SIST EN 50356:2002

SLOVENSKI STANDARD
SIST EN 50356:2002
01-september-2002
Method for spark testing of cables
Method for spark testing of cables
Durchlaufspannungsprüfung an elektrischen Kabeln und Leitungen
Essai diélectrique au défilement à sec des câbles électriques
Ta slovenski standard je istoveten z: EN 50356:2002
ICS:
29.060.20 Kabli Cables
SIST EN 50356:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50356:2002

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SIST EN 50356:2002
EUROPEAN STANDARD EN 50356
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2002
ICS 29.060.20
English version
Method for spark testing of cables
Essai diélectrique au défilement à sec Durchlaufspannungsprüfung an
des câbles électriques elektrischen Kabeln und Leitungen
This European Standard was approved by CENELEC on 2002-03-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50356:2002 E

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SIST EN 50356:2002
EN 50356:2002 - 2 -
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 20, Electric
cables.
The text of the draft was submitted to the Unique Acceptance Procedure and was approved
by CENELEC as EN 50356 on 2002-03-01.
The following dates were fixed:
- latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-03-01
- latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-03-01
__________

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Contents
Introduction.4
1 Scope.5
2 Types of voltage waveform .5
3 Procedure.5
4 Equipment .5
5 Test voltages.8
6 Sensitivity.8
7 Calibration.9
Annex A (informative) Recommended minimum voltage levels.14
Annex B (informative) Example of an artificial fault device.16
Annex C (informative) Notes on the use of spark testing machines.17
Bibliography.18
Figure 1 — Requirements for pulsed waveforms – Rise time.11
Figure 2 — Requirements for pulsed waveforms – Fluctuation of peak value and pulse
repetition rate .12
Figure 3 — Requirements for pulsed waveforms – Pulse duration .13
Figure B.1 — Needle for use in the artificial fault device.16

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Introduction
The practice of using spark-testers to detect defects in the insulation or sheathing layers of electric
cables has been developed over many years of practical experience.
The operation of the equipment using the verification method described in this document has proved
to be satisfactory. This method employs an artificial fault simulator and its performance has been
shown to be comparable to that using operational efficacy tests involving the detection of artificially
prepared defects (i.e. faults in the insulation/sheathing material) in lengths of cable.

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1 Scope
The spark-test method specified in this standard is intended for the detection of defects in the
insulation or sheathing layers of electric cables. For single core cables with no outer metallic layer, the
general process is accepted as being equivalent to subjecting samples of those cables to a voltage
test in water.
This standard specifies the operational requirements for the spark-test equipment, as well as the
principal characteristics, functional parameters and calibration procedures for each type of test
equipment.
2 Types of voltage waveform
For the purposes of this standard, the types of voltage waveform used for spark-testing are divided
into the following groups:
a.c. an alternating current (a.c.) voltage of approximately sine-wave form, at the industrial
frequency of 40 Hz to 62 Hz;
d.c. a direct current (d.c.) voltage;
h.f. an alternating current (a.c.) voltage of approximately sine-wave form, at frequencies between
500 Hz and 1 MHz;
pulsed a voltage waveform comprising a fast rise time and highly damped wave-tail, as defined in 4.2.
NOTE Provided the manufacturer can demonstrate equivalent effectiveness, h.f. voltages at frequencies below 500 Hz may be
used.
3 Procedure
The insulated conductor or sheathed cable shall be passed through an electrode energised at the test
voltage. The method detailed in this standard provides for the application of a.c., d.c., h.f. and pulsed
voltages.
The requirements for voltage waveform, frequency and test voltage are given in 4.2 and clause 5. The
maximum speed at which the cable shall pass through the electrode is determined by the minimum
residence time specified in 4.6.
When used as an alternative to a voltage test in water, it is recommended that the test be restricted to
layer thicknesses not greater than 2,0 mm and to a.c. and d.c. test voltages.
The requirements are not applicable to cable insulation having a rated voltage (U ) greater than 3 kV.
0
Annex A provides recommended voltages for each voltage waveform, to be used in the absence of
any alternative voltages in the relevant cable standard.
4 Equipment
4.1 Safety
To limit the effect of electrical shock to personnel, for all types of voltage source, the equipment shall
be constructed such that the short-circuit current is limited to less than 10 mA r.m.s. or equivalent.
This requirement is additional to, or may be superseded by, any national regulation that prevails at the
time.
NOTE Guidance on the limiting of shock currents can be found in IEC 60479-1 and IEC 60479-2.

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EN 50356:2002 - 6 -
Further aspects of operational safety are given in Annex C.
4.2 High voltage source
The high voltage electrode shall be supplied in one of the following forms, as defined in clause 2: a.c.,
d.c., h.f. or pulsed.
For a d.c. test, connection to the test electrode shall be by means of a low capacitance unscreened
lead. For d.c. and pulsed voltage testing, the test electrode may be either positive or negative polarity,
the other pole being earthed.
The requirements for pulsed waveforms are presented in Figures 1, 2 and 3.
For pulsed waveforms, the rise time of the wave front shall reach 90 % of the specified peak value in
less than 75 �s – see Figure 1. Fluctuations of the actual peak value, due to variations of input power
into the generator, shall not exceed ± 2 % of the specified peak value – see Figure 2. The peak value
shall not show more than 5 % reduction in the event of an increase of capacitive load of 50 pF, during
the operation, from an initial load of 25 pF between electrode and instrument ground. The time that
each pulse remains at a voltage greater than 80 % of the specified peak voltage shall be between
20 �s and 100 �s – see Figure 3. The pulse repetition frequency shall be greater than 170 per second
and less than 500 per second. This corresponds to pulse separations between 2 000 �s and 5 880 �s.
Visible or audible corona shall be evident in the electrode structure when operating at the specified
voltage.
4.3 Voltage monitoring equipment
For a.c., d.c. and h.f. sources, the voltage between electrode and earth shall be displayed on a meter
either by connection directly to the output terminal of the high voltage source or by any suitable
equivalent arrangement. The measurement system shall have an accuracy of ± 5 % of the indicated
value.
For a pulse source there shall be a peak reading instrument voltmeter connected directly to the
electrode, continually indicating the voltage at the electrode, with or without a grounded test wire in the
test chamber. The peak reading voltmeter shall indicate full deflection at a peak value not exceeding
25 kV and with a precision level of ± 5 % of the indicated value.
NOTE If the spark-tester is to be controlled remotely, it should be noted that the current drawn by the cable under test can
cause variation of the test voltage. In this situation, the regulation of the voltage source needs to be sufficient to maintain the
voltage within the 5 % accuracy limit.
4.4 Fault indicator
There shall be a detection circuit to provide a visible and/or audible indication of failure of the
insulation or sheath to maintain the specified voltage. The fault detector shall be arranged to operate a
digital display counter such that one count per discrete fault is registered. It shall also be of a totalizer
type and cumulative to the end of the cable run. The counter shall maintain the indication until either
the next succeeding fault is registered or until the indication is manually cancelled.
4.5 Electrodes
An appropriate choice of electrode shall be made in order to obtain the maximum effective rate of
detection.
Types of cable to be tested (construction, materials, etc.) and the test conditions (linear speed, voltage
source mode, etc.) form some of the parameters to be considered.

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Examples of electrode types are
- contact types:
bead chain, spring loaded hyperbola, brushes (rotating or fixed),
- non-contact types:
metallic tube, rings.
4.6 Design of electrodes
4.6.1 Contact type
The electrode shall be of metallic construction and its length shall be such that every point of the
insulated conductor or non-metallic sheath under test is in electrical contact with the electrode for
times not less than the following:
a) for a.c. supply to the electrode: 0,05 s
NOTE 1  This time represents a maximum linear throughput speed of 1,2 m/min per millimetre of electrode. The minimum
length of the electrode (mm) is therefore given by 0,833 v, where v is the linear throughput speed in m/min.
b) for d.c. supply to the electrode : 0,001 s
NOTE 2  This time represents a maximum linear throughput speed of 60 m/min per millimetre of electrode. The minimum length
of the electrode (mm) is therefore given by 0,017 v, where v is the linear throughput speed in m/min.
s
0,002 5
c) for h.f. supply to the electrode:
f
where f is the supply frequency in kHz.
NOTE 3  This time represents a maximum linear throughput speed of 24 f m/min per millimetre of electrode. The minimum
length of the electrode (mm) is therefore given by 0,042 v/f, where v is the linear throughput speed in m/min.
s
2,5
d) for pulse supply to the electrode:
p
where p is the pulse repetition rate in pulses per second.
NOTE 4  This time represents a maximum linear throughput speed of 24 p m/min per millimetre of electrode. The minimum
length of the electrode (mm) is therefore given by 0,042 v/p, where v is the linear throughput speed in m/min.
4.6.2 Non-contact type (d.c. test only)
The electrode shall consist of a cylindrical metal tube or series of metallic rings. In either case the
internal diameter(s) shall not be greater than 15 mm. In the case of the ring type, the number of rings
shall be such that a uniform electric field is formed. These electrodes shall only be used with a d.c.
source and their length shall be such that every point of the insulated conductor or non-metallic sheath
is in the electrode for not less than 0,001 s.
NOTE This time represents a maximum linear throughput speed of 60 m/min per millimetre of electrode. The minimum length
of the electrode (mm) is therefore given by 0,017 v, where v is the linear throughput speed in m/min.
The design of the non-contact electrode shall be such that the cable under test is guided by any
suitable means along the central axis and be maintained in that position without undue deviation for
the duration of the test run.
The maximum recommended overall diameter of the core or cable to be tested using the non-contact
electrode system is 3,0 mm.
The use of this type of electrode shall be restricted to a test voltage of 18 kV.

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