SIST EN 60099-4:2005/A1:2007

SIST EN 60099-4:2005/A1:2007

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SIST EN 60099-4:2005/A1:2007


EUROPEAN STANDARD
EN 60099-4/A1

NORME EUROPÉENNE
August 2006
EUROPÄISCHE NORM

ICS 29.120.50; 20.240.10


English version


Surge arresters
Part 4: Metal-oxide surge arresters without gaps
for a.c. systems
(IEC 60099-4:2004/A1:2006)


Parafoudres  Überspannungsableiter
Partie 4: Parafoudres à Teil 4: Metalloxidableiter ohne
oxyde métallique sans éclateurs Funkenstrecken für
pour réseaux à courant alternatif Wechselspannungsnetze
(CEI 60099-4:2004/A1:2006) (IEC 60099-4:2004/A1:2006)




This amendment A1 modifies the European Standard EN 60099-4:2004; it was approved by CENELEC on
2006-07-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this amendment 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 amendment 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, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the 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


© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60099-4:2004/A1:2006 E

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SIST EN 60099-4:2005/A1:2007
EN 60099-4:2004/A1:2006 - 2 -
Foreword
The text of document 37/324/FDIS, future amendment 1 to IEC 60099-4:2004, prepared by IEC TC 37,
Surge arresters, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
amendment A1 to EN 60099-4:2004 on 2006-07-01.
The following dates were fixed:
– latest date by which the amendment has to be
implemented at national level by publication of
an identical national standard or by endorsement (dop) 2007-04-01
– latest date by which the national standards conflicting
with the amendment have to be withdrawn (dow) 2009-07-01
__________
Endorsement notice
The text of amendment 1:2006 to the International Standard IEC 60099-4:2004 was approved by
CENELEC as an amendment to the European Standard without any modification.
__________

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SIST EN 60099-4:2005/A1:2007


INTERNATIONAL IEC


STANDARD 60099-4



2004



AMENDMENT 1
2006-05

Amendment 1
Surge arresters –
Part 4:
Metal-oxide surge arresters without gaps
for a.c. systems

This English-language version is derived from the original
bilingual publication by leaving out all French-language
pages. Missing page numbers correspond to the French-
language pages.
 IEC 2006 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
S
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 3 –
FOREWORD
This amendment has been prepared by IEC technical committee 37: Surge arresters.
The text of this amendment is based on the following documents:
FDIS Report on voting
37/324/FDIS 37/325/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 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.
_____________

Page 3
CONTENTS
Replace, on page 7, the title of Annex N by the following new title:
Annex N (normative) Test procedure to determine the lightning impulse discharge capability
Page 9
Add:
Figure 13 – Examples of arrester units
Figure 14 – Short-circuit test setup
Figure 15 – Example of a test circuit for re-applying pre-failing current immediately before
applying the short-circuit test current
Delete the titles of Figures N.1, N.2 and N.3.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 5 –
Page 11
Add:
Table 14 – Test requirements
Table 15 – Required currents for short-circuit tests
Delete the titles of Tables N.1, N.2 and N.3.

Page 51
6.11 Short circuit
Replace the text of this subclause by the following:
An arrester for which a short-circuit rating is claimed by the manufacturer shall be subjected
to a short-circuit test according to 8.7 to show that the arrester will not fail in a manner that
causes violent shattering of the housing and that self-extinguishing of open flames (if any)
occurs within a defined period of time.
6.12.1 Disconnector withstand
Add to this subclause the following third dashed item:
– for surge arresters to be installed in overhead lines with system voltages exceeding 52 kV,
test of the lightning impulse discharge capability (see Annex N).
Page 53
Add, after 6.16, the following new subclause:
6.17 Lightning impulse discharge capability
For surge arresters to be installed in overhead lines with system voltages exceeding 52 kV,
the lightning impulse discharge capability shall be demonstrated by the tests and procedures
of Annex N.

Page 57
Table 3 – Arrester type tests
Delete all references to Annex N.

Page 75
Add, after 8.5.2.2, on page 77, the following new subclauses:

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 7 –
8.5.2.3 Test procedure for resistor elements stressed at or above the reference voltage
If U is close to or above the reference voltage, it may not be possible to perform an
ct
accelerated ageing test at U , due to the extreme voltage dependence for the power losses
ct
and stability of available voltage source. If U ≥ 0,95*U and if it is not possible to perform
ct ref
an accelerated ageing test according to 8.5.2.1, this alternative test procedure shall apply and
replaces 8.5.2.1 and 8.5.2.2.
NOTE To provide an overview and to serve as an aid to understanding the procedure, the steps required are as
follows.
1) Calculate power loss, P , for the highest stressed resistor (at T = 40 °C and U = U ).
ct a c
2) Determine the steady-state temperature, T , for the highest stressed part of the arrester by using one of the
st
three alternative procedures of 8.5.2.3.1.
3) At a voltage U , determine the ratio, k , of power loss at 115 °C to power loss at T for the type of resistor
ct x st
elements used.
4) Perform an accelerated ageing test at constant power loss, k * P .
x ct
5) Interrupt the test for a short time and take measurements of power loss at specified time intervals.
6) If T > 60 °C, increase test temperature or test time.
st
7) Evaluate the power losses of step 5) according to 8.5.2.3.3.
8.5.2.3.1 Determination of test parameters
Calculate the power losses, P , per resistor element at the maximum ambient temperature of
ct
40 °C with the arrester energized at U , for the highest voltage stressed resistor according to
c
Annex L including the effect of the resistive current.
NOTE 1 For dead-front and liquid-immersed arresters, 65 °C and 95 °C, respectively, apply as maximum ambient
temperatures.
Select one of the three following test procedures to determine the steady-state temperature,
T , of the most stressed part of the arrester at maximum ambient temperature.
st
NOTE 2 The test procedures are considered to be conservative in increasing order from 1 to 3.
1. At an ambient temperature of 25 °C ± 10 K, energize the complete arrester at the claimed
U until steady-state temperature conditions have been attained. The temperature shall be
c
measured on resistor elements, at five points as evenly spaced as possible over the most
highly stressed 20 % portion of the length of each column of the arrester. If this 20 %
portion contains less than five resistor elements, the number of measuring points may be
limited to one point on each resistor element. The average temperature rise above
ambient of the resistor elements shall be added to the maximum ambient temperature to
obtain the temperature T .
st
2. At the maximum ambient temperature, energize a thermally pro-rated section
representative for the arrester type at a voltage level, which results in the same power
losses per resistor element as determined above. Keep the power losses constant by
adjusting the voltage if necessary. Measure the temperature of the resistors in steady-
state condition and calculate the average steady-state temperature, which is set equal to
T
st.
3. At an ambient temperature of 25 °C ± 10 K, energize a thermally pro-rated section
representative for the arrester type at a voltage level which results in the same power
losses per resistor element as determined above. Keep the power losses constant by
adjusting the voltage if necessary. Measure the temperature of the resistors in steady-
state condition and calculate the average steady-state temperature rise, ΔT , above
st
ambient. Determine the temperature, T by adding ΔT to the maximum ambient
st , st
temperature.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 9 –
The prorated section shall represent the steady-state thermal behaviour of the complete
arrester.
NOTE 3 The section may not necessarily be the same as that used for the operating duty test.
At a voltage U , determine the ratio, k , of power losses at 115 °C to power losses at T for
ct x st
the type of resistor elements used. For this test the voltage source shall fulfil the requirements
according to 8.5.1.
8.5.2.3.2 Test procedure
Three resistor samples shall be subjected to constant power losses equal to k *P (tolerance
x ct
+30
%) for 1 000 h. During the test, the temperature shall be controlled to keep the surface
0
temperature of the resistor at the required test temperature T ± 4 K. The applied test voltage
t
at the start of the test shall be not less than 0,95*U .
ct
If the temperature, T , is equal to or below 60 °C, T shall be 115 °C. If T is above 60 °C,
st t st
either the test temperature or the testing time shall be increased as follows.
a) Increase of the test temperature
= 115 + (T – T – ΔT )
T
t st a,max n
where
T is the test temperature in °C;
t
T is the steady-state temperature of the resistors in °C;
st
T is the maximum ambient temperature in °C;
a,max
ΔT = 20 K.
n
NOTE 1 For liquid-immersed arresters ΔT = 25 K, which results from the requirement that the operating duty test
n
starting temperature for these arresters (120 °C) is 25 K above the maximum ambient temperature (95 °C), while
for other arresters the difference between the operating duty test starting temperature and the maximum ambient
temperature is 20 K.
b) Increase of the testing time
ΔT/10
t = t * 2,5
0
where
t is the testing time in h;
t = 1 000 h;
0
ΔT is the temperature above 60 °C.
NOTE 2 For dead-front and liquid-immersed arresters, t is 2 000 h and 7 000 h, respectively, and ΔT is the
0
temperature above 85 °C and 120 °C, respectively.
8.5.2.3.3 Determination of elevated rated and continuous operating voltages
The three test samples shall be heated to T ± 4 K and subjected to the constant power losses
t
k *P . One to two hours after the voltage application, the voltage is adjusted to a voltage in
x ct
the range 0,95* U to U and the power losses, P , are measured. During the test, after
ct ct 1ct
30 %, 50 % and 70 % of the testing time, the measurement of power losses is repeated under
the same conditions with respect to temperature and voltage. The minimum power loss values
at these times are designated as P . At the end of the ageing test, under the same
3ct
conditions with regard to block temperature and at the same voltage, the power losses P
2ct
are determined.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 11 –
• If P is equal to or below 1,1 times P , then the test according to 8.5.4 and 8.5.5 shall
2ct 3ct
be performed on new resistors:
– if P is equal to or less than P , U and U are used without any modification;
2ct 1ct sc sr
– if P > P , the ratio P /P is determined for each sample. The highest of these
2ct 1ct 2ct 1ct
ratios is called K . On three new resistors at ambient temperature, the power losses
ct
P and P are measured at U and U , respectively. Thereafter, the voltages are
1c 1r sc sr
increased so that the corresponding power losses P and P fill the relation:
2c 2r
P P
2c 2r
= K ; = K
ct ct
P P
1c 1r
U * and U * are the highest of the three increased voltages obtained. As an alternative,
c r
aged resistors may also be used after agreement between the user and the manufacturer.
• If P is greater than 1,1 times P , and P is greater than or equal to P , then aged
2ct 3ct 2ct 1ct
resistors shall be used for the following test of 8.5.4 and 8.5.5. New resistors with
corrected values U * and U * can be used, but only after agreement between the user and
c r
the manufacturer.
Aged resistors are, by definition, resistors tested according to 8.5.2.3.2.
These cases are summarized in Table 7.
Where aged resistors are used in the operating duty test, it is recommended that the time
delay between the ageing test and the operating duty test be not more than 24 h.
The measuring time should be short enough to avoid increased power loss due to heating.

Page 91
8.7 Short-circuit test procedure

Replace the title and contents of 8.7 by the following new title and text:
8.7 Short-circuit tests
8.7.1 General
Arresters, for which a short-circuit rating is claimed by the manufacturer, shall be tested in
accordance with this subclause. The test shall be performed in order to show that an arrester
failure does not result in a violent shattering of the arrester housing, and that self-
extinguishing of open flames (if any) occurs within a defined period of time. Each arrester
type is tested with four values of short-circuit currents. If the arrester is equipped with some
other arrangement as a substitute for a conventional pressure relief device, this arrangement
shall be included in the test.
The frequency of the short-circuit test current supply shall be between 48 Hz and 62 Hz.
With respect to the short-circuit current performance, it is important to distinguish between
two designs of surge arresters.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 13 –
– “Design A” arresters have a design in which a gas channel runs along the entire length of
the arrester unit and fills ≥50 % of the internal volume not occupied by the internal active
parts.
– “Design B” arresters are of a solid design with no enclosed volume of gas or having an
internal gas volume filling <50 % of the internal volume not occupied by the internal active
parts.
NOTE 1 Typically, “Design A” arresters are porcelain-housed arresters, or polymer-housed arresters with a
composite hollow insulator which are equipped either with pressure-relief devices, or with prefabricated weak spots
in the composite housing which burst or flip open at a specified pressure, thereby decreasing the internal pressure.
Typically, “Design B” arresters do not have any pressure relief device and are of a solid type with no enclosed
volume of gas. If the resistors fail electrically, an arc is established within the arrester. This arc causes heavy
evaporation and possibly burning of the housing and/or internal material. These arresters’ short-circuit performance
is determined by their ability to control the cracking or tearing-open of the housing due to the arc effects, thereby
avoiding violent shattering.
NOTE 2 "Active parts" in this context are the non-linear, metal-oxide resistors and any metal spacers directly in
series with them.
Depending on the type of arrester and test voltage, different requirements apply with regard to
the number of test samples, initiation of short-circuit current and amplitude of the first short-
circuit current peak. Table 14 shows a summary of these requirements which are further
explained in the following subclauses.
NOTE 3 After agreement between the manufacturer and the purchaser, the test procedure can be modified to
include, for example, a number of reclosing operations. For such special tests, the procedure and acceptance
criteria should be agreed upon between the manufacturer and the purchaser.
8.7.2 Preparation of the test samples
For the high-current tests, the test samples shall be the longest arrester unit used for the
design with the highest rated voltage of that unit used for each different arrester design.
For the low-current test, the test sample shall be an arrester unit of any length with the
highest rated voltage of that unit used for each different arrester design.
NOTE 1 Figure 13 shows different examples of arrester units.
In case a fuse wire is required, the fuse wire material and size shall be selected so that the
wire will melt within the first 30 electrical degrees after initiation of the test current.
NOTE 2 In order to have melting of the fuse wire within the specified time limit and create a suitable condition for
arc ignition, it is generally recommended that a fuse wire of a low resistance material (for example copper,
aluminium or silver) with a diameter of about 0,2 mm to 0,5 mm be used. Higher fuse-wire cross-sections are
applicable to surge arrester units prepared for higher short-circuit test currents. When there are problems in
initiating the arc, a fuse wire of larger size but with a diameter not exceeding 1,5 mm, may be used since it will
help arc establishment. In such cases, a specially prepared fuse wire, having a larger cross-section along most of
the arrester height with a short thinner section in the middle, may also help.
8.7.2.1 “Design A” arresters
The samples shall be prepared with means for conducting the required short-circuit current
using a fuse wire. The fuse wire shall be in direct contact with the MO resistors and be
positioned within, or as close as possible to, the gas channel and shall short-circuit the entire
internal active part. The actual location of the fuse wire in the test shall be reported in the test
report.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 15 –
No differences with regard to polymer housings or porcelain housings are made in the
preparation of the test samples. However, differences partly apply in the test procedure (see
8.7.4.2). In this case, “Design A” arresters with polymeric sheds which are not made of
porcelain or other hollow insulators, and which are as brittle as ceramics, shall be considered
and tested as porcelain-housed arresters.
8.7.2.2 “Design B” arresters
“Design B” arresters with polymeric sheds which are not made of porcelain or other
mechanically supporting structures, and which are as brittle as ceramics, shall be considered
and tested as porcelain-housed arresters.
8.7.2.2.1 Polymer-housed arresters
No special preparation is necessary. Standard arrester units shall be used. The arrester units
shall be electrically pre-failed with a power frequency overvoltage. The overvoltage shall be
run on completely assembled test units. No physical modification shall be made to the units
between pre-failing and the actual short-circuit current test.
The overvoltage given by the manufacturer shall be a voltage exceeding 1,15 times U . The
c
voltage shall cause the arrester to fail within (5 ± 3) min. The resistors are considered to have
failed when the voltage across the resistors falls below 10 % of the originally applied voltage.
The short-circuit current of the pre-failing test circuit shall not exceed 30 A.
The time between pre-failure and the rated short-circuit current test shall not exceed 15 min.
NOTE The pre-failure can be achieved by either applying a voltage source or a current source to the samples.
2
– Voltage source method: the initial current should typically be in the range 5-10 mA/cm . The short-circuit
current should typically be between 1 A and 30 A. The voltage source need not be adjusted after the initial
setting, although small adjustments might be necessary in order to fail the resistors in the given time range.
2
– Current source method: Typically a current density of around 15 mA/cm with a variation of ±50 %, will result
in failure of the resistors in the given time range. The short-circuit current should typically be between 10 A
and 30 A. The current source need not be adjusted after the initial setting, although small adjustments might
be necessary in order to fail the resistors in the given time range.
8.7.2.2.2 Porcelain-housed arresters
The samples shall be prepared with means for conducting the required short-circuit current
using a fuse wire. The fuse wire shall be in direct contact with the MO resistors and be
located as far away as possible from the gas channel and shall short-circuit the entire internal
active part. The actual location of the fuse wire in the test shall be reported in the test report.
8.7.3 Mounting of the test sample
For a base-mounted arrester, the mounting arrangement is shown in Figures 14a and 14b.
The distance to the ground from the insulating platform and the conductors shall be as
indicated in Figures 14a and 14b.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 17 –
For non-base-mounted arresters (for example, pole-mounted arresters), the test sample shall
be mounted on a non-metallic pole using mounting brackets and hardware typically used for
real service installation. For the purpose of the test, the mounting bracket shall be considered
as a part of the arrester base. In cases where the foregoing is at variance with the
manufacturer's instructions, the arrester shall be mounted in accordance with the installation
recommendations of the manufacturer. The entire lead between the base and the current
sensor shall be insulated for at least 1 000 V. The top end of the test sample shall be fitted
with the base assembly of the same design of an arrester or with the top cap.
For base-mounted arresters, the bottom end fitting of the test sample shall be mounted on a
test base that is at the same height as a surrounding circular or square enclosure. The test
base shall be of insulating material or may be of conducting material if its surface dimensions
are smaller than the surface dimensions of the arrester bottom end fitting. The test base and
the enclosure shall be placed on top of an insulating platform, as shown in Figures 14a and
14b. For non-base-mounted arresters, the same requirements apply to the bottom of the
arrester. The arcing distance between the top end cap and any other metallic object (floating
or grounded), except for the base of the arrester, shall be at least 1,6 times the height of the
sample arrester, but not less than 0,9 m. The enclosure shall be made of non-metallic
material and be positioned symmetrically with respect to the axis of the test sample. The
height of the enclosure shall be 40 cm ± 10 cm, and its diameter (or side, in case of a square
enclosure) shall be equal to the greater of 1,8 m or D in Equation (1) below. The enclosure
shall not be permitted to open or move during the test.
D = 1,2 × (2 × H + D) (1)
arr
where
H is the height of tested arrester unit;
D is the diameter of tested arrester unit.
arr
Porcelain-housed arresters shall be mounted according to Figure 14a. Polymer housed
arresters shall be mounted according to Figure 14b.
Test samples shall be mounted vertically unless agreed upon otherwise between the
manufacturer and the purchaser.
NOTE 1 The mounting of the arrester during the short-circuit test and, more specifically, the routing of the
conductors should represent the most unfavourable condition in service.
The routing shown in Figure 14a is the most unfavourable to use during the initial phase of the test before venting
occurs (especially in the case of a surge arrester fitted with a pressure relief device). Positioning the sample as
shown in Figure 14a, with the venting ports facing in the direction of the test source, may cause the external arc to
be swept in closer proximity to the arrester housing than otherwise. As a result, a thermal shock effect may cause
excessive chipping and shattering of porcelain weather sheds, as compared to the other possible orientations of
the venting ports. However, during the remaining arcing time, this routing forces the arc to move away from the
arrester, and thus reduces the risk of the arrester catching fire. Both the initial phase of the test as well as the part
with risk of catching fire are important, especially for arresters where the external part of the housing is made of
polymeric material.
For all polymer-housed arresters, the ground conductor should be directed to the opposite direction as the
incoming conductor, as described in Figure 14b. In this way, the arc will stay close to the arrester during the entire
duration of the short-circuit current, thus creating the most unfavourable conditions with regards to the fire hazard.
NOTE 2 In the event that physical space limitations of the laboratory do not permit an enclosure of the specified
size, the manufacturer may choose to use an enclosure of lesser diameter.
8.7.4 High-current short-circuit tests
Three samples shall be tested at currents based on selection of a rated short-circuit current
selected from Table 15. All three samples shall be prepared according to 8.7.2 and mounted
according to 8.7.3.

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SIST EN 60099-4:2005/A1:2007
60099-4 Amend. 1  IEC:2006 – 19 –
Tests shall be made in a single-phase test circuit, with an open-circuit test voltage of 77 % to
107 % of the rated voltage of the test sample, as outlined in 8.7.4.1. However, it is expected
that tests on high-voltage arresters will have to be made at laboratories which might not have
the sufficient short-circuit power capability to carry out these tests at 77 % or more of the test
sample rated voltage. Accordingly, an alternative procedure for making the high-current,
short-circuit tests at a reduced voltage is given in 8.7.4.2. The measured total duration of test
current flowing through the circuit shall be ≥0,2 s.
NOTE Experience from porcelain-housed arresters has shown that tests at the rated current do not necessarily
demonstrate acceptable behaviour at lower currents.
8.7.4.1 High-current tests at full voltage (77 % to 107 % of rating)
The prospective current shall first be measured by making a test with the arrester short-
circuited or replaced by a solid link of negligible impedance.
The duration of such a test may be limited to the minimum time required to measure the peak
and symmetrical component of the current waveform.
For “Design A” arresters tested at the rated short-circuit current, the peak value of the first
half-cycle of the prospective current shall be at least 2,5 times the r.m.s. value of the
symmetrical component of the prospective current. The following r.m.s. value of the
symmetrical component shall be equal to the rated short-circuit current or higher. The peak
value of the prospective current, divided by 2,5, shall be quoted as the test current, even
though the r.m.s. value of the symmetrical component of the prospective current may be
higher. Because of the higher prospective current, the sample arrester may be subjected to
more severe duty, and, therefore, tests at X/R ratio lower than 15 shall only be carried out
with the manufacturer’s consent.
For “Design B” arresters tested at rated short-circuit current, the peak value of the first half-
cycle of the prospective current shall be at least √2 times the r.m.s. value.
For all the reduced short-circuit currents, the r.m.s. value shall be in accordance with Table
15 and the peak value of the first half-cycle of the prospective current shall be at least √2
times the r.m.s. value of this current.
The solid shorting link shall be removed after checking the prospective current and the
arrester sample(s) shall be tested
...