Transformers and Power Distribution Flashcards
6 cards from real 309A practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Transformers and Power Distribution flashcards as text
What is demand factor as applied to transformer sizing?
Answer: The ratio of maximum demand to total connected load
Demand factor is the ratio of the maximum demand of a system to the total connected load. It is always 1.0 or less, as not all connected loads operate simultaneously at full capacity.
What is the standard frequency for electrical power distribution in Canada?
Answer: 60 Hz
Canada, like the rest of North America, uses 60 Hz as the standard power distribution frequency. This affects motor speeds, transformer design, and all frequency-dependent equipment.
What protection does a ground fault relay provide in a transformer secondary distribution system?
Answer: Detection of current flowing to ground indicating insulation failure or contact with grounded surfaces
Ground fault relays detect current imbalances indicating current flowing to ground through a fault path, providing early warning of insulation deterioration and protection against ground faults.
What is the Canadian standard for transformer impedance marking?
Answer: Marked on the nameplate as percentage impedance at rated kVA
Canadian standards require the percentage impedance (%Z) at the transformer's rated kVA to be clearly marked on the nameplate. This is essential for calculating available fault current and coordinating protection.
What is the purpose of a load-break switch in a medium-voltage distribution system?
Answer: To safely open and close circuits under load conditions
Load-break switches can safely interrupt load current (but not fault current) in medium-voltage distribution systems, allowing equipment to be de-energized for maintenance without shutting down the entire system.
What is the maximum voltage for a low-voltage distribution system as defined by Canadian standards?
Answer: 750 V
Canadian electrical standards define low voltage as up to 750 V. Systems above 750 V are classified as medium or high voltage and require additional safety precautions and qualified personnel.