Like AC Electrical Generators Synchronization, What is Transformers Synchronization? What are the Electrical Parameters to be considered?

for transformer synchronization or parallel connection:

1. Same terminal voltage

2. Same frequency

3. Same phase sequence

4. same vector diagram

Tranformers should have the same voltage, and also frequency. It is important that they are more or less the same rating in term of current carrying capacity, impedance and the same type, e.g. both must be autotransformers. This is often used in ring feed reticulation feeders.

Transformers synchronization is the working parallel of two or more power tranformers.

All the transformers synchronized shall have the same powers, same voltages , same internal resistances , same ratios , same vektors and in addition to that for the best result , they shall have identical test results which can be achieved only with the same manufacturer.

same voltage ratio

identical position of tap chanager

same impedance ratio

same freequency

same polarity

same vector 

same terminal voltage

Same voltage ratio

Same per unit (pu) impedance

Same polarity of all connected transformers

Same phase sequence

Equal short-circuit impedances

Transformer are energized , a running generators are synchronized ,for e.g in a loop in loop out66/11 KV primary SS with66 kv GIS-Bus /Bay, there are NOSP clearance check list is added auxillary from local battery room is purt on for parameters monitoring before breaker on sequence begin those are many points starting from oil levels for any leakage , HV testing report re confirmation , remote end modification relay setting confirmation etc the sequence is incoming feeder on , followed by GIS bay energization from bay to transformer energization and then from transfore to11 kv switchgear energizatuion ..it involves imense checks and rechecks , transformers are never connected to GRID they are connected to local GIS/other Bus and bus is connected to next transmission lines or substation ,various countries like INDIA have HVDC direct transmission which is differant special equipments and differant type of transforemers  . Even generating station transformers are of special construction u can read on google or refer NEC-450