3.4.205
instrument security factor
ratio of rated instrument limit primary current to the rated primary current
Note 1 to entry: Attention should be paid to the fact that the actual instrument security factor is affected by the burden. When the burden value is significantly lower than rated one, larger current values will be produced on the secondary side in the case of short-circuit current.
Note 2 to entry: In the event of system fault currents flowing through the primary winding of a current transformer, the safety of the apparatus supplied by the transformer is at its highest when the value of the rated instrument security factor (FS) is at its lowest.
[SOURCE: IEC 60050-321:1986, 321-02-28, modified notes to entry]
3.4.206
secondary limiting e.m.f. for measuring current transformers
product of the instrument security factor FS, the rated secondary current and the vectorial sum of the rated burden and the impedance of the secondary winding
This method will give a higher value than the actual one. It was chosen in order to apply the same test method as
used for protective current transformers. Refer to 7.2.6.202 and 7.2.6.203.
[SOURCE: IEC 60050-321:1986, 321-02-31, modified title, synonym and note to entry]
3.4.207
rated accuracy limit primary current
value of primary current up to which the current transformer will comply with the requirements for composite error
[SOURCE: IEC 60050-321:1986, 321-02-29]
3.4.208
accuracy limit factor
ratio of the rated accuracy limit primary current to the rated primary current
[SOURCE: IEC 60050-321:1986, 321-02-30]
3.4.209
secondary limiting e.m.f. for protective current transformers
product of the accuracy limit factor, the rated secondary current and the vectorial sum of the rated burden and the impedance of the secondary winding
3.4.210
saturation flux
maximum value of secondary linked flux in a current transformer, which corresponds to the magnetic saturation of the core material
Note 1 to entry: The most suitable procedure for the determination of the saturation is given with the d.c. saturation method described in 2B.2.3.
Note 2 to entry: In the former standard IEC 60044-6, it was defined as a knee point value, which characterized the transition from the non-saturated to the fully saturated state of a core. This definition could not gain acceptance because the saturation value was too low, and led to misunderstandings and contradictions. Therefore, it was replaced by it which defines the condition of complete saturation.
3.4.211
remanent flux
value of secondary linked flux which would remain in the core 3 min after the interruption of a magnetizing current of sufficient magnitude to induce saturation flux
3.4.212
remanence factor
ratio of the remanent flux to the saturation flux, expressed as a percentage
3.4.213
secondary loop time constant
value of the time constant of the secondary loop of the current transformer obtained from the sum of the magnetizing and the leakage inductances and the secondary loop resistance
3.4.214
excitation characteristic
graphical or tabular presentation of the relationship between the r.m.s. value of the exciting current and a sinusoidal voltage applied to the secondary terminals of a current transformer, the primary and other windings being open-circuited, over a range of values sufficient to define the characteristics from low levels of excitation up to 1.1 times the knee point e.m.f.
