Omicron CP TD1 Reference Manual

CP TD1 Reference Manual V 1.44
132
12.3 Two- and Three-Winding Transformer Tests (IEEE
C57.12.90)
a)
In this table the term guard signifies one or more conducting elements arranged and connected to
Method I
Test without guard circuit
a
Method II
Test with guard circuit
a
Two-winding transformers
b
Two-winding transformers
b
High to low and ground High to low and ground
Low to high and ground High to ground, guard on low
High and low to ground Low to high and ground
⎯ Low to ground, guard on high
Three-winding transformers Three-winding transformers
High to low, tertiary, and ground High to low and ground, guard on tertiary
Low to high, tertiary, and ground High to ground, guard on low and tertiary
Tertiary to high, low, and ground Low to tertiary and ground, guard on high
High and low to tertiary and ground Low to ground, guard on high and tertiary
High and tertiary to low and ground Tertiary to high and ground, guard on low
Low and tertiary to high and ground Tertiary to ground, guard on high and low
High, low, and tertiary to ground
High and low to tertiary and ground
High and tertiary to low and ground
Note 1: While the real significance that can be attached to the power factor of liquid-immersed
transformers is still a matter of opinion, experience has shown that power factor is helpful
in assessing the probable condition of the insulation when good judgement is used.
Note 2: In interpreting the results of power-factor test values, the comparative values of tests taken
at periodic intervals are useful in identifying potential problems rather than an absolute
value of power factor.
Note 3: A factory power-factor test will be of value for comparison with field power-factor
measurements to assess the probable condition of the insulation. It has not been feasible
to establish standard power-factor values of liquid-immersed transformers for the following
reasons:
a) Experience has indicated that little or no relation exists between
the power factor and the ability of the transformer to withstand the
prescribed dielectric tests.
b) Experience has shown that the variation in power factor with
temperature is substantial and erratic so that no single correction
curve will fit all cases.
c) The various liquids and insulating materials used in transformers
result in large variations in insulation power-factor values.

Omicron CP TD1 Specifications

General

Brand	Omicron
Model	CP TD1
Category	Measuring Instruments
Language	English