6.13.202.2 Specific marking of the rating plate of a measuring current transformer
The accuracy class and instrument security factor (if any) shall be indicated following the indication of the corresponding rated output.
EXAMPLE 1 15 VA cl. 0.5
EXAMPLE 2 15 VA cl. 0.5 FS 10
Current transformers having an extended current rating (see 5.6.201.5) shall have this rating indicated immediately following the class designation.
EXAMPLE 3 15 VA cl. 0.5 ext.150 % FS 10
For current transformers having an extended burden range (see 5.6.201.4), this rating shall directly precede the class indication.
EXAMPLE 4 1-10 VA class 0.2 (meaning burden range from 1 to 10 VA at class 0.2)
NOTE The rating plate may contain information concerning several combinations of ratios, burdens and accuracy classes that the transformer can satisfy at the same ratio. In this case, non-standard values of burden may be
used.
EXAMPLE 15 VA class 1; 7 VA class 0,5
6.13.202.3 Specific marking of the rating plate of a class P protective current transformer
The rated accuracy limit factor shall be indicated following the corresponding rated output and accuracy class.
EXAMPLE 30 VA class 5P10
6.13.202.4 Specific marking of the rating plate of class PR protective current transformers
The rated accuracy limit factor shall be indicated following the corresponding rated output and accuracy class.
EXAMPLE 1 10 VA class 5PR10
If specified, the following parameters shall also be indicated:
– the secondary loop time constant;
– the upper limit of the secondary winding resistance;
6.13.202.5 Specific marking of the rating plate of class PX and PXR protective
current transformers
The class requirements may be indicated as follows:
– the rated turns ratio
– the rated knee point e.m.f.;
– the upper limit of exciting current at the rated knee point e.m.f. and/or at the stated percentage thereof;
– the upper limit of secondary winding resistance.
If specified, the following parameters shall also be indicated:
– the dimensioning factor;
– the rated resistive burden.
6.13.202.6 Specific marking of the rating plate of current transformers for transient performance
The class marking consists of the following 2 elements:
a) Definition part (compulsory)
The definition part contains the essential information which is necessary to determine whether the current transformer fulfils given requirements (consisting of duty cycle).
b) Complementary part (compulsory only if a duty cycle is specified by the customer)
The complementary part represents one of many possible duty cycles which lead to the value specified in a).
7 Tests
7.1 General
7.1.2 Lists of tests
Table 10 of IEC 61869-1:2007 is replaced by new Table 10.
Table 11 of IEC 61869-1:2007 is applicable with the addition of the following text:
For GIS current transformers, the accuracy tests may be performed without insulating gas.
7.2 Type tests
7.2.2 Temperature-rise test
IEC 61869-1:2007, 7.2.2 is applicable with the following additions:
7.2.2.201 Test set up
The current transformer shall be mounted in a manner representative of the mounting in service and the secondary windings shall be loaded with the burdens according to 6.4.1.
However, because the position of the current transformer in each switchgear installation can be different, the test setup arrangement is left to the manufacturer.
For current transformers in three phase gas-insulated metal enclosed switchgear, all three phases have to be tested at the same time.
7.2.2.202 Measurement of the ambient temperature
The sensors to measure the ambient temperature shall be distributed around the current transformer, at an appropriate distance according to the current transformer ratings and at about half-height of the transformer, protected from direct heat radiation.
To minimise the effects of variation of cooling-air temperature, particularly during the last test period, appropriate means should be used for the temperature sensors such as heat sinks with a time-constant approximately equal to that of the transformer.
The average readings of two sensors shall be used for the test.
