# The Pacific Intertie is a high voltage direct current (HVDC) connection between the Pacific Northwest and California, designed to take advantage of hydroelectric power to meet electricity demand in Southern California. The HVDC connection transmits electricity from the Dalles Dam in Oregon to Los Angeles. The Dalles Dam has a nameplate capacity of 1,780 MW. A 900-mile HVDC power line connects the dam to the Los Angeles area. Because of the differences in weather patterns and electricity demand in the two regions, the Dalles Dam supplies energy to the Los Angeles area during the summer across the HVDC line, when demand in Southern California is high and water from snowmelt in the Northwest is usually plentiful.   a) When dams produce electricity, they use a generator to convert hydraulic motion to alternating current (AC) power. Before this power is transmitted via the Pacific Intertie, an HVDC converter station is used to convert that AC power from the dam to DC power. What is one benefit and one drawback of the current design of the Pacific Intertie, where DC power is transmitted instead of AC power?   b)When the Pacific Intertie was first constructed in 1965, electricity was transmitted at avoltage of 800. kV. How much current (in amps) flowed through the transmission line when the dam was producing its rated power?   c) In 2012, the HVDC converter station (which converts AC power from the dam to DC power for transmission) was upgraded to its current voltage of 1150 kV. How much current (in amps) currently flows through the transmission line when the dam is producing its rated power?   d) The resistance of a transmission line is proportional to its length (assuming for simplicity that temperature is constant). Assume that between 1965 and 2012, the Pacific Intertie used the same material for the transmission line, which had a resistance of 2.14 x 10^-3 Ω per 1000. feet. What is the total resistance of the transmission line?   e)When the Dalles Dam is producing its rated power, how much power loss was there in the transmission line in 1965? How about after the upgrade in 2012?    f) What percentage of the dam’s rated power was lost in transmission in 1965? In2012?   g) Based on your answer to part f, explain the relationship between voltage and power loss.   h)Electricity demand in the Los Angeles area is 3,500 MW from 1 am to 7 am; 4,700 MW from 7 am to 12 pm; 5,900 MW from 12 pm to 9 pm; and 4,100 MW from 9 pm to 1 am. Assume the Dalles Dam provides all of its generated electricity to the Los Angeles area and only accounts for 25% of the Los Angeles area electricity supply at any given time. Calculate the capacity factor for the hydroelectric facility over one day, accounting for the loss in power incurred during transmission of electricity using the values for transmission power loss calculated for the 2012 system in part (e).

Question
The Pacific Intertie is a high voltage direct current (HVDC) connection between the Pacific Northwest and California, designed to take advantage of hydroelectric power to meet electricity demand in Southern California. The HVDC connection transmits electricity from the Dalles Dam in Oregon to Los Angeles. The Dalles Dam has a nameplate capacity of 1,780 MW. A 900-mile HVDC power line connects the dam to the Los Angeles area. Because of the differences in weather patterns and electricity demand in the two regions, the Dalles Dam supplies energy to the Los Angeles area during the summer across the HVDC line, when demand in Southern California is high and water from snowmelt in the Northwest is usually plentiful.

a) When dams produce electricity, they use a generator to convert hydraulic motion to alternating current (AC) power. Before this power is transmitted via the Pacific Intertie, an HVDC converter station is used to convert that AC power from the dam to DC power. What is one benefit and one drawback of the current design of the Pacific Intertie, where
DC power is transmitted instead of AC power?

b)When the Pacific Intertie was first constructed in 1965, electricity was transmitted at avoltage of 800. kV. How much current (in amps) flowed through the transmission line when the dam was producing its rated power?

c) In 2012, the HVDC converter station (which converts AC power from the dam to DC power for transmission) was upgraded to its current voltage of 1150 kV. How much current (in amps) currently flows through the transmission line when the dam is producing its rated power?

d) The resistance of a transmission line is proportional to its length (assuming for simplicity that temperature is constant). Assume that between 1965 and 2012, the Pacific Intertie used the same material for the transmission line, which had a resistance of 2.14 x 10^-3 Ω per 1000. feet. What is the total resistance of the transmission line?

e)When the Dalles Dam is producing its rated power, how much power loss was there in the transmission line in 1965? How about after the upgrade in 2012?

f) What percentage of the dam’s rated power was lost in transmission in 1965? In2012?

g) Based on your answer to part f, explain the relationship between voltage and power loss.

h)Electricity demand in the Los Angeles area is 3,500 MW from 1 am to 7 am; 4,700 MW from 7 am to 12 pm; 5,900 MW from 12 pm to 9 pm; and 4,100 MW from 9 pm to 1 am. Assume the Dalles Dam provides all of its generated electricity to the Los Angeles area and only accounts for 25% of the Los Angeles area electricity supply at any given time. Calculate the capacity factor for the hydroelectric facility over one day, accounting for the loss in power incurred during transmission of electricity using the values for transmission power loss calculated for the 2012 system in part (e).