Transcript Fault Level Calculations

Today’s Session
What is ahead?
• Fault Level Calculations
–
–
–
–
Power-system Overview
PU Concept
3 Ph. Fault Level Calculations
1 Ph Fault Level Calculations
• O/C E/F Relay Time Coordination
– General information about relay characteristic
– Worked out example
• Directional Relay
– What is MTA
– How to confirm direction of relay reach while in
service
Fault Level
Calculations
Fault Level Calculations
What is ahead?
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•
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Overview of transmission network.
What is mean by fault level
PU Concept
Network Modeling
Fault Level Calculation & Worked out
example
– Three Phase Fault
– SLG Fault
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Fault Level Calculations
Step-1
Overview of power system
grid and transmission
network
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Fault Level Calculations
Typical State Level Power System & our area of interest
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Fault Level Calculations
Typical State Level Power System & our area of interest
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Fault Level Calculations
Local Network – or – Sub-Transmission System
400kV
S/S - A
S/S - C
220kV
S/S - B
220kV
132kV
S/S - F
33kV
132kV
11kV
220kV
S/S - E
S/S - D
33kV
33kV
Fault Level Calculations
Step-2
What is mean by fault level
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Fault Level Calculations
What is fault level
S/S - A
S/S - B
14530
MVA
11300
MVA
18290
MVA
9700
MVA
8400
MVA
9730
MVA
6400
MVA
4630
MVA
7200
MVA
5800
MVA
S/S - C
2700
MVA
1185
MVA
3670
MVA
ABC Transmission Co. Ltd.
3 Ph Fault Levels For 2010-2011
Fault Level Calculations
What is fault level-Continued….
S/S - B 2450 MVA
2200 MVA
2450 MVA
2200 MVA
14530 MVA
1465 MVA
2300 MVA
8700 MVA
9730 MVA
1030 MVA
1465 MVA
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Fault Level Calculations
Step-3
Understanding Per-Unit
Measurements
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Fault Level Calculations
PU Concept
• PU impedance values are calculated by
– For Transformers
%ImpedanceNew Base MVA =
Base MVA
% ImpedanceName Plate
Capacity in MVA
– For Lines
Base MVA
%Impedance
=
Ohmic Value
kV 2
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Fault Level Calculations
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
)
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Fault Level Calculations
PU Concept
Base MVA = 200 MVA
Sec A
Sec B
400kV
220kV
Sec C
132kV
T1
L1
Sec D
33kV
T2
L2
T3
L3
12 Ohm
400/220 kV
15% 315 MVA
0.4
ohm/Km
200 Km
220/132 kV
14% 200 MVA
0.4
ohm/Km
50 Km
132/33 kV
0.4
ohm/Km
30 Km
9.33% 25 MVA
Fault Level Calculations
Step-4
Network Modeling
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Fault Level Calculations
PU Concept
T1
400/220 kV
15% 315 MVA
L1
0.4
ohm/Km
200 Km
T2
L2
220/132 kV
0.4
ohm/Km
50 Km
14% 200 MVA
T3
132/33 kV
L3
0.4
ohm/Km
30 Km
9.33% 25 MVA
Fault Level Calculations
Short Circuit Current
• 3 Phase Short Circuit MVA at fault point
Base MVA x 100
= ----------------------------------------------------
Percentage Impedance
(from source to fault point)
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Fault Level Calculations
PU Concept-Continued
XT1
9.52%
XL1
33.05%
XT2
14%
XL2
22.96%
XT3
74.64%
XL3
220%
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Fault Level Calculations
PU Concept
75 Ohm
80 Ohm
34 Ohm
20 Ohm
65 Ohm
12 Ohm
400/220 kV
15% 315 MVA
0.4
ohm/Km
200 Km
220/132 kV
14% 200 MVA
0.4
ohm/Km
50 Km
132/33 kV
0.4
ohm/Km
30 Km
9.33% 25 MVA
Fault Level Calculations
Step-5
Finding Source Impedance,
Worked out Example
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Fault Level Calculations
Typical State Level Power System & our area of interest
4630 MVA
Xs(pu)
Base MVA= 100
4630
Xs(pu)
Xs (pu) = 0.0216
Or
Xs% = 2.16%
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Fault Level Calculations
Solved Example
220/132kV
Padegaon
132kV
2850
MVA
0.4 Ohms / Km
8 Km
33kV
50 MVA
10.21% 132/33-11 kV
Harsool
50 MVA
10.88 %
132kV
25 MVA
9.73 %
25 MVA
10.04 %
11kV
0.4 Ohms / Km
5 Km
132/33-11 kV
Chikalthana
33kV
50 MVA
10.03%
25 MVA
10.52 %
25 MVA
10.21 %
25 MVA
9.84 %
11kV
220/132kV
Padegaon
2850
MVA
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Fault Level Calculations
Solved Example
132kV
2257
MVA
132/33-11 kV
33kV
Harsool
668
MVA
132/33-11 kV
Chikalthana
132kV
11kV
1998
MVA
33kV
538
MVA
11kV
Fault Level Calculations
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
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Fault Level Calculations
Unsymmetrical Faults-Sequence Network
M1
T2
L
T1
G
XM11
M2
XM21
XT21
XL1
SLD
XT11
Xg1
F
+Ve Sequence Network
XM10
XM20
XM12
XT20
XL0
XT10
F
Zero Sequence Network
Xg0
XM22
XT22
XL2
XT12
F
-Ve Sequence Network
Xg2
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Fault Level Calculations
Single Line to Ground Fault-Sequence Network Connections
XM11
XM21
X1XL
XT21
1
XT11
Xg1
XL2
XT12
Xg2
F
XM12
XM22
X2
XT22
Ia = 3 / (X1 + X2 + X0)
F
X0
XM20
XT20
F
XL0
XT10
Xg0
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Fault Level Calculations
220/132kVSingle Line to Ground Fault-Solved Example
Padegaon
132kV
3Ph 2850
MVA
1Ph 2230
MVA
0.4 Ohms / Km
8 Km
33kV
50 MVA
10.21% 132/33-11 kV
Harsool
50 MVA
10.88 %
132kV
25 MVA
9.73 %
25 MVA
10.04 %
11kV
0.4 Ohms / Km
5 Km
132/33-11 kV
Chikalthana
33kV
50 MVA
10.03%
25 MVA
10.52 %
25 MVA
10.21 %
25 MVA
9.84 %
11kV
Fault Level Calculations
Single Line to Ground Fault-Solved Example
3Ph 2850
MVA
1Ph 2230
MVA
3Ph 2850
MVA
1 Ph Short
Circuit MVA at
132kV
Harsool Bus
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3*BaseMVA*100
(
2*( XS1 + (XL11 || XL21) )
+
( XS0 + (XL10 || XL20) )
)
220/132kV
Padegaon
3Ph 2850
MVA
1Ph 2230
MVA
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Fault Level Calculations
Solved Example
132kV
132/33-11 kV
33kV
Harsool
3Ph 2257
MVA
3Ph 668
MVA
1Ph 1662
MVA
1Ph 604
MVA
132/33-11 kV
Chikalthana
132kV
11kV
1998
MVA
33kV
538
MVA
11kV
Fault Level Calculations
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