Monitoring of Angular Separation in Power system: Part 5

Second method which is used for power angle monitoring is synchrocheck relay or synchrocheck trolley. It is in general not directly used by control centers but extensively used by substation or power plant operators in the field.?Its major usage is described below:

1.????Synchronizing two power system islands running asynchronously

2.????Synchronizing two power systems after any blackout

3.????Synchronizing a generator with power system

4.????Closing of line within the power system safely within prescribed limits

5.????Paralleling of second tie line between two substations

These devices basically check the slip between the frequency on two systems and based on that provide the substation operator with a view of when to close the synchronizing breaker through which two systems will be synchronized/paralleled. ?For above mentioned activities, it is important to consider voltage, phase angle, phase rotation and frequency. ?The details of their importance can be seen in detail in the article provided under reference 2-5. It is worth mentioning that these are local type of devices, and such parameters are checked across the breaker through which two systems will be connected. Below provided figure provide the details on various types of synchronization activity.

Grid Operator coordinates with field operator and share instruction on the value of allowable voltage difference, phase angle difference and frequency difference depending on type of synchronization to ensure smooth synchronization. Substation operators set these values and close synchronizing breaker only when these criteria are satisfied. While power plant operator sets defined limits in auto-synchronizer which allows the generator to synchronize automatically when it satisfies voltage, phase angle rotation, phase angle difference and frequency difference criteria and ensures that there will not be any reverse power flow.

Any wrong synchronization where synchronization happens outside the set parameter limit can be disastrous for the power system as well equipment being synchronized. ?Synchronization with phase opposition (at 180 degrees) will like creating three phase faults across the synchronizing breaker. That’s why utmost precaution is taken along with various checks to ensure smooth synchronization occurs.

For further reading have a look at the below reference which discusses the various fundamentals, working principles for synchro check relay and synchronizer in detail.

Reference :

1. Remote Visualization of synchroscope using synchrophasors, https://www.researchgate.net/publication/345715070_Remote_Visualization_of_synchroscope_Using_synchrophasors
2. https://voltage-disturbance.com/power-engineering/understand-synchro-check-relay-for-source-paralleling/
3. Synchronism Check Equipment, GE Power Management https://www.gegridsolutions.com/products/applications/ger2622a.pdf
4. https://www.o-t-s.com/synchronizing.htm
5. https://steemit.com/steemstem/@thinkingmind/parallel-running-of-generators
6. https://electrical-engineering-portal.com/synchronisers-power-system-two-supplies