List of High Voltage Measurement Methods and Devices

Voltage measurement is a very important part of an electrical measurement system. The voltage is basically a potential difference or pressure between two ends of a conductor that forces to flow the electric current within the conductor. So, a particular load requires a certain amount of voltage for its operation. If there is a lower voltage or higher voltage than the required voltage, the electrical load will not work properly. Even the load may get damaged if high voltage is applied. So we sometimes need to measure voltage in an electrical system. 

For medium voltage, we can use our standard conventional measuring instruments such as a voltmeter. We just need to connect the voltmeter in parallel with the voltage source. But when it comes to the point of extremely low and high voltage measurement, we need some special devices and methods. Because in these cases our standard measurement devices cannot measure properly. Even when we measure the high voltage it may get damaged and there is a high risk of electrical safety.

High Voltage Measurement Methods and Devices

Here are some examples of common methods and devices for high-voltage measurement,

1. Electrostatic Voltmeter
2. Sphere Gaps
3. Potential Transformer(P.T)
4. Series Resistance Methode
5. Capacitive Potential Divider Method
6. Resistive Potential Divider Method
7. Multiplier
8. Potential Divinding Matching
9. Klydonograph
10. Peak Reading Voltmeters
11. Capacitance Measurement
12. High Voltage Probe

High Voltage Measurement using Electrostatic Voltmeter

During high voltage measurement, the main problem is electrical safety. We take a huge level of safety precautions when we connect a measuring device to the high voltage source. But the electrostatic system does not need any direct contact. Generally, the voltage above 10KV can be measured using a disc-type electrostatic voltmeter and it can be used up to 200KV. The electrostatic Abraham voltmeter can be used for 3KV to 500KV voltage measurements. These electrostatic devices are constructed by two electrodes that attract or repeal the electrostatic object and force it to move the pointer.

Sphere Gaps

The sphere gap method is a very reliable method for high voltage measurement. Here, two metal spheres are placed at a gap and the voltage is applied to them. And the breakdown of the gas(generally air) between the gap due to the applied voltage is measured. The density of the gas gets affected by the spark over Voltage for a particular gap distance. The breakdown also depends upon various factors such as the size of the metallic spheres, gap area, etc. But it is independent of the humidity.

Potential Transformer(P.T)

A potential Transformer is also known as a Voltage transformer. It is basically a step-down transformer. Generally, the high voltage to be measured is stepped down into a low voltage. By measuring the ratio between high voltage and low voltage, it is very easy to measure the high voltage by measuring the low voltage. For, example a potential transformer that can step down the 11KV into 110V. So, we cannot use a traditional voltmeter with 11KV, but we can connect it with 110V. So, when the voltmeter measures 110V with the help of a Potential Transformer, we will be sure that there is 11KV in the system.

Series Resistance Method for High Voltage Measurement

Series Resistance Method issued for both High Voltage AC and High Voltage DC measurement. In this method, a very high resistance( generally 20 KiloOhm/Volt) is connected in series with a micro ammeter. And this whole combination of series resistance and ammeter is connected across the high voltage is to be measured. This method is practically implemented with very high safety measures. Generally, the system is kept in an insulated container. Sometimes, a safety gap or spark gap, or neon lamp is connected across the microammeter for safety purposes. In this method, multiple resistors of different values can be connected to achieve the proper insulating and limiting function.

Capacitive Potential Divider Method

The capacitive potential dividing method is very useful for alternating voltage measurement. It makes very minim electrical power losses. Generally, two capacitors of different values are connected in series and the whole combination of those two capacitors is connected across the voltage source. A step-down transformer can be used to step down the very high voltage at a level so the measurement can be done with minimum effort. 

The electrostatic voltmeter is connected across the low-valued capacitor. We know that when two series connected capacitors are connected across a voltage source the voltage is divided across the two capacitors depending upon their values. The total voltage is equal to the total voltage of the individual capacitors. And using mathematical calculations we can measure the actual voltage by measuring the voltage across any one capacitor.

Resistive Potential Divider Method

The resistive potential dividing method can be used for both AC and DC voltage measurement but it is most suitable for DC voltage measurement. Here also a high resistance potential divider is connected across the voltage source to be measured. A low voltage voltmeter across any part of the divider so it can measure the definite fraction of the total voltage. As we know that resistance can cause electrical power loss so this method is not so much efficient.

The multiplier for High Voltage Measurement

The principle of a multiplier is the same as the voltage divider principle but it helps a lot for the DC voltage measurement. Generally, a voltage multiplier is an electrical circuit consisting of resistors or diode or capacitors combinations.

Klydonograph

Klydonograph is most suitable for surge voltage or high-level transient voltage measurement. It is built with a dielectric sheet and a photographic film, and electrodes. The high voltage to be measured is applied to the electrodes. When the impulse voltage is applied to the high-voltage electrode the photographic film or plate shows different diagrams in the Lichtenberg Pattern. For different characteristics of the applied voltage, a different pattern can be shown. Generally, the patterns have a different radius. For example, different voltages such as negative voltage, small positive voltage, moderate positive voltage, and large positive voltage make different patterns.

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• Difference between Earth Fault Relay and Earth Leakage Relay
• Series and Shunt Reactor Difference, Applications, Use
• List of Undervoltage Protection Equipment, Device and Their Function
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