ABB RELION 611 Series Technical Manual page 235

1MRS757454 D
611 series
Technical Manual
The operation of NSPTOC can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
A070660 V1 EN
Figure 109: Functional module diagram
Level detector
The measured negative-sequence current is compared to the set Start value. If the
measured value exceeds the set Start value, the level detector activates the timer
module. If the ENA_MULT input is active, the set Start value is multiplied by the set
Start value Mult.
The protection relay does not accept the Start value or Start value Mult
setting if the product of the settings exceeds the Start value setting
range.
Timer
Once activated, the timer activates the START output. Depending on the value of the
Operating curve type setting, the time characteristics are according to DT or IDMT.
When the operation timer has reached the value of Operate delay time in the DT mode
or the maximum value defined by the inverse time curve, the OPERATE output is
activated.
When the user-programmable IDMT curve is selected, the operation time
characteristics are defined by the parameters Curve parameter A, Curve parameter B,
Curve parameter C, Curve parameter D and Curve parameter E.
If a drop-off situation happens, that is, a fault suddenly disappears before the operate
delay is exceeded, the timer reset state is activated. The functionality of the timer in
the reset state depends on the combination of the Operating curve type, Type of reset
curve and Reset delay time settings. When the DT characteristic is selected, the reset
timer runs until the set Reset delay time value is exceeded. When the IDMT curves are
selected, the Type of reset curve setting can be set to "Immediate", "Def time reset" or
"Inverse reset". The reset curve type "Immediate" causes an immediate reset. With the
reset curve type "Def time reset", the reset time depends on the Reset delay time
setting. With the reset curve type "Inverse reset", the reset time depends on the current
during the drop-off situation. The START output is deactivated when the reset timer
has elapsed.
Section 4
Protection functions
229