Siemens 7SJ82, Manual

Page: 821 / 1638

Measured Value Description
(_:13591:321) V/f th.
Thermal tripping of the overexcitation protection. If
the value reaches 100 %, the tripping occurs.
Cooling Time
If the value drops below the threshold (
(_:13591:3) Threshold
), tripping of the thermal characteristic
curve (dependent characteristic curve) is reverted. However, the parameterized cooling time (
Cooling time
therm.replica
) reduces the thermal storage (counter content) to 0. This parameter is defined as time. It is
required by the thermal replica in order to cool down from 100 % to 0 %.
Resetting the Thermal Map
The binary input indication
(_:13591:501) >Reset thermal replica
can be applied to reset the
thermal replica. The thermal replica will then have a value of 0. A reparameterization will also lead to resetting
the thermal replica.
Blocking the Stage
The function can be blocked externally or internally by the binary input signal
(_:13591:81) >Block
stage
. Blocking will cause a picked up function to be reset.
Application and Setting Notes
Thermal overloads extended over a longer period will jeopardize electric equipment, for example, synchro-
nous motors, generators, or transformers and may cause damage. When using the thermal, user-defined char-
acteristic curve, the overexcitation protection lends itself perfectly for adjustment to the specified limits of the
protection equipment.
The following provides the recommended settings:
i
i
NOTE
It must be noted that one requirement for the correct mode of operation of the function is based on the
proper setting of the power-system data.
You can find more detailed information on this in chapter
6.1 Power-System Data .
For additional setting recommendations, verity the following parameter in the power-system data:
•
Adjusted rated frequency
•
Adjusted rated voltage of the protected object
•
Adjusted rated voltage of the voltage transformer of the applicable measuring point
Parameter:
Threshold Value
•
Default setting
(_:13591:3) Threshold
=
1.10
The
Threshold
parameter is used to describe the value for the permissible continuous overexcitation.
The default value is a practical value used for transformers. The value may be less for generator applica-
tions. These values can be found in the manufacturer's information.
Parameter:
Time Delayed Warning
•
Default setting
(_:13591:101) Warning delay
=
10.00 s
When using the
Warning delay
parameter, the time can be determined by which the warning indica-
tion of the stage should be delayed after the pickup. This time delay depends on the specific application.
This time must clearly exceed the reaction time of the regulators. 10 seconds is a feasible value.
Parameter:
Cooling Time Therm. Replica
•
Default setting
(_:13591:102) Cooling time therm.replica
=
3600 s
6.39.3.2
Protection and Automation Functions
6.39 Overexcitation Protection
SIPROTEC 5, Overcurrent Protection, Manual 821
C53000-G5040-C017-8, Edition 07.2017