SIST IEC 60364-7-713:2000

Electrical installations of buildings - Part 7: Requirements for special installations and locations - Section 713: Furniture

Applies to furniture connected by fixed wiring to the electrical installation of the building and also to the prefabricated furniture and furniture connected by means of a plug and socket-outlet unless these items are the subject of other IEC publications. Electrical equipment of furniture shall be connected to a single-phase supply < or = 240V, and the total load current shall not exceed 16 A.

Installations électriques des bâtiments - Partie 7: Règles pour les installations et emplacements spéciaux - Section 713: Mobilier

S'applique au mobilier connecté de manière fixe à l'installation électrique du bâtiment et également au mobilier préfabriqué et au mobilier connecté à l'installation électrique des bâtiments au moyen des prises de courant sauf si ce mobilier est soumis à d'autres publications de la CEI.  L'équipement électrique du mobilier doit être connecté à une alimentation monophasée sous une tension inférieure ou égale à 240 V, son courant d'emploi total ne doit pas dépasser 16 A.

Električne inštalacije zgradb – 7. del: Zahteve za posebne inštalacije in lokacije – 713. oddelek: Pohištvo

General Information

• Status: Withdrawn
• Publication Date: 31-Jan-2000
• Withdrawal Date: 26-Nov-2019
• ICS: 91.140.50 - Electricity supply systems
• ICS: 97.140 - Furniture
• Technical Committee: ELI - Electrical and communication installations
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 27-Nov-2019
• Due Date: 20-Dec-2019
• Completion Date: 27-Nov-2019
• Ref Project: IEC 61869-14:2018 - Instrument transformers - Part 14: Additional requirements for current transformers for DC applications

Standards Content (Sample)

SLOVENSKI STANDARD
SIST IEC 60364-7-713:2000
01-februar-2000
(OHNWULþQHLQãWDODFLMH]JUDGE±GHO=DKWHYH]DSRVHEQHLQãWDODFLMHLQORNDFLMH±
RGGHOHN3RKLãWYR
Electrical installations of buildings - Part 7: Requirements for special installations and
locations - Section 713: Furniture
Installations électriques des bâtiments - Partie 7: Règles pour les installations et
emplacements spéciaux - Section 713: Mobilier
Ta slovenski standard je istoveten z: IEC 60364-7-713
ICS:
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
97.140 Pohištvo Furniture
SIST IEC 60364-7-713:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST IEC 60364-7-713:2000

---------------------- Page: 2 ----------------------

SIST IEC 60364-7-713:2000
NORME CEI
IEC
INTERNATIONALE
364-7-713
INTERNATIONAL
Première édition
STAN DARD First edition
1996-02
bâtiments
Installations électriques des —
Partie 7:
Règles pour les installations et emplacements
spéciaux —
Section 713: Mobilier
Electrical installations of buildings —
Part 7:
Requirements for special installations
and locations —
Section 713: Furniture
© CEI 1996 Droits de reproduction réservés — Copyright — all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
PRICE CODE
IEC Me*ayHapomiaa 3nefsrpoyexHH4ecnaR HoMuccus
voir catalogue en vigueur
Pour prix,
For price, see current catalogue

---------------------- Page: 3 ----------------------

SIST IEC 60364-7-713:2000
– 3 –
364-7-713 © IEC:1996
CONTENTS
Page
FOREWORD 5
Clause
700.1 Introduction 7
713 Furniture 7
713.1 General 7
713.1.1 Scope 7
713.1.2 Normative references 7
11
713.1.3 Definitions
11 Selection and erection of electrical equipment
713.5
11
713.51 Common rules
11
713.52 Wiring systems
13
713.55 Other equipment

---------------------- Page: 4 ----------------------

SIST IEC 60364-7-713:2000
364-7-713 © IEC:1996 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTRICAL INSTALLATIONS OF BUILDINGS -
Part 7: Requirements for special installations and locations -
Section 713: Furniture
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international co-operation on all questions concerning standardization in the electrical and electronic
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The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
5)
equipment declared to be in conformity with one of its standards.
Attention is drawn to the possibility that some of the elements of this International Standard may be the
6)
subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 364-7-713 has been prepared by IEC technical committee 64:
Electrical installations of buildings.
The text of this standard is based on the following documents:
FDIS Report on voting
64/811/FDIS 64/835/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

---------------------- Page: 5 ----------------------

SIST IEC 60364-7-713:2000
364-7-713 © IEC:1996 – 7 -
ELECTRICAL INSTALLATIONS OF BUILDINGS -
Part 7: Requirements for special installations and locations -
Section 713: Furniture
700.1 Introduction
The requirements of part 7 supplement, modify or replace the general requirements of the other
parts of IEC 364. The numbers following the particular number of the section of part 7 are
those of the corresponding parts, chapters, sections or clauses of IEC 364. The absence of a
reference to a chapter, section or clause means that the corresponding general requirements
are applicable.
713 Furniture
713.1 General
713.1.1 Scope
The particular requirements of this section apply to the wiring system of furniture (and similar
fitments) which is connected to the electrical installation.
Examples are beds, cupboards, desks and shop display cases, in which electrical equipment
such as luminaries, socket-outlets, switching devices and wiring systems are installed.
The requirements of this section apply to furniture connected by fixed wiring to the electrical
installation of the building and also to prefabricated furniture and furniture connected by means
of a plug and socket-outlet unless these items are the subject of other IEC publications.
Electrical equipment of furniture shall be connected to a single-phase supply <240 V, and the
total load current shall not exceed 16 A.
The requirements do not apply to electrical appliances and equipment specifically designed for
installation in furniture and which are the subject of other IEC publications, for example radios,
TV receivers, refrigerators and laboratory tables, installe
...

IEC 61869-14
®

Edition 1.0 2018-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Instrument transformers –
Part 14: Additional requirements for current transformers for DC applications

Transformateurs de mesure –
Partie 14: Exigences supplémentaires concernant les transformateurs de
courant pour application en courant continu

IEC 61869-14:2018-07(en-fr)

---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61869-14

®


Edition 1.0 2018-07




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Instrument transformers –

Part 14: Additional requirements for current transformers for DC applications




Transformateurs de mesure –

Partie 14: Exigences supplémentaires concernant les transformateurs de

courant pour application en courant continu















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 17.220.20 ISBN 978-2-8322-5803-3




Warning! Make sure that you obtained this publication from an authorized distributor.

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------
– 2 – IEC 61869-14:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 7
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 11
5 Ratings . 16
6 Design and construction . 20
7 Tests . 25
Annex 14A (informative) Equivalent thermal current in CTs for DC application . 37
14A.1 General . 37
14A.2 Current harmonic content . 37
14A.3 Losses in primary conductor due to harmonic content . 38
14A.4 Thermal test with AC current . 40
Annex 14B (informative) Proposed rated insulation level applicable to current
transformers for DC application. 41
Bibliography . 42

Figure 1401 – Example of LCC scheme . 7
Figure 1402 – Typical scheme for VSC – symmetrical monopole . 8
Figure 1403 – Typical scheme for VSC – asymmetrical monopole or bipole . 9
Figure 1404 – Typical step responses of a system . 14
Figure 1405 – Accuracy limits of a DCCT . 19
Figure 1406 – Polarity reversal test profile . 30
Figure 1407 – Measurement of the step response time . 32
Figure 14A.1 – Typical waveform of current flowing in the primary conductor for LCC
applications . 37
Figure 14A.2 – The two terms that make up the total losses in the primary conductor . 39
Figure 14A.3 – Additional losses in conductors due to typical current harmonics . 40
Figure 14A.4 – Power-frequency losses in conductors compared to DC losses . 40

Table 1401 – Current and voltage in current transformers for LCC application . 8
Table 1402 – Current and voltage in current transformers for VSC application . 10
Table 3 – Partial discharge test voltages and permissible levels . 17
Table 1403 – Limits of ratio error for DCCT (classes from 0,1 to 1) . 19
Table 7 – Static withstand test loads . 21
Table 8 – Arc fault duration and performance criteria . 22
Table 1404 – Markings of terminals . 23
Table 1405 – Rating plate marking for common rating plate . 24
Table 1406 – Rating plate marking for each secondary converter . 24
Table 1407 – Rating plate marking for auxiliary power supply . 25

---------------------- Page: 4 ----------------------
IEC 61869-14:2018 © IEC 2018 – 3 –
Table 10 – List of tests. 26
Table 14A.1 – Typical harmonic current values (800 kV LCC) . 38
Table 14B.1 – Proposed rated primary terminal insulation levels for current
transformers for DC application. 41

---------------------- Page: 5 ----------------------
– 4 – IEC 61869-14:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

INSTRUMENT TRANSFORMERS –

Part 14: Additional requirements for current
transformers for DC applications

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61869-14 has been prepared by IEC technical committee 38:
Instrument transformers.
The text of this standard is based on the following documents:
FDIS Report on voting
38/560/FDIS 38/565/RVD

Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 6 ----------------------
IEC 61869-14:2018 © IEC 2018 – 5 –
A list of all parts in the IEC 61869 series, published under the general title Instrument
transformers, can be found on the IEC website.
This Part 14 is to be used in conjunction with, and is based on, IEC 61869-1:2007, General
requirements, and IEC 61869-6:2016, Additional general requirements for low-power
instrument transformers – however the reader is encouraged to use the most recent editions.
This Part 14 follows the structure of IEC 61869-1:2007 and IEC 61869-6:2016 and
supplements or modifies their corresponding clauses.
When a subclause of Part 1 or Part 6 is not mentioned in this Part 14, that subclause applies.
When this standard states “addition”, “modification” or “replacement”, the relevant text in
Part 1 or Part 6 is to be adapted accordingly.
For additional clauses, subclauses, figures, tables, annexes or notes, the following numbering
system is used:
• clauses, subclauses, tables, figures and notes that are numbered starting from 1401 are
additional to those in Part 1 and Part 6;
• additional annexes are lettered 14A, 14B, etc.
An overview of the planned set of standards at the date of publication of this document is
given below. The updated list of standards issued by IEC TC 38 is available at the website:
www.iec.ch
PRODUCT FAMILY STANDARDS PRODUCT PRODUCTS OLD
STANDARD STANDARD
61869-1 61869-2 ADDITIONAL REQUIREMENTS FOR 60044-1
CURRENT TRANSFORMERS 60044-6
GENERAL
REQUIREMENTS
61869-3 ADDITIONAL REQUIREMENTS FOR 60044-2
INDUCTIVE VOLTAGE TRANSFORMERS
61869-4 ADDITIONAL REQUIREMENTS FOR 60044-3
COMBINED TRANSFORMERS
61869-5 ADDITIONAL REQUIREMENTS FOR 60044-5
CAPACITIVE VOLTAGE TRANSFORMERS
ADDITIONAL REQUIREMENTS FOR
61869-6 61869-7 60044-7
ELECTRONIC VOLTAGE TRANSFORMERS
ADDITIONAL
GENERAL 61869-8 ADDITIONAL REQUIREMENTS FOR 60044-8
REQUIREMENTS
ELECTRONIC CURRENT
FOR LOW-POWER
TRANSFORMERS
INSTRUMENT
DIGITAL INTERFACE FOR INSTRUMENT
61869-9
TRANSFORMERS
TRANSFORMERS
61869-10 ADDITIONAL REQUIREMENTS FOR LOW-
POWER PASSIVE CURRENT
TRANSFORMERS
61869-11 ADDITIONAL REQUIREMENTS FOR LOW- 60044-7
POWER PASSIVE VOLTAGE
TRANSFORMERS
61869-12 ADDITIONAL REQUIREMENTS FOR
COMBINED ELECTRONIC INSTRUMENT
TRANSFORMER OR COMBINED LOW-
POWER PASSIVE TRANSFORMERS
61869-13 STAND ALONE MERGING UNIT
ADDITIONAL REQUIREMENTS FOR
61869-14
CURRENT TRANSFORMERS FOR DC
APPLICATIONS
61869-15 ADDITIONAL REQUIREMENTS FOR
VOLTAGE TRANSFORMERS FOR DC
APPLICATIONS

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– 6 – IEC 61869-14:2018 © IEC 2018
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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understanding of its contents. Users should therefore print this document using a
colour printer.

---------------------- Page: 8 ----------------------
IEC 61869-14:2018 © IEC 2018 – 7 –
INTRODUCTION
General
This document applies to current transformers intended to be used in DC applications with at
least one of the following functions:
• measure DC current (with significant harmonics);
• withstand DC voltage.
Depending on the position of the current transformer on the DC system, different kinds of
application exist, which are briefly described below, together with the approximate voltage or
current wave shape.
Line-commutated converters (LCC)
Line-commutated converters (LCC) are based on thyristor converters (see Figure 1401). They
are characterized by a single direction of current flow, and a voltage polarity reversal
possibility. Significant voltage and current harmonics exist up to frequencies of about 3 kHz to
4 kHz.

Figure 1401 – Example of LCC scheme
We distinguish three different current-measurement functions:
• CT1: measurement of the current at the AC side of the converter;
• CT2: measurement of the current at the DC side of the converter;
• CT3: measurement of the current in the DC filter.
Table 1401 gives an overview of the current and voltage waveshapes as well as the main
characteristics of the different applications of the CT.

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– 8 – IEC 61869-14:2018 © IEC 2018
Table 1401 – Current and voltage in current transformers for LCC application
Current Voltage Characteristics
CT1 AC current
AC + DC voltage
Large amount of current harmonics
Mainly for protection purposes


CT2 Pure DC application
High-accuracy measurement
Harmonics measurement
Metering, control and protection
purposes


CT3 DC voltage stress with harmonics
DC current = 0
Harmonics measurement
Mainly for protection purposes



Voltage-source converters (VSC)
Voltage-source converters (VSC) are based on transistor converters. They are characterized
by a bi-directional current flow and a single voltage polarity. Voltage and current harmonics
exist up to frequencies of about 20 kHz.
Two variants of VSC schemes exist: symmetrical monopoles (using one single converter) and
asymmetrical monopole or bipole (with one converter for each polarity).
Both schemes are shown in Figure 1402 and Figure 1403.

Figure 1402 – Typical scheme for VSC – symmetrical monopole

---------------------- Page: 10 ----------------------
IEC 61869-14:2018 © IEC 2018 – 9 –

Figure 1403 – Typical scheme for VSC – asymmetrical monopole or bipole
We distinguish three different current-measurement functions:
• CT4: measurement of the current in the transistor branches of the converter.
The CT can be placed before (CT4a) or after the transistor branch (CT4b);
• CT2: measurement of the current at the DC side of the converter;
• CT3: measurement of the current in the DC filter (not always present in this scheme).
Table 1402 gives an overview of the current and voltage waveshapes as well as the main
characteristics of the different applications of the CT.

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– 10 – IEC 61869-14:2018 © IEC 2018
Table 1402 – Current and voltage in current transformers for VSC application
Current Voltage Characteristics
CT2 Pure DC application
High accuracy
measurement
Harmonics measurement
Metering, control and
protection purposes
Short step response time


CT3 DC voltage stress
DC current = 0
Harmonics measurement
Mainly for protection
purposes


CT4a Symmetrical monopole: Pure AC voltage or DC +
AC voltage
DC + AC current
High-accuracy
measurement
Short step response time


Asymmetrical monopoles /
bipoles:

CT4b DC voltage stress
DC + AC current
High-accuracy
measurement
Short step response time

---------------------- Page: 12 ----------------------
IEC 61869-14:2018 © IEC 2018 – 11 –
INSTRUMENT TRANSFORMERS –

Part 14: Additional requirements for current
transformers for DC applications



1 Scope
This part of IEC 61869 provides all requirements specific to current transformers to be used in
DC applications (DCCTs), whatever the technology used. The output signal can be analogue
or digital.
It is applicable to newly manufactured current transformers used for measuring, protection
and/or control applications in DC power systems with a rated voltage above 1,5 kV.
The general configuration of a single-pole low-power instrument transformer is described in
Figure 601 of IEC 61869-6:2016.
The DCCTs intended for current measurement in the transistor branch of the VSC valve
(referred to as CT4a and CT4b in Figure 1403 and Table 1402) are not covered by this
document, and will be considered in a future revision.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
Clause 2 of IEC 61869-6:2016 is applicable, with the following additions and modifications:
IEC TS 60815-4:2016, Selection and dimensioning of high-voltage insulators intended for use
in polluted conditions – Part 4: Insulators for DC systems
IEC TS 61245:2015, Artificial pollution tests on high-voltage ceramic and glass insulators to
be used on DC systems
IEC 61869-6:2016, Instrument transformers – Part 6: Additional general requirements for low-
power instrument transformers
IEC 61869-9:2016, Instrument transformers – Part 9: Digital interface for instrument
transformers
3 Terms and definitions
Clause 3 of IEC 61869-1:2007, of IEC 61869-6:2016 and of IEC 61869-9:2016 are applicable
with the following additions and modifications.

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– 12 – IEC 61869-14:2018 © IEC 2018
3.1 General definitions
3.1.1401
instrument transformer for DC application
instrument transformer intended to be used in DC applications with at least one of the
following functions:
• measure DC current or DC voltage (with significant harmonics);
• withstand DC voltage.
3.1.1402
current transformer for DC application
DCCT
instrument transformer for DC application in which the secondary signal, under normal
conditions of use, is substantially proportional to the primary current
Note 1 to entry: The different applications are described in the introduction.
3.2 Definitions related to dielectric ratings
3.2.2
highest voltage for equipment
U
m
Definition 3.2.2 of IEC 61869-1:2007 is replaced by the following one:
highest value of DC voltage for which the equipment is designed to operate continuously, in
respect of its insulation as well as other characteristics that relate to this voltage
3.3 Definitions related to current ratings
3.3.1401
DC overload current
overcurrent occurring in an electric circuit, which is not caused by a short-circuit or an earth
fault
Note 1 to entry: The DC overload current is specified by the customer in terms of value and duration.
[SOURCE: IEC 60050-826:2004, 826-11-15, modified – “DC” added in the term and Note 1 to
entry added.]
3.3.1402
short-time overload current
I
sov
DC overload current occurring for a duration shorter than one minute
3.3.1403
long-time overload current
I
lov
DC overload current occurring for a duration of minutes or hours
Note 1 to entry: Different values of long-time overload can be specified for different durations.
3.3.1404
maximum peak fault current
I
sc
maximum peak value of current occurring during a fault condition of the DC power system

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3.4 Definitions related to accuracy
3.4.1401
Absolute error
ε
A
error (expressed in A) that a current transformer introduces into the measurement and which
arises from the fact that the actual transformation ratio is not equal to the rated transformation
ratio
Note 1 to entry: The absolute error is defined by the following formula:

ε = K ⋅ U – I
A r s p
where
K is the rated transformation ratio;
r
I is the DC value of the actual primary current in steady state;
p
U is the DC value of the output voltage.
s
3.5 Definitions related to other ratings
3.5.1401
step response
duration between the instant when the measurand (or quantity supplied) is subjected to a
specified abrupt change and the instant when the indication (or quantity supplied) reaches,
and remains within specified limits of, its final steady-state value
Note 1 to entry: See graphical explanation in Figure 1404.

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a
 For periodic behaviour
b
 For aperiodic behaviour
u Input variable
U Initial value of the input variable
0
U Step height of the input variable
s
v Output variable
V , V Steady-state values before and after application of the step
0 ∞
v Overshoot
m
Specified tolerance limit
2 ∆v
s
T Step response time
sr
T Settling time
s
T Dead time
t
Figure 1404 – Typical step responses of a system
Note 2 to entry: The dead time includes the delay time.
[SOURCE: IEC 60050-311:2001, 311-06-04 and IEC 60050-351:2013, 351-45-27 modified –
Note 1 to entry has been added; the notes of the sources have been deleted.]

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3.5.1402
step response time
T
sr
for a step response, the duration of the time interval between the instant of the step change of
an input variable and the instant when the output variable reaches for the first time a specified
percentage of the difference between the final and the initial steady-state values
Note 1 to entry: The step response time includes the delay time of the current transformer.
[SOURCE: IEC 60050-351:2013, 351-45-36, modified – Note 1 to entry has been modified
and the figure has been deleted.]
3.5.1403
settling time
T
s
for a step response, the duration of the time interval between the instant of the step change of
an input variable and the instant when the difference between the step response and their
steady-state value remains smaller than the transient value tolerance
Note 1 to entry: The settling time includes the delay time of the current transformer.
[SOURCE: IEC 60050-351:2013, 351-45-37, modified – Note 1 to entry has been modified
and the figure has been deleted.]
3.5.1404
overshoot
v
m
for a step response of a transfer element, the maximum transient deviation from the final
steady-state value of the output variable, usually expressed in percent of the difference
between the final and the initial steady-state values and for reference-variable step respon
...