Abstract:

Taking an abnormal alarm of TV for a 220kV main transformer protection as an example, it is found that excessive third harmonic is a cause for abnomal TV.Furthermore,when a harmonic elimination is equipped at the TV neutral point, it can produce voltage and third harmonics in the zero sequence opendelta connection, causing abnormal alarm of TV for  main transformer protection.Corresponding methods are put forward to ensure the safe and stable operation of the main equipment of substation.

Key words:

abnormal alarm of TV, protection of main transformer, third harmonics, secondary voltage；harmonic elimination