The three-channel transformer DC resistance tester is a core instrument for the detection of power transformers, mutual inductors and other inductive equipment. It is mainly used to measure the DC resistance of transformer windings together with bushings. Application scope
The core advantage of this instrument is that it can simultaneously measure the resistance of three-phase windings, significantly improving work efficiency and enabling the detection of abnormal differences in three-phase resistance through data comparison.
Power Transformer Handover and Preventive Tests
Substations and power plants: After the installation or major overhaul of a new transformer, it is necessary to measure the DC resistance to check the welding quality of the winding joints, the contact condition of the tap changer, and whether there is an inter-turn short circuit.
Regular inspection: Regularly detect whether there is any loosening or oxidation at the connection points of the transformer windings and leads.
Transformer Winding Fault Diagnosis
By analyzing the imbalance rate of three-phase resistance, it is possible to determine whether the transformer has faults such as poor contact of the tap changer, broken strands in the winding, or interlayer short circuits.
On-load Tap Changer (OLTC) Testing
The instrument generally has a winding test function and can be used to detect whether the contact resistance of the tap changer during the switching process is qualified, as well as whether there are problems such as excessive transition time or contact erosion.
Transformer Testing
Suitable for DC resistance measurement of voltage transformers (PT) and current transformers (CT).
Other Inductive Load Testing
Can be used for DC resistance measurement of windings in large motors, reactors, and other equipment.
Selection Guide
When choosing a three-channel DC resistance tester, the following core parameters and functional requirements should be comprehensively considered:
1. Core Parameters: Test Current and Range
The test current and range are determined by the capacity of the transformer being tested and are the primary basis for selection.
Small-capacity transformers / distribution transformers (<1600kVA): It is recommended to use a three-channel tester with a test current of 5A or 10A. These have high resolution and are compact, making them easy to carry on-site.
Medium-capacity transformers (1600kVA – 30000kVA): It is recommended to use a three-channel tester with a test current of 20A or 40A. This can stabilize the inductive effect and shorten the test time.
Large power transformers / generator sets (>30000kVA): It is recommended to use a three-channel tester with a test current of 50A or above (such as 60A or 100A). The large current can quickly establish a magnetic field and significantly reduce the inductive charging time. Usually, it is necessary to use it in conjunction with a demagnetization function.
2. Key Functional Features
On-load Tap Changer (OLTC) testing function
If the managed transformers are mainly on-load tap changers, it is recommended to choose a model with dynamic testing or transition resistance waveform analysis functions. This can capture the switching waveforms of the tap changer and assess the service life of the switch.
Demagnetization function
After completing the DC resistance test on large transformers, the core is prone to residual magnetism, which may cause excessive inrush current during operation and trigger incorrect relay protection actions. If large-capacity transformers are frequently tested, it is recommended to choose a model with an automatic demagnetization function.
Data storage and communication
It is preferable to choose an instrument that supports U disk storage, Bluetooth transmission, or background software management to facilitate the generation of test reports later.
3. Wiring Method
Five-core wiring method (recommended): Use A/B/C three-phase current and voltage lines plus the neutral point N line. This can completely eliminate errors caused by test leads and contact resistance, especially suitable for measuring small resistances below 1mΩ.
Three-core simple wiring: Some simplified models use three-core wiring, which has a higher wiring efficiency but slightly lower measurement accuracy than the five-core wiring method.
4. Anti-interference capability
When used in substations with strong electromagnetic interference environments of 500kV and above, it is recommended to choose an instrument with strong anti-interference capability (such as with shielded interface) to ensure stable and reliable test data.
Post time: Mar-02-2026