Pollution Degree:
ductive due to condensation. This is to be
expected.
Any addition of foreign matter, solid, liquid or gaseous
(ionized gases), that may produce a reduction of insulation capabilities, is considered pollution. The pollution
degree affects the creepage and clearance values. The
degree of pollution is broken down as follows:
Level 1: No pollution or only dry non-conduc
tive pollution occurs.
Level 2: Normally only non-conductive pollu
tion occurs. Temporary conductivity caused by
condensation is to be expected.
Level 3: Conductive pollution occurs, or dry
non-conductive pollution, which becomes con-
Level 4: The pollution generates persistent
conductivity caused by conductive dust, rain or
snow.
The IEC 61010 Standard includes tables that tie the
above criteria together. This allows one to design,
test, and classify hand-held probe assemblies pertinent
to the application. Two such excerpts from tables
appear below. They have been included to illustrate
how a probe can satisfy two separate classifications.
(i.e.- a 600V, CAT III and a 1000V, CAT II can be equally
satisfied with a single design.)
DOUBLE INSULATION
Working
Voltage (r.m.s. or d.c.)
up to
V
300
600
1000
Pollution Degree 2
Installation Category (overvoltage category) II
Clearance
mm
3.3
6.5
11.5
Test Voltage, V
Creepage Distance, mm
For Use In Equipment
Material Group
I
CTI>600
II
CTI>400
II
CTI>100
3.3
6.5
11.5
4.2
8.5
14.0
6.0
12.0
20.0
Peak Impulse
1,2/50 µs
r.m.s.
50/60 Hz
1 min
d.c. or
50/60 Hz peak
1 min
4250
6800
10200
2300
3700
5550
3250
5250
1000
DOUBLE INSULATION
Working
Voltage (r.m.s. or d.c.)
up to
V
300
600
1000
Pollution Degree 2
Installation Category (overvoltage category) III
Clearance
mm
6.5
11.5
16.0
Test Voltage, V
Creepage Distance, mm
For Use In Equipment
Material Group
I
CTI>600
II
CTI>400
II
CTI>100
6.5
11.5
16.0
6.5
11.5
16.0
6.0
11.5
20.0
Peak Impulse
1,2/50 µs
r.m.s.
50/60 Hz
1 min
d.c. or
50/60 Hz peak
1 min
6800
10200
13600
2700
5550
7400
3250
7850
10450
References:
http://www.technology.niagarac.on.ca/courses/elnc236/dmmsafet/tsld009.htm
IEC 61010 Standard
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