ABB REM 54 Series, Техническое справочное руководство

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44
1MRS750915-MUM
Machine Terminal
Technical Reference Manual, General
REM 54_
5.1.6.1. Scaling the rated values of the protected unit for analog channel
A separate scaling factor can be set for each analog channel. The factors enable
differences between the ratings of the protected unit (generator, transformer, motor,
etc.) and those of the measuring device (CTs, VTs, etc.) The setting value 1.00
means that the rated value of the protected unit is exactly the same as that of the
measuring device.
When scaling factors are used, it should be noted that they affect the operation
accuracy of the terminal. The accuracies stated in the function block manuals on
CD-ROM Technical Descriptions of Functions only apply with the default values of
the scaling factors. For example, a high factor affects the operation of sensitive
protection functions such as the directional earth-fault protection.
The scaling factor is calculated channel by channel as follows:
Scaling factor = I
nmd
/ I
np,
where
Example:
The scaling factors for the analog channels can be set via the HMI of the machine
terminal or with the Relay Setting Tool. The HMI path for the scaling factors is:
Main Menu/Configuration/Protected Unit/Ch 1: scaling,
Ch 2: scaling
...
I
nmd
Rated primary current of the measuring device (A)
I
np
Rated primary current of the protected unit connected to the channel
Rated primary current of current trafo = 500 A: I
nmd
= 500 A
Rated current of the protected unit = 250 A: I
np
= 250 A
Scaling factor for current channels: 500 A / 250 A = 2.00
The scaling factor is not used for general measurement signals
connected to the analog channel.