Signals - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.5.8.7
822
• At the time of system faults, the magnitude of the voltage may dip to Voltage level
1 for time defined by Recovery time 1. The generating unit has to remain
connected to the network during such condition. This boundary defines area A.
• Area B defines the linear growth recovery voltage level from Voltage level 1 to
Voltage level 2 in a time period from Recovery time 1 to Recovery time 2.
• Area C is the zone where voltage stabilizes. Voltage level 3 is defined to same
value as Voltage level 2. The system should remain above this voltage in a time
period from Recovery time 2 to Recovery time 3.
The system restores to a normal state and function resets when the voltage is equal or
greater than Voltage level 4 after Recovery time 4 time period.
When the voltage at the point of common coupling is above the LVRT curve, the
generation unit must remain connected, and must be disconnected only if the voltage
takes values below the curve.
GUID-770C4AC5-E28E-4DCE-9B4E-EF50108874C9 V1 EN
Figure 448: A typical required ride-through voltage capability of generating unit
The LVRT requirement depends on the power system characteristics and the
protection employed, varying significantly from each other. The requirement also
differs from country to country. LVRTPTUV function incorporates four types of
LVRT curves which satisfy most of the power system needs. Grid operators can fine-
tune the LVRT curve by setting the parameters as per their requirement, making the
use simpler in comparison with different conventional undervoltage protection with
different operate time setting and logics.

Signals

Table 778: LVRTPTUV Input signals
Name Type
U3P SIGNAL
BLOCK BOOLEAN
Default Description
- Three-phase voltages
0=False Block signal for activating the blocking mode
1MRS759142 C
REX640
Technical Manual