The effect of DC offset on current-operated relays

Author

Stringer, Norman T.

Author_Institution

Basler Electr. Co., Houston, TX, USA

Volume

34

Issue

1

fYear

1998

Firstpage

30

Lastpage

34

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 system, can produce saturation in the 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 current transformer 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; electrical faults; power system protection; power system relaying; power transformers; relay protection; transformer windings; DC offset; L/R time constant; current transformer saturation; current-operated relays; fault sensing; power system faults; power system relay protection; protective relays; transformer secondary; Circuit faults; Coils; Current transformers; Fault currents; Power system protection; Power system relaying; Protective relaying; Relays; Switches; Voltage;

fLanguage

English

Journal_Title

Industry Applications, IEEE Transactions on

Publisher

ieee

ISSN

0093-9994

Type

jour

DOI

10.1109/28.658712

Filename

658712