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For multi-unit filters, the following diagram is applicable:
Figure 74: Basic CT configuration in the case of a multi-unit filter arrangement
8.6.2.2 Material needed and hypotheses for correct measurements
A two-channel scopemeter with one voltage input and one current input is needed.
Adequate probes are also needed. A power analyzer like the Fluke 41B can also be used.
Some minor knowledge of the load is also required. For instance, the method explained
below is based on the fact that the load is inductive and not regenerative (i.e. the load
current lags by less than 90° the phase voltage). If a capacitor bank is present, it is better
to disconnect it before making measurements in order to ensure an inductive behavior
of the load. It is also assumed that the load is approximately balanced.
Remark: Other way to check the CT installation manually is to use the waveform displays
of the PQF-Manager. In this it should be noted that all waveforms displayed are
synchronized on the rising edge zero crossing of the voltage V (L1-N). Note however that
this approach requires some experience.
8.6.2.3 Checking the correct connection of the CTs with a two-channel scopemeter
−
The first channel of the scopemeter must be connected to the phase voltage
referenced to the neutral or to the ground if the neutral is not accessible
−
The second channel must measure the associated current flowing from the
network to the load as seen by the CT input of the PQF
8.6.2.3.1 Measurement of the CT in phase L1
−
For the voltage measurement (channel 1), the positive (red) clamp must be
connected to the phase L1 and the negative clamp (black) must be connected to
the neutral (ground)
−
For the current measurement (channel 2), the clamp should be inserted into the
wire connected on terminal X21.1 and the arrow indicating positive direction of
150 Commissioning instructions Manual Power Quality Filter PQFS
(only shown for one phase)
(Figure 75)
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