ABB PRO-33.0-TL Series, Service Manual

Page: 21 / 122

Program features 21
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Combinatory limit
Combinatory limit monitors grid voltage and frequency simultaneously. There are limits for
the positive sequence and the negative sequence of grid voltage, and limits for
underfrequency and overfrequency.
The grid is declared as unstable, if the
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negative sequence voltage and the frequency are outside their limits, or
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positive sequence voltage and the frequency are outside their limits.
If either of the conditions is true for the time defined in parameter 188.81 Combinatory trip
time , the grid is declared as unstable and the inverter disconnects from the grid.
Settings
188.80 Combinatory trip
188.81 Combinatory trip time
188.84 Comb pos seq voltage limit
188.85 Comb neg seq voltage limit
188.86 Comb underfrequency limit
188.87 Comb overfrequency limit

Rate of change of frequency
The grid frequency rate of change (RoCoF) has enable and limit parameters. If it is
enabled and the limit is exceeded, the inverter disconnects from the grid.

Active anti-islanding
The anti-islanding function is used to prevent an island situation in an electrical grid. Island
in a grid is a situation in which a generator powers part of the grid even though the power
from the utility grid is cut off. Islanding can be dangerous to people working with the grid
and not realizing that the circuit is still powered. For that reason, distributed power
generators such as solar inverters must detect an island situation and immediately stop
feeding power to the grid.
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The anti-island function is based on a so called active method whereby reactive
current is injected into the grid. The actual detection of a islanding condition is based
on grid voltage measurements. The function can be configured with parameters. The
parameters are preset to such values that ensure that the relevant country-dependent
requirements are fulfilled.
Settings
188.120 1-phase AI

External grid monitoring relay
Depending on the installation country, an external third party-certified grid monitoring relay
may be needed. If an external relay is used, loose limits for grid monitoring should be set.
The recommended setting for overvoltage monitoring limit is 130%. The limit for
undervoltage monitoring should be set below the external relay setting.
The inverter can be controlled by external grid monitoring equipment through parameter
188.16 External trip . If value one (1) is written to this parameter the external monitoring
device indicates to the inverter that the grid is unstable. As a result the inverter trips.