This guide describes VLF withstand and other diagnostic tests and the measurements that are performed in the field on shielded medium and high-voltage cables rated 5 kV and above with extruded and laminated insulation. VLF test methods utilize ac signals at frequencies less than 1 Hz. The most commonly used, commercially available, VLF test frequency is 0.1 Hz. Whenever possible the guide addresses testing of complete cable systems. Tables are included of the recommended test voltage levels for installation, acceptance, and maintenance tests.