A THHN conductor will have 75°C termination on one end and a 60/75°C termination on the other, which ampacity column will be used?

Conductor with 75 °C temperature rating must have ampacity from the 60°C column or the 75°C column.
It is permissible to use the 75°C rating if the installed conductor is rated at least 75 °C.
Because all of the connection points in this example have at least a 75°C rating, the conductor’s ampacity can be based on the 75°C column

Murray loop test is performed on a faulty cable 300 m long. At balance, the resistance connected to the faulty core was set at 15 Ω and the resistance of the resistor connected to the sound core was 45 Ω. Calculate the distance of the fault point from the test end.

Where,
R2 is the resistance connected to the faulty core in ohm
R2 is the resistance of the resistor connected to the sound core in ohm

R1 Distance of fault location (Lx) = R2/(R1 + R2)*(2*L)
= (15/60)*600
= 150 m

An electric potential field is produced in air by point 1 μC and 4 μC located at (-2, 1, 5) and (1, 3, -1) respectively. The energy stored in the field is

Recently, India signed first ever term contract to import crude oil with which country?

___ is the short time reduction in the rms voltage between 0.1 to 0.9 p.u for a duration of ___

Voltage sag:
It is usually associated with system faults but can also be caused by energization of heavy loads or starting of large motors.
Voltage sag is the short reduction in the RMS voltage between 0.1 to 0.9 pu for a duration of 0.5 cycle to 1 minute

In underground cables, the electrostatic stress is ___ at contactor surface and ___ at the sheath.

The electrostatic stress in a cable is not uniformly distributed.
The potential gradient is inversely proportional to the distance from the centre of the cable.
Hence, it will be maximum (gmax) at the surface of the conductor and goes on decreasing until it becomes minimum (gmin) at the surface of the sheath.
That means electrostatic stress in the dielectric of a cable is maximum at the surface of the conductor and minimum at the surface of the sheath.