Answer / ankit sinha

sf6 is a high speed ckt breaker in which sf6 gas is used as
an arc quenching medium.sf6 is ahigh electronegative gas.it
has a great tendency to absorb free electrons.these
breakers are used from 115kv to 230kv.

Answer / raghavendran

SF6 stands for sulpher hexa flouride.its a gaseous material
having an electro negative property, making it condusive to
be used for absorption of free electrons.In SF6 breakers, we
have SF6 gas compressed at certain pressure say 2.2 bar
inside a chamber, the pressure level of whose is constantly
monitored.It is also a great fire resistant.

Answer / vijay

SF6 is one of the Gas insulation for circuit breaker.which
placed on busbar and cb opening,closing elements.it has
been used 22kV to 230kV.its high prodection and safety

Answer / abuhuraira munir

Sulphur hexafluoride (SF6) is an inert, heavy gas having
good dielectric and arc extinguishing properties. The
dielectric strength of the gas increases with pressure and
is more than of dielectric strength of oil at 3 kg/cm2. SF6
is now being widely used in electrical equipment like high
voltage metal enclosed cables; high voltage metal clad
switchgear, capacitors, circuit breakers, current
transformers, bushings, etc. The gas is liquefied at
certain low temperature, liquefaction temperature increases
with pressure.
Sulphur hexafluoride gas is prepared by burning coarsely
crushed roll sulphur in the fluorine gas, in a steel box,
provided with staggered horizontal shelves, each bearing
about 4 kg of sulphur. The steel box is made gas tight. The
gas thus obtained contains other fluorides such as S2F10,
SF4 and must be purified further SF6 gas generally supplier
by chemical firms. The cost of gas is low if manufactured
in large scale.
Medium-voltage circuit breakers rated between 1 and 72 kV
may be assembled into metal-enclosed switchgear line ups
for indoor use, or may be individual components installed
outdoors in a substation. Air-break circuit breakers
replaced oil-filled units for indoor applications, but are
now themselves being replaced by vacuum circuit breakers
(up to about 35 kV). Like the high voltage circuit breakers
described below, these are also operated by current sensing
protective relays operated through current transformers.
The characteristics of MV breakers are given by
international standards such as IEC 62271. Medium-voltage
circuit breakers nearly always use separate current sensors
and protection relays, instead of relying on built-in
thermal or magnetic overcurrent sensors.
Medium-voltage circuit breakers can be classified by the
medium used to extinguish the arc:
Vacuum circuit breaker
SF6 is an inert, nonflammable, non-toxic and non-ozone
depleting insulating medium.
SF6 has three times the dielectric strength of air at
atmospheric pressure. This can be further increased by
increasing the pressure.SF6 consists of very large
molecules and can be enclosed without notable losses for
the complete service life of a switchgear installation
(approx. 40 years).

how to find out speed of single phase motor

6 Answers   BARC,

---

what is the formula for hv test for cable and circuit breaker..????

0 Answers  

---

Why a Transformer Noise during its running condition ??

11 Answers   NTPC, UPPCL,

---

why there is no current in the rotor body althrough the flux linking with it also get changes. why current only flows in windinds not in rotor

1 Answers   Vedanta,

---

y we use neutral,all r told its used to for closed path..k its a just used to closed path,in a transmission line y we put same conductor used n both phase and neutral..if we use less than phase conductor in neutral mean we ll reduce cost its right r wrong..if we use mean any problem occur in transmission line..

0 Answers   ME,

---

what is the funda of earthing? Explain breifly about earthing?

5 Answers   IOCL,

---

sir, i want to know the calculation for find rated current for cable sizes.(both copper & aluminium) with examole. please sir for example: 35sq.mm al.cable is withstands for how many amps? is suitable for 45kw motor?

5 Answers   L&T,

---

What is meant by derating factor?

0 Answers  

---

1.main parts of generator? what is used A-check,B-check,C- check? 2.what is FM200 system in data centers? 3.difference between pac,ahu?

0 Answers   TATA,

---

For single phase(phase to neutral) having potential difference 230.in three phase(phase to phase)we have 440V HOW...?

1 Answers  

---

i am going to give the JSEB,RANCHI exam for power plant,so i need some samples of papers related to that,so please send me these papers by my mail id.

0 Answers  

---

Why we are getting low voltage in star connection?

2 Answers  

---