WorksheetsElectrical Grid Situational-Based MCQs- Advanced to Expert
Total questions: 40
Worksheet time: 20mins
A sudden disconnection of a large generator from the grid results in:
Frequency increase
Frequency drop and underfrequency protection activation
Voltage overshoot
Synchronization
In an interconnected grid, a tie-line helps:
Store power
Transfer power between regions and maintain frequency balance
Lower frequency
Protect SCADA
In case of fault current exceeding the rating of a circuit breaker, what system is added?
Relay
Current transformer
Backup breaker or series reactor
Fuse
What is the key parameter monitored by an Automatic Generation Control (AGC)?
Power factor
Frequency deviation and tie-line power
Line voltage
Breaker status
In real-time grid operations, Area Control Error (ACE) refers to:
Energy difference
Difference in scheduled and actual power flow and frequency
Power loss
Voltage error
A wind turbine generator connected to the grid must synchronize:
Only voltage
Voltage, frequency, and phase angle
Just current
Temperature
A large-scale solar PV plant output is fluctuating due to cloud cover. How does the grid handle this?
Disconnect PV
Use spinning reserves or battery storage
Increase fault level
Bypass transformer
Frequency relays in the grid are used to:
Control voltage
Shed load during underfrequency to avoid blackout
Detect overcurrent
Maintain PF
What is load frequency control responsible for?
Voltage control
Managing real power balance and system frequency
Reactive power sharing
Ground fault detection
What type of compensation is applied to long transmission lines to prevent voltage drop?
Series capacitive compensation
Shunt inductance
Line reactor
Open circuit
In a smart grid, Advanced Metering Infrastructure (AMI) enables:
Voltage transformation
Bi-directional communication and real-time monitoring of usage
Harmonic elimination
Load dumping
The function of a synchrophasor (PMU) in grid monitoring is:
Load switching
Real-time phasor measurement of voltage and current for dynamic stability monitoring
Energy billing
Transformer tap change
In case of islanding detection, what method is most commonly used?
Overcurrent
Voltage sag
ROCOF (Rate of Change of Frequency) or impedance measurement
Thermal overload
If a grid suffers low voltage due to high demand, how is it mitigated?
Add shunt capacitors or reduce load
Lower frequency
Disconnect generators
Turn off SCADA
In an HVDC link, the power flow is controlled by:
Transformers
Phase angle
Converter control (alpha angle or firing angle)
AVR
The typical communication protocol in substation automation is:
Modbus
IEC 61850
BACnet
RS-232
What does the term 'grid inertia' refer to?
Load flow stability
Resistance to change in frequency due to stored kinetic energy in rotating machines
Synchronizing torque
Voltage regulation
What is the disadvantage of a weak grid?
Easier to control
Prone to voltage and frequency instability under fluctuating loads or renewable integration
Less fault current
More efficiency
In reactive power compensation, STATCOM is used for:
Power measurement
Dynamic reactive power injection for voltage control
Short circuit detection
Power theft monitoring
A transformer under high load has reduced voltage at the secondary. What compensates it automatically?
Earth wire
On Load Tap Changer (OLTC)
Overcurrent relay
SCADA
A substation transformer frequently trips during heavy thunderstorms. What could be the most effective long-term mitigation?
Use larger circuit breakers
Install surge arresters and ground mesh improvement
Reduce connected load
Increase OLTC tap
In a large power system, when a high-voltage transmission line trips, the system experiences transient oscillations. What equipment helps mitigate this?
AVR
Power System Stabilizers (PSS)
OLTC
Bus coupler
When a generator is operated in voltage control mode in a weak grid, it may cause:
Stability improvement
Overvoltage and voltage instability
Reactive power loss
Frequency drift
If two large regions with differing frequencies are interconnected suddenly, what could result?
Blackout due to power swings or frequency instability
Increased efficiency
Harmonic cancellation
Reduced losses
In a fault-tolerant grid architecture, the purpose of meshed transmission topology is:
Reduce fault current
Improve voltage drop
Enhance reliability through alternative power paths
Simplify control
Wide-Area Monitoring Systems (WAMS) primarily use PMUs for:
Protection operation
Data acquisition for real-time oscillation and stability analysis
Switchgear diagnostics
Power factor correction
During solar eclipse, large-scale PV generation drops suddenly. The grid operator should:
Ignore the event
Increase spinning reserve in anticipation
Shut down loads
Isolate solar farms
Load encroachment is a problem in:
Transformer saturation
Distance relay misoperation due to heavy loading
Fault clearing time
Islanding detection
A long 400 kV line exhibits Ferranti effect under light load. What’s the remedy?
Increase line length
Shunt reactor installation at receiving end
Series capacitor
Transformer replacement
If a region in the grid exhibits low inertia due to high penetration of renewables, how can inertia be synthetically added?
Increase battery banks
Use synchronous condensers or grid-forming inverters
Reduce transmission line impedance
Increase transformer rating
An inter-area oscillation in a grid is best analyzed using:
OLTC trends
Synchrophasor data from multiple PMUs
Circuit breaker logs
Harmonic analyzer
Transient stability studies are performed to assess:
Steady-state efficiency
Ability of the system to maintain synchronism after a disturbance
Energy losses
OLTC step count
A converter-based wind farm connected to the grid behaves like:
An active load
A voltage source
A current source with limited fault contribution
A synchronous generator
Reactive power control at grid-level substations is essential to:
Increase frequency
Avoid voltage collapse and maintain voltage profile
Reduce PF
Reduce losses in transformer
What challenge arises when large-scale rooftop solar connects to low-voltage distribution grids?
Frequency dip
Reverse power flow and voltage rise
OLTC saturation
Overcurrent trip
Harmonics from nonlinear industrial loads are controlled using:
OLTC
Passive filters, active filters, or tuned reactors
Relays
Tap changers
In an HVDC back-to-back link, synchronization of frequency is:
Necessary
Not required since DC decouples frequency
Only for load sharing
Controlled by transformer
Virtual inertia from battery storage is provided by:
SOC control
Fast inverter response emulating inertial behavior
High current injection
Transformer tap
For fast fault detection in smart grids, what advanced technique is employed?
Time-domain reflectometry
Artificial intelligence on PMU data for pattern recognition
Infrared thermography
Circuit breaker aging
The coordination of overcurrent relays in a meshed grid must consider:
Current level only
Directionality, time grading, and backup paths
Only impedance
Cable insulation
