Answer / usman aslam

It is placed for human safety. Lightening can cause step
potential between 2 feet of the person standing in yard.
So gravel is placed so that moisture is maintained and
potential of earth remains equal throughout the yard hence
step potential will be zero.

Answer / aaa

It provides a highly resistive layer which increases the allowable step and touch potentials.

Answer / brandon

A thin layer of aggregate above a low-resistance substrate
(or embedded ground grid if the substrate is a
high-resistance material) provides a high resistance between
the bottom of a human's feet and the substrate. This will
lower the upward current through the body considerably in
the event of a L-G fault compared to the equipment bonds
(assuming equipment is properly bonded to the substation
ground). However, since the aggregate is thin relative to
the ground plane, it does not impede the shape of the
equipotential voltage field of the substation and thus
reduces the step potential by keeping a consistant voltage
grading.

Aggregate is not for lightening as lightening protection is
provided through overhead shield conductors bonded to the
ground grid or substrate.

If oil-filled equipment fails and and a fire is started, the
aggregate also has a quenching effect by distributing the
oil within the void spaces and creating small pockets
instead of a large surface of oil.

See IEEE 80 for the complete explanation.

Answer / nikhil

This is done to prevent grass to grow in the area. Grass
can cause dew or moisture which can be dangerous for the
equipments and working staff there.

Answer / sukhvinder

Gravelling is done to reduce the ground resistance of the
foot from its value.

Answer / yogendra singh

This is done to prevent grass to grow in the area. Grass
can cause dew or moisture which can be dangerous for the
equipments and working staff there

Answer / dinesh

its placed to avoid the soil erosion from the substation in
rainy season & also to prevent grass & unwanted plant to
grow in the substation which can harm the equipments.
Such unwanted plants & greenery can be home for reptiles
which cam cause short-circuit etc to the equipments and
also damage.

Answer / samal

Ok grass can cause moisture ,it will help in maintaining
the resistance of yard(will be very low)

so moisture is not the reason of that cause.
it(aggregate) will mantain the capacitance of yard ground
to live part & helps in maintaining vibration

Answer / alpz

its because majority, if not all of equipment in substation
is oil filled, aggregate is use to prevent oil in dripping
around the entire s/s in case there's a maintenance or
accidental leak in any equipment.

why motor rating in kw?

3 Answers  

What is Hot reserves and spinning reserves?

1 Answers  

Grounding. Dear all at one of my site we checked the amps at the earthing cable to the alternator it was found 125 to 130 A. at the neutal cable in same machine found 146A. in the same plant checked the earthing current on other alternator it was 52A, and neutral 116 A. we are facing problems with our controller and the card was damaged once. can that neutral/GND current be a reason? as there is common grounding for the Alternator,Brkr panel,Transformer?

2 Answers  

how to produsing geretor power

0 Answers  

what is power factor?

8 Answers   Adani, Blue Star, Power Control,

HI SIR, AM PREPARING FOR RRB FOR SECTION ENGINEER POST. PLZ SEND ME THE PREVIOUS QUESTION PAPERS AND HELP ME. I HAVE NO ENOUGH TIME MY EXAM DATE IS 22ND JUNE.... MY EMAIL ID IS nalla.amarnath@gmail.com

0 Answers  

In 400KV Switchyard, we have used Circuit Breaker With PIR, what is the significance of PIR & why they'r used?

2 Answers  

Define norton equivalent circuit?

0 Answers  

Which type of transformer used in lighting load?

2 Answers   IMFA,

how much watts are equal to one unit of energy meter?

9 Answers  

why motor rating in KW?

2 Answers  

Whether amorphous core transformer is commercialized or not:Name of company making amorphous core transformer and what are different rating?

0 Answers   DAE,