IEC 61000 4 25 Edition 1 1 2012 05 INTERNATIONAL STANDARD NORME INTERNATIONALE Electromagnetic compatibility (EMC) Part 4 25 Testing and measurement techniques – HEMP immunity test methods for equipme[.]
Introduction
The HEMP immunity test standard has been established for electrical and electronic equipment and systems, enabling manufacturers to qualify their products early in the design process This standard allows the use of existing IEC laboratory immunity tests that are already mandated for other EMC applications.
Immunity tests
HEMP immunity tests are categorized into two primary types: radiated immunity tests and conducted immunity tests In this context, "electronic equipment" refers to devices designed for specific functions, such as small computers or telephones.
Certain equipment, like computers linked to control boards for factory process monitoring, can be viewed as components of a larger system Typically, this electronic equipment is compact, measuring around 1 m x 1 m x 1 m or less Most testing on such small devices is anticipated to occur in laboratories utilizing current injection simulators and TEM cells.
In HEMP and EMC testing, the size of the system plays a crucial role, particularly for large equipment exceeding 1 meter in dimension, which necessitates the use of a substantial HEMP simulator Unlike other EMC tests, HEMP testing features several large early-time HEMP simulators, approximately 10 meters high, located globally These simulators can effectively replicate the pulsed electric and magnetic fields associated with early-time HEMP threats, allowing for the exposure of large systems to these conditions Additionally, they are instrumental in ensuring that equipment designed for HEMP resilience functions correctly when integrated into a complete system.
Immunity test levels
This standard outlines the electromagnetic disturbances that may occur at equipment ports due to high-altitude nuclear events These disturbances arise from the radiated and conducted High-altitude Electromagnetic Pulse (HEMP) environments, taking into account any protective measures in place Detailed descriptions of these electromagnetic disturbances can be found in IEC 61000-2-9.
IEC 61000-2-10 and IEC 61000-2-11 The rationale for the immunity test levels and threat reductions due to protection elements and probable flashovers are described in annex A.
Radiated disturbance tests
Radiated immunity test levels
The radiated immunity test levels described below involve only the early time radiated fields
Testing for intermediate-time and late-time HEMP fields is unnecessary Annex A provides details on selecting immunity test levels, while Table 1 lists the peak values of the early-time electric field, \$E_{\text{peak}}\$ for the chosen immunity test levels.
Table 1 – Radiated immunity test levels defined in the present standard
Immunity test level Test required for equipment and systems with the following protection a E-field peak value b
Concept 4 Intermediate value Intermediate value Concepts 2A, 2B, 3 Intermediate value Intermediate value Concepts 1A, 1B Special applications
X a The protection concepts are described in IEC 61000-5-3 b According to IEC 61000-2-11, table 2
Radiated immunity test specifications
In the simulator's test volume, the electric field resembles a quasi-plane wave characterized by a double exponential pulse time history when no object is present.
2,5/25 ns wave, i.e a unipolar wave with a 10 %-90 % rise time of 2,5 ns and a pulse width equal to 25 ns This waveform is given by the equation below
E peak is the peak value of the electric field in volts per meter
NOTE E peak is the immunity test level selected from table 1 t is the time in seconds.
The frequency-domain spectral magnitude for equation (1) is given by
= (2) where f is the frequency in hertz
For the waveform parameters given above, the frequency-domain spectral magnitude of equation (2) is shown in figure 1
Figure 1 – Frequency domain spectral magnitude between 100 kHz and 300 MHz.
Small radiated test facilities
Small test facilities are better equipped to achieve the required field specifications with tighter tolerances in parameter variations compared to large HEMP simulators These facilities are mainly designed for testing smaller equipment The tolerances for the early-time HEMP pulse waveform across the entire test volume of the small facility will be specified accordingly.
– The ratio of peak electric field to the peak magnetic field shall be equal to 377 Ω ± 50 Ω
– The rise time between 10 % and 90 % of the peak value shall be within the range of 2,0 ns and 2,5 ns
– The electric field shall be continuously increasing during the 10 % and 90 % rise time
– The pulse width (the time duration between points on the leading and trailing edges of the pulse at 50 % of E peak ) shall be within the range of 25 ns and 30 ns
– The magnitude of any pre-pulse on the electric field shall be equal to or less than 7 % of the magnitude of the peak field
– Electric field reflections from the terminator of the simulator shall be less than 10 %
The smoothed frequency spectrum of the electric field at the center of the test volume must not vary by more than ±3 dB from the theoretical spectrum defined by equation (2) within the bandwidth of 100 kHz to 300 MHz.
– At the time of the peak value of the simulated fields, other non-principal electromagnetic components shall be smaller than 10 % of the peak value of the simulated field
The peak electric field in the test volume must remain uniform, adhering to the criteria that it should fall within the range of \$E_{\text{peak}}\$ to \$E_{\text{peak}} + 6 \, \text{dB}\$.
To assess field tolerances, measurements of electric and magnetic fields must be conducted at the center and the eight corners of the test volume without the Equipment Under Test (EUT) present.
Large HEMP simulators
Large HEMP simulators are essential for testing extensive equipment and complete systems, offering a variety of rise times, pulse widths, and field amplitudes These simulators are categorized into two types based on their radiated field behavior: type I and type II Type I simulators typically deliver shorter rise times and pulse widths compared to type II simulators It is important to conduct a pre-test analysis for type II simulators, as they do not comply with the radiated immunity specifications outlined in section 5.4.2.
The response of electrical components to High-Altitude Electromagnetic Pulse (HEMP) is influenced by the pulse shape and the mechanisms of coupling and penetration In smaller systems, such as mobile phones, HEMP coupling primarily occurs through high-frequency aperture penetrations, making type I simulators with a larger high-frequency spectral content ideal for testing Conversely, in systems with longer external conductors, like HF radios, the HEMP response is mainly due to field coupling with the antenna, suggesting that type II simulators with slower rise times and longer pulse widths are more suitable for testing these systems.
Different systems respond uniquely to various components of the incident HEMP environment, highlighting the need for a pre-test analysis program for type II simulators This analysis is essential to understand how type II simulated fields interact with the system and to evaluate the effectiveness of these simulators in conducting immunity tests The test's adequacy will be validated by comparing the interaction and coupling results of the simulated fields with the theoretical pulse outlined in section 5.4.2.
For type I simulators, the peak electric field, denoted as \$E_{\text{peak}}\$ , must be selected from Table 1 based on the chosen immunity test level Tolerances for the early-time response should also be considered during testing.
HEMP pulse over the entire parallelepiped test volume of the simulator shall be as follows
– The ratio of peak electric field to the peak magnetic field shall be equal to 377 Ω ± 50 Ω
– The rise time between 10 % and 90 % of the peak value shall be 2,5 ns ± 0,5 ns
– The electric field shall be continuously increasing during the 10 % and 90 % rise time
– The pulse width (the time duration between points on the leading and trailing edges of the pulse at 50 % of E peak ) shall be within the range of 25 ns and 75 ns
– The magnitude of any pre-pulse on the electric field shall be equal to or less than 7 % of the magnitude of the peak field
– Electric field reflections from the terminator of the simulator shall be less than 10 %
The smoothed frequency spectrum of the electric field at the center of the test volume must not vary by more than ±10 dB from the theoretical spectrum defined by equation (2) within the bandwidth of 1 MHz to 200 MHz.
The peak electric field in the test volume must remain uniform, adhering to the criteria that it should fall within the range of \$E_{\text{peak}}\$ to \$E_{\text{peak}} + 6 \, \text{dB}\$.
To assess field tolerances, measurements of electric and magnetic fields must be conducted at the center and the eight corners of the test volume without the Equipment Under Test (EUT) present.
5.4.4.2 Large HEMP simulators − type II
A pre-test analysis is required for tests with type II simulators since these test facilities do not meet the radiated immunity specifications given in 5.4.2
The specifications of type II large simulators are the same as type I, except for rise time, pulse width, and frequency spectrum specification, which are as follows:
– The rise time between 10 % and 90 % of the peak value shall be within the range of 2 ns and 10 ns
– The pulse width (the time duration between points on the leading and trailing edges of the pulse at 50 % of E peak ) shall be within the range of 25 ns and 500 ns
The smoothed frequency spectrum of the electric field at the center of the test volume must not vary by more than ±10 dB from the theoretical spectrum defined by equation (2) within the bandwidth of 1 MHz to 100 MHz.
Frequency domain spectrum requirements
The HEMP simulator must meet specific requirements for its frequency domain spectrum, in addition to the transient field criteria The frequency spectrum is to be derived from a uniformly sampled transient waveform consisting of 4,096 samples, spanning from a start time of 0 to an end time of 2 ms A 2,048-point complex-valued frequency spectrum will be generated using either a fast Fourier transform (FFT) or a discrete Fourier transform (DFT), with a defined frequency sampling interval.
0,5 MHz, and a maximum frequency of 1,0 GHz b) The frequency domain spectrum shall be smoothed using a 5-point windowing average
The smoothed spectrum's magnitude must remain within the designated dB level of the specified waveform, as outlined in equation (2) and illustrated in figure 1, while being averaged over a 2 MHz window.
Most frequency spectra exhibit occasional nulls or "dropouts" that do not significantly impact the transient waveform's overall behavior To accommodate these nulls, the smoothed frequency domain spectrum for small and large simulators is required to remain within ±3 dB and ±10 dB, respectively This distinction in spectral limits arises from the smaller simulators' tighter tolerances and greater accuracy in simulating fields.
Conducted disturbance tests
Conducted immunity test levels
For the conducted disturbance, three types of conducted environments shall be considered
These correspond to each of the time regimes for HEMP (early, intermediate and late time)
The immunity test levels for three types of conducted environments are presented in tables 2, 3, and 4, which display common-mode test values Common-mode tests are mandatory for I/O and shielded cables, while both common-mode and differential-mode tests are necessary for power and telecom ports during the initial two time regimes.
Differential-mode immunity test levels match the common-mode values, as indicated in Table 5, which outlines additional tests that address the indirect effects of the late-time environment.
See annex A for a description of the immunity test levels as a function of required reliability and protection of the installed equipment
5.5.1.1 Early-time conducted immunity test levels
The early time conducted immunity test levels are listed in table 2 The first six levels utilise damped sinusoids waveforms to account for the ringing associated with interior building wiring
The application of immunity test levels for the protection concepts, confidence levels
Antenna cable ports can be activated through exposure to a simulated High-Altitude Electromagnetic Pulse (HEMP) during radiated immunity testing, or by applying a suitable conducted differential-mode surge, as outlined in annex B Table A.3 presents various cable ports related to this process.
Table 2 – Early time conducted immunity test levels
Waveform Basic standard Severity level in the basic standard
Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a 5/50 ns 5/50 ns 5/50 ns 25/500 ns 10/100 ns Fast transient
ISO 7137 ISO 7137 ISO 7137 ISO 7137 ISO 7137 ISO 7137 IEC 61000-4-4 IEC 61000-4-4 IEC 61000-4-4 This standard This standard This standard
See Annex D See Annex D See Annex D See Annex D See Annex D See Annex D
X EC10 EC11 ECX NOTE 1 Voltage and current levels shown in the table are for common mode values
NOTE 2 EC10 consists of four sublevels in addition to 25 kV: 1 kV, 4 kV , 8 kV and 16 kV
NOTE 3 For immunity test levels EC8 and EC9, it is sufficient to test with a single pulse
NOTE 4 EC11 consists of four sublevels in addition to 160 kV: 20 kV, 40 kV, 80 kV and 120 kV This immunity test level category is intended for testing equipment directly connected to long MV distribution power lines protected against lightning If lightning protection is not used, increase V oc to 1,6 MV and I sc to 4 000 A (see Annex A). a Each immunity test level consists of at least two frequencies: 1 MHz and 10 MHz or 10 MHz and 30 MHz The damping parameter Q of the damped oscillatory wave test, as defined by equation (D.1) in IEC 61000-2-10, ranges from 5 to 20
A Waveform Basic standard Severity level in the basic standard
Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a Damped sinusoids a 5/50 ns 5/50 ns 5/50 ns 25/500 ns 10/100 ns Fast transient
IEC 61000-4-18 IEC 61000-4-18 IEC 61000-4-18 IEC 61000-4-18 IEC 61000-4-18 IEC 61000-4-18 IEC 61000-4-4 IEC 61000-4-4 IEC 61000-4-4 This standard This standard This standard
NOTE 1 Voltage and current levels shown in the table are for common mode values
NOTE 2 EC10 consists of four sublevels in addition to 25 kV: 1 kV, 4 kV, 8 kV and 16 kV
NOTE 3 For immunity test levels EC8 and EC9, it is sufficient to test with a single pulse
NOTE 4 EC11 consists of four sublevels in addition to 160 kV: 20 kV, 40 kV, 80 kV and 120 kV This immunity test level category is intended for testing equipment directly connected to long MV distribution power lines protected against lightning If lightning protection is not used, increase V oc to 1,6 MV and I sc to 4 000 A (see Annex A) a Each immunity test level consists of at least three frequencies: 3 MHz, 10 MHz and 30 MHz The damping parameter Q of the damped oscillatory wave test, as defined by equation (D.1) in IEC 61000-2-10:1998, ranges from 5 to 20
5.5.1.2 Intermediate-time conducted immunity test levels
Table 3 presents the intermediate time immunity test levels conducted by HEMP The IC3 level is applied for protection concepts 1A and 2A, which lack lightning protection on the low voltage a.c power circuit The justification for this immunity test level is detailed in Annex A.
IC2 and IC1 levels are lower than IC3, as each test must encompass the specified level along with the two preceding lower levels, according to the test procedure outlined in clause 9 Additionally, if lightning protection is implemented, intermediate time HEMP tests become unnecessary, since the surge protective devices (SPDs) utilized for lightning protection are effective against the slower surges indicated in table 3.
Table 3 – Intermediate time HEMP conducted immunity test levels
Time waveform Basic standard Severity level in the basic standard
NOTE Voltage and current levels shown in the table are for common mode values For differential mode, use the values shown for common mode in the table
5.5.1.3 Late-time conducted immunity test levels
The late-time HEMP conducted disturbance is a concern for telecommunications equipment, equipment directly connected to MV distribution power lines, and HV transmission power lines
Low voltage (LV) power circuits are largely unaffected by quasi-dc disturbances due to their short lengths and the attenuation from distribution transformers While the ideal time waveform is a unipolar 1/50 s pulse, simulating this waveform can be challenging, especially at higher currents Therefore, a trapezoidal pulse is utilized for immunity testing, as it is easier to implement Conducted environment immunity test levels for late-time High-altitude Electromagnetic Pulse (HEMP) are detailed in Table 4.
2 The ITU is the International Telecommunications Union
Table 4 – Conducted environment immunity test levels for late-time HEMP
Time waveform Basic standard Application
Unidirectional 60 s trapezoidal pulse This standard Typical telecom port with lines of 3 km or less
Unidirectional 60 s trapezoidal pulse This standard Telecom port for long lines up to 10 km
Unidirectional 60 s trapezoidal pulse This standard Equipment directly connected to MV primary distribution power circuits a
Unidirectional 60 s trapezoidal pulse This standard Equipment directly connected to long HV transmission power lines a
This standard Voltage and current immunity test levels defined by the user
The detailed waveform specifications can be found in Annex C The applicability is contingent upon the presence of a d.c path to earth at both ends of the line, and guidance on selecting the appropriate immunity test levels is provided in Annex A.
Low voltage power circuits are susceptible to the indirect impacts of late-time High-Altitude Electromagnetic Pulse (HEMP) disturbances on power distribution and transmission lines Table 5 outlines the tests for immunity against harmonic distortion and voltage dips that are suitable for low-voltage alternating current (a.c.) power ports.
Table 5 – Late time HEMP conducted environment effects tests for low-voltage a.c power ports
Immunity test level Effects Test specification Basic standard Severity level in the basic standard
LCH1 Severe harmonic distortion 2 nd harmonic – 5 % of V r
LCV1 Voltage variations 60 % of V r dip for 10 periods IEC 61000-4-11 Test level 40 % of V r
NOTE V r is the rated a.c input voltage.
Conducted immunity test specifications
The standard identifies various IEC EMC tests that fulfill HEMP test requirements, aiming to reduce the need for additional generators and testing facilities The test specifications align with existing standards, as detailed in table 6.
A coupling/de-coupling network similar to that used to conduct tests in IEC 61000-4-4,
IEC 61000-4-5 and IEC 61000-4-12 18 shall be used for EC1 through EC11 and IC1 through
IC4 tests require verification of the network's dielectric strength to ensure it is adequate for early-time HEMP conducted immunity tests Specifically, for EC11 early-time HEMP disturbances, the network must be designed to endure voltage pulses of up to 200 kV Detailed instrumentation and measurement guidance for these specialized tests can be found in IEC 61000-4-33.
Table 6 – Conducted HEMP immunity test specifications
Conducted test Reference document for the test specifications Source impedance
Burst repetition rate: 2,5 kHz Burst duration: 10 ms
Single unipolar pulse 25/500 ns wave IEC 61000-4-33 is applicable
Single unipolar pulse 10/100 ns wave IEC 61000-4-33 is applicable
40 ± 10 % Range: per standard ITU-T test
Trapezoidal wave generator IEC 61000-4-33 is applicable Late-time
Current injection generator IEC 61000-4-33 is applicable Late-time
Radiated field tests
Radiated field generator
The radiated field generator shall be either a small radiated field test facility that meets the specification requirements in 5.4.3, or a large HEMP simulator that meets the specification requirements in 5.4.4.
Instrumentation
The measurement method utilizes a fibre optic transmission link to measure and transmit signals to a data processing system without interfering with the surrounding electromagnetic (EM) field This system is designed to be intrinsically insensitive to electromagnetic radiation from the simulator The instrumentation and measurement techniques outlined in IEC 61000-4-33 are relevant for the radiated field tests specified in this standard The measurement system serves three main purposes: providing reference field measurements, synchronizing the simulated High-Altitude Electromagnetic Pulse (HEMP) with the operational modes of the system under test as needed, and delivering current and voltage measurements for the Equipment Under Test (EUT) as required by the user.
The required overall measurement system accuracy shall should be within ±3,0 dB over a frequency range of f min to f max where f min = 0,025/(pulse width) and f max =1,25/(pulse rise time)
The frequency range required for the measurement system is between 50 kHz and 500 MHz, meaning that the minimum frequency does not need to fall below 50 kHz, and the maximum frequency should not exceed 500 MHz Additionally, the overall instantaneous dynamic range of the measurement system must be at least 40 dB.
It is recommended that the measurement system have the following characteristics
– The data transmission system should have a minimum 3dB bandwidth of 50 kHz to 1GHz
– The digitizer or oscilloscope should have a 500 MHz minimum bandwidth and a minimum sampling rate of 2 gigasamples per second with a minimum data resolution of 8 bits
– The electric and magnetic field sensors should have a minimum 3 dB bandwidth of 50 kHz to 1 GHz
– The current sensors should have a minimum 3dB bandwidth of 50 kHz to 200 MHz
The reference field measurement will include three orthogonal components of both electric and magnetic fields, allowing for the evaluation of the electric to magnetic field ratio and the identification of spurious electromagnetic field components Additionally, users have the option to request other field measurements within the test volume.
If the user requires voltage data, the measurement system shall be carefully designed to provide accurate voltage measurements in the presence of strong electromagnetic fields.
Conducted disturbance tests
Test generator
The test generators used for conducted disturbance immunity tests align with the basic standards outlined in table 6 The immunity test levels EC10, EC11, and LC1 – LC4 are based on this standard, with the specifications for the test generators detailed below.
The characteristics and performance of the EC10 fast transient generator including the coupling device are as follows:
– open circuit voltage range: 1 kV – 10 % to 25 kV + 10 %
– the generator shall be capable of operating under short circuit conditions
Characteristics for operation under 50 Ω load condition:
– maximum energy: 6 J/pulse at 16 kV into a 50 Ω load
– rise time (10 % to 90 %) of the pulse: 25 ns ± 30 %
– dynamic source impedance ( see note): 50 Ω ± 15 Ω
– relationship to power supply: asynchronous
NOTE The source impedance may be verified by the measurement of the peak values of the output impulse voltage at no load and 50 Ω load conditions respectively (ratio 2:1)
The characteristics and performance of the EC11 fast transient generator including the coupling device are as follows:
– open circuit voltage range: 20 kV –10 % to 160 kV + 10 %
– the generator shall be capable of operating under short circuit conditions
Characteristics for operation under 50 Ω load condition:
– maximum energy: 50 J/pulse at 160 kV into a 50 Ω load
– rise time (10 % to 90 %) of the pulse: 10 ns ± 30 %
– dynamic source impedance ( see note): 50 Ω ± 15 Ω
– relationship to power supply: asynchronous
NOTE The source impedance may be verified by the measurement of the peak values of the output impulse voltage at no load and 50 Ω load conditions respectively (ratio 2:1)
The characteristics and performance of the LC1 and LC2 slow pulse generator including the coupling device are as follows:
– open circuit voltage waveshape: square wave
– trapezoidal voltage droop for a 100 Ω load: 10 %
– open circuit voltage range: 50 V – 10 % to 500 V + 10 %
– voltage rise time (10 % to 90 %) for a 100 Ω load: 1s ± 0,5 s
– voltage pulse duration (50 % value) for a 100 Ω load: 60 s ± 0,5 s
NOTE See Annex C for additional waveform details
A current injection generator is ideal for testing power system components, as the load impedance at low frequencies, typically a few hertz, varies from a few ohms to tens of ohms for transformer windings and inductors connected to earth The LC3 and LC4 slow pulse generators exhibit specific characteristics and performance metrics suitable for these applications.
– open circuit voltage waveshape: square wave
– trapezoidal current droop for a 0,1 Ω load: 50 %
– current rise time (10 % to 90 %) for a 0,1 Ω load: 1s ± 0,5 s
NOTE See annex C for additional waveform details.
Instrumentation
The test instrumentation for conducted disturbance immunity tests must align with the basic standards outlined in table 6 The overall measurement system accuracy required for the specified levels is ±3.0 dB across a frequency range defined by \$f_{min} = \frac{0.025}{\text{pulse width}}\$ and \$f_{max} = \frac{1.25}{\text{pulse rise time}}\$ Additionally, for the special tests specified in this standard, the appropriate instrumentation and measurement techniques must be utilized.
The IEC 61000-4-33 standard specifies that the overall measurement system accuracy must be within ± 3.0 dB across a frequency range defined by \$f_{min} = \frac{0.025}{\text{pulse width}}\$ and \$f_{max} = \frac{1.25}{\text{pulse rise time}}\$ The maximum frequency range required is from 50 kHz to 500 MHz, meaning \$f_{min}\$ should not be less than 50 kHz and \$f_{max}\$ should not exceed 500 MHz Additionally, the measurement system must have an instantaneous dynamic range of at least a specified minimum.
40 dB For immunity test levels EC9 to EC11, high voltage probes will be required to monitor the voltages
Radiated disturbance test
The test volume of a simulator is determined by its physical dimensions and the properties of its radiating structure, such as the antenna It is defined as the space where the incident electromagnetic fields achieve or surpass the necessary strength and uniformity standards.
In a simulated HEMP test, sections 5.4.3 and 5.4.4 highlight that if the object being tested is excessively large compared to the test volume, the induced response may differ from that of an incident plane wave illumination, leading to questionable test results.
To achieve accurate simulation results, it is essential to minimize the interaction between the EUT and the simulator by positioning the object under test at a sufficient distance from the simulator's radiating or wave guiding elements Specifically, for a bounded wave (parallel-plate) simulator, the object should be placed at least 0.3 times its overall transverse dimension away from the parallel plates.
If the EUT is to be tested while resting on a ground plane, it shall be located no closer than
The EUT can be positioned closer to free-field simulators, such as vertical or horizontal radiating dipole antennas, as the interaction between the EUT and the simulator structure is minimal compared to that of a parallel plate simulator, which requires a distance of 0.6 times its transverse dimension to the upper parallel plate.
The Equipment Under Test (EUT) is defined by its finite volume, determined by its maximum height, width, and length, which must fit within the specified simulator test volume If short external conductors associated with the EUT can be realistically illuminated by the simulator, they will also be included in the EUT's volume calculation For free-field testing, where the EUT is not on a ground plane, it should be positioned on a dielectric stand within the simulator, as outlined in clauses 8.3.2.1 and 8.3.2.2.
Conducted disturbance test
The test setup requirements for HEMP conducted disturbance immunity testing align with those for other IEC EMC tests, allowing for testing to be completed as a standalone requirement or as part of other IEC EMC tests For laboratory HEMP conducted disturbance immunity tests not referenced to other IEC EMC tests, the Equipment Under Test (EUT) must be positioned on a dielectric stand at a height of 0.1 m ± 0.01 m above the ground plane For table-top equipment, the EUT should be placed on a dielectric stand at a height of 0.8 m ± 0.08 m Additionally, a ground connection must be established between the ground plane and the EUT per the manufacturer's specifications, with a minimum distance of 0.5 m maintained between the EUT and other conducting surfaces.
The test equipment and instrumentation required for EMC tests by other IEC-approved standards, as referenced in table 6, can be used for HEMP conducted immunity tests
However, for special immunity test levels, such as severity level X in a referenced standard, special equipment with higher peak pulse voltage capabilities may be required For late-time
HEMP conducted immunity tests, instrumentation must should be capable of recording the injected pulse and equipment or system response up to 60 s
Tests for conducted and radiated disturbance immunity may be performed separately There are no requirements for testing both types of stresses simultaneously
In a radiated test, if the entire system, including all short external conductors, can be realistically illuminated, early-time conducted tests on those cables may be unnecessary Additionally, conducted tests for antenna ports might not be required if the antenna is oriented for maximum response during simulated HEMP stress testing However, it is essential to conduct immunity tests on all ports connected to power, telecom, or other long lines.
HEMP immunity tests must follow a detailed test plan outlining the equipment to be tested, the required immunity levels and waveforms, climatic conditions, key operational modes, and the criteria for passing It is crucial that the ambient environment of the testing facility does not affect the results During testing, equipment performance should be closely monitored as per clause 9 If the equipment interacts with other systems, efforts should be made to transmit the same or simulated data to ensure accurate performance evaluation during the test.
If the EUT fails to meet the test requirements and diagnostic measurements have been taken within the system or equipment, it is essential to remove the probes and cables before retesting This step ensures that any added instrumentation does not contribute to the test failure Additionally, the test report must explicitly document all external cables connected to the system.
EUT, whether they are part of the equipment or are part of a measurement system
The EUT must undergo testing in all major operational modes outlined in the test plan Conducted immunity tests will utilize both positive and negative waveforms, while radiated immunity tests will require only one polarity of the waveform.
Laboratory tests shall be conducted with the ambient environmental conditions identified in 8.1
On-site tests are inappropriate for immunity acceptance testing; however, they can be utilized to verify the immunity of installed equipment and the overall system While the ambient conditions outlined in section 8.1 are preferred for these tests, they are not mandatory.
Climatic conditions
The required HEMP testing shall be carried out in standard climatic conditions in accordance with IEC 60068-1 (1988):
– atmospheric pressure: 86 kPa to 106 kPa
When equipment is designed or specified for specific climatic conditions, it is essential to consider other ranges of these conditions, especially for outdoor testing The climatic conditions must be accurately measured and documented in the test report.
Immunity test level and test exposures
Testing exposures below the voltage protection level of Surge Protective Devices (SPDs) is crucial, as well as conducting tests at sufficiently low voltage levels to prevent arcing within the system, which can lead to potential damage.
Each immunity test level will include three specific test amplitudes, beginning two levels below the designated immunity test level, which is expected to be lower than the voltage protection level offered by the SPD and the arcing threshold The test should incorporate the immunity test level from the table, along with 50% and 25% of that level Testing will commence at the lowest amplitude, ensuring it remains below the voltage protection level provided by the SPD and the arcing threshold.
EC11 exceptions include a primary level and additional sublevels If lower levels must be below the voltage protection level, a lower starting test amplitude should be defined Each test pulse must utilize the same waveform as the specified immunity test level.
For radiated immunity testing, it is essential to specify an immunity test level as outlined in Table 1 Each orientation and major operational mode of the test object must undergo at least two test exposures at three different test amplitudes, totaling six exposures.
Immunity test levels for each time regime must be specified, as outlined in tables 2, 3, 4, and 5 These tests, which include both common mode and differential mode excitation with positive and negative polarity waveforms, are essential for power and telecom ports Differential mode tests should match the amplitude of common mode tests, although they are not required for I/O and shielded cables A minimum of two test exposures is necessary at each of the six test amplitudes, comprising three positive and three negative pulses, leading to a total of 12 exposures for each major operational mode of the test object.
Radiated disturbance test procedure
Test parameter measurements
The climate parameters defined in 8.1 shall be measured by the test operator and documented
The test facility's characteristics, which include measurements of electromagnetic field waveforms within the test volume in the absence of the Equipment Under Test (EUT), must be provided to the test operator Additionally, this information should encompass an evaluation confirming compliance with the field uniformity and waveform characteristics requirements outlined in section 5.4.3.
To ensure consistency in the electric field measurements, it is essential to record the electric field outside the test volume for each pulse of field illumination, confirming that the generator's amplitude remains uniform across all pulses.
Radiated test procedure
A small radiated test facility is suitable for testing equipment, but it is essential to conduct immunity tests on all cable ports While a small system can be evaluated in a large HEMP simulator and may satisfy the conducted immunity standards for several cable ports, long lines, such as a.c power and telecommunication lines, cannot be effectively tested in any facility.
HEMP simulator Consequently, conducted immunity tests are always required for these ports
The large HEMP simulator is ideal for conducting system-level tests involving multiple pieces of equipment operating in unison However, this standard does not mandate the use of such a simulator for system-level testing.
Immunity tests are conducted at a designated immunity test level, which includes exposures at that level and the two immediately lower levels If only one lower level is defined, only that level will be utilized In cases where the lowest immunity test level is specified, only that exposure is required Each exposure level must undergo a minimum of two pulses of field illumination.
Each immunity test is conducted at a designated immunity test level, involving exposures at three different amplitudes: the full specified level, as well as 50% and 25% of that level For each of these three exposure levels, a minimum of two pulses of field illumination must be executed.
The fundamental method employed in this process involves evaluating equipment and small systems within a laboratory testing environment, which may include facilities like a TEM cell, anechoic chamber, or open area test site.
The Equipment Under Test (EUT) must be positioned on a dielectric stand at a height of 0.1 m ± 0.01 m above the ground plane within the test volume, ensuring that all equipment cables are utilized in a manner consistent with normal operation A ground connection between the ground plane and the EUT should be established according to the manufacturer's specifications, with careful control and documentation of cable lengths and positions It is essential to orient the cabling to minimize coupling with the electric and magnetic field components present in the test facility Additionally, separate conducted immunity tests should be conducted to address cable coupling The EUT should be rotated to expose all sides, typically six, to the incident pulsed fields, although practical limitations may restrict the number of rotations.
If the method of monitoring involves measurements within the EUT, the probes and cables involved shall be carefully positioned, so as to minimise adverse effects on the measurements
In particular, fibre optic cables without metal material are recommended for such measurements
A pre-test analysis is essential for type II simulators, as they do not comply with the radiated immunity specifications outlined in section 5.4.2 To ensure the test's adequacy, it is necessary to compare the interaction and coupling results of the simulated fields with the theoretical pulse defined in section 5.4.2.
The basic approach used in this procedure is to test a large piece of equipment (or a self- contained system) to the early-time radiated HEMP environment in a large HEMP simulator
Simulators with substantial test volumes, reaching up to 1,000 m³, allow for simultaneous exposure of a system and its external and interconnecting cables This testing method offers the significant advantage of evaluating interconnected equipment under realistic operational conditions Additionally, it can potentially eliminate the necessity for individual equipment level tests, thereby reducing the overall conducted immunity testing required.
However, all ports connected to power, telecom, or other long lines must have conducted immunity tests
To conduct the procedure, the Equipment Under Test (EUT) must be positioned on a dielectric stand within the simulator, ensuring that external system cables are arranged to optimize the induced currents at each Point of Entry (PoE) Verification of these currents is essential, as they should be compared against the specified conducted immunity test levels for each PoE If the induced currents during radiated field testing surpass the conducted disturbance immunity requirements—characterized by higher peak values, shorter rise times, and broader pulse widths—and the system remains operational, the conducted immunity test for that PoE becomes unnecessary Additionally, if required, radiated tests can be conducted at elevated field levels to enhance the induced currents at each PoE.
This procedure is effective only if the system can function properly during exposure If the required levels of induced current are not met, a conducted immunity test must be conducted.
The EUT must be positioned on a dielectric stand at a height of 0.1 m ± 0.01 m above the ground plane within the designated test volume For table-top equipment or systems, this placement is essential for accurate testing.
EUT shall be placed on a dielectric stand at a height of 0,8 m ± 0,08 m above the ground plane within the test volume A ground connection shall be made between the ground plane and the
The Equipment Under Test (EUT) should be positioned according to the manufacturer's guidelines, ensuring that all six faces are exposed to the incident fields Additionally, any short external cables within the test volume must be oriented to achieve maximum response at each cable port during at least one orientation of the EUT.
Conducted disturbance immunity test procedure
The test procedure outlined in the basic standard referenced in table 6 must be followed for conducted immunity tests, with specific exceptions noted It is essential to conduct tests on all types of conductive lines, including the longitudinal metallic components of fiber optic cables, that are connected to the system and equipment This encompasses power, communication, signal, control, and earthing lines.
For shielded cables bonded to a shielded enclosure at both ends, the cable shield must be driven with the necessary stress In cases where the cable is unshielded or the shield is not electrically connected to the equipment shield, the internal wires should be directly driven with the required stress, ensuring that the bulk current on these wires complies with the drive specifications.
Immunity tests are conducted at a designated immunity test level, which includes exposures at that level and the two immediately lower levels If only one lower level is defined, only that level will be utilized In cases where the lowest immunity test level is specified, exposure at that level alone is sufficient Each exposure level requires a minimum of two positive pulses and two negative pulses to ensure accurate testing.
Each immunity test is conducted at a designated level and includes exposures at three different levels: the specified immunity test level, 50%, and 25% of that level For each exposure level, a minimum of two positive pulses and two negative pulses must be executed.
Test execution
Execution of the radiated immunity test
The radiated immunity test will be conducted according to a test plan that verifies the performance of the Equipment Under Test (EUT), as specified in the product standard or, if unavailable, by the relevant technical specification.
The Equipment Under Test (EUT) must be in normal operating condition A test configuration matrix will be created, detailing the EUT's operational configurations, key functional states, and orientations concerning wave propagation The test plan will outline specific requirements for each test configuration.
– test exposure levels: the selected immunity test level, plus the next two lower levels;
– number of exposures at each level (at least two are required);
– description of positions of the cables and measurements to be made;
– polarity and angle of incidence of the simulated fields;
– details of the test set-up, whenever it is different from that specified in clause 7;
Execution of the conducted immunity test
The immunity test will be conducted according to a test plan that verifies the performance of the Equipment Under Test (EUT), as specified in the product standard or, if unavailable, by the technical specification.
The Equipment Under Test (EUT) must be in normal operating condition A test configuration matrix will be created, outlining the EUT's operational configurations and key functional states The conducted immunity test plan will detail the specifications for each test configuration.
– type of tests to be performed (early-time, intermediate-time, and/or late-time);
– test modes (both common and differential modes are normally required for early and intermediate time tests on cables connected to a.c and d.c power ports and telecom ports);
– common mode test levels: the selected immunity test level, plus the next two lower levels;
– differential mode test levels: equal to the common mode test levels;
– polarity of test voltage/current waveforms (both polarities are mandatory);
– number of required applications of each exposure level (at least two);
– EUT cable (conductor) ports to be tested;
– sequence of application of the test pulse to the EUT ports, one after the other, or two cables connected to more than one port, etc.;
– test set-up, whenever different from that specified in clause 7;
NOTE Differential mode tests are recommended for power and telecom cable ports
The test plan must be agreed upon by both the manufacturer and the testing laboratory or user Testing can be conducted without probes if there is a concern that these probes may alter or interfere with the results.
9 Test results and test reports
The test report must detail the Equipment Under Test (EUT), including test conditions, operational modes, and measured results for each exposure For radiated immunity tests, it should also present the measured reference field and information about the High-Altitude Electromagnetic Pulse (HEMP) field generator, including calibration results, field mapping within the test volume, and the time domain electric field along with its frequency spectrum Additionally, the report should assess any adverse effects caused by fluctuations in the electric field's frequency spectrum compared to the theoretical spectrum.
The performance of the EUT can be categorized into several classifications: a) normal performance within specified limits; b) temporary degradation or loss of function that is self-recoverable; c) temporary degradation or loss of function requiring operator intervention or a system reset; d) non-recoverable degradation or loss of function due to data loss or equipment damage; and e) degradation that poses a potential safety risk, such as fire.
Acceptance tests must be detailed in the specific product standard, including the test program and result interpretation Product committees have the authority to adjust the test result categories as needed based on circumstances.
Rationale for the immunity test levels
The immunity tests outlined in this standard are based on a thorough evaluation of equipment locations and suitable test levels Test levels are determined by the protection offered at the equipment site, influenced by installation conditions such as building structure and lightning protection, as specified in IEC 61000-5-3 Additionally, the required reliability of the equipment plays a crucial role in this selection process The specific levels and waveforms for HEMP radiated and conducted stresses are detailed in IEC 61000-2-11, aligning with the protection concepts established in IEC 61000-5-3, which include very high (99%), high (90%), and nominal levels.
(50 %) probability levels in IEC 61000-2-11 have been used to determine stresses for very high, high, and nominal equipment reliability requirements, respectively
To streamline immunity testing, we have merged the criteria of multiple protection concepts, resulting in the elimination of certain test levels Additionally, we have adjusted some stress tests to reflect potential reductions caused by flashovers or the lightning protection offered by medium voltage surge arresters and low voltage surge protective devices.
HEMP test results indicate that steep-front short-duration transients can cause flashover at approximately twice the level of the 1,2/50 às wave specified in IEC 61000-4-5 For instance, if an insulator flashes over at 110 kV for the 1,2/50 às wave, it would do so at around 220 kV for HEMP-induced transients The voltage protection level on a medium voltage line equipped with a metal-oxide varistor (MOV) lightning arrester with short leads is roughly three times higher than that for the 1,2/50 às wave For example, a 9 kV MOV surge arrester has a voltage protection level of about 40 kV for a 20 kA 1,2/50 às wave, meaning that HEMP disturbances would be limited to approximately 120 kV However, this protection level of 120 kV is significantly lower than the insulator's flashover level of 220 kV.
The voltage protection level on a low voltage (LV) line equipped with a surge protective device (SPD) featuring short leads is approximately three times higher for a 1.2/50 µs wave This increased protection level for steep-front surges is largely attributed to the lead inductance, which is around 1 µH/m To ensure minimal lead inductance during SPD installation, refer to the guidelines in [2] A correctly installed SPD can achieve a voltage protection level that is about four times the operating voltage for a 1.2/50 µs wave, capable of handling surge currents of several kiloamperes, as noted in [2].
According to IEC 61000-2-11, levels R1, R4, and R7 represent specific values, while levels R2, R3, R5, and R6 serve as intermediate levels Additionally, level RX is designated for a specific electromagnetic disturbance level tailored for particular applications, such as accommodating higher levels due to field enhancement near metallic structures to ensure a greater hardening margin.
IEC 61000-2-11, (5 V/m) and (50 V/m), would not be significant as immunity test levels, and these low levels have not been used in this standard
3 The figures in brackets refer to clause A.3
The radiated immunity test levels, outlined in table A.1, are derived from the protection concepts specified in IEC 61000-5-3 Concept 4 ensures a minimum attenuation of 40 dB through a shielded enclosure with modest RF shielding Meanwhile, concepts 2 and 3 achieve 20 dB of attenuation using structures such as concrete buildings with rebar, bonded metal buildings, or buried structures.
Table A.1 – Radiated immunity test levels
Immunity test level Test required for equipment and systems with the following protection Protection concept a
40 dB attenuation Intermediate value Intermediate value
20 dB attenuation Intermediate value Intermediate value
No field attenuation Special applications
Radiated tests for intermediate and late-time HEMP are not required, since these environments will only couple significantly to very long lines, and conducted environment tests are more appropriate
The test levels for the three time regimes of the conducted disturbance are as follows:
− EC levels are related to early time HEMP conducted environments;
− IC levels pertain to intermediate time HEMP conducted environments;
− LC levels are for the late time HEMP conducted environments
A.2.1 Early-time immunity test levels
A.2.1.1 The conducted early time HEMP environment
The classification of conducted common-mode early-time HEMP environments, as presented in
IEC 61000-2-11, are shown in table A.2
Table A.2 – Conducted common-mode early time HEMP environments
1B and 2B 20 kV/50 A 60 kV/150 A 160 kV/400 A 2,5 kV/50 A
1A and 2A 200 kV/500 A 600 kV/1,5 kA 1,6 MV/4,0 kA 25 kV/500 A
The waveform for the buried line is characterized by a unidirectional pulse of 25/500 ns and a source impedance of 50 Ω In the conducted environment, damped sinusoids with a frequency of 10 MHz are utilized, capable of handling voltages up to 4 kV from elevated lines Transients from elevated lines that are equal to or exceed this threshold are also considered.
8 kV are 10/100 ns waves in IEC 61000-2-11 However, the higher values above 8 kV in table A.3 are for cases where LV insulation breakdown or SPD responses are appropriate
These cases are all represented by 5/50 ns waves
High voltage transients from concepts 1 and 2 in table A2 will not affect low voltage equipment within buildings due to the insulation strength of low voltage circuits and the influence of lightning protection devices It is assumed that the lightning protection is nominal, meaning that the surge protective device (SPD) or surge arrester provides less than optimal voltage protection For instance, a metal oxide varistor (MOV) SPD with lead lengths of 0.1 m in a 50% probability conducted environment for concept 2B, which involves a 0.5 kA 10 x 100 ns wave as per IEC 61000-2-11, results in a specific protection voltage level.
Larger surges result in increased protection voltage levels due to lead inductance, which leads to attenuation at various points within a building Steep-front surges experience significant attenuation while traveling through power lines, causing reductions in both amplitude and steepness of the surge front.
For a.c power ports connected to LV power circuits without lightning protection, the peak voltage is approximately given by two times the severe lightning level of 8 kV specified in