Underground Residential Distribution Transformers - Instant Video
This 49-minute video covers the basic principles involved in detecting a transformer problem, how to disconnect, replace, and reconnect a faulted subsurface transformer. Basic troubleshooting techniques are presented using an example in which a subsurface residential transformer has caused a power outage. Techniques for energizing and de-energizing are illustrated.Explains how to use the process of elimination to determine the cause of a residential power outage and how to use this process to locate the cause of a residential power outage. Shows how to use diagrams to locate circuits, transformers, and houses, and know how to plan a logical search for the cause of an outage.
Verifying the Power Outage – 6 minutes
Uses diagrams to locate the transformer, or transformers, that feeds houses reporting a power outage. Determines if residential customers reporting power outages are actually not getting power. Determines if a problem in the primary circuit is the cause of a power outage.
Identifying a URD System Fault – 7 minutes
Uses diagrams to find a particular transformer in a URD system. Takes a voltage reading of a transformer’s secondary output. Explains, with a schematic diagram, how a blown fuse could cause a transformer to have no secondary output even though it is receiving primary power. Explains, with a diagram, how to de-energize a transformer without interrupting power to customers fed by other transformers in the circuit.
Isolating a URD Transformer – 9 minutes
Covers how to: use a primary schematic and a construction print (or similar system drawing) to find a tie point, make a tie, isolate a suspected faulty transformer, and test a transformer and its primary cables to make sure that they are de-energized.
Testing a URD Transformer – 7 minutes
Explains how to: safely remove a transformer fuse for testing, install a new fuse in a URD transformer, re-energize a URD transformer, and disconnect secondary cables.
Disconnecting a URD Transformer – 10 minutes
Covers how to: install grounds on primary cables, remove primary cables from a transformer, disconnect the neutrals and the case ground from a URD transformer, obtain information necessary to order a replacement URD transformer, and recognize various types of URD transformers.
Replacing a URD Transformer – 8 minutes
Explains how to: install a replacement URD transformer, test the replacement transformer for proper operation, restore transformers and cables on either side of the replacement transformer to their original conditions, and disconnect the tie point.