The triumph says to "Complete a Seraph Tower Public Event without failing a single Support Tower charge cycle." I was able to complete the event where every time the support tower charged it was "successful," as in no enemy interference and it emitted seven polarity charges. Either it also means you cannot miss a polarity charge throw as well, since during the last one orb was missed and we had to wait for the support tower to charge again (which was successful), or that an enemy can never set foot on a support tower that is charging. It's either one of those things or the triumph is bugged right now.