Understanding Over-Voltages and Lightning Surges
Switching over-voltages and lightning surges are significant concerns in electrical systems, particularly in Extra High Voltage (EHV) and Ultra High Voltage (UHV) systems. Here’s why switching over-voltages are more hazardous in these scenarios.
1. Nature of Over-Voltages
- Switching over-voltages occur during the operation of electrical equipment, especially when circuits are opened or closed.
- These over-voltages can reach magnitudes significantly higher than the system's normal operating voltage.
2. Impact on EHV/UHV Systems
- EHV and UHV systems operate at voltages above 220 kV and 800 kV, respectively.
- The high capacitance and inductance in these systems can amplify the effects of switching actions, resulting in extreme voltage spikes.
3. Comparison with Lightning Surges
- Lightning surges, while dangerous, usually have a relatively short duration and are somewhat predictable in terms of occurrence.
- Conversely, switching over-voltages can happen frequently and unexpectedly during normal operations, leading to repeated stress on the system.
4. Equipment Vulnerability
- EHV and UHV systems contain sensitive and expensive equipment that may not withstand the extreme voltage levels caused by switching over-voltages.
- The insulation and protective devices designed for these systems may fail under such conditions, causing significant damage.
5. Conclusion
- In summary, the unpredictable nature and the potential for extremely high voltage levels from switching operations make switching over-voltages particularly hazardous in EHV and UHV systems.
- This distinction emphasizes the importance of robust protective measures in the design and operation of high-voltage electrical networks.