Line Distance Protection

Distance protection is and remains by far the main protection principle for overhead lines and cables. It is reliable, fast and largely manages to eliminate the variable system quantities of load and supply out of the protection calculation.

Distance protection is in its core an impedance measurement, comparing a known line impedance against a measured system impedance. A modern distance protection IED (Intelligent Electronic Device) has to deal with many more features though; phase selection, load encroachment, power swing detection, scheme communication, phasor measurement, monitoring, control, and backup protection – a wide variety of tasks are performed, differing from installation to installation and customer to customer.

In order to cope with any situation, a modern protection IED needs to be configurable to fit within its intended application area. Hitachi Energy's solution to this requirement is the Relion series of IEDs. The Relion series offers a standardized library of the functionality on a high performance, common hardware architecture, and provides the flexibility and configurability to suit any application area.

The Relion 650 series distance protection IEDs are characterized as devices fulfilling common application requirements, typically characterized as sub-transmission. Depending on the required specifications the 650 series can be used on distribution and transmission levels as well though. The Relion 650 series distance protection IEDs include all required back-up functionality and the full power and flexibility of the Relion platform.

The Relion 670 series distance protection IEDs improve upon the 650 series to fulfill more demanding applications, offering improved performance, increased customization options of hardware and software, and allowing for increased functional integration and scalability.

The PSL 6602U is ideal as an alternative to the Relion series offering, ultimately suitable as a main 2 solution as it uses a different hardware architecture and its own protection algorithms. Based on a reliable architecture with a redundant CPU and A/D conversion, it applies for advanced distance protection with back-up protection in a configured package, making it very user friendly and intuitive.