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Analyzes and evaluations of example power quality recording performed with SONEL PQM series analyzers
OPERATION OF THE POWER GENERATOR
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The good power quality also means the lack of interruptions in the supply of electricity. Of the available solutions, diesel generators are the most widely used. They allow you to secure the continuity of power supply both during temporary failures and long-term interruptions occurring in energy distribution systems. Due to temporary working conditions, the EN 50160 standard provides for separate quality parameters in island operation.
Description of the identified problem The generator works in a continuous mode supplying a fragment of a sensitive and restless technological process. The impact of the suddden change of loads on the generator's operation and important quality parameters of the power supply should be assessed. The analysis was performed on the basis of a 24-hour slice recording of a typical production period.
Measuring equipment used PQM-702 Power Quality Analyzer F-1A flexible current probes Sonel Analysis software
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Fig. 1. Picture of voltages and currents during generator operation
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Fig. 2. The image of frequency against the background of currents during generator operation
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Fig. 3. The voltage diagram for the operation of the power generator
Initial conclusions 1. The variation in load (See 1 and 2) has a visible effect on the grid frequency caused by the variation in rotation speed (See 3 and 4). 2. Rotation changes additionally cause visible effects of voltage fluctuations (See 4.).
Unusual observations Fluctuations in RMS voltage values may be caused by a change in frequency. Another reason may be the association of the signal variation period with the averaging time in the meter, combined with rapid changes in the voltage and current waveforms. This can create a non-intuitive picture of the situation.
OPERATION OF THE POWER GENERATOR
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OPERATION OF THE POWER GENERATOR
8
Observed voltage surge events (See 5.) are a mathematical effect in which the RMS value represents the signal energy and not the instantaneous levels, which is seen in connection with the instantaneous values waveform (See 6.).
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Fig. 4. RMS 20ms (1/2) image of the phase voltages and currents of the voltage increase event during generator operation
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Fig. 5. Oscillographic image of phase voltages and currents of the voltage increase event during generator operation
Fig. 6. The fragmentary image of the frequency and phase voltages during generator operation
Fig. 7. A fragmentary image of changes in phase voltages as a result of rapid load changes during generator operation
Conclusions 1. Fluctuations in the RMS voltage value (Fig. 6) may be caused by a change in frequency and the association of the variation period with the averaging time, as well as a non-periodic change in the voltage and current waveforms, which may result in a non-intuitive picture of the situation. 2. The generator is not a very "rigid" power source, therefore step load changes can cause large voltage dips and changes in the network frequency, related to the engine rotation speed (Fig. 6.). 3. Interpretation of events related to exceeding the RMS value requires additional analysis of the waveforms showing the actual behavior of the signals.
OPERATION OF THE POWER GENERATOR
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