Prevention as the first tool for cultural heritage protection

Rich in historical and artistic evidence, Castello and Parco di Masino, whose origins date back to the year 1000 and protected by FAI (Fondo per l’Ambiente Italiano) since 1988, represents one of the assets that are part of the inestimable cultural heritage of our country.

One of FAI’s main objectives is to preserve and conserve the properties over time so that everyone can get to know them. This is possible, first and foremost, through the recognition of the cultural value of a Property and then with its conservation through restoration, maintenance and prevention, the latter being understood as the limit for all risks that could cause the loss of the Property, considering – above all – the growing risks arising from lightning phenomena.

In this logic of prevention which is an integral part of FAI’s way of working, from 2022 the Castello and Parco di Masino will be the first asset owned by the Trust to be equipped with a system of preventive defence against direct and indirect lightning strikes.

Together, let’s discover the project designed and implemented by Euthalia for the protection of Castello and Parco di Masino.

For historical and artistic landscapes and heritages such as the FAI properties, when developing lightning and surge protection projects, it is necessary not to underestimate the importance of considering not only the risk of loss of human life, but also the risk of loss of irreplaceable cultural heritage.

Indeed, should lightning strike a historical structure directly or indirectly, it could cause significant material damage not only economically but also structurally, compromising its original value.

The study and design for the protection against direct and indirect lightning strikes of the historic building were carried out following, in the first instance, the series of CEI EN 62305 technical standards for lightning protection.

Starting from the air area, devices were installed to protect the entire structure and the area surrounding it from direct lightning strikes. Their position was determined during the design phase by using the protection angle method, as required by the reference standard. (Fig. 1)

Fig. 1 Protection angle of the Euthalia active defence system installed on Castello di Masino, Caravino (TO)

On the highest terrace, the primary air head SATURNO 2 (commonly referred to as the ‘capturing rod’) was installed externally, which, at a height of 4 metres and with a coverage angle of 74°, protects the largest part of the building with its cone. (Fig. 2)

Fig. 2 Primary air head SATURNO 2

The primary SATURNO 2 air head was connected via FS 17 GV 95 cable to the grounding electrodes with two down conductors:

1. Direct to the grounding leakage circuit – single conductor.
2. Direct to the grounding leakage circuit, but interposing the air filter (SCa 200 kA) and the ground filter (SCt 500 kA). This connection is fundamental for the correct functioning of the Euthalia system with Ingelva technology: the air filter – connected to the head – works to enhance its effect; while the ground filter, an element that at steady state (50/60 Hz) behaves like an ordinary conductor, during storm phenomena becomes a high-impedance filter that, together with the rest of the system, helps to prevent the formation of direct strikes and block ascending lightning strikes.

The eaves, metal elements that are natural strike catchers for the structure, have been unified by joining them together at different levels with a bare copper cable with a cross-section of no less than 25 mm². In turn, the eaves loop is turn connected to the downstream air filter, thereby fulfilling the technical requirement of equal potential of the natural strike collectors to the ground node via down conductors or conductive downpipes.

The connection explained above makes it possible to create a reflector for our air head, which contributes to the ‘self-powering’ of the system by collecting electrical charges during thunderstorm phenomena, when there is an increase in the electromagnetic field in the air.

For the protection of the tower, on the other hand, the existing metal symbol on the top was harmonised and used as an absorber; this intervention made it possible to extend the preventive action area of the protection system. (Fig. 3)

Fig. 3 Harmonisation of the metal symbol on the Main Tower

The symbol on the tower, which is considered as a lightning arrester by the technical reference standard, was connected to the air head SATURNO 1, located under the tower roof. The integration of the SATURNO 1 air head within the structure, a position that does not compromise or limit its operation, made it possible to minimise the aesthetic impact of the lightning protection system on the castle.

In this portion, two more down conductors were built using FS 17 GV 50 cable and, using the same connection scheme as described above, the air filter (SCa 150 kA) and the ground filter (SCt 300 kA) were installed.
A square of ground electrodes was built for both air heads: four spikes, respectively two metres apart. This configuration makes it possible to increase the ground dispersion and, at high frequencies, to obtain a high impedance polarisation.

To preserve the aesthetics of the asset, all the conductor cables were inserted, where possible, inside the existing downpipes and, in order not to expose them to possible degradation due to the effects of moisture, an increased cable section was used to guarantee the electrical continuity of the circuit over time.

The following harmonisation work was also carried out (application of components useful for eliminating the “spike effect” generated by elements on the structure – particularly on the roof – which could cause a build-up of charges and compromise the operation of the Ingelva Antimpatto® technology protection system):

• Insertion of another SATURNO 1 air head under the roof located on the south side of the structure, to extend the system’s preventive action area. (Fig. 4)
• Harmonisation of the remaining metal symbols on the structure with 25 mm² bare copper cable. (Fig. 5)
• Installation of harmonising metal components (APS and AGSE – sky brushes) on all chimneys present and ringing of the pointed stone details. (Fig. 6)
• Installation of a ground filter (SCt) in correspondence with the wind tower downpipe.
• Installation of a ground filter (SCt) in correspondence with each existing ground leakage line entering the structure.

As can be seen in the following pictures, and in particular in Figure 7, each conductor has been carefully painted to promote integration with the surrounding part of the structure.

Fig. 8 Installation of surge protection devices upstream of switchboards