38
Connecting the Current Sensors (Current Input)
If the input exceeds the measurable range (using VTs and CTs)
Use instrument transformers: voltage transformers (VTs [potential transformers, PTs]) and current
transformers (CTs) externally. VT ratios and CT ratios can be set on the instrument to allow primary-
side input values to be read directly.
See “Scaling (when using VTs [PTs] or CTs)” (p. 63).
DANGER
Do not touch VTs (PTs), CTs, or any input terminals of the instrument
when they are energized.
Doing so could result in serious bodily injury.
WARNING
When using VTs (PTs) externally, do not short the secondary side.
Applying a voltage to the primary side while in the shorted state may cause a large
current to ow to the secondary side, resulting in equipment damage or re.
When using CTs externally, do not leave the secondary side open.
If a current ows to the primary side while in the open state, a high voltage may occur
on the secondary side, resulting in a risk of the operator experiencing an electric
shock.
IMPORTANT
The phase dierence between the external VTs (PTs) and CTs may introduce a large error
component into power measurement. If you wish to make more accurate power measurement,
use VTs (PTs) and CTs with a small phase error in the frequency band of the circuit being used.
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