Why DC Winding Resistance Testing of Transformers is Needed?

DC winding resistance testing is considered an essential method for troubleshooting windings, revealing issues such as loose windings, winding deformations, local defects, or incorrect connections. These issues are categorized as faults because they cause a significant number of transformer failures each year. Winding resistance testing can also detect problems with transformer tap changers, on-load tap changers (OLTC), and/or de-energized tap changers (DETC)—the main components, and according to some statistics, the most prominent category of failure in transformers.

The JYR-20S utilizes an ARM (Advanced RISC Machines; USA) high-precision multi-core CPU, offering stable performance and high computational accuracy. It also adopts third-generation constant current source technology, with a maximum output current of 20A, a range of 0Ω to 20kΩ, and an output voltage of up to 24V. It features a built-in channel conversion matrix. The JYR-20S allows various tests on power transformers to be performed without rewiring. The instrument can complete three-phase simultaneous tests, phase-by-phase tests, magnetic assistance tests, and single-phase DC winding resistance tests.

JYR-20S Mian Feature Function:

1.The testing lines are connected to the transformer in one trial, without the need to reset the testing lines during the testing process.

2.Simultaneous testing of three phases is adopted when testing the Yn type, using a high-voltage YN three-phase simultaneous measurement compensation method (including O-phase resistance), and the balance rate of resistance across the three phases is calculated automatically.

3.For Yn/D(Y) types, phase-by-phase testing can be performed, and the balance rate of resistance across the three phases is calculated automatically. This solves the issue where the resistance of the neutral point's leading wire cannot be measured.

4.Automatic magnetic assistance is applied for low-voltage testing when testing large-capacity YnD11 transformers (with a magnetic assist box inside).

5.An auxiliary function judges data stability by automatically calculating the percentage deviation of resistance at 5", 15", or 30" intervals, accurately determining the authenticity of the test data.

6.The large screen display allows for user-friendly operation, with printing via USB and a 485 communication interface.

7.Protection functions include misconnection protection for 380V power, power-off protection, back EMF protection, and a clear discharging indication.

Other Functions of JYR-20S:

1.The JYR-20S features a temperature conversion function. By selecting the test material (copper/aluminum) and inputting the temperature (optional special wireless temperature probe to collect the test temperature directly), the instrument automatically converts the resistance to the set standard temperature for easy comparison with historical data.

2.The instrument can store 100 sets of test data. It has a USB interface to import data into a USB drive and a built-in Bluetooth communication module to interact with a PC and other computer data, or to connect to a micro-Bluetooth printer for printing data reports.

3.The "Test/Stop" mechanical button provides shortcuts and includes an automatic shutdown function if there is no operation for 5 minutes.

4.The built-in rechargeable lithium battery can complete up to a hundred transformer tests on a single charge. Fully balanced battery charging technology effectively extends battery life.

5.The high-brightness color touch LCD display provides fast and clear touch menu operation.

6.The instrument is equipped with a discharge sound alarm, overheat alarm, and other protective circuits. Clear instructions help reduce mishandling.

Technology Specification:

Deployment	JYR-10S	JYR-20S
Output current	Auto、 10A、 3A、 1A、 300m A、 100mA 、 30mA、 10mA	Auto、 20A 、 3A、 1A、 300m A、 100mA 、 30mA、 10mA
Test range	0~20kΩ
Accuracy	For 10S: 0.2%±0.4μΩ For 20S: 0.2%±0.2μΩ
Minimum resolution	0.1μΩ
Power supply in operation	AC220V±10%, 50Hz±1Hz(can be customized)
Temperature in operation	-20~40℃
Relative humidity	≤80%RH, No forming dew
Volume	Length 420mm  Width 320mm  Height 200mm
Net weight	13.8 kg