URD Transformers

Verifying the Power Outage Use diagrams to locate the transformer(s) that feeds houses reporting a power outage. Determine if houses reporting power outages are actually not getting power. Determine if a problem in the primary circuit is the cause of the power outage. Identifying a URD System Fault Use diagrams to find a particular transformer in an underground residential distribution (URD) system. Take a voltage reading of a transformers secondary output. Explain with a schematic diagram how a blown fuse can cause a transformer to have no secondary output even though it is receiving primary power. Explain 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 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. Test a transformer and its primary cables to make sure that they are de-energized. Testing a URD Transformer Safely remove a transformer fuse for testing. Install a new fuse in a URD transformer. Re-energize a URD transformer. Disconnect secondary cables. Disconnecting a URD Transformer 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. Recognize various types of URD transformers. Replacing URD Transformer 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. Disconnect the tie point.