The PHENIX Technologies model FRA-100 Frequency Response Analysis test system is a portable, off-line system designed to detect winding movements resulting from shipping damage, subjection to low impedance through faults, or general looseness of clamping structures brought on by the normal effects of aging, in distribution and power transformers. The technology used in this highly sophisticated diagnostic tool was developed in the United States by the National Electric Energy Testing, Research and Applications Center (NEETRAC), a center of Georgia Institute of Technology. PHENIX Technologies and NEETRAC have teamed together to bring this powerful testing technique to the electric power industry.

Software Analysis and Data Management Package.
The FRA-100 software package is a Windows based application that provides both testing control as well as data management functions.

Upon selecting the type of transformer from a list of standard single phase, three phase and auto connections, the software provides prompts to the user to connect the leads and initiate each sequence of impulses. Built in safety checks will prompt the user if there is a problem with the lead connection that is recognized by the computer, based on the data collected.

In addition, on three phase transformers the test technician can select whether or not he or she wants to perform an OWA test on the transformer. The OWA test is recommended on all three phase transformers even if a comparison to historical data is also desired. The OWA test has been shown to be generally the most sensitive to actual mechanical changes in the winding geometry, while at the same time looking over changes that commonly affect all three phases, resulting from temperature differences, oil condition, etc.

The data management portion of the software provides for convenient storage and retrieval of test records, allowing the comparison of both WND results and OWA results on any two transformer test records that are selected. This allows comparison between historical data and present data, as well as comparison with the frequency response of sister units if it is desired to make this comparison.

A test report can be generated and stored that provides the results of the comparison of any two test records selected, and that provides written application guidelines that prompt the test technician about possible reasons for the results obtained, based on the type of transformer and the results encountered. The guidelines are based on the extensive development investigations performed during the development of the FRA-100 test system, and provide valuable insight into the results. Additionally, the software generates a Green/Yellow/Red condition assessment as an immediate visual indication to the test technician of whether a significant change exists between frequency responses under comparison. This visual condition assessment can be used as the basis in deciding whether additional electrical tests or internal visual inspections should be made on the transformer before approving it to be energized in service.

Impulse Source.
An internal 300 V impulse source provides the exciting impulses required for the FRA test. The pulse source is automatically controlled by the PC, with all pulse application and data collection being managed by the test computer, following an initiation command by the test technician to acknowledge that the test leads have been connected to the proper terminals of the transformer, and that all personnel are clear of the test leads.

For each connection configuration, the PC will collect data from a series of ten applied impulses. Each impulse is of approximately 300 V magnitude, with a steep rise time on the order of a few hundred nanoseconds, and a variable time to chop that is controlled by the test set computer that ranges over a time interval of approximately 10 to 90 microseconds during the series of 10 applied impulses.