Stabilized And Instantaneous Differential Protection For Two-Winding; Transformers Tr2Ptdf (Ansi 87T) - ABB RELION REX640 Technical Manual

Protection and control

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Table of Contents

Protection functions

Characteristics

Operate time accuracy in definite

Operate time accuracy in inverse

Suppression of harmonics

Stabilized and instantaneous differential protection for

two-winding transformers TR2PTDF (ANSI 87T)

Identification

Function description

Stabilized and instantaneous differ-

ential protection for two-winding

transformers

Function block

Figure 386: Function block

Functionality

The stabilized and instantaneous differential protection for two-winding

transformers function TR2PTDF is designed to protect two-winding transformers

and generator-transformer blocks. TR2PTDF includes low biased and high

instantaneous stages.

The biased low stage provides a fast clearance of faults while remaining stable

with high currents passing through the protected zone increasing errors on current

measuring. The second harmonic restraint, together with the waveform based

algorithms, ensures that the low stage does not operate due to the transformer

inrush currents. The fifth harmonic restraint ensures that the low stage does not

operate on apparent differential current caused by a harmless transformer over-

Low operate value multiples in the range of 1.5...20

±1.0% of the set value or ±20 ms

±5.0% of the set value or ±20 ms

RMS: No suppression

DFT: -50 dB at f = n × fn, where n = 2, 3, 4, 5,...

Peak-to-Peak: No suppression

identification

1MRS759142 F

ANSI/IEEE C37.2

device number

Technical Manual