Maximum short-circuit current with transformer substation

Power net fault *

MVA

Primary voltage *

Secondary voltage *

Transformer power *

kVA

Voltage fault *

Joule effect losses *

Medium voltage line length *

Line type *

Medium voltage wire size *

Medium voltage conductors in parallel *

Conductor *

Low voltage line length *

Low voltage wire size *

Low voltage conductors in parallel *

Conductor *

Description

This tool calculates the maximum symmetrical short-circuit current at the output of a transformer substation, based on IEC 60865 and IEEE C37.100 standards. Results are essential for selecting circuit breakers, fuses, busbars, and cables, as well as verifying equipment’s short-circuit withstand capability.

Input Parameters

Power Net Fault (MVA): Short-circuit power of upstream network, indicating source strength. Higher values lead to higher fault currents.
Primary Voltage (kV): Rated voltage on the high-voltage side of the transformer (e.g., 10 kV, 20 kV, 35 kV).
Secondary Voltage (V): Rated voltage on the low-voltage side (typically 400 V or 220 V).
Transformer Power (kVA): Apparent power rating of the transformer.
Voltage Fault (%): Short-circuit impedance percentage (U_k%), provided by manufacturer. Key factor in determining fault current.
Joule Effect Losses (%): Load loss as a percentage of rated power (P_c%), used to estimate equivalent resistance.
Medium Voltage Line Length: Length of MV feeder from transformer to load (in m, ft, or yd), affecting line impedance.
Line Type: Choose conductor configuration:
- Overhead line
- Unipolar cable
- Multipolar cable
Medium Voltage Wire Size: Conductor cross-section, selectable in mm² or AWG, with Copper or Aluminum material options.
Medium Voltage Conductors in Parallel: Number of identical conductors connected in parallel; reduces total impedance.
Conductor Material: Copper or Aluminum, affecting resistivity.
Low Voltage Line Length: Length of LV circuit (m/ft/yd), usually short but significant.
Low Voltage Wire Size: Cross-sectional area of LV conductor (mm² or AWG).
Low Voltage Conductors in Parallel: Number of parallel conductors on the LV side.

Output Results

Three-phase short-circuit current (Isc, kA)
Single-phase short-circuit current (Isc1, kA)
Peak short-circuit current (Ip, kA)
Equivalent impedance (Zeq, Ω)
Short-circuit power (Ssc, MVA)
Reference Standards: IEC 60865, IEEE C37.100

Designed for electrical engineers, power system designers, and safety assessors conducting short-circuit analysis and equipment selection in low-voltage distribution systems.

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