Answer / k.prakashchandra

Have you measured IR properly, as the values are very high
?The IR should not exceed 2 ohms for a 66 KV MUSS .I do not
know whether primary neutral is to be earthed in case of
star/star tr.It is stated that LV side IR is 130 ohms ,and
hence the maximum earth fault current will be 50A.For 7.5
MVA tr the rated LV line current is about 400 A and EFR is
likely to be set at 80A.It appears that the earth wire
melted due to continuous earth fault current.If there is
conductor to ground fault at a distance of 100 m from tr
earthing ,there will be a pd of 63.5 V /m along the line
between the fault point and the neutral earth. If anybody
stands barefooted with feet 1 m apart along this line, he is
likely to be electrocuted as the power line does not
trip.Further the ground around the earthing also may be at
nearly phase voltage during earth fault

Answer / 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.

can anybody sent me power grid questions. what subject should i prefer for preparation?

0 Answers   Reliance, Vascon,

---

What are the main advantages of bode plot?

0 Answers  

---

Dear sir, iam completed iti ncvt electrician 2000-2002 & diploma electrical eng completed 2008-2010 distance education in rvd university, still i got B licences only but my working company want C licences, how to i get c licencese pls reply me iam in critical situation thank you karthick 9841637803

0 Answers  

---

wish of these transformer uses oil?

0 Answers   FJ International,

---

In Ferantti Effect Receiving end voltage is greater than sending end voltage but how it is possible. I know its all about charging current but give me some more detailed explaination?

3 Answers  

---

how to differentiate a mpcb,mcb with a contactor? Explain their working operation

0 Answers   L&T,

---

why celing fan is running in anti clock wise and table fan is running in clock wised?

2 Answers   Ambuja, Infosys, MAHINDRA,

---

Utility company give the supply to customer in KVA but bill them for Watt.why?

1 Answers   L&T,

---

What are the role of each components in PID COntroller

1 Answers   BARC,

---

how does a tube light choke working?

2 Answers  

---

How to convert from HP to BHP please explain????????

1 Answers  

---

HOW TO CALCULATE GROUND FAULT CURRENT IN 430V 4000AMP AIR CIRCUIT BREAKER?

2 Answers  

---