Measurement of Tan Delta Capacitance of Winding and Capacitance (C1 & C2) for Bushings
The condition of the insulation is essential for secure and reliable operation of the transformer. Measuring capacitance and dissipation/power factor helps you to determine insulation condition in bushings or between windings. It is alternatively known as the loss angle test or the dissipation factor test.
Measurement of Low Voltage Excitation Current
Excitation current tests are used to detect: Shorted turn-to-turn insulation, Short circuited core laminations, Loosening of the core clamping, or Improper winding connections.
Transformer Short-Circuit Impedance Measurement
Short-circuit impedance variation is necessary for verifying the observance of the technical conditions (including the design conditions), certain nonconformities in the winding execution, checking the winding behavior in operation, verifying the system and short-circuit calculation (including the correct protection setup), the loading of the same type units, or more importantly, of the different type ones.
Winding Resistance Measurement
Winding resistances are tested in the field to check for loose connections, broken strands and high contact resistance in tap changers. Additionally, the dynamic resistance measurement enables an analysis of the transient switching operation of the diverter switch.
Frequency Response Analysis (FRA)
Short-circuit impedance variation is necessary for verifying the observance of the technical conditions (including the design conditions), certain nonconformities in the winding execution, checking the winding behavior in operation, verifying the system and short-circuit calculation (including the correct protection setup), the loading of the same type units, or more importantly, of the different type ones.
On-Load Tap Changer
Continuity Measurement (Ripple & Slope)
With advancing age, transformers require regular checks. Hence it becomes important to perform meaningful maintenance to avoid sudden and/or total failure. The state and health of on-load tap changers can successfully be assessed by performing static and dynamic winding resistance tests for each tap. Comparing the static winding resistance for each tap against the values measured at commissioning, the state of the selector as well as diverter contacts can be analyzed. The dynamic winding resistance test from one tap to the next yields a ripple and slope measurement, which will highlight any unwanted interruptions in the switching process of one tap to the next.
