Which device is used for measurement of impulse current?
Digital Recorder, Impulse Voltmeter and Impulse Calibrator. In most of the testing and calibration laboratories, digital recorders are used for recording the waveforms of impulse voltages and impulse currents.
What is impulse current?
Impulse Current Generation: Impulse current testing of surge arresters is done to test their ability to withstand lightning impulses. Impulse current can have varying wave shapes and magnitudes depending upon their application and occurrence. Often, impulse currents appear as periodic or damped oscillatory currents.
How high voltage is tested using the method of sphere gaps?
The two spheres used are identical in size and shape. The schematic arrangement is shown in Figs 7.19a and 7.19b. The voltage to be measured is applied between the two spheres and the distance or spacing S between them gives a measure of the sparkover voltage.
Which kind of ammeter is used for series capacitance voltmeter?
rectifier ammeter
The series capacitance is formed as a parallel plate capacitor between the high voltage terminal of the transformer and a ground plate suspended above it. A rectifier ammeter is used as an indicating instrument and is directly calibrated in high voltage rms value.
What is the use of Hall generator?
Hall generators are used for contactless measurements of magnetic fields in the range from 10–6 to 105 oersteds. To measure weak magnetic fields, the generator is inserted in a gap in a ferromagnetic or ferrite core; this technique makes it possible to increase substantially the sensitivity of the generator.
What are the methods available for measurement of high alternating current?
Measurement of high a.c. voltages employ conventional methods like series im- pedance voltmeters, potential dividers, potential transformers, or electrostatic voltmeters. But their designs are different from those of low voltage meters, as the insulation design and source loading are the important criteria.
What are the types of impulse current waveform?
Standard impulse current wave shapes
- Exponential impulse current test for verification of current rating.
- Exponential impulse current test for determination of residual voltage like, as surge arresters.
What is the need of generating impulse current?
During Exponential current tests, the residual voltage of the test object is often in the range of hundreds of kV, thus requiring an impulse voltage generator as energy storage element. The impulse voltage generator is discharged through pulse forming elements to achieve the correct impulse current shape.
How do you calculate impulse voltage?
Impulse Voltage Measurements Using Voltage Dividers
- If the amplitudes of the impulse voltage is not high and is in the range of a few kilovolts, it is possible to measure them even when these are of short duration by using CROS.
- These three elements form a voltage generating system.
How the bank of capacitors is connected in a multistage impulse generator?
The cost and size of the impulse generator increases at a rate of the square or cube of the voltage rating. Hence, for producing very high voltages, a bank of capacitors are charged in parallel and then discharged in series.
What is impulse test of transformer?
The purpose of the impulse voltage test is to secure that the transformer insulation withstand the lightning overvoltage which may occur in service. When the charging voltage has reached the required value, breakdown of the spark gap F1 is initiated by an external triggering pulse.
What are the different types of test impulses?
Depending on the apparatus and its proposed application, the specifications prescribe different types of test impulses, e.g., lightning, switching and chopped impulse voltages as well as exponential, rectangular and short-time alternating currents.
What kind of instrument is used to measure impulses?
In most of the testing and calibration laboratories, digital recorders are used for recording the waveforms of impulse voltages and impulse currents. Other designations for such instruments are digital oscilloscope, transient recorder and digitiser, with which even certain constructional and functional principles are associated.
How are high voltage and high current impulses characterised?
According to IEC 60060 and IEC 62475, high-voltage and high-current impulses are characterised by parameters of their waveforms in the time domain.
What kind of resistor is used for Impulse measurement?
For the conventional measurement of impulse currents during tests of power apparatuses up to a few 100 kA, low-ohmic resistors or magnetic coils are used in combination with digital recorders enabling computer-aided processing of the recorded data.