Several schemes are used to provide fast and reliable protection for transmission lines. The most common include:

• Distance Protection: This is a widely used method where relays measure the impedance of the line to determine the distance to the fault. Relays are set with multiple "zones of reach" to provide both primary and backup protection. For example, a Mho relay is commonly used for long transmission lines due to its immunity to power swings.

• Differential Protection: This scheme compares the current entering and leaving a protected zone. Under normal conditions, these currents are balanced. An imbalance indicates a fault within the zone, triggering the relay to act.

• Pilot Protection: This scheme uses communication channels (like fiber optics, microwave, or power line carriers) to exchange information between the relays at both ends of a line, enabling high-speed tripping for faults anywhere on the line.

Our company's equipment is used by professionals who install and maintain the components required for these advanced protection systems.