ABB RELION REX640 Technical Manual page 1255

Protection and control

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1MRS759142 F

underreaching function is connected to the CSUR input. The duration of the CSUR

input signal can be prolonged by the

duration of the CS_PRM signal.

In the permissive overreach scheme, the received signal CR_PRM or CRL, if

the unblocking function is enabled, is used to allow the overreaching residual

overcurrent function DEFLPDEF to trip (activation of the OPERATE output) after the

settable pick-up delay

zone is connected to the CACC input.

The CS_PRM signal is also generated if the CR_PRM signal is received and the local

carrier acceleration signal CACC is active.

Activating the BLOCK input totally blocks the permissive overreach scheme. The

CS_PRM and OPERATE outputs can be blocked by the BLK_CS_OPR input.

Figure 713: Simplified functional diagram of the permissive overreach scheme

Directional comparison blocking scheme DCB

The directional comparison blocking scheme is enabled with

In the blocking scheme, the START signal from the reverse-looking residual

overcurrent function DEFLPDEF set to operate for the reverse direction earth fault,

is connected to the CSBLK input to create a CS_BLOCKING signal. The starting of

the reverse-looking function indicates that the fault is located outside the protected

feeder. The duration of the CSBLK input signal can be prolonged with the

Dur setting to ensure a sufficient duration of the CS_BLOCKING signal.

The blocking scheme is mainly used to allow the forward-looking overreaching

residual overcurrent function to trip (activation of the OPERATE output) after the

Technical Manual

In case of parallel feeders, when the external current reversal logic

(RCRWPSCH) is enabled, the CS_PRM signal is not prolonged and the

Carrier Min Dur is set to zero to secure correct operation.

Coordination time . The start signal from the overreaching

Protection related functions

Carrier Min Dur setting to ensure a sufficient

Scheme type =