IEC 61000-2-10:2021 pdf free download – Electromagnetic compatibility (EMC)
5.1 Introductory remarks
The electromagnetic field generated by a high-altitude nuclear explosion described inIEC 61000-2-9 can induce currents and voltages in all metallic structures.These currents andvoltages propagating in conductors represent the conducted environment. This means that theconducted environment is a secondary phenomenon, a consequence of the radiated field alone.
All metallic structures (i.e., wires, conductors, pipes,ducts,etc.) will be affected by the HEMP.The conducted environment is important because it can direct the HEMP energy to sensitiveelectronics through signal, power, and grounding connections. It should be noted that there aretwo distinct categories of conductors: external and internal conductors (with regard to a buildingor any other enciosure). While this can seem simplistic, this separation is critical in terms of theinformation to be provided in this document.
The difference between these two types of conductors is explained by electromagnetic topology.ln general,external conductors are those which are located outside of a building and arecompletely exposed to the full HEMP environment.This category includes power，metalliccommunication lines,antenna cables, and water and gas pipes (if metallic).For the purposesof this document,the conductors can be elevated above the ground or buried in the earth.Internal conductors are those which are located in a partially or completely shielded buildingwhere the HEMP fields have been reduced by the building. This is a much more complexsituation, because the HEMP field waveforms will be significantly altered by the building shield,and the coupling to internal wires and cables is consequently very difficult to calculate,althoughsome measured data are available from simulated HEMP tests.
ln this document the external conducted common mode environments are calculated usingsimplified conductor geometries and the specified HEMPenvironments for the early,intermediate,and late-time waveforms.These conducted external environments are intendedto be used to evaluate the performance of protection devices outside of a building, and becauseof variations in telecom and power systems, the effects of transformers and telephone spliceboxes are not considered here.This process results in approximate, but well-defined waveformsthat are needed to test protective elements on external conductors in a standardized manner.For the internal conductors, a procedure is defined to estimate the conducted environmentsappropriate for equipment testing.For unshielded multiconductor wires, it is assumed that theline-to-ground currents are equal to the common-mode current.
5.2Early-time HEMP external conducted environment
For the early-time HEMP, the high-amplitude electric field couples efficiently to antennas andto any exposed lines such as power and telephone lines. The antenna coupling mechanism isextremely variable and dependent on the details of the antenna design. In many cases, it isadvisable to perform continuous wave (CW) testing of an antenna and to “combine” theresponse function of the antenna with the incident HEMP environment using a convolutiontechnique.However，simple formulae have been provided to compute the response of thinantennas (see 5.5). For long lines, it is possible to perform a comprehensive set of commonmode calculations that are reliable and depend only upon a few parameters.These parametersinclude conductor length, exposure situation (above ground or buried), and the surface groundconductivity (for depths between 0 m and 5 m). In addition, because the HEMP coupling isdependent on angle of elevation and polarization (see Figure 1), it is possible to statisticallyexamine the probability of producing particular levels of current.