Review: Protective Relaying Midterm Exam

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What are the three electrodes usually found in a thyristor?

Emitter, collector, and base

Cathode, diode, and resistor

Positive, negative, and neutral

Anode, cathode, and gate (correct)

Which relay can differentiate internal and external faults effectively?

Thermal relay

Low impedance relay

Static differential relay

High impedance relay (correct)

What is the main role of the bus bar in a supply system?

Ensure voltage balance

Prevent current transformer saturation

Carry fault currents safely (correct)

Interrupt the power supply

What is the purpose of using a linear coupler instead of conventional current transformers in protective relaying?

To overcome saturation in large fault currents Signup and view all the answers

Which type of relay is commonly used for protecting generators and transformers from internal faults?

Static differential relay Signup and view all the answers

How is the connection between contacts and a bimetallic strip made in a simplest thermal relay?

By a spring Signup and view all the answers

What is the operating value of a phase comparator of a mho distance relay scheme?

ILZR−ZL Signup and view all the answers

Which type of supply does the Induction type relay work on?

Alternating current (AC) Signup and view all the answers

What component is considered the 'heart' of a static relay?

Measuring element Signup and view all the answers

In a directional power relay, when does the relay operate?

When power flows in a specific direction Signup and view all the answers

What does the Definite or Fixed time function element provide in relays?

Defined time delay Signup and view all the answers

How does a differential relay operate?

When phasor difference exceeds a predetermined value Signup and view all the answers

What is the main factor that determines the operation of distance relays?

Ratio of voltage and current Signup and view all the answers

In an impedance relay, which type of torque is produced by the voltage element?

Reset torque Signup and view all the answers

Why are static relays considered to place a reduced burden on protective transformers compared to electromagnetic relays?

Lower VA requirements Signup and view all the answers

What is a key requirement for static relays in terms of auxiliary supply?

Surge suppression Signup and view all the answers

Which type of relay is known as the simplest type of relay?

Electromagnetic attraction relay Signup and view all the answers

What is the term used for overcurrent level detectors in relays?

Fault current level detectors Signup and view all the answers

What type of relay employs active semiconductor devices like diodes and transistors?

Static relay Signup and view all the answers

In distance time relays, what is the time of operation proportional to?

Fault distance Signup and view all the answers

Which component pivots when attracted towards the coil in a directional relay?

Plate made of iron Signup and view all the answers

What type of relay can withstand overload for minutes or hours depending on the magnitude of the overload?

Thermal relay Signup and view all the answers

Which relay operates based on the comparison of phase angles and magnitudes of currents entering and leaving the system?

Current differential relay Signup and view all the answers

In a reactance relay, how is the operating torque obtained?

By current Signup and view all the answers

What is the function of the filter circuit in static relays after rectifiers?

Smoothing of d.c. voltage Signup and view all the answers

What is the restraining value of a phase comparator in a reactance distance relay scheme?

ZRIL Signup and view all the answers

What is a limitation of static relays?

Variation of characteristic with temperature and age Signup and view all the answers