Calculation Of Total Impedance Up To Remote Busbar - GE MiCOM P40 Agile Technical Manual

P543i/P545i
6.4

CALCULATION OF TOTAL IMPEDANCE UP TO REMOTE BUSBAR

Z = Z + Z :
T S L
= 8.988+ j50.917 ohms =51.7 ohms angle 80°
6.5 CALCULATION OF THROUGH FAULT X/R RATIO
X/R = 50.917 / 8.988 = 5.66
through
6.6 CALCULATION OF THROUGH FAULT CURRENT
I = 230kV / (1.732
f through
6.7 CALCULATION OF LINE IMPEDANCE TO ZONE 1 REACH POINT
Z = 0.8ZL = 7.12 + j 38.08 = 38.73 ohms angle 79.4°
zone 1
6.8 CALCULATION OF TOTAL IMPEDANCE TO ZONE 1 REACH POINT
Z = Z + Z zone 1 = 7.208 + j 41.397 = 42.019 ohms angle 80°
T zone 1 S
6.9 CALCULATION OF X/R TO ZONE 1 REACH POINT
X/R = 41.397 / 7.208 = 5.74
zone 1
6.10 CALCULATION OF FAULT CURRENT TO ZONE 1 REACH POINT
I = 230kV / (1.732
f zone 1
6.11 CALCULATION OF VK FOR CURRENT DIFFERENTIAL PROTECTION
Transient Bias Disabled, with k2 set to 150%
´ X/R = 2.14 ´ 5.66 = 12.11
I
f through through
As this is less than 1000, we use the highest of K = 65 or K = 40 + (0.07(I
Hence in this example we use K = 65. Therefore:
³ KI
We know that V (R
k n CT
³ 65(R
V + 2R )
k CT L
Transient Bias Enabled, with k2 set to 150%
K = (1.42 ´ 2.14 + 53.7)(6.06E-03 ´ 5.66 + 0.515) = 31.2, therefore
³ 31.2(R
V + 2R )
k CT L
6.12 CALCULATION OF VK FOR DISTANCE ZONE 1 REACH POINT
³ K ´ I
Using: V (1+ X/R)(R
k RPA fZ1
> 0.6 ´ 2.63 ´ (1 + 5.74)(R
V
k
V > 10.65(R + R )
k CT L
P54x1i-TM-EN-1
´ 51.7) = 2568.5 A primary = 2.14 A secondary
´ 42.019) = 3160.34 A primary = 2.63 A secondary
+ 2R ), therefore
L
+ R )
CT L
+ R ), therefore:
CT L
Chapter 16 - Current Transformer Requirements
´ X/R))
f
425