Infrastructure and Mobility, Traffic Solutions
Sopers Lane, Poole, Dorset
BH17 7ER
Version
7
Page 55 of 76
Status
ISSUED
Last Editor
Ore Oluwatudimu
TS008468
Date
31/01/2017
Document
Name
UPS Solution General Handbook
Doc. No.
667/HB/47750/000
Copyright
Siemens plc 2017 All Rights Reserved
12.6.2 Generator Selection
Generators to be used with the Siemens UPS solution
must
adhere to the following
conditions.
WARNING:
Using a Generator that does not meet all the conditions below is a
major safety risk
and may also cause permanent damage to the UPS solution.
The generator:
•
Must have an output rating not exceeding 7.4kVA but at least double that of the
FXM UPS unit fitted within the UPS solution.
o
Suggest 3kVA for the FXM1100
o
Suggest 6kVA for the FXM2000
•
Must be 230V single phase.
•
Must be fitted with a link between Neutral and Earth (i.e. not floating earth).
12.6.3 Protection and Reference Earthing
In
all
cases, all generator outlets
must
be protected by
30mA RCDs
.
As described in section 7.2, the traffic installation’s bonded street furniture form a
rudimentary TT earth electrode, the quality of which must be tested and recorded as part
of UPS commissioning.
If this test was passed then the installation itself provides a
perfectly adequate earth reference for a generator
and no additional equipment is
required. See section 11.2 for more details of the installation TT Earth Electrode test.
WARNING:
If there is
ANY DOUBT WHATSOEVER
about the TT earth
provided by the installation (e.g. the TT earth electrode test results are not
available) then additional reference earthing may be required, as described
below.
Additional reference earthing is not required if
all three
of the following statements are
true for the site:
•
The controller is ELV.
•
There are no other metallic items within touching distance (2m) of the generator,
feeder pillar, UPS solution, controller cabinet or any other part of the traffic
installation including all signal columns.
•
The generator will be connected for no more than 24 hours.
If the TT earth of the junction is in question and one or more of the above statements
does not apply, the generator
must
be provided with a separate, dedicated earth
electrode, such as an earth spike or mat, for reference earthing. This earth electrode
should have a resistance less than 200 OHMS.
NOTE:
Generator referencing earth electrodes cannot be tested with an earth
fault loop impedance tester as they do not actually form part of the fault path. A
priority earth electrode tester must be used instead.
Where it is impossible to install an earth electrode, it is acceptable to bond the main earth
terminal of the generator to simultaneously accessible metallic items that do not form part
of the traffic signal installation (i.e. a lamp column and/or guard rail). An earth wire with a
cross-sectional area no less than 16mm2 should be used for this bond.
