Answer / rukmagoud

Differential protection requires two cts for its connection.
If one of the CT reaches its Knee point voltage , then the
CT Enters into Saturation. so when Ct is in Saturation
state, its characteristic changes, i.e the current will
not be proportional to primary current thereby
differential current comes into picture in differential
relay , there by there is a chance of maloperation of relay.
This usually comes when there is any through fault.

rukmagoud
APGENCO/NAGARJUNASAGAR

Answer / ramesh p

the differential relay will get maloperation when one of
the CT get saturation

Answer / girish kumar samal, hindalco,h

DIFFERENTIAL PROTECTION FAIL. CT DOES NOT GIVE SECONDARY
CURRENT ACCORDING TO PRIMARY. EOR WHICH DIFFERENTIAL RELAY
OPERATE.

Answer / tony

Normally the knee point voltage must be

Vk > 2*Vs

Where Vs is the calculated max. voltage appears across the relay.

Beyond knee point the chara of CT is no longer proportional to the primary current and this cause faulty measuring by relay.Thus if we have higher Vk we can easily with stand higher Vs(fault equivalent seen by relay)

power factor is max for which welding a.arc b.resistance c.gas

2 Answers   Bhel, HCL,

---

what type of oil is used in transformers? a)conduting b) insulating

25 Answers   ABB, LGS,

---

when we put inducter in neuteral grounding of genrator.

3 Answers  

---

What is Icu and Ics and what is difference b/w them. please tell me how to calculate a size of a copper bar for a system or a breaker... reply on... king.arish@gmail.com would be waiting for a logical answer.

0 Answers  

---

what is the basis for selection of Protection CT class ? How anyone can decide whether to go for 5P10 or 5P20 ?

3 Answers  

---

we all know voltage is a force(emf), and the force always devides if 2 or more than2 loads are there but why does the voltage remains same is parallel, it must devide na ???

0 Answers   NTPC,

---

what r the sizes of CB's? how to select CB's?

1 Answers  

---

If two generator running parallel, at that condition both ngr Taken in line or taken any one ngr, but why any one or both Ngr in line? Ngr is use for which purpose?

3 Answers  

---

why voltage rating of transformers are in multiples of 1.1?

3 Answers  

---

Why most of analog o/p devices having o/p range 4 to 20 mA and not 0 to 20 mA ?

2 Answers  

---

rajha power sector details

0 Answers  

---

what is active power & reactive power?

0 Answers   Avtech, Jindal,

---