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(EN 62305-3), a minimum wall thickness of the enclosure of currents (follow currents) up to 100 kA rms . Undesired supply
4 mm is required for steel. The lightning protection sys- disruption resulting from tripping main fuses is thus prevented.
tem must meet the requirement according to Annex D of Type 2 DEHNguard M TNS 275 FM surge arresters are installed
IEC 62305-3 (EN 62305-3) “Additional information for LPS in the downstream sub-distribution boards.
in the case of structures with a risk of explosion”. If the Ex A modular multipole DEHNventil combined arrester with high
zones of exhaust openings are located in the protected vol- follow current limitation is installed in the distribution board of
ume of lightning current carrying metal parts of the enclo- the CHP (Figure 9.3.10). This prewired spark-gap-based com-
sure, no additional air-termination systems are required. If bined arrester comprises a base part and plug-in protection
this is not the case, additional air-termination systems must modules. DEHNventil ensures maximum availability of the in-
be installed to protect the exhaust openings from direct stallation, disconnection selectivity with respect to 20 A gL/gG
lightning strikes. fuses as well as limitation and extinction of mains follow cur-
rents up to short-circuit currents of 100 kA rms .
Earthing concept If DEHNventil is installed close to the loads (≤ 5 m), protection
To avoid high potential differences between the individual of terminal equipment is also ensured.
earth-termination systems, they are interconnected to an over-
all earth-termination system (Figure 9.3.9). This is achieved Remote monitoring
by intermeshing the individual earth-termination systems of The remote monitoring system ensures that the performance
the buildings and systems. Mesh sizes from 20 m x 20 m to data of the biogas plant are permanently available. The instal-
40 m x 40 m have proven to be economically and technically lation-specific measured values can be directly read off the ac-
feasible. By intermeshing all earth-termination systems, po- quisition unit. This unit features interfaces such as Ethernet or
tential differences between the parts of the installation are RS 485 which are connected to a PC and / or modems for remote
considerably reduced. Moreover, the voltage stress on the enquiry and maintenance. Remote monitoring, for example via
electrical connecting cables between the buildings in case of modem, allows service staff to log on to existing systems and
lightning effects is reduced. to provide immediate support to the operator in case of failure.
The modem is connected to the network termination unit (NTBA)
Feeding electricity into the grid of a basic ISDN connection. It must also be ensured that the
The biogas produced is typically used in gas or pilot injection measured data are forwarded by means of the telecommunica-
engines to generate electricity and heat. In this context, such tion network via ISDN modem to provide permanent monitoring
engines are referred to as combined heat and power plants and to optimise the installation’s performance. For this purpose,
(CHP). These CHPs are located in a separate operations build- the U k0 interface upstream of the NTBA which is connected to
ing. The electrical equipment, switchgear cabinets and control the ISDN modem is protected by a BLITZDUCTOR XT combined
cabinets are housed in the same room or in a separate room of arrester (Figure 9.3.11). It is advisable to use a DEHNprotector
this operations building. The electricity generated by the CHPs surge arrester to protect the power and data side of telecom-
is fed into the public grid (Figure 9.3.10). munications terminal equipment and telephone systems with RJ
connection. Figure 9.3.11 shows an example of how to protect
Lightning equipotential bonding, which must be established a CCTV camera by means of these arresters. A shielded UKGF
for all conductive systems entering the building, is an integral BNC surge arrester is provided for the coaxial cable (video trans-
part of a lightning protection system. Lightning equipotential mission system). More detailed information on the protection of
bonding requires that all metal systems be incorporated in the CCTV systems can be found in chapter 9.7 “Surge protection for
equipotential bonding so as to cause as little impedance as pos- CCTV systems”.
sible and that all live systems are indirectly integrated in the
equipotential bonding via type 1 surge protective devices. Light- Process control
ning equipotential bonding should be established as close as The control unit is a key element of a biogas plant. Its function
possible to the entrance point into the structure to prevent par- is to centrally actuate all pumps and mixers, record process
tial lightning currents from entering the building. The incoming data such as the gas volume and gas quality, monitor the tem-
230/400 a.c. lines of the main low-voltage distribution board perature, acquire all input materials as well as visualise and
of the consumer installation (Figure 9.3.10) are protected by document all data.
type 1 surge protective devices (SPDs). DEHNbloc, for example, If the process control fails as a result of surges, processes for
is a type 1 surge protective device with RADAX Flow spark gaps biogas production are interfered with and interrupted. Since
for power supply systems. This lightning current arrester has a these processes are extremely complex, unscheduled down-
discharge capacity up to 50 kA (10/350 μs) per pole. The patent- time can lead to further problems so that the standstill period
ed RADAX Flow principle limits and extinguishes short-circuit may be extended to several weeks.

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