Doble DTA System

Doble Test Assistant:
From Field Test to Office Action

Doble Test Assistant^® (DTA) is an amazingly adept way to test and analyze the condition of your power-system apparatus. Here's what you need to know in order to unlock its potential as a virtual expert guide. This briefing is going to walk you through its features, functions, and business value. You'll see how DTA's two modules, Field and Office, go beyond raw numbers to deliver real answers for on-site technicians, engineers, and management.

In one year, an insurance group reported 25 substation transformer failures costing over $100,000 each. That news gets worse: At a nuclear power plant, a transformer failed in “an eventful mode.” Translation: The resulting substation fire caused weeks of production downtime. The estimated loss of revenue was $1 million a day.

The long-term prognosis is even more dismal. A study by another insurance group indicates the operational life cycle of transformers is decreasing. They found deteriorating insulation was causing failures in equipment that had been in service an average of just 17.8 years. Yet another major insurance group predicts substation transformer failures will rise by 500% within 10 years.

Adding to today’s challenges in testing, statistical failure analysis shows there is a range of possible reasons causing transformer failures. These include abnormal operating conditions, over-voltages, system short-circuits, abnormal operations, improper maintenance, substandard materials, substandard manufacturing techniques, and design deficiencies.

For beleaguered asset managers trying to cope with these issues, the old rules of thumb are proving less and less effective. The best strategy is to focus on data that is first and foremost statistically significant. Therein lies the rub.

Suppose you have a transformer with an unusual test result. How can you be certain of your diagnosis, when all you have to work with are limited number of test results from a handful of similar transformers in your inventory? In all likelihood, you won't have a "statistically significant" sample for guidance

This is where Doble Test Assistant plays a critical and decisive role. Doble has that needed breadth of data. The DTA Expert System includes knowledge gained from millions of test results that were collected from hundreds of Doble clients over many years.

DTA in a nutshell is an easy-to-use "smart" software system, designed for use by apparatus maintenance, operations, and management teams. Once DTA is on the scene, the test technician is on the fast track to having knowledge based on statistically significant data.

The data record for an apparatus—a transformer with tertiary—centers on the nameplate. All attached equipment, such as bushings (mouse over) are part of the single apparatus record.

The process starts with the DTA Field Test module, with its many testing capabilities and its ability to analyze each test result. DTA's Field System module collects and processes test data. Later, the DTA Office module takes all of the test results from the Field System and incorporates that data into your company's DTA database for planning and analysis.

From the get-go, DTA makes it easy for technicians to build a useful and significant collection of test results. By enforcing strict data formats and naming conventions, DTA sets up a uniform framework that assures that all apparatus types, accessories, test plans, and test results can be accessed and analyzed universally.

To make it easy to comply with these rules when testing in the field, the DTA user interface has drop-down menus and pick lists. Automated electronic test plans reinforce standardized test methodology and test sequences for each apparatus type. In addition, DTA’s Field System automates calculations required for older manual instruments.

For example, DTA applies a temperature correction factor for accurate comparison of test results, regardless of the ambient temperature when the tests were run.

When examining the test data for the transformer, the DTA expert system module can be invoked (mouse over) to provide help in the analysis of the data and recommended courses of action needed to be taken.

What’s more, the user receives a highly dependable conclusion about the condition of apparatus insulation, based on norms established by thousands of test results. DTA even tells the test technician about next steps, once the facts are in.

Once a questionable or unacceptable test result turns up, the DTA Field System lists recommended follow-up investigative procedures. DTA is recognized for its unique analysis, leveraging an expert system that incorporates over 3,700 rules derived from more than 10 million tests from Doble’s master database. In effect, the DTA Field System provides the virtual presence of an engineering guide with over 80 years’ experience.

That vast library of information continues to grow. Each year, thousands more test results are added to the master Doble Database, from which norms, rules, and expert help are formulated. Virtually no problem “stumps” the system.

From Field to Office,
DTA Power Multiplies

With DTA Office, engineering managers can query their database to reveal trends and distributions in their own data. If that sample is too limited, they can request Doble to query the entire master database for a particular apparatus. In this case, a particular transformer has over 5,200 valid data points.

DTA’s Office module provides a database into which all of the DTA Field data is loaded. In this database, records are structured by apparatus. The apparatus nameplate and all of the test history for the apparatus are located in one record. This provides ease of access for analysis, reporting, and maintenance scheduling.

Using DTA Office, engineering managers can compare multiple tests over a period of time to distinguish emerging trends. Reports can be run on specific test results or the location of equipment.

This information supports proactive guidance of maintenance operations. More importantly, managers can minimize unplanned outages and maximize utility profits. This is where DTA literally pays.

While rules based on thousands of tests are necessary to diagnose an apparatus problem, rules alone are not sufficient to analyze a trend in multiple assets.

DTA SNAPSHOT

Q: How long has DTA been in use?
DTA has been in use for 14 years. It was first released on March 4, 1991.

Q: What are the latest versions of DTA?
DTA Field Version 5.1
DTA Office Version 4.3

Q: How do I get the new version?
All user companies may access updates via Doble’s web site. Contact your client service engineer for a password.

Q: What makes DTA unique?

Uniform test methods and measurements
Data produced in a controlled manner by Doble’s test equipment
Rigorous rules for formats and naming
Information easily compared against similar information from within the company
Information comparable against results from similar tests from other companies
Best-practice gains, via work with statistically larger, more viable samples

When results differ dramatically and your data is limited, how do you distinguish a trend from an aberration? To accomplish this task, access to a very large data sample is vital for any analysis to be statistically significant.

DTA is just as essential for the asset manager performing a trend analysis as it is for the field technician diagnosing an equipment problem. As part of the Doble Services Program, clients can ask their Doble Client Service Engineers to make queries on the master database, with its repository of results from over 10 million tests.

With DTA, engineering managers concerned about the way an apparatus is behaving can rest assured that an answer based on significant real-world data will always be readily available.

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