I am not licensed in WA, so this answer should not be interpreted as legal advice, which can be given only after a lawyer has been able to gather all facts, ask follow up questions, and perform any needed research. No attorney-client relationship is formed by way of this answer; such a relationship would exist only after the execution of a proper, written retainer agreement.
Generally, obtaining an injunction can be a complicated process that even many lawyers can find difficult. Based on your simple explanation of the problem, though, and depending on the state laws in Washington, you may be able to get a protective order that would accomplish your goal. More and more states are making pro se protective or restraining orders possible, and some states have forms and instructions available on the Internet.
So, if this person is a guy in the neighborhood who just keeps messing around with your electric meter at home because he's a pest, a simple pro se restraining or protective order might be the route to go (although to be safe, you may wish to have the assistance of an attorney since court staff cannot provide you with legal advice). But if it's a larger issue (such as a business dispute over ownership of the equipment), you'll really want to get a lawyer involved.