Mark any advantages of underground relative to overhead distribution.
Mark any advantages of underground relative to overhead distribution.
Which type of cable is most susceptable to water treeing?
What options should reduce problems with water treeing? Mark all that apply.
Faults on underground systems are generally permanent rather than temporary. What is the most common exception? Faults in:
Which type of cable has the lowest dielectric losses?
True/false: Dielectric losses are higher at higher voltages.
Which soil is the worst for cable ampacity?
On a single-phase cable, if you decrease the resistance of the neutral, what will happen to the loop resistance of the cable?
For a three-phase cable system with 350-kcmil aluminum cables in a flat configuration with a separation of 7.5” and 1/3 neutrals, what has the most impact to reduce zero-sequence resistance?
True/false: Ampacities are lower in direct-buried cable than for cable in conduit.
For a 350-kcmil cable in a triplex configuration, which of the following is best for cable ampacity?
Find the maximum electric field on a single-phase cable for the following combinations:
If a cable has a resistance of 0.1 ohms/kft at 20°C, find the resistance at 90°C.
Find the capacitance from line to ground of 1 mile of a 500-kcmil copper cable with 220-mil insulation.
Using the Anders approximation, find the resistance at 1000 Hz as a multiplier of the dc resistance for a 500-kcmil copper cable with EPR insulation.
If a cable has an ampacity of 500 A at an earth temperature of 20°C and an allowed conductor temperature of 80°C, find the new ampacity if the allowed conductor temperature is increased to 95°C.
For a fault current of 5000 A, find the minimum clearing time needed to prevent damage on a 500-kcmil copper 175-mil EPR cable. If the cable has a 4-mil copper sheath, also find the minimum clearing time to prevent damage (assume all fault current flows in the cable sheath).
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