TEVKO

Electrical tests

Diagnostic electrical testing for transformers and substations

Each test isolates a different failure mode. We run them with Omicron and Megger instrumentation, correct for temperature and deliver a protocol compared against standards and asset history.

Transformer turns ratio test (TTR)

Verifies the turns ratio between high- and low-voltage windings to detect shorted turns, tap-changer faults and connection errors.

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Insulation power factor and Tan Delta

Measurement of dielectric losses in transformer and bushing insulation to detect moisture, contamination and paper-oil ageing before they cause failure.

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Insulation resistance and polarization index

Measurement of insulation resistance with a megohmmeter and calculation of absorption and polarization indices to assess moisture and cleanliness of the dielectric system.

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Dissolved gas analysis in oil (DGA)

Chromatography of the insulating oil to detect incipient faults — arcing, partial discharge and hot spots — from the gases dissolved in the oil, without de-energizing the transformer.

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Sweep frequency response analysis (SFRA)

SFRA test that detects mechanical deformation and displacement of windings and core — invisible to conventional electrical tests — after short circuits, transport or earthquakes.

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Transformer winding resistance test

Measurement of the DC resistance of windings to detect loose connections, broken strands and bad tap-changer contacts.

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Transformer excitation current test

Measurement of the no-load current the transformer draws to detect shorted turns, core defects and tap-changer faults.

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Physicochemical oil analysis

Battery of physical and chemical tests on transformer oil to assess its condition and decide reconditioning, regeneration or replacement.

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Moisture in oil (Karl Fischer)

Measurement of water content in transformer oil by Karl Fischer titration — moisture is one of the main accelerators of insulation ageing.

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Furan analysis (paper ageing)

Measurement of furanic compounds in oil to estimate the ageing of the solid insulation (paper) — the part of a transformer that cannot be renewed.

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PCB (askarel) content in oil

Testing transformer oil for polychlorinated biphenyls (PCB / askarel) — a regulatory and environmental compliance requirement before servicing or disposal.

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Ground (earthing) system measurement

Measurement of the resistance and integrity of a substation grounding system to ensure personnel safety and correct protection operation.

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SF6 circuit breaker testing

Testing of SF6 high-voltage circuit breakers: gas quality, contact resistance, timing and mechanism, to ensure reliable interruption.

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