5.2 Measurements
5.2.1 Current measurement and scaling
The current measurement module (CT module, or CTM) is used for measuring the currents from
current transformers. The measured values are processed into the measurement database and they
are used by measurement and protection functions. It is essential to understand the concept of current
measurements to be able to get correct measurements.
Figure. 5.2.1 - 55. Current measurement terminology
PPRI:
RI: The primary current, i.e. the current which flows in the primary circuit and through the primary side
of the current transformer.
SEC:
SEC: The secondary current, i.e. the current which the current transformer transforms according to its
ratios. This current is measured by the protection relay.
NOM:
NOM: The nominal primary current of the protected object.
A
AQ
Q-F205
-F205
Instruction manual
Version: 2.04
56
© Arcteq Relays Ltd
IM00013
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