High Voltage Questions Worksheet Flashcards
True or False. A 25kV, URD HV cable will have stand and insulation shielding in its construction
True
True or False. For HV cables, the insulation thickness will increase with voltage increases
True
True or False. Extra high voltage cables will have a thermoset insulation in the middle channel of the cable
False. Liquid or gas
True or False. A common type of medium-voltage cable in general use today is Teck cable
True
True or False. Dielectric strength of a material is the ability of the dielectric to withstand electrical breakdown under the influence of frequency
False. Voltage stress
True or False. Dielectric strength will increase if a dielectric becomes heated
False. This weakens the insulation
True or False. XLPE is a thermoset plastic
True
True or False. IEEE classifies high voltage as 115,000 - 230,000V
True
True or False. Some large electric motors operate at voltages as high as 13.8kV
True
True or False. Most HV alternators generate electric power at voltages between 20kV and 40kV to reduce line losses
False. 10kV to 20kV
True or False. The voltages used in the transmission system are generally 60kV - 765kV for BC Hydro
False. 500kV max
True or False. PVC is a thermoplastic material
True
True or False. The conductor shield overcomes the problem of ionized air between the conductor strands
True
True or False. The insulation shield creates an equidistant radial flux in the insulation
True
True or False. If the insulation shield was constructed of lead it would also prevent the ingress of moisture into the cable
True
True or False. The grounded shield acts to protect life in the event of mechanical damage to the cable
True
True or False. 100% insulation is used in grounded systems, where ground faults are eliminated in no more than one hour
False. 133%
True or False. Cable armour provides HV cable with mechanical protection
True
True or False. A pothead is a termination method that has been traditionally used on shielded Teck power cables
False. PILC cables
True or False. Its better to have a creep age distance a little too long, as opposed to too short when terminating HV cable
True
True or False. Moisture and contaminants on the insulation could cause current tracking and flashover
True
True or False. Splicing a HV cable is considered more difficult than terminating a HV cable
True
True or False. A common reason for a HV splice to fail is air getting trapped in between layers of insulation
True
What is the process called when air breaks down and becomes a conductor?
Ionization
What represents a power loss in lines and can cause radio and TV interference?
Corona
What is is called when current tries to flow across insulation to ground?
Tracking
What is used on HV insulators and cable terminations to increase the creepage distance?
Skirting
The ability to withstand a very high voltage for short duration is called ________
Impulse voltages
What is created on the insulation surrounding a conductor due to an electrostatic field?
Electric stress
Created because the flux concentrations are decreasing with distance which means the stress on the insulation decreases with distance
Voltage gradient
The result of dust collecting on HV insulators or terminations
Flashover
Relates to the minimum separation required between energized HV conductors
Strike Distance
True or False. An electrostatic field is due to conductive air
False. Voltage
True or False. A radial system is an expensive form of HV supply for rural locations
False. It is the cheapest
True or False. A ring system is also called a loop system
True
True or False. A network system is essentially a loop system with additional interconnecting ties
True
True or False. The network system is used for supplying HV power to major airports
True
True or False. Lightning arresters are connected in parallel to the load
True
True or False. Reactors are connected in series to the load
True
True or False. Unit substations are common used for the supply of large industrial and commercial installations
True
True or False. A substation that contains HV equipment is usually located outdoors and includes disconnects, circuit breakers, power transformers, lightning arresters, etc
True
True or False. A radial system used for the supply of power for rural locations is the easiest to protect against overload and short-circuits
True
True or False. The loop system offers a higher degree of reliability than the radial system
True
True or False. A HV vault must be built of concrete and located so that at least one wall is an outside wall
True
