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Phase currents
The three phase currents are displayed locally as
A and kA values and transferred via the SPA bus
as ampere values. Prior to this, though, the
measured values must be scaled, using the
information about the rated current of the pri-
mary side of the current transformer.
Example 12:
Scaling of a measured phase current value.
The rated current of the primary side of the
current transformers is 400 A. For scaling the
current must be given in amperes. The scaling
factor is 400.00.
>99WS9:400.00:XX
; Set scaling factor S9 at 400.00
>99WV151:1:XX
; Store the set parameters
The scaling factor can be set within the range
0.00…10000.00. Variable S9 has been given
the default value 200.00 after factory testing.
Phase-to-phase voltages
The voltages are displayed locally and trans-
ferred via the SPA bus as kV values. Prior to this,
though, the measured voltages have to be scaled
by means of a scaling factor. The scaling factor
is equal to the rated voltage of the primary side
of the voltage transformers, divided by 100.
Example 13:
Scaling of a measured phase-to-phase voltage
value.
The rated voltage of the primary side of the
voltage transformers is 16 kV. For scaling the
voltage must be given in volts. The scaling factor
is 16000 / 100 = 160.00.
>99WS10:160.00:XX
; Set scaling factor S10 value 160.00
>99WV151:1:XX
; Store the set parameters
The scaling factor can be set within the range
0.00…10000.00. Variable S10 has been given
the default value 210.00 after factory testing.
Active and reactive power
Active power is displayed locally and transferred
via the serial bus as megawatt (MW) values.
Correspondingly the value of reactive power is
displayed locally and transferred via the serial
bus as megavar (Mvar) values. The power is
measured in both directions. Positive values
have no sign and negative values are indicated by
the red minus sign.
Power can be measured via an optional mea-
suring module type SPTM 8A1 (option 1),
SPTM 6A2 (option 2) or SPTM 6A3 (option
3). Because the measuring principle varies with
the measuring modules, the possible option
used must be programmed into the control
module (parameter S90). In addition power
measurement can be enabled or disabled with
parameter S91. As a default power measurement
is disabled (S91=0).
A) Power measurement via mA inputs
(SPTM 8A1)
The input signal range of the mA-inputs is -20…
0...+20 mA. The following setting parameters
are used for scaling the inputs:
S12 = Low limit of mA signal related to active
power
S13 = High limit of mA signal related to active
power
S14 = Low limit of mA signal related to reactive
power
S15 = High limit of mA signal related to reac-
tive power
S16 = Value of active power corresponding to
mA signal at low limit
S17 = Value of active power corresponding to
mA signal at high limit
S18 = Value of reactive power corresponding to
mA signal at low limit
S19 = Value of reactive power corresponding to
mA signal at high limit
When power measurement has been enabled
the low and high limits of the mA signals are first
given and then the corresponding values of
active and reactive power.
