Application - ABB RELION REX640 Technical Manual

1MRS759142 C
4.5.9.6
REX640
Technical Manual
The function is blocked and LOWAMPL_BLKD is activated, if the measured frequency
deviates ±5% from the nominal value.
The magnitude of calculated vector shift for three phase-to-earth or phase-to-phase
voltages, USHIFT_A_AB, USHIFT_B_BC and USHIFT_C_CA or positive
sequence voltage U1SHIFT, which resulted in the activation of last OPERATE output,
are available in the Monitored data view.
The activation of BLOCK input deactivates the INT_BLKD output.
GUID-E4A9345A-FC5A-4128-9F21-553C8ADD797B V1 EN
Figure 451: Vector shift during Loss of Mains
Pulse timer
Once the Pulse timer is activated, it activates the OPERATE output. The pulse length
of OPERATE is fixed to 100 ms.
The activation of the BLOCK input deactivates the OPERATE binary output and resets
the timer.

Application

Use of distributed generation (DG) units is increasing due to liberalized markets
(deregulation) and the global trend to use more renewable sources of energy. They
generate power in the range of 10 kW...10 MW and most of them are interconnected
to the distribution network. They can supply power into the network as well as to the
local loads. It is not common to connect generators directly to the distribution
networks and thus the distributed generation can cause some challenges for the
protection of distribution networks. From the protection point of view, one of the most
challenging issue is islanding.
Islanding is defined as a condition in which a distributed generation unit continues to
supply power to a certain part of the distribution network when power from the larger
utility main grid is no longer available after the opening of a circuit-breaker. Islanding
is also referred as Loss of Mains (LOM) or Loss of Grid (LOG). When LOM occurs,
Section 4
Protection functions
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