The effect of DC offset on current operated relays

Author

Stringer, Norman T.

Author_Institution

Basler Electr. Co., Highland, IL, USA

fYear

1997

fDate

11-16 May 1997

Firstpage

154

Lastpage

159

Abstract

When a fault occurs on a power system, one or more phases will experience DC offset. This DC component, which will decay dependent on the L/R time constant of the power system, can produce saturation in current transformers, as well as the input current transformers of the protective relays sensing the fault. In addition, when the fault current is interrupted, the resulting DC tail can maintain the current above the relay´s pickup setting for a time dependent on the CT secondary circuit L/R time constant. This paper discusses this phenomenon and how it can affect the operation of two types of current operated relays

Keywords

current transformers; fault currents; power system protection; power system relaying; power transformer protection; relay protection; DC offset; DC tail; L/R time constant; current operated relays; current transformer saturation; power system protective relays; transformer secondary circuit; Circuit faults; Coils; Current transformers; Fault currents; Power system protection; Power system relaying; Protective relaying; Relays; Switches; Voltage;

fLanguage

English

Publisher

ieee

Conference_Titel

Industrial and Commercial Power Systems Technical Conference, 1997. Conference Record, Papers Presented at the 1997 Annual Meeting., IEEE 1997

Conference_Location

Philadelphia, PA

Print_ISBN

0-7803-3825-1

Type

conf

DOI

10.1109/ICPS.1997.596025

Filename

596025