Siemens 6MD86 - Application and Setting Notes

Resetting the Thermal Map
You can reset the thermal memory via the binary input indication >Reset thermal replica. The thermal
memory will then have a 0 value. A reparameterization will also lead to resetting the thermal memory.
Blocking the Function
Blocking will cause a picked up function to be reset. The function can be blocked externally or internally by the
binary input signal >Block stage.
All indications then drop out and the thermal memory is set to the value 0.
Blocking Closure
The signal Block close can be used to prevent closure of the protected object at a high thermal load. The
signal is set if the tripping overtemperature is exceeded, and cancelled if the temperature falls below the
dropout threshold.
Functional Measured Values
Measured Value Description
(_:310) Equival. current
Besides the thermal measured values in percent, the equivalent
current is also issued as a thermal current-measured value (A or
kA). The current equivalent is the primary current, which corre-
sponds to the thermal measured value in percent, assuming
steady-state conditions.
(_:304) Time until close
The Time until close is the expected time until it is possible
for the protected object for reclosure. The calculation of this
value is based on the assumption of constant currents. The
thermal replica has then fallen below the setting value of the
dropout threshold.
(_:305) Time until trip
The Time until trip is the expected time until tripping
(100 % value exceeded) occurs. The calculation of this value is
based on the assumption of constant currents.
(_:306) Overload
The value Overload indicates the current temperature of the
protected object in percent. Tripping occurs if 100 % is exceeded.
Application and Setting Notes
Parameter: Threshold current warning
•
Recommended setting value (_:101) Threshold current warning = 1.1 A for l
rated
= 1 A
Set the threshold to the maximum permissible continuous current (I
max, perm
). This results in the same setting
value as for K-factor.
Parameter: Threshold thermal warn.
•
Recommended setting value (_:104) Threshold thermal warn. = 90 %
The default setting can be left at a K-factor of 1.1, because the thermal memory sets itself to 83 % at
continuously flowing rated current. The calculation uses the rule of three: 100 % corresponds to (K-factor)
2
and x % corresponds to 1
2
.
[fowarnsc-100810-01.tif, 2, en_US]
At a K-factor of 1.05, the thermal memory for rated current is 91% filled. Increase the Threshold
thermal warn. to 95%.
7.27.4
Protection and Automation Functions
7.27 Thermal Overload Protection, 1-Phase
896 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017