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PHA
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The PIU measures the instantaneous phase that varies with the changes in the mains frequency.
However, since the same frequency variation is also seen by the Remote Reference Unit, the
variation is cancelled out.
NOTE
: For this reason, an additional Remote Reference Unit is required where the frequency of
the mains supply to the Remote Reference Unit, is not phase locked to frequency of the mains
supply at the place where the PIU is making measurements (e.g. Mainland European based PIU
locations cannot use the UK based Remote Reference Unit in Cardiff. They must use a Remote
Reference Unit installed within Mainland Europe).
The measured phase is required to be within ±30° of one of the three display vectors that are
separated by 120°, in order to display the vector on the unit.
The measured phase can be uploaded to the reference unit by pressing F1 for more than 3
seconds and releasing the button. An example of the data uploaded is shown below:
•
L1,4,5,$GPRMC, 105412.00,5130.11239, N, 0307.14367, W, 347, 050
•
L2,3,2,$GPRMC, 105412.00,5130.11239, N, 0307.14367, W, 097, 050
•
L3,3,1,$GPRMC, 105412.00,5130.11239, N, 0307.14367, W, 214, 050
The format of the data may differ from that shown but will always have the detected phase (L1
or L2 or L3 as shown) L0 indicates unknown phase.
The remaining data shown in the examples include the accurate date/time field, followed by the
Latitude and Longitude GPS co-ordinates for the PIU at the time of the data upload (51°
30.11239”N 03° 07.14367”W – HAYSYS, Cardiff). It also includes the instantaneous phase and the
reference phase (050 = L2 in this case).
5.2 Location of the Remote Reference Unit
Traditionally, other systems require a reference unit to be installed within the local substation.
This is not the case with the HAYSYS PIU.
Only a single Remote Reference Unit is required for
the whole Distribution Network
. The only need for an additional reference unit is when one
Distribution Network is not Phase Synchronised with the Distribution Network where the PIU is
being used (e.g. using the PIU in Europe and connecting to a Remote Reference Unit installed
within the UK). HAYSYS has a Remote Reference Unit installed at its offices in Cardiff. This is
sufficient to allow PIU users to operate the PIUs anywhere within the United Kingdom.
Of course, customers can also purchase their own Remote Reference Unit if they so wish, but
this is not necessary.
Should a phase change be present between two points across a single Distribution Network,
then the HAYSYS PIU allows the phase reference to be offset locally from the Remote Reference
Unit. The unit also accepts changes due to WYE-DELTA connections. The PIU operator can rotate
the phase reference stored within the PIU to correct for this phase change (see section 5.4 to
see how to do this).
It is recommended that prior to its use, the phase indicated by the PIU is confirmed to be correct
by measuring the phase of a known point (this could be within the substation or any other
property where the phase is known to be correct). If it is not, then the reference phase of the
PIU should be rotated until the PIU indicates the correct phase.