Mathematical models for current, voltage, and coupling capacitor voltage transformers

Abstract

This paper reviews a number of mathematical models used to represent the nonlinear behavior of the magnetic core of instrument transformers. Models of instrument transformers using these core representations are presented. The transient response of the instrument transformer is compared to actual test results recorded in the laboratory. The paper provides practical guidelines as to which of the physical elements of instrument transformers are important to model during transient studies and which elements could be ignored without sacrificing the accuracy of the simulation results. The electromagnetic transients program (EMTP) data files used to generate the models are also provided in the appendix to help new EMTP users model instrument transformers for evaluation of high-speed protective relaying systems.

Novel principle and adaptive scheme of phase correlation line current differential protection

“…Here, the length of transmission line is 100 km, the system equivalent impedances of the two side power systems are given in Table I. 1200:5 CT model has been simulated in EMTDC for obtaining realistic CT response to faults [25]. The protection schemes are applied and tested on the line L 2 .…”

Selection of minimal tripping times for distance protection using fault trees with time dependencies

“…The instrument transformers have been modeled in accordance with generally accepted rules [21]. Thus, transients in current transformers resulting from core saturation and transients in capacitive voltage transformers due to discharging of the capacitive elements have been taken into account.…”

Adaptive Current Differential Protection Schemes for Transmission-Line Protection

“…The Type-98 model requires nonlinear characteristics of the CT core. To convert the excitation curve specified by pairs, the methodology described in [28], [29] is used. The CT model data have been given in Table I.…”