Effects of GIC Neutral Blocking Devices (NBDs) on transmission lines protection performance and potential for resonance

摘要

Geomagnetic Induced Current (GIC) is a quasi-DC current that may have adverse effects on power system reliability. Several GIC blocking device (NBDs) designs are available, but the majority is capacitive. Concerns have arisen about the effects of NBDs on distance-protection relays. To investigate their impact, real-time simulation (of IEEE-39 bus system) with actual hardware-in-the-loop testing is utilized. The study showed that these relays are not affected by the insertion of NBDs regardless of the polarizing quantity used. However, during close-by fault, the energy through NBDs’ MOV is excessive. Also, the potential for resonance between NBDs and the system was investigated. The results indicate the possibility for resonance under steady-state imbalance, however, in most cases resonance is masked by a high damping system, thus it becomes indiscernible. But under fault conditions, even for non-resonating conditions, care is needed to avoid over-voltages by providing a backup spark-gap for MOV devices.