What are the requirements of a sphere gap for measurement of high voltages?
Answer. A sparkover voltage of 30 kV (peak) at 1 cm spacing in air at 20°C and 760 ton pressure occurs for a Sphere Gap Measurement or any uniform field gap.
What are the parameters and factors that influence peak voltage measurement?
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.
Why do we use sphere gap for High Voltage?
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 distance is known.
What is sphere gap in high voltage engineering?
It is known that spark gap spheres measure the peak AC voltage with a precision of ±3%. The breakdown voltage depends on the distance between the spheres, on the spheres diameter, and on the type of voltage: direct, alternating, or impulse.
What are the factors affecting sphere gap measurement?
Various factors that affect the sparkover voltage of a sphere gap are: nearby earthed objects, (i) atmospheric conditions and humidity. (ii) irradiation, and (iv) polarity and rise time of voltage waveforms.
What is a sphere gap?
a device for closing or opening an electric circuit. A sphere gap consists of two spherical electrodes separated by a gas-filled insulating interval.
What are sphere gaps?
Definition of sphere gap : a spark gap (see spark gap sense 2) in which the electrode terminals are metal spheres.
What is the effect of dust particles on the measurement using sphere gaps?
In the measurements of high voltages using sphere gaps, particulate pollution can adversely effect the accuracy of HVAC measurements by up to 6% and should be taken into account.
Why is the sphere gap used to measure the breakdown of gas?
The breakdown strength of a gas depends on the ionisation of the gas molecules, and on the density of the gas. As such, the breakdown voltage varies with the gap spacing; and for a uniform field gap, a high consistency could be obtained, so that the sphere gap is very useful as a measuring device.
What is sphere gap?
What are the effect of humidity on the spark over voltage?
Sparkover voltage increases with humidity.
How sphere gap is used as measuring instrument?
In the measuring device, two metal spheres are used, separated by a gas-gap. The potential difference between the spheres is raised until a spark passes between them. The breakdown strength of a gas depends on the size of the spheres, their distance apart and a number of other factors.