In the long-term operation and maintenance of offshore wind power equipment, insulation resistance testing is a key means of assessing the insulation condition of electrical equipment and preventing latent faults. Recently, during the outage maintenance of a transformer at the Three Gorges Dafeng Offshore Wind Farm that had been in operation for five years, the QLDM-DA insulation resistance tester developed and manufactured by Baoding Qilida Electric Technology Co., Ltd. accurately identified an insulation anomaly in the high-voltage bushing’s end screen. This provided a reliable basis for equipment defect location and handling, ultimately ensuring the safe resumption of transformer operation. This demonstrates the testing capabilities and engineering value of Baoding Qilida Electric Technology Co., Ltd.’s equipment in harsh environments.
Case Background: Periodic Insulation Assessment of Offshore Wind Power Transformers
As an important node in the green energy supply of East China, the operational reliability of equipment at the Three Gorges Dafeng Offshore Wind Farm directly affects the stability of the regional power grid and power generation efficiency. The transformer to be inspected at this offshore substation (model: S11-110000/220, rated capacity: 110000/110000 kVA) had been in operation for five years. The owner strictly adhered to the preventative testing procedures for power equipment, conducted a special insulation resistance assessment, and used a QLDM-DA insulation resistance tester provided by Baoding Qilida Electric Technology Co., Ltd. to systematically and comprehensively test the insulation condition of the transformer body and its auxiliary components.
Testing Process and Anomalies Found
Testing personnel used the QLDM-DA to measure the insulation resistance of key components such as the transformer windings, bushings, and grounding system. When testing the insulation resistance to ground of the high-voltage dry bushing’s end screen (bushing model: FGRBWL2-252/630), the instrument reading was only 5 MΩ, far below the standard requirement.
Standards compared:
GB 50150 “Electrical Installations – Acceptance Testing Standard for Electrical Equipment”
IEC 60137 “Insulating Bushings with AC Voltage Higher than 1000V”
Both standards clearly stipulate that the insulation resistance to ground of the bushing’s end screen should not be less than 1000 MΩ. The test results clearly showed that the insulation of the bushing’s end screen was severely deteriorated, posing a potential grounding hazard or internal moisture ingress.
Problem identification and manufacturer collaboration
Based on the test data, on-site technical personnel from the bushing manufacturer were immediately contacted for verification. Disassembly and inspection revealed structural defects and material deterioration in the high-voltage bushing’s end screen terminals, leading to a significant decrease in its insulation performance in the assembled state.
To further verify, the technicians removed the end screen terminals and conducted individual tests. The insulation resistance to ground of the end screen recovered to 5000 MΩ, proving that the main bushing insulation was intact, and the problem was concentrated on the quality and structural design of the end screen terminals.
On-site handling and retesting passed.
The manufacturer replaced the terminal block with a newly designed one on-site. After reinstallation, insulation testing was conducted again using the QLDM-DA insulation resistance tester from Baoding Qilida Electric Technology Co., Ltd. Data showed:
Insulation resistance to ground of the replaced terminal block: ≥ 2500 MΩ. This fully meets the standard requirements, and insulation performance has been significantly restored.
Power restoration and operational verification.
After completing all maintenance items, the transformer was successfully energized. All operating parameters were normal, and no further insulation-related alarms occurred. This maintenance, through precise testing and rapid handling, avoided a potential equipment failure caused by insulation deterioration, ensuring the continuous and stable operation of the wind farm.
The core value of the QLDM-DA insulation resistance tester from Baoding Qilida Electric Technology Co., Ltd.
In this case, the QLDM-DA demonstrated its superior performance even in the high humidity and high salinity environment of the sea:
1. High precision and wide measurement range: Accurately measures insulation resistance from kΩ to TΩ, adapting to the testing needs of various equipment.
2. Strong anti-interference capability: Suitable for complex electromagnetic environments such as offshore wind power, providing stable and reliable test data.
3. Intelligent operation: Automatically calculates absorption ratio and polarization index, generating test reports with one click, improving maintenance efficiency.
4. Strong standard compliance: Built-in multiple international and domestic standard thresholds assist in rapid on-site judgment.
Qilida’s Technical Service Philosophy
Baoding Qilida Electric Technology Co., Ltd. adheres to the service philosophy of “Instruments are tools, data is language, and safety is the goal.” We not only provide high-performance electrical testing equipment but also strive to help users discover hidden dangers, diagnose faults, and verify solutions through precise measurements, achieving closed-loop management from “testing” to “management.”
In the fields of new energy, power grids, industry, and transportation, Baoding Qilida Electric Technology Co., Ltd. is willing to safeguard the safety of your power equipment throughout its entire lifecycle with reliable products and professional technical support.
