Among all the components of the transformer, the on load tap changer is the only mechanical component that continuously operates in operation. Its task is to adjust the transformer ratio by switching the winding tap under load, thereby stabilizing the grid voltage. Because it needs to operate repeatedly in high current environments, the probability of wear and failure is much higher than other components.

Why do we need to specifically test on load tap changers

The National Preventive Testing Regulations for Power Equipment clearly require that after major repairs of transformers and maintenance of on load tap changers, the sequence of switch actions must be checked, and parameters such as switching time must be measured. But this test cannot be achieved through manual judgment and simple measurement tools - the switching process of the on load tap changer is only a few tens of milliseconds, the transition resistor is only connected for a few tens of milliseconds before exiting, and the eyes and hands cannot keep up at all. Only specialized instruments can capture the complete details of this process.

What can HZYA-3Z measure

HZYA-3Z can simultaneously obtain the following parameters in one test:

Transition waveform: fully record the resistance change curve of the entire switching process

Transition time (T1/T2/T3/T4): running time of transition resistor 1, bridging time, running time of transition resistor 2, total transition time

Transition resistance value (R1/R2): The actual resistance value of two transition resistors

Three phase synchronicity (T0): time difference of three-phase switching action

Coil resistance (R0): The DC resistance of the winding itself

These parameters combined can comprehensively reflect the mechanical status, contact status, and electrical performance of the on load tap changer, and are the direct basis for determining whether the switch needs maintenance.

The essential difference between direct current resistance method and direct current resistance method

The traditional method of measuring step by step with a DC resistance meter can only determine whether the contact of each gear is normal, and cannot capture the dynamic characteristics during the switching process. HZYA-3Z samples at a high speed of 20kHz at the moment of switch switching, accurately reproducing the entire switching process and discovering hidden dangers such as spring aging and abnormal transition resistance that cannot be seen by traditional methods.