50/51 51N/50N time grading on radial feeder 3

[newelecteng]

Hi all,

How to set protection (over current and earth fault) in terms of PICKUP and Time (first stage IDMT, second stage DT) on radial feeder shown on attached.
Relay Type:Micom p127
Thanks in advance.

 

[JG2828]

I would start by hiring an EE to do a relay settings and coordination study for you.

Added attachment as inline image:

 

[newelecteng]

Thanks GJ2828,
We need to do realy settings and coordination on 1,2,3,4.

 

[bceng87SS1517]

Need the SC available contribution on line side of breaker #4, then you will need to model the radial feed to include cable size/lengths, breaker types, bus types(swgr or aerial), XFMR nameplate data, type of grounding if either side is has wye windings, resistor size if it is resistively grounded, ratio and location of any CT's and which relay they are connected, type of relays, load specs if you have it for settings on breaker #1.

 

[newelecteng]

Load: 400 amp
CB1: CTR:600:1
CB2: CTR:1200:1
CB3: CTR:400:1
CB4: CTR:400:1
Max SC on 33kv bus=25ka
Xtmr: 20mva 33kv/11kv
all relays is micom p127 relay

 

[Parchie]

Please estimate your impedance of your lines. Without those, you can only guess.

 

[newelecteng]

Hi archie,
Thanks for your response
I don't have line Z
But the transformer Z=8.5% YNyn
Load: 400 amp
CB1: CTR:600:1
CB2: CTR:1200:1
CB3: CTR:400:1
CB4: CTR:400:1
Max SC on 33kv bus=25KA
MAX SC on 11kv bus=8KA
Xtmr: 20mva 33kv/11kv
all relays is micom p127 relay