
A.24
A
Overview
HDC
Electrical data
Technical data
Insulating material
The insulating materials are subdivided
into four groups according to their CTI
(Comparative Tracking Index):
Insulating material
I
600 ≤ CTI
II
400 ≤ CTI < 600
III a
175 ≤ CTI < 400
III b
100 ≤ CTI < 175
The comparative tracking index must
be determined according to DIN IEC
112/VDE 0303 part 1 on the basis of
specially prepared samples with test
solution A.
Design of clearances and creepage distances in electrical equipment,
influencing factors:
Rated voltage
The rated voltage is derived from the nominal voltage of the power supply and the
corresponding network type.
For insulation
phase-to-phase 1)
phase-to-ground 1)
All systems
3-wire systems,
neutr. point grounding
VV
V
12.5
–
24 / 25
25
–
30
32
–
42 / 48 / 50**)
50
–
60
63
–
30-60
63
32
100**)
100
–
110 / 120
125
–
150**)
160
–
220
250
–
110-220
250
125
120-240
300**)
320
–
220-440
500
250
600**)
630
–
480-960
1000
500
1000**)
1000
–
Single-phase
2- or 3-wire AC or DC systems
Voltages for table 4
Rated voltage
of the power
supply (mains) *)
For insulation
phase-to-phase
phase-to-ground
All systems
3-phase
4-wire systems
3-wire systems
w th grounded
ungrounded1) or.
neutral wire2)
phase-grounded
VV
V
60
63
32
63
110/120/127
125
80
125
150**)
160
–
160
208
200
125
200
220/230/240
250
160
250
300**)
320
–
320
380/400/415
400
250
400
440
500
250
500
480/500
500
320
500
575
630
400
630
600**)
630
–
630
660/690
630
400
630
720/830
800
500
800
960
1000
630
1000
1000**)
1000
–
1000
1) Phase-to-ground insulation levels for ungrounded or impedance-
grounded systems are equal to those of phase-to-phase because the
operating voltage to ground of any phase can, in practice, reach full
phase-to-phase voltage. This is because the actual voltage to ground
is determined by the insulation resistance and capacitive reactance of
each phase to ground; thus, a low (but acceptable) insulation resistance
of one phase can ground it and raise the other two to full phase-to-
phase voltage to ground.
2) For electrical equipment for use in both 3-phase 4-wire and 3-phase
3-wire supp ies, grounded and ungrounded, use the values for 3-wire
systems only.
) It is assumed that the rated voltage of the electrical equipment is not
lower than the nominal voltage of the power supply.
**) Because of the common changes, the meaning of the ** symbol has
not been used in table 1; i.e. the / symbol indicates a 4-wire 3-phase
distribution system. The lower value is the phase-to-neutral voltage,
while the higher value is the phase-to-phase voltage. Where only one
value is indicated, it refers to 3-wire 3-phase systems and specifies
the value phase-to-phase.
The values given in table 1 are still taken into account in tables 3a
and 3b by the ** symbol.
3-phase
3- or 4-wire AC systems
Voltages for table 4
Rated voltage
of the power
supply (mains) )