After the prohibition of radioactive conductor rods, they were replaced by E.S.E. (active) conductor rods. E.S.E. (active) conductor rods come in two types; electrostatic conductor rods and piezoelectric crystal conductor rods.
Protection is enabled by means of an active conductor rod, the tip of which is refined and sharpened in both conductor rod systems, and conductor rods are placed on the highest spot of the construction to be protected. Conductor rods are connected with the ground along the shortest route. The protection area they provide varies depending on the location of the installation and height of such location compared to the surrounding constructions. The electro-geometrical model method based on warning distance enables the safe calculation of protection level.
Active conductor rods suitable for ion devices also follow the same rules, however warning distance is further improved (about 1.5-3 times), because arc delay is reduced. Their advantage is the increase in efficiency, especially in the case of low-density lightning strikes, and a decrease in the lengths of conductor rods for some situations with very hard applicability.
Protection Diameter Calculation for Active Conductor Rod Systems
The protection radius of active conductor rod heads is calculated using the following formula depending on the protection level.
Rp2 = h( 2D-h) + ΔL( 2D+ΔL) h≥5 mt
In this formula;
h: Active conductor rod height (m)
Rp: Protection radius (m)
D: Lightning progress step or spark gap of lightning along the way
For Level I Protection D=20m
For Level II Protection D=45m
For Level III Protection D=60m
ΔL (m): V(m/µs).ΔT(/µs)
Using the formula;
V: Movement velocity of ions formed around the attractor under lightning conditions to reach the lightning, V=1m/µs as per the standard.
ΔT: Time it takes for conductor rod systems to attract the lightning.
ΔL: Distance to catch lightning in ΔT time (i.e. the distance that ions travel to reach the lightning).
This parameter varies depending on the manufacture conductor rod system, and is determined in laboratory tests according to the manufacturing method and specifications.
Electrostatic Conductor Rods
Electrostatic active conductor rods form an effective protection area against lightning. Such type of conductor rods have different manufacturing techniques and an effective protection area. Electrostatic conductor rods come in various types and shapes. They have several different test reports, standards (ISO and their local standards), and generally an anti-corrosion warranty of 25 years.
Electrostatic conductor rods operate by using the electromagnetic field that changes/densifies in the air prior to lightning striking. When the electromagnetic field difference between the air and ground increases, the mechanism inside the conductor rod shifts to the ionization system using this difference, and starts an ion diffusion. It creates a lightning channel with this ion diffusion, and conducts the lightning from itself to the ground.
The lightning rod unit functions both in positive lightning conditions and negative lightning conditions. Electrostatic conductor rods have active and passive ionization electrodes. Thanks to their passive electrodes, they detect the potential difference between the location of the conductor rod and the ground, and enable ionization in the air in the most guaranteed way. The ion efficiency reaches its maximum level thanks to the internal ion generator system contributing to ionization diffusion.
Piezoelectric Crystal E.S.E Active Conductor Rods
Piezoelectric crystals are crystal structures that convert electrical energy to mechanical energy and vice versa. They are made of a very rigid material called lead-zirconate-titanate, and their tips are covered with nickel, which has the quality of a thin layer of electrode. When used as generators, these ceramics generate voltage levels between 20,000 and 25,000V that are much higher than the voltage required to obtain the desired ions, simply by increasing the pressure.
Piezoelectric excitation (reversible effective voltages) is mostly obtained with the vibrant effect that occurs in the pole resonance, vibrant effect that occurs due to the pre-tension applied on the exciter, and the power that is generated from the conductor rod’s own combination in the presence of the smallest turbulence. When connected to the transducer with electrical power, emitter ends are exposed to this high voltage. For this reason, they release high amounts of ions (7.65*1010 times 2.5 to 6.5kV). While these ions are captured by the VENTURI circuit, an ionized air flow occurs around the attractor head and its extension.
Piezoelectric crystals are made from some minerals that are found in nature. Therefore, they are not affected by the lightning discharges. They are protected against both positive and negative lightning discharge.
In these conducting rods, high voltage impacts generated by the vibrations received by the piezoelectric crystal found in the body of the device create an ionization. Accelerated ion diffusion occurs thanks to the ion diffusion mechanism in the shape of a venturi pipe. Thus, a lightning channel is created with this ion diffusion, and the lightning is conducted from itself to the ground. Piezoelectric crystal is present in the lower body. The upper section contains the ion diffusion system and protection system. For various models, there are protection radii depending on different level results as per different h heights. As they operate with piezo crystal, a durable natural mineral, this type of conductor rod is superior to electrostatic active conductor rods.
Shortening of Corona Effect Warning Time: Research shows that the piezoelectric ionization system generally shortens the warning time of corona effect (Townsend avalanche). According to the latest research conducted by N.L.Allen, T.E.Allibone and D.During, increase of ionization density (150-1100 ion/cm3) shortens the warning time by 50%, and the more the ionic density increases, the more this delay decreases regularly. In other words, any artificial increase that occurs in the ionic density in the air surrounding an electrode leads to a decrease in the ionization voltage. With such an effect, the electrical field is extended, ionization is enabled in the lightning attractor end, an ionized air channel is created inside the detection head, excitation delay is shortened by stimulating the corona effect, and the discharge rate of the corona current is increased.
Protection Radius of Active Conducting Rod
The role of ground connection is significant in the effective operation of an active conducting rod system, and it must be installed carefully. NF C 17-100 and NF C 17-102 standards state that the cage and conducting rods for each down conductor must have a separate/independent grounding. Electrical grounding or the available arch are connected to these conductors to provide equipotential. Lastly, it is required to keep the conductor grounding as far away from any underground metal electric power transmission pipes as possible (3-5m), and the ohmic value with low wave impedance must not be above 10 Ohm.
Active Conductor Rod Installation Elements
Conductor rod head: The part that captures the atmospheric electrical discharges of the area to be protected from lightning to be conducted to the ground.
Conductor rod pole: The pole carrying the conductor rod.
Pole crochet: Enables detection of the down conductor on the pole.
Conductor rod pole lock clamp: Used to fasten the pole of the conductor rod.
Tile crochet: Enables the down conductor to descend from above the tile.
Down conductor: The conductor used for grounding the conductor rod.
Wall crochet: Enables the down conductor to descend from above the wall or concrete.
Control (test) terminal: The element that enables measurement of the grounding resistance.
Protection pipe: The element that protects the part of the down conductor between the control terminal and ground against impacts.
Protection pipe lock clamp: The crochet used to secure the protection pipe.
PVC hose: The hose inside the protection pipe containing the conductors.
Grounding electrode: Installed underground and used to decrease resistance.
Exothermic welding/grounding electrode head: Used for the connection of the down conductor and electrode.
Note: The label on the active conductor rod must be checked to confirm that the product is under warranty by the manufacturing company.
External Conductor Rod Systems Design Defects
- “Side arcs” that occur when high impedance (resistivity) appears somewhere on the conductor along the down conductor, and low impedance appears on the metal surface nearby.
- Loss of effectiveness of the external conductor rod system as a result of situations, such as inaccurate conductor section, inaccurate fixing range, inaccurate fold, resulting from the design defect of down conductors.
- Exceeding periodical maintenance and inspection time.
Precautions
All metal surfaces must have the same potential value by establishing equipotential connection.
The down conductor must be connected with the ground through the shortest route, and fixed at a maximum of 1m ranges.
Corrosion that occurs in the External Conductor Rod System, loose-broken connections, and missing-lost materials must be checked by specialist institutions, and the results must be reported.
Conductor Rod Inspection and Grounding Measurement
Lightning protection installations, such as radioactive conductor rods, active conductor rods and Faraday cages, as well as electrical and grounding installations, must be inspected at least once a year pursuant to the following regulations and specifications.
In the “Regulation on Grounding in Electrical Installations/Annex-P” issued by the Ministry of Energy and Natural Resources and published in the Official Gazette dated 21.08.2001 and numbered 24500, recommended periods concerning the inspection, measurement and audits of various grounding installations during the operation period are given below:
For electric production, transmission and distribution plants (excluding the energy transmission and distribution lines): 2 years
Energy transmission and distribution lines: 5 years
For industrial plants and trade centers: ...
Inspection and measurement of resistance related to grounding: 1 year
Other inspections, measurements and checks related to grounding facilities: 2 years
For unfixed facilities: ...
For fixed operating elements: 1 year
For mobile operating elements: 6 months
The inspection, measurement and audit periods of grounding facilities within the scope of precautions to be taken in work places and works involving flammable, explosive, hazardous and harmful substances, and grounding facilities in work places, including work in wet environments, cannot exceed one year.
Pursuant to TS622 issued by the Turkish Standards Institute on 04.12.1990 under the Decree of the Council of Ministers dated 4.1.1976 and numbered 7/11204, Article 2.11.2 states the “Rules for Protection of Constructions from Lightning” as; “inspections must be repeated preferably at intervals not exceeding 12 months. Choosing an interval slightly shorter than 12 months might be beneficial in order to vary the season of inspection.”
Pursuant to the “General Technical Specifications, Section 7, Electrics General Technical Specifications of Construction Works” issued by the Republic of Turkey Ministry of Public Works and Settlement, Article 47.15.1 states that “maintenance of all types of lightning protection systems shall be performed periodically on a yearly basis.” It is also obligatory to perform maintenance of conductor rods and grounding pursuant to the Occupational Health and Safety Regulation of the Ministry of Labor and Social Security.
Grounding Rules for Communication Installations around Lightning Protection Installations
Adjacent Grounding Rods: If there are other grounding rods at a distance shorter than 2m from the grounding against lightning, all grounding rods must be connected to each other. It is recommended to connect all grounding rods with each other where the distance between them is 2-20m. In cases where ground resistivity is higher than 500Wmt, it is also recommended to connect the grounding rods with a distance longer than 20m between the grounding for protection against lightning.
Protection of buildings against lightning: It is recommended to connect the grounding installations related to the communication system to the lightning protection installation. For this purpose, the same conductor sections and elements must be used as in the lightning protection installation. Grounding bonding (ring) conductors are connected many times whereas grounding bus bars or grounding terminals are connected only once.
In order to prevent arcs in high buildings (such as steel-concrete communication towers) that contain communication installations inside and might be exposed to lightning hazards, the vertical metal parts must be covered with reinforcing bars with adequate sections (St 37). The function grounding and protection conductor (FPE) of the grounding bonding conductor along the upward route for technical hardware must be connected to the covered vertical metal parts on each floor, but at distances of at least 10m apart and also on the lowest and highest points of the building (for instance the building’s ironwork).
In such case, these parts must have easily accessible connection points. If the lightning protection installation is kept separate from the operating grounding of a main step-down station, the grounding installation of the communication system connected to this operating grounding can be connected to the lightning protection installation only using the arrester.