Answer / er sushil saini

this is because whenever fault occur the ac supply will
also fail so protection system will not work and damage to
equipments can occur. DC supply in battery bank will always
be available in case of ac failure and protection system
will work and trip the breakers.

Answer / rd dadhich

1.It is very common practice to use battery with charger for
protection , operation & indication in HT switch gears due
to most relable system to work as after charging only
battery comes directly in line during failure of AC supply.
or power supply.

UPS can be used theoretically , but we are adding one more
week link in critical protection supply due to addition of
inverter. , as inverter is :-

AC supply . > Battery Charger > Battery > Inverter

Where as battery charger is only :-

AC supply . > Battery Charger > Battery

2. AC coils of tripping & closing are un common & bigger in
size.

Answer / kesavan.03

In the case of AC supply we can't reliable. However UPS is
available in any failure of UPS supply also will dangerous
for control system. As in the case of DC supply the battery
is charged & it is available whenever we need. So DC coils
are used for control purpose(Closing & Tripping),

Answer / er. manoj

Now consider a situation when there is a fault and coil supply is given AC, as we know in case of fault there is a voltage dip, so across the coil sufficient voltage would not build up to energize it. So DC is given across tripping or closing coil

Answer / jpgupta

how to check capacitor

Answer / ganesh yeole

hey friends.....I agreed ur ans but I feel one more thing...if we use AC supply to HT system....see you know well sign wave when wave going upper side then down....when wave coming down side you have to see 0 volt but HT tripping or closing coils or contactor pick up time not sufficiently working on there. it not working properly so you found there electrical damages. that's cause DC supply using in HT system. cause DC is directly pick up to coils.........if you are satisfied to my answer you mailed me ganesh.yeole89@gmail.com.......mob no. 09579853838

Answer / ankit

dc supply is used because response time in dc supply is fast as it does not have positive negative sinusoidal wave like ac supply
and in ht we need very fast switching in microseconds

Answer / jp gupta

why can check Ignitor thas its ok or not

Answer / satyanarayana

Suppose if breaker was tripped on under voltage then Ac supply is not available at that instant so that breaker will not trip if AC supply is used for breaker closing and tripping.

Answer / avd

Fundamentaly UPS AC supply can be used. But you are
investing more in UPS than the battery charger. Remember
UPS will have inverter section also.

why transformer does not obey ohm law?

27 Answers  

how can we know cable size for a given current? if any one have catalogue plz mail to vijay_raju369@yahoo.co.in

5 Answers  

HOW TO CALCULATE EARTHING SIZING?

0 Answers   L&T,

Hello every one I am currently working in IT side but i have an offer to work under 'A' license holder and he says i can get c license what is the use of c license and what shall i do after getting it basically i am an electrical graduate please help me shall i leave this it job and work in electrical maintenance will i have a good future i am confused Thank You in Advance

1 Answers  

What is DTR erection?

0 Answers  

What is the difference between Derived earth Fault and measured earth fault.How it works.

1 Answers  

what is electronic regulator and how we can use that in fans?

3 Answers  

What is required of exietation to the alternater.

4 Answers  

How many kinds of E.L.C.B and how to work E.L.C.B

0 Answers   Accenture,

what is efficient motors and how it is different from normal induction motors

0 Answers   Sarthak Contracts,

what is difference between low voltage and high voltage

3 Answers  

Classify driling machines.

0 Answers   Essar,