A voltage divider is an important electrical device used to reduce high voltage into a smaller and measurable voltage. It is widely used in high-voltage testing, measurement systems, laboratories, substations, and electrical engineering applications.

According to the working principle, voltage dividers are mainly divided into three categories:

1. Resistance Voltage Divider
2. Capacitive Voltage Divider
3. Resistance-Capacitance Voltage Divider

Among them, capacitor voltage division technology plays an important role in impulse voltage measurement and high-voltage testing systems.

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1. Resistance Voltage Divider

A resistance voltage divider uses pure resistors to divide voltage. It has a simple structure, stable performance, and high measurement accuracy, making it one of the most commonly used voltage dividers.

Advantages of Resistance Voltage Divider

Under lightning impulse voltage conditions, the resistance voltage divider offers several benefits:

High Stability

When low-temperature-coefficient copper wire or alloy resistance wire is used, the divider provides:

• Excellent temperature stability
• Good long-term performance
• Reliable measurement accuracy

Fast Response Performance

Resistance voltage dividers can achieve excellent response characteristics, especially when designed with low inductance structures.

Because of these advantages, many standard impulse measurement systems use resistance voltage dividers.

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Limitations of Resistance Voltage Divider

Although widely used, resistance voltage dividers also have some disadvantages.

Influence on Impulse Generators

To obtain faster response speed, the resistance value cannot be too large. However, low resistance may increase the load on the impulse voltage generator and shorten the wave tail time.

In practical applications, this issue is usually solved by adjusting the wave-tail resistance of the generator.

Stray Capacitance Effects

When measuring transient impulse voltages, the measurement error is related to:

Error \propto R \times C

Where:

• (R) = resistance value
• (C) = stray capacitance to ground

Therefore, engineers try to reduce:

• Ground stray capacitance
• Internal inductance
• Physical size of the divider

To improve performance, resistance wires are usually tightly wound on insulated tubes and immersed in transformer oil for insulation and capacitance reduction.

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2. Capacitive Voltage Divider

A capacitive voltage divider, also known as capacitor voltage division, uses capacitors instead of resistors to divide voltage.

It is commonly used for pulse voltage and high-voltage impulse measurements.

Types of Capacitive Voltage Divider

Capacitive voltage dividers are generally divided into two structures:

Distributed Capacitive Voltage Divider

This type uses several high-voltage capacitors connected together.

Each capacitor element contains:

• Capacitance
• Internal inductance
• Contact resistance
• Stray capacitance

Because the parameters are distributed throughout the system, it is called a distributed capacitive voltage divider.

Centralized Capacitive Voltage Divider

This design uses only one high-voltage capacitor.

Usually, it consists of two metal electrodes placed in a nearly uniform electric field with air as the dielectric medium.

This structure is called a centralized capacitive voltage divider.

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Advantages of Capacitor Voltage Division

The capacitor voltage division method offers several important advantages:

No Heating Problem

Unlike resistance dividers, capacitive dividers consume very little energy and generate minimal heat.

Suitable for Long Wave Measurements

Capacitive voltage dividers perform very well when measuring:

• Long wave-front voltages
• Long half-peak impulse waves
• Power-frequency voltages

Stable Capacitance

When compressed-gas standard capacitors are used, the capacitance value remains:

• Highly accurate
• Stable over time
• Less affected by surrounding objects

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Limitations of Capacitive Voltage Divider

Although capacitor voltage division is very useful, it also has limitations.

Slower Response for Steep Waves

The shielding ring stray capacitance can increase response time, making capacitive voltage dividers less suitable for measuring very steep impulse waves compared with shielded resistance dividers.

High-Frequency Oscillation

When used for impulse measurements, centralized capacitive voltage dividers may experience superimposed high-frequency oscillations.

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3. Resistance-Capacitance Voltage Divider

The resistance-capacitance voltage divider combines the advantages of resistance and capacitive voltage dividers.

It is generally divided into:

• Resistance-capacitance series divider
• Resistance-capacitance parallel divider

The series type is also called the damped capacitive voltage divider.

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Why Use a Resistance-Capacitance Voltage Divider?

This design helps solve the residual inductance problem found in pure capacitor voltage division systems.

Its main advantages include:

• Reduced oscillation
• Improved waveform response
• Better impulse voltage measurement performance
• More stable output signals

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Types of Damped Capacitive Voltage Divider

High-Damping Capacitive Voltage Divider

This type is mainly used as a voltage measurement conversion device and is not suitable as a load capacitor for impulse generators.

Low-Damping Capacitive Voltage Divider

This design uses very small damping resistance values.

Advantages include:

• Easier standard wave generation
• Dual function as measurement and load capacitor
• Better convenience in practical testing

However, it may still produce some oscillation during measurements.

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Working Principle of Resistance-Capacitance Divider

In theory:

• During rapid voltage changes, the divider ratio mainly depends on capacitance
• During slower voltage changes, resistance becomes the dominant factor

This combination allows the divider to perform well under different voltage conditions.

In practical laboratory applications, some designs eventually remove the parallel resistance because selecting the ideal resistance value can be difficult.

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Applications of Voltage Dividers

Voltage dividers are widely used in:

• High-voltage laboratories
• Lightning impulse testing
• Power frequency measurement
• Transformer testing
• Substation systems
• Insulation testing
• Pulse voltage measurement

Today, capacitor voltage division technology remains one of the key methods used in modern high-voltage measurement systems.

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Conclusion

There are three main types of voltage dividers: resistance voltage dividers, capacitive voltage dividers, and resistance-capacitance voltage dividers.

Each type has its own advantages, limitations, and application scenarios. Among them, capacitor voltage division is especially important in high-voltage impulse testing because of its low energy consumption and excellent long-wave measurement capability.

Choosing the correct voltage divider depends on factors such as:

• Measurement accuracy
• Waveform characteristics
• Voltage level
• Response speed
• Testing environment

Understanding these voltage divider types helps engineers select the most suitable solution for high-voltage testing and electrical measurement applications.