Distribution Transformer Test
Distribution Transformer Test
(OP)
Is there a way to test distribution transformers for winding faults using a meter or a thumper(Hi-pot) device? Our linemen typically test for winding faults by inserting a smaller sized fuse, re-energizing the transformer, and waiting to see if the fuse will hold. The problem is, with our emphasis on power quality these days, If the fuse does not hold there is a draw down of voltage on our system. So we are wondering what is done on other systems to verify the windings of a transformer before energizing.
Any help or suggetsions are greatly appreciated.
Any help or suggetsions are greatly appreciated.






RE: Distribution Transformer Test
(1) DC-insulation resistance between windings and each winding to core/can, and (2) turns-ratio test between the windings will give a reasonable assay of transformer condition. Some TTR sets will also display relative excitation current.
RE: Distribution Transformer Test
A good reason to use a 30' hotstick to close the cutout while re-fusing.
A smaller size fuse may also blow on inrush even if there is no fault. One of the criteria for sizing transformer fuses is to make sure it is large enough to withstand inrush.
RE: Distribution Transformer Test
Thanks Again.
Happiness is a way of travel, not a destination.
RE: Distribution Transformer Test
Given the equipment value and the cost of lost production/revenue in the case of 750kVA, a better “checklist” may be §7.2.2 NETA 2001 Maintenance Testing Specs for liquid-filled transformers, or ANSI/NETA Standard MTS 7.2.2 Standard for Maintenance Testing of Liquid-Filled Transformers. from netaworld.org.
RE: Distribution Transformer Test
A falut large enough to blow a fuse must be detectable trough:
- Insulation resistance (usually refered as megger)
- Turn ratio (usually refered as TTR)
- Winding resistance
- Also you may test the oil dielectric strength.
A good guide for performing test in the field is IEEE Std 62-1995 "IEEE Guide for Diagnostic Field Testing of Electric Power Apparatus - Part 1: Oil Filled Power Transformers, Regulators and Reactors."
RE: Distribution Transformer Test
RE: Distribution Transformer Test
http://www.sandc.com/products/faulttamer/default.asp
Jes
RE: Distribution Transformer Test
RE: Distribution Transformer Test