KV Hipot testing equipment was used for the main transformer testing of the 220 kV step-up substation in the Inner Mongolia 600 MW/2,400 MWh energy storage project.

At the site of the 600 MW/2,400 MWh independent new energy storage project in Dingyuanying, Alashan, Inner Mongolia, KV Hipot Power Equipment Co., Ltd.’s three-phase DC resistance tester (20A) and three-phase turns ratio tester were used for electrical testing of the main transformer at the 220 kV step-up substation, supporting winding resistance measurement and turns ratio verification during the on-site commissioning phase.

This project has an energy storage capacity of 600 MW/2,400 MWh. The main transformer at the step-up substation is responsible for voltage conversion between the energy storage system and the high-voltage grid. On-site testing focused on the main transformer windings, connection circuits, and tap positions. Through DC resistance and turns ratio measurements, complementary data were obtained for equipment condition verification.

On September 24, 2026, a DC resistance test was conducted on the high-voltage side of the main transformer. A KV Hipot three-phase DC resistance tester (20A) was used to measure the resistance by connecting it to the terminals of the winding under test. The DC resistance test focuses on checking the resistance characteristics of the windings and related connection circuits, providing a reference for troubleshooting poor connections, abnormal winding connections, and tap contact problems.

For large main transformers, the validity of DC resistance data depends not only on the instrument readings but also on wiring contact, tap position, measurement stability, and temperature conditions. On-site records must clearly specify the winding, phase, and tap position corresponding to each set of data. When comparing the results with factory records, consistent measurement criteria should be used, and temperature conversion should be performed according to applicable methods. The 20A rating was the instrument configuration used in this test; the specific test current should be selected based on the winding under test and the test plan.

On September 25, 2026, a main transformer turns ratio test was conducted on-site using a KV Hipot three-phase turns ratio tester to verify the transformation ratios between different windings and their correspondence with the tap positions. During testing, reference values must be set based on the main transformer’s nameplate voltage, vector group, and tap parameters. The measured results are then compared with the corresponding theoretical values.

Turns ratio verification can help identify winding or tap connection abnormalities that require further investigation. For three-phase transformers, result analysis must also consider the vector group and instrument measurement method to ensure the correct conversion relationships among the line voltage ratio, phase voltage ratio, and turns ratio, avoiding misjudgments due to incorrect parameter settings or wiring mismatches.

DC resistance and turns ratio tests verify the main transformer from two aspects: resistance characteristics and voltage transformation relationships. When an abnormality is found at a certain tap position, the corresponding DC resistance and turns ratio data can be used for verification, gradually narrowing down the scope of investigation. Complete test records should retain the measurement conditions, original data, and review results, providing traceable information for subsequent quality reviews and equipment operation management.

KV Hipot Transformer Testing Solutions

This field application demonstrates the practical use of KV Hipot transformer testing equipment in the commissioning of a 220 kV step-up substation for a large-scale energy storage project.

KV Hipot Power Equipment Co., Ltd. provides transformer testing equipment for power engineering contractors, substation commissioning teams, utilities, testing service companies, and operation and maintenance organizations.

Our transformer testing solutions include equipment for:

• DC winding resistance measurement
• Transformer turns ratio testing
• Transformer capacitance and tan delta testing
• Sweep frequency response analysis (SFRA)
• Transformer insulation testing
• Transformer oil testing
• AC withstand and other high-voltage commissioning tests

For different transformer capacities, voltage levels, winding configurations, and field-testing requirements, KV Hipot can assist customers in selecting an appropriate test equipment configuration to match their actual commissioning and maintenance tasks.