Tan Delta Diagnostics TD Series

As a simple and highly effective method to assess the dielectric condition of medium voltage cables, tangent delta measurement is the method to detect treeing in the insulation.


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TD Series Cable Diagnostic System used for tan delta measurement. While partial discharge measurement is suitable for detecting electrical trees, tangent delta measurement – also referred to as dissipation factor measurement – detects water treeswhich have formed in the insulation of the device under test. The data collected is compared to measurement values from the same cable taken during the acceptance test. That allows classification of the dielectric condition (new, strongly aged, faulty) of the cable.

The weight-optimized cable diagnostics systems are compact and designed for mobile use. As with VLF cable testing a sinusoidal 0.1 Hz VLF (very low frequency) AC test voltage is used. To measure the dissipation factor tan δ, voltages up to twice the nominal voltage (2.0 U0) are required. Therefore, there are two models in the TD series offering 2 voltage ranges – 33 kV peak and 62 kV peak. These ultra precise cable diagnosis systems measure the dissipation factor with an accuracyof ± 10-⁴ for loads in the range of 15 nF to 5 μF.

Fields of application

Tangent delta measurement is compatible with medium voltage cables with various insulation types, such

  • XLPE
  • PE
  • EPR
  • PILC

Furthermore capacitors, switchgear, transformers and rotating machines can be tested.

Reporting and display

The PC-based software-tool TD Control Center offers functions for analysis, storage and display of the measurement process. During the tangent delta measurement, output voltage and current are transferred in real time to the PC-software via the Bluetooth™ interface.
The tangent delta graph shows measurement values of the dissipation factor tan δ with respect to the selected output voltage test points.
During the test procedure, a diagnosis report containing all measurement values is created, suitable for storage or direct printing.