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What is the short-circuit impedance of a transformer? What are the effects of transformer short-circuit impedance?

:2023-06-05 09:58:01:

Transformer short-circuit impedance, also known as impedance voltage, refers to the equivalent series impedance Zk=Rk+jXk between terminals in a pair of windings at rated frequency and reference temperature. Due to its value being determined through load testing in addition to calculation, it is commonly referred to as impedance voltage.

When the transformer is operating at full load, the short-circuit impedance level has a certain impact on the output voltage level of the secondary side. Low short-circuit impedance, low voltage drop, high short-circuit impedance, high voltage drop. When the load of the transformer is short circuited, the short-circuit impedance is small, the short-circuit current is large, and the power borne by the transformer is large. The short-circuit impedance is high, the short-circuit current is low, and the power borne by the transformer is small.

1. The higher the impedance voltage of the transformer, the smaller the short-circuit current flowing through the transformer during the secondary side short circuit, and the smaller the impact on the transformer. Therefore, the current owner requires a minimum short-circuit impedance value during the transformer manufacturing process, but increasing the transformer impedance voltage has higher requirements for the manufacturing process;

2. The larger the impedance voltage of the transformer, the greater the amplitude of voltage change on the load side of the transformer when the load changes, resulting in poor voltage stability;

3. The higher the impedance voltage of the transformer, the greater the reactive power consumed by the transformer winding under the same load.


The percentage of short-circuit impedance of a transformer is numerically equal to the mass percentage of the internal short-circuit protection voltage of the transformer. The percentage of the voltage applied by the primary winding to the rated output voltage level when a transformer is short circuited by the secondary winding and the secondary winding passes through the rated operating current of the system. The percentage of short-circuit impedance value of a transformer is an important parameter that reflects the internal impedance of the transformer, i.e. the impedance drop of the transformer itself when operating at rated load. The sudden short circuit on the secondary side of the transformer, the amount of short-circuit current that will be generated, the manufacturing price of the transformer, and the parallel operation of the transformer are also of great significance.

ZC-204B Transformer Short Circuit Impedance Tester is a specialized instrument for measuring low voltage short circuit impedance of transformers under on-site and laboratory conditions. The instrument comes with an adjustable power output, which is particularly suitable for on-site testing of 110kV and above main transformers. The instrument adopts phase-locked loop technology internally, synchronously sampling AC signals, and measuring data accurately.


Kvtester Electronics Technology Co.,Ltd. is a high-tech enterprise specializing in power testing, testing, research and development, production, and sales of testing equipment. It has been engaged in the electrical testing industry for many years, and its products are of high quality. We welcome customers to come and purchase.

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