THEORY OF OPERATION. 
 
GENERAL. 
 
Data recording is one of the main functions. However, while recording data for later analysis, the 
instrument can also carry out the following functions: 
 
1. Statistical analysis - statistical analysis of the measured signals. 
 
2. Periodic analysis - On line recording and analysis of various measured signals over preset 
periods. 
 
3. Voltage anomalies - Detection and recording of voltage anomalies. 
 
4. Power breaks - Detection and recording of supply interruptions. 
 
5. Waveforms 
 
6. Fast logging 
 
7.Transients 
 
8. Flickers 
 
9. EN 50160 
 
Apart from power break recording, which is always enabled, all the other functions are the same in all- 
recording functions. 
 
1. STATISTICAL ANALYSIS 
 
The input range (from 0 to full scale) for each value is divided in 256 divisions (100 for PF and cos φ). 
Measured values are scaled accordingly. The result is a statistical table, a Gaussian function, which can 
be analysed using the PC software. Statistical analysis is carried out only on signals selected in the signals 
submenu. Statistical analysis cannot be applied to Harmonic measurements. 
 
2. PERIODIC ANALYSIS 
 
Periodic analysis is carried out over a programmable integration period(IP) It can be from 1s to 15min. 
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 (total harmonic distortion) 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) 
 
Active power is divided into two quantities: Import (positive) and Export (negative). Reactive power and 
power factor are divided into four quantities : positive inductive (+i), positive capacitive (+c), negative 
inductive (-i and negative capacitive (-c). Neutral conductor current (I0) is ignored when measuring in 3- 
wire connection. 
 
For power, voltage and current measurements, values are stored for each input cycle. Harmonics and 
THD values are computed on samples of each 8th input cycle. 
 
For calculation of Average Voltage, voltages less then 2% of full scale (0.02 x Un) are treated as voltage 
interruptions and are excluded from any calculations. 
 
The stored maximum and minimum values are based on values calculated during each input cycle, while 
average values (except for voltage, power & harmonics) are calculated at the end of each IP and are 
based on the number of input cycles in the period. 
 
Average values for power, voltage and harmonic components ignore input cycles where the voltage is 
lower than 0.02 x Un. Further, if a Power Break or a Power Up occurs during an IP or the IP starts during 
a Power Break, the instrument will start a new cycle. 
 
When measuring Power and Power Factor, values can be calculated for each individual cycle or averaged 
over a period (the 'Power sub IP') that can be set to any value between 1 and 20 cycles (a 400 ms 
window at 50Hz). 
 
If the instrument is recording a power, it automatically calculates and records the energy of the selected 
power in an IP. 
 
Values used for the calculation of maximum and minimum Powers and Power Factors are the average 
values calculated on power sub IP values. 
 
Recording of voltage or current THD is automatically enable if one or more individual voltage or current 
harmonics are selected. 
 
3. VOLTAGE ANOMALY RECORDING 
 
Voltage anomalies occur when a voltage exceeds preset boundaries. The rms voltages of each half input 
cycle are used for comparison. For every Voltage Anomaly detected, the Instrument stores : 
 
- Date & time when the anomaly started. 
 
- The nominal voltage. 
 
- Minimum or maximum voltage during the anomaly. 
 
- The previous 64 rms values, calculated on half input cycles (half periods), before the anomaly 
occurred. 
 
Voltage Anomaly recording is enabled on selected voltage inputs and can be calculated based either on 
a fixed tolerance window or on a variable tolerance window. 
 
Fixed Tolerance Mode 
 
The nominal voltage is set by the user, and the high and low limits are set as a percentage of the 
nominal voltage. 
 
Variable Tolerance Mode 
 
The nominal Voltage is calculated and is the average voltage during the previous anomaly integration 
period (settable between 1 and 900s). The new nominal reference voltage can be up the +- 30% of the 
programmed nominal voltage. High and low limits are set as a percentage of the nominal voltage and 
can be between +- 1% and +-30% of the nominal voltage. 
 
4. POWER BREAKS RECORDING 
 
If data logging is in progress, the start of every OFF state of the instrument is treated as a Power Break. 
This OFF state occurs either if the instrument is switched OFF or if it loses its power supply, either 
battery or mains. 
 
For each Power Break, the instrument logs the date & time of both the beginning and end of the power 
break, and the cause of the power break (manual or loss of supply). 
 
5. WAVEFORMS 
 
Waveform measurement is a powerful tool for troubleshooting and capturing current and voltage 
response in a switching situation. Waveform method saves waveforms of selected inputs on a trigger 
occurrence. the trigger can be set manually, by timer or when half-period RMS value of selected trigger 
input rises/falls above/below a trigger level. Selected pre- and post- trigger periods expressed in periods 
of power frequency or in seconds are stored in the instrument's memory. Each saved period in a 
waveform record consists of 128 sampled values. 
 
6. FAST LOGGING 
 
Fast logging is a measurement similar to a waveform recording but instead of storing 64 points in a 
wave half-period only the RMS value of the particular half-period is saved. In this case only 1/64 of 
the memory is spent on a record data. Triggering and signal selection are the same as for waveform 
recording. 
 
7. TRANSIENTS 
 
Transient is a term for Short, highly damped momentary voltage or current disturbance. There are two 
types of transient overvoltages : 
 
- impulsive overvoltages 
 
- oscillatory overvoltages 
 
Transient recording is the measurement method with the fastest sampling rate that the instrument can 
provide. Up to 25 kHz signals can be captured in this mode of operation. 
 
The Principle of measurement is similar to waveform recording, but with a higher sampling rate. With 
 
single signal enabled for capturing, there are 1000 samples in a 50 Hz signal period. When all six signals 
are enabled, 400 samples per period per signal are stored in the instrument memory. 
 
8. FLICKERS 
 
Flicker is a visual sensation caused by unsteadiness of a light. The level of the sensation depends on the 
frequency and magnitude of the lighting change and on the observer. 
 
Flickers are measured in accordance with standard IEC 61000-4-15 "Flicker meter-functional and design 
specifications". It defines the transform function based on a 230V/60W lamp-eye-brain chain response. 
That function is a base for flicker meter implementation. 
 
9. EN50160 
 
Standard EN50160 "Voltage characteristic of electricity supplied by public distribution systems" is 
a standard that defines the voltage characteristics of a Low voltage (LV) and Medium voltage (MV) 
distribution system. It is used as a base for utility-client contracts in the European Union and for small 
power generation contracts. 
 
The measurement procedure is very simple : one must connect the voltage of all 3 phases to an 
instrument, choose "EN50160" measurement and measurement can start. All parameters except time of 
the beginning and end of recording are automatically set. Start and stop time can be set or manual start- 
stop sequence must be performed over a one week period.
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