Which of the following can cause damage to distribution equipment? Mark all that apply.
Lowering the pole ground resistance at a capacitor bank will help with which of the following (mark all that apply)?
Lowering the pole ground resistance at a transformer will help with which of the following (mark all that apply)?
Which of the following will be improved with better grounding? Mark all that apply.
On which factor do you select the surge arrester rating? Mark all that apply.
Better line insulation helps with which of the following? Mark all that apply.
External gaps are recommended to help reduce arrester failures.
Per IEEE C62.22-2009, what is the minimum MCOV for an arrester used on a 13.8-kV multigrounded system?
Which type of insulation is most dependent on the voltage waveshape and duration?
Which type of insulation is least dependent on the voltage waveshape and duration?
For arresters at the open point of a cable, which type of surge rise time is most damaging to the cable system?
On a three-phase line recloser, how many arresters are needed on the structure for adequate protection?
What is the probability of a negative first stroke that is greater than 45 kA? Use the EPRI (1992) approximation on p. 664.
What is the probability of a negative first stroke that is greater than 45 kA? Use the Anderson-Eriksson model in Table 13.1 on p. 664.
In open ground, find the average strikes to an overhead line using the Eriksson model. Assume 5 flashes/km^2/year and a line height of 40 ft.
For an underground cable in open ground, find the average strikes that attach to that cable per year using the Sunde model. Assume 5 flashes/km^2/year and 1000 ohm-m soil.
On a distribution transformer, calculate the protective margins for both BIL and CWW for the following parameters: system voltage = 12.5 kV, transformer size = 50 kVA, lead length = 4 ft, arrester duty cycle rating = 10 kV, arrester LPL = 34 kV. Assume 8 kV/ft of lead length.
On a distribution transformer with the following parameters, calculate the lead length necessary to maintain a protective margin for BIL of 50%: system voltage = 34.5 kV, transformer size = 50 kVA, lead length = 4 ft, arrester duty cycle rating = 10 kV, arrester LPL = 34 kV. Assume 8 kV/ft of lead length.
Using the enhanced version of the Rusck model proposed by Darveniza, find the induced voltage on an overhead line based on the following parameters: line height = 40 ft, lightning current = 25 kA, distance from the line = 50 ft, and earth resistivity = 1000 ohm-m.
Visit overhead distribution lines in your area. Find and photograph five examples of lightning protection issues, possibly including the following:
Use EMTP or another transient program to model a lightning strike to a distribution line as in Figure 13.38. Evaluate the impact on a pole-mounted controller. Include the following:
Write a spreadsheet that calculates protective margins for overhead and underground systems. Include all appropriate inputs needed.
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