# Measurement of High Voltage and Currents

## Impulse Voltage Measurements

Potential Dividers for Impulse Voltage Measurements: Potential or voltage dividers for high voltage Impulse Voltage Measurements, high frequency a.c. measurements, or for fast rising transient voltage measurements are usually either resistive or capacitive or mixed element type. The low voltage arm of the divider is usually connected to a fast recording oscillograph or a peak …

## Uniform Field Electrode Gaps

Uniform Field Electrode Gaps: Sphere gaps, although widely used for voltage measurements, have only limited range with Uniform Field Electrode Gaps. Hence, it is not possible to ensure that the sparking always takes place along the uniform field region. Rogowski presented a design for Uniform Field Electrode Gaps for sparkover voltages up to 600 kV. …

## Sparkover Voltage of Sphere Gaps

Factors Influencing the Sparkover Voltage of Sphere Gaps: Various factors that affect the sparkover voltage of a sphere gap are: nearby earthed objects, atmospheric conditions and humidity, irradiation, and polarity and rise time of voltage waveforms. 1.Effect of nearby earthed objects: The effect of nearby earthed objects was investigated by Kuffel by enclosing the earthed …

## Sphere Gaps are used to measure Voltage Measurement

Sphere Gaps are used to measure Voltage Measurement: Sphere Gaps are used to measure Voltage Measurement – A uniform field spark gap will always have a sparkover voltage within a known tolerance under constant atmospheric conditions. Hence a spark gap can be used for measurement of the peak value of the voltage, if the gap …

## Peak Reading AC Voltmeter Circuit

Peak Reading AC Voltmeter Circuit: Peak Reading AC Voltmeter Circuit : When a capacitor is connected to a sinusoidal voltage source, the charging current where V is the rms value of the voltage and co is the angular frequency. If a half wave rectifier is used, the arithmetic mean of the rectifier current is proportional …

## Electrostatic Voltmeters

Electrostatic Voltmeters: In Electrostatic Voltmeters fields, the attractive force between the electrodes of a parallel plate capacitor is given by where, V = applied voltage between plates, C = capacitance between the plates, A = area of cross-section of the plates, d = diameter of plates s = separation between the plates, ε0 = permittivity of …

## Magnetic Type Potential Transformer

Magnetic Type Potential Transformer: Magnetic Type Potential Transformer are the oldest devices for a.c, measurements. They are simple in construction and can be designed for any voltage. For very high voltages, cascading of the transformers is possible. The voltage ratio is: where V1 and V2 are the primary and secondary voltages, and N1 and N2 are …

## Capacitance Voltage Transformer

Capacitance Voltage Transformer: The errors due to harmonic voltages can be eliminated by the use of capacitive voltage dividers with an electrostatic voltmeter or a high impedance meter such as a T.V.M. If the meter is connected through a long cable, its capacitance has to be taken into account in calibration. Usually, a standard compressed …

## Series Capacitance Voltmeter

Series Capacitance Voltmeter: To avoid the drawbacks pointed out earlier, a Series Capacitance Voltmeter is used instead of a resistor for a.c. high voltage measurements. The schematic diagram is shown in Fig. 7.10. The current Ic through the meter is: where, C= capacitance of the series capacitor, ω= angular frequency, and V= applied a.c. voltage. If …

## Series Impedance Voltmeter

Series Impedance Voltmeter: For power frequency a.c. measurements the Series Impedance Voltmeter may be a pure resistance or a reactance. Since resistances involve power losses, often a capacitor is preferred as a series reactance. Moreover, for high resistances, the variation of resistance with temperature is a problem, and the residual inductance of the resistance gives …