HV and EHV Testing Laboratory

A necessary condition for the reliable and safe operation of power equipment, particularly high voltage equipment, transformers, and generators, is the good condition of their electrical insulation system. This condition is determined by the characteristics of both the solid insulation and the insulating oil. Through regular diagnostic monitoring of these parameters and considering the equipment’s operational life data, a specialised facility can not only assess the current condition of the electrical insulation system but also recommend measures, propose preventive actions, and provide a well-founded estimate of future operational reliability and lifespan. Underestimating or even neglecting diagnostics by power equipment operators can lead to severe failure scenarios, endangering lives and health, causing significant environmental damage, and, not least, resulting in power outages with subsequent economic losses. Timely and thorough diagnostics of power equipment’s operational condition is often a prerequisite for securing insurance contracts between power equipment operators and insurance companies.

The testing laboratory provides:

• Diagnostics of the insulation systems of electrical rotating machines (hydro generators, turbo generators, high voltage motors)
• Diagnostics of the insulation systems of electrical non-rotating machines (power and instrument transformers, bushings)
• Testing of circuit breakers and surge arresters
• Testing of inter-turn insulation with current impulses (Baker test)
• Diagnostics of power equipment filled with SF6 gas
• Diagnostics of the insulation properties of circuit breakers
• Measurement of partial discharges in rotating machines
• Detection of partial discharges using a corona camera
• Measurement of frequency response characteristics of transformers (FRA) to assess potential internal winding deformation
• Diagnostics of internal winding deformation
• Dielectric spectroscopy in the frequency domain (IDAX) and determination of moisture content in transformer paper insulation
• Chromatographic analysis of gases dissolved in electrical insulating fluids
• Vibration testing of drives, particularly in water turbines and hydro generators
• Measurements using thermal imaging
• Ozone detection
• Testing of work and protective equipment
• High voltage testing (mobile voltage source up to 350 kV / 1A DC and AC)
• Specialised on-site measurements using extra high voltage (EHV), high voltage (HV), and low voltage (LV) measuring equipment
• Consulting services in the aforementioned areas

The testing laboratory also operates a specialised chemical analysis unit, which provides the following support analyses for electrical insulating fluids by determining:

• Breakdown voltage values of liquid insulants at mains frequency
• Water content in insulating oil
• Acid number of mineral insulating oils
• Density of mineral insulating oils
• Interfacial tension between oil and water
• Temperature dependence of the dissipation factor, relative permittivity, and internal resistivity under direct current voltage
• Content of gases dissolved in mineral insulating oil, including total gas content
• Sludge insoluble in n-heptane
• Particle count and size in insulating fluids using a particle counter
• Thermal-oxidative stability (TOS) of mineral insulating oils
  Presence of corrosive sulphur (qualitative and quantitative, including testing for DBDS)
• Inhibitor content
• Passivator content in mineral oils using HPLC
• PCB (polychlorinated biphenyls) content in mineral oils using gas chromatography
• And by conducting laboratory regeneration of insulating fluids

For solid insulation, it also determines:

• Water content in solid insulation
• DP (average degree of polymerisation) value
• Presence of furanic compounds released from solid paper insulation into the oil