ABB RER620 Technical Manual page 92

Section 4
Protection functions
86
When the user programmable IDMT curve is selected, the operate 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 trip 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. If
the drop-off situation continues, the reset timer is reset and the PICKUP output is
deactivated.
The "Inverse reset" selection is only supported with ANSI or user
programmable types of the IDMT operating curves. If another operating
curve type is selected, an immediate reset occurs during the drop-off
situation.
The setting Time multiplier is used for scaling the IDMT trip and reset times.
The setting parameter Minimum trip time defines the minimum desired trip time for IDMT.
The setting is applicable only when the IDMT curves are used.
The Minimum trip time setting should be used with great care because the
operation time is according to the IDMT curve, but always at least the value
of the Minimum operate time setting. For more information, see the
General function block features section in this manual
The timer calculates the pickup duration (PICKUP_DUR) value which indicates the
percentual ratio of the pickup situation and the set trip time. The value is available through
the Monitored data view.
Blocking logic
There are three operation modes in the blocking functionality. The operation modes are
controlled by the BLOCK input and the global setting "Configuration/System/Blocking
mode" which selects the blocking mode. The BLOCK input can be controlled by a binary
input, a horizontal communication input or an internal signal of the relay program. The
influence of the BLOCK signal activation is preselected with the global setting Blocking
mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode, the
trip timer is frozen to the prevailing value. In the "Block all" mode, the whole function is
blocked and the timers are reset. the "Block TRIP output" mode, the function operates
normally but the TRIP output is not activated.
1MAC309294-MB F
RER620
Technical Manual