本指南描述了在现场对额定电压为5 kV至69 kV、具有挤压和层压绝缘的老化屏蔽中高压电缆进行的VLF耐受性和其他诊断测试以及测量。VLF测试方法使用频率小于1 Hz的交流信号。最常用的商用甚低频测试频率为0.1赫兹。只要有可能，电缆系统的处理方式与单独的电缆类似。表中列出了安装、验收和维护试验的推荐试验电压水平。

This guide describes VLF withstand and other diagnostic tests and the measurements that are performed in the field on service-aged shielded medium and high-voltage cables rated 5 kV through 69 kV 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, cable systems are treated in a similar manner to individual cables. Tables are included of the recommended test voltage levels for installation, acceptance, and maintenance tests.