Polarisation Index (IR / PI)

Polarisation Index = R₁₀min / R₁min from a megger test. IEEE 43 minimum acceptable PI ≥ 2.0 for most machines.

ElectricalInsulation

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

PI = \frac{R_{10 \text{ min}}}{R_{1 \text{ min}}}, \quad DAR = \frac{R_{60 \text{ s}}}{R_{30 \text{ s}}}

Symbol	Meaning	Unit
$R_{t}$	Insulation resistance at time t	MΩ
$PI$	Polarisation index
$DAR$	Dielectric absorption ratio

Source: IEEE 43 - Recommended Practice for Testing Insulation Resistance

Polarisation Index = R\u2081\u2080min / R\u2081min from a megger test.