Siemens SIPROTEC 4 7UT6 Series Manual page 35

transformer, to monitor the windings of a shunt reactor. For THERM.OVERLOAD2, you may select under
address 144 from the same options as for the first overload protection.
RTD-boxes for Overload
If, in case of an overload with thermal replica, the coolant temperature must be taken into consideration, or if
an overload protection with hot-spot calculation in accordance with IEC 60354 is used (address 142 THERM.
OVERLOAD = th repl w. sens or IEC354), at least one RTD-box 7XV5662–xAD must be connected at the
service interface or an additional interface of the device, which informs the device with regard to the coolant
temperature. The additional interface is set in address 190 RTD-BOX INPUT. The possible interfaces are
dependent on the version of 7UT6x (cf. Ordering Information and Accessories in the Appendix). Port C
(service interface) is available in all versions. Depending on the device version, Port D is also possible.
RTD-box Type
If you operate RTD boxes with the device, the number and transmission type of the temperature detectors
(RTD = Resistance Temperature Detector) can be specified in address 191 RTD CONNECTION: 6 RTD
simplex or 6 RTD HDX (with one RTD-box) or 12 RTD HDX (with two RTD-boxes). The settings have to
comply with those of the RTD-box.
NOTE
i i
The assignment with regard to which temperature measuring point shall be used for which overload
protection will be effected later during setting of the protection functions.
Overexcitation Protection
The overexcitation protection is used to detect increased overflux or overinduction conditions in generators
and transformers, especially in power station unit transformers, which cause impermissible temperature rise
in the iron. Note that the overexcitation protection (address 143 OVEREXC. PROT.) can only be used if the
device is equipped with voltage measurement inputs and voltages are connected. This protection is not appli-
cable for single-phase busbar protection (address 105 PROT. OBJECT = 1ph Busbar). For further details
see Section 2.11 Overexcitation
Reverse Power Protection
The reverse power protection (only for devices with measuring voltage inputs, address 150 REVERSE POWER)
primarily protects a turbine generator unit on failure of notenergy to the prime mover. In the system it can be
used, for example, as a de-coupling criterion. It can only be used for three-phase protected objects, thus for
address 105 PROT. OBJECT = 1 phase transf. or 1ph Busbar. The reverse current protection requires
that the device is connected to a voltage transformer set and, together with a connected current transformer,
allows for a reasonable calculation of the active power. The definition of the reverse direction is explained in
detail elsewhere.
Forward Power Monitoring
The forward power supervision (only in devices with measuring voltage inputs, address 151 FORWARD
POWER) can monitor a protected object both for undershooting and for overshooting a pre-defined active
power. It can only be used for three-phase protected objects, thus not for address 105 PROT. OBJECT = 1
phase transf. or 1ph Busbar. The forward power supervision requires that the device is connected to a
voltage transformer set and, together with a connected current transformer, allows for a reasonable calcula-
tion of the active power. The definition of the forward direction is explained in detail elsewhere.
Undervoltage Protection
Undervoltage protection (address 152 UNDERVOLTAGE) detects voltage dips in electrical machines and avoids
inadmissible operating states and possible loss of stability in electrical devices. It can only be used in three-
phase protected objects, thus not at address 105 PROT. OBJECT = 1 phase transf. oder 1ph Busbar.
It is normally only possible in device variant that have a voltage measuring input.
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
Protection.
Functions
2.1 General
35