Solutions for Power Transformer Testing
Power transformers are subject to several electrical, mechanical, thermal, and environmental stresses during regular operation, with an expected life cycle of more than 30 years; it is important to know the status and evolution of the transformer along its life, whether it is in condition to continue operation with the maximum security or requires any repair, maintenance or even take it out from service; therefore, utilities and service companies schedule power transformer testing plans to assess their condition, increase its service life, and provide safe and trouble-free operation.
The need of integrated and optimized solutions for power transformer testing
Due to the short downtime available, power transformer testing during a maintenance program should be optimized for maximum automation of tests and minimize the testing time; this requires to establish also a short and sufficient number of electrical tests for determining the state of the transformer and tracking its evolution; accordingly, and in line with the predictive maintenance, testing of the power transformer should provide the early detection of the real problem to perform the required actions; this is only possible with the existence of a common database with all the tests performed in the same transformer, for optimizing the diagnosis and trending analysis that allows a predictive monitoring of faults.
The predictive testing can be an effective first step in the maintenance system if the tests results of different parameters are crossed to analyze the different sources of the aging problems; there are in the market testing equipment for power transformers which work as separated units, but not usually integrated into a unique diagnosis system and linked to a diagnostic software; this is the spirit of the ETP System, an integrated solution for power transformer testing that reduces the test time and the expenses; the ETP System merge the different power testing results for effective trending analysis that allows to properly schedule any future maintenance work.
The ETP, a system for predictive maintenance
The ETP is an integrated 3-phase power transformer testing system that evaluates and detects most of the common failures at the four main circuits of the power transformer, electrical, geometrical, magnetic and dielectric circuit. The ETP System has four independent modules controlled from PC, which can also be used separately for power transformer testing; trending and diagnostics are performed by expert software which confirms the existence of problems by evolution and correlation of the measurements done by each module.
The ETP System is oriented and deeply proved for testing on the field, with a quick and fully guided software system, which avoids the need to perform calculations and reduce the human errors with instructions to the operator; the measurements are unified in a common database for transformer trending analysis, with graphic representations of the results for each tap position.
With the same cables, for minimum connection work, the ETP System performs an integrated power transformer testing, in less than 2 hours, to characterize the transformer with the following electrical tests which are sufficient for defining the state of the transformer completely:
- Three Phase Turns ratio/ excitation current (ETP-1)
- Recovery voltage/insulation resistance/ polarization index (ETP-2)
- Three Phase Windings resistance measurement (ETP-3)
- Three Phase Short circuit impedance measurement (ETP-4)
The ETP Trends software has been designed for tracking the evolution over time of transformers tested with the ETP system, being possible to identify anomalies on the transformer lifetime, and preventing that it enters in a risky zone observing the evolution of the power transformer testing parameters showed in the ETP Trends graphics; in this way we will know when any intervention should be performed and solve the problem in its incipient phase.
The ETP Diaghelp program is an expert software for transformer diagnosis, that applies several diagnostic criteria – based on standards and long and proven experience in the field – to the whole power transformer testing files generated with the ETP system, providing an indication of the existing problem and its severity; the DiagHelp analyze the results from any of the saved tests, detects the problems in the different circuits of the transformer, and displays a chart with the corresponding indicators, alerts and recommendations.
Other SMC products for power transformer testing
The Raptor System includes test templates for instrument transformer testing and also for power transformer testing in single phase, such as PT ratio, withstand voltage, shortcircuit impedance tests and power factor.
The PME-20-PH is a digital phase angle meter that provides phase deviation on power and metering transformers, with quick phase angle measurement between two voltages, two currents or between current and voltage; includes also the measurement of frequency and power factor.