Voy a participar en el Campeonato de España de triatlon de larga distancia ITU 3000-120-30, se podría hacer un entrenamiento específico para esa distancia?
Interesting distance 
You could either go with the ‘Custom Configuration’ or just go with either Half or Full-Ironman plan depending on how much emphasis you want to put on long run and ride development (Ironman plan puts more emphasis).
I would also in any case put the event distance in the Plan System Prompt so the agent working on the training plan is aware of it