The Kazon don't have transporters, but that doesn't mean they don't have a way to board the Array. And with Voyager
's brief contact with the Kazon, how is Janeway supposed to know what the Kazon can or cannot do? They don't have easy access to water, but they have starships. That's a bizarre combination of technology that makes it difficult to predict else what they might be able to do or what other technology they may be weilding. Sure, we learned later that they're basically running their former master's ships, and probably doing only a passable job of maintaining them, but in the incident at the Array, how can Janeway legitimately risk leaving timed explosives behind when hostiles are right there, actively seeking to capture it, and possibly capable of thwarting her attempt to deny it to them?