Adiabatic Equation CalculatorThe Adiabatic Equation.
✔ Calculates Conductor Size mm²
✔ Calculates la
✔ Calculates I²
✔ Calculates k value
✔ Calculates t (s)
Download the Adiabatic Equation Calculator for iPhone, iPad or Android
The Adiabatic Equation Calculator in an app. Calculate the minimum permissible cpc or earth size using the Adiabatic Equation.
Sizing of protective conductors can be achieved by looking up the relevant table or where required by calculation using the Adiabatic Equation.
Adiabatic Equation Symbols
- S = Conductor Size (mm²)
- Ia = Fault Current (A)
- I² = la Squared
- t = Time (s)
- k = Conductor k Value
Conductor k Value Tables
BS 7671 Values of k for Protective Conductors:
- Table 54.2 – Conductor not incorporated in a cable and not bunched with cables.
- Table 54.3 – Conductor incorporated in a cable or bunched with cables.
- Table 54.4 – Sheath or armour of a cable.
- Table 54.5 – Steel conduit or trunking.
Adiabatic Equation Parameters
- Uo Voltage
- Measured Zs Value
- Protective Device Type & Rating
- Conductor Type
- Conductor Material
Disconnection Time Tables
BS 7671 Maximum Operating Time / Current Characteristics Tables:
- Fig 3A2 (a,b) – BS 3036 Semi-enclosed Fuse
- Fig 3A3 – (a,b) – BS 88-2.2
- Fig 3A4 – BS EN 60898 / 61009-1 MCB/RCBO Type B
- Fig 3A5 – BS EN 60898 / 61009-1 MCB/RCBO Type C
- Fig 3A6 – BS EN 60898 / 61009-1 MCB/RCBO Type D
- BS 1361 Fuse
A great app for electricians and inspectors carrying out electrical testing & inspecting for verifying existing protective conductor sizes.