Short Circuit

This section allows users to configure parameters for short-circuit analysis, including impedance assumptions, voltage tolerances, and generator contributions.

Zero-Sequence Impedance

• Define a factor to relate zero-sequence impedance to positive-sequence impedance.
• Used for calculating impedance in single-phase and two-phase-to-ground faults.
• Default: 1 × positive-sequence impedance (conservative assumption).
• Zero-sequence impedance of the overlying grid is neglected (R₀grid = ∞).

Voltage Tolerance

Affects the voltage correction factors (cₘᵢₙ and cₘₐₓ) for low-voltage buses:

• 0%: cₘᵢₙ = 0.95, cₘₐₓ = 1.05
• 10%: cₘᵢₙ = 0.9, cₘₐₓ = 1.1
• IEC 60909-0:2001: cₘᵢₙ = 0.95, cₘₐₓ = 1.0

Short Circuit Duration

• Set the duration (in seconds) used to calculate thermally equivalent short-circuit currents (Iₜˢ).

Branch Temperature

• Select the assumed temperature of branches at the end of the short circuit:
  • 40°C (highest minimal currents)
  • 80°C
  • 160°F (lowest minimal currents, conservative)

Higher temperatures result in higher impedance and lower short-circuit currents, which may affect protection device performance.

Generator Contribution

• Enable this option to allow generators to contribute to nearby short circuits.
• By default, only the network feeder contributes.
• Generators with specific connection types (e.g., inverter-based) can be included.

These settings help ensure accurate and standards-compliant short-circuit analysis for protection and planning purposes.