How to test the temperature rise of transformer?
Writer： Hengfeng you electric Time：2023-03-29 views：times
The transformer test includes type test, routine test and special test, among which the temperature rise test is one of the type tests. This test is mainly to check the structural performance of the transformer, specifically to check whether the transformer can be cooled quickly, that is, to check whether the heat generated by the total loss can be dissipated quickly during the operation of the transformer, And whether it meets the top oil temperature rise of the transformer and the limited value of winding temperature rise specified in IEC standards. It is also necessary to check whether some other parts have local overheating, such as iron core, oil tank and structural parts. Since December 14, 2014, the temperature rise test of oil immersed transformer in China has implemented the Chinese national standard GB / t1094.2-2013 (iec60076-2:2011).
In the process of transformer test, temperature rise test is the most time-consuming test with the largest workload. At present, there are mainly methods to test the temperature rise of transformer: direct load method, mutual load method, circulating current method, zero sequence current method, short circuit method and so on. Among these methods, the short-circuit method requires the lowest test voltage and the smallest power capacity. Moreover, for oil immersed transformers, the national standard stipulates that the short-circuit method is the standard method of temperature rise test. Today, let's share with you how to carry out the temperature rise experiment of oil immersed transformer?
A. Oil immersed transformer short circuit method
Applied total loss
Firstly, short circuit the outgoing terminal of the low-voltage end of the tested transformer, apply total loss to the high-voltage end, and conduct the test after supplying power to the transformer. During the test, it is necessary to regularly monitor and record some temperature values, such as the temperature of the surrounding environment of the transformer, the temperature of the top oil layer and the temperature of the inlet and outlet of the radiator. The general time interval is half an hour and the test time is 3H. During the test, when the temperature rise change of the monitoring part is less than 1 ℃ per hour, the temperature rise is basically stable, We average the last 1H test value and take this value as the final result.
Apply rated current
The input current of the winding shall reach the rated current. After continuous monitoring for 1h, record the temperature of the surrounding environment of the transformer, the temperature of the top oil layer and the temperature of the inlet and outlet of the radiator, then cut off the power supply and minimize the current. At this time, the temperature rise of the winding group can be obtained by measuring the value of the thermal resistance. The test system used in this test is an automatic measurement and control system for transformer temperature rise test based on PC. the control equipment of the system is PC. the data acquisition, control of test equipment and management of instruments and meters are realized through interface and serial interface. In the temperature rise test, the voltage and current signal applied by the measured transformer is attenuated by the voltage and current transformer, then the signal is transformed by the test console, a / D conversion is carried out by the data acquisition card, and then the data is transmitted to the PC through the interface. Finally, the PC realizes the calculation and display of three voltage, current and power, After judging the calculation results, the corresponding control signal is output to the control equipment.
B. To control the temperature rise of power transformer within the range required by the standard, it is recommended to start from the following:
1. The measurement of no-load loss and no-load current, short-circuit impedance and load loss in routine test are qualified, which does not necessarily ensure that the temperature rise test is also qualified. Therefore, hengfengyou electric controls the heating capacity of the transformer by reducing the design standard of no-load loss and load loss of the transformer by 10% lower than IEC and GB standards (to save cost, less than 5% for most manufacturers), It is conducive to the passing of temperature rise test. In the internal loss of the transformer, the no-load loss is basically unchanged and increases slightly with the increase of operation time. Only the load loss changes with the change of operation load. Hengfengyou electric recommends that the user avoid overload operation of the transformer. For long-term operation, it is recommended to operate at 80% capacity.
2. Improve the supply chain management of purchased products and control the quality of purchased products to ensure the quality of the whole power transformer. Hengfengyou Electric has established a perfect SQA supplier management system and has strict procurement and management standards for key components and raw materials directly related to transformer temperature rise, such as shell (including radiator) of liquid immersed transformer, material and production of silicon steel sheet of iron core, material and size of copper (aluminum) wire or copper (aluminum) foil, coil structure and winding, transformer oil, etc. If there are other power transformer consulting or procurement needs: Jack（ info@hengfengyou.com ）。
