fault level calculations
TRANSCRIPT
Fault Level Calculations
Fault Level Calculations 2
What is ahead?
• Overview of transmission network.
• What is mean by fault level
• PU Concept
• Network Modeling
• Fault Level Calculation
• Example
Fault Level Calculations 3
Step-1Overview of power system
grid and transmission network
Fault Level Calculations 4
Typical State Level Power System & our area of interest
Fault Level Calculations 5
Typical State Level Power System & our area of interest
Fault Level Calculations 6
400kV
220kV
220kV
132kV
33kV
33kV220kV
132kV
11kV33kV
S/S - A
S/S - F S/S - E
S/S - B
S/S - C
S/S - D
Local Network – or – Sub-Transmission System
Fault Level Calculations 7
Step-2What is mean by fault level
Fault Level Calculations 8
What is fault level
ABC Transmission Co. Ltd.
3 Ph Fault Levels For 2010-2011
14530 MVA
18290 MVA
9700 MVA
8400 MVA
11300 MVA
4630 MVA
5800 MVA
6400 MVA
7200 MVA
2700 MVA
1185 MVA
3670 MVA
9730 MVA
S/S - B
S/S - A
S/S - C
14530 MVA
8400 MVA
9730 MVA
S/S - B
Fault Level Calculations 9
What is fault level-Continued….
14530 MVA
9730 MVA
S/S - B
2200 MVA 2200 MVA 2300 MVA
2450 MVA 2450 MVA
1465 MVA1465 MVA
8700 MVA
1030 MVA
Fault Level Calculations 10
Step-3Understanding Per-Unit
Measurements
Fault Level Calculations 11
PU Concept
• PU impedance values are calculated by
– For Transformers
• %Impedance = Ohmic Value * ( Base MVA / Name Plate MVA )
– For Lines
• %Impedance = Ohmic Value * ( Base MVA / BasekV2 )
Fault Level Calculations 12
PU Concept
• PU impedance values are calculated by
– For Transformers
• %Impedance = Ohmic Value * ( Base MVA / Name Plate MVA )
– For Lines
• %Impedance = Ohmic Value * ( Base MVA / BasekV2 )
Fault Level Calculations 13
PU Concept
400/220 kV
15% 315 MVA
12 Ohm
Sec DSec CSec B
0.4 ohm/Km 200 Km
0.4 ohm/Km 50 Km220/132 kV
14% 200 MVA
132/33 kV
9.33% 25 MVA
0.4 ohm/Km 30 Km
Sec A
Base MVA = 200 MVA
400kV 33kV132kV220kV
T1 L1 T2 L2 T3 L3
Fault Level Calculations 14
PU Concept
400/220 kV
15% 315 MVA
L3T3L2T2L1T1
0.4 ohm/Km 200 Km
0.4 ohm/Km 50 Km220/132 kV
14% 200 MVA
132/33 kV
9.33% 25 MVA
0.4 ohm/Km 30 Km
Fault Level Calculations 15
Short Circuit Current
• 3 Phase Short Circuit MVA at fault point
Base MVA x 100 = ----------------------------------------------------
Percentage Impedance (from source to fault point)
Fault Level Calculations 16
PU Concept-Continued
9.52% 33.05% 14% 22.96% 74.64% 220%
XT1 XL1 XL2 XL3XT2 XT3
Fault Level Calculations 17
PU Concept
400/220 kV
15% 315 MVA
12 Ohm
65 Ohm20 Ohm34 Ohm80 Ohm75 Ohm
0.4 ohm/Km 200 Km
0.4 ohm/Km 50 Km220/132 kV
14% 200 MVA
132/33 kV
9.33% 25 MVA
0.4 ohm/Km 30 Km
Fault Level Calculations 18
Step-4Finding Source Impedance
Fault Level Calculations 19
Typical State Level Power System & our area of interest
4630
Base MVA=Xs(pu)
MVA
100 Xs(pu)4630
Xs (pu) = 0.0216
Or
Xs% = 2.16%
Fault Level Calculations 20
Solved Example
2850 MVA
8 Km
0.4 Ohms / Km
5 Km
0.4 Ohms / Km
50 MVA 10.21%
50 MVA 10.88 %
25 MVA 9.73 %
25 MVA 10.04 %
50 MVA 10.21%
50 MVA 10.88 %
25 MVA 9.73 %
25 MVA 10.04 %
50 MVA 10.03%
25 MVA 10.52 %
25 MVA 10.21 %
25 MVA 9.84 %
220/132kV Padegaon
132/33-11 kV Harsool
132/33-11 kV Chikalthana
132kV 33kV
11kV
132kV 33kV
11kV
Fault Level Calculations 21
Solved Example
2850 MVA
668 MVA
2257 MVA
220/132kV Padegaon
132/33-11 kV Harsool
132/33-11 kV Chikalthana
132kV 33kV
11kV
132kV 33kV
11kV
1998 MVA
538 MVA
Fault Level Calculations 22
Unsymmetrical Faults-Sequence Network
• Up till now we have discussed 3 Phase faults which are rear. Most of the fault in power system are single line to ground faults.
• To find out the short circuit MVA due to single phase to ground fault it is necessary to use Sequence Network
• Let us have a closer look of sequence network
Fault Level Calculations 23
Unsymmetrical Faults-Sequence Network
M1
M2
T2 L GT1
Xg1XT11XL1XT21
XM21XM11
Xg2XT12XL2XT22
XM22XM12
Xg0XT10XL0XT20
XM20XM10
F
FF
SLD
+Ve Sequence Network
-Ve Sequence NetworkZero Sequence Network
Fault Level Calculations 24
Single Line to Ground Fault-Sequence Network Connections
Xg1XT11XL1XT21
XM21XM11
F
Xg2XT12XL2XT22
XM22XM12
F
Xg0XT10XL0XT20
XM20
F
X1
X2
X0
Ia = 3 / (X1 + X2 + X0)
Fault Level Calculations 25
Single Line to Ground Fault-Solved Example
3Ph 2850 MVA
8 Km
0.4 Ohms / Km
5 Km
0.4 Ohms / Km
50 MVA 10.21%
50 MVA 10.88 %
25 MVA 9.73 %
25 MVA 10.04 %
50 MVA 10.21%
50 MVA 10.88 %
25 MVA 9.73 %
25 MVA 10.04 %
50 MVA 10.03%
25 MVA 10.52 %
25 MVA 10.21 %
25 MVA 9.84 %
220/132kV Padegaon
132/33-11 kV Harsool
132/33-11 kV Chikalthana
132kV 33kV
11kV
132kV 33kV
11kV
1Ph 2230 MVA
Fault Level Calculations 26
Single Line to Ground Fault-Solved Example
3Ph 2850 MVA
3Ph 2850 MVA
1Ph 2230 MVA
3*BaseMVA*100
( XS0 + (XL10 || XL20) )2*( XS1 + (XL11 || XL21) )( )+
1 Ph Short Circuit MVA
at 132kV Harsool Bus
Fault Level Calculations 27
Solved Example220/132kV Padegaon
132/33-11 kV Harsool
132/33-11 kV Chikalthana
132kV 33kV
11kV
132kV 33kV
11kV
1998 MVA
538 MVA
3Ph 2850 MVA
1Ph 2230 MVA
3Ph 2257 MVA
1Ph 1662 MVA
3Ph 668 MVA
1Ph 604 MVA
Fault Level Calculations 28