Automatic Voltage Regulators (AVR) Quiz

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Questions and Answers

Which of the following features is NOT available in GE's AVR Control VR-1?

Data Port (correct)

Supervisory ON/OFF Switch (correct)

Neutral Indicating Light

LCD Display (correct)

What type of operations counter is used in the Siemens MJ-XL AVR controls?

Digital

Mechanical

Analog

Electronic (correct)

In terms of voltage levels, what is the range for the GE AVR Controls?

105-135 volts (correct)

110-140 volts

120-150 volts

100-130 volts

Which AVR control features a supervisory ON/OFF switch?

Siemens MJ-XL Signup and view all the answers

What is the main purpose of a Voltage Regulator?

To automatically maintain a constant voltage Signup and view all the answers

Which method is NOT used by Automatic Voltage Regulators (AVRs) to adjust voltage?

Artificially boosting voltage from the source Signup and view all the answers

What types of voltage problems can AVRs effectively solve?

Undervoltage Signup and view all the answers

Which function is unique to Capacitor Banks compared to AVRs?

Capable of reducing thermal loading Signup and view all the answers

What is one of the reasons for installing AVRs?

To improve the quality of service Signup and view all the answers

Which statement about AVRs and Capacitor Banks is true?

AVRs can perform switching operations without frequent wear Signup and view all the answers

What voltage problems are AVRs incapable of addressing?

Voltage sags Signup and view all the answers

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

To provide a voltage for the tap changing motor Signup and view all the answers

How does a line drop compensator affect voltage during full load conditions?

It increases the output voltage of the regulator Signup and view all the answers

What role does the voltage sensor play in the regulation process?

It compares the voltage against a set tolerance Signup and view all the answers

What is the purpose of the time delay feature in a voltage regulator?

To ignore brief and self-correcting voltage variations Signup and view all the answers

Which of the following situations would a line drop compensator address effectively?

Sustained voltage drops during peak load Signup and view all the answers

What happens when the voltage detected by the sensor is outside the defined bandwidth?

The control will adjust the output voltage Signup and view all the answers

What does the term 'bandwidth' refer to in a voltage sensor context?

The range of acceptable voltage levels around a set point Signup and view all the answers

Which statement accurately reflects the line voltage without a line drop compensator under full load conditions?

The output will drop to 6800V Signup and view all the answers

Why is it important for the regulator to correct only prolonged voltage variations?

To prevent unnecessary wear on the tap changing motor Signup and view all the answers

What occurs when V2 is low during reverse power flow?

The AVR raises the voltage by increasing T2. Signup and view all the answers

Which component remains constant during the adjustment in reverse power flow?

T1 Signup and view all the answers

What is the relationship expressed in the equation represented?

V1 & T1 are dependent on V2 & T2. Signup and view all the answers

What kind of detector is used for reverse power flow in older types of AVR control?

Reverse Power Flow Detector kit Signup and view all the answers

What happens to the load side voltage during a low V2 situation?

It decreases. Signup and view all the answers

Which mode is NOT mentioned as a reverse sensing mode?

Dynamic Regulation Signup and view all the answers

What feature is standard in newer AVR controls related to reverse power flow?

Reverse Power Flow Detector Signup and view all the answers

In reverse power flow situations, what is the equation used for analyzing the power relationship?

V1 * T1 = V2 * T2 Signup and view all the answers

What is the role of T2 when V2 is low?

It increases to maintain voltage balance. Signup and view all the answers

What is the likely effect on power flow when the AVR incorrectly interprets the source voltage?

Potential voltage instability. Signup and view all the answers

What primary function does the potential transformer serve in the voltage regulator operating sequence?

It supplies a signal proportional to the line voltage. Signup and view all the answers

What triggers the tap-changing motor to operate in the voltage regulator sequence?

A signal after the voltage is out of the preset band for a certain time. Signup and view all the answers

Which component modifies the signal from the potential transformer in the voltage regulator?

The line drop compensator. Signup and view all the answers

How does the voltage sensor contribute to the voltage regulation process?

It signals when the voltage exceeds limits. Signup and view all the answers

What is the desired outcome after the operation of the tap-changing motor?

To return sensed voltage back within the bandwidth. Signup and view all the answers

In the operating sequence, what happens if the voltage remains outside the preset band?

A signal is sent to the tap-changing motor. Signup and view all the answers

What role does the time delay play in the voltage regulation process?

It determines how quickly the motor responds to voltage changes. Signup and view all the answers

Which component is responsible for detecting when the voltage is out of the preset band?

The voltage sensor. Signup and view all the answers

What occurs after the tap-changing motor begins correcting the voltage?

It continues changing taps until the sensed voltage is within the bandwidth. Signup and view all the answers

What is a likely consequence of improper line drop compensator settings?

Voltage fluctuations outside acceptable limits. Signup and view all the answers

Study Notes

EENG 105: Distribution System & Substation Design - Topic 5

Course: EENG 105
Topic: Voltage Regulators, Voltage Drop Calculations, Shunt Capacitor Placement, Voltage Regulating Transformers, Tap Changers
Instructor: Engr. Ernick R. Romes, Faculty, CvSU - EE

Voltage Regulators

A voltage regulator automatically maintains a constant voltage.
Design options include simple feed-forward designs or negative feedback systems.
Electromechanical mechanisms or electronic components can be used.

Automatic Voltage Regulators (AVRs)

AVRs utilize tap-changing autotransformers.
They continuously monitor output voltage and adjust taps to achieve desired voltage.
Voltage regulation typically ranges from a 10% increase (boost) to 10% decrease (buck) in 32 steps, approximately 5/8 steps.

Reasons for Installing AVRs

Improve system voltage
Enhance service quality
Meet regulatory standards

Effects of AVRs on Voltage Problems

Problems Solved: Undervoltage, Overvoltage, Unbalanced voltage
Problems Not Solved: Voltage sags, Voltage swells, Voltage Flickers/Fluctuations

Functions Performed by AVRs & Capacitor Banks

Function	AVR	CAP	Comments
Can raise and lower voltage	Yes	Yes*	Affects by being switched on or off
Can raise voltage on source side	No	Yes	Produces small voltage changes if bank size is small
Capable of small voltage step control	Yes	No*	Produces small changes in voltage if bank size is small
Capable of many switching operations with infrequent inspection	Yes	No*	Rapid deterioration of capacitor switch contacts with many switching operations per day
Reduces losses in the system	No*	Yes	Some reduction in losses likely result on the output side by virtue of increased voltage
Reduces thermal loading	No	Yes
Raises system loading capability	Yes*	Yes	Raises loading capability on output side but not necessarily on input side

Typical AVR Locations

Primary side of power transformer bank
Secondary of power transformer bank
Main line of feeder
Middle of feeder
Customer tapping point

Voltage Regulator Operating Sequence

Potential transformer supplies a signal proportional to current line voltage to the control
This signal is modified by the line-drop compensator settings
Voltage sensor signals when the voltage is out of the bandwidth
Tap-changing motor adjusts taps until sensed voltage again is within the bandwidth
Tap-changing continues until voltage is again within the bandwidth

Major Components of an AVR

Source bushing
Load bushing
Neutral or SL bushing
Series arrester
Position indicator
Electronic control

Position Indicator

Mechanically linked to the tap-changing switch
Indicates actual tap-changer position via a yellow pointer
Displays maximum and minimum positions attained during raising and lowering operations
Allows operator to set load bonus

Series Arrester

A bypass arrester connects across the series winding
Constrains the voltage developed across the series winding during faults like lightning strikes, surges and line faults.

Typical Features of an Electronic Control

Voltage Level Selector
Bandwidth Selector
Time Delay Selectors
Band-edge Indicator
Line Drop Compensation Selectors
Neutral Indicating Light
Draghand Reset /Neutral Light Test Switch
Internal /External Power Switch
External Power Terminals
Voltmeter Terminals
Motor & Panel Fuses
Operations Counter
LCD Display
Keypads
Data Port

Control Operating Modes

Sequential: Control responds to out of band conditions by sequentially changing taps until voltage returns to the targeted range.
Non-Sequential: Control responds by changing one tap and then resetting the time delay before another change
Time Integrating: Works like sequential mode, but time delay is decremented until zero when voltage returns to the band.
Voltage Averaging: Control monitors and averages instantaneous load voltage; computes tap changes to bring average voltage back to the set voltage; timer resets when voltage is in band for 10 seconds.

Reverse Power Flow

When power flow reverses, the PT senses the change and prompts control adjustments for corrective action.
This prevents damage when power flow reverses.

Reverse Sensing Modes

Locked Forward: Control operates solely in forward direction while idling at last tap position.
Locked Reverse: Operates solely in reverse direction while idling at last position.
Bi-directional: Operates in forward direction when current exceeds user-defined forward threshold and in reverse direction when current exceeds user-defined reverse threshold.

Regulator Connection Diagrams

Various diagrams illustrating regulator setups in 3-phase and single-phase circuits: 3-phase 4-wire circuits using Wye connection, 3-phase 3-wire circuits using Delta connections, and more.

AVRs Used by MERCALCO

Description of specific AVRs employed by MERALCO.

The Cooper/McGraw Edison VR-32 Step-Voltage Regulator

Types of Cooper/McGraw Edison VR-32 step-voltage regulators (e.g., CL-2, CL-4C, CL-5A).

Features of Cooper's AVR Controls

Detailed table comparisions of functionality for each Cooper regulator models.

Cooper AVR with CL-2A, CL-4C, CL-5A Control

Diagrammatic detail and explanations of each control type

The GE Type VR-1 Step-Voltage Regulator

Types of GE voltage regulators (e.g., VR-1, SM-3).

Features of GE's AVR Controls

Detailed table comparisions of functionality for each GE regulator models.

The Siemens Type JFR Step-Voltage Regulator

Description of Siemens JFR regulators. This includes units like 250 kVA, 7.62 kV and 400 kVA, 19.92 kV) types.

Nameplate of a Siemens, Cooper, and GE VR-32, VR-1, and CL-5A AVR

Visual representation and details of important information contained on the nameplates.

Voltage Drop Calculation

Formula for calculating voltage drop in a copper wire given length, current, and cross-sectional area: Volts = Length x Current x 0.017 / Area
Factors that affect voltage drop, like temp and insulation

Special Features of AVR Controls

Voltage Limiting/First House Protector: Sets high and low limits on the output
Voltage Reduction: Adjustment to reduce voltage during periods of high demand exceeding capacity
Automatic Load Bonus: Limits regulation range when current exceeds the set limit.
Harmonic Measurement: Measures harmonics (3rd, 5th, 7th, 9th, 11th. 13th, and up to 31st or more).

Load Bonus Capability

Description of the ADD and VARI-AMP settings, along with voltage drop related to higher loads.
Table of load percentages and associated maximum voltage regulation.

Effect of Load Bonus Setting on AVR Capacity

Ranges and ratings in amperage for different load capacities for different Cooper AVR models.

Important Reminders

Series winding protection, differing from lightning protection, is crucial
Always ensure regulators are in neutral prior to bypass operations
Do not hold drag hand reset for more than five (5) seconds.

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Description

Test your knowledge on Automatic Voltage Regulators (AVR) and their functionalities, including features, operations, and voltage range. This quiz covers various aspects of GE and Siemens AVR controls, as well as their effectiveness in solving voltage problems. Perfect for those looking to deepen their understanding of electrical engineering concepts related to voltage regulation.