This is about the recent problem that we have faced in our
project site.
We have 6/7.5 MVA. 66/11kV three phase star - star power
transformer. The neutral was solidly connected to the
earthing mat. But because of high resistance of earthing
mat (130 ohm on LV and 180 ohm on HV), one day LV side
neutral earthing conductor melted and we had a huge damage.
Can any one plz tell me what might happen when we connect
power transformer neutral to the earthing mat which has
high resistance (>100 ohm ) ?????
Answer Posted / gairhe
I think you are right.
for the LV even if the imbalance neutral current is 10 A,
the 130 ohm resistance will produce GPR ( Ground Potential
Rise ) of 10 X 130 = 1.3 kV.
Also at the site the transformer neutral earth conductor was
touching the 185 sq mm single core copper power cable and
control cable. May be because of this high GPR , sparking
occurred and heat was generated.
The neutral earthing conductor is of size 95 sq mm. so 10 A
current is not a big issue.
In my view 1.3 kV and sparking developed heating at the
group of XLPE power cable, control cable and fire started .
Then the XLPE power cable was damaged and because of the hig
earth fault from the damage of XLPE cable, the near by
neutral earthing conductor got melted.
Is This Answer Correct ? | 1 Yes | 0 No |
Post New Answer View All Answers
dear sir/madam i want to get some knowledge about RRB EXAMINATION(section engineer) 1- what is minimum cut off 2- wht portion is major portion . 3- can any body provide Sample paper. thanks & regards ashish
What are the basic component of a cro?
plese send me the oces/dgfs sylabus and previous year question pattern of electrical engg.?
What is the requirement of grounding the neutral of single phase generators on load? If the neutral is not grounded, what will be the effect?
what is the effect of power factor of machines in starting current
In case of salient pole alternator when number of poles are 4 or more than 4 it helps the flux wave to be sinusoid as air gap length is increased from center to tip , but if the number of poles are 2 how does the flux wave is sinusoidal?
300m long and 30kw inductive loade 3phase supply how many size cable required
Two bulbs of 100w and 40w respectively connected in series across a 230v supply which bulb will glow bright and why?
ht side line to earth voltage
CALCULATE THE TOTAL VOLTAGE DROP AND SELECT THE CABLE SIZE IN MM-SQARE FOR A PANEL-262KW AT 110 METER FROM THE SOURCE SUPPLY , SUPPLY VOLTAGE 240/415
what is difference between cpp electrical system and refinery electrical system
I am a possesor of c licence from 1993. I forgot to renew during the year 1998. During that time I was working at TNEB to till date. Is there any possibility to get renewed? or to apply for a new one?
I use 20 nos led tube 4feet, in pathway 100mtr approximate, so what size cable i use for lighting
when measure the core loss of three phase distribution transformer or three phase reactor loss, one phase shown negative watt loss. why??
why do we use 25kv supply for traction purpose?