Advanced: ED-332 (HVDC aircraft propulsive systems)EUROCAE ED-332 "Guidance on Characteristics of Aircraft Propulsive High Voltage DC Electrical Systems" defines steady-state and abnormal-transient voltage envelopes for 800 VDC-class propulsive networks. Turn this on to size clearance from ED-332's worst-case abnormal voltage transient instead of the continuous working voltage, default the HV-to-chassis voltage from ED-332's abnormal common-mode condition, and see the standard's Dielectric Withstanding Voltage and insulation resistance requirements alongside your IEC 60664-1 results.

1Electrical parameters

Voltage entered asBoth voltage fields below are interpreted the same way. Peak assumes a sinusoidal waveform (Vrms = Vpeak/√2) — for a DC or non-sinusoidal withstand voltage rating, enter RMS directly if you know it rather than relying on this conversion.

Working voltage (V rms)Drives both creepage and clearance directly — the highest voltage actually across the insulation.

Working voltage to chassis (V rms)Defaults to 50% of working voltage — edit to override.

Factor of safety (%)Applied as a margin on top of the standard's calculated minimum distances (default 20%).

Electric field condition (clearance only)Inhomogeneous field (Case A): "Electric field which does not have an essentially constant voltage gradient between electrodes (non-uniform field)" (clause 3.15). Represented by a 30 μm-radius point electrode against a 1 m × 1 m plane — the worst case for voltage withstand. Clearances at or above the Case A values in Table F.2 can be used for any electrode shape/arrangement, without a voltage-withstand test (clause 5.1.3.2) — the safe default.

Homogeneous field (Case B): "Electric field which has an essentially constant voltage gradient between electrodes (uniform field), such as that between two spheres where the radius of each sphere is greater than the distance between them" (clause 3.14). Case B permits smaller clearances, but only where the geometry is specifically designed to achieve this uniform field, and the standard requires it to be verified by an actual voltage-withstand test (clause 5.1.3.3) — don't select it just because the numbers are smaller.

Case A is the safe default usable for any geometry; Case B needs a uniform-field design verified by test.

2Environment

Pollution degreePD1: No pollution or only dry, non-conductive pollution occurs. The pollution has no influence.

PD2: Only non-conductive pollution occurs except that occasionally a temporary conductivity caused by condensation is to be expected.

PD3: Conductive pollution occurs or dry non-conductive pollution occurs which becomes conductive due to condensation which is to be expected.

PD4: Continuous conductivity occurs due to conductive dust, rain or other wet conditions.

PD4 has no creepage table value (IEC 60664-1 4.6.3) — requires enclosure/coating design; clearance still computes with its footnoted 1.6 mm floor.

Material groupIEC 60664-1 classifies insulating materials into four groups by their Comparative Tracking Index (CTI, per IEC 60112 using solution A) — a measure of resistance to surface tracking (the progressive formation of a conductive path from electrical stress + surface contamination): Group I (CTI ≥ 600), Group II (400 ≤ CTI < 600), Group IIIa (175 ≤ CTI < 400), Group IIIb (100 ≤ CTI < 175). Lower CTI (IIIb) needs more creepage distance for the same voltage/pollution degree. Use Group IIIb if the material is unknown.

Group IIIb (100 ≤ CTI < 175). IIIb is the conservative default for unknown/general-purpose plastics.

CTI per IEC 60112. If unknown, use Group IIIb.

Altitudecorrection k = 1

No correction below 2000 m (6562 ft) — that is the standard's native reference condition. Correction applies to clearance only; creepage (a surface-tracking property) is not altitude-dependent.

Reference tables

Required distances (including the 20% factor of safety) at your current working voltage and HV-to-chassis voltage, across every Material Group / Case × Pollution Degree combination — the highlighted cell matches your current selection.

Creepage @ Working Voltage (300 V)

	PD1	PD2	PD3
I	0.83mm	1.80mm	4.53mm
II	0.83mm	2.51mm	5.09mm
IIIa	0.83mm	3.60mm	5.66mm
IIIb	0.83mm	3.60mm	5.66mm

Creepage @ HV to Chassis (150 V)

	PD1	PD2	PD3
I	0.37mm	0.94mm	2.37mm
II	0.37mm	1.30mm	2.61mm
IIIa	0.37mm	1.89mm	2.97mm
IIIb	0.37mm	1.89mm	2.97mm

Clearance @ Working Voltage (0.3 kV, altitude-adjusted)

	PD1	PD2	PD3
Case A	0.01mm	0.24mm	0.96mm
Case B	0.01mm	0.24mm	0.96mm

Clearance @ HV to Chassis (0.15 kV, altitude-adjusted)

	PD1	PD2	PD3
Case A	0.00mm	0.24mm	0.96mm
Case B	0.00mm	0.24mm	0.96mm

Paschen's Law cross-checkconsistent

First-principles physics, independent of the IEC table: air's dielectric breakdown voltage depends on the pressure × gap product (p·d). At 5,000 ft the local pressure is 84.56 kPa (vs 101.33 kPa at sea level) — for a 0.24 mm gap, p·d = 2.029 kPa·cm, well above the Paschen minimum (0.111 kPa·cm), so breakdown voltage still falls monotonically as altitude increases — the IEC table's assumption holds throughout this range.

Breakdown voltage at this gap

1,424V

Min. gap for working voltage

0.005mm

Rib / groove creepage reduction

A rib (raised barrier) or groove (recessed channel) of adequate width lets the standard's required creepage distance be achieved within a smaller flat-surface footprint — the creepage path is measured up-and-over (or down-and-across) the feature rather than straight across it, adding roughly twice its height to the path.

Rib / groove height, H (mm)

Rib / groove width, W (mm)Must be at least 1 mm at PD2 (IEC 60664-1's minimum width for a groove/rib not to be "bridged" in the standard's measurement rule — narrower features are ignored, as if contamination could span the gap). The minimum rises with pollution degree: 0.25mm at PD1, 1.0mm at PD2, 1.5mm at PD3.

Minimum width at PD2: 1 mm. ✓ Meets the minimum — credits 4 mm of additional creepage path (2×H).

Required flat-surface footprint

	Without rib/groove	With rib/groove
Working voltage	3.60mm	0.00mm
HV to chassis	1.89mm	0.00mm

Reference & assumptions

New to IEC 60664-1? Read the guide: Creepage & Clearance: How IEC 60664-1 Sets Insulation Distances — a plain-language explainer of the standard behind this calculator.

Clearance uses IEC 60664-1 Table F.2 (verified against the standard's full text), with a choice of Case A (inhomogeneous field, always usable) or Case B (homogeneous field, smaller clearances but requires geometry designed for a uniform field and verification by voltage-withstand test), plus the table's own footnoted pollution-degree floors (PD2 ≥ 0.2 mm, PD3 ≥ 0.8 mm, PD4 ≥ 1.6 mm — small gaps can be bridged completely by particles/condensation regardless of the voltage a gap otherwise has to withstand). Clearance is driven directly by the working voltage (and separately by the working voltage to chassis), altitude-corrected — this tool does not step the working voltage up through an overvoltage category / rated impulse withstand voltage (IEC 60664-1 Table F.1) first, which is a deliberate simplification that will understate required clearance for circuits exposed to significant transient overvoltages (e.g. direct mains connection) — add your own margin for those. Creepage uses the IEC 60664-1 CTI/pollution-degree methodology (subclause 2.7.1.3) as tabulated in Table F.4, assuming functional insulation throughout (this tool does not model basic/supplementary/reinforced insulation separately). Both creepage and clearance are now power-law interpolated between the standard's tabulated voltage points (rather than taking the next-higher band's more conservative value), since these tables approximate a power law, not a straight line, or a step function. Altitude correction (IEC 60664-1 Table F.10 / Table A.2) is applied only to clearance — cross-checked against standard-atmosphere barometric pressure, and against Paschen's Law directly. Paschen's Law assumes an idealised uniform field between clean electrodes; real-world breakdown voltage is typically lower due to field non-uniformity, surface roughness and humidity — treat it as a physics sanity check, not a substitute for the standard's tested margins. Pollution degree 4 has no creepage table value (enclosure/coating design required) but clearance still computes via its footnoted floor. This tool supports engineering estimation — verify exact values against the current official IEC 60664-1 text, and any applicable product standard, before certification use.

Voltage input mode: both voltage fields can be entered as RMS or as a peak/withstand value — switching modes only changes how the numbers you type are interpreted (Vrms = Vpeak/√2, assuming a sinusoidal waveform); every downstream calculation still uses RMS internally, matching Table F.4's own basis. For a DC or non-sinusoidal withstand rating, enter RMS directly if you know it.

Rib / groove creepage reduction (Premium): a rib (raised barrier) or groove (recessed channel) molded or cut into the insulation surface lets the required creepage distance be met within a smaller flat footprint, since the standard's measurement rule traces the creepage path up-and-over (or down-and-across) the feature rather than straight across it. A feature narrower than IEC 60664-1's pollution-degree-dependent minimum width — 0.25mm at PD1, 1.0mm at PD2, 1.5mm at PD3 (reproduced from the standard's own table, cross-checked against Texas Instruments' "Demystifying Clearance and Creepage Distance for High-Voltage End Equipment" application note, which cites and quotes the same IEC 60664-1 table) — is "bridged" in the standard's measurement: the path is measured straight across as if the feature weren't there, since contamination can span a gap that narrow, giving zero credit. A feature meeting the minimum width credits twice its height as additional creepage path length — the standard engineering approximation for a simple rectangular rib/groove profile (the path travels up one face and down the other, or vice versa), not a literal reproduction of the standard's full set of measurement figures for angled or rounded contours, uncemented joints, or multiple ribs in series, which this tool does not attempt to model.

Validated: checked that the calculator reproduces the standard's own tabulated points exactly at several spot checks (e.g. 1.0 kV Case A → 0.15 mm clearance; 400 V/PD2/Group I → 2.0 mm creepage; 250 V/PD2/Group IIIb → 2.5 mm creepage — all widely-cited reference figures), and that the power-law interpolation between tabulated points was independently re-derived from the documented formula and matches the calculator's output to 5+ significant figures at a non-tabulated voltage (0.7 kV → 0.07889 mm both ways). The rib/groove minimum-width table (0.25/1.0/1.5mm) exactly reproduces the TI application note's own published table; the bridging rule (below minimum → zero credit) and the 2× height credit rule were checked against hand-worked cases including the exact minimum-width boundary (width equal to, not just above, the minimum still counts).

Calculation steps

1. Altitude correction factor (IEC 60664-1 Table F.10)

k = f(altitude), linearly interpolated between tabulated points; k = 1.0 below 2000 m

Altitude = 5,000 ft = 1,524 m

k = 1

2. Altitude-adjusted voltage for clearance (working voltage used directly — no overvoltage-category step-up)

V_clearance = working voltage × k

Working voltage: 300 V × 1 = 300 V. HV to chassis: 150 V × 1 = 150 V

0.3 kV (working) / 0.15 kV (HV to chassis)

3. Required clearance (IEC 60664-1 Table F.2, Case A — inhomogeneous field, PD2 floor) + safety factor

Clearance = max(f(V)^b (ratio-based), pollution-degree floor) × (1 + FoS)

Working voltage: base 0.2 mm (PD floor applied), with 20% margin = 0.24 mm. HV to chassis: base 0.2 mm (PD floor applied), with margin = 0.24 mm

4. Required creepage distance (IEC 60664-1 Table F.4, functional insulation) + safety factor

Creepage = f(working voltage, pollution degree, material group)^b (power-law interpolated between tabulated voltage bands) × (1 + FoS)

PD2, Group IIIb (100 ≤ CTI < 175)

Working voltage (300 V): base 3 mm, with margin = 3.6 mm. HV to chassis (150 V): base 1.573 mm, with margin = 1.888 mm

5. Paschen's Law cross-check

V_b = B·(p·d) / [ln(A·(p·d)) − ln(ln(1 + 1/γ))], A=113/(kPa·cm), B=2740 V/(kPa·cm), γ=0.01

p = 84.56 kPa at 5,000 ft, d = 0.24 mm → p·d = 2.029 kPa·cm

V_b = 1,424 V vs working voltage 300 V — consistent with the design

6. Rib / groove creepage reduction (IEC 60664-1)

Credit = widthOk ? 2·H : 0 (widthOk = W ≥ minimum-width(PD)); footprint = max(0, required creepage − credit)

H = 2 mm, W = 1.5 mm, minimum width at PD2 = 1 mm

Credit = 4 mm. Footprint (working voltage) = 0 mm, (HV to chassis) = 0 mm

Creepage & Clearance Distance Calculator