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BSI PD IEC/TR 60909-4:2021:2022 Edition

BSI PD IEC/TR 60909-4:2021:2022 Edition

$215.11

Short-circuit currents in three-phase AC systems – Examples for the calculation of short-circuit currents

Published By Publication Date Number of Pages
BSI 2022 84
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PDF Pages PDF Title
2 undefined
4 CONTENTS
8 FOREWORD
10 1 Scope
2 Normative references
3 Terms and definitions, symbols and indices, and formulae
11 4 Positive-sequence, negative-sequence and zero-sequence impedances ofelectrical equipment
4.1 General
4.2 Overhead lines, cables and short-circuit current-limiting reactors
Figures
Figure 1 – Positive-sequence and zero-sequence impedances of an overhead line (one circuit) and cable (cross-bonded)
12 4.3 Transformers
4.3.1 General
Figure 2 – Positive-sequence and zero-sequence impedance of a short-circuit current-limiting reactor
13 Figure 3 – Positive-sequence and zero-sequence system impedances of a two-winding transformer YNd5
14 Tables
Table 1 – Examples for equivalent circuit-diagrams of transformers in the positive-sequence and the zero-sequence system
17 4.3.2 Example
Figure 4 – Equivalent circuits of a three-winding network transformer
Table 2 – Approximations for the ratios X(0)T/XT of two- and three-winding transformers
19 4.4 Generators and power station units
4.4.1 General
21 Figure 5 – Short circuit at the high-voltage side of a power station unit with on-load tap changer
22 4.4.2 Example
24 5 Calculation of short-circuit currents in a low-voltage system Un = 400 V
5.1 Problem
5.2 Determination of the positive-sequence impedances
5.2.1 Network feeder
Figure 6 – Low-voltage system Un = 400 V with short-circuit locations F1, F2, F3
25 5.2.2 Transformers
Table 3 – Data of electrical equipment for the example in Figure 6 – Positive-sequence and zero-sequence impedances (Z(2) = Z(1))
26 5.2.3 Lines (cables and overhead lines)
5.3 Determination of the zero-sequence impedances
5.3.1 Transformers
27 5.3.2 Lines (cables and overhead lines)
5.4 Calculation of I”k and ip for three-phase short circuits
5.4.1 Short-circuit location F1
28 Figure 7 – Positive-sequence system (according to Figure 6) for the calculation of I”k at the short-circuit location F1
29 5.4.2 Short-circuit location F2
30 5.4.3 Short-circuit location F3
5.5 Calculation of I”k1 and ip1 for line-to-earth short circuits
5.5.1 Short-circuit location F1
31 5.5.2 Short-circuit location F2
5.5.3 Short-circuit location F3
Figure 8 – Positive-sequence, negative-sequence and zero-sequence system with connections at the short-circuit location F1 for the calculation of I”k1
32 5.6 Collection of results
Table 4 – Short-circuit impedances and short-circuit currents
Table 5 – Joule integral depending on Tk at the short-circuit location F2 and F3
33 6 Calculation of three-phase short-circuit currents in a medium-voltage system – Influence of asynchronous motors
6.1 Problem
6.2 Complex calculation with absolute quantities
34 Figure 9 – Medium-voltage network 33 kV/6 kV: data
35 Table 6 – Calculation of the short-circuit impedances of electrical equipment and Zk(T1,T2) at the short-circuit location F, without motors (circuit-breakers CB1 and CB2 are open)
37 6.3 Calculation with per-unit quantities
38 Table 7 – Calculation of the per-unit short-circuit reactances of electrical equipment and *Xk(T1,T2) at the short-circuit location F
39 6.4 Calculation with the superposition method
41 Figure 10 – Short-circuit current I”K(T1,T2)S calculated by the superposition method (S) compared with I”K(T1,T2)IEC calculated by the IEC method of equivalent voltage source at the short-circuit location, depending on the load Sb and the voltage Ub
42 7 Calculation of three-phase short-circuit currents for a power station unit and the auxiliary network
7.1 Problem
Figure 11 – Short-circuit current I”KS calculated by the superposition method (S) compared with calculated by the I”kIEC method of equivalent voltage source at the short-circuit location, depending on the transformation ratio t before the short circuit
44 Figure 12 – Power station unit (generator and unit transformer with on-load tap-changer) and auxiliary network with medium- and low-voltage asynchronous motors: data
45 7.2 Short-circuit impedances of electrical equipment
7.2.1 Network feeder
7.2.2 Power station unit
46 7.2.3 Auxiliary transformers
47 7.2.4 Low-voltage transformers 2,5 MVA and 1,6 MVA
49 Table 8 – Data of transformers 10 kV/0,73 kV and 10 kV/0,42 kV, data of low-voltage motor groups and partial short-circuit currents of these motor groups on busbars B and C respectively
50 Table 9 – Data of medium-voltage asynchronous motors and their partial short-circuit currents at short-circuit locations on busbars B and C respectively
51 7.2.5 Asynchronous motors
7.3 Calculation of short-circuit currents
7.3.1 Short-circuit location F1
52 7.3.2 Short-circuit location F2
53 7.3.3 Short-circuit location F3
54 Figure 13 – Positive-sequence system for the calculation of the short-circuit currents at the location F3 (see Figure 12)
57 7.3.4 Short-circuit location F4
Figure 14 – Positive-sequence system for the calculation of the short-circuit currents at the location F4 (see Figure 12)
59 7.3.5 Short-circuit location F5
Figure 15 – Positive-sequence system for the calculation of the short-circuit currents at the location F5 (see Figure 12)
61 8 Calculation of three-phase short-circuit currents in a wind power plant
8.1 General
8.2 Problem
62 8.3 Data and short-circuit impedances of electrical equipment
Figure 16 – Windfarm with ten wind power station units
63 Table 10 – Data and impedances of the electrical equipment (see Figure 16) referred to the 20 kV side
64 8.4 Nodal admittance and nodal impedance matrices
Table 11 – The diagonal elements of the nodal admittance matrices for the three variants in 1/Ω
65 8.5 Short-circuit currents for the wind power plant with ten wind power station units WD
Table 12 – Short-circuit impedances and short-circuit currents at F1 to F14 for wind power stations units with doubly fed asynchronous generators WD
66 Figure 17 – Equivalent circuit diagram for the calculation of the short-circuit current at the location F1 without the consideration of the internal wind power plant cables (values are related to the 20 kV voltage level), variant 1
Table 13 – Short-circuit impedances and short-circuit currents at F1 to F3 for wind power stations units with doubly fed asynchronous generators WD neglecting the internal wind power plant cables
67 8.6 Short-circuit currents for the wind power plant with ten wind power station units WF
68 Table 14 – Quotients Zij/ZkFi for i = 1 to 14 and j = 3…6, 8…10, 12…14 and the sum of the columns
Table 15 – Short-circuit impedances and short-circuit currents at F1 to F14 for wind power stations units with full size converters WF
69 Figure 18 – Equivalent circuit diagram for the calculation of the short-circuit current at the location F1 without the consideration of the internal wind power plant cables (values are related to the 20 kV voltage level), variant 2
70 8.7 Short-circuit currents for the wind power plant with five wind power station units WD and five wind power station units WF
Table 16 – Short-circuit impedances and short-circuit currents at F1 to F3 for wind power stations units with full size converters WF neglecting the internal wind power plant cables
71 Table 17 – Quotients Zij/ZkFi for i = 1 to 14 and j = 3, 10, 12, 13, 14 and the sum of the columns
Table 18 –Short-circuit impedances and short-circuit currents at F1 to F14 for five wind power stations units with doubly fed asynchronous generators WD and five wind power station units with full size converters WF
72 Figure 19 – Equivalent circuit diagram for the calculation of the short-circuit current at the location F1 without the consideration of the internal wind power plant cables (values are related to the 20 kV voltage level), variant 3
73 Table 19 – Short-circuit impedances and short-circuit currents at F1 to F3 for five wind power stations units with doubly fed asynchronous generators WD and five wind power station units with full size converters WF neglecting the internal wind power plant cables
74 9 Test network for the calculation of short-circuit currents with digital programs in accordance with IEC 60909-0
9.1 General
75 9.2 High-voltage test network 380 kV/110 kV/30 kV/10 kV
9.2.1 Network topology and data
76 Figure 20 – High-voltage AC test network 380 kV/110 kV/30 kV/10 kV
78 9.2.2 Short-circuit impedances of electrical equipment
Table 20 – Overhead lines and cables
79 9.3 Results
9.3.1 General
Table 21 – Impedances (corrected if necessary) of the electrical equipment (see Figure 20) referred to the 110 kV side with Z(2) = Z(1)
80 9.3.2 Three-phase short-circuit currents
9.3.3 Line-to-earth short-circuit currents
Table 22 – Results I”k, ip, Ib and Ik
81 Table 23 – Results I”k and ip1
82 Bibliography

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BSI PD IEC/TR 60909-4:2021
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