On-site testing of high-voltage equipment

Decoupling of partial discharge signals in the connection of the earth screen of a busbar of a generator busduct

FKH offers insulation diagnoses and other electrical tests on all high-voltage electrical equipment. In addition to diagnoses on transformers and rotating machinery, there is a particular focus on condition analyses for measuring transducers, switchgears and entire switch panels, lightning arrestors, bushings and insulated busbars.

FKH offers simple voltage tests with AC voltage, surge voltage and DC voltage, as well as diagnostic measurements under AC voltage, partial discharge measurements, dissipation factor measurements and other dielectric measurement methods to analyse the polarisation properties of the insulation medium. FKH advises its customers on selecting the most economical and informative test procedures. The measurement results are accompanied by an assessment with recommendations for any measures that may need to be implemented on the electrical equipment.

Insulation tests may be required for quality checks in connection with procurement procedures. In many cases, grid operators commission FKH to carry out condition analyses on service-aged components. These may be triggered by an accumulation of failures or by the need to decide between continued operation or replacement of older components in switchgears.

Meaningful results can be obtained from analyses of oil-cellulose insulation, cast resin-mineral insulation and mixed insulation. On the basis of these results, it is possible to determine whether the insulation of the electrical equipment still corresponds to the condition when new, whether maintenance measures are required, or whether operational safety can no longer be guaranteed on account of the condition of the insulation. A relevant factor for this assessment is usually tolerance for minor fault locations in the insulation that can be identified and quantified. Their criticality differs greatly due to the extensive range of insulation types that are now available. Ageing and self-healing mechanisms in the insulation medium are decisive factors. Self-healing mechanisms are more commonly found in organic composite insulation systems consisting of fluid and solid components than in purely solid insulation systems.

The ageing mechanisms for insulation are considered on the basis of FKH’s lengthy experience of interpreting diagnostic results and on recommendations that have been issued.

Phase-resolved pulse statistics for a partial discharge source in an aged busbar