Current ratios from 60 A up to 1000 A (primary side) and 1 A or 5 A (secondary side) The transformer’s accuracy permits extremely precise current measurements. High quality current transformer factory include 5 amp secondary, high turns ratio voltage outputs for both wire leads and pcb configurations.
This includes ANSI, Commercial, Ground Fault, High Frequency, Wound Primary, DC Immune and Nano Alloy current transformers. The STWA1H current transformer is made to match the current-relays for recognition of AC-current and for controls for deducting plants type STW. K.-L. Chen, R.-S. Wan, Y. Guo, N. Chen, W.-J. Lee, A redundancy mechanism design for Hall-based electronic current transformers, Energies 10 (2017) 1-14.
F.C.F. Guerra, W.S. Mota, Current transformer model, IEEE Transactions on Power Delivery, 22(1) (2007) 187-194. Current transformer error compensation unit (CTECU) Ratio error Phase angle error Digital compensation technique. Core-balance current transformer by Gilber and Maxwell transformers.
On-site conjunctive testing of current transformers and the apparatus that they energize is often required. The output current is reduced during transient saturation, which may prevent the relays from operating if the conditions are near to the relay setting This must not be confused with the increased r.m.s. value of the primary current due to the asymmetric transient, a feature which sometimes offsets the increase ratio error. The total exciting current during the transient period is of the form shown in Figure 13 and the corresponding resultant distortion in the secondary current output, due to saturation, is shown in Figure 14.
Exciting current is equal to the total asymmetric input current, since beyond this point the output current, and hence the voltage drop across the burden resistance, is negative. I’s = the actual secondary output current. From this it can be seen that the ratio of reactance to resistance of the power system is an important feature in the study of the behaviour of protection relays.
For the CT equivalent circuit, the voltage is the drop on the burden resistance Rb. Integrating for each component in turn, the steady state peak flux is given by: The power system, neglecting load circuits, is mostly inductive, so that when a short circuit occurs, the fault current that flows is given by: This is because the winding of the device has to develop a given number of ampere-turns at rated current, so that the actual number of turns is inversely proportional to the current, and the impedance of the winding varies inversely with the square of the current rating.
It is however, normally accepted that a current transformer is of the low reactance type provided that the following 4 conditions prevail: The ‘linear’ current transformer constitutes an even more radical departure from the normal solid core CT in that it incorporates an appreciable air gap, for example 7.5-10mm. However, the resulting decrease in possible remanent core flux confines any subsequent d.c. flux excursion, resulting from primary current asymmetry, to within the core saturation limits.