What device indicates that a high-voltage line is de-energized?

The correct answer is indeed the high-voltage voltmeter. This device is specifically designed to safely measure the voltage levels of high-voltage lines and is equipped with the capability to indicate whether a line is energized or de-energized. By checking the voltage present in the line, a high-voltage voltmeter can confirm the absence of electrical power, which is critical for ensuring safety before any maintenance or repairs are performed on the line.

In contrast, a clamp-on meter is typically utilized for measuring current flow in conductors without direct contact, but it does not specifically indicate whether a line is energized or de-energized. A ground resistance tester evaluates the resistance of grounding systems, which is important for safety and functionality but does not relate to the status of high-voltage lines in terms of energy. An insulation resistance tester assesses the integrity of insulation in electrical systems, ensuring that it is effective in preventing current leakage, but it also does not provide a direct indication of whether a high-voltage line is energized or not.

The application and functions of the high-voltage voltmeter make it the appropriate choice for determining the energized state of high-voltage lines, emphasizing the importance of this device in electrical safety practices.