we can still use the other, while if the whole base station
goes down, we can still work in DMO mode”. To add
extra value, Semco uses TETRA’s data capabilities to allow
operators to track the movements of their workers, using its
marine co-ordination system SemPAM.
To further ensure availability, the base station’s power
supply can be backed up, as Søndergaard explains. “It depends
on the client’s requirements, of course. Sometimes there is
a UPS system available on the platform that we connect to.
We also have the option of installing a small battery back-up
inside the service boxes that we have from DAMM to provide
two to four hours’ running time, which depends on the
amount of transceivers and the load that we experience on
the equipment. When we install repeaters inside the wind
turbines, we typically also install a small UPS bank to support
the repeaters in the event that the turbine needs to be shut
down during maintenance.”
One added complication stems from the way wind farms
have been developed and then sold on. “A lot of the bigger
clients who have lots of elds have traditionally implemented
a wind farm as a single entity, so everything is geared up to
that one wind farm,” says Gallant. “ere’s a trend, certainly
in some of the bigger players, to take all of that co-ordination
between the dierent wind parks and try and make a hub
for communications onshore from a marine co-ordination
perspective, which gives them challenges – basically trying to
bring all the dierent TETRA and VHF systems together.”
He adds that they also want exibility so that “if they were
to sell the park o to somebody in the future, they still have
the ability to cut that eld out of a multisite solution”.
Søndergaard says one of the most important things to
consider when deploying TETRA in this sector is “proper
training of the users on the radio equipment, so they know
how to operate the equipment when they are in the eld
and know the dierence between trunked operation and
direct mode operation”. In some cases, clients have reported
that their systems aren’t working, only for the issue to be due
to “the users not being fully educated on the system”.
ere is also the harsh conditions and their potential
impact on equipment, so Semco works to protect it as much
as possible. Søndergaard adds: “Typically, we try to avoid all
products that contain aluminium since it has been proven not
to withstand a long time in a maritime environment. We try
Typically, we try to avoid all products
that contain aluminium since it has
been proven not to withstand a long time
in a maritime environment
to mount the equipment inside the substations or we also
put up environmental enclosures next to the antenna tower
and so on, if we need to shorten the feeder runs.”
In addition, the risk of lightning strikes is a concern, so
Søndergaard says it is important to spend more attention on
ensuring adequate grounding compared with what would be
needed “if it was just a non-critical onshore installation”.
He also emphasises the need for “good handcraft”, adding:
“Most of this work that we supply to our end-clients is being
installed at dierent yards all over Europe. Often the people
installing antennas, cables and so on are not familiar with
antenna cables and coax connectors. It requires the correct
people to install this equipment ie, the engineer or electrician
needs to know what they are doing. For instance, if a 7/8-
inch cable is being installed and the electrician secures it to a
tray with ties that squeeze that cable, then the cable will need
to be replaced soon afterwards, costing time and money.”
Gallant adds that quite often “if there’s a problem, it’s
actually down to a bad installation on the antenna side of
things, which can be avoided”.
Turning to handsets, Søndergaard says: “For oshore
workers, it’s better to buy a little bit more expensive
equipment from well-known manufacturers like Sepura,
Motorola Solutions and so on because they just withstand
the oshore conditions a lot better than some of the
rather cheap equipment that you can buy from the Far East.”
Returning to the point about backhaul, Gallant says at
the start of the construction phase “you might have nothing
out there, it’s just blue water”, so a temporary TETRA base
station with VHF with a satellite back to shore might be used.
However: “If possible, we would try and see if there’s some
sort of local infrastructure available. Typically, before a wind
farm’s construction phase begins, there might be a metrology
mast that would have been deployed beforehand to ensure
that the project placement will be economically viable; so
sometimes we can hook on the back of a metrology mast and
set a temporary base. If it’s got bre back to shore then we
use that, and if there’s a nearby platform we can use its bre
back to shore.” He adds that during the operation phase, the
cables that conduct the electricity generated by the turbines
back to shore include bre, and it is this which is used for
backhaul in normal operations.
Gallant says the approach to maintenance and ongoing
support varies from customer to customer, with some
allowing Semco to access their network, so it can remotely log
onto the base stations, monitor for them and examine their
log les to see if there are any problems brewing. ose clients
that do not allow this require their own personnel to be more
technically informed so they can do the work themselves.
Clearly, while ensuring reliable communications in
tough maritime conditions is not without its challenges,
these can be overcome with the right combination of expertise
and planning.
Redundant
TETRA
transceivers
January 2019 @CritCommsToday 21