ABB RELION REX640 Technical Manual page 664

Protection and control

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Protection functions

transferring the possible additional blocking information between the local and

remote terminals whenever the blocking logic behavior needs to be the same on

both line ends.

The line differential function in one protection relay can be set to test mode, that

protection outputs in the protection relay and sets the remote protection relay to a

remote test mode, such that the injected currents are echoed back with the shifted

phase. It is also possible that both protection relays are simultaneously in the test

mode. When the line differential protection function is in the test mode:

• The remote end protection relay echoes locally injected current samples back

with the shifted phase. The current samples that are sent to the remote

protection relay are scaled with the CT ratio correction setting.

• The operation of both stages (stabilized low or instantaneous high) are blocked,

and also the direct inter-trip functionality is blocked (both receive and send) in

the protection relay where the test mode is active.

• The remote end line differential protection function that is in the normal mode

(On) is not affected by the local end being in the test mode. This means that the

remote end function is operative but, at the same time, it ignores the received

current samples from the other end protection relay which is in the test mode.

• The PRO_ACTIVE output is false only in the protection relay that is currently in

the test mode.

Figure 375: Operation during the normal operation of the line differential protection

Operation setting is set to "test/blocked". This blocks the line differential

1MRS759142 F

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