ABB RELION REX640 Technical Manual page 904

Protection and control

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Protection functions

Figure 506: Typical example of operation of LVRTPTUV function

Activation of the BLOCK input resets the timers and deactivates the function

Distributed generation, mainly wind and solar farms, are rapidly increasing due

to liberalized markets (deregulation) and the global trend to use more renewable

sources of energy. These farms are directly connected to grids, and due to their

large size may influence the behavior of the grid. These farms are now required

to comply with stringent grid connection requirement, which was previously

mandatory only for high capacity power plants. These requirements include helping

grid in maintaining system stability, reactive power support, transient recovery and

voltage-frequency regulation. These requirements make it necessary for the wind

and solar farms to remain in operation in the event of network disturbances.

Many grid codes now demand that the distributed generation connected to HV

grids must withstand voltage dips to a certain percentage of nominal voltage (down

to 0% in some cases) and for a specific duration. Such requirements are known as

Low-Voltage Ride-Through (LVRT) or Fault-Ride-Through (FRT) and are described by

a voltage versus time characteristics.

Typical LVRT behavior of a distributed generation can be divided into three areas

according to the variation in voltage over time.

• At the time of system faults, the magnitude of the voltage may dip to

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.

1MRS759142 F

Technical Manual