Relay Protection Quiz

What is the purpose of back up protection?

• To increase the speed

• To increase the reach

• To leave no blind spot

• To guard against failure of primary

Differential relays use the principle of:

• Time-domain comparison

• Frequency-domain analysis

• Current magnitude comparison between incoming and outgoing feeders

• Monitoring power factor

Distance relays measure:

• Impedance of the protected line

• Voltage at different points along the line

• Current flowing through the line

• Power factor of the line

Which of the following factors is NOT considered when setting the pickup current for an overcurrent relay?

• Nominal load current of the protected equipment

• Time-current characteristic curve of the relay

• Fault current levels expected during various fault scenarios

• Ambient temperature of the relay installation

How does a directional impedance relay distinguish between fault current direction and load current?

• Comparing phase angles of voltage and current

• Measuring active and reactive power components

• Analyzing the impedance seen from the relay location

• Checking the polarity of the current waveform

What is the primary function of a directional power relay in a protection scheme?

• Measuring instantaneous power flow direction

• Detecting reverse power flow from protected equipment

• Tripping in response to unbalanced phases and power swings

• Initiating corrective actions for undervoltage or overvoltage conditions

Which characteristic of a directional overcurrent relay determines the angle range for fault detection?

• Pickup current setting

• Time dial setting

• Operating characteristic curve

• Directional element angle setting

How can the tripping characteristic of an inverse-time overcurrent relay be adjusted to provide optimal coordination with upstream and downstream relays?

• By selecting the appropriate CT ratio for current scaling.

• By modifying the pickup current setting of the relay.

• By choosing the inverse-time curve characteristic with suitable time multiplier.

• All of the above

A Mho relay is a

• Voltage restrained directional relay

• Voltage restrained over current relay

• Directional restrained over-current relay

• Directional restrained over voltage relay

Which of the following relay has inherent directional characteristic?

• Mho

• Reactance

• Impedance

• None of the above