Key Technologies for Long-Distance Protection of High-Voltage Transmission Lines

Long-distance protection of high-voltage transmission lines primarily relies on technologies such as differential protection, distance protection, and automatic reclosing. Together, these technologies effectively ensure safe power transmission and stable grid operation.

In the vast power transmission network, high-voltage transmission lines play a crucial role, acting as energy arteries that deliver electricity from power plants to homes and businesses. However, as transmission lines extend over longer distances, ensuring power stability and safety—especially during long-distance transmission—has become a critical challenge for power engineers.

1. Differential Protection: Accurately Identifying Fault Zones

Differential protection is a key component in long-distance protection of high-voltage transmission lines. Based on Kirchhoff's Current Law, it compares the magnitude and phase of currents at both ends of the protected line to determine whether an internal fault exists. When a short circuit or other internal fault occurs, the current difference between the two ends increases significantly, triggering the differential relay to rapidly isolate the faulty section. This prevents fault escalation and ensures the rest of the power grid continues to operate normally.

2. Distance Protection: Rapidly Isolating Fault Locations

Distance protection determines the location of a fault by measuring the ratio of voltage to current (i.e., impedance) at the sending end of the line. During a short circuit, the impedance at the fault point drops sharply. The distance protection relay calculates the distance to the fault based on this measured impedance and issues a tripping command to isolate the faulty section from the grid. This method offers fast operation and excellent selectivity, making it particularly suitable for protecting long-distance transmission lines.

3. Automatic Reclosing: Enhancing Power Supply Reliability

In addition to the above methods, automatic reclosing is an essential part of long-distance transmission line protection. Many grid faults are transient in nature, such as those caused by lightning strikes or bird contacts. After such faults are cleared, the line often returns to normal operation. The automatic recloser detects a line trip, waits for a preset time delay (to allow transient faults to clear), and then automatically closes the circuit breaker to restore power. This significantly improves power supply reliability and minimizes outage-related losses for consumers.

In summary, long-distance protection of high-voltage transmission lines is a complex and systematic engineering task that depends on the integrated application of multiple protection technologies. The combined use of differential protection, distance protection, and automatic reclosing provides robust support for the safe and stable operation of the power grid. As power system technologies continue to advance, we can expect even more innovative protection solutions to emerge, injecting new vitality into the future of power transmission.