Application - ABB RELION 620 Series Technical Manual

Section 4
Protection functions
4.1.7.5
236
"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 trip time setting. For more information, see the
IDMT curves for overcurrent protection
The timer calculates the pickup duration value PICKUP_DUR, which indicates the
percentage ratio of the pickup situation and the set trip time. The value is available in the
monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in 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 protection relay's
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, but the TRIP output is not deactivated when
blocking is activated. In the "Block all" mode, the whole function is blocked and the timers
are reset. In the "Block TRIP output" mode, the function operates normally but the TRIP
output is not activated.

Application

Since the negative sequence current quantities are not present during normal, balanced
load conditions, the negative sequence overcurrent protection elements can be set for
faster and more sensitive operation than the normal phase-overcurrent protection for fault
conditions occurring between two phases. The negative sequence overcurrent protection
1MAC504801-IB E
section in this manual.
620 series ANSI
Technical Manual