Power factor test set

Data records

• The same instrument is used for transformer excitation current tests, which assess the magnetizing circuit, and with accessories for turns ratio and leakage reactance measurements and for testing capacitor bank units. Source: Doble product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.additional-transformer-tests
• Power factor test sets assess the insulation of transformers, bushings, circuit breakers, cables, surge arresters and rotating machines, in addition to the traditional power-frequency test offering a test at a frequency well below the power frequency that exposes problems hidden at line frequency. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.applications
• Capacitance is assessed before power factor, because an unexpected change in capacitance from the previous or factory value points to a wrong connection or a physical change in the apparatus. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.capacitance-check
• To reject the electrostatic interference present in an energized substation, the set generates its own clean test signal and measures at frequencies above and below the line frequency, so that the line-frequency interference does not enter the result. Source: Doble product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.interference-suppression
• A power factor test set applies an alternating test voltage to the insulation and measures the voltage, the current and the loss, from which it reports capacitance and the power factor or dissipation factor of the insulation. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.measures
• Power factor is the cosine of the angle between the applied voltage and the resulting current, and tan delta is the tangent of the dielectric loss angle, the complement of that angle; for the small loss angles of sound insulation the two values are almost equal and an instrument may display either. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.power-factor-and-tan-delta
• Power factor depends on insulation temperature, so results are corrected to a reference temperature before trending; generic correction tables have fallen out of use because the temperature dependence varies from unit to unit, and a set may instead derive an individual correction from a short frequency sweep. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.temperature-correction
• The test connections are configured as a grounded specimen test, where the current returns through ground, as a grounded specimen test with guard, where a guard lead diverts unwanted current paths from the measurement, or as an ungrounded specimen test, where the measuring lead goes to an ungrounded terminal so that only the insulation between the two leads is measured. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.test-modes
• A tip-up test repeats the measurement at several voltage levels; ideal insulation gives the same power factor at every level, so a power factor that rises with voltage indicates deteriorated insulation, and a set may flag voltage dependence from the harmonic content of the measured signal. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.power-factor-test-set.tip-up-test