Pantograph-equipped locomotives must not run through a section break when one side is de-energized. The locomotive would become trapped, but as it passes the section break the pantograph briefly shorts the two catenary lines. If the opposite line is de-energized, this voltage transient may trip supply breakers. If the line is under maintenance, an injury may occur as the catenary is suddenly energized. Even if the catenary is properly grounded to protect the personnel, the arc generated across the pantograph can damage the pantograph, the catenary insulator or both.