The ITER ICRF antenna will operate at a considerable plasma-wall distance. In these circumstances it is expected that the ICH&CD system will routinely deliver power near its maximum voltage in the Main Transmission Lines (MTL). On the other hand during ICRF heating of JET plasmas the distance between the plasma separatrix and the ICRH antenna is usually kept to a minimum in order to maximise the power coupled to the plasma. This is necessary in order to compensate for the drastic reduction of the coupling resistance Rc that occurs when the plasma goes into H-mode, due to the depletion of the density in the Scrape-Off Layer in front of the antenna. As a consequence of this the maximum voltage in the MTL line also increases, leaving less headroom to cope with fast transients like ELMs. However it has also been shown [1] that the proximity of the midplane plasma separatrix to the outer wall (RF antenna) increases the power necessary for the transition to H-mode.