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Voltage transformer secondary circuit short circuit fault online monitoring and preventive measures - Database & Sql Blog Articles
Voltage transformers play a crucial role in power systems, acting as essential components that bridge the primary and secondary circuits in AC systems. They are used to transmit electrical information to measuring instruments, protective devices, and control systems. Like regular transformers, voltage transformers operate on the same basic principle, consisting of a primary winding, a secondary winding, and an iron core. The windings and core are insulated to ensure safe operation. Under normal conditions, the secondary voltage is proportional to the primary voltage.
It’s important to note that the secondary winding of a voltage transformer must never be short-circuited or grounded. If this occurs, the impedance drops significantly, causing the secondary voltage to drop to zero and the magnetic flux to become distorted. This can lead to severe core saturation, increased iron losses, and overheating. Prolonged exposure can damage the insulation and even burn out the windings. Additionally, fuses may blow, affecting meter readings and potentially causing malfunctions in protection systems. To prevent such issues, the national standard DL408-91 explicitly states that “secondary circuits of live voltage transformers must strictly avoid short circuits or grounding.â€
Common causes of secondary circuit short circuits include:
1. Short circuits in the connecting cables.
2. Grounding due to moisture, corrosion, or physical damage.
3. Internal metal defects leading to short circuits.
4. Moisture and rust at outdoor terminal joints.
5. Poor wiring practices in voltage transformers.
6. Omissions during pre-testing or maintenance.
Regular inspections can help identify these faults through observable signs such as:
- Unusual noise from the transformer.
- Excessive heat and burning smell.
- Abnormal meter readings or protection device malfunctions.
- Physical damage or burning of the secondary winding.
To address these challenges, online monitoring systems have been developed. These systems continuously monitor current in the PT secondary loops. When the current exceeds a set threshold (e.g., 8A for 20ms), it triggers a protection signal, isolates the faulty loop, and alerts maintenance personnel with sound and light alarms. This real-time monitoring not only detects faults early but also helps locate the issue quickly, preventing potential accidents.
In conclusion, both manual patrols and online monitoring are effective methods for detecting and addressing secondary circuit faults in voltage transformers. Implementing these strategies ensures safer operations and compliance with industry standards like DL408-91. By combining proactive inspection with advanced monitoring technologies, power system reliability can be significantly improved.