Temperature Detection Via Rtd Boxes; Description - Siemens siprotec SJ62 User Manual

2 Functions
2.20

Temperature Detection via RTD Boxes

Applications

2.20.1 Description

RTD-box 7XV56
Communication
with the Protection
Device
Processing Tem-
peratures
301
Up to two temperature detection units (RTD-boxes) with 12 measuring sensors in total
can be applied for temperature detection and are recognized by the protection device.
• In particular the RTDs enable the thermal status of motors, generators and trans-
formers to be monitored. Rotating machines are additionally monitored for a viola-
tion of the bearing temperature thresholds. The temperatures are measured in dif-
ferent 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.
The RTD-box 7XV566 is an external device mounted on a standard DIN rail. It features
6 temperature inputs and one RS485 interface for communication with the protection
device. The RTD-box detects the coolant temperature 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.
The protection device can employ up to two RTD-boxes via its service port (port C),
7SJ64 also via the additional port (port D).
Up to 12 temperature measuring points are available in this way. For greater distances
to the protection device the communication via fibre optic cables is recommended. Al-
ternative communication structures are shown in Appendix A.3.
The transmitted raw temperature data is converted to a temperature in degrees
Celsius or Fahrenheit. The conversion depends on the temperature sensor used.
For each temperature detector two threshold decisions can be performed which are
available for further processing. 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 dimen-
sioned drawing.
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015