Answer / a.ramesh

Why we use DO Fuse in HT Lines?
DO - Means Drop off.
*We do use DO Fuse in HT line for isolating the faulty bit
of Spur line.
What is the purpose of DO Fuse?
*Actually it is called as DOLO. ie., " Drop Off Lift On ".
One end of the fuse wise is tied to Supply end of DOLO unit
and the other end is connected through a stone to delivery
end of DOLO unit with stone hanging. When there is fault in
spur line the fuse wise cuts than because of gravitational
weight of stone the stone tied piece of fuse wire falls
down. there by supply will be isolated. After clearing the
fault the same way the fuse may be provided using 11KV
Hickory Rod with safety gadgets.
*No need for taking Line clear for carrying out maintenance
of this spur line. Remove the fuse, attend the maintenance
with making safety zone, observe safety rules, wearing
safety gadgets after completing the work provide DOLO fuse
restore power supply to the spur line.
*is provided in 11KV Spur lines for isolating spur line
during fault occurs.

Answer / k.prakashchandra

DOLO cut outs are provided to 11KV/433V tr centers and
sometimes to the 11 KV lines.The cut outs can be opened
,removed & re fixed with the help of hickory rods for
replacement of HT fuses of trs and opening of lines.As
they have renewable fuses ,they provide back-up protection
also.They are just like HT cut-outs and a cheap substitute
for GOS. Earlier they were used for protection to power trs
in sub-stations on 110 or 33KV side when they were called
expulsion type fuses.

Answer / abhijit

basically;DO is dropout fuse the two ends(contacts) of the
fuse connected by a spring ;
if fault occurs;and current value crosses the cut off factor
fuse contacts (spring)will get released;avoiding any problem
to the line

Answer / k.sudheer

DOLO fuses-
1. Avoids loose contact due to spring loaded 'clip' system to the stationary upper portion.
2. Once fuse is blown, the fuse rod 'hangs' down (since the sprint latch was ties by the fuse
wire itself.
3. blown fuse rod can be removed without 'line clear' by using a 'fuse link rod'. Fuse is the replaced at ground, and again using the fuse line rod, install back- "click" the top latch holds.
4. The DOLO fuse rod is a hollow tube of Mica sheets to prevent molten fuse wire from splashing out.

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