Damian-Moderator said:
The recommendation is a max of 25mtrs.
However I am sure others will tell you that it is ok to have two and plug them together.
The danger of that is there is a potentially weak point at the junction of the two cables and volt drop along a longer length
The danger isn't a weak point at all. Where the danger lies is in having a 240V plug and socket lying on the floor. First of all the is the possability that the socket will get affected by damp and there is risk of electric shock. Next is the trip hazard presented to fellow site users again from the 60mm diameter plug and socket left unguarded on the floor.
If you do need to run a longer cable than the recommended 25Mtrs then have one made up to length as a one piece cable.
The longest standard 240 volt extension reel commercialy available is in fact 50Mtrs (see screwfix and B&Q web sites). Under Health & Safety Executive guidelines, if you are using mains electric on a public site, then they recomend that a 1Mtr cable of 240V be used to a transformer producing a max voltage of 110V for flex lead powered appliances.
There has to be common sense applied to loose cables on the ground, for example route your cable away from walking routes and do not cross vehicle routes.
In my working capacity I have to set my caravan up on farms for 6 wks or so to build poultry units. To gain access to electricity, I have got a 50Mtr cable with a 13amp plug (household type) and a socket to suit our caravan. Being an electrician, I did check the voltage drop and there was less than 4 volts which is still better than the continental 230V.
BTW as a safety measure, I use orange lead and place identification notices every 10Mtrs so that people can see the cable route.
Just remember. Electricity is the silent blind odourless killer!!!!!!!