Lightning And Surge Protection For Cable Networks And Antennas For TV (Part 2)

Lightning And Surge Protection For Cable Networks And Antennas For TV PART 2 - (photo by dipolnet.com)


Continued from part one:
Lightning And Surge Protection For Cable Networks And Antennas For TV (Part 1)


Protective Mechanisms

If an antenna is protected by isolated air-termination systems it means:

- That in the area of flat roofs an air-termination rod will be installed with the required separation distance s, putting the whole antenna arrangement (mast and antennas) in the protective zone of the protective angle (Figure 4).

Now the antenna arrangement is no longer in lightning protection zone LPZ 0(risk of direct lightning currents) but lightning protection zone LPZ 0(risk of indirect impulse currents and of the unattenuated electromagnetic field of lightning).

Antenna with air-termination rod on a flat roof of buildings with external lightning protection system

Figure 4 - Antenna with air-termination rod on a flat roof of buildings with external lightning protection system


- That in the area of pitched roofs an air-termination rod will be installed with the required separation distance s using highly insulating distance holders (DEHNiso distance holders) to fix it at the antenna mast, putting the whole antenna arrangement (mast and antenna) into the protective zone of the protective angle (according to the applicable class of LPS) - Figure 5.

Antenna with air-termination rod and highly insulating distance holder on pitched roofs with external lightning protection system

Figure 5 - Antenna with air-termination rod and highly insulating distance holder on pitched roofs with external lightning protection system


Also here the antenna arrangement is no longer in lightning protection zone LPZ 0A (risk of direct lightning currents), but in lightning protection zone LPZ 0B (risk of indirect impulse currents and of the unattenuated electromagnetic field of lightning).

Protection against surges, irrespective of an installed isolated air-termination system, has to be provided for the coaxial cable shields by surge protective devices, to be installed downstream the equipotential bonding bar (Figure 6).
Surge protective devices downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems with external lightning protection system and isolated air-termination system

Figure 6 - Surge protective devices downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems with external lightning protection system and isolated air-termination system


These surge protective devices to be used both as single devices and for rail mounting protect the downstream devices against inductive and/or capacitive inputs of waveform 8/20 μs, arising from cloud/cloud flashes, distant strikes or direct strikes into the isolated air-termination system.

Surge protective devices Type 3 have to be provided for any electrical equipment with 230/50 Hz downstream the equipotential bonding bar, which is installed for the coaxial cable shields. Care has to be taken that the lightning equipotential bonding is carried out for all systems leading into the building.

A lightning protection system not being installed, the following is recommended:

Surge protective devices downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems without external lightning protection system and with isolated air-termination system

Figure 7 - Surge protective devices downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems without external lightning protection system and with isolated air-termination system


- An air-termination rod mounted with insulated distance holders prevents from a direct strike to the antenna. For this the air-termination rod has to be connected with the earth electrode by a separately installed earthing conductor (Figure 7) to be guided preferably on the outside of the building and to be connected with the earth electrode at ground level.

Antenna mast and equipotential bonding bar have to be connected with the earth electrode via an equipotential bonding conductor.
Combined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems without external lightning protection system

Figure 8 - Combined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable shields in case of antenna systems without external lightning protection system


- If the antenna mast is earthed directly, combined lightning current and surge arresters have to be provided (Figure 8), because partial lightning currents, which the surge arresters are not able to control, will be conducted in this case through the coaxial cables.

The antenna mast has to be connected with the earth electrode by an earthing conductor.

Combined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable shields in case of underground cable networks

Figure 9 - mbined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable shields in case of underground cable networks


Underground utility lines of systems require combined lightning current and surge arresters being able to carry lightning currents. They also have to be mounted near the point of entrance into the building (Figure 9).

Reference: Lightning Protection Guide – DEHN Inc. (dehn.de)


About Author //

author-pic

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD programming and web-design. Present on



4 Comments


  1. Santana, JP
    Jun 30, 2014

    Very good article.


  2. jonathanreeves
    Oct 25, 2013

    The demand for bandwidth and reliability requires surge protection devices to be incorporated in today’s networks. PolyPhaser, Transtector and LEA offer high quality, industrial surge protection solutions for sensitive electronics. And the network requirements are full end-to-end power and signal integrity. Recently installed Category 5 cable from Techpart, which works really fine for me.


  3. José Santana
    Sep 16, 2013

    Very nice article.


  4. tarekdia
    Sep 13, 2013

    A NEW LECTURE ONHOW TO CONDUCT ACRC FLASH ANALYSIS USING ETAP
    http://WWW.ETAP-COURSES.COM

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