The ETP SYSTEM is a complete predictive maintenance instrument to detect the problems before unexpected failures appear in power transformers, autotransformers, and instrument transformers, reducing non-programmed shutdowns, transport, and catastrophic costs.

The predictive and condition based maintenance is nowadays accepted as the most efficient solution to guarantee the proper operation of critical assets. In both electrical power generation, T & D and industry applications, power transformers are essential and require the right maintenance policy.

Due to the high cost of the on-line monitoring systems and the need of performing scheduled shutdowns for other different reasons as mechanical revisions, the off-line tests provide a cost- efficient, safe way to proper transformer maintenance.


The ETP system will guide the operator with messages on the computer's screen, while an exhaustive set of measurements is performed on the analyzed transformer. Three-phase connection instructions are displayed, as well as wait messages while the secondary windings are discharged automatically.

Each transformer's technical parameters are saved into a database along with the results obtained during successive tests, in order to recall them in the future and to perform their evolution in the time.
 

Complete three-phase system

The ETP System is composed by four independent measurement modules controlled from a common measurement & analysis software in a PC. Diagnostics are performed by co-relating the measurements done by each module:

• Turns Ratio: three-phase measurement of the turns ratio and the excitation current in ever y position of the tap changer. Results are compared with the theoretical values and the error is shown graphically.
• Recovery Voltage: evaluation of the solid and liquid insulation condition through electrical measurements.
• Winding Resistance: three-phase measurement of the resistance values in every winding and for every position of the tap changer.
• Short-circuit Impedance: evaluation at low voltage of the short-circuit impedance and voltage.

The above measurements are used to evaluate the condition and then predict possible failures at the four main circuits in a transformer:

• Electrical Circuit: checking the continuity of the windings, the connections and the tap changer.
• Geometrical Circuit: checking the symmetry between the columns of the core, between the windings and the core and between these and the transformer's enclosure.
• Magnetic Circuit: checking the condition of the magnetic core (loose plates, short-circuits, detachment of the magnetic shunt, etc.).
• Dielectric Circuit: checking the degradation and the ageing of the solid and liquid insulation.

Testing is a simple, automatic and fully software-guided task. The operation is divided into to main steps: 1) Measurement, wich guides the operator to the connections and wait operations, eliminating human errors and ensuring repeatability, and 2) Analysis, by immediately displaying the measured values on the screen as they are acquired by the software. The information can be immediately converted into a complete report and interpreted by an expert to determine whether maintenance operations should be planned or not.

ETP Trends software will produce an evolutive view of the transformer’s condition by collecting results from successive tests within any two dates.

ETP Diaghelp will apply an expert algorithm to the test results to provide a direct, concise diagnostic of the transformer including alerts, warnings and ser vice recommendations.

The Power Socket is a plug base equipped with a series of protection and indication circuits that make it an ideal accessory for use as a complement to ETP measuring units.

Thanks to the Power Socket, the operator may provide grounding when this is not incorporated in the installation, and also has at his disposal a mains disconnect circuit breaker close to the equipment for the performance of any interventions or for possible hazardous conditions, as well as voltage presence and level indicators and the aforementioned ground detection device. It also includes a power line filter and surge protector in order to minimize possible damage to the units supplied and increase the immunity to conduced interference.