Ice NP900 Series, Инструкция по применению

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Application Guide - NP900 Series 7 (504
)
3 F
UNCTIONS OF
NP900
3.1 M
EASUREMENTS
3.1.1 C
URRENT MEASUREMENT AND SCALING
In NP900 series current measurement module (CT-module) is used for measuring the
currents from current transformers and processing the measured currents to
measurement database and for use of measurement- and protection functions. For the
measurements to be correct it is essential to understand the concept of the NP900 series
IEDs current measurements.
- PRI
o
Primary current, the current
which flows in the primary circuit
and through primary side of the
current transformer.
- SEC
o
Secondary current, the current
which the current transformer
transforms according to its ratios.
This current is measured by the
protection IED.
- NOM
o
Nominal primary current of the
load. Load in this means can be
any electrical apparatus which
produces or consumes electricity
and has rated value for when it is
producing or consuming
electricity in its rated conditions.
Figure 3.1.1-1 Current measurement terminology in NP900 platform
For the measurements to be correct it needs to be made sure that the measurement
signals are connected to correct inputs, current direction is connected correctly and the
scaling is set correctly.
For the scaling relay calculates scaling factors based onto the set CT primary, secondary
and nominal current values. Relay measures secondary current which in this case mean
the current output from the current transformer which is installed into the primary circuit of