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Transformers neutral grounding accessing small reactance is an effective measure to restrain short circuit current in 500kV power grid. But accessing small reactance will bring changes to the zero-sequence parameters of system. The relay protection, especially the main transformer protection and transmission line protection nearby will be affected and act incorrectly when unsymmetrical earth fault...
The single-phase grounding fault line selection in the distribution network has always been an outstanding problem of power system relay protection. One of the key reasons for fault line selection difficulty is that the fault current is correspondingly too weak to be detected effectively for the small current grounding system which is widely adopted in our distribution networks. The paper mainly discusses...
This paper attempts to use a novel algorithm of traveling wave caused by the transient condition and the sudden change of the point of failure when traveling wave invades the transformer substation, gain the polar and amplitude characteristic of current front traveling wave in various lines, constitute line selection protection algorithm, complete line selection of single-phaseground fault in the...
Closing a transformer without load will lead to the emergence of sympathetic inrush current in adjacent transformer. Sympathetic inrush current always causes mal-operation of protective relay and harmonic over-voltage. Based on simplified equivalent circuit of two shunt-wound transformers, the magnetic analytical expression and rule of bias magnet attenuation are analyzed. After that, the reasons...
Widespread use of digital distance relays has increased the application of distance protection to lower voltages, including subtransmission and distribution circuits. Many systems may be impedance grounded. In this paper, we look at some unique problems that may arise on single-source, distribution systems, such as might occur at the 26-kV voltage level. A source of concern for distance relays on...
The purpose of this paper is to provide a tutorial or "refresher" on grounding methods, sources of ground current, ground current flow in the power system, and how each impacts protective relaying. With retirements, new hires, reorganization, cross training, and so on, this subject, like many others, requires regular review to maintain the experience level of our protection engineers and...
Questions of duration operate of resistor for neutral grounding is equipped. Two main mode of resistors operate are considered. Practical recommendations of selection values of resistors value for this mode are given.
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