Key points for preparation before testing
Before starting the operation, strictly follow the procedures of power outage, electricity inspection, and grounding wire hanging. Confirm that both the high and low voltage sides of the transformer are completely powered off and there is no residual voltage. Ensure that the site is properly fenced and marked with warning signs for safety.
Check the transformer nameplate parameters, record the rated transformation ratio, wiring group, capacity, and voltage level, and set the tester's corresponding wiring mode and rated parameters in advance.
Check whether the instrument power cord, test line, and grounding clip are intact and undamaged, and ensure that the wiring terminals are clean and free from oxidation, to avoid test errors caused by poor contact.
Ground the instrument reliably, place it in a stable and dry location, keep it away from strong electromagnetic interference sources, and ensure that the site is ventilated and free from rain, snow, and dampness.
Key points of on-site wiring operation
Strictly follow the transformer wiring group corresponding to the instrument wiring diagram, and connect the test lines to the high-voltage side and low-voltage side respectively, with each phase line corresponding to one another. Misconnection and short circuit are strictly prohibited.
The test wire clamp is used to securely grip the transformer bushing terminal, ensuring tight contact. The surface oxide layer and oil stains are removed to minimize measurement deviations caused by contact resistance.
The three-winding transformer needs to be wired and tested in the order of high-medium, high-low, and medium-low gears, and no winding combination should be omitted.
After wiring is completed, conduct a phase-by-phase review again to confirm that there are no inter-phase short circuits or incorrect grounding connections. Irrelevant personnel should be evacuated from the testing area.
Key points of instrument operation and testing process
After powering on, the instrument performs a self-check. Select the automatic transformation ratio test mode, and correctly set the wiring group, tap position, and rated voltage ratio parameters.
Adjust and test the transformer tap changer step by step according to its positions, wait for the data to stabilize at each position before saving the record, and strictly prohibit skipping positions during testing.
During the testing process, it is prohibited to touch the wiring terminals or tap switches, and it is not allowed to move the instruments arbitrarily, in order to avoid vibration and external interference that may affect the accuracy of the data.
If data drift, errors, or excessive transformation ratio deviation occur, immediately stop the test, check the wiring, grounding, and gear setting, and perform re-measurement after troubleshooting.
Data judgment and key points for closing
Compare the actual measured transformation ratio with the rated transformation ratio on the nameplate, strictly adhere to the allowable error range specified in the regulations, and determine whether it is qualified. Meanwhile, record the data for each gear transformation ratio, phase, and group.
Save the original test data and screenshots for archiving, and annotate the test time, weather, staff, and transformer number for future traceability and comparison.
After the test is completed, first turn off the instrument power supply, then remove the test wires and grounding wires, organize the cables in order, and restore the equipment to its original state on site.
Clean up the work site, remove safety barriers, fill out test record reports, and promptly analyze the causes of out-of-limit and abnormal data, and report for handling.