ForewordA significant investment with respect to electric power distribution is in cable systems. A high degree of reliability and reasonable life expectancy of the cable systems are necessary. In order to guarantee optimum performance of the power cable system@ standards and guidelines have been developed which address the specific testing requirements for service-aged extruded and laminated dielectric insulation. This Guide is one part of an omnibus Guide that discusses known techniques for performing electrical tests in the field on shielded power cable systems.This guide provides a description of the methods and practices to be used in the application of very low frequency (VLF) high voltage excitation for field testing of shielded power cable systems (Bach [B1]1 and [B2]; Baur@ Mohaupt@ and Schlick [B5]; Gnerlich [B8]). VLF testing techniques@ effective for a broad range of cable types@ provide a new method of evaluation@ and help to fill the need for more complete information on the cable system condition while minimizing or eliminating some potential adverse charging effects of the direct voltage high-potential test method (commonly known as the DC Hi-Pot test) (Eager [B6]; Groenefeld@ von Olshausen@ and Selle [B9]; Steennis@ Boone@ and Montfoort [B19]). This guide addresses VLF testing in the frequency range from 0.01 Hz to 1 Hz.The information contained in this guide is intended to provide the methodology@ voltages@ and factors to be considered when utilizing VLF testing@ whether as a withstand test or as a diagnostic test. For general information regarding other field testing methods@ refer to the omnibus standard@ IEEE Std 400?.2ScopeThis guide describes very low frequency withstand and diagnostic tests and measurements that are performed in the field on shielded medium voltage cables with extruded and laminated dielectric insulation. Whenever possible@ cable systems are treated in a similar manner to individual cables. Charts are included as an aid in identifying the effectiveness of the VLF test for various cable insulation problems.