Minggu, 25 Desember 2011

Voltage Impulses

Forms of Voltage Impulses

There are three forms inpuls voltage that may be experienced in the electric power system, namely:
1. Lightning impulse voltage
2. Surge impulse voltage circuit
3. Truncated impulse voltage

Wavefronts are part of a wave that starts from point zero (nominal) to the point of peak (according to IEC determined from the nominal point of intersection between the axis of time with the straight line connecting the 30% and 90% of peak voltage). While the tail is part of the wave peak to wave down 50% from the peak point. The wave form is expressed as:
± (x Tt Tf) ms. [IEC: ± (1.2 x 50) ms]

Circuit used for surge value:
[IEC: ± (250 x 2500) ms]
Tools that can be used to generate a high voltage impulse among others:
1. RC impulse generators
2. Impulse generator RLC
3. Marx Generator
5. How to Measure Voltage Impulse

a. Using Sela Ball

Sela ball is often used to measure the impulse voltage. Sela ball must always ditera with voltage spark between the ball 50% of the standard. Sela standard ball is a ball broke in qualifying standards regarding:
1. Quality
2. The distance between
3. The size of the ball

In certain circumstances the air, between the ball always has a certain spark voltage as well. That is why the sidelines ball can be used as a measuring tool.

Form of the condition of the ball electrode
1. Its surface is slippery
2. Flat arches
3. The surface of the ball must be free of dust, oil, etc.
4. Prisoners damper installed in series with the minimum distance 2d
(D = diameter) of the ball is measured from the point where there is a spark.
a. The test voltage ac = 100 kW s / d 1000 kW
b. Impulse test voltage 500 W

b. Using a CRO

By using Chatode-Ray Oscillograph (CRO) we can:
- Voltage peak
- Waveform
- The lack of impulse shape abnormalities (describing damage to test equipment)
CRO can only measure a low voltage only, so to measure the high voltage required voltage divider (either resistors or capacitors)

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