ABB RELION 620 Series Technical Manual page 321

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1MAC504801-IB E

620 series ANSI

Technical Manual

GUID-1F833D04-EA04-427E-BC3D-2BFE5E694FFC V1 EN

Functional module diagram

Level detector

The fundamental frequency component of the measured three-phase voltages over the

range of 10...70 Hz is compared phase-wise to the set Pickup value . If the measured value

is lower than the set value of the Pickup value setting, the Level detector enables the phase

selection logic module. The Relative hysteresis setting can be used for preventing

unnecessary oscillations if the input signal slightly varies above or below the Pickup value

setting. After leaving the hysteresis area, the pickup condition has to be fulfilled again and

it is not sufficient for the signal to only return back to the hysteresis area.

The Voltage selection setting is used for selecting the phase-to-earth or phase-to-phase

voltages for protection.

Phase selection logic

If the fault criteria are fulfilled in the Level detector, the phase selection logic detects the

phase or phases in which the fault level is detected. If the number of faulty phases match

with the set Num of pickup phases, the phase selection logic activates the Timer.

Once activated, the Timer activates the PICKUP output. The time characteristic is definite

When the trip timer has reached the value set by Trip delay time, the TRIP output is

In a drop-off situation, that is, when a fault suddenly disappears before the trip delay is

exceeded, the reset state is activated. The reset timer runs until the set Reset delay time

value is exceeded. If the drop-off situation exceeds the set Reset delay time, the Timer is

reset and the PICKUP output is deactivated.

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

Protection functions

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