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2.3 Making the Connections
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2.3.2 When Using PT or CT
DANGER
Once the connections are made, do not touch the input terminals of
the voltage and current transformers. There are exposed live parts,
and a danger of electric shock or serious accident.
Check that the terminals are tightened securely. If the connections
should become detached, there is a danger of a short-circuit or
electric shock accident. Additionally, if the connections are not
properly tightened, the contact resistance increases, which may lead
to the generation of heat, or fire.
WARNING
When using an external voltage transformer, do not leave the
secondary side short-circuited. If a voltage is applied to the primary
while the secondary is short-circuited, a high current will flow
through the secondary, which could lead to fire or malfunction.
When using an external current transformer, do not leave the
secondary side open-circuit. If a current flows through the primary
while the secondary is open-circuit, this can generate a high voltage
on the secondary, which is extremely dangerous.
Before switching on power for the line to be measured, check that
the connections and the wiring are not shorting between the voltage
input terminals. If there is a short circuit, a electrical shock and or
short circuit accident will occur.
To prevent accidental electrocution or short-circuits, make
connections to the voltage and current input terminals using only
insulated wire that is terminated with pressure-fitted terminals. (The
voltage and current input terminals have an M6 axial diameter.)
CAUTION
To avoid electric shock, the wiring which is used for making the
connections to the current input terminals should have sufficient
current carrying capacity and insulation.
NOTE
SOURCE side
LOAD side
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input terminals
･ By setting the PT ratio and the CT ratio, it is possible to directly read the
first side of the PT and CT. For details, refer to Section 4.7, "Setting the PT
and CT Ratios and SC."
･ The secondary side of the PT or CT must be grounded for safely. (Since
most previously attached PT and CT's are already grounded, please check
before grounding.)
･ When using an outside connected trans (PT,CT), the phase differences of
those may cause differences in the electrical measurement. If a precise
electrical measurement is necessary, use a PT or CT that has only a small
phase difference from the wiring's wave length area that is to be used.
･ Depending on the input level, power meter losses may affect measured
values. Refer to Section 2.3.3 for how to make connections that minimize
power meter losses.
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