Figure. 5.4.1 - 22. Measurement range in relation to the nominal current.
The
I
n
magnitude refers to the user set nominal current which can range from 0.2…10 A, typically 0.2
A, 1A or 5 A. With its own current measurement card, the IED will measure secondary currents from
0.001 A up to 250 A. To this relation the pick-up setting in secondary amperes will vary.
Function blocking
The blocking signals are checked in the beginning of each program cycle. A blocking signal is received
from the blocking matrix for the function dedicated input. If the blocking signal is not activated when
the pick-up element activates, a START signal is generated and the function proceeds to the time
characteristics calculation.
If the blocking signal is active when pick-up element activates, a BLOCKED signal is generated and the
function will not process the situation further. If the START function has been activated before the
blocking signal, it resets and the release time characteristics are processed similarly to when the pick-
up signal is reset.
The blocking of the function causes an HMI display event and a time stamped blocking event with
information of the startup current values and its fault type to be issued.
The blocking signal can also be tested in the commissioning phase by a software switch signal when
the relay's common and global testing mode is activated.
The variables users can set are binary signals from the system. The blocking signal needs to reach the
IED minimum of 5 ms before the set operating delay has passed in order for the blocking to activate in
time.
Operating time characteristics for trip and reset
The operating timers’ behavior during a function can be set for trip signal and for the release of the
function in case the pick-up element is reset before the trip time has been reached. There are three
basic operating modes available for the function:
• Instant operation: activates the trip signal with no additional time delay simultaneously with
the start signal.
• Definite time operation (DT): activates the trip signal after a user-defined time
delay regardless of the measured current as long as the current is above or below the
X
set
value and thus the pick-up element is active (independent time characteristics).
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
IM00021
57
Summary of Contents for AQ-M257
Page 1: ...AQ M257 Motor protection IED Instruction manual...
Page 2: ......
