Regulator Systems and Voltage Control Quiz

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Questions and Answers

What is the maximum number of consecutive tap changes that can occur after the time-delay period?

5 (correct)

In the voltage averaging mode, what triggers the activation of the time-delay circuit?

When the load voltage goes out of band (correct)

When the average voltage is reached

When the load voltage is too high

When the timer is reset

How is the timer decremented in the time integrating mode?

By 1 second for every 1.1 seconds elapsed

It does not decrement at all

By 0.1 seconds for every second elapsed

By 1.1 seconds for every second elapsed (correct)

What action occurs when the output voltage (V2) is low during reverse power flow?

The PT senses the low voltage and an increase in series winding is implemented Signup and view all the answers

What condition must be met for the timer to reset in the voltage averaging mode?

The voltage must remain in-band for at least 10 continuous seconds Signup and view all the answers

What is the primary function of the potential transformer in a regulator system?

To provide voltage proportional to the circuit voltage for control Signup and view all the answers

Which component is responsible for minimizing voltage swings due to changes in load current?

Line Drop Compensator Signup and view all the answers

How does the line drop compensator affect the voltage at the regulator's output during full load conditions?

It increases the voltage output Signup and view all the answers

What action does the voltage sensor take when the detected voltage is outside the set bandwidth?

It prompts the control to adjust the output voltage Signup and view all the answers

What is the purpose of adding a time delay in the regulator's operation?

To allow the regulator to ignore brief voltage changes Signup and view all the answers

What is the potential transformer connected to in the regulator system?

The load side of the regulator Signup and view all the answers

What voltage levels does the regulator maintain during no load conditions?

7200V Signup and view all the answers

Which of the following best describes the role of the bandwidth in a voltage sensor?

It sets the tolerance range within which the output should vary Signup and view all the answers

What is the voltage level range for the CL-2 AVR control?

105-135 Signup and view all the answers

Which control type has the longest time delay range in seconds?

CL-4C Signup and view all the answers

Which option correctly describes the operational features of the CL-5A control?

Electronic operations counter Signup and view all the answers

Which control does not include a supervisory ON/OFF switch?

CL-4C Signup and view all the answers

Which AVR control type has an LCD display?

Both B and C Signup and view all the answers

What is the voltage bandwidth range of the CL-5A control?

1-6 Signup and view all the answers

What unique feature does the CL-5A control have concerning manual control switches?

Auto/Remote-OFF-Manual switch Signup and view all the answers

Which control has a data port available?

Both B and C Signup and view all the answers

Which voltage range is typical for the input voltage of the CL-5A control?

80-137 V Signup and view all the answers

Which feature is present in all Cooper AVR controls mentioned?

Motor fuse Signup and view all the answers

What happens when the voltage from Source B is low in reverse power flow operation?

The control signals the AVR to raise the voltage by increasing T2. Signup and view all the answers

Which of the following is a standard feature in newer AVR controls for managing reverse power flow?

Reverse Power Flow Detector Signup and view all the answers

In the equation involving Source A and Source B, what remains constant during the reverse sensing operation?

T1 Signup and view all the answers

What is the primary purpose of the turns ratio in the context of reverse power flow?

To balance the voltages V1 and V2. Signup and view all the answers

Which mode is NOT mentioned as a typical reverse sensing mode in AVR controls?

Variable Lock Signup and view all the answers

If the AVR is connected for normal regulation but fed from Source B, which of the following outcomes can occur?

V1 must decrease as T2 increases. Signup and view all the answers

What is the role of an AVR in handling reverse power flow?

To sense and adjust for changes in voltage levels. Signup and view all the answers

Which control method does the SM-3 model use for manual control switches?

Auto-Manual Signup and view all the answers

How does the operations counter differ between GE's VR-1 and SM-3 models?

VR-1 has a mechanical counter; SM-3 has an electronic counter. Signup and view all the answers

Which model includes a data port?

GE's SM-3 Signup and view all the answers

What feature is unique to the Siemens MJ-XL model compared to MJ-3A?

Supervisory ON/OFF switch Signup and view all the answers

What is the maximum time delay for the SM-3 model?

180 seconds Signup and view all the answers

Which feature is found in both GE's AVR controls and Siemens controls?

External power terminals Signup and view all the answers

What is the voltage bandwidth range of the GE VR-1 model?

1.5-3 Signup and view all the answers

Which model does not have an LCD display?

Siemens MJ-3A Signup and view all the answers

What type of fuse is present in both the GE SM-3 and the Siemens MJ-XL models?

Panel fuse Signup and view all the answers

What is the primary purpose of voltage limiting in a regulator?

To place both a high and low limit on the output voltage Signup and view all the answers

How does the Automatic Load Bonus feature affect regulation?

It limits the range of regulation at high current levels Signup and view all the answers

Which harmonics are included in the THD measurement for the SM-3 control?

1-31st harmonic Signup and view all the answers

What loading percentage corresponds to 5% maximum regulation in the Load Bonus capability?

160% Signup and view all the answers

What should always be done before by-passing a regulator?

Ensure the regulator is in neutral Signup and view all the answers

Which of the following statements is true regarding series winding protection and lightning protection?

Series winding protection is different from lightning protection Signup and view all the answers

What is the potential risk of by-passing a regulator at the minimum raise or lower position?

It can result in maximum fault current due to low impedance Signup and view all the answers

What is the purpose of the drag hand reset button?

To reset the position indicator solenoid Signup and view all the answers

Study Notes

EENG 105: Distribution System & Substation Design - Topic 5

Topic: Voltage Regulators, Voltage Drop Calculations, Shunt Capacitor Placement, Voltage Regulating Transformers, Tap Changers

Voltage Regulators

Definition: A system designed to automatically maintain a constant voltage.
Design: Can use simple feed-forward design, or include negative feedback, using electromechanical or electronic components.

Automatic Voltage Regulators (AVRs)

Mechanism: A tap-changing autotransformer that continuously monitors output voltage and adjusts taps to achieve desired voltage.
Regulation Range: Adjusts line voltage from 10% raise (boost) to 10% lower (buck) in approximately 5/8 steps.

Reasons for Installing AVRs

Improve System Voltage: Maintain consistent voltage levels.
Enhance Quality of Service: Stable voltage for reliable operation.
Meet Regulatory Standards: Adherence to industry regulations.

Effects of AVRs on Voltage Problems

Problems Solved: Undervoltage, overvoltage, unbalanced voltage.
Problems Not Solved: Voltage sags, swells, flickers/fluctuations.

Functions Performed by AVRs & Capacitor Banks

Function	AVR	Capacitor Bank	Comments
Raise/Lower Voltage	Yes	Yes*	*Mechanism of operation, switched on/off effect
Raise Voltage on Source Side	No	Yes	*Produces small changes in voltage if bank is small size
Small Voltage Step Control	Yes	Yes*	*Large number of switching operations can deteriorate capacitor switch, results in losses on output, with increased voltage
Reduce Losses	No	Yes*	*Reduction in losses, increased voltage on the output side of the regulator
Reduce Thermal Loading	No	Yes	*Reduced thermal loading; increased voltage on Output
Raise System Loading Capabilities	Yes*	Yes	*Increased loading capability on the output; not on the input

Typical AVR Locations

Transformer Banks: Primary and secondary sides.
Feeder Lines: Main lines and middle points.
Customer Tapping Points: Customized connection points for customers.

Voltage Regulator Operating Sequence

Potential Transformer (PT): Measures and provides voltage proportional to the line voltage for control.
Line Drop Compensator: Minimizes voltage fluctuations due to load current changes.
Voltage Sensor: Compares input voltage to a preset value and triggers corrective voltage adjustments whenever the output voltage is not within bandwidth.
Time Delay: Ignores brief voltage variations and activates voltage adjustments continuously only when variations persist over a defined period, also prevents continuous tapping due to short-lived fluctuations.
Tap Changer / Tap-Changing Motor (Motor): Corrects the voltage by changing tap settings.

Major Components of an AVR

Source Bushing
Load Bushing
Neutral Bushing
Series Arrester: Protects from surges and strikes.
Position Indicator: Shows the tap changer's position.
Electronic Control: Maintains voltage.

Typical Features of an Electronic Control

Voltage Level Selector
Bandwidth Selector
Time Delay Selector
Band-edge Indicator
Line Drop Compensation Selectors
Neutral Indicator Light
Draghand Reset / Neutral Light Test Switch
Control Switch (Manual/Auto)
External Power Terminals
Voltmeter Terminals
Motor and Panel Fuses
Data Port
LCD Display (showing settings and values)
Keypads

Control Operating Modes

Sequential: Correcting voltage fluctuations sequentially, one tap change at a time, using precise timing in response to out-of-band conditions.
Non-Sequential: Tap change occurs once and time delay is reset.
Time Integrating: Timer counts the duration of out-of-band conditions before initiating a tap change.
Voltage Averaging: Determines an average of the voltage during a period of time and corrects based on that average, it's useful when there are various small voltage fluctuation over a duration

Reverse Sensing Modes

Locked Forward: The control operates in the forward direction regardless of reverse power flow.
Locked Reverse: The control operates in the reverse direction regardless of the forward power flow.
Bi-directional: The control operates either in the forward or reverse direction depending on the direction of the real components.

Voltage Drop Calculation

Formula: Volts = Length × Current × 0.017 / Area (Length in meters; Current in amps, Area in square millimeters).
Temperature Correction: The formula needs to be corrected for variable wire temperatures.

Special Features of AVR Controls

Voltage Limiting : Protects electrical equipment from excessive voltages.
Voltage Reduction: Corrects voltage when demand exceeds capacity
Automatic Load Bonus : Adjusts voltage regulation for when fixed currents are reached in forward and reverse operation.
Harmonic Measurement: Measures harmonics and Total Harmonic Distortion.

Load Bonus Capability

Definition: The ability of a AVR to work with higher than nameplate current loads in the regulated range.
Rating: A chart detailing the percentage of rated loading in terms of maximum regulation attainable for different loads.

Effect of Load Bonus Settings on AVR Capacity

Parameter Table: A table shows the load current ratings at different percentage-based, regulated ranges.

Important Reminders

Series Winding Protection: The method for defending the series winding is separate from lightning protection.
Neutral Position: Always ensure that the regulator is in the neutral position before bypassing it.
Drag Hand Reset Button: Avoid prolonged holding of the drag-hand reset button to prevent potential damage.

Typical Features of an Electrical Control

Detailed features, including those specific to different types of controls (e.g., CL-2, CL-4C, CL-5A, and SM-3). These include voltage level, bandwidth, time delay, LDC (Line Drop Compensation), various indicators (band-edge, neutral indicator), controls (switches, switches, and pushbuttons).

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Description

Test your understanding of regulator systems and their functions with this quiz. Explore topics such as time-delay circuits, voltage averaging modes, and the role of potential transformers. Perfect for those studying electrical engineering principles related to voltage control.