Interested to Buy Any Domain ? << Click Here >> for more details...
Answer Posted / satya
None of these answers is precise, except ans 2 to large extent.
OK. LBB is Local Breaker Backup. (This is opposed to Remote Back up.)
What is LBB?
First of all here is the philospohy that must be met for LBB.
1)There must be a fault. ( Or more precisely, a protective relay has issued a command to trip the breaker)
2) But that breaker has failed to trip.
Then LBB scheme disconnects other breakers at that station ( Local).
If LBB fails to isolate ( assuming an elemnt is still connected while others have opened) , the remote end stations breakers connected to this station will trip ( Remote Backup)
An LBB scheme thus ensures
1) The relay commanded trip on fault. ( NO contacts of main trip relay used)
2) That there was a current of rasonable amount after some reasonable time. ( Breaker did not open for that much time)
eg we set 200ms time. If so it means that the breaker still has current flowing after 200ms means it failed.
Then the LBB relay will issue a trip signal to other breakers at that bus.
OK Explain well in interview.
OK just a supplement. Should LBB operate if the breaker fails to open on manual command ( not fault)? Think about it.
| Is This Answer Correct ? | 9 Yes | 4 No |
Post New Answer View All Answers
sourse is 66 KV / 350 MVA, transfarmer is 1000 KVA 6.6 / 0.415 kv, iF fault is 28.75 MVA on 0.415 KV Bus then calculat the Transfarmer Impidance
As we use capacitior bank in 3ph ckt for improvement of PF, why not we use capacitor in single phase domestric use, at our house their are many inductive equipments,like fan,mixer,tube choke,air conditioner they also draw PF... by using capacitor can they improve PF. if yes--what are advantage and how to connect a capactor in single ph,and which type of capacitor if no- what are disadvantages.
Why do power lines not short out when they fall into water?
What is the height of DA, DAL, DB, DC & DDE tower?
How to confirm the Phase shifting Transformer VECTOR GROUP relation , as below ZNy11.45d10.45-ZNYy0.15d11.15
delta motor winding resistance I take normally single winding is 2.5, which value is came delta connection ie RY ?
sir iam from electrical and electronics branch ,can i appear for the hpcl offline requirtment? if yes please mail me on vikram_raju25@yahoo.co.in
single phase power supply give to separate one steel coup with water, what reaction create
how much winding resistance of 0.75kw to 12.5kw 3ph sqwiralcage induction motor?
What is the difference between earth fault protection of motor feeder with CBCT and Without CBCT ?
induction 3 phase motor terminal connection
difference between servo motor and synchronous motor
WHAT IS LOAD CELL
I WANT YHE TECHNICAL AND ELECTRICAL SPECIFICATIONS OF 2x4MW 11KV 2x10MW 11KV 2x25MW 11KV 2x100MW 11KV HYDEL POWER PLANT i.e PROTECTION SYSTEM,MONITORING,CONTROL SYSTEM,GENERATION,SYNCHRONISATION,METERING PLEASE SEND THE DETAILS TO MY MAIL ID SPRAVEEN_222@YAHOO.CO.IN
Why saturation region slowly shifted in the left side?
