High Voltage power frequency test transformers are required to produce single phase very high voltages.
Their continuous current ratings are very low, usually ≈ 1A. Even 1A is a very high current rating. This is because a HIV test transformer has to supply only the capacitive charging current to the capacitance formed by the dielectric of the test object.
However, since the voltage rating requirements are high, the test transformers are required to be produced with very high insulation level.
This increases the size of the test sets tremendously. Hence, single units of test transformers areproduced maximum up to 700kV.
