Question

Energy Transmission/Distribution (fifth topic) Main operating units in the electric power system are - Power Generating Units (conventional as well as renewable) Substations/Switch Yards - Transmission Lines Consumers (industrial and domestic) Transformation, connection and distribution in the electric power network,” The Grid", is being realized in substations. Primary function of a substation is the transformation of an incoming transmission line voltage level to another outgoing transmission line voltage level. As Substations are situated at regular distance intervals they can isolate (disconnect) malfunctioning generating/consumer units as well as faulty transmission lines enabling thus the rest of the grid to continue operating. 7. Which device is used to detect this fault condition? (3%) 8. What can cause extreme high currents in the power system. (3%) 9. How many times can a fault current be compared to the normal current. (3%) 10. Which device detects such a fault? (3%) 11. Which devices are destined to counter the sudden huge energy impulses when lightning hits the power system? (3%) 12. In a substation, when are connector (isolator) switches being operated and when are circuit breakers (power switches) being activated? (3%) 13. Why is it desirable to extinguish the arc at the contacts of the circuit breaker as fast as possible? (3%) 14. Name three properties of SF6 gas (sulfur hexa fluoride) that make it so suitable to extinguish the arc in circuit breakers. (6%)

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