Operation Manual

MI 2092 Power Harmonics Analyser Section VI Theory of operation

Section VI Theory of operation

1. General

Data recording is one of the main functions of the instrument. However, while recording

data for later analysis, the Instrument can also carry out the following functions:.

· Statistical analysis – Statistical analysis of the measured signals.

· Periodic analysis – On line recording and analysis of various measured

signals over preset periods.

· Voltage anomalies - Detection and recording of voltage anomalies.

· Power breaks – Detection and recording of supply interruptions.

Apart from power break recording, which is always enabled, all the other functions are

independent and can be disabled or enabled by the user. The measuring principles are

the same in all recording functions and are described in Section II-2 below. Averaging

and statistical techniques are described later in this section.

Data is stored in non-volatile memory and can be download to a PC for further analysis

and printing. Downloading can be carried out either on-line while recording and / or after

recording has finished. Independent of the recording status, the Instrument can send all

samples of an input signal to a PC (for external analysis and viewing) every second.

2. Statistical analysis

The input range (from 0 to full scale) for each value is divided in 256 divisions

(100 for PF and cosj). Measured values are scaled accordingly. The result is a

statistical table, a Gaussian function, that can be analysed using the PC software

(see section V below). Statistical analysis is carried out only on signals selected

in the Signals submenu.

Statistical analysis cannot be applied to Harmonic measurements.

3. Periodic analysis

Periodic Analysis is carried out over a programmable integration period (IP). This can

be set (from 1 second to 30 minutes) by the user. During the integration period, the

instrument calculates maximum, minimum and average values of selected quantities. At

the end of the Period, these values are stored in memory together with the Period Start

date/time and synchronization input.

Stored values differ for the various parameters:

· For THD measurement Only maximum and average values.

· For voltage harmonics and

voltage-current angle Only maximum and minimum values.

· For current harmonics Only maximum values.

· All other Parameters Minimum, maximum and average.