Scale Factors - Siemens ACCESS 9340 Reference Manual

PMCM-9340D-0208
2/2008

Scale Factors

© 2008 Siemens Energy & Automation, Inc. All Rights Reserved.
A scale factor is the multiplier expressed as a power of 10. For
example, a multiplier of 10 is represented as a scale factor of 1, since
1
10 =10; a multiplier of 100 is represented as a scale factor of 2, since
2
10 =100. This allows you to make larger values fit into the register.
Normally, you do not need to change scale factors. If you are creating
custom alarms, you need to understand how scale factors work so
that you do not overflow the register with a number larger than what
the register can hold. When WinPM.Net is used to set up alarms, it
automatically handles the scaling of pickup and dropout setpoints.
When creating a custom alarm using the meter's display, do the
following:
•
Determine how the corresponding metering value is scaled, and
•
Take the scale factor into account when entering alarm pickup
and dropout settings.
Pickup and dropout settings must be integer values in the range of
-32,767 to +32,767. For example, to set up an under voltage alarm for
a 138 kV nominal system, decide upon a setpoint value and then
convert it into an integer between -32,767 and +32,767. If the under
voltage setpoint were 125,000 V, this would typically be converted to
12500 x 10 and entered as a setpoint of 12500.
Six scale groups are defined (A through F). The scale factor is preset
for all factory-configured alarms. Table 6–2 on page 80 lists the
available scale factors for each of the scale groups. If you need either
an extended range or more resolution, select any of the available
scale factors to suit your need. Refer to "Changing Scale Factors" on
page 217 of Appendix B—Using the Command Interface.
ACCESS 9340 and 9360 Meters
Chapter 6—Basic Alarms
EN–79