Material Needed And Hypotheses For Correct Measurements; Checking The Correct Connection Of The Cts With A Two-Channel Scopemeter - ABB PQFM Instruction Manual

Power quality filter

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Figure 92: 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-L2). Note however that

this approach requires some experience.

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

8.6.2.3.1Measurement 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

the current should point towards the PQF. Do not forget to remove the shorts on

the CT secondary (if present) before making the measurement.

168 The PQF-Manager user interface ç Manual Power Quality Filter PQFM

(only shown for one phase)

(Figure

93)

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