Power Distribution Flashcards
7 cards from real EETC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Power Distribution flashcards as text
What is the primary purpose of a distribution transformer's tap changer?
Answer: To adjust the output voltage to compensate for load variations
Tap changers adjust the transformer turns ratio to maintain proper secondary voltage as load and primary voltage fluctuate.
In a radial distribution system, what is the main disadvantage compared to a loop or network system?
Answer: Loss of service to all customers downstream of a fault
In a radial system, a single fault interrupts power to all customers downstream of the fault point since there is only one supply path.
Which conductor arrangement is used in most North American overhead distribution systems serving residential areas?
Answer: Wye four-wire multigrounded neutral
The multigrounded wye four-wire system is standard in North America because it provides both single-phase 120/240V service and neutral grounding at multiple points.
A capacitor bank installed on a distribution feeder primarily improves which system parameter?
Answer: Power factor and reduces reactive power demand
Shunt capacitor banks supply reactive power locally, improving power factor, reducing current draw, and decreasing line losses.
What does the term 'feeder' refer to in power distribution?
Answer: The medium-voltage circuit leaving a substation to serve distribution loads
A distribution feeder is the medium-voltage (typically 4–35 kV) circuit that originates at a substation and carries power to distribution transformers serving customers.
Voltage unbalance in a three-phase distribution system primarily causes which problem in three-phase motors?
Answer: Overheating and reduced motor efficiency
Voltage unbalance creates negative-sequence currents in motors that produce opposing torque and significant heat, reducing efficiency and shortening motor life.
What is the function of a sectionalizer in a distribution system?
Answer: To count fault current operations and open after the recloser locks out
A sectionalizer counts the number of fault interruptions by an upstream recloser and opens during a dead interval after a preset count, isolating the faulted section.