Working Voltage
(up to and including)

Nominal Ac Mains
Supply Voltage <150V
(Transient Rating for
Secondary Circuit 800 V)1

Nominal Ac Mains
Supply Voltage
>150V <300V
(Transient Rating for
Secondary Circuit1500 V)

Nominal Ac Mains
Supply Voltage
>300V <600V
(Transient Rating for Secondary Circuit 2500 V)1

Circuit Not Subjet to Transient Overvoltage

Voltage Peak or Dc

Voltage Rms
(Sinusoidal)

Pollution
Degrees 1 and 2

Pollution
Degree 3

Pollution
Degrees 1 and 2

Pollution
Degree 3

Pollution
Degrees 1, 2,
and 3

Pollution
Degrees 1 and 2 Only

V

V

F

B/S

R

F

B/S

R

F

B/S

R

F

B/S

R

F

B/S

R

F

B/S

R

71

50

0.4
(0.2)

0.7
(0.2)

1.4
(0.4)

1.0
(0.8)

1.3
(0.8)

2.5
(1.6)

0.7
(0.5)

1.0
(0.5)

2.0
(1.0)

1.0
(0.8)

1.3
(0.8)

2.5
(1.6)

1.7
(1.6)

2.0
(1.5)

4.0
(3.0)

0.4
(0.2)

0.4
(0.2)

0.8
(0.4)

140

100

0.8
(0.2)

0.7
(0.2)

1.4
(0.4)

1.0
(0.8)

1.3
(0.8)

2.6
(1.6)

0.7
(0.5)

1.0
(0.5)

2.0
(1.0)

1.0
(0.8)

1.3
(0.8)

2.6
(1.6)

1.7
(1.5)

2.0
(1.5)

4.0
(3.0)

0.6
(0.2)

0.7
(0.2)

1.4
(0.4)

210

150

0.6
(0.2)

0.9
(0.2)

1.8
(0.4)

1.0
(0.8)

1.3
(0.8)

2.8
(1.6)

0.7
(0.5)

1.0
(0.5)

2.0
(1.0)

1.0
(0.8)

1.3
(0.8)

2.6
(1.6)

1.7
(1.6)

2.0
(1.5)

4.0
(3.0)

0.6
(0.2)

0.7
(0.2)

1.4
(0.4)

280

200

F 1.1 (0.8) B/S 1.4 (0.8) R 2.8 (1.6)

1.7
(1.5)

2.0
(1.5)

4.0
(3.0)

1.1
(0.2)

1.1
(0.2)

2.2
(0.4)

420

300

F 1.6 (1.0) B/S 1.9 (1.0) R 3.8 (2.0)

1.7
(1.5)

2.0
(1.5)

4.0
(3.0)

1.4
(0.2)

1.4
(0.2)

2.8
(0.4)

700
840
1400

500
600
1000

F/B/S 2.5 R 5.0
F/B/S 3.2 R 5.0
F/B/S 4.2 R 5.0

2800
7000
9800
14,000
28,000
42,000

2000
5000
7000
10,000
20,000
30,000

F/B/S/R 8.4 See2
F/B/S/R 17.5 See2
F/B/S/R 25 See2
F/B/S/R 37 See2
F/B/S/R 80 See2
F/B/S/R 130 See2

1. Where transients in the equipment exceed this value, the appropriate higher clearance shall be used.
2. Compliance with a clearance value of 8.4 mm or greater is not required if the clearance path is:

  • entirely through air, or

  • wholly or partly along the surface of an insulating material of Material Group I; and the insulation involved passes an electric strength test according to 5.2.2 using:
    • an ac test voltage whose rms value is equal to 1.06 times the peak working voltage, or

    • a dc test voltage equal to the peak value of the ac test voltage prescribed above.

If the clearance path is partly along the surface of a material that is not Material Group I, the electric strength test is conducted across the air gap only.

Table III. Table 2K of the standard provides minimum clearances in secondary circuits (clearances in millimeters).