IEC TR 60269-5:2014/AMD1:2020

IEC TR 60269-5 ®
Edition 2.0 2020-12
TECHNICAL
REPORT
AMENDMENT 1
Low-voltage fuses –
Part 5: Guidance for the application of low-voltage fuses

IEC TR 60269-5:2014-03/AMD1:2020-12(en)

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IEC TR 60269-5 ®
Edition 2.0 2020-12
TECHNICAL
REPORT
AMENDMENT 1
Low-voltage fuses –
Part 5: Guidance for the application of low-voltage fuses

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.120.50 ISBN 978-2-8322-9174-0

– 2 – IEC 60269-5:20/AMD1:2020
© IEC 2020
FOREWORD
This amendment has been prepared by subcommittee 32B: Low voltage fuses, of IEC
technical committee 32: Fuses.
This amendment corrects and adds to IEC TR 60269-5 published in 2014. This edition
constitutes a technical revision.
This amendment includes the following significant technical changes with respect to the
original document:
a) addition of battery fuses;
b) new clause on inverter protection;
c) numerous details improved.
The text of this amendment is based on the following documents:
Draft TR Report on voting
32B/694/DTR 32B/697A/RVDTR
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
_____________
2 Normative References
Replace the existing reference to IEC 60269-1:2006 by the following new reference:
IEC 60269-1:2006, Low-voltage fuses - Part 1: General requirements
IEC 60269-1:2006/AMD1:2009
IEC 60269-1:2006/AMD2:2014
Replace the existing reference to IEC 60269-4:2009 by the following new reference:
IEC 60269-4, Low-voltage fuses - Part 4: Supplementary requirements for fuse-links for the
protection of semiconductor devices
Replace the existing reference to IEC 60947-3:2008 by the following new reference:
IEC 60947-3:2015, Low-voltage switchgear and controlgear - Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units

IEC 60269-5/AMD1 – 3 –
© IEC 2020
4 Fuse benefits
Replace the existing text of bullet point h) by the following new text:
h) Compact size offers economical overcurrent protections at high short-circuit levels
Add the following new bullet point after point p):
q) Fuse-links will operate independent of the operation position of the fuse. The operation
position is usually vertical. Other positions of use are permissible. The deratings of the
manufacturers of the fuse must be observed.

5 Fuse construction and operation
5.2.1 Fuse-link
Replace the existing third paragraph of 5.2.1 by the following new text:
The fuse-element is usually made of flat silver or copper with multiple restrictions in the cross-
section. This restriction is an important feature of fuse design, normally achieved by precision
stamping.
Replace the existing first sentence of the fourth paragraph of 5.2.1 by the following new text:
M-effect (see 5.3.3) is sometimes added to the fuse-element to achieve controlled fuse
operation in the overload range.

5.3.2 Fuse operation in case of short-circuit
Replace the existing bullet points by the following new text:
• the arcing stage (t ): the arcs begin at restrictions and are then extinguished by the filler.
a
• M-effect (see 5.3.3) is sometimes added to the fuse-element to achieve controlled fuse
operation in the overload range;

5.3.3 Fuse operation in case of overload
Replace the existing third bullet point by the following new text:
• Both stages make up the fuse operating time (t + t ). The energy generated in the circuit
m a
by the overload current during pre-arcing (melting) time and operating time can still be
2 2
represented by the pre-arcing I t and operating I t values, respectively;
however under overload conditions the pre-arcing I t value is so high it provides little
useful application data and the prearcing time is the preferred measure for times longer
than a few cycles or few time constants. In this case, arcing time is negligible compared to
the prearcing time.
5.3.5 Fuse operation in altitudes exceeding 2 000 m
Replace the second sentence of the first paragraph of 5.3.5 by the following new text:

– 4 – IEC 60269-5:20/AMD1:2020
© IEC 2020
This is as stated in IEC 60269-1:2014, Subclause 3.2.
Replace the existing second and third paragraphs of 5.3.5 by the following new text:
For the current carrying capacity of a fuse and the cable to be influenced by the cooling effect
of the surrounding air, the current carrying capacity is derated with lower air pressure. This
can be described by the following approximation:
Above 2 000 m a de-rating factor of 0,5 % for every 100 m above 2 000 m will be required,
due to reduced convection of heat and lower air pressure.

6 Fuse-combination units
Replace the second sentence of the first paragraph of Clause 6 by the following new text:
Fuse-combination units are shown in Table 2 (equivalent to Table 1 of IEC 60947-3:2008).

Table 2 – Definitions and symbols of switches and fuse-combination units
Replace existing Table 2 by the following new table:

IEC 60269-5/AMD1 – 5 –
© IEC 2020
Replace the existing last paragraph of Clause 6 by the following new text:
The fuse(s) fitted to a fuse-combination unit or fuse-combination switch also protect the unit
or the switch itself against the effects of overcurrent.

7 Fuse selection and markings
Renumber the existing note after the second paragraph of Clause 7 as Note 1.
Table 3
Add the following new row to the end of Table 3:
gBat, aBat Protection of batteries Full and partial range

Replace the text of the final bullet point of the eighth paragraph of Clause 7 by the following
new text:
• Size*) or reference
Add the following new note after the final bullet point of the eighth paragraph of Clause 7:

– 6 – IEC 60269-5:20/AMD1:2020
© IEC 2020
NOTE 2 The definition of fuse sizes, especially the dimensions are given by IEC 60269-2. In general fuse- links
and fuse-bases and fuse-combination units shall have the same size. Some manufacturers offer to use a smaller
fuse-link size in a bigger fuse-base or fuse-combination unit.
Example: size 1 fuse-link used in size 2 fuse-switch disconnector. Those combinations shall be tested and
confirmed by the manufacturer.

8 Conductor protection
Figure 6 – Currents for fuse-link selection

Figure 1 – Currents for fuse-link selection
8.6 Utilization category gK
Replace, in the first sentence of 8.6, "limitating" by "limiting".

8.7 Utilization category gPV
Replace, in the first sentence of 8.7, "(see Clause 19.)." by "(see Clause 19).".

Add the following new Subclause 8.8 and renumber existing Subclause 8.8 as 8.9:
8.8 Utilization category gBat
Selection of a fuse for battery systems. These fuse-links are for overload and short circuit
protection.
IEC 60269-5/AMD1 – 7 –
© IEC 2020
8.9 Protection against short-circuit current only
Replace, in the first sentence of Subclause 8.9 (formerly 8.8), the phrase "let through I t" by
"operating I t".
9 Selectivity of protective devices
9.2.1 General
2 2
In the second sentence of the NOTE replace the phrase "let through I t" by "operating I t".

9.3 Selectivity of circuit upstream breakers of fuses
Replace the existing title of Subclause 9.3 by the following new title:
Selectivity between circuit-breakers upstream and fuses

9.4 Selectivity of upstream fuses of circuit breakers
Replace the existing title of Subclause 9.4 by the following new title:
Selectivity between fuses upstream and circuit-breakers

9.4.3 Verification of selectivity for operating times < 0,1s
Replace, in the first sentence of 9.4.3, the word "prearcing" by "pre-arcing".

Figure 11 – Verification of selectivity between fuse F and circuit-breaker C for
2 3
operating time t < 0,1 s
Replace, in the note to Figure 11, "I " by "I ".
c S
12 Transformer Protection
12.1 Distribution transformers with a high-voltage primary
Replace the second sentence of the first paragraph of 12.1 by the following new text:
Short-circuit protection of these transformers are generally provided by high voltage fuse-
links on the primary, and such fuse-links are selected to withstand the transformer
magnetising (inrush) current during energization.

– 8 – IEC 60269-5:20/AMD1:2020
© IEC 2020
15 Protection of semiconductor devices in a.c. and d.c. rated voltage circuits
Add, at the beginning of Clause 15, the following new Subclause heading:
15.1 General recommendations
Replace the existing text of the second sentence of the third paragraph of Clause 15 by the
following new text:
(In this connection, experience has shown that semiconductors fail as a short-circuit
protection and a large current results.)
Add, at the end of Clause 15, the following new subclauses:
15.2 Fuse application with inverters
15.2.1 Inverters
Figures 17 to 19 show examples of inverters of voltage source type.

Figure 17 – Inverter double-way connection with arm fuses
for regenerative or non-regenerative load

IEC 60269-5/AMD1 – 9 –
© IEC 2020
Figure 18 – Inverter double-way connection with d.c. loop fuses
for regenerative or non-regenerative load

Figure 19 – Multi inverters systems double-way connection with
d.c. loop fuses for regenerative or non-regenerative load
Fast fuses can protect the junction of a GTO thyristor against the effect of a large current. As
for transistors, IGBT junctions cannot be protected by fuses because of their extremely low I t
value. Nevertheless, as for other semiconductors, a high fault current will cause the explosion
of the IGBT case because of the energy built up inside the component. A lot of power tests
demonstrate that the explosion I t of the IGBT can be defined and show that fast fuses can
prevent an IGBT from exploding.
Moreover tests have been made to measure the fuse contribution to the inductance of the
circuit and the effect of high frequencies on the current carrying capability of the fuse. The
fuse technology and the circuit design play a great part in the total inductance of the circuit.
The publication of appropriate curves and data is absolutely necessary to allow the selection
of a fuse for the protection of power inverters.

– 10 – IEC 60269-5:20/AMD1:2020
© IEC 2020
15.2.2 Purpose of the fuse
15.2.2.1 General
The purpose of the fuse is to protect the equipment against a semiconductor explosion or
when it is possible to protect the semiconductor junction in case of short circuit.
The fuse's main purpose is then to stop the capacitor discharge due to a short circuit made by
two arms in series conducting simultaneously.
Two arms will create such a short circuit when one semiconductor is triggered at the wrong
time or fails.
The fuse-link will operate very quickly as the di/dt is generally very high because of the very
low value of the inductance L (see Figure 20).
The short circuit current is the sum of the capacitor discharge current icap and the d.c. current
id coming from the d.c. power source (Figure 6).
However the value of the inductance L (between the power source and the capacitor) is much
larger than the value of the inductance of the capacitor discharge current. Then when the
fuse-link operates the cut-off current I would be still very small
...