Siemens SIPROTEC 4 7UT6 Series Manual page 208

Functions
2.9 Thermal Overload Protection
The current overload alarm setpoint I ALARM (address 4205) is referred to the rated current of the side and
should be set equal to or slightly below the permissible continuous current k ·Ι
of the thermal alarm stage. In this case, the thermal alarm stage is set to 100 % and is thus virtually ineffec-
tive.
Emergency Start for Motors
The run-on time value to be entered at address 4208 T EMERGENCY must ensure that, after an emergency
start and dropout of the binary input
replica has fallen below the dropout threshold. This parameter can only be set with DIGSI under Additional
Settings.
The startup itself is only recognised if the startup current 4209 set in address I MOTOR START is exceeded.
Under each load and voltage condition during motor start, the value must be overshot by the actual startup
current. With short-time permissible overload the value must not be reached. This parameter can only be set
with DIGSI under Additional Settings. For other protected objects retain setting ∞. The emergency start is
thus disabled.
Temperature Detector for Hot-spot Calculation
For the hot-spot calculation according to IEC 60354 the device must be informed on the type of resistance
temperature detectors (RTD) that will be used for measuring the oil temperature, the one relevant for the hot-
spot calculation and ageing determination. With a RTD-box 7XV5662x–xAD up to 6 detectors are possible,
with 2 boxes up to 12. On connection of one RTD-box set under address OIL-DET. RTD the number of the
relevant temperature detector (1 to 6), on connection of two RTD-boxes under address 4221 OIL-DET. RTD
(1 to 12). Only such address is always available that corresponds with the setting in accordance with the func-
tional scope (Section
The characteristic values of the temperature detectors are set separately, see section RTD-boxes
Boxes for Overload
Hot-Spot Stages
There are two annunciation stages for hot-spot temperature. To set a specific hot-spot temperature value
(expressed in °C), which is meant to generate the warning signal (stage 1), use address 4222 HOT SPOT ST.
1. Use address 4224 HOT SPOT ST. 2 to indicate the corresponding alarm temperature (stage 2). It can also
be used for the tripping of circuit breakers if the outgoing message
cated to a trip relay.
If address 276 TEMP. UNIT is set to degree Fahrenheit during configuration of the Power System Data 1,
thresholds for warning and alarm temperatures have to be expressed in Fahrenheit at addresses 4223 and
4225.
If the temperature unit is changed in address 276, after having set the thresholds for temperature, these
thresholds changed for the temperature unit, must be reset in the respective addresses.
Ageing Rate
For ageing rate L thresholds can also be set, i.e. for the warning signal (Stage 1) in address 4226 AG. RATE
ST. 1 and for alarm signal (Stage 2) in address 4227 AG. RATE ST. 2. This information is referred to the
relative ageing, i.e. L=1 is reached at 98°C or 208°F at the hot spot. L > 1 refers to an accelerated ageing, L < 1
to delayed ageing.
Cooling Method and Insulation Data
Set in address 4231 METH. COOLING which cooling method is used: ON = Oil Natural for natural cooling, OF
= Oil Forced for oil forced cooling or OD= Oil Directed for oil directed cooling. The definitions under margin
heading "Cooling Methods" in the function description of the hot-spot calculation.
For hot-spot calculation, the device requires winding exponent Y and the hot-spot to top-oil gradient H
can be set under 4232 Y-WIND.EXPONENT and 4233 HOT-SPOT GR. If the corresponding information is not
available, it can be taken from the IEC 60354. An extract from the corresponding table of the standard with
the technical data relevant for this project can be found in the following table.
208
>Emer.Start O/L , the trip command is blocked until the thermal
2.1.3.1 Setting Notes) under address 191 RTD CONNECTION.
Detection).
. It can also be used instead
N Obj
O/L h.spot TRIP (No 044.2605) is allo-
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
2.10 RTD-
, that
gr