Safety and Underground Systems - Instant Video
This 26-minute Instant Video covers the basic concepts of underground systems, with emphasis on safe work practices unique to underground work. It discusses safety considerations that apply to transformers used with underground distribution, and during the installation and switching of underground equipment.
Introduction – 3 minutes
Describes live-front and elbow-connected padmount transformers.
Underground Installation – 6 minutes
Demonstrates how to direct bury underground cable. Explains the advantages of this method in residential, commercial, and light industrial areas. For denser city areas, it shows how to install cable in conduits and vaults. Also discusses: Traffic hazards, public safety, safety in underground confined spaces.
Underground Switching, Part 1 – 5 minutes
This section shows how to ground a piece of substation equipment after transferring its load, isolating, and de-energizing it. How to test for backfeed voltages, how to install grounds on a transformer, how to tag isolated equipment.
Underground Switching, Part 2 – 5 minutes
Demonstrates how to isolate a damaged cable by disconnecting it at the substation, and at above-ground pole top terminations.
A More Complex Switching Job – 7 minutes
How to remove a switching station from a loop-type distribution system. In this example, the switching procedure involves 16 steps, each of which are explained. Demonstrates the concept of close-before-open when working on loop-type systems. Emphasizes the importance of these steps when disconnecting cables: Isolate, test, ground, and tag.