Clearance
Extract DIN VDE 0110-04.97*)
This standard is a technical adaptation of IEC Report 664/664A and specifies, in general, the minimum insulation distances for equipment. It can be used by committees to protect persons and property in the best possible way from the effects of electrical voltages or currents (e.g. fire hazard) or from functional failure of the equipment by providing adequate dimensioning of clearances and creepage distances in equipment.
*) It is the users responsibility to ensure that the complete current issue of the specification is considered.
Rated impulse without voltage
In allocation of the equipment to an installation category, the following factors shall be taken into account:
Overvoltages which can enter the equipment from outside across the terminals.
Overvoltages generated in the equipment itself and occurring at the terminals.
The following parameters apply to:
Installation category I
Equipment is intended for use only in appliances or installation parts, in which no overvoltages can occur.
Equipment in this installation category in normally operated at extra low voltage.
Installation category II
Equipment is intended for use in installations or parts of installations, in which lightning overvoltages need not be considered. Overvoltages caused by switching must be taken into account.
This includes for example domestic appliances.
Installation category III
Equipment is intended for use in installations or parts of installations, in which lightning overvoltages need not be considered, but which are subject to particular requirements with regard to the safety and availability of the equipment and its supply systems.
This includes equipment for fixed installation such as protective devices, relays, switches and sockets.
Installation category IV
Equipment is intended for use in installations or parts of installations, in which lightning overvoltages must be taken into account.
This includes equipment for connection to overhead lines such as omnidirectional control receivers and meters.
For circuits or parts of circuits inside the equipment, clearances may be dimensioned directly for the expected overvoltages. If the expected overvoltages are not impulse voltages but DC or AC voltages, the maximum value of these voltages shall be determined as the rated impulse withstand voltage for clearances both for homogeneous and inhomogeneous field.
Degree of pollution
Pollution degree 1: No pollution or only dry, non-conductive pollution occurs. The pollution has no influence.
Pollution degree 2: Only non-conductive pollution occurs. A temporary conductive caused by condensation must be expected occasionally.
The degrees of pollution 3 and 4 are in this case not considered, as they are not relevant for the connectors shown in this catalogue. The minimum creepages in table 00.04 refer to the CTI-value for insulation group III a/b.
Clearance
The clearance is defined as shortest distance through the air between two conductive elements.
|
|
Clearance |
|
To identify the clearance distance
Define the installation category
Define the degree of pollution expected
Select the rated impulse withstand voltage from table 00.01
Select the minimum required clearance from table 00.02
Exemplary calculation
What voltage can be used, if the clearance, the installation category and the degree of pollution are known:
|
Clearance |
Installation |
Degree of |
Voltage |
|
1.2 mm |
II |
2 |
150 V |
|
3.0 mm |
II |
2 |
600 V |
|
4.5 mm |
II |
2 |
600 V |
Creepage
The creepage is defined as shortest distance on the surface of an insulating material between two conductive elements.
|
|
Clearance |
|
To identify the creepage distance
Define the installation category
Define the degree of pollution expected
From the nominal voltage and the type of supply system select the rated voltage from table 00.03 a/b
From the rated voltage and degree of pollution select the minimum creepage required in table 00.04
For the dimensioning of the creepage distance the tracking formation of the insulating material has to be considered. If not indicated contrary, the CTI value of the insulating material is <400 and the isolation group is III a/b.
Exemplary calculation
What voltage can be used, if the creepage, the installation category and the degree of pollution are known:
|
Clearance |
Installation |
Degree of |
Voltage |
|
1.2 mm |
II |
2 |
50 V |
|
3.0 mm |
II |
2 |
220 V |
|
8.0 mm |
II |
2 |
600 V |
Table 00.01
|
Voltages phase-to-earth |
Rated impulse withstand voltages in kV for installation category |
|||
|
I |
II |
III |
IV | |
|
50 |
0.33 |
0.50 |
0.80 |
1.5 |
|
100 |
0.50 |
0.80 |
1.5 |
2.5 |
|
150 |
0.80 |
1.5 |
2.5 |
4.0 |
|
300 |
1.5 |
2.5 |
4.0 |
6.0 |
|
600 |
2.5 |
4.0 |
6.0 |
8.0 |
Table 00.02
|
Rated impulse |
Minimum clearances in mm up to 2000 m above sea level1) |
|||
|
Case A |
Case B |
|||
|
Pollution degree |
Pollution degree |
|||
|
1 |
2 |
1 |
2 | |
|
0.33 |
0.01 |
0.2 |
0.01 |
0.2 |
|
0,80 |
0,1 |
0,1 |
||
|
1.5 |
0.5 |
0.5 |
0.3 |
0.3 |
|
2.5 |
1.5 |
1.5 |
0.6 |
0.6 |
|
6.0 |
5.5 |
5.5 |
2 |
2 |
1) For higher altitudes see table 2b from
DIN VDE 0110 for multiplying factors.
2) Verification by an impulse voltage test is required if the clearance
is less than the value specified for case A.
3) Point to plane.
|
Table 00.03 a. Single phase, three or two wire AC or DC systems
|
Table 00.03 b. Three phase, four or three wire AC systems |
|
|
|
Table 00.04
|
Rated voltage |
12.5 |
25 |
32 |
50 |
63 |
80 |
100 |
125 |
160 |
200 |
250 |
320 |
400 |
500 |
630 |
800 |
1000 |
|
Minimum Degree of pollution 1 |
0.09 |
0.125 |
0.14 |
0.18 |
0.2 |
0.22 |
0.25 |
0.28 |
0.32 |
0.42 |
0.56 |
0.75 |
1 |
1.3 |
1.8 |
2.4 |
3.2 |
|
Degree of polution 2 |
0.42 |
0.5 |
0.53 |
1.2 |
1.25 |
1.3 |
1.4 |
1.5 |
1.6 |
2 |
2.5 |
3.2 |
4 |
5 |
6.3 |
8 |
10 |
