ABB RER620

Section 4 1MAC309294-MB F
Protection functions
218 RER620
Technical Manual
Figure 100: Functional module diagram
Freq>/< detection
The frequency detection module includes an overfrequency or underfrequency detection
based on the Operation mode setting.
In the “Freq>” mode, the measured frequency is compared to the set Pickup value Freq>.
If the measured value exceeds the set value of the Start value Freq> setting, the module
reports the exceeding of the value to the operate logic module.
In the “Freq<” mode, the measured frequency is compared to the set Pickup value Freq<.
If the measured value is lower than the set value of the Start value Freq< setting, the
module reports the value to the operate logic module.
df/dt detection
The frequency gradient detection module includes a detection for a positive or negative
rate-of-change (gradient) of frequency based on the set Start value df/dt value. The
negative rate-of-change protection is selected when the set value is negative. The positive
rate-of-change protection is selected when the set value is positive. When the frequency
gradient protection is selected and the gradient exceeds the set Pickup value df/dt value,
the module reports the exceeding of the value to the operate logic module.
Operate logic
This module is used for combining different protection criteria based on the frequency and
the frequency gradient measurement to achieve a more sophisticated behavior of the
function. The criteria are selected with the Operation mode setting.
The relay does not accept the set value “0.00” for the Pickup value df/dt
setting.
f
Over/under
frequency
detection
TRIP
PICKUP
df/dt
df/dt
detection
BLOCK
Blocking
logic
Trip logic
TRIP_OFRQ
TRIP_UFRQ
PICKUP_OFRQ
PICKUP_UFRQ
TRIP_FRG
PICKUP_FRG