Composition and Features of the Device A typical triple-frequency test device usually includes: Triple-frequency power generator (core component, compact in size). Single-phase voltage regulator (for adjusting input). Test transformer (if higher output voltage is required, a high-voltage test transformer may be connected in series, but in many cases, the triple-frequency generator's direct output is sufficient for PT testing). Control and protection box. Features: Small size and light weight: Compared with power-frequency test transformers of the same capacity, the triple-frequency device is lighter and more portable, suitable for on-site movement. Good waveform: The output waveform is close to a sine wave with low distortion. Safety: Equipped with comprehensive overcurrent, zero-position start, and timing protection functions. 6. Standards followed: GB 50150-2016 "Standard for Hand-over Test of Electric Equipment in Electrical Equipment Installation Engineering" DL/T 596-2021 "Regulations for Preventive Tests of Power Equipment" GB 1094.3 "Power Transformers - Part 3: Insulation Levels, Insulation Tests and External Clearances in Air" IEC 60076-3 (Power transformers - Part 3: Insulation levels, dielectric tests and external clearances) 7. Operation precautions: Grounding: The device enclosure and the non-pressurized end of the tested equipment must be reliably grounded. Wiring check: The input and output wiring of the triple-frequency generator has strict phase requirements; incorrect connection may result in no output or equipment damage. Capacitive rise effect: For long cables or high-capacitance test objects (although triple-frequency is mainly used for inductive loads, if capacitive loads are present), attention should be paid to voltage rise; the voltage should be measured directly on the high-voltage side (using a voltage divider or high-voltage meter). Time control: Strictly control the pressurization time; excessive time may cause insulation overheating damage, while too short a time may render the test invalid. Discharge: After the test, the test object must be fully discharged. 8. Difference from "variable frequency series resonance": Triple-frequency generator: Fixed output at 150Hz, mainly used for induced voltage withstand tests on inductive loads such as transformers and PTs, solving the problem of core saturation. Variable frequency series resonance device: Frequency adjustable (30-300Hz), mainly used for AC withstand voltage tests on cables, GIS, generators, and other capacitive or high-capacitance loads, utilizing the resonance principle to reduce power supply capacity.
