Short-circuit currents per IEC 60909 and IEEE C37.010
Short-circuit currents at the HV and MV buses, with the equipment ratings checked against the results. The method follows the standards set of the project.
Fault calculations and rating checks
The currents are checked against the equipment ratings and set the grid current. The report shows the sequence impedances and each equation with its clause.
- At the HV and MV buses, or at both HV buses of a switching substation
- Maximum and minimum currents, with the plant infeed in the maximum case
- Sequence impedances of the grid, lines and transformers
- Rating checks per standards set, below
- Calculation trail per step: equation, input values, result and clause
- Calculation report in PDF
Method and checks per standards set
The network and the reports have one form on both sets. The equations, voltage basis and rating checks follow the standards set of the project.
| Item | IEC, CEA and CBIP | ANSI, IEEE and NESC |
|---|---|---|
| Method | IEC 60909-0:2016 | IEEE C37.010-2016 E/X method, with E/Z for E/X (§5.2.1) |
| Voltage basis | Maximum currents with c = 1.10, minimum currents with c = 1.00 | Maximum currents at the level's maximum system voltage, minimum currents at 1.0 per unit |
| Faults | 3-phase, 2-phase, 1-phase-to-earth and 2-phase-to-earth | Three-phase and line-to-ground, with the ac and dc decrement adjustment |
| Results | Initial symmetrical, peak and thermal equivalent currents | Interrupting current, closing and latching current, short-time current and dc time constant |
| Rating checks | CB breaking and making current, short-time current, earth-mat design current | Breaker ratings per IEEE C37.04-2018 Tables 8, 12 and 16, ground grid design current |
| Plant infeed | Converter plant infeed, or power station units per IEC 60909-0:2016 §6.7.1 for synchronous plants | Converter plant infeed |
Results, 220/33 kV pooling substation
The fault currents are below the ratings of the circuit breakers. Sample design per IEC, CEA and CBIP.
- 220 kV peak current (ip)
- 62.17 kA
- 33 kV peak current (ip)
- 68.58 kA
- 220 kV 1-phase-to-earth fault
- 20.24 kA
- 220 kV 2-phase fault
- 18.32 kA
- 220 kV 2-phase-to-earth fault
- 20.87 kA
- 220 kV 3-phase fault, minimum
- 19.23 kA
Equation, input values, result and clause per step
The calculation trail shows how the design reaches its currents, from the network and transformer impedances to the rating checks.
- 1Network feeder impedanceIEC 60909-0:2016 §6.2 Eq. 4–5I″kQ 40 kA, grid X/R 15, cmax 1.1ZQ1 = 0.232 + j3.485 Ω
- 2Line impedanceIEC 60909-0:2016 §6.41 × 10 km Twin ACSR MooseZL1 = 0.280 + j3.100 Ω
- 3Transformer impedance with correctionIEC 60909-0:2016 §6.3.1 Eq. 7, §6.3.3 Eq. 12a2 × 160 MVA, uk 12.5 %, X/R 40KT = 0.9721, ZT1 = 0.919 + j36.747 Ω
- 4Plant infeedIEC 60909-0:2016 §6.9k 1.2, plant 263 MVA829 A at 220 kV
- 5Initial symmetrical currentIEC 60909-0:2016 §7.2 Eq. 29220 kV Z1 0.512 + j6.585 Ω, 33 kV Z1 0.032 + j0.975 Ω220 kV 21.98 kA, 33 kV 24.25 kA (per section)
- 6Peak currentIEC 60909-0:2016 §8.1.1 Eq. 54, §8.1.2 (κ, method B)κ 2.000 (220 kV), 2.000 (33 kV)220 kV 62.17 kA, 33 kV 68.58 kA
- 7Thermal equivalent currentIEC 60909-0:2016 §10 Eq. 100tk 1.00 s (220 kV), 3.00 s (33 kV), m 0.044 (220 kV), 0.034 (33 kV)220 kV 22.46 kA, 33 kV 24.66 kA
- 8Equipment rating checksIEC 62271-100:2008 §4.101, §4.103220 kV 50 kA, 33 kV 31.5 kA, kmake 2.5 at 50 Hz7 of 7 checks pass
Short-circuit calculation report
The report states the inputs, the sequence impedances, the maximum and minimum currents, the plant infeed and the rating checks.
