Siemens 6MD85, Manual

Page: 899 / 1256

[fo_ueb_for_Irated, 3, en_US]
EXAMPLE:
Temperature class B for continuous operation: permissible overtemperature = 80 K
From this, a temperature for I
rated
of 120 °C (80 K + 40 °C) can be derived when using a measuring element for
the measurement.
Temperature class F as thermal limiting value: permissible overtemperature = 105 K.
From this, a maximum temperature of 155 °C (105 K + 40 °C) derives.
From these values, the magnitude of the K factor can also be derived.
[fo_bsp_kfaktor, 3, en_US]
If selecting a setting value of 1.1 for the
K-factor
, your selection can be considered as conservative.
Parameter: Storage of thermal replica
•
Recommended setting value
(_:113) Storage of thermal replica
=
no
If a continuous auxiliary voltage of the bay units is ensured, the default setting can be retained.
Parameter: Behav. at I> Imax therm.
•
Recommended setting value
(_:114) Behav. at I> Imax therm.
=
current limiting
The
Behav. at I> Imax therm.
parameter is used to select the process by which the function reacts to
short-circuit currents. To prevent premature tripping of the overload protection at low time constants, high
preloading and high short-circuit currents, the thermal replica can be modified.
The default setting has been selected compatible with SIPROTEC 4 devices. If you wish to take further temper-
ature rise into consideration, the
current limiting
procedure is recommended.
Parameter Value Description
current limiting
The input current is limited to the value set in the
Imax thermal
parameter. If
the measured current exceeds the set current value, the limited current value is
supplied to the thermal replica. An advisable current threshold is approx. 2 to
2.5 I
rated, obj
.
freeze therm. rep.
If the input current exceeds the
Imax thermal
parameter, the thermal replica
will be frozen for the time the parameter is exceeded. This parameter value is
provided to enable compatibility with older products!
Parameter: Temperature sensor
•
Default setting
(_:44) Temperature sensor
=
none
Use the
Temperature sensor
parameter to determine which temperature sensor to use to detect the
ambient temperature.
A temperature sensor (RTD = Resistance Temperature Detector) is used to measure the ambient temperature
of the protected object and to feed it to the device via an RTD unit. The function Thermal overload protec-
tion receives the measured temperature value via the function RTD unit Ether. or RTD unit Serial from the
function group Analog units.
Parameter: Default temperature
•
Recommended setting value
(_:118) Default temperature
=
40°C
Protection and Automation Functions
7.27 Thermal Overload Protection, 1-Phase
SIPROTEC 5, High-Voltage Bay Controller, Manual 899
C53000-G5040-C015-9, Edition 11.2017