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

no of rotrs poles in salient pole synchronous machine

3 Answers  

---

How to Calculate Stc Rating of an indoor type VCB Panel? What is a full form of STC?

1 Answers   ABB,

---

How many sprinklers should be in one pipe line?

0 Answers  

---

What are the disadvantages of thermal power plant?

0 Answers  

---

How do we calculate the resistance per metre of single core aluminium stranded cable 19*3.25mm sheathed in pvc,at 15 deg C temperature?

0 Answers  

---

We have given to 3phase supply to ups system & how can coming netural

0 Answers  

---

why high speed tripping relay is used in protection circuit why not normal relay

0 Answers  

---

Why dc supply is used for closing and tripping coil of ht breakers. What happen if we use only ups ac supply only.

12 Answers   ACC, JLL, ZETDC,

---

Why only plate(copper) Earth pit given for neutral earthing? why not pipe(G.I) Earth pit?

1 Answers  

---

Can we convert off load tap changer transformer to on load tap changer transformer

2 Answers  

---

Differenciate between circuit wiring and sub main wiring with illustrations

0 Answers   MU,

---

We have 2 11kv/433v transformers for 2saperate acb for mv panels and 1 bus coupler acb. Suppose I’ll close bus coupler what will happen or it will be share the load. Please suggestion and any modification required.

1 Answers  

---