DC with tan voltage value as ig ed by the man facturer to the eq ipment or a p rt of it, c aracterisin the sp cified p rmanent over 5 min with tan ca a i ty of its in ulation [SOURCE: IE
Marking 1 4
Surge arresters shall be identified by the following minimum information which shall appear on the rating plate (nameplate):
• nominal discharge current In in kA;
• rated short circuit current Is in kA;
• manufacturer's name or trademark, type and identification;
NOTE The rated voltage of a DC metal-oxide arresters coincides with continuous operating voltage as per the operating duty test
According to IEC 60099-4:2009, section 3.8, the rated voltage of a surge arrester is the maximum permissible RMS value of power-frequency voltage between its terminals, ensuring correct operation under long-term overvoltage conditions as determined by the operating duty test This rated voltage is the 10 s power-frequency voltage utilized in the operating duty test following high-current or long-duration impulses.
In the operating duty test, thermal stability must be demonstrated within 30 minutes after applying the rated voltage For surge arresters in AC systems, the typical ratio of rated voltage to U_c is approximately 1.25, reflecting a specific long-term overvoltage that can arise during fault conditions In contrast, conditions in DC systems differ significantly.
According to IEC 60850 the supply voltages of traction systems are defined The highest non-permanent voltage
U max2 is specified for durations ranging from 1 second to 5 minutes Selecting a surge arrester with U c greater than U max2 ensures that the operating duty test outlined in section 6.5 accounts for all impacts of long-term overvoltages exceeding 1 second, providing a substantial safety margin In DC systems, there are no higher long-term overvoltages that can be classified as a "rated voltage."
Service conditions 1 4
Normal service conditions 1 4
Surge arresters that meet international standards are designed to function effectively under specific service conditions, including an ambient temperature range of -40 °C to +40 °C, compliance with solar radiation requirements as outlined in IEC 62498-2:2010, and an altitude limit of 1,400 m Additionally, they must adhere to pollution levels of PD 1 for indoor and PD 4 for outdoor installations, as specified in IEC 62497-1 These devices should also be installed near rail tracks on foundations that mitigate the impact of train vibrations and shocks, while being capable of operating satisfactorily under conventional accelerations.
– horizontal acceleration ( gh ): 5 m/s 2 ; f) surge arresters for onboard rolling stock shall be able to withstand vibrations and shocks that occur in service as defined in IEC 61 373;
Abnormal service conditions 1 5
When manufacturing or applying surge arresters, it is crucial to consider specific abnormal service conditions that may impact their performance These conditions include temperatures exceeding +40 °C or dropping below -40 °C, operation at altitudes above 1,400 m, exposure to harmful fumes or vapors, and contamination from smoke, dirt, or salt spray Additionally, excessive moisture, live washing, and the presence of explosive dust or gas mixtures pose significant risks Mechanical factors such as earthquakes, vibrations, and unusual transportation or storage methods must also be taken into account Furthermore, proximity to heat sources, non-vertical or suspended installations, and torsional or tensile loading can affect the integrity of the arrester, especially if it is used as a mechanical support.
Requirements 1 5
Insulation withstand of the arrester housing 1 5
The insulation of the arrester housing shall be coordinated with the arrester protective characteristics Tests shall be performed according to 6.2.
Reference voltage 1 5
Measuring the reference voltage is essential for selecting the appropriate test sample during the operating duty test, as outlined in section 6.5 The reference voltage of a DC surge arrester is determined at a specific reference current, which usually falls within the range of 0.05 mA.
Single column arresters require a minimum current of 1.0 mA per square centimeter of the disc area The manufacturer must specify and publish the minimum reference voltage of the arrester at the reference current used for routine testing.
Residual voltages 1 6
The maximum residual voltages for a specific design, considering all specified currents and wave shapes, are derived from type test data and the maximum residual voltage recorded during routine tests as published by the manufacturer To calculate the maximum residual voltage for any current and wave shape, the residual voltage from type-tested samples is multiplied by a scale factor This scale factor is determined by the ratio of the declared maximum residual voltage, verified during routine testing, to the measured residual voltage of the samples under identical current and wave shape conditions.
Internal partial discharges 1 6
The internal partial discharges of the arrester energized at 1 ,05 times its continuous operating voltage shall not exceed 1 0 pC.
Seal leakage 1 6
For arresters having an enclosed gas volume and a separate sealing system, seal leak rates shall be specified as defined in 6.9.
Current distribution in a multi-column arrester 1 6
The manufacturer shall specify the unbalance of the current distribution in a multicolumn arrester.
Charge transfer 1 6
Arresters shall be able to withstand the charge transfer test as specified in 6.4.
Operating duty 1 6
Arresters shall be able to withstand the combination of stresses arising in service as demonstrated by the operating duty tests, see 6.5.
Short circuit behaviour 1 6
Arresters must endure a short circuit test as outlined in section 6.6, ensuring they do not fail in a way that leads to violent shattering of the housing Additionally, any open flames must self-extinguish within a specified timeframe.
4.3.1 0 Protective characteristics of the arresters
The protective features of arresters are defined by three key factors: a) the residual voltage for steep current impulses as outlined in section 6.3.2; b) the residual voltage versus discharge current characteristics for lightning impulses detailed in section 6.3.3; and c) the residual voltage for switching impulses (Ups) specified in section 6.3.4.
Surge arresters are classified by Qt according to Table 1
Classes DC-A, DC-B and DC-C correspond to increased charge transfer capabilities The selection of the appropriate class shall be based on system requirements
The nominal discharge current shall be selected from the values of Table 2
General 1 7
Type tests shall be carried out as given in Table 3
Type tests do not require repetition unless there is a design change that affects performance; in that case, only the relevant tests must be redone.
1 Insulation withstand tests on the arrester housing 6.2
2 Residual voltage tests 6.3 a) Steep current impulse residual voltage test 6.3.2 b) Lightning impulse residual voltage test 6.3.3 c) Switching impulse residual voltage test 6.3.4
The article discusses nine environmental tests for surge arresters, including: a) a weather aging test specifically for polymer-housed surge arresters; b) an accelerated weathering test applicable to both polymer and cast resin-housed surge arresters; and c) a temperature cycling test combined with a salt-mist test designed for porcelain and cast resin-housed arresters.
1 0 Shock and vibration test (if applicable) 6.1 1
When conducting tests on multiple samples, the specific number of samples and their conditions are outlined in the respective clauses Arresters that vary solely in mounting methods or supporting structure arrangements, yet share the same components and similar construction leading to identical performance characteristics, including heat dissipation and internal atmosphere, will be regarded as having the same design.
The housing of an arrester serves as its external insulating component, ensuring adequate creepage distance while safeguarding internal elements from environmental factors Composed of multiple parts, the housing offers both mechanical strength and protection against external conditions.
A direct lightning impulse test according to Annex B may be performed optionally.
Insulation withstand tests on the arrester housing 1 8
General 1 8
These tests demonstrate the voltage withstand capability of the external insulation of the arrester housing
The tests shall be performed in the conditions and with the test voltages specified in IEC 60060-1 :201 0
The outside surface of insulating parts shall be carefully cleaned
To conduct these tests, the internal components must be either removed or made inoperative Alternatively, these parts can be substituted with an equivalent grading arrangement to ensure consistent voltage distribution along the arrester axis.
In design scenarios where external insulation is directly molded onto metal-oxide resistors or an insulating substrate, testing can be conducted with the housing molded onto an appropriate insulating material.
Tests will be conducted on the longest arrester housing If this does not reflect the highest specific voltage stress per unit length, further tests will be carried out on the housing unit with the highest specific voltage stress.
Ambient air conditions during tests 1 9
The voltage to be applied during a withstand test is determined by multiplying the specified withstand voltage by the correction factor taking into account density and humidity (see IEC 60060-1 :201 0)
Humidity correction shall not be applied for wet tests.
Wet test procedure 1 9
The external insulation of outdoor arresters shall be subjected to wet withstand tests under the test procedure given in IEC 60060-1 :201 0.
Lightning impulse voltage test 1 9
The arrester shall be subjected to a standard lightning impulse voltage dry test according to IEC 60060-1 :201 0
Fifteen consecutive impulses at the specified test voltage will be applied for both polarities The arrester passes the test if there are no internal disruptive discharges and if the external disruptive discharges do not exceed two in each series.
1 5 impulses The test voltage shall be equal to the lightning impulse protection level of the arrester multiplied by 1 ,47
If the dry arcing distance is greater than the test voltage divided by 500 kV/m, this test is not required.
DC voltage withstand test 1 9
The housings of arresters for outdoor use shall be tested in wet conditions, and housings of arresters for indoor use, in dry conditions
Housings shall withstand a DC voltage equal to the lightning impulse protection for a duration of 1 min.
Residual voltage tests 1 9
General 1 9
The residual voltage type test aims to gather data for determining the maximum residual voltage, as detailed in section 3.27 This involves calculating the ratio of voltages at specific impulse currents to the voltage level assessed during routine tests The voltage in these tests may be either the reference voltage or the residual voltage, measured at an appropriate lightning impulse current ranging from 0.1 to 2 times the nominal discharge current, based on the manufacturer's selected routine test procedure.
The manufacturer's data must specify and publish the maximum residual voltage for lightning impulse current used in routine tests To determine the maximum residual voltages for all specified currents and wave shapes, the measured residual voltages of the test sample are multiplied by the ratio of the declared maximum residual voltage at the routine test current to the measured residual voltage for the sample at that same current.
Residual voltage tests must be conducted on the same three samples of complete arresters or metal-oxide resistors Adequate time should be allowed between discharges for the samples to cool to near ambient temperature In the case of multi-column arresters, testing can be limited to a single column, with residual voltages measured based on the total currents of the complete arrester divided by the number of columns, while adhering to current sharing requirements.
Steep current impulse residual voltage test
Each of the three samples must undergo testing with a steep current impulse that has a peak value equal to the nominal discharge current of the arrester, within a tolerance of ± 5% The virtual front time for this impulse should range from 0.9 µs to 1.1 µs The time to half value on the tail is not critical and can have any tolerance It is essential to record the peak value and the impulse shape of the voltage across the samples, making necessary corrections for any inductive effects from the voltage measuring circuit, as well as the geometry of both the test sample and the test circuit.
To determine the need for an inductive correction, a steep current impulse is applied to a metal block matching the dimensions of the tested metal-oxide resistor samples The peak voltage across the metal block is recorded If this peak voltage is less than 2% of the peak voltage of the metal-oxide resistors, no correction is necessary If it falls between 2% and 20%, the impulse shape of the metal block voltage is subtracted from the metal-oxide resistor voltages, and the peak values of the corrected voltages are noted However, if the peak voltage exceeds 20%, improvements to the test circuit and voltage measuring circuit are required.
The steep current impulse residual voltage of the arrester is the sample impulse voltage (corrected if necessary) with highest peak value multiplied by the scale factor
To ensure consistent current wave shapes during measurements, it is effective to connect both the test sample and the metal block in series within the test circuit By simply swapping their positions relative to one another, one can measure the voltage drop across either the metal block or the test sample.
Lightning impulse residual voltage test
The test shall be applied to three samples Each sample shall be submitted to three lightning current impulses in accordance with 3.23 with peak values of approximately 50 %, 1 00 % and
The arrester is designed to handle 200% of the nominal discharge current, with a virtual front time ranging from 7 µs to 9 µs, while the half-value time can vary without critical implications Residual voltages are established according to section 3.27, and the maximum residual voltages are plotted on a curve that relates residual voltage to discharge current The residual voltage corresponding to the nominal discharge current on this curve is defined as the lightning impulse protection level of the arrester.
Switching impulse residual voltage test
A switching current impulse, chosen from the values in Table 4, will be applied to each of the three samples with a tolerance of ± 5% The maximum voltage recorded among these three samples is identified as the switching impulse residual voltage of the arrester for the corresponding current.
Table 4 – Peak currents for switching impulse residual voltage test
Charge transfer test
General
Before the tests the residual voltage and reference voltage of each test sample shall be measured for evaluation purposes
The charge transfer test will be conducted on three new samples of complete arresters or metal-oxide resistors, which have not undergone any prior testing except for the specified evaluation During these tests, the non-linear metal-oxide resistors may be exposed to open air at a still air temperature of 20 °C ± 15 K.
Each charge transfer test will include 18 discharge operations organized into six groups of three impulses The intervals between discharge operations will range from 50 to 60 seconds, allowing the sample to cool to near ambient temperature between each group of three.
After the charge transfer test and once the sample has cooled to near ambient temperature, it is essential to repeat the residual voltage and reference voltage tests These tests should be compared with the initial values obtained prior to the charge transfer test, ensuring that any changes do not exceed 5%.
Visual examination of the test samples after the test shall reveal no evidence of puncture, flashover, cracking or other significant damage of the metal-oxide resistors.
Charge transfer test requirements
The test evaluates the charge transfer capability (Qt) of the surge arrester by applying current impulses to the test sample, with specific parameters outlined in Table 5.
Table 5 – Parameters for the charge transfer test
Virtual duration of peak of current impulse T d ms
Longer virtual duration of peak of current impulse may be selected after agreement between manufacturer and user
The test must be conducted using a test generator that produces long-duration rectangular current impulses, meeting specific criteria Notably, the virtual duration of the peak current impulse (Td) should range from 1 ms to 5 ms.
(see Figure 1 ); b) the virtual total duration ( Tt ) of the current impulse shall not exceed 1 50 % of the virtual duration of the peak (see Figure 1 )
The charge on each tested sample shall lie between 90 % and 1 1 0 % of the specified value for the first impulse and between 1 00 % and 1 1 0 % of this value for the following impulses
The article requires that records of the voltage and current waveforms for both the initial and final impulses be presented on a consistent time base for each sample Additionally, it is essential to include the peak current value, charge, and energy for each impulse.
Operating duty tests
General
The tests simulate service conditions by applying a predetermined number of specified impulses to the arrester, along with energization from a power supply at a specified DC voltage The voltage measurement must maintain an accuracy of ± 1%, and during the operating duty tests, the DC voltage should not vary from the specified values by more than ± 1%.
The main requirement to pass these tests is that the arrester is able to cool down during the
DC voltage application, i.e thermal runaway does not occur
Thermal runaway in an arrester occurs when the continuous power loss surpasses the thermal dissipation capacity of its housing and connections, resulting in a progressive rise in the temperature of the metal-oxide resistor elements, ultimately leading to failure.
A thermally stable arrester is characterized by a decrease in the temperature of its metal-oxide resistor elements over time after experiencing a temperature rise due to operational duties This stability is observed when the arrester is energized at a specified continuous operating voltage and under defined ambient conditions The testing process includes a specific sequence to evaluate this performance.
This sequence is given in Table 7
The test shall be made on three samples of complete arresters at an ambient temperature of
The key parameter for successfully passing the operating duty test of metal-oxide resistors is the power loss of the resistor To ensure accurate testing, the operating duty test must be conducted on new metal-oxide resistors using an elevated test voltage, \( U_c^* \), which replicates the power losses experienced at the continuous operating voltage of aged resistors This elevated test voltage is determined through the accelerated aging procedure outlined in section 6.5.2.
The DC test voltage for testing arresters must match the continuous operating voltage, as specified in section 3.1.2 This voltage is then adjusted in accordance with section 6.5.2 to determine the elevated test voltage, denoted as \$U_c^*\$.
NOTE The established preheat temperature of 60 °C ± 3 K specified in Table 7 is a weighted average that covers the influence of ambient temperature and solar radiation.
Accelerated ageing procedure
This test procedure aims to establish the voltage value \$U_c^*\$ for the operating duty test, as illustrated in Figure 2, enabling the assessment of new metal-oxide resistors.
DC test voltage shall be applied
NOTE This test does not consider polarity change during service
Three metal-oxide resistor samples will be subjected to continuous operating voltage (Uc) for 1,000 hours, with the surface temperature maintained at 115 °C ± 4 K throughout the testing period.
All materials, whether solid or liquid, that come into direct contact with metal-oxide resistors must be included in the ageing test, maintaining the same design as that used in the complete arrester.
In the process of accelerated aging, the metal-oxide resistor must be placed in the same medium used in the arrester This procedure involves testing individual metal-oxide resistors within a closed chamber, which should have a volume at least twice that of the resistor itself Additionally, the density of the medium inside the chamber must be equal to or greater than that of the medium in the arrester.
6.5.2.3 Determination of elevated continuous operating voltages
The three test samples will be heated to 115 °C ± 4 K, and the power losses of the metal-oxide resistor, denoted as P1 ct, will be measured at a voltage of Uc 1 hour to 2 hours after voltage application Subsequent measurements of the power losses will occur every 100 hours following the initial measurement of P1 ct After 1,000 to 1,100 hours of aging under the same conditions, the power losses, referred to as P2 ct, will be recorded Any accidental de-energizing of the test samples, not exceeding a total of 24 hours during the test period, is allowed and will not be included in the test duration The final measurement will take place after a minimum of 100 hours of continuous energizing, with all measurements conducted within the specified temperature range of ± 1 K.
The minimum power losses value among those measured at least every 1 00 h time span shall be called P3ct This is summarized in Figure 2
Figure 2 – Power losses of the metal-oxide resistor at elevated temperatures versus time
If P2ct is equal to, or less than, 1 1 0 % P3ct , then the test according to 6.5.3 shall be performed on new metal oxide resistors:
• if P2ct is equal to, or less than, P1 ct , Uc is used without any modification;
If the power loss P2ct exceeds P1ct, the ratio P2ct / P1ct is calculated for each sample, with the highest ratio designated as Kct Power losses P1ct are measured at ambient temperature across three new metal-oxide resistors at voltage Uc Subsequently, the voltage is increased to ensure that the resulting power losses P2ct meet the specified relationship.
The highest of the three increased voltages obtained is represented by \$U_c^*\$ (Kct \$U_c\$) Alternatively, aged metal-oxide resistors can be utilized, provided there is an agreement between the user and the manufacturer.
If P2ct is greater than 1 1 0 % P3ct , and
• P2ctis lower than P1 ct then aged metal-oxide resistors shall be used for the following tests of 6.5.3 Uc is used without modification;
If the pressure P2ct is greater than or equal to P1ct, aged metal-oxide resistors must be utilized for the tests outlined in section 6.5.3 New metal-oxide resistors with a corrected value of \$U_c^*\$ may be employed, but this is contingent upon mutual agreement between the user and the manufacturer.
Metal-oxide resistors subjected to the above test during more than 1 000 h are considered as aged Table 6 summarizes these cases
Table 6 – Determination of elevated continuous operating voltage
Power losses measured Test samples for the operating duty test Test voltage for the operating duty test
P 2ct ≤ 1 ,1 × P 3ct and P 2ct ≤ P 1 ct New samples U c
P 2ct ≤ 1 ,1 × P 3ct and P 2ct > P 1 ct New samples 푈 c ∗
P 2ct > 1 ,1 × P 3ct and P 2ct < P 1 ct Aged samples U c
P 2ct > 1 ,1 × P 3ct and P 2ct ≥ P 1 ct Aged samples U c
New samples (alternatively after agreement between manufacturer and purchaser)
Where aged metal-oxide resistors are used in the operating duty test, the time delay between the ageing test and the operating duty test should be not more than 24 h
The measuring time shall be short enough to avoid increased power loss due to heating.
Operating duty test
The complete test sequence is given in Table 7
Table 7 – Test procedure of operating duty test
1 Initial measurement Residual voltage measurement at nominal discharge current and reference voltage measurement Time interval not specified
(see 6.5.3.2) Part I 4 groups of 5 impulses at I n 8/20 à s
Time interval not specified at ambient temperature Part II High current impulse 4/1 0 à s
Cooling to ambient temperature High current impulse 4/1 0 à s
3 Operating duty test Preheat to 60 °C ± 3 K
One impulse of the charge transfer test (see 6.4.2)
50 s to 60 s One impulse of the charge transfer test (see 6.4.2)
As short as possible, no longer than 1 00 ms Elevated continuous operating voltage, 30 min (see 6.5.2.3) Cooling to ambient temperature
4 Final measurement and examination Residual voltage measurement at nominal discharge current and reference voltage measurement Visual examination of test sample
In situations where generator performance is limited, it is permissible to conduct a total charge transfer involving two operations, with three operations completed within a two-minute timeframe This approach is justified as the operating duty test confirms the thermal stability of the surge arrester following energy absorption.
Before the operating duty test the reference voltage and residual voltage at nominal discharge current of each of the three test samples shall be determined at ambient temperature (see 6.3.3)
The test samples shall be suitably marked to ensure the application of the correct polarity in the following subclauses
The samples undergo a conditioning test involving 20 current impulses, as specified in section 6.5.3.1, with a peak value matching the nominal discharge current of the arrester These impulses are delivered in four groups of five, with a 50 to 60-second interval between each impulse Additionally, the intervals between groups are designed to allow the samples to cool down to near ambient temperature.
The second phase of conditioning involves applying two high current impulses, Ihc, with a 4/1 0 à s duration and peak values chosen from Table 8 It is essential that the measured peak value of these current impulses falls within 90% to 110% of the specified peak value.
The conditioning shall be carried out on the test samples in open air at a still air temperature of 20 °C ± 1 5 K
Table 8 – Values for high current impulses
After this conditioning the test samples shall be stored for future use in the operating duty test
After conditioning, the arrester shall be heated up to 60 °C ± 3 K The test shall be carried out at the ambient temperature of 20 °C ± 1 5 K
In cases of elevated pollution levels or unusual service conditions, a higher temperature may be utilized for testing, provided that both the manufacturer and purchaser reach an agreement on this adjustment.
The arrester must undergo two charge transfer operations with a rated charge Qt, as outlined in Table 5 for the specific arrester class Additionally, there should be a time interval of 50 to 60 seconds between the impulses.
After the second charge transfer operation, the arrester shall be disconnected from the impulse generator and connected to the DC source as soon as possible but not later than
Thirty minutes after the impulse, the elevated continuous operating voltage \( U_c^* \), established through the accelerated aging procedure outlined in section 6.5.2, must be applied to assess thermal stability or the risk of thermal runaway.
To accurately simulate real system conditions, the second charge transfer operation must be conducted while the sample is energized at Uc* A 100 ms limit is allowed due to practical constraints within the test circuit.
All charge transfer operations will be documented through oscillographic records of the voltage and current across the test sample The charge and energy dissipated during these operations will be calculated from the voltage and current oscillograms, with the results recorded in the type test report.
Metal-oxide resistor temperature or DC current or power loss shall be monitored during the
DC voltage application to prove thermal stability or thermal run-away
After the complete test sequence, the reference voltage and residual voltage at nominal discharge current for each of the three arresters are measured once the test sample has cooled to near ambient temperature.
6.5.3.4 Evaluation of thermal stability in the operating duty tests
The samples subjected to the operating duty tests are considered to be thermally stable if the
DC current or power loss or metal-oxide resistor temperature steadily decreases during the last 1 5 min of Uc voltage application in the procedure shown in Table 7
The stability of DC current is significantly affected by the applied voltage and ambient temperature changes Consequently, determining the thermal stability of the arrester may not be straightforward after the Uc * voltage application In such instances, it is essential to prolong the Uc * voltage application until a consistent decrease in current, power loss, or temperature is clearly observed If no increasing trend in current, power dissipation, or temperature is detected within 3 hours of voltage application, the sample is deemed stable.
The arrester has passed the test if all the following conditions are met:
• the thermal stability is achieved;
• the change in residual voltage measured before and after the test is not more than 5 %;
• the change in reference voltage measured before and after the test is not more than 1 0 %;
• visual examination of the test samples after the test reveals no evidence of puncture, flashover or cracking of the non-linear metal-oxide resistors.
Short-circuit tests
General
Tests are conducted to ensure that the failure of an arrester does not lead to the violent shattering of its housing and that any open flames self-extinguish within a specified timeframe Each type of arrester is evaluated under varying short-circuit current values Additionally, if the arrester features an alternative to a conventional pressure relief device, this configuration will also be incorporated into the testing process.
With respect to the short-circuit current performance, it is important to distinguish between two designs of surge arresters
• “Design A” arresters have a design in which a gas channel runs along the entire length of the arrester unit
• “Design B” arresters are of a design with no enclosed volume of gas
"Design A" arresters are typically housed in porcelain or polymer, featuring a composite hollow insulator These devices are designed with either pressure-relief mechanisms or prefabricated weak points in the composite housing that activate at a predetermined pressure, effectively reducing internal pressure.
"Design B" arresters are solid devices that lack pressure relief mechanisms and do not contain any gas volume When the metal-oxide resistors fail, an internal arc forms, leading to significant evaporation and potential burning of the housing or internal components The effectiveness of these arresters in short-circuit situations relies on their capacity to manage the cracking or tearing of the housing caused by the arc, preventing violent shattering.
Preparation of the test samples
Depending on the type of arrester and test voltage, different requirements apply with regard to the number of test samples and initiation of short-circuit current
The tests shall be carried out on complete arresters for the highest voltage rating
Samples must be prepared to conduct the necessary short-circuit current using a fuse wire This fuse wire should be in direct contact with the metal-oxide resistors and positioned as close as possible to the gas channel, effectively short-circuiting the entire internal active component The specific location of the fuse wire during the test must be documented in the test report.
The preparation of test samples does not differentiate between polymer and porcelain housings Arresters designed with polymeric sheds, when applied to a primary housing made of porcelain or other brittle insulators, will be regarded and tested as porcelain-housed arresters.
The selection of fuse wire material and size is crucial, ensuring that it melts within 2 ms during high and reduced short-circuit current tests However, for low short-circuit current tests, there are no time constraints for melting.
The test samples shall be filled with the surrounding medium (gas) used in the arresters
No special preparation is necessary Surge arrester without modification shall be used
Complete arresters must undergo electrical pre-failure testing using a DC or AC overvoltage applied to their terminals It is essential that no physical modifications are made to the arresters between the pre-failure process and the subsequent short-circuit current test.
Pre-failing overvoltage can lead to the failure of the arrester within approximately 5 minutes, with a possible variation of ± 3 minutes Metal-oxide resistors are deemed to have failed when the voltage across the arrester drops below a certain threshold.
1 0 % of the originally applied voltage The pre-failing current shall not exceed 30 A
The time between pre-failure and the rated short-circuit current test shall not exceed 1 5 min
The pre-failure shall be achieved by either applying a voltage source or a current source to the sample
For voltage source method: The initial current should typically be in the range 5 mA/cm 2 to
The pre-failing short-circuit current generally ranges from 1 A to 30 A, and the voltage source typically does not require adjustment after the initial setting However, minor adjustments may be necessary to ensure the metal-oxide resistors fail within the specified time range.
For the current source method, a typical current density of approximately 1.5 mA/cm², with a variation of ±50%, can lead to the failure of metal-oxide resistors within a specified time frame The pre-failing short-circuit current should generally range between 10 A and 30 A Once set, the current source usually does not require adjustments, although minor tweaks may be needed to ensure the timely failure of the metal-oxide resistors.
Testing of porcelain housed arresters
6.6.3.1 Mounting of the test sample
The mounting arrangement is shown in Figure 3 The distance to the ground from the insulating platform and the conductors shall be as indicated in this figure
Figure 3 – Short-circuit test setup for porcelain-housed arresters
(all leads and venting systems in the same plane)
The bottom end fitting of the test sample must be mounted on a test base that matches the height of a surrounding circular or square enclosure This test base can be made of insulating material or conducting material, provided its surface dimensions are smaller than those of the arrester's bottom end fitting Both the test base and enclosure should be placed on an insulating platform The arcing distance between the top end cap and any metallic object, excluding the arrester's base, must be at least 1.6 times the height of the sample arrester, with a minimum distance of 0.9 m Additionally, the enclosure should be constructed from non-metallic material and symmetrically positioned relative to the test sample's axis.
The enclosure must have a length of 40 cm ± 10 cm, with its diameter (or side length for a square enclosure) being at least 1.8 m or as specified by the formula below It is essential that the enclosure remains stationary and closed throughout the testing process.
D = 1 ,2 × (2 × h + Darr) where h is the height of tested arrester unit;
Darr is the diameter of tested arrester unit
Test samples shall be mounted vertically unless otherwise agreed between the manufacturer and the user
The mounting of the arrester during the short-circuit test and, more specifically, the routing of the conductors shall represent the most unfavourable condition in service
Flexible over a length of at least 0,2 m
The routing depicted in Figure 3 is the least favorable during the initial testing phase prior to venting, particularly for surge arresters equipped with pressure relief devices When the sample is positioned with the venting ports directed towards the test source, it may lead to the external arc being drawn closer to the arrester housing This proximity can result in thermal shock, causing significant chipping and shattering of porcelain weather sheds compared to other venting port orientations.
6.6.3.2 High current and reduced current short-circuit tests
Four samples will be tested at currents determined by the rated short-circuit current and reduced currents as specified in Table 9 These samples will be prepared in accordance with section 6.6.2 and mounted following the guidelines in section 6.6.3.1.
The tests shall be carried out with DC currents
Arresters must undergo testing at the rated short-circuit current, the reduced short-circuit current, and the low short-circuit current as specified in Table 9 The average value of the test current should meet or exceed the rated short-circuit current while remaining within the acceptable tolerance limits for both the reduced and low short-circuit currents.
Tests will be conducted in a test circuit using an open circuit test voltage ranging from 77% to 107% of the continuous voltage of the test sample The total duration of the test current flowing through the circuit will be as specified in Table 9 For surge arresters equipped with pressure relief devices, the low short-circuit current will continue until venting takes place.
Table 9 – Required currents for short-circuit tests of porcelain housed arresters
Short circuit currents can be selected based on mutual agreement between the manufacturer and the user, with a typical value of 600 ± 33 A Additionally, if the performance during a short circuit test with AC current is shown to be equivalent to that of a DC current test, AC current testing may be conducted instead, provided there is agreement between both parties.
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 current waveform
The solid shorting link will be removed after verifying the prospective current, and the arrester samples will be tested using identical circuit parameters Throughout all short-circuit tests, the short-circuit current will be documented against time.
6.6.3.3 Low-current short-circuit test
The test must utilize a circuit capable of generating a current of 600 A ± 200 A through the test sample, measured approximately 0.1 seconds after the initiation of the short circuit current The current should continue for a minimum of 1 second after the fuse wire melts or until venting occurs The sample preparation should follow the guidelines in section 6.6.2, and mounting should adhere to section 6.6.3.1 For handling an arrester that fails to vent, refer to section 6.6.5.
Testing of polymer housed arresters
For a base-mounted arrester, the mounting arrangement is shown in Figure 4 The distance to the ground of the insulating platform and the conductors shall be as indicated in Figure 4
For non-base-mounted arresters, the test sample must be installed using hardware that reflects typical real-world service conditions The mounting bracket will be treated as an integral component of the arrester base during testing, and the manufacturer's installation guidelines should be followed.
For base-mounted arresters, the bottom end fitting must be installed on a test base that matches the height of a surrounding circular or square enclosure, which can be made of insulating material or conducting material if its dimensions are smaller than those of the arrester fitting Both the test base and enclosure should rest on an insulating platform Non-base-mounted arresters follow the same bottom requirements, with an arcing distance of at least 60% of the arrester's height, but no less than 0.9 m, between the top end cap and any metallic object, excluding the base The enclosure must be non-metallic, symmetrically positioned relative to the test sample, with a height of 40 cm ± 10 cm and a diameter or side length of at least 1.8 m or as defined by the relevant formula It is crucial that the enclosure remains closed and stationary throughout the test.
D = 1 ,2 ×(2 × h + Darr) where h is the height of tested arrester unit;
Darr is the diameter of tested arrester unit
The arresters shall be mounted according to Figure 4 in the vertical position unless otherwise agreed between the manufacturer and the purchaser
Figure 4 – Short circuit test setup for polymer housed arresters
(all leads and venting systems in the same plane)
6.6.4.2 High-current, reduced current and low current short-circuit test
The tests shall be carried out with DC currents
Arresters must undergo testing at the rated short-circuit current, reduced short-circuit current, and low short-circuit current as specified in Table 1 The average value of the test current should meet or exceed the rated short-circuit current while remaining within the acceptable tolerance limits for both the reduced and low short-circuit currents.
Table 1 0 – Required currents for short-circuit tests
Short circuit currents can be selected based on mutual agreement between the manufacturer and the user, with a typical value of 600 ± 33 A Additionally, if the performance during a short circuit test with AC current is shown to be equivalent to that of a DC current test, AC current testing may be conducted instead, provided there is agreement between both parties.
All arresters shall be prepared according to 6.6.2 and mounted according to 6.6.4.1
Tests will be conducted in a test circuit using an open circuit test voltage ranging from 77% to 107% of the continuous voltage of the test sample The total duration of the test current flowing through the circuit will be as specified in Table 10 For surge arresters equipped with pressure relief devices, the low short-circuit current will continue until venting occurs.
To measure the prospective current, conduct a test with the arrester short-circuited or replaced by a solid link of negligible impedance, ensuring the test duration is limited to the minimum time necessary for peak and current waveform measurement After verifying the prospective current, remove the shorting link and test the arrester sample(s) using the same circuit parameters Additionally, record the short-circuit current over time during all short-circuit tests.
Pre-failed arresters can accumulate significant arc resistance, restricting the current flow through the arrester To ensure accurate testing, it is advisable to conduct short-circuit tests promptly after the pre-failure, ideally before the test samples have cooled.
To ensure optimal performance of pre-failed arresters, it is crucial to verify that the arrester exhibits sufficiently low impedance before subjecting it to short-circuit current This can be achieved by reapplying the prefailing circuit for a maximum of 2 seconds prior to the short-circuit test current, as illustrated in Figure 5 Additionally, the short-circuit current of the pre-applied circuit may be increased up to 300 A, with the maximum duration \( t_{rpf} \) being contingent upon the magnitude of the current.
Irpf, shall not exceed the following value: trpf≤ Qrpf / Irpf where trpf is the re-prefailing time, in s;
Qrpf is the re-prefailing charge = 60 As;
Irpf is the re-prefailing current, in A
Figure 5 – Example of a test circuit for re-applying pre-failing immediately before applying the short-circuit test current
Evaluation of test results
The test is deemed successful if it meets three key criteria: first, there should be no violent shattering; second, while structural failure of the sample is allowed, it must ensure that no parts of the test sample are found outside the enclosure.
– fragments, less than 60 g each, of ceramic material such as metal-oxide or porcelain, – pressure relief vent covers and diaphragms,
The soft components of polymeric materials demonstrate the ability to self-extinguish open flames within 2 minutes after testing Additionally, any ejected parts, whether inside or outside the enclosure, also extinguish flames within the same timeframe.
If the arrester does not show visible venting after testing, it is important to exercise caution, as the housing may still be pressurized This precaution is necessary for all test current levels, but is especially critical for low current short-circuit tests.
Internal partial discharge tests
This test shall be carried out at AC voltage The power frequency voltage ( Utac , RMS value) to be applied shall be Uc of the sample divided by √2
The test voltage must be raised to 125% of Utac and maintained for a duration of 2 to 10 seconds, before being reduced to 105% of Utac At this voltage, the partial discharge level should be assessed in accordance with IEC 60270, ensuring that the internal partial discharge measurement does not exceed 10 pC.
This test shall be performed on one sample of a complete arrester The test sample may be shielded against external partial discharges.
Bending moment test
General
The test applies to polymer-housed arresters with and without enclosed gas volume and to porcelain-housed arresters
The complete testing procedure for various arrester designs is outlined below and depicted in Figure A.1 For porcelain-housed arresters, the specified SLL is 40% of the SSL, while for polymer-housed arresters, the SLL is lower than the SSL, as shown in Figure 9.
This test evaluates the arrester's capacity to endure the manufacturer's specified bending loads Typically, arresters are not engineered to handle torsional loads; however, if such loads are anticipated, a specialized test may be required, contingent upon an agreement between the manufacturer and the user The testing must be conducted on fully assembled arresters.
Test on porcelain and cast-resin housed arresters
To conduct the test, one end of the sample must be securely attached to a stable mounting surface of the testing apparatus, while a load is applied to the opposite free end to generate the necessary bending moment at the fixed end.
The load direction must be perpendicular to the arrester's longitudinal axis If the arrester exhibits non-axi-symmetrical bending strength, the manufacturer must disclose this information, and the load should be applied at an angle that maximizes the bending moment on the weakest section of the arrester.
6.8.2.2 Test procedure to verify the Specified Short-Term Load (SSL)
Three samples shall be tested Prior to the tests, each test sample shall be subjected to a leakage check (see of 7.1 d) and an internal partial discharge test (see 7.1 c)
The bending load on each sample must be gradually increased to the specified SSL, with a tolerance of +5% to -0%, over a period of 30 to 90 seconds Once the test load is achieved, it should be sustained for 60 to 90 seconds Continuous measurements of force and deflection are required throughout the test duration After the load is released smoothly, the residual deflection must be recorded, with measurements taken between 1 to 10 minutes post-release.
The arrester shall have passed the test if:
• there is no visible mechanical damage,
• the residual deflection is less than or equal to the greater of 3 mm or 1 0 % of maximum deflection during the test,
• the test samples pass the leakage test in accordance with 6.9,
• the internal partial discharge level of the test samples does not exceed the value specified in 6.7.
Test on polymer-housed arresters with and without enclosed gas
A test in two steps shall be performed one after the other on three samples
Prior to the bending-moment test, each sample shall be subjected to the following electrical tests made in the following sequence:
• power losses measured at Uc and at an ambient temperature of 20 °C ± 1 5 K;
• internal partial discharge test according to 6.7;
• residual voltage test at the nominal discharge current;
• leakage tests in accordance with 6.9 for arresters with enclosed gas volume and separate sealing system
To conduct the test, one end of the sample must be securely attached to a stable mounting surface of the testing apparatus, while a load is applied to the opposite free end to generate the necessary bending moment at the fixed end.
The load direction must be perpendicular to the arrester's longitudinal axis If the arrester exhibits non-axi-symmetrical bending strength, the manufacturer must provide details about this asymmetry Consequently, the load should be applied at an angle that maximizes the bending moment on the weakest section of the arrester.
Tolerance on specified loads shall be + 5 % / –0 % The test is undertaken in two steps:
• Step 1 1 : two samples shall be submitted to the short-term load test as described in 6.8.3.2.2;
• Step 1 2: the third sample shall be submitted to the mechanical preconditioning as per 6.8.3.2.3;
• Step 2: all three samples shall be submitted to the water immersion test as per 6.8.3.2.4 6.8.3.2.2 Short-term load test
Two samples will undergo testing at the specified short-term load (SSL) The bending load will be gradually increased to the SSL within a timeframe of 30 to 90 seconds Once the test load is achieved, it will be maintained for a duration of 60 to 90 seconds Throughout the test, force and deflection will be continuously measured from start to finish, followed by a smooth release of the load The residual deflection will be assessed 1 to 10 minutes after the load is released.
The maximum deflection during the test and any residual deflection shall be recorded
This step constitutes a part of the test procedure and shall be performed on one of the test samples
Terminal torque preconditioning shall be achieved by applying the arrester terminal torque as specified by the manufacturer to the test sample for duration of 30 s
Thermo mechanical preconditioning is achieved by submitting the arrester to the specified continuous load (SLL) in four directions and in thermal variations as described in Figure 6 and Figure 7
If, in particular applications, other loads are dominant, the relevant loads should be applied instead The total test time and temperature cycle should remain unchanged
If the sample has no cylindrical symmetry, the load direction shall be chosen in such a manner as to achieve the maximum mechanical stress
Te m pe ra tu re
The thermal variations involve two 48-hour cycles of heating and cooling, as illustrated in Figure 7 Each hot and cold period must be sustained for a minimum of 16 hours, and the preconditioning process will take place in air.
The applied static mechanical load shall be equal to SLL defined by the manufacturer Its direction changes every 24 h as defined in Figure 7
The preconditioning may be interrupted for maintenance for a maximum aggregate duration of
4 h and restarted after interruption The cycle then remains valid
Any permanent deformation measured from the initial no-load position shall be reported
Figure 7 – Example of the arrangement for the thermo-mechanical preconditioning and directions of the cantilever load
The test samples must be submerged in a vessel containing boiling deionised water mixed with 1 kg/m³ of NaCl for a duration of 42 hours To prevent the evaporation of water during the boiling process, the vessel should be covered with a lid.
NOTE The characteristics of the water described above are those measured at the beginning of the test
This temperature (boiling water) may be reduced to (80 ± 5) °C (with a minimum duration of
By mutual agreement between the user and the manufacturer, the sealing material's ability to withstand boiling temperatures for 42 hours can be contested This initial duration of 52 hours may be extended to a maximum of 168 hours (one week) upon consent from both parties.
At the end of this step, the arrester shall remain in the vessel until the water cools to
The holding temperature of (50 ± 5) °C is crucial for delaying verification tests until after the water immersion test, as illustrated in Figure 8 The arrester must be kept at this temperature until the verification tests are conducted in accordance with section 6.8.3.3 Samples should cool to ambient temperature in still air, with a maximum cooling time of 2 hours Verification tests must be completed within 8 hours following the cooling period.
After removing the sample from the water it may be washed with tap water
After the test, the tests as per 6.8.3.1 shall be repeated
The arrester has successfully passed the test if the following is demonstrated
The force-deflection curve maintains a positive slope up to the SSL value, with minor dips not exceeding 5% of the SSL magnitude Digital measuring equipment must have a sampling rate of at least 10 samples per second, and the cut-off frequency should be no less than 5 Hz.
Maximum deflection during step 1 and any residual deflection after the test shall be reported but do not count as pass criteria
• for arresters with enclosed gas volume and separate sealing system, the samples pass the leakage test in accordance with 6.9;
The increase in watt losses, measured at Uc and within an ambient temperature variation of no more than 3 K from the initial measurements, does not exceed the greater of the specified limits.
20 mW/kV of Uc (measured at Uc ) or 20 %;
• the internal partial discharge measured at 1 05 % Uc does not exceed 1 0 pC;
Definition of mechanical loads
The definition of mechanical loads is shown in Figure 9
Te m pe ra tu re ( °C )
Time as long as necessary Cooling
Figure 9 – Definition of mechanical loads (base load = SSL)
Seal leak rate test
General
This test verifies the gas and water tightness of the entire system, specifically for arresters equipped with seals and related components that are crucial for preserving a controlled atmosphere within the housing This includes arresters that feature an enclosed gas volume and a distinct sealing mechanism.
The test shall be performed on one complete arrester unit The internal parts may be omitted
If the arrester contains units with differences in their sealing system, the test shall be performed on one unit each, representing each different sealing system.
Definition of seal leak rate
The seal leak rate indicates the amount of gas that escapes through the housing seals over time when there is a pressure difference of at least 70 kPa In cases where the sealing system's efficiency varies with the pressure gradient direction, the most unfavorable scenario should be taken into account.
Guaranteed mean value of breaking load 1 20 %
Seal leak rate = ∆푝 ∆푡 1 × 푉 at | 푝 1 − 푝 2 | ≥ 70 kPa and at a temperature of + 20 °C ± 1 5 K, where:
The change in internal gas pressure of the arrester housing, denoted as \$\Delta p_1\$, is calculated by the difference between the internal gas pressure at the end time \$t_2\$ and the start time \$t_1\$ Here, \$p_1(t)\$ represents the internal gas pressure in pascals (Pa) as a function of time, while \$p_2\$ indicates the external gas pressure surrounding the arrester, also measured in pascals (Pa) The time interval is defined from \$t_1\$ (start time) to \$t_2\$ (end time), measured in seconds.
V is the internal gas volume of the arrester, in m 3
Sample preparation
The test sample shall be new and clean.
Test procedure
The manufacturer may use any sensitive method suitable for the measurement of the specified seal leak rate, and other pressure differences with some correction suitable for the arresters
NOTE Some test procedures are specified in IEC 60068-2-1 7.
Test evaluation
The maximum seal leak rate (see 6.9.2) shall be lower than:
6.1 0.1 Weather ageing test for polymer-housed surge arresters
This test shall be performed on surge arresters for outdoor use only It shall be performed on one surge arrester of highest Uc and minimum specific creepage distance
The test is conducted in a moisture-sealed, corrosion-proof chamber, utilizing a constant DC voltage equal to Uc under time-limited continuous salt fog conditions To ensure proper ventilation, an aperture not exceeding 80 cm² is provided for the natural evacuation of exhaust air, while a turbo sprayer or room humidifier with a consistent spraying capacity serves as the water atomizer.
The chamber will be filled with fog, avoiding direct spraying on the test specimen A solution of NaCl and deionized water will be used in the sprayer When the DC test circuit is loaded with a current of 250 mA on the high-voltage side, it will experience a maximum voltage drop of 5%.
The protection level shall be set at 1 A The test specimen shall be cleaned with deionized water before starting the test
The test specimen must be positioned vertically during testing, ensuring adequate clearance between the chamber's roof, walls, and the specimen to prevent electrical field interference Relevant data can be found in the manufacturer's installation instructions.
• NaCl content of water between 1 kg/m 3 to 1 0 kg/m 3
The manufacturer must specify the initial salt content of the water The water flow rate is measured in liters per hour per cubic meter of the test chamber, and water recirculation is prohibited.
Interruptions caused by flashovers are allowed during testing, and if multiple flashovers happen, the test voltage will be interrupted The application of salt fog must continue until the arrester is washed with tap water, with interruptions not exceeding 15 minutes The test will then resume with a lower salt content in the water, and if more flashovers occur, the process will be repeated It's important to note that interruption times do not count towards the total test duration.
The NaCl concentration in the water, along with the frequency of flashovers and the length of interruptions, must be documented Additionally, the count of overcurrent trip-outs should be noted and factored into the assessment of the test duration.
Within this salinity range, reduced salt levels can heighten test severity, while increased salt content raises the likelihood of flashover, complicating testing on larger diameter housings.
The test is regarded as passed, if:
• no tracking occurs (see IEC 61 1 09),
• erosion does not occur through the entire thickness of the external coating up to the next layer of material,
• sheds and housing are not punctured,
• the reference voltage measured before and after the test has not decreased by more than
• the partial discharge measurement performed before and after the test is satisfactory, i.e the partial discharge level does not exceed 1 0 pC according to 7.1 c)
6.1 0.2 Accelerated weathering test for polymer housed surge arresters and cast resin housed surge arresters
Three specimens of shed and housing materials shall be selected for this test Where there are markings on the items, they should be included as part of the specimen
The insulator housing shall be subjected to a 1 000 h UV light test using one of the following test methods
Markings on the housing, if any, shall be directly exposed to UV light a) xenon-arc methods: ISO 4892-1 and ISO 4892-2 using method A without dark periods:
• black-standard/black panel temperature of 65 °C;
• an irradiance of around 550 W/m 2 b) fluorescent UV Method: ISO 4892-1 and ISO 4892-3, using type I fluorescent UV lamp:
Tests without water shall not be employed
After the test, markings on shed or housing material shall still be legible; surface degradations such as cracks and blisters are not permitted
In situations where there is uncertainty about degradation, two surface roughness measurements must be conducted on each of the three specimens The crack depth, denoted as Rz according to ISO 4287, should be measured over a sampling length of at least 2.5 mm, and Rz must not exceed 0.1 mm.
NOTE ISO 3274 gives details of surface roughness measurement instruments
6.1 0.3 Temperature cycling test and salt mist test for porcelain and cast resin-housed arresters
Accelerated testing confirms that the sealing mechanism and exposed metal combinations of the arrester remain unaffected by environmental conditions These tests will be conducted on complete arrester units of varying lengths.
For arresters with an enclosed gas volume and a separate sealing system, the internal parts may be omitted
Arresters that vary solely in length, while sharing the same design, materials, and sealing systems, are classified as the same type of arrester.
Prior to the tests, a leakage check shall be made by any sensitive method adopted by the manufacturer
The tests specified below shall be performed on one sample in the sequence given
The test shall be performed according to test Nb of IEC 60068-2-1 4
The hot period must maintain a temperature between +40 °C and +70 °C, while the cold period should be at least 85 K lower than the hot period's temperature, with a minimum temperature of -50 °C.
• duration of each temperature level: 3 h;
The test shall be performed according to Clause 4 and 7.6 of IEC 60068-2-1 1 :1 981
• salt solution concentration: 5 % ± 1 % by weight;
After conducting the tests, a leakage check must be performed on each arrester as outlined in section 6.1 0.3.2 The arrester is considered to have passed the tests if it successfully meets the leakage check criteria specified in section 6.9.
The surge arrester installed on board rolling stock shall be able to withstand shock and vibration test as stated in IEC 61 373
7 Routine tests and acceptance tests
Routine tests
The manufacturer must conduct routine tests that include measuring the reference voltage (\$U_{ref}\$) at direct current within specified limits, performing a residual voltage test on complete arresters or metal-oxide resistor elements, and ensuring the residual voltage does not exceed manufacturer specifications Additionally, an internal partial discharge test must be conducted, along with a leakage check for sealed housing arresters using a method chosen by the manufacturer For multi-column arresters, a current distribution test is required on all parallel metal-oxide resistor groups, with the impulse current specified by the manufacturer and not exceeding set limits, while ensuring the current impulse has a virtual front time of at least 7 µs.