Present comprehensive assessments power systems, required to check the trend of the parameters in teams involved in different industry applications with voltage levels of 220 V up to 115 kV.


The purpose of testing and Tangent Delta Tip-up is to evaluate the condition, quality, aging of insulation, as well as losses of isolates with frequency, in motors, generators, distribution transformers, power transformers, Insulators, electrical connections  and equipment in substation.


The diagnostic method of isolation Tangent Delta (tan .delta) expresses the dissipation factor and insulation power factor in percentage. This method measures the capacitance similarly separations insulation between the windings and windings to ground; capacitance depends mainly on the geometry of the windings of the electrical machine. The variations in capacitance are effectively indicative of motion and structural problems of the windings (displaced wedges, bending, etc.)


The development of these tests apply for equipment with voltage levels of 220 volts to more than 115kV.


Applicable to tests:








IME offers various predictive maintenance tests that allow you to diagnose the state of your equipment. The results will tell you when to schedule plans for preventive or corrective maintenance before serious failures occur.



Tangent Delta Test

Evaluate the condition, quality and aging of the insulation, as well as losses of isolates with frequency. The Tan δ expresses dissipation factor in percentage and measures the partial and total capacitance of the equipment.


Scope: Motors, Generators, Distribution Transformers, Power Transformers, Transformers Measurement, Insulators and equipment in substations.



Transformation Ratio Test (TTR)

To diagnose short circuit between turns of the winding, poor contact between the windings and the transformer terminals.

The voltage induced in each of the phases of the low voltage side of the three-phase or single-phase transformer (power and distribution) is measured, when an AC voltage is injected at a stage of high voltage side of the transformer. This is to verify that the transformation ratio automatically calculated by the computer is similar to the ratio specified in the data plate of the transformer.




Winding Resistance Test

To determine if there are irregularities due to loose connections, displacement or physical deformations in the windings, shorted windings, high resistance in Taps changer (if so in power and distribution transformers).


Scope: Distribution Transformers, Power Transformers, current transformers and potential transformers.




Insulation Resistance Test

To know the level of insulation between the windings and the various parts of electrical machines (power transformers, TP, TC, Motors and Generators) such as ground and core ones. Establish the state of isolation present in the transformer in case of moisture and possible contamination by elements such as dust or free polar particles in oil (for transformers immersed in oil). It should be noted that the isolation characteristics are not constant because they can deteriorate over time.


Scope: Distribution Transformers, Power Transformers, current transformers and potential transformers.




FRA Test


To evaluate the mechanical integrity of cores, windings and clamping structures of power transformers. Measuring electrical transfer functions over a wide frequency range.


The test is performed through the MIDAS TETTEX equipment, which uses the principle SFRA (Frequency Response Analysis Scanning) - proven worldwide for measurements in the frequency domain method. The SFRA is a comparative method, is an assessment of the transformer is done by comparing a set of results SFRA with the benchmark results.


Each grid has an answer in own unique frequency, the so-called fingerprint. Defects, mechanical shock (p. Ex., Earthquakes) or transport can cause deviations in the frequency response. Comparing measurements of different phases, sister units or the actual fingerprint with earlier measurements in the same transformer can detect electrical variations and position of the internal components.


We recommend testing the frequency response especially after the transport of transformers to site and after detecting faults with high currents to verify that the windings have not been damaged.


Scope: Power Transformers

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