive a plug. A luminaire track system is not regarded as a socket-outlet system.", is it part of the fixed wiring?

BS 7671 also defines a cable coupler. This pairing has a 'plug' and a 'connector' ... however, this connector doesn't have an IEC, CENELEC or British standard ... so, to use them in an electrical installation for which BS 7671 applies (including those to BS 7909) would require a declaration of some sort (see BS 7671, Regulation 133.1.1 and Section 511).

Samantha Rendell said:

Given that it uses the 38999 connectors and it is solely dedicated to the dismounted control systems that form part of the system is this a valid assessment? 

Are the 'control systems' part of an electrical installation, or Machinery as defined in the Supply of Machinery (Safety) Regulations? If the latter, then BS EN 60204-1 might apply, rather than BS 7671?

Semantics again!

Is it an electrical installation or a machine? Or neither?? My first thought was whether this equipment is in scope or not. 110.1.1 says that the Regulations apply to electrical installations, so if it is not one, BS 7671 does not apply.

Is the device in question a "socket-outlet". Newfutile questioned this. I think that it is difficult to get away from the connexion being a socket and plug, but I am far from convinced that it is a "socket-outlet" as defined. More importantly, 411.3.3 is all about supplying electrical energy (the Grid in a building, PV, generator, WHY) from a socket upstream to an appliance downstream.

Most things are mobile if you have the capacity. I envisage a "machine", for want of a better word, which can be transported (perhaps to a battlefield, or more importantly, an exercise area), but which has to be broken down into components to make it mobile. If you didn't use some form of plug and socket, how else would you put it together? (I discount the notion of terminal blocks in enclosures.)