The ultra-low frequency high-voltage generator combines modern digital frequency conversion technology and is controlled by a microcomputer. The rise and fall of voltage, measurement, protection are all fully automated. Due to its fully electronic design, the ultra-low frequency high-voltage generator is small in size, light in weight, has a large-screen liquid crystal display, which is clear and intuitive, and can display the output waveform and print the test report. The design indicators of the ultra-low frequency high-voltage generator fully comply with the “General Technical Conditions for Special Testing Instruments for Electric Power Equipment, Part 4: General Technical Conditions for Ultra-Low Frequency High-Voltage Generators” of the power industry standard. It is very convenient to use.
The ultra-low frequency high-voltage generator is widely applicable in the ultra-low frequency insulation withstand tests of wires and cables and large-scale high-voltage rotating generators. The operation method of the ultra-low frequency high-voltage generator for the withstand test of generators is as follows:
During commissioning, major overhauls, partial replacement of windings, and routine tests, this test can be carried out. Using a 0.1Hz ultra-low frequency high-voltage generator to conduct withstand tests on motors, the defects of the insulation at the generator end are more effective than the withstand tests at 50Hz.
The reason is that under 50Hz voltage, the capacitive current flowing out from the stator coil causes a large voltage drop when flowing through the semiconductor anti-halo layer outside the insulation, thus reducing the voltage borne by the insulation of the end of the stator coil;
However, in the ultra-low frequency situation, this capacitive current is greatly reduced, and the voltage drop on the semiconductor anti-halo layer is also greatly reduced, so the voltage on the insulation at the end is higher, making it easier to detect defects.
Connection method: During the test, it should be carried out phase by phase. The tested phase is subjected to pressure, and the non-tested phase is short-circuited and grounded.
According to the requirements of relevant regulations, the peak value of the test voltage can be determined by the following formula: Umax = √2βKU0
Where Umax: Peak value of the 0.1Hz test voltage (KV)
β: Equivalent coefficient of 0.1Hz and 80Hz voltages, according to the requirements of our national regulations, take 1.2
K: Usually take 1.3 to 1.5. Generally take 1.5
UO: Rated voltage of the generator stator winding (KV)
For example: For a generator with a rated voltage of 13.8KV, the calculation method for the peak value of the ultra-low frequency test voltage is:
Umax = √2×1.2×1.5×13.8 ≈ 35.1 (KV)
The test time should be carried out according to relevant regulations
During the withstand test of the generator with the ultra-low frequency high-voltage generator, if there are no abnormal sounds, odors, smoke, or unstable data display, it can be considered that the insulation has withstood the test. To better understand the insulation condition, it is necessary to monitor the surface condition of the insulation as comprehensively as possible, especially for air-cooled units. Experience indicates that appearance monitoring can detect abnormal phenomena of generator insulation that cannot be reflected by the instrument, such as surface corona and discharge.
Post time: Aug-12-2026