Measurand
To detect critical power-system situations, the Undervoltage-controlled reactive-power protection function
uses the fundamental values of the phase-to-phase voltages, the positive-sequence current, and the reactive
power.
Q-Measurement Direction
The default directions of the positive reactive-power flow Q and the forward direction of the short-circuit
protection are identical, in the direction of the protected object. Via parameter Q sign, the direction of the
positive reactive-power flow Q can be changed by inverting the sign of the reactive power Q.
Pickup
The protection stage picks up under the following conditions:
•
All 3 phase-to-phase voltages are below the parameterized threshold value.
•
The positive-sequence current I
1
is above the parameterized threshold value.
•
The power-generation facility requires more than the parameterized reactive power (Q is above the para-
meterized threshold value).
Trip Interface
The stage provides 2 operate signals, the
Operate (generator)
and the
Operate (grid)
. Depending
on the parameter Trip interface contains, one or none of them will be forwarded to the trip interface
of the circuit-breaker interaction.
Blocking of the Stage
The following blockings reset the picked up stage completely:
•
Externally or internally via the binary input signal
>Block stage
•
Measuring-voltage failure
For further information, refer to chapter 6.7.4.1 Description.
Blocking of the Operate Delay and Operate Signal via the Device-Internal Inrush-Current Detection Function
The Blk. w. inrush curr. detect. parameter permits you to define whether the operate delay should
be blocked by a threshod-value violation due to an inrush current.
For further information about device-internal Inrush-current detection function, refer to chapter
6.3.7.1 Description .
Application and Setting Notes
Parameter: Blk. by meas.-volt. failure
•
Recommended setting value (_:13921:10) Blk. by meas.-volt. failure = yes
You use the Blk. by meas.-volt. failure parameter to control the response of the stage when a
measuring-voltage failure is detected.
A measuring-voltage failure can only be detected if one of the following 2 conditions is met:
•
The device-internal Measuring-voltage failure detection function is configured and switched on.
•
The binary input signal
>Open
of the function block Voltage-transformer circuit breaker is connected to
the voltage-transformer circuit breaker.
Parameter Value
Description
yes
The Protection stage is blocked when a measuring-voltage failure is
detected. Siemens recommends using the default setting, as there is
no assurance that the Protection stage will function correctly if the
measuring voltage fails.
6.40.3.2
Protection and Automation Functions
6.40 Undervoltage-Controlled Reactive-Power Protection
SIPROTEC 5, Overcurrent Protection, Manual 829
C53000-G5040-C017-8, Edition 07.2017
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