ABB RELION REX640 Technical Manual page 905

Protection and control

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1MRS759142 F

• Area B defines the linear growth recovery voltage level from

Voltage level 2 in a time period from Recovery time 1 to Recovery time 2 .

• Area C is the zone where voltage stabilizes.

The system restores to a normal state and function resets when the voltage is equal

or greater than

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.

Figure 507: 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.

LVRTPTUV Input signals

Table 854: LVRTPTUV Input signals

Technical Manual

Voltage level 2 . The system should remain above this voltage in a time

Recovery time 2 to Recovery time 3 .

Voltage level 4 after Recovery time 4 time period.

Protection functions

Voltage level 1 to

Voltage level 3 is defined to same

Three-phase voltages

Block signal for acti-

vating the blocking