Ct Orientation Check - Siemens MD-12HD User Manual

CT Orientation Check

The MD-xxHD meter reports power and energy in each electrical quadrant under a different register.
When CTs are installed backwards, the indicated current vector is oriented 180 degrees away from the
true displacement angle. In accordance with standard definitions, the Wattage and VARs of the effected
channel report with a sign opposite from what is expected. Often this means that the import registers will
be reading zero while the export registers are showing a value. Note that backward CTs have no impact
on the amplitude of the Power Factor. A moderate power factor (>0.7) in concert with a negative power is
a clue that the CT is on backwards, but is on the correct phase.
Check that the wattage has the correct sign (Designated + for loads)
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ViewPoint HD: Real Time Values > (Confirm Sign of Power For All Elements)
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MD-xxHD Web App: Real Time Values > (Confirm Sign of Power For All Elements)
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LCD: Real Time Values > (Confirm Sign of Power for Each Element)
If a CT is discovered to be on backwards after the installation is complete, the direction of the
CT can be reversed through a user configuration register designed for this purpose, called the
"Flipper," located at 2226, 2234, and 2235 or use ViewPoint HD's meter setup.
Siemens Industry, inc.
Electrical Power Quadrants with Reversed CT Shown
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