phase angle setting for synchrocheck relay

[falsam]

In a secodary selective system, what shall be the maximum phase angle setting of synchrocheck relay used for paralleling two incomers without creating any disturbance in the system. What are the factors which govern this setting?
In fact, when both the transformers whose secondaries are to be paralleled have same MVA, %impedance and vector group, there should not be much of a difference in phase angle.

 

[Shortstub]

Only if supplied from same upstream source!

 

[RajT]

If both the transformer incomers are fed from the same source upstream then both the supplies should be in synch and thus a check synch relay is not really required.
If however in the event that the supplies are fed from two different sources (or if in doubt) then a check synch realy would be required. The setting may be (in your case) say 5degs as it would simply act as a permissive gate signal (allowing paralleling)since you are unable to control either the freq or the volts.

 

[Shortstub]

In the HPI company I was with, common practice for a secondary-selective substation with automatic transfer, was to provide just phase and voltage checks, but, only if normally-synchronized sources were occasionaly unsynchronized. The settings were:

o Phase angle, +/- 25 Deg.

o Voltage Difference, 80-90%.

A frequency-check was added if one of the sources came from local generation! If the installation was in a location where the frequency check feature was unavailable, then a timer was incorporated with the phase-angle check feature!