An admittance relay is categorized as what type of relay? __________ relay
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Answer: B. directional
Explanation
An admittance relay, commonly known as a mho relay, functions as a voltage-restrained directional relay. It measures system impedance and compares phase angles to determine fault direction. This directional capability makes it indispensable for protecting high-voltage transmission lines. Mho relays plot their operating characteristics on the complex impedance plane as a circle through the origin. Directional relays determine whether a fault is located in the forward or reverse direction. Distance protection schemes use admittance relays to clear faults rapidly within specific zones.
Long transmission line protection relies on mho relays to discriminate between internal and external faults. Power systems engineers use admittance relays to prevent unwanted tripping during heavy load conditions. Directional protection ensures selective fault isolation in complex interconnected electrical grids. Impedance is measured by the relay, but the classification describes it specifically as a directional relay. Non-directional relays lack the phase comparison needed to determine fault direction accurately. None of the above is incorrect because option B correctly identifies it as a directional relay.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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