Answer / yusuf

Buchholz and Pressure relays such as Over Surge Relays are
also known as Gas operated relays... Consider an internal
fault such as inturturn fault in the transformer winding,
then the oil temperature raises which in turn produces Gas
inside the Oil Tank.. This Gas passes through the pipe
connected between Oil Tank and Conservator Tank and relay is
placed in the pipe work... so the Gas passes through the
relay and gives an alarm first and then trips the
transformer when the fault is severe.... Differential
protection is based on the principle of Differential current
which compares the current at the two sides ( LV & HV )of
the Trafo... And that's the reason the Differential
protection does not operate for incipient (Slow developing)
Faults

Answer / s.panneer selvam

I agree with the answer but i found that the differential relay is high impedance relay, in which we cannot used differential relay for transformer internal fault. Because due to mismatch in CT's and lead connection ur circuit will trip spuriously even if there is no abnormality when CT are requested for 100% protection. so we compelled to use some stabilizing resistor which creates non operative zone for some part of winding.where a incipient faults are not continous fault which exists in circuit , it is discontinuous fault after some it may not be in circuit. 

21. What is the purpose of taking Capacitance and Tan Delta Test in Transformer bushing? 22. What are the protections to be used for Generator? 23. Draw the vector diagram and condition for the following: 1) Dyn1 2) Ynd0 3) YnYn0 24. What happens when the polarity changes in CT? Explain briefly? 25. Explain the Term in CT Name Plate – Class: 5P10

3 Answers  

---

Why A.C. capacity given in Ton. Ex. - 1.5 Ton

4 Answers   Samsung, UltraTech,

---

phase colour is indicated by R Y B (red yellow blue) but in transformer i have seen U V W instead of (R Y B) have any meaning of this

3 Answers   Areva, Kim Yew,

---

as we see that in our country the power rating for transmission is always rated in multiple of 11 like 11kv,33kv,66kv132kv. So i want to know wht is reason or logic here.

2 Answers  

---

What is method of calculating the fault current for a MDB, 50KW, 3PH, 415V, 50HZ?

0 Answers   L&T,

---

---

In the transformer, in which form we see the losses of transfprmer ?

3 Answers  

---

1 tr is equal to how many Kw .is there any specific formula for this to get the result .

13 Answers   Cipla, LG, NSN,

---

what are the main problems that happen in an emergency light and how to fix them ?

2 Answers  

---

What is the basic working principle of Tri vector meter?

5 Answers   TCS,

---

Why DC excitation is used for alternators? Why cant it be AC?

35 Answers   ABB, Ace Info, Alstom, Shalivahana Power,

---

Difference between SHORT CIRCUIT and an OVERLOAD ?

1 Answers  

---

Can any one give an explanation about rating factors of cable? if we are laying the cable on the air with an temp 15 degree then rating factors will be 1.15 and if we are laying the cable on the air an temp 60 degree then rating factor will be 0.76 please describe it and what is the difference between rating factor and derating factor?

0 Answers  

---