Siemens SIPROTEC 7SJ61 - Temperature Detection Via RTD Boxes; Description

Functions
2.14 Temperature Detection via RTD Boxes
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
200
2.14 Temperature Detection via RTD Boxes
Up to two temperature detection units (RTD-boxes) with 12 measuring sensors in total can be applied for tem-
perature detection and are recognized by the protection device.
Applications
• In particular the RTDs enable the thermal status of motors, generators and transformers to be monitored.
Rotating machines are additionally monitored for a violation of the bearing temperature thresholds. The tem-
peratures are measured in different locations of the protected object by employing temperature sensors
(RTD = Resistance Temperature Detector) and are transmitted to the device via one or two 7XV566 RTD-
boxes.
2.14.1 Description
RTD-box 7XV56
The RTD-box 7XV566 is an external device mounted on a standard DIN rail. It features 6 temperature detectors
and one RS485 interface for communication with the protection device. The RTD-box detects the coolant tem-
perature of each measuring point from the resistance value of the temperature detectors (Pt 100, Ni 100 or Ni
120) connected via two- or three-wires and converts it to a numerical value. The numerical values are made
available at a serial port.
Communication with the Protection Device
The protection device can employ with up to 2 RTD-boxes via its service port (port C).
Therefore, up to 12 temperature measuring points are available in this way. For greater distances to the pro-
tection device the communication via fiber optic cables is recommended. Alternative communication structures
are shown in Appendix A.3.
Processing Temperatures
The transmitted raw temperature data is converted to a temperature in degrees Celsius or Fahrenheit. The con-
version depends on the temperature sensor used.
For each temperature detector two threshold decisions can be performed which are available for further pro-
cessing. The user can make the corresponding allocations in the configuration matrix.
Each temperature input issues an alarm in case of a short-circuit or an interruption of the sensor circuit or if a
sensor is configured but not assigned. Additionally, a group annunciation is generated via all 6 temperature
inputs of an RTD-box (14101 „Fail: RTD“). In case of a communication fault, an alarm of the entire RTD-
box is issued (264 „Fail: RTD-Box 1“ or 267 „Fail: RTD-Box 2“).
The following figure shows the logic diagram for temperature processing.
The manual supplied with the RTD-box contains a connection diagram and dimensioned drawing.