For many years, dissolved gas analysis and fluid quality testing have been used as diagnostic tools for transformers. By far, the most widely accepted standards for transformer fluid testing and interpretation in the last decade have been the 1991 revision of the IEEE guides, C57.104 and C57.106. TJ/H2b Analytical Services has used the knowledge gained from the application of these guides as a foundation for the development of enhanced diagnostics. In particular, TJ/H2b has developed diagnostic enhancements that include:

  • Expanding the number of fluid assessment tests
  • Updating pass/fail fluid assessment limits for newer maintenance philosophies
  • Trending the relationships for fluid data
  • Analyzing the relationships between fluid and gas data
  • Trending gas-in-oil data beyond two tests
  • Relating gas-in-oil data to phenomena in the transformer
  • Assessing solid insulation condition
  • Considering the relationship of these data to operation, system events, or maintenance activities

In 1997, TJ/H2b began to look at fluid testing possibilities that would provide the capabilities required for upgraded transformer maintenance programs.The ability to use transformers up to their maximum safe loading capabilities is essential to optimizing their use. Necessarily, obtaining the optimal use of transformers changes the approach to maintenance. The major critical asset components of a transformer, the paper, windings and core were not designed to be maintained in the same manner as the components of tap changers or breakers. In a manner analogous to human health care, a combination of preventive practices, prudent operating practices, treatments and repairs are needed. Management of the asset requires the best use of these alternatives and this, in turn, requires the appropriate condition assessment tools.

Transformer Condition Assessment, TCA® has been developed to provide the information for management of the oil condition, management of the paper condition, and the identification of the problems such as core lamination problems, core ground problems, no load tap changer problems, terminal and connector problems.

 

A Transformer Case History
The case below demonstrates the capability to identify fault location
Dissolved Gas Analysis Test 1 Test 2
Hydrogen
3246
4098
Methane
15941
21396
Ethane
4115
4860
Ethylene
27293
34664
Acetylene
168
247
Cardon Monoxide
187
251
Cardon Dioxide
6299
8158
Nitrogen
52053
59960
Oxygen
3927
1809
Particle Profile
5 to 15 um
9275
144800
15 to 25 um
1685
17450
25 to 50 um
780
3725
50 to 100um
140
170
> 100 um
15
10

TCA® gave a condition 4* and indicated severe heating, possible coking, and arcing at a connector or contact adjacent to but not directly in contact with paper. Internal inspection revealed a loose bolt on a load side bushing connector that had developed a large coke formation. This formation led to arching that had begun to deteriorate the connector.

The advantages of the Transformer Condition Assessment program can be summarized as follows:
  • Units that require maintenance are identified.
  • Units that do not currently require maintenance are identified.
  • Maintenance activities can be better focused.
  • Operators and planners can assess loading capabilities.
  • Failures can be reduced.
  • Reliability is enhanced.
  • Costs are reduced.
  • Safety is not compromised.

The TCA® Diagnostic Service is available exclusively at TJ/H2b Analytical Services.