IEC 60853-2:1989/AMD1:2008

Amendment 1 - Calculation of the cyclic and emergency current rating of cables - Part 2: Cyclic rating of cables greater than 18/30 (36) kV and emergency ratings for cables of all voltages

Amendement 1 - Calcul des capacités de transport des câbles pour les régimes de charge cycliques et de surcharge de secours - Partie 2: Régime cyclique pour des câbles de tensions supérieures à 18/30 (36) kV et régimes de secours pour des câbles de toutes tensions

General Information

• Status: Published
• Publication Date: 14-Oct-2008
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.060.20 - Cables
• Technical Committee: TC 20 - Electric cables
• Drafting Committee: WG 19 - TC 20/WG 19
• Current Stage: PPUB - Publication issued
• Start Date: 30-Nov-2008
• Completion Date: 15-Oct-2008

Standards Content (Sample)

IEC 60853-2
Edition 1.0 2008-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
Calculation of the cyclic and emergency current rating of cables –
Part 2: Cyclic rating of cables greater than 18/30 (36) kV and emergency ratings
for cables of all voltages
Calcul des capacités de transport des câbles pour les régimes de charge
cycliques et de surcharge de secours –
Partie 2: Régime cyclique pour des câbles de tensions supérieures à 18/30
(36) kV et régimes de secours pour des câbles de toutes tensions

IEC 60853-2:1989/A1:2008
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IEC 60853-2
Edition 1.0 2008-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
Calculation of the cyclic and emergency current rating of cables –
Part 2: Cyclic rating of câbles greater than 18/30 (36) kV and emergency ratings
for câbles of all voltages
Calcul des capacités de transport des câbles pour les régimes de charge
cycliques et de surcharge de secours –
Partie 2: Régime cyclique pour des câbles de tensions supérieures à 18/30
(36) kV et régimes de secours pour des câbles de toutes tensions

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
K
CODE PRIX
ICS 29.060.20 ISBN 978-2-88910-313-3
– 2 – 60853-2 Amend. 1 © IEC:2008
FOREWORD
This amendment has been prepared by IEC technical committee 20: Electric cables.
The text of this amendment is based on the following documents:
FDIS Report on voting
20/965/FDIS 20/991/RVD
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 maintenance result date indicated on the IEC web site 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.
_____________
PREFACE
Replace the quoted IEC publication “287(1982)”, by the following:
IEC 60287-1-1, Electric cables – Calculation of the current rating – Part 1-1: Current rating
equations (100 % load factor) and calculation of losses – General
IEC 60287-2-1, Electric cables – Calculation of the current rating – Part 2-1:Thermal
resistance – Calculation of thermal resistance
IEC 60287-3-1, Electric cables – Calculation of the current rating – Part 3-1:Sections on
operating conditions – Reference operating conditionsand selection of cable type
Throughout the standard, replace all references to “IEC Publication 287” by “the IEC 60287
series”.
Add the following new reference:
IEC 60853-3, Calculation of the cyclic and emergency current rating of cables – Part 3: Cyclic
rating factor for cables of all voltages, with partial drying of the soil
1.1 General
Replace the first paragraph by the following:
This standard gives manual methods for calculating cyclic rating factors for cables whose
internal thermal capacitance cannot be neglected; in general this applies to cables for
voltages greater than 18/30 (36) kV. It also gives a method for calculating the emergency
rating for cables of any voltage. IEC 60853-1 deals with cyclic rating factors for cables of
voltages not greater than 18/30 (36) kV where the internal thermal capacitance could be

60853-2 Amend. 1 © IEC:2008 – 3 –
neglected. IEC 60853-3 deals with cyclic rating factors for cables of all voltages when partial
drying of the soil occurs.
Delete the fourth paragraph.
Add the following three new paragraphs at the end of 1.1:
When the load current changes in discrete and multiple steps the method set out in Clause 4
can be used to determine the temperature response of the cable.
This method shall be used carefully where a large number of steps is considered, or long
duration steps are dealt with, or large variations of the load current occur.
As the method involves an iterative process, the convergence criterion shall be adapted to the
different situations.
2 Symbols
Replace the word “sheath” by “metallic sheath or screen” under definitions Q q , q and q
,
s a j s.
Throughout the text, starting with the “Unit” column, replace “J/m.K” with “J/Km” also replace
“K.m/W” with “Km/W”.
Replace the definition for N with “N = number of cables in a group, or, for touching cables, the
number of circuits, see 7.4 b)”
Replace “δ ” by ”σ” in order to align with the French version. Also in the “Unit” column, replace
3 3
“J/K.m “ by “J/Km ”.
Add the following new definition:
Steady-state conductor temperature rise above ambient due to
Δθ Κ
d
dielectric losses
4.2.1.1 Single-core cables
Replace, in the second line, the word “sheath” by “metallic sheath or screen”.
4.2.1.2 Three-core cables
Replace the existing Equation (4-2) by the following new Equation (4-2):
⎛ 2πT ⎞
⎜ ⎟
−
⎜ ⎟
ρ
⎝ i ⎠
d = D e (4-2)
c i
Replace, in the first line after Equation (4-2) and in the first line of 4.2.1.2 b), the word
“sheath” by “metallic sheath or screen”.
4.2.2.1 General
Add, at the end of the subcause, a third paragraph as follows:
For single-core cables in trefoil formation, the values of T and T are adjusted by the
1 3
appropriate factors given in IEC 60287-2-1.

– 4 – 60853-2 Amend. 1 © IEC:2008
4.2.2.2 Representation of common types of cable
Replace, after Equation (4-6), in the definition for Q and twice in the definition for q , the word
s s
“sheath” by “metallic sheath or screen”.
4.2.4.1 Buried cables (directly or in ducts)
Replace the existing Equation (4-36) by the following new Equation (4-36):
⎧ 2 2 ⎫
⎡ ⎤
2 ⎡ ⎤
⎡ ⎤ k=N −1 ⎛ ⎞ ⎛ ⎞
⎛ ⎞ ′
2 − (d ) - (d )
⎡ ⎤
ρ W − D ⎛ ⎞
⎪ ⎜ pk ⎟ ⎜ pk ⎟ ⎪
− L ⎢ ⎥
T I ⎜ e ⎟ ⎢ ⎥
⎢ ⎥
⎜ ⎟
θ (t ) = − Ei −⎢− Ei ⎥ + − Ei − − Ei (4-36)
⎨ ⎜ ⎟ ⎜ ⎟ ⎬
⎜ ⎟ ∑ ⎢ ⎢ ⎥⎥
e
⎢ ⎜ ⎟ ⎥
4π 16tδ tδ 4tδ 4tδ
⎜ ⎟ ⎢ ⎥
⎪ ⎜ ⎟ ⎜ ⎟ ⎪
⎝ ⎠
⎣ ⎦ ⎢ ⎥
k=1 ⎢ ⎥
⎢ ⎝ ⎠ ⎥
⎣ ⎦
⎝ ⎠ ⎝ ⎠
⎣ ⎦
⎣ ⎦
⎩ ⎭
Replace the final sentence of 4.2.4.1 beginning “This formula has been simplified … “ by the
following new paragraph:
Equation (4-36) is the general equation for the transient response of buried cables and its
application for cyclic rating purposes is given in Clause 7. It is noted that this equation cannot
be used directly for cables in unfilled troughs.
4.3.2.1 General
Add, at the end of this subclause, a new paragraph as follows:
For single-core cables in trefoil formation the values of T and T are adjusted by the
1 3
appropriate factors given in IEC 60287-2-1.
4.3.2.2 Representation of common types of cable
Replace the existing Equation (4-47) by the following new equation:
T = T + q T + q T + q T (4-47)
B 1 s f a 2 j 3
4.4.1 Transient temperature response
Add the following new text after item b).
When the temperature response to a current that changes in discrete and multiple steps is
calculated, the calculations described in this clause should be repeated for every partial step
of the current. In the calculation of these partial transients, the correct heat source (the heat
gained or lost in the partial current step) and the correct temperatures (for the calculation of
electrical resistances) shall be used in the formulas above. One way of accomplishing this is
to perform iterative calculations for each load step as follows:
1) Start with the temperature achieved at the end of the previous load step.
2) Calculate the electrical resistances corresponding to this temperature and obtain power
losses.
3) With these losses calculate the temperature at the end of the time step.
4) Use this temperature to recalculate the electrical resistances and power losses and go to
step 3.
5) Repeat steps 3 and 4 until convergence is achieved and go to the next load step.
The total temperature response per partial step will be found by using the appropriate
formulae in this clause. The complete total temperature response of the cable circuit will be

60853-2 Amend. 1 © IEC:2008 – 5 –
found by adding all the partial transients, thereby taking the time differences between the
partial steps into account.
4.4.1.2 Cables in air
Replace the last paragraph by the following:
T is the external thermal resistance due to air in the steady-state, calculated according to
IEC 60287-2-1, and shall be expressed as a quantity per conductor or equivalent conductor.
4.4.2 Correction to transient temperature response for variation in conductor losses
with temperature (emergency ratings only)
Replace the heading of this subclause with the words “Not used”.
Delete the text of this subclause, including Equation (4-73).
4.4.3.2 Cables at voltages higher than 275 kV
Replace, in the third line, and in the penultimate paragraph, the word “sheath” by “metallic
sheath or screen”.
Add, at the end of the subclause, the following new text:
Information on the voltages above which dielectric losses should be considered is given in
IEC 60287-1-1.
5.1 General
Replacethe existing Equation (5-1) by the following new Equation (5-1):
θ = Y θ (1) + Y [θ (2) − θ ()1 ]+ Y [θ (3) − θ (2)]
max 0 R 1 R R 2 R R
(5-1)
+Y[]θ (6) − θ (5) + μ[θ (∞) − θ (6)]
5 R R R R
5.2.1 Any load cycle of known shape
Replace the existing Equation (5-3) by the following new Equation (5-3):
M =
(5-3)
1/ 2
⎛ ⎞
⎡ θ()i + 1 θ ()i ⎤ ⎡ θ ()6 ⎤
⎜ R R R ⎟
Y − + μ 1 −
⎢ ⎥ ⎢ ⎥
∑
i
⎜ ⎟
θ ()∞ θ ()∞ θ ()∞
⎢ ⎥ ⎢ ⎥
⎣ R R ⎦ ⎣ R ⎦
i=0
⎝ ⎠
5.2.2 Flat top load cycle
Replace the existing Equation (5-5) by the following new Equation (5-5):
1/ 2
⎡ 1 ⎤
M = (5-5)
⎢ ⎥
()1−()1 − μ[]1 − α(6) + kα(6){1− β(6)}
⎣ ⎦
7.2 Single isolated circuit
Under item a) 1), replace ” … for cables in ducts, in trefoil or flat touching formation….” by
”….for cables in trefoil or flat touching formation or in ducts… “

– 6 – 60853-2 Amend. 1 © IEC:2008
7.4 Group of “N”circuits, each of three single-core identical touching cables or ducts,
all cables having equal losses
Replace the existing title and
...