Affect of Weak Infeed & powe swing on distance relay 1

[sabap]

How does the problem of weak infeed and power swing on t/line affects a distance relay? Does these have any particular problem with POTT scheme. How are they implemented. What is echo method for weak infeed problem elimination.

I will also appreciate if anyone can give a brief description of weak infeed and power swing in terms of their settings/implementation in a distance protection relay.

Thanks in advance.

 

[Aakhrinaam]

Sabap,
It's best to treat the two issues separately.

Power Swings :

The relay should block the operation of distance elements during power swings (depends on the chosen setting)even though the impedance seen by the relay is inside the characteristic.

The settings for Power swing blocking will be manufavcturer specific. Some measure the speed of the locus of the swing to differentiate it from a fault. Some manufacturers ( Areva/ALSTOM) do not require any settings.



Weak Infeed Echo:

During Weak infeed conditions , one end may not contribute to the fault and hence not see the fault. For permissive schemes to work the other end may need a signal back from the weak end . If echo is enabled at the weak infeed end , it will transmit back (echo) any signal sent by the other end , enabling both ends to trip.

Echo is generally blocked by operation of any reverse looking element at the weak end.

 

[DiscoP]

Look up the "NPAG" product on the areva-td.com website

Chapter 11 has a good explanation of Power Swing Blocking

Chapter 12 Discussed Distance Schemes in detail including POTT and Weak Infeed Echo.

Some distance relays have the logic for these schemes already created (eg MiCOM P441) - the manuals for these relays provide some detailed explanations on the schemes too.

 

[sabap]

I dont know why but i could not open this website from our corporate network. Is this site still functional?
):

 

[DiscoP]

Yep - just checked it again to be sure

The full address is

http://www.areva-td.com

then click on Products and Systems, then find NPAG on the list

 

[sabap]

Got it. Its been updated. I had the older version.

Thanks.s