High Voltage Tester ETP-2
A high voltage tester is used for verifying the performance on field of electrical devices according to the specific requirements of the high voltage signal for each device; one of the main applications of a high voltage tester is checking the insulation that enables the device to operate with reliability and safety during its lifecycle; this is the case of the ETP-2, a high voltage tester which is specifically designed for the evaluation of the insulation condition in power transformers with oil/paper system.
The ETP-2, a high voltage tester for insulation resistance and recovery voltage analysis in power transformers
The ETP-2 is a high voltage tester that uses appropriate DC voltage levels with minimum risk for the winding, from 500 to 2000 Vdc; the main function is the analysis of the insulation condition on power and distribution transformers and autotransformers of any type with oil-paper dielectric.
The ETP-2 provides a fully guided and automatic software controlled test, with operator instructions during the execution and graphic representation of the results, an automatic system that avoids errors and provides a repeatability of the measurements to be able to study its evolution through an organized storage of results; it is a high voltage tester used by many utilities, workshops, manufacturers and testing companies, with an experience of more than 20 years on field.
Applying several DC voltage levels through different cycles in specific time intervals, and performing different electrical measurements and calculations, this high voltage tester get the following parameters:
- Recovery Voltage
- Insulation Resistance (temperature normalized or corrected)
- Time Constant
- Polarization index
The ETP-2 can detect problems such as contaminated insulation, paper and oil dielectric degradation or anomalous aging, and evaluates the overall condition of the oil/paper system.
The recovery voltage measurement (RVM) is the technique used by this high voltage tester for obtaining the polarization spectrum of the dielectric with information of dissolved humidity and components degradation; the high voltage tester shows graphically the evolution of the recovery voltage throughout the test, measured at the different cycles; the appearance and position of the maximum point are final indicative of the quality of the dielectric paper/oil, and the displacement of this curve peak is related with the existence of greater humidity and degradation of the dielectric; the ETP-2 is a high voltage tester that effectively completes the range of other insulation diagnosis methods, e.g. tan delta, partial discharge measurements, oil analysis, and so on.
Converting a high voltage tester into a diagnostic system and decision-making tool
The database storage of results and immediate reporting of this high voltage tester enables individual tracking of each transformer, which can be compared with previous results with optional trending and diagnosis software; the ETP-2 is part of ETP system for predictive power transformer maintenance, so that it can cross results with the other units to provide a complete diagnostic; more than just an individual measurement provided by any other high voltage tester, it is the evolution of the winding insulation status offered by the ETP-2 which provides the best information, with the integration of the results into databases for correlation and trending comparison.
The ETP Trends software provides a graphical view of all the results in the database from successive tests performed in the same transformer, establishing trends for each of the parameters considered. The ETP DiagHelp program estimates the status of the transformer, applying different diagnostic criteria to the calculations and measurements carried out by the ETP system.
In this way, this high voltage tester can detect when a transformer enters a risk zone and it is possible to schedule the most appropriate maintenance actions; the Diaghelp and Trends software packages complete the ETP-2, turning the high voltage tester into a results analysis system and decision-making tool.
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