Siemens MJ-XL Installation And Operation Manual page 24

4
Setting Up the MJ-XL Control Panel
tapped sensing transformer to correct the voltage. Instead
of using a sensing transformer, the MJ-X
voltage mathematically, using the P2 PT turns ratio. The
turns ratio for a given regulator can be determined from
the regulator' s nameplate.
To define the turns ratio, you must first determine which
column in the nameplate describes the "P2" secondary
for a given primary voltage. P2 describes the pin on the
Polarized Disconnect Switch (PDS, or jack plug). The P2
pin is attached to the regulator Potential Transformer sec-
ondary (if present), and is usually labeled Control Volts on
the nameplate. See Figures 4.1 to 4.3 for examples.
Note: For an ANSI type B regulator, the utility wind-
ing tap leads are labeled P3, P4, P5, ...etc. and
the P2 lead is connected to the U2 terminal on
the PDS.
View P2 PT, then specify the turns ratio exactly as it is
specified on the regulator nameplate (e.g., 7620:121). The
microprocessor will correct the reference voltage to the
basis voltage (115, 120, or 125 V). Default value is 120 V.
If an inverted (Type B) regulator has a source-side Potential
Transformer, the utility (tertiary) winding leads are labeled
P3, P4, etc., and the P2 lead is connected to the "U2" ter-
minal on the PDS. The source-side PT leads are now
labeled P12, P13, etc., and the P12 lead is connected to
the P2 terminal on the PDS in the control box.
Note also that no reverse power flow relay is required. The
microprocessor senses the reversal and applies the appro-
priate polarity.
4.3.8 CTratio (Current Transformer Ratio)
The Current Transformer ratio defines scaling for current
measurements.
View CTratio: then specify the ratio exactly as specified on
the nameplate. See Figures 4.1 to 4.3 for examples.
The primary side of this ratio is also used by the control
program to define the CT primary rating. This rating and
the I Threshold % define a tap change deadband for use
during certain reverse power flow conditions. (I Threshold
% is described below.)
4.3.9 Meter Volts (Meter Scaling)
The Meter Volts data item determines which voltage is
presented on the display screen. You can choose either
the Primary side (system voltage— e.g., 7620 V) or the
Secondary side (120 V nominal).
To make the choice, view Meter Volts. Specify PRI if you
wish to monitor the system-level voltage; specify SEC if
you wish to monitor voltage scaled to the nominal 120 volt
range.
Note: Power and energy calculations are always
derived from the system-level voltage and are
not affected by the Meter Volts setting.
20
4.3.10 I Threshold % (Low Current Threshold)
L
corrects the
The I Threshold % data item defines a threshold for load
current magnitude, below which automatic mode tap
changes are inhibited. This threshold is defined as a per-
centage of the CT primary rating. (See CTratio above.)
For example, in the case of a regulator with a CTratio of
200:0.2, the CT primary rating would be 200 A. If you
specify I Threshold % = 4, you are defining a low current
threshold of 8 A. (4%*200 A = 8 A).
To set the low current threshold, view I Threshold %: and
specify a percentage of the full scale CT primary rating.
4.3.11 I Shift (Current Shift)
The I Shift data item compensates for system current-to-
voltage phase differences. Consult the factory for proper
application of this data item. (Note: This data item is pri-
marily intended for use with Load Tap Change (LTC) trans-
formers.)
4.3.12 I Load Max (Maximum Load Current)
This item specifies the Maximum Load Current as a per-
centage of the Full Load Current. When the load current
(Ild) exceeds the Maximum Load Current, the MJ-X
vates the Overcurrent Alert condition.
4.3.13 I Full Load
This item specifies the Full Load Current for use in deter-
mining when an Overcurrent condition occurs. Typically,
the Full Load Current setting is the same as the CT Pri-
mary (the first number of the CT Ratio screen), though this
is not always the case. Locate the regulator' s Full Load
Current specification on the upper right side of the name-
plate (just below the "Class" specification). The regulator
nameplate shows the Full Load Current as "XXX Amps."
Enter the value for the Full Load Current setting into the
MJ-XL. See Figures 4.1 to 4.3 for examples.
4.3.14 R Limit, L Limit
These items set the Tap Position Raise and Lower Limit
values; the MJ-X
lower limit reached" Alert conditions. Configure these
parameters to match the Vari-Amp settings on the side of
the Tap Position Indicator Dial mounted on the regulator.
(For most applications, the Vari-Amp settings are at 10%.)
If the Tap Position reaches or exceeds the R Limit Setting,
the MJ-X
wise, if the Tap Position reaches or exceeds the L Limit
Setting, the MJ-X
The R Limit/L Limit settings are used strictly for alerting—
these limit settings do not prevent tap raise/lower opera-
tions from exceeding the limits.
4.3.15 Power Flow Modes
The Power Flow Mode data item allows you to specify
which control program algorithm will be used under
reverse power flow conditions. Systems which experience
power flow reversals have unique control requirements.
L
uses the limit values to check for "raise/
L
activates the "R Limit Reached" Alert. Like-
L
activates the "L Limit Reached" Alert.
Siemens Power Transmission & Distribution, Inc.
L
acti-