Figure 361: Typical example of operation of LVRTPTUV function
Activation of the
BLOCK
input resets the timers and deactivates the function
outputs.
4.5.9.5
Application
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
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.
1MRS757644 H
Protection functions
620 series
Technical Manual
691
