I was involved in a number of rental projects where the primary load was an arc furnace. It was a pretty ugly experience and it required a good bit of work to make it successful for the time required for the utility to finish up their substation work.
As I remember everything had to be way over-sized, one job I still have a few details on,
4 groups of 10 2MW generators feeding utility supplied 40MVA transformers each,
To get first unit on line for each group we had to do a dead gen/dead bus gen breaker close and ramp the generator up, then the other 9 units could be paralleled to make the group "ready".
When first two groups up and running some auxiliary plant equipment was brought online, not sure what it was since the plant was about 2 miles away, but I do know whatever that equipment was it was very tolerant to a low voltage condition.
Third and then fourth step up transformers were energized by the two groups already online, then the remaining generators were brought online.
With all four groups of generators online, the arc furnace start sequence came on, for that "first start" we had to have a second under/over voltage settings group active to allow for the large swings, once arc was established and stable we could slowly bring units offline and plant would bring on other aux loads. We would usually end up with 12-15 units remaining online at about 40-50% kW and about 80-90% kVA load. Technically we were off the reactive capability curve but the factory engineers felt we had enough "extra" in those tail ends at the time.
Every Monday morning at about 2am we did the start, at midnight on Friday they did a stop sequence that took about 4 hours.
On that particular job we failed 12 AVR's and 2 generator ends over a 2 month period. At that time our 2MW portable units had a reputation of being very rugged and reliable, it was one of the worst rental jobs we ever had, but we ended up doing 7 or 8 of them over the next couple of years.
As I understood it these were fairly small furnaces, mostly dealing with scrap recycling in the USA midwest.
I seriously doubt that the current model 2MW portable power units by several companies would be able to deal with the harmonics, low power factor and load instability we saw on the units we used at the time, at least in my opinion.
Hope that helps, MikeL.