SAUDI ARABIAN STANDARD SA SO IEC 60669-2-4/2007
 
 
 
 
 
 
 
  
 
SAUDI STANDARD 
NO.  SASO IEC 60669-2-4:  2007  
 
 
SWITCHES FOR HOUSEHOLD AND SIMILAR  
FIXED ELECTRICAL INSTALLATIONS – 
 
Part 2-4: Particular requirements –  
Isolating switches 
  
 
         
SAUDI ARABIAN STANDARDS ORGANIZATION 
THIS DOCUMENT IS A DRAFT SAUDI STANDARD CIRCULATED FOR COMMENTS.  IT IS, THEREFORE, SUBJECT TO CHANGE AND MAY NOT BE REFERRED TO AS A SAUDI STANDARD UNTIL APPROVED BY THE BOARD OF DIRECTORS.  SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
1 
  
CONTENTS  
FOREWORD....................................................................................................................... .. 3 
 1 Scope ....................................................................................................................... ..... 4 
2 Normative references ..................................................................................................... 4 
3 Definitions ................................................................................................................. ..... 4 
4 General requirements ..................................................................................................... 5 
5 General notes on tests .................................................................................................... 5 
6 Ratings ..................................................................................................................... ..... 5 
7 Classification .............................................................................................................. .... 6 
8 Mark ing ..................................................................................................................... ..... 6 
9 Checking of dimensions .................................................................................................. 7 
10 Protection against electric shock ..................................................................................... 7 
11 Provision for earthing......................................................................................................  7 
12 Terminals .................................................................................................................. ..... 7 
13 Constructional requirements ......................................................................................... 11 14 Mechanism .................................................................................................................. . 12 
15 Resistance to ageing, protection provided by enclosures of switches and 
resistance to humidity ................................................................................................... 13 
16 Insulation resistance and electric strength ..................................................................... 13 17 Temperature rise .......................................................................................................... 14 
18 Making and breaking capacity ....................................................................................... 15 19 Normal operation .......................................................................................................... 19 
20 Mechanical strength ..................................................................................................... 19  
21 Resistance to heat ........................................................................................................ 19 
22 Screws, current-carrying parts and connections............................................................. 20 
23 Creepage distances, clea rances and distances thr ough sealing compound .................... 20 
24 Resistance of insulating material to a bnormal heat, to fire and to tracking ...................... 20 
25 Resistance to rusting .................................................................................................... 2 0 
26 EMC requirements ........................................................................................................ 20  
 Annex A (normative) Survey of specimens needed for tests ................................................. 28 
Annex B (normative)  Additional requiremen ts for switches havin g facilities for the 
outlet and retention of flexible cables .................................................................................. 29 
Annex AA (informative)  Determination of short-circuit power factor ..................................... 30 
Annex BB (informative)  SCPDs for short-circuit tests .......................................................... 32 
 Bibliography .................................................................................................................. ..... 33 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
2 
 Figure 101 – Test circuit for verification of t he short circuit withstand capability  with a 
SCPD of one-pole isolating  switch ....................................................................................... 22 
Figure 102 – Test circuit for verification of t he short circuit withstand capability  with a 
SCPD of a two-pole isolating  switch .................................................................................... 23 
Figure 103 – Test circuit for verification of the short circuit withstand capability with a 
SCPD of a three-pole isolating  switch .................................................................................. 24 
Figure 104 – Test circuit for verification of t he short circuit withstand capability  with a 
SCPD of a four-pole isolating  switch .................................................................................... 25 
Figure 105 – Test apparatus for verification of the minimum I2t and Ip values  to be 
withstood by the isolating  switch ......................................................................................... 26 
 
Table 2 – Relationship between rated currents and connectable cross-sectional areas 
of copper conductors for screw-type terminals ....................................................................... 7 
Table 3 – Tightening torque for verification of the mechanical strength  of screw-type 
terminals ..................................................................................................................... ......... 8 
Table 4 – Test values for flexion and pull out for copper conductors ....................................... 9 
Table 5 – Test values for pulling out test ............................................................................... 9 
Table 6 – Composition of conductors ................................................................................... 10 
Table 7 – Relationship between rated currents and connectable cross-sectional areas 
of copper conductors for screwless term inals ...................................................................... 10 
Table 8 – Test current for the verification of electrical and thermal stresses in normal 
use of screwless terminals .................................................................................................. 1 0 
Table 9 – Cross-sectional areas of rigid copper conductors  for deflection test of 
screwless terminals ........................................................................................................... . 11 
Table 10 – Deflection test forces ......................................................................................... 11 Table 12 – External cabl e diameter limits for surface type switches...................................... 12 
Table 101 – Test voltage across the open contacts for verifying the suitability  for 
isolation, referred to the rated voltage of the isolating switch and  to the altitude where 
the test is carried out ....................................................................................................... ... 14 
Table 15 – Temperature-rise test currents and cross-sectional areas of copper 
conductors .......................................................................................................................... 14 
Table 102 – Minimum values of I2t and Ip ........................................................................... 16 
Table 103 – Power factors for short-circuit tests .................................................................. 17 Table 17 – Number of operations for normal operation test .................................................. 19 
Table BB.1 – Indication of silver wire diameters as a function of rated currents  and 
short-circuit currents ........................................................................................................ ... 32 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
3 
  
 
FOREWORD 
 
The Saudi Standards,Metrology  and Qualit y Organization (SASO) has adopted the 
International Standard IEC 60669-2- 4/2004 “SWITCHES FOR HOUSEHOLD AND 
SIMILAR FIXED ELECTRICAL INSTALLATIONS –  Part 2-4: Particular 
equirements – Isolating switches ” issued  by the International Electrotechnical 
Commission (IEC). It has been adopted wi thout any technical m odifications with a 
view to its approval as a Saudi standard. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
4 
  
SWITCHES FOR HOUSEHOLD AND SIMILAR  
FIXED ELECTRICAL INSTALLATIONS –  
 
Part 2-4: Particular requirements –  
Isolating switches 
  
1 Scope 
This clause of Part 1 applies except as follows. 
Replacement of the first paragraph: 
This part of IEC 60669 applies to manually operated general purpose isolating switches with a 
rated voltage not exceeding 440 V and a rated current not exceeding 125 A, intended for 
household and similar fixed electrical installations, either indoors or outdoors. 
NOTE Isolating switches are designed for overvoltage ca tegory III and used in environment of pollution degree 2 
according to IEC 60664-1. 
2 Normative references 
This clause of Part 1 applies except as follows. 
Addition: 
IEC 61180-1:1992, High-voltage test techniques for low voltage equipment – Part 1: 
Definitions, test and procedure requirements   
3 Definitions 
This clause of Part 1 applies except as follows. 
Additional definitions: 3.101 
isolating switch  
switch designed to provide isolation of the insta llation or part of the installation and equipment 
from the supply and to carry and to make and break the current in all line current carrying 
poles 
3.102 
conditional short-circuit current  
I
nc 
value of the a.c. component of a prospective current, which a switch without integral short-
circuit protection, but protected by a suitable short-circuit protective device (hereinafter referred to as SCPD) in series, can withstand under specified conditions of use and behaviour SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
5 
 3.103      I2t  
integral of the square of the current over a given time interval ( t0, t1) 
∫=1
02 2t
tt i tI d 
4 General requirements 
This clause of Part 1 applies. 
5 General notes on tests 
This clause of Part 1 applies except as follows. 
5.4 Addition: 
For the test of 18.101 three additional specimens are used.  
6 Ratings 
This clause of Part 1 applies except as follows. 6.2  Modification:  
In the first paragraph , delete the values "6 A" and "10 A" and add the values  “80 A, 100 A and 
125 A.” 
Additional note:  
NOTE 101 In the following countries the value 13 A is  considered as a preferred value: DK and UK. 
NOTE 102  In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
In the UNITED KINGDOM, this clause in Part 1 applies. 
 
Additional subclause: 
6.101 Standard and preferred values of the conditional short-circuit current ( Inc) 
NOTE The associated power-factors  are specified in Table 103. 
6.101.1 Values up to and including 10 000 A 
The standard values of the conditional short-circuit current ( Inc) are: 
1 500 A, 3 000 A, 4 500 A, 6 000 A and 10 000 A. 
6.101.2 Values above 10 000 A 
The preferred values are:  
15 000 A, 20 000 A and 25 000 A. Values above 25 000 A are not considered by this standard. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
6 
 7 Classification 
This clause of Part 1 applies except as follows. 
7.1.1  Addition:  
Isolating switches shall be only of pattern numbers 1, 2, 3 or 03. 
7.1.2  This subclause of Part 1 is not applicable. 
7.1.6  Addition:  
– rail type 
7.2 Replacement in Table 1, first column, last line, of the values  “16, 20, 25, 32, 40, and 63” 
by “equal and above 16”.  
8 Marking 
This clause of Part 1 applies except as follows. 
8.1 Addition: 
– symbols for open position (OFF) and closed position (ON), 
– symbol for isolating function,  – rated conditional short-circuit current  ( I
nc). 
The manufacturer shall provide reference(s) of one or more short circuit protection devices 
(SCPDs) in his catalogue and/or in the instructions which are provided with the isolating 
switch. 
8.2 Addition:  
– isolating function ............................................................................................... 
– rated conditional short-ci rcuit current  ...............................................................
 Inc 
8.3 Addition  
Isolating switches shall be marked with the symbols for isolating function and for the closed 
and open position. These markings shall be visible from the front after installation, even after 
removal of the front cover of the enclosure when the isolating switch is mounted and wired as 
in normal use. The isolating symbol may be included in a wiring diagram even combined with symbols of other functions, provided that it is visible from the front under the conditions 
specified before. 
The marking for the rated conditional short-circuit current ( I
nc) shall be on the isolating switch 
or in the manufacturer's published literature. 
8.6 Replacement of the first sentence of the first paragraph 
Isolating switches shall be so marked that the actual contact position is clearly indicated. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
7 
 Deletion of Note 1 . SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
8 
 9 Checking of dimensions 
This clause of Part 1 applies. 
10 Protection against electric shock 
This clause of Part 1 applies except as follows. 
10.3  Replacement of the first two lines:  
Accessible parts of isolating switches shall be made of insulating material, with the exception 
of the following: 
11 Provision for earthing 
This clause of Part 1 applies. 
12 Terminals 
This clause of Part 1 applies except as follows.  
Replacement of Table 2: 
Table 2 – Relationship between rated currents and connectable cross-sectional areas 
of copper conductors for screw-type terminals   
Ranges of rated currents Rigid conductors (solid or stranded)a 
A Nominal cross-sectional areas 
mm2 Diameter of largest conductor 
mm 
16b 
Above 16 up to and including 25 
Above 25 up to and including 32 
Above 32 up to and including 50 Above 50 up to and including 80  
Above 80 up to and including 100 
Above 100 up to and including 125 From   1,5   up to   4 inclusive 
From   2,5   up to   6 inclusive 
From   4      up to 10 inclusive 
From   6      up to 16 inclusive From 10      up to 25 inclusive  
From 16      up to 35 inclusive 
From 25      up to 50 inclusive 2,72 
3,34 
4,34 
5,46 6,85 
7,90 
9,10 
a  The use of flexible conductors is permitted. 
b  Each supply terminal of isolating switches, other  than those of pattern numbers 3 and 03, shall allow the 
connection of two 2,5 mm2 conductors. For isolating switches having a rated voltage not exceeding 250 V a 
round hole is sufficient for the connection of two 2,5 mm2 conductors. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
In the UNITED KINGDOM, Table 2 of Part 1 applies.  SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
9 
 12.2.5  Replacement of Table 3:  
Table 3 – Tightening torque for verification of the mechanical strength  
of screw-type terminals  
Nominal diameter of thread 
mm Torque 
Nm 
1 2 3 4 5 
Up to and including 1,6 
Above 1,6 up to and including 2,0 
Above 2,0 up to and including 2,8 Above 2,8 up to and including 3,0 
Above 3,0 up to and including 3,2 
Above 3,2 up to and including 3,6 Above 3,6 up to and including 4,1 
Above 4,1 up to and including 4,7 
Above 4,7 up to and including 5,3 Above 5,3 up to and including 6,0 
Above 6,0 up to and including 8,0 
Above 8,0 up to and including 10,0 Above 10,0 up to and including 12,0 
Above 12,0 up to and including 15,0 0,05 
0,1 
0,2 
0,25 
0,3 
0,4 0,7 
0,8 
0,8 1,2 
2,5 
– – 
– – 
– 
– – 
– 
– 
1,2 
1,2 
1,4 1,8 
2,5 
3,5 4,0 
5,0 0,1 
0,2 
0,4 0,5 
0,6 
0,8 1,2 
1,8 
2,0 2,5 
3,5 
4,0 
– 
– 0,1 
0,2 
0,4 0,5 
0,6 
0,8 1,2 
1,8 
2,0 3,0 
6,0 
10,0 
– 
– – 
– 
– – 
– 
– 
1,2 
1,8 
2,0 3,0 
4,0 
6,0 8,0 
10,0 
NOTE 1 Column 1 applies to screws without heads if the screw when tightened does not protrude from the hole, 
and to other screws which cannot be tightened by means of  a screwdriver with a blade wider than the diameter of 
the screw. 
Column 2 applies to nuts of mantle terminals which are tightened by means of a screwdriver. 
Column 3 applies to other screws  which are tightened by means of a screwdriver. 
Column 4 applies to nuts of mantle terminals in which the nut is tightened by means other than a screwdriver. 
Column 5 applies to screws or nuts, other than nuts of mantle terminals, which are tightened by means other than 
a screwdriver. 
Where a screw has a hexagonal head with a slot for tighteni ng with a screwdriver and the values of columns 3 
and 5 are different, the test is made twice, first applying to the hexagonal head the torque specified in column 5 and then applying the torque specified in column 3 by me ans of a screwdriver. If the values of columns 3 and 5 
are the same, only the test with the screwdriver is made. 
NOTE 2 For mantle terminals the specified nominal diameter is that of the slotted stud. NOTE 3 The shape of the blade of the test screwdriver should suit the head of the screw to be tested. 
NOTE 4 The screws and nuts should not be tightened in jerks. 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
10 
 Replacement of Table 4: 
Table 4 – Test values for flexion and pull-out for copper conductors  
Conductor  
cross-sectional area a 
mm2  Diameter 
of bushing hole  b 
mm  Height H c 
mm Mass 
for conductor 
kg 
1,5 6,5 260 0,4 
2,5 9,5 280 0,7 
4,0 9,5 280 0,9 
6,0 9,5 280 1,4 
10,0 9,5 280 2,0 
16,0 13,0 300 2,9 
25,0 13,0 300 4,5 
35 14,5 320 6,8 
50 16 340 9,5 
a AWG sizes corresponding to mm2 can be found in IEC 60999. 
b  If the bushing hole diameter is not large enough to accommodate the conductor without binding, a bushing 
having the next larger hole size may be used. 
c  Tolerance for height H = ±15 mm. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
In the UNITED KINGDOM, Table 4 of Part 1 applies. 
 
12.2.6  Replacement of Table 5: 
Table 5 – Test values for pulling out test 
Cross-
sectional 
area of 
conductors  
accepted by 
the terminal 
mm2 From 1,5 
up to 2,5 
inclusive From 2,5 
up to 4 
inclusive From 4 
up to 6 
inclusive From 6 
up to 10 
inclusive From 10 
up to 16 
inclusive From 16 
up to 25 
inclusive From 25 
up to 35 
inclusive From 35 
up to 50 
inclusive 
Pull 
N 50 50 60 80 90 100 190 235 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
In the UNITED KINGDOM, Table 5 of Part 1 applies. 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
11 
 12.2.7  Replacement of Table 6:  
Table 6 – Composition of conductors   
Cross-sectional area 
mm 2 Number of wires and nominal diameter of wires 
mm 
Solid conductor Stranded conductor 
1,5 
2,5 
4 6 
10 
16 25 
35 
50 1 × 1,38 
1 × 1,78 
1 × 2,25 
1 × 2,76 
1 × 3,57 
– – 
– 
– 7 × 0,52 
7 × 0,67 
7 × 0,86 
7 × 1,05 
7 × 1,35 
7 × 1,70 
7 × 2,14 
7 × 2,53 
19 × 1,83 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
In the UNITED KINGDOM, Table 6 of Part 1 applies.  
12.3.2  Replacement of Table 7: 
Table 7 – Relationship between rated currents and connectable cross-sectional areas 
of copper conductors for screwless terminals  
 Conductors 
Rated current 
 
A Nominal cross-
sectional areas 
mm2 Diameter of largest 
rigid conductor 
mm Diameter of largest 
flexible conductor 
mm 
16a 1,5 to 2,5 2,13 2,21 
a Each supply terminal of isolating switches other than those of pattern numbers 3 and 03 shall allow the 
connection of two 2,5 mm2 conductors. In such cases a terminal with separate independent clamping 
means for each conductor shall be used. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
In the UNITED KINGDOM, Table 7 of Part 1 applies.  
12.3.11  Replacement of Table 8:  
Table 8 – Test current for the verification of electrical and thermal stresses 
in normal use of screwless terminals  
Rated current 
 
A Test current 
 
A Cross-sectional area 
of the conductor 
mm2 
16 22 2,5 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
In the UNITED KINGDOM, Table 8 of Part 1 applies. 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
12 
 12.3.12  Replacement of Tables 9 and 10: 
Table 9 – Cross-sectional areas of rigid copper conductors  
for deflection test of screwless terminals   
Rated current of the isolating 
switch Cross-sectional area of the test conductor 
mm2 
A 1st test sequence 2nd test sequence 
16 1,5 2,5 
 
Table 10 – Deflection test forces  
Cross-sectional area of the test conductor 
mm2 Force for deflecting the test conductora 
N 
1,5 
2,5 0,5 
1,0 
a The forces are chosen so that they stress t he conductors close to th e limit of elasticity. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
 In the UNITED KINGDOM, Tables 9 and 10 of Part 1 apply. 
 
13 Constructional requirements 
This clause of Part 1 applies except as follows. 
Additional subclause: 
13.2.101  Isolating switches when in the open position shall provide an isolation distance in 
accordance with the requirements necessary to satisfy the isolating function. 
Indication of the contact position shall be prov ided by the position of the actuating member 
and/or by suitable means.  
NOTE A pilot light alone is not considered as suitable means. 
The actuating member shall be connected to the moving contacts in a reliable way. The 
actuating member shall not indicate the open position unless all the moving contacts are in 
the open position.  
Isolating switches shall be so designed that the actuating member can only be fitted in a 
manner which ensures correct contact position and correct locking, if the isolating switch is 
provided with means for locking. When means are provided or specified by the manufacturer 
to lock the isolating switch in the open position, locking in that position shall only be possible when the contacts are in the open position. 
Compliance is checked by inspection and by the tests of clause 16.101. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
13 
 13.12  Replacement of Table 12: 
Table 12 – External cable diameter limits for surface type switches 
Rated 
current 
A Cross-sectional 
areas 
mm2 Number 
of conductors Limits of external diameter 
of cables 
Minimum 
mm Maximum 
mm 
16 1,5 up to and including 4 2 
7,6 15 
3 16 
4 18 
5 19,5 
20 
25 2,5 up to and including 6 2 
8,6 18,5 
3 20 
4 22 
5 24,5 
32 4 up to and including 10 2 
9,6 24 
3 25,5 
4 28 
5 30,5 
40 
45 50 6 up to and including 16 2 
10,5 27,5 
3 29,5 
4 32 
5 35,5 
63 10 up to and including 25 2 
13 31,5 
3 34 
4 37,5 
5 41,5 
80 
100 16 up to and including 35 2 
15,5 — 
3 38,0 
4 42,0 
5 — 
125 25 up to and including 50 2 
18,5 — 
3 44,0 
4 48,5 
5 — 
NOTE The limits of external diameter of cables spec ified in this table are based on type 60227 IEC 10 according 
to IEC 60227-4 and type 60245 IEC 66 according to IEC 60245-4 and are given for information. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
In the UNITED KINGDOM, Table 12 of Part 1 applies.  
14 Mechanism 
This clause of Part 1 applies. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
14 
 15 Resistance to ageing, protection provided by enclosures of switches and 
resistance to humidity 
This clause of Part 1 applies. 
16 Insulation resistance and electric strength 
This clause of Part 1 applies except as follows. 
Additional subclause: 
16.101  Isolating switches shall be suitable for is olation. They shall be tested in the new, 
clean and dry conditions, when in the open position, across the terminals of each pole. 
Compliance is checked by the following test. The 1,2/50 impulse voltage according to Figure 1 of IEC 61180-1 is applied between the line 
terminals connected together and the load terminals connected together with the contacts in 
the open position.  
The impulses are given by a generator producing positive and negative impulses having a 
front time of 1,2 µs and a time to half value of 50 µs, the tolerances being 
± 5 % for the peak value; 
± 30 % for the front time; ± 20 % for the time to half value. 
The shape of the impulses is adjusted with the isolating switch under test connected to the 
impulse generator. For this purpose appropriate voltage dividers and voltage sensors shall be 
used. 
Small oscillations in the impulses are allowed, provided that their amplitude near the peak of 
the impulse is less than 5 % of the peak value. 
For oscillations on the first half of the front, amplitudes up to 10 % of the peak value are 
allowed. 
The test voltage shall be chosen from Table 101, in accordance with the rated voltage of the 
isolating switch. 
The impulse voltage shall be applied 3 times at intervals of 1 s minimum. 
There shall be no discharges during the test. 
NOTE 1 The surge impedance of the test apparatus should be 500 Ω; a substantial reduction of this value is 
under consideration. 
NOTE 2 The expression “discharge“ is  used to cover the phenomena associated with the failure of insulation 
under electric stress, which includes current flow and a drop in voltage. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
15 
 Table 101 – Test voltage across the open contacts for verifying the suitability  
for isolation, referred to the rated voltage of the isolating switch and  
to the altitude where the test is carried out  
Rated voltage Test voltage [kV] and corresponding altitudes above sea level [m] 
V Sea level 200 500 1 000 2 000 
Not exceeding 
130 V 3,5 3,5 3,4 3,2 3 
Exceeding 
130 V 6,2 6 5,8 5,6 5 
 
17 Temperature rise 
This clause of Part 1 applies except as follows. 
Replacement of Table 15: 
Table 15 – Temperature-rise test currents and cross-sectional areas 
of copper conductors 
 
Rated current 
A  
Test current  
A Nominal cross-sectional 
area of conductors  
mm2 
16 
20 25 32 40 45 50 63 80 
100 125 20 
25 32 38 46 51 
57,5 
75 90 
115 145      4
a 
  4   6 
10 16 16 16 25 25 35 50 
a For isolating switches having a rated voltage not exceeding 250 V, other than those of 
pattern number 3 and 03 the test shall be carried out with conductors having a  
cross-sectional area of 2,5 mm2. 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
In the UNITED KINGDOM, Table 15 of Part 1 applies.  
Replacement of the penultimate paragraph before Note 5: 
The temperature rise test of the terminals shall not exceed 45 K for isolating switches having 
rated current up to and including 63 A, 65 K for isolating switches having rated current greater than 63 A. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
16 
 18 Making and breaking capacity 
This clause of Part 1 applies except as follows. 
Additional subclause: 
18.101 Short-circuit withstand capability tests 
Six new specimens are used for this test. 
The test is intended to verify that the isolat ing switch is able to withstand, without damage, 
short-circuit currents up to and including its rated conditional short-circuit current. 
18.101.1 General conditions for test 
The conditions of 18.101 are applicable to any test intended to verify the behaviour of the 
isolating switches under short-circuit conditions. 
a) Test circuit 
 Figures 101, 102, 103 and 104 respectively give diagrams of the circuits to be used for the 
tests concerning: 
– a single pole isolating switch; – a two-pole isolating switch; – a three-pole isolating switch; – a four-pole isolating switch. 
 The supply S feeds a circuit including resistors R, reactors L, the short circuit protection 
device SCPD and the isolating switch under test D. 
 The values of the resistors and reactors of the test circuit shall be adjusted to satisfy the 
specified test conditions. 
 The reactors L shall be air-cored. They shall always be connected in series with the 
resistors R, and their value shall be obtained by connecting individual reactors in series; parallel connecting of reactors is allowed when these reactors have practically the same 
time-constant. 
 Since the transient recovery voltage characteristics of test circuits including large air-
cored reactors are not representative of normal service conditions, the air-cored reactor in any phase shall be shunted by a resistor taking approximately 1  % of the current through 
the reactor, unless otherwise agreed between manufacturer and user. 
 In each test circuit the resistors R and the reactors L are inserted between the supply 
source S and the isolating switch D. 
 The SCPD is inserted between the resistor R and the isolating switch D.  For the tests of 18.101.2 the isolating switch D shall be connected with cables having a 
length of 0,75 m per pole and the maximum cross-sectional area corresponding to the 
rated current according to Table 2. 
NOTE It is recommended to connect 0,5 m on the supply  side and 0,25 m on the load side of the isolating 
switch. 
 The diagram of the test circuit shall be given in the test report. It shall be in accordance 
with the relevant figure. 
 There shall be one and only one point of the test circuit which is directly earthed; this shall 
be the neutral point of the supply.  SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
17 
  The SCPD may be a circuit-breaker, or a fuse, having an I2t and peak current Ip not 
exceeding the I2t and peak current Ip withstand capabilities stated by the manufacturer for 
the isolating switch D. 
 For the purpose of verifying the minimum I2t and Ip values to be withstood by the isolating 
switch, as given in Table 102, tests have to be performed. The SCPD shall be adjusted 
and shall be embodied either by a silver wire using the test apparatus shown in Figure 105 or by a fuse (as proposed in Annex BB) or by any other means. 
 For the purpose of this test, verification of the correctly selected and adjusted SCPD (I
2t 
and Ip) is made prior to testing, the isolating  switch being replaced by a temporary 
connection having a negligible impedance.  
 The minimum values of let-through energy I2t and peak current based on an electrical 
angle of 45°, are given in Table 102. 
 Unless otherwise specified by the manufacturer, these values shall not be higher than 
1,1 times the values given in Table 102. 
Table 102 – Minimum values of I2t and Ip 
Inc Ip / I2t  In = 16 A 16 A < In ≤ 32 A 32 A < In ≤ 40 A 40 A < In ≤ 63 A 63 A < In ≤ 80 A 80 A < In ≤ 125 A 
1 500 Ip (kA) 1,02 1,50 1,90 2,10 - - 
I2t (kA2s) 1,00 4,10 9,75 22,00 - - 
3 000 Ip (kA) 1,10 1,85 2,35 3,30 3,70 3,95 
 I2t (k A2s) 1,20 4,50 8,70 22,50 36,00 72,50 
4 500 Ip (kA) 1,15 2,05 2,70 3,90 4,80 5,60 
 I2t (k A2s) 1,45 5,00 9,70 28,00 40,00 82,00 
>6 000 Ip (kA) 1,30 2,30 3,00 4,05 5,10 5,80 
 I2t (k A2s) 1,60 6,00 11,50 25,00 47,00 65,00 
 
NOTE  1 At the request of the manufacturer higher values of I2t and Ip may be used. 
NOTE 2  In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
For current rating less than 16 A, the column for 16 A rating applies. 
 
 For intermediate values of short-circuit test currents the next higher short-circuit current 
shall apply.  
 The verification of the minimum I2t and Ip values is not needed if the manufacturer has 
stated for the isolating switches values higher than the minimum ones, in which case the 
stated values shall be verified. 
 For co-ordination with circuit-breakers, tests with this combination are necessary. 
 All the conductive parts of the isolating switch D normally earthed in service, including the 
metal support on which the isolating switch is mounted or any metal enclosure (see 
18.101.1 f), shall be connected to the neutral point of the supply or to a substantially non-
inductive artificial neutral permitting a prospective fault current of at least 100 A.  
 This connection shall include a copper wire F of 0,1 mm diameter and not less than 50 mm 
in length for the detection of the faul t current and, if necessary, a resistor R1 limiting the 
value of the prospective fault current of approximately 100 A.  
 The current sensors O1 are connected on the load side of the isolating switch D.  
 The voltage sensors O2 are connected across the supply terminals. 
 Resistors R2 drawing a current of 10 A per phase are connected on the supply side of the 
isolating switch D between the reactor for adjusting the prospective current to the rated 
conditional short-circuit current of the isolating switch and the isolating switch D. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
18 
  Unless otherwise stated in the test report, the resistance of the measuring circuits shall be 
at least 100 ohm per volt of the power frequency recovery voltage.  
b) Tolerances for test quantities 
 The verification tests for the conditional short-circuit withstand capability shall be 
performed at values of influencing quantities and factors as stated by the manufacturer in 
accordance with Clause 5, unless otherwise specified. 
 The tests are considered as valid if the values as recorded in the test report are within the 
following tolerances for the specified values: 
– current: (05+) %; 
– rated frequency: ± 5  %;  
– voltage: ± 5  % (including recovery voltage). 
c) Power factor of the test circuit 
 The power factor of each phase of the test circuit shall be determined according to a 
recognised method which shall be stated in the test report. 
 Two examples are given in Annex C.   The power factor of a polyphase circuit is considered as the mean value of the power 
factor of each phase.  
 The power factor shall be in accordance with Table 103. 
Table 103 – Power factors for short-circuit tests  
Short circuit current 
A Power factor  
Ic = 1 500 0,95 to 0,98 
 1 500 < Ic ≤ 3 000 0,85 to 0,90 
3 000 < Ic ≤ 4 500 0,75 to 0,80  
4 500 < Ic ≤ 6 000  0,65 to 0,70  
6 000 < Ic ≤ 10 000 0,45 to 0,50 
10 000 < Ic ≤ 25 000 0,20 to 0,25  
 
d) Power frequency recovery voltage 
 The value of the power frequency recovery voltage shall be equal to a value 
corresponding to 105 % of the rated voltage of the isolating switch D. 
NOTE 2 The value of 105 % of the rated voltage is deemed to cover the effects of the variations of the 
system voltage under normal service conditions. The upper limit value may be increased with the approval of the manufacturer. 
e) Calibration of the test circuit 
 The isolating switch D and the SCPD are replaced by temporary connections G1 having 
negligible impedance compared with that of the test circuit. 
 For the test of 18.101.2 the load terminals of the isolating switch D being short-circuited 
by means of the connections of negligible impedance, the resistors R and the reactors L are adjusted so as to obtain, at the test voltage, a current equal to the rated conditional 
short-circuit current at the prescribed power-factor; the test circuit is energised 
simultaneously in all poles and the current curve is recorded with the current sensor O
1. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
19 
 f) Condition of the isolating switch for test 
 The isolating switch D shall be mounted on a metal support in free air, unless it is 
intended for installation in an individual metal enclosure specified by the manufacturer, in which case it shall be tested in the smallest of such individual enclosures.  
 Its control mechanism shall be operated simulating as closely as possible the normal 
manual operation.  
 It shall be verified that the isolating switch D operates correctly on no-load when it is 
operated under the specified conditions. 
g) Sequence of operations 
 The test procedure consists of a sequence of operations. The following symbols are used 
for defining the sequence of operations: 
O represents an automatic opening operation of the SCPD, the short-circuit being 
established by the closing device T, with the isolating switch under test (D) and the SCPD in the closed position; 
CO represents a closing operation of the isolating switch under test (D), both the closing 
device T and the SCPD being in the closed position, followed by an automatic 
operation of the SCPD. 
t represents the time interval between two successive short-circuit operations, which 
shall be at least 3 min. 
h) Behaviour of the isolating switch during tests  During tests, the isolating switch D shall not endanger the operator. 
 Furthermore, there shall be no permanent arcing, no flashover between poles or between 
poles and exposed conductive parts, no melting of the fuse F. 
i) Condition of the isolating switch after tests  After the test carried out in accordance with 18.101.2 the isolating switch D shall show no 
damage impairing its further use and shall be capable, without maintenance, of 
– complying with the requirements of 16.2 without previous humidity treatment, 
the test voltage of 4 000 V being reduced by 1 000 V, and the other test 
voltages by 500 V; 
– switching on and off its rated current at its rated voltage once only. 
18.101.2 Verification of the co-ordination between the isolating switch and the SCPD 
These tests are intended to verify that the isolating switch D, protected by the SCPD, is able 
to withstand, without damage, short-circuit curre nts up to and including its rated conditional 
short-circuit current (see 6.101). 
The short-circuit current is interrupted by the SCPD. 
The SCPD is renewed or reset as applicable, after each operation. The following test is made under the general cond itions of 18.101.1, to check that at the rated 
conditional short-circuit current I
nc the SCPD protects the isolating switch.  
For the breaking operations (sequence O), the closing device T is synchronised with respect 
to the voltage wave so that a point of initiation is +45° ± 5° from the 0 crossing point. The same phase shall be used as reference for the purpose of synchronisation for the different 
specimens.  SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
20 
 a) Test condition 
 The connections G1 of negligible impedance are replaced by the isolating switch D and by 
the SCPD.  
b) Test procedure  The following sequence of operations is performed: 
O - t - CO 
NOTE For the explanation of this s equence of operations see 18.101.1 g). 
19 Normal operation 
This clause of Part 1 applies except as follows. 
Addition: 
After the normal operation tests the isolating switch shall comply with 6 mA maximum leakage 
current test with a voltage of 110 % of the rated voltage. 
19.1  Replacement of Table 17: 
Table 17 – Number of operations for normal operation test 
Rated current Number of 
operations 
16 A, for isolating  switches having a rated voltage not exceeding 250 V a.c. of pattern 
number 2 40 000 
16 A, for pattern number 3 and 03 having a rated voltage not exceeding 250 V 
16 A, for isolating  switches having a rated voltage exceeding 250 V a.c.  20 000 
Above 16 A up to and including 40 A 10 000 
Above 40 A up to and including 80 A 5 000 
Above 80 A up to and including 125 A 1 000 
 
Replacement of the third paragraph starting from the end by: 
After the test, the specimen shall withstand an electric strength test as specified in 16.2 
without previous humidity treatment, the test voltage of 4 000 V being reduced by 1 000 V, and the other test voltages by 500 V, and a temperature rise test as specified in Clause 17, the test current being reduced to a value of the rated current. 
NOTE  In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted. 
In the UNITED KINGDOM, Table 17 of Part 1 applies.” 
20 Mechanical strength 
This clause of Part 1 applies. 
21 Resistance to heat 
This clause of Part 1 applies. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
21 
 22 Screws, current-carrying parts and connections 
This clause of Part 1 applies. 
23 Creepage distances, clearances and distances through sealing compound 
This clause of Part 1 applies except as follows. 
Replacement of point 1 of Table 20: 
1 Between live parts which are separated when the contacts are open  ......……………………………...4 101 
Replacement of point 6 of Table 20 
6 Between live parts which are separated when the contacts are open.......……………………………....4 101 
Addition of the following footnote to Table 20: 
101 If the value is lower than 4 mm but not lower than 3 mm compliance with this standard is given when the 
isolating switches fulfil the conditions of the test of 16.101. 
24 Resistance of insulating material to abnormal heat, to fire and to tracking 
This clause of Part 1 applies except as follows.  
24.2  Replacement of the first paragraph 
For isolating switches, parts of insulating material retaining live parts in position shall be of 
material resistant to tracking. 
25 Resistance to rusting 
This clause of Part 1 applies. 
26 EMC requirements 
This clause of Part 1 applies. 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
22 
 Figures  
Figures of Part 1 apply except as follows. 
Figure 1 
Addition: 
Addition of two rows to the table of dimensions: 
35 8,2 3,5 2,5 – – – – – – 
50 10 4 2,5 – – – – – – 
 
Figure 2 
Addition: Addition of two rows to the table of dimensions: 
Up to 35 8,2 – – – – 
Up to 50 10 – – – – 
 
Figure 3 
Addition: 
Addition of two rows to the table of dimensions: 
Up to 35 8,2 – 
Up to 50 10 – 
 
Figure 4 
Addition: 
Addition of two rows to the table of dimensions: 
Up to 35 9 – – 
Up to 50 9 – – 
 
Figure 5 
Addition: 
Addition of two rows to the table of dimensions: 
Up to 35 8.2 – 
Up to 50 10 – SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
23 
 Additional figures: 
 
O1 O2
G1G1 P T R1F R
L S 
R2
D
IEC   419/04  
  Key 
S  =  Supply 
R  =  Adjustable load resistor L  =  Adjustable load reactor 
T  =  Closing device 
F  =  Copper wire fuse R
1 = Fault current limiting resistor 
R2 = Resistor drawing a current of 10 A per phase 
P  = SCPD G
1  = Temporary connection for calibration 
O1  = Current sensor  
O2  = Voltage sensor 
D    = Isolating  switch under test 
 
Figure 101 – Test circuit for verification of the short circuit withstand capability  
with a SCPD of one-pole isolating  switch SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
24 
  
O1 O2
G1 G1 P T R1F R
L S 
R2
DR
L 
G1
G1N
IEC   420/04  
   Key 
S  =  Supply 
R  =  Adjustable load resistor 
L  =  Adjustable load reactor 
T  =  Closing device F   =  Copper wire fuse 
R
1 = Fault current limiting resistor 
R2 = Resistor drawing a current of 10 A per phase 
P = SCPD 
G1 = Temporary connection for calibration 
O1 = Current sensor  
O2 = Voltage sensor 
D = Isolating switch under test 
 
Figure 102 – Test circuit for verification of the short circuit withstand capability  
with a SCPD of a two-pole isolating  switch SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
25 
  
O1 O2
G1 G1 P T R1F R 
L S 
R2R
L 
G1
G1
DN
R
L 
G1
G1O2O2
O1 O1
IEC   421/04 
 
   Key 
S   =  Supply 
R   =  Adjustable load resistor 
L   =  Adjustable load reactor T   =  Closing device 
F   =  Copper wire fuse 
R
1 =  Fault current limiting resistor 
R2 =  Resistor drawing a current of 10 A per phase 
P  =  SCPD 
G1 = Temporary connection for calibration 
O1 =  Current sensor  
O2 =  Voltage sensor 
D  =  Isolating switch under test 
 
Figure 103 – Test circuit for verification of the short circuit withstand capability  
with a SCPD of a three-pole isolating  switch SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
26 
  
 
O1 O2
G1 G1 P T R1F R 
L S 
R2R
L 
G1
G1
DN
R
L 
G1
G1O2O2
O1 O1G1
IEC   422/04 
 
   Key 
S    =  Supply 
R    =  Adjustable load resistor 
L    =  Adjustable load reactor T    =  Closing device 
F    =  Copper wire fuse 
R
1  =  Fault current limiting resistor 
R2  =  Resistor drawing a current of 10 A per phase 
P    =  SCPD 
G1  = Temporary connection for calibration 
O1  =  Current sensor  
O2 =  Voltage sensor 
D    =  Isolating switch under test 
 
Figure 104 – Test circuit for verification of the short circuit withstand capability  
with a SCPD of a four-pole isolating  switch SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
27 
 48 200
20200
80
405
10
5,5
510 10 80
57 9
9025
12
1R = 131
2 2
4
IEC   423/04 
Dimensions in millimetres 
 Key 
1) Gliding plates 
2) Terminal 
3) Stop for gliding plate 
4) Silver wire 
Figure 105 – Test apparatus for verification of the minimum I2t and Ip values  
to be withstood by the isolating  switch SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
28 
 Annexes 
Annexes of Part 1 apply except as follows. 
Annex A 
Replacement: SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
29 
 Annex A  
(normative) 
Survey of specimens needed for tests 
The numbers of specimens needed for the tests according to 5.4 are as follows: 
 
Clauses and subclauses Number 
of specimens Number of 
additional 
specimens for 
dual current 
rating 
  6 Ratings A  
  7 Classification A  
  8 Marking A  
  9  Checking of dimensions ABC  
10 Protection against electric shock ABC  
11 Provision for earthing ABC  
12 Terminals a ABC JKL 
13 Constructional requirements b ABC  
14 Mechanism ABC  
15 Resistance to ageing, protecti on provided by enclosures of 
switches and resistance to humidity ABC  
16 Insulation resistance and electric strength ABC  
17 Temperature rise ABC JKL 
18.1 and18.2 Making and breaking capacity  ABC JKL 
19 Normal operation c ABC JKL 
16.101 Impulse test d ABC  
20 Mechanical strength subclauses 20.1 to 20.9 e ABC  
21 Resistance to heat ABC  
22 Screws, current-carrying parts and connections ABC  
23 Creepage distances, clearances and distances through sealing 
compound  
ABC  
18.101 Short circuit withstand capability XYZ + PQR  
16.101 Impulse test d XYZ  
19.2 Normal operation for fluorescent lamp circuits DEF MNO 
24.1 Resistance to abnormal heat and to fire GHI  
24.2 Resistance to tracking f GHI  
25 Resistance to rusting GHI  
 TOTAL 15 6 
a  Five extra screwless terminals are used for the test of  12.3.11 and one extra set of specimens is used for the 
test of 12.3.12. 
b An extra set of membranes are needed for each of the tests of 13.15.1 and 13.15.2. 
c For isolating switches of pattern number 2 one extra set of specimens is used. 
d Test to be carried out only if the clearance of item 6 of Clause 23 is lower than 4 mm. 
e One extra set of specimens of cord-operated isolating switches is needed for the test of 20.9. 
f One extra set of specimens may be used. 
 
 SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
30 
  
Annex B  
(normative) 
 
Additional requirements fo r switches having faciliti es for the outlet and 
retention of flexible cables 
 
This annex of Part 1 applies. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
31 
 Additional annexes: 
Annex AA  
(informative) 
 
Determination of short-circuit power factor 
  
AA.1 Introduction  
There is no method by which the short-circuit power factor can be determined with precision. 
Two examples of acceptable methods are given in this annex. 
AA.2 Method I – Determination from d.c. component 
The angle may be determined from the curve of the d.c. component of the asymmetrical current wave between the instant of the short-circuit and the instant of contact separation as follows: 
a) The formula for the d.c. component is: 
i
d =  Ido . e-Rt/L 
where 
id   is the value of d.c. components at the instant t; 
Ido  is the value of the d. c. component at the instant taken as time origin; 
L/R is the time constant of the circuit, in seconds; 
t   is the time, in seconds, taken from the initial instant; 
e   is the base of Napierian logarithms. 
The time-constant L/R can be ascertained from the above formula as follows: 
1) measure the value of Ido at the instant of short-circuit and the value of id at another 
instant t before contact separation;  
2) determine the value of e-Rt/L by dividing id by Ido;  
3) from a table of values of e-x, determine the value of -x corresponding to the ratio of 
id / Ido 
4) the value x represents Rt/L from which L/R is obtained. 
 
b) Determine the angle ϕ from: 
ϕ = arc tan ω L/R 
where ω is 2 π times the actual frequency. 
This method should not be used when the currents are measured by current transformers. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
32 
 AA.3 Method II - Determination with pilot generator 
When a pilot generator is used on the same shaft as the test generator, the voltage of the pilot generator on the oscillogram may be compared in phase first with the voltage of the test 
generator and then with the current of the test generator. 
The difference between the phase angles between pilot generator voltage and main generator 
voltage on the one hand and pilot generator voltage and test generator current on the other 
hand gives the phase angle between the voltage and current of the test generator, from which 
the power factor can be determined.  SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
33 
 Annex BB  
(informative) 
 
SCPDs for short-circuit tests 
  
BB.1 Introduction 
For the verification of the minimum I2t and lp values to be withstood by the isolating switch as 
given in Table 102, short-circuit tests have to be performed. The short-circuit tests shall be 
made by the use of a fuse or a silver wire using the test apparatus shown in Figure 105 or by 
the use of any other means producing the required I2t and lp values. 
BB.2 Silver wires 
For the purpose of verifying the minimum I2t and lp values to be withstood by the isolating 
switch, in order to obtain reproducible test results, the SCPD, if any, may be a silver wire 
using the test apparatus shown in Figure 105. 
For silver wires with at least 99,9 % purity, Table BB.1 gives an indication of the diameters 
according to the rated current ln and the short-circuit currents lnc. 
Table BB.1 – Indication of silver wire diameters as a function of rated currents  
and short-circuit currents 
lnc Silver wire diameter a in mm corresponding to 
A ln = 16 A 16 A < ln ≤ 32 A 32 A < ln ≤ 40 A 40 A< ln ≤ 63 A 63 A < ln ≤ 80 A 80 A < ln ≤ 125 A 
1 500 0,35 0,50 0,65 0,85 - - 
3 000 0,35 0,50 0,60 0,80 0,95 1,15 
4 500 0,35 0,50 0,60 0,80 0,90 1,15 
>6 000 0,35 0,50 0,60 0,75 0,90 1,00 
a The silver wire diameter values are essentially based on peak current ( Ip) considerations (see Table 102). 
 
NOTE In the UNITED KINGDOM, isolators having a rated current below 16 A are widely used and permitted.  
For current rating less than 16 A, the column for 16 A rating applies. 
The silver wire shall be inserted horizontally in the appropriate position of the test apparatus 
shown in Figure 105 and stretched. The silver wire shall be replaced after each test. 
BB.3 Fuses 
For the purpose of verifying the minimum I2t and lp values to be withstood by the isolating 
switch, in order to obtain reproducible test results, the SCPD, if any, may be a corresponding 
fuse. 
The rating of the fuse shall not be smaller than the rating of the isolating switch. Higher 
ratings of fuses may be used to obtain the I2t and lp values of Table 102. 
Intermediate values can be achieved by adding fuses in parallel. SAUDI ARABIAN STANDARD SASO IEC 60669-2-4/2007
 
34 
 BB.4 Other means 
Other means may be used provided that the values of Table 102 are fulfilled. 
Addition: 
Bibliography 
 
IEC 60664-1:1992, Insulation coordination for equipment within low-voltage systems – Part 1: 
Principles, requirements and tests 
IEC 60999 (all parts), Connecting devices – Electrical copper conductors – Safety require-
ments for screw-type and screw less-type clamping units 
 
___________