WAZIPOINT Engineering Science & Technology: How to Improve Voltage Regulation in Power System?

Monday, October 2, 2023

How to Improve Voltage Regulation in Power System?

Voltage Regulation
Voltage Regulation Improve in Transmission Lines

If we consider how the high voltage in the transmission lines should regulate, then the answer is with a transformer.

But if we consider how the voltage is increased in an already operating transmission line this can be done by couplers in the transformer in or by decreasing the number of turns in the transformer, thereby raising or lowering the voltage.

Under heavy load conditions, more current is drawn from your TL and this increases the voltage drop V=IZ to increase the voltage at the sending end there are some methods that can be used:

Method-1 changes Z, whereas method-2 changes current I. And these are what voltage drop depends on Vdrop=IZ. Decreasing voltage drop means raising the voltage at the receiving end. 

  1. You can add series capacitors to your TL with each phase at some distance from your line. The capacitive reactance Xc will remove part of the inductive reactance Xl and hence the total impedance Z will decrease. And when Z decreases that means your voltage will rise because the voltage drop now is small.
  2. Using shunt capacitors, using shunt capacitors at receiving end or at selected points across your TL will compensate part of the inductive reactance, and hence will decrease the current that flows in the TL and this will decrease the voltage drop and hence increases the voltage. These shunt capacitors, in fact, act like power factor correctors, they increase pf and then decrease the current: I=P3√∗V∗pf as you see when pf increases the current will decrease from this equation.

In most cases, the shunt capacitors are used at the receiving end of the TL in the substations.

How to Improve Voltage Regulation in Power Distribution Line

Mainly controlling the voltage level in the distribution system voltage regulation is improved. The possible way to improve voltage regulation in an electrical power distribution system network is as below:

1. Use of generator voltage regulators;

2. Application of voltage-regulating equipment in the distribution substations;

3. Application of capacitors in the distribution substation;

4. Balancing of the loads on the primary feeders;

5. Increasing feeder conductor size;

6. Changing of feeder sections from single-phase to multiphase;

7. Transferring loads to new feeders;

8. Installing of new substations and primary feeders;

9. Increase of primary voltage level;

10. Application of voltage regulators on the primary feeders;

11. Application of shunt capacitors on the primary feeders;

12. Application of series capacitors on the primary feeders;

To improve voltage regulation in a power distribution line, which refers to maintaining a stable voltage level within an acceptable range, you can consider the following methods:

Voltage Control at Substations: Implement automatic voltage control (AVC) systems at distribution substations. AVC systems monitor the voltage levels and adjust tap settings on transformers or voltage regulators to maintain the desired voltage within the prescribed limits.

Reactive Power Compensation: Install reactive power compensation devices such as capacitor banks at strategic locations along the distribution line. Capacitor banks help offset the reactive power demand of loads, thereby reducing voltage drop and improving voltage regulation.

Voltage Regulators: Utilize voltage regulators at critical points in the distribution system. These regulators can adjust the voltage levels based on load conditions, compensating for voltage variations and ensuring a stable voltage supply.

Load Balancing: Properly distribute the loads across different phases and feeders to achieve load balance. Load imbalance can lead to uneven voltage distribution and voltage drop, adversely affecting voltage regulation. Load balancing can be achieved by redistributing loads or implementing load shedding techniques.

Voltage Drop Calculation: Conduct voltage drop calculations for the distribution line to identify areas with excessive voltage drops. By identifying these locations, appropriate measures such as cable size upgrade or voltage regulation devices can be implemented to mitigate voltage drop and improve voltage regulation.

Power Factor Improvement: Encourage power factor improvement for industrial and commercial customers. Low power factor can lead to increased reactive power demand and voltage drop. By improving power factor through power factor correction techniques, such as capacitor banks, the reactive power demand can be reduced, improving voltage regulation.

Upgrading Equipment and Conductors: Evaluate the existing distribution infrastructure and consider upgrading transformers, conductors, and other equipment to reduce losses and improve voltage regulation. Transformers with better voltage regulation characteristics can be employed, and using conductors with lower resistance can help reduce voltage drop.

System Monitoring and Control: Implement advanced monitoring and control systems that provide real-time data on voltage levels, load conditions, and system performance. This data can be used to identify voltage fluctuations, plan maintenance activities, and take corrective actions to maintain voltage regulation.

System Design Optimization: During the design phase, ensure that the distribution system is appropriately sized and configured to handle the anticipated loads. Properly sized conductors, transformers, and other equipment can help minimize voltage drop and improve voltage regulation.

Voltage Quality Standards: Establish and enforce voltage quality standards and regulations to ensure that the distribution system operates within acceptable voltage limits. Compliance with these standards will promote better voltage regulation and overall system performance.

Implementing these measures requires careful planning, coordination, and sometimes investment. It is advisable to consult with electrical engineers and professionals experienced in power distribution systems to assess the specific requirements and design suitable solutions for improving voltage regulation in your distribution line.

How is voltage regulation calculated?

Voltage Regulation for 11KV, 22KV, 33KV Overhead Line
  • % Voltage Regulation = (1.06 x P x L x PF) / (LDF x RC x DF)
  • RC = (KV x KV x 10) / ( RCosΦ + XSinΦ)
  • The required size of Capacitor (Kvar) = KVA1 (Sin ø1 – [Cos ø1 / Cos ø2] x Sin ø2)
  • L = [1 – (KVARC / 2 KVARL) x (2n – 1)]
  • % Voltage Rise = (KVAR(Cap) x Lx X) / 10 x Vx2
Voltage regulation in a power system is calculated using the following formula:

Voltage Regulation (%) = [(V_no-load - V_full-load) / V_full-load] * 100


V_no-load represents the voltage measured at the terminals of the load when no current is flowing (open circuit condition).
V_full-load represents the voltage measured at the terminals of the load when it is operating at full load (maximum current flowing through the load).
The voltage regulation formula calculates the percentage difference between the no-load voltage and the full-load voltage, relative to the full-load voltage. It provides an indication of how well the voltage is maintained within an acceptable range as the load changes.

A positive voltage regulation percentage indicates that the voltage decreases from no-load to full-load conditions, while a negative percentage indicates that the voltage increases. Ideally, voltage regulation should be as low as possible to ensure stable and reliable power supply to connected loads.

It's worth noting that voltage regulation can also be expressed as a percentage of the rated voltage. In this case, the formula becomes:

Voltage Regulation (%) = [(V_no-load - V_full-load) / V_rated] * 100

Where V_rated represents the rated voltage of the system or equipment under consideration. This allows for a standardized comparison of voltage regulation across different systems or equipment with varying rated voltages.

Nominal Value of Voltage Regulation:

  • Above 33kV (-) 12.5% to (+) 10%.
  • Up to 33kV (-) 9.0% to (+) 6.0%.
  • Low voltage (-) 6.0% to (+) 6.0%
The nominal value of voltage regulation refers to the desired or acceptable range of voltage regulation for a specific power system or equipment. The actual value may vary depending on the application, standards, and specific requirements.

In general, power systems aim to maintain voltage within a certain tolerance to ensure proper operation of electrical equipment and minimize the impact of voltage fluctuations on connected loads. The acceptable range of voltage regulation can vary based on factors such as the type of system, load characteristics, and industry standards.

For example, in many power distribution systems, a voltage regulation of ±5% is considered acceptable. This means that the voltage at the load terminals should not deviate more than 5% above or below the rated voltage under varying load conditions.

In some applications, stricter voltage regulation requirements may be necessary. For sensitive electronic equipment or precision machinery, tighter voltage regulation tolerances, such as ±2% or even tighter, may be specified to ensure optimal performance and prevent damage.

It's important to consult relevant standards, guidelines, and specifications specific to the particular application or industry to determine the appropriate nominal value of voltage regulation. These standards may vary across different regions or sectors, so it's crucial to consider the specific requirements and regulations applicable to your situation.

What is Voltage Regulation in Power System

By definition voltage regulation is “the ratio of voltage drop from no load to the full load to the no-load voltage”.

Voltage may regulate in the following ways on small scale-
  1. Electronic voltage regulator.
  2. Electromechanical regulators.
  3. Automatic voltage regulator.
  4. AC voltage stabilizers.
  5. Coil-rotation AC voltage regulator. 
  6. DC voltage stabilizers.
  7. Active regulators.
  8. Linear regulators. 
  9. Example of linear regulators. 
  10. Transistor regulator. 
  11. Regulator specification.

There are main two ways to express voltage regulation in a distribution network system:

One is voltage regulation up and another is voltage regulation down.

Consider the general formula for voltage regulation up as

Voltage Regulation Formula-1

Here Vnl is the no-load voltage and Vfl is the full-load voltage.

The voltage regulation up is normally used in the case of transformers.

Consider the general formula for voltage regulation down as

Voltage Regulation Formula-2

The voltage regulation is normally used in the case of alternators and power system calculations and its efficiency scaling. 

What is meant by good voltage regulation in the system?

Voltage regulation for the transformer is given by the ratio of change in secondary terminal voltage from no load to full load to no load secondary voltage.

So, good voltage regulation of a transformer means- output voltage fluctuation from no load to full load is the least. output voltage fluctuation with power factor is the least. difference between primary and secondary voltage is the least. The difference between primary and secondary voltage is maximum.

The bonus about the Voltage Regulator or Voltage Controller.

If you are interested to know about electronic voltage regulator circuits or want to purchase them, you may visit the following pages for details about them lm317.

ManufacturePart NumberDescription



1.2V to 37V adjustable voltage regulators

Inchange Semiconductor


Adjustable Voltage Regulator

ON Semiconductor


Positive Voltage Regulator

National Semiconductor


3-Terminal Adjustable Regulator



3-Terminal Adjustable Regulator



3-Terminal Adjustable Positive Voltage Regulator






1.2V to 37V adjustable voltage regulators

National Semiconductor


3-Terminal Adjustable Regulator

Fairchild Semiconductor


3-Terminal Positive Adjustable Regulator

Linear Voltage Regulator

A linear voltage regulator which is also called LDO or low-dropout linear regulator—uses a transistor controlled by negative feedback and is a regulator device that is used to maintain the specified output voltage that remains constant despite variations in input voltage.

Linear Voltage Regulator Circuit
Fig- Schematic line diagram of linear Voltage Regulator

A linear voltage regulator is an electronic circuit or device used to maintain a constant output voltage regardless of changes in the input voltage or load conditions. It accomplishes this by dissipating excess voltage as heat. Linear voltage regulators are commonly used in various electronic devices and power supply applications where a stable voltage source is required.

Here are the key characteristics and components of a linear voltage regulator:

Input Voltage (Vin): Linear voltage regulators accept an input voltage (Vin) that can vary within a specified range. They are often used to convert a higher input voltage to a lower, more stable output voltage.

Output Voltage (Vout): The output voltage (Vout) of a linear voltage regulator remains constant as long as the input voltage and load current stay within specified limits. Common output voltages include 3.3V, 5V, and 12V.

Regulation: Linear voltage regulators provide voltage regulation, meaning they can maintain a constant output voltage despite variations in the input voltage or changes in the load current.

Dropout Voltage: Dropout voltage is the minimum voltage difference between the input voltage and the output voltage for the regulator to operate properly. Linear regulators require a minimum dropout voltage to function correctly.

Load Regulation: Load regulation refers to how well the regulator maintains the output voltage when the load (current drawn from the regulator) changes. Linear regulators typically have good load regulation.

Line Regulation: Line regulation indicates how well the regulator maintains the output voltage when the input voltage varies. Linear regulators also generally have good line regulation.

Pass Element: The heart of a linear voltage regulator is the pass element, typically a bipolar transistor or a MOSFET. This component is responsible for controlling the flow of current and regulating the output voltage.

Feedback Mechanism: Linear regulators use a feedback loop that compares the actual output voltage to a reference voltage and adjusts the pass element's conduction to maintain a constant output voltage. This feedback loop can be implemented using operational amplifiers (op-amps) in voltage regulator ICs.

Heat Dissipation: One significant drawback of linear voltage regulators is that they dissipate excess voltage as heat, especially when the input voltage is much higher than the desired output voltage or when the load current is high. This heat dissipation can limit their efficiency, making them less suitable for applications with high power requirements.

Efficiency: Due to heat dissipation, linear voltage regulators tend to have lower efficiency compared to switching voltage regulators. They are more efficient when the input-output voltage differential is small.

Common linear voltage regulator ICs include the 78xx series (e.g., 7805 for 5V output) for positive voltage regulation and the 79xx series (e.g., 7905 for -5V output) for negative voltage regulation.

Linear voltage regulators are suitable for low-power applications where simplicity, low cost, and precise voltage regulation are more critical than high efficiency. If efficiency is a concern, especially in high-power applications, switching voltage regulators are often preferred despite their increased complexity.


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  3. Voltage Regulators: Voltage regulators are devices used to stabilize and regulate voltage levels in a power system. They detect variations in voltage and adjust the output accordingly to maintain a stable voltage level2. As per HESI Exam Help there are different types of voltage regulators, including tap changers, electronic voltage regulators, and automatic voltage regulators2.


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