ABB RELION 620 Series Technical Manual page 363

1MAC504801-IB E
620 series ANSI
Technical Manual
to obtain information from the engine manufacturer and to measure the reverse power
during commissioning.
Reverse overpower can also act as an alternative for an under excitation protection in case
of small generators. If the field excitation is reduced, the generator may start importing the
reactive power, making the generator run as an asynchronous generator. A synchronous
generator is not designed to work asynchronously and may become damaged due to
heating in the damper windings or heating in the rotor due to slip frequency current.
When operated in reverse power direction, 32O can be used as an alarm if the power
flowing from the industry is feeding the grid, which may not be desired as per the rules and
regulations of the utility owning the grid.
Q
Non
operating
area
(a )
GUID-69E16240-232F-4B20-B2C0-7CD73E5376C1 V2 EN
Figure 164: Forward active overpower characteristics (a) and forward reactive
overpower characteristics (b)
Operating
area
P
Section 4
Protection functions
Q
Operating area
Non operating area
(b)
P
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