Introduction: In earlier post, we have learnt about various parameters related to synchronization checks in electrical power syatem.
Click here for earlier post regarding synchronization check.
Now, we will see voltage waveforms if these parameters are varied. In all waveforms, Red and Blue are two voltages to be compared for check synchronization. Black is vector difference of Red and Blue.
1. Phase angle variation: Typical setting for phase angle difference is 15-30 deg. Two cases for 30deg and 60deg are shown below. The vector difference will be Sine of angle difference between two voltages. Therefore, for 30 deg it will be 0.5 and for 60 deg it will be 0.866
2. Voltage variation: Typical setting for voltage difference is 7.5 to 15%. Two cases for 10% and 20% are shown below. The vector difference will be same as difference between two voltages.
Click here for earlier post regarding synchronization check.
Now, we will see voltage waveforms if these parameters are varied. In all waveforms, Red and Blue are two voltages to be compared for check synchronization. Black is vector difference of Red and Blue.
1. Phase angle variation: Typical setting for phase angle difference is 15-30 deg. Two cases for 30deg and 60deg are shown below. The vector difference will be Sine of angle difference between two voltages. Therefore, for 30 deg it will be 0.5 and for 60 deg it will be 0.866
2. Voltage variation: Typical setting for voltage difference is 7.5 to 15%. Two cases for 10% and 20% are shown below. The vector difference will be same as difference between two voltages.
3. Frequency variation: Typical setting for voltage difference is +0.2 to +0.5%. Two cases for 5% and 10% are shown below. Case for higher frequency difference are choosen for proper visualization. Showing diagram for 0.5% frequency difference will require longer time scale and it would not be clear to visualize the diagram..
In the image below, the vector difference is gardually inreasing and decreasing at a frequency equal to frequency difference between two voltages. The CB has to be closed when voltage difference is at lower level. Therefore, if frequency difference is low, we have more time to close the CB. In the image below (for 5%), voltage is low for ~6 cycles, which would be ~120ms for 50Hz system. It will be impossible for operator to close CB in this short duration. In actual case the check sync setting will 10 times lower i.e. 0.5%, this will give operator a time of 1200ms (1.2 sec), which is sufficient for closing of CB.
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