Page 35 - 260909_BACnet_Europe-Journal_45

BACnet Insight

to move the current boundary between Ethernet net- becomes increasingly digital, cybersecurity can no longer lation rules, network topologies and a broad portfolio of
works and field communication further down the automa- be considered solely at the management and automation controllers and field devices.
tion hierarchy. A sensor or actuator with a serial interface levels. Field devices are also becoming intelligent, net-
would no longer necessarily become part of the IP world worked and updateable components. Rethinking Network Topologies
only through a controller or gateway but could itself be
integrated directly into an Ethernet-based communication SPE can potentially enable IP communication over cable The move to SPE does not mean that existing field bus
architecture. routes originally installed for conventional serial field structures can simply be transferred unchanged. This is
bus communication. In suitable installations, this means one of the key challenges for broader adoption.
Particularly Interesting for Retrofit Projects that BACnet/SC can also be extended further into the
field level. This opens up the possibility of encrypted and 10BASE-T1L is designed for long distances and funda-
One of the most promising opportunities for SPE lies in authenticated BACnet communication over existing two- mentally uses point-to-point connections. This differs from
existing buildings. Installing completely new cabling is wire infrastructures. Comparable IP-based security archi- bus structures familiar from technologies such as BACnet
often technically challenging and economically difficult to tectures were previously difficult or impossible to imple- MS/TP. In addition, 10BASE-T1S is available as an SPE
justify. At the same time, many buildings already contain ment over such cabling using traditional serial field bus variant for shorter distances and multidrop applications.
two-wire connections running over considerable distances technologies, or they involved technical compromises and
to field devices. SPE can open up new possibilities here. significant reductions in transmission speed. Building automation therefore requires network concepts
Depending on the cable type, the quality of the existing that combine the technical advantages of SPE with the
installation, cable lengths and the specific installation con- SPE can therefore offer a double benefit, particularly in economic and practical requirements of typical building
ditions, it may be possible to reuse existing cabling for SPE retrofit applications: the existing physical infrastructure installations. Switches, connection technology, power sup-
communication. may be reused while the communication technology run- ply and network topology must be considered alongside
ning over it takes a significant step forward. A cable that installation, commissioning and maintenance.
This decision does not have to be based solely on theo- previously carried a traditional field bus can thus – fol-
retical cable specifications or documentation that may be lowing appropriate testing and with suitable components The success of SPE will consequently depend on more
decades old. Measurement and test equipment is already – become an Ethernet connection. IP and ultimately than the physical layer alone. What is needed is a com-
available to assess existing cable routes and determine BACnet/SC can then operate on top of it. plete ecosystem that can be planned, installed and oper-
whether a reliable SPE connection can reasonably be ated as naturally and efficiently as today’s established
implemented. The Connector Question: Hardly an Obstacle for field bus solutions.
Building Automation
This is particularly important for retrofit projects. In What Comes Next for SPE?
existing buildings, it is often not fully documented which The development of Single Pair Ethernet has not been
cables were actually installed or what condition they are in entirely free of debate. In the past, different groups within The coming years are likely to be characterized primarily
today. Age, cable length, installation method, connection the SPE community had different views on which connec- by the continued development of this ecosystem. The first
points and other factors can influence the transmission tor interfaces and connection systems should become SPE-enabled controllers already demonstrate that com-
characteristics of a link. established standards. Various technical approaches and bining SPE with BACnet is technically and practically fea-
interests led to discussions that were sometimes per- sible. Wider adoption, however, will require more sensors,
Testing and qualifying the actual installed cable provides ceived by potential users as a possible obstacle to broader actuators, room automation devices, switches and infra-
greater planning certainty. Before modernization begins, it market adoption. structure components.
is possible to identify which links are suitable for SPE and
where modifications or new cabling may be necessary. This situation has since been resolved, with the relevant SPE is unlikely to replace all existing field bus systems at
This creates a pragmatic modernization approach: test connection technologies standardized or assigned to their once. A gradual development is much more probable. New
before replacing. Existing cables can first be qualified, respective application areas. installations can be designed from the outset with a more
and suitable links can then be reused for Ethernet-based consistent Ethernet architecture. In existing buildings, SPE
communication. For traditional building automation, however, the question can be deployed selectively wherever existing two-wire
of a single universal SPE connector is less significant than cabling enables an economically attractive migration path.
The long distances possible with 10BASE-T1L make this it may be in other industries using preassembled cabling.
approach particularly interesting for building automation. Field devices in building automation are often not con- Developments at the device level will be particularly
Under suitable conditions, an existing two-wire cable that nected using standardized network plugs. Screw termi- important. As more manufacturers integrate SPE directly
previously carried a conventional field bus can become a nals, spring terminals and other terminal connections into sensors, actuators and controllers, fewer transitions
transmission medium for Ethernet. have been common practice for decades. between different communication technologies will be
required. At the same time, new device functions may
The real benefit extends far beyond higher data rates. The single pair of wires used for an SPE interface on a emerge that benefit from more capable IP connectivity.
Once Ethernet is available, IP communication becomes sensor, actuator or controller can therefore be connected
possible. This opens up new options for device manage- to suitable terminals in much the same way as a conven- Power transmission over the same pair of wires is another
ment, diagnostics, software updates and cybersecurity – tional field bus cable. The connector debate that attracted important element for future applications. Combining data
potentially without having to recable the entire building. considerable attention within the SPE community conse- communication and power supply within the same infra-
quently affects large parts of the building automation mar- structure can be a significant factor in economically con-
BACnet/SC over Existing Cable Routes ket only marginally. necting large numbers of field devices.

The combination of SPE, IP and BACnet/SC is particu- Other factors will be more important for the success of SPE should therefore not be viewed solely as a replace-
larly interesting in this context. As building automation SPE in buildings: interoperable components, clear instal- ment for existing communication technologies. It can also

BACnet Europe Journal 45 09/26 35