Figure. 5.3.1 - 13. Inverse operating time formulas for IEC and IEEE standards.
Non-standard delay characteristics
In addition to the previously mentioned delay characteristics, some functions also have delay
characteristics that deviate from the IEC or IEEE standards. These functions are the following:
• overcurrent stages
• residual overcurrent stages
• directional overcurrent stages
• directional residual overcurrent stages.
The setting parameters and their ranges are documented in the chapters of the respective function
blocks.
Table. 5.3.1 - 27. Inverse operating time formulas for nonstandard characteristics.
RI-type
RD-type
Used to get time grading with
mechanical relays
Mostly used in earth fault protection which grants selective tripping even in non-
directional protection
t = Operating delay (s)
k = Time dial setting
I
m
= Measured maximum current
I
set
= Pick-up setting
t = Operating delay (s)
k = Time dial setting
I
m
= Measured maximum current
I
set
= Pick-up setting
A
AQ
Q-T256
-T256
Instruction manual
Version: 2.06
36
© Arcteq Relays Ltd
IM00028
Summary of Contents for AQ-T256
Page 1: ...AQ T256 Transformer protection IED Instruction manual...
Page 2: ......
