Shielding Failure SFR and SFFOR - All Electron - All about High Voltage systems

Shielding failure calculation (SFR & SFFOR) using LPM method

This tool lets you calculate the Shielding Failure Rate (SFR) and Shielding Failure FlashOver Rate (SFFOR) of a 3-phase single or multi circuit transmission line using the simplified Leader Progression Model (as described in CIGRÉ TB 839) and graphically visualizes the result. For the lateral striking distance, the values of Brown–Whitehead are applied. For lightning distribution reference is made to CIGRÉ TB 839 & TB 063.

LPM Tool – Lightning Performance Model

Model setup

Inputs

Background field(kV/m)

Cloud height(m)

Insulator length(m)

Kcor applicable?

Lightning strike density(fl/km²/yr)

Current distribution

Conductors

#	D (cm)	#	Spacing (cm)	V ph-ph (kV)	Angle (°)	X (m)	H (m)

Key outputs

Shielding failure rate (SFR)

Shielding Failure Flash Over Rate (SFFOR)

Number of strikes to tower (N_L)

Results and intermediate values

Geometry & lateral unprotected distance

Phase angle offset: 0°

Lightning current(kA)

Total lateral unprotected distance

Black dots: phase conductors. Green dots: shield wires. Purple: Lds for phase conductors (protected parts). Green: Lds for shield wires. Red: unprotected part of Lds for phase conductors when I ≥ Ic; orange: unprotected part when I < Ic.

Intermediates – per conductor

Intermediates – Rizk core

Intermediates – Lds and Dc per conductor

Intermediates – Dc for all angles

Toggle a curve by clicking its legend. The dot shows the currently active phase angle for each conductor.

Intermediates – Distributions & Ic

Number of steps (3–200 kA):

Critical current for flashover Ic (kA):

I (kA)	ΣDc (m)	P cum	P(step)	ΣDc·P(step) SFR	ΣDc·P(step) SFFOR

Please note: this method simplifies several aspects and is typically used for voltage levels of 400kV and higher. This tool was set up for educational purpose. Want to learn more about this topic? Follow our online training.