Answer / sri

High-voltage transformers contain oil as their insulating
dielectric. When a critical electric field is exceeded,
conduction paths grow at microsecond speeds through the oil,
in the form of branched trees, called streamers. These can
lead to destructive breakdown.

Above a particular electric field, known as the dielectric
strength Eds, the dielectric in a capacitor becomes
conductive. The voltage at which this occurs is called the
breakdown voltage of the device, and is given by the product
of the dielectric strength and the separation between the
conductors

The high voltage test (also called dielectric strength test
or hipot test) can be made in AC or DC. If the high voltage
test is made in DC, it is then combined with insulation ;
if the high voltage test is made in AC, it is then, this is
then, more stressful for the sample and made according to
the sketch below.

Measurement of high voltage test under alternating current
is performed using an alternating voltage (50Hz) adjustable
to an effective 50V to 1,500V. As is the case with direct
current, the high voltage test detects any sudden rise of
current up to a programmed threshold.



http://www.sefelec.com/en/high-voltage-test.php

purpose
to test the insulators for their effectiveness. normally
used for transformer oil testing purpose.

Answer / nandu

we using hv kit for meggering purpose,ht breaker close open
test and tranformer core winding test

Answer / dinesh

1.where we use di-electric material there occur breakdown

what happens when back charging of transformer is done for longer period

1 Answers  

---

what is OLTC and difference between RTCC and OLTC

7 Answers   Sodexo,

---

how to calculate the cable size depending on the amps?

1 Answers   Polycab,

---

when meggering a 3ph,480v oil reservoir heater on a regen gas compressor, why do I get a reading to ground when meggering phase to ground? shouldn't it read opened or is there something that makes it read closed? on the same heater, when ohming, it reads open. thanx

1 Answers  

---

What are safety features considered for Lifts during emergency?

1 Answers  

---

Ammeter of 1 ohm resistance measure max 10 ohm to measure higher resistance from it

6 Answers   BARC,

---

On 400 amp factory load how kvarh capacitors provide

0 Answers  

---

What are the effects of electrical faults?

0 Answers  

---

my motor rating is 800HP, 128Amps, 3.3kV. What is capaitor bank i can use for PF improvement to 0.990?

3 Answers  

---

what happens if the phase sequence of parrlel connected sys will changed & phase displacement

1 Answers  

---

which signal we found accurate reading of analog signal or degital signal and why?

1 Answers  

---

who iz power minister ?? :P

1 Answers   IOCL,

---