R1 R2 Calculator

Resistance Split Calculator from Ze and Zs

Input Fields

Total circuit impedance

Zₑ

Ω

Total earth fault loop impedance

Source impedance

Zₛ

Ω

Impedance of the supply transformer/source

CalculateReset

Calculate automaticallyIf enabled, the result will update automatically when you change any value.

Your Results

R1 + R2

Leave a Comment

How did this result make you feel?

0😀 Like 0💡 Helpful 0😕 Confused 0😞 Disappointed 0❌ Inaccurate

R1 and R2 Calculation Formulas

$$R_1 + R_2 = Z_s – Z_e$$ $$\text{Assuming } R_1 = R_2: \quad R_1 = R_2 = \frac{Z_s – Z_e}{2}$$

Where:

• $$Z_s$$ = total system impedance (Ω)
• $$Z_e$$ = external impedance (Ω)
• $$R_1$$ = line resistance (Ω)
• $$R_2$$ = CPC resistance (Ω)

These formulas assume a symmetrical line where $$R_1$$ and $$R_2$$ contribute equally to the difference between $$Z_s$$ and $$Z_e$$.

R1 R2 – Calculation Example

Given:

• $$Z_s$$ = 0.76 Ω
• $$Z_e$$ = 0.34 Ω

Calculation:

1. $$R_1 + R_2 = 0.76 – 0.34 = 0.42~\Omega$$
2. $$R_1 = R_2 = \frac{0.42}{2} = 0.21~\Omega$$

The $$R_1$$ and $$R_2$$ test is part of the electrical installation safety procedure to ensure proper earth continuity and minimal resistance. This calculator is useful for quickly verifying the integrity of wiring and connections in TN systems. It supports the design and validation of circuit protection setups to comply with safety regulations and standards such as BS 7671 (UK Wiring Regulations).