CLDC Technical Information:(Remote Terminal Unit) Out Station

Remote terminal unit(RTU) is a system that continuously monitors status data & analog data. This data is transmitted to a master station. It also receives and executes control commands from the master station to open and close output relays and operate controls on any connected IEDs.

The RTU is essentially a computer which can store and process data in digital form. RTU maintain its own local database of all the points, which are to be measured and controlled and continuously updates the information. The RTU sends data to the master in response to queries sent by the master(poll-response method). Typically only information that has changed since the last query is sent to the master.

Analog information's are received from current and voltage transformers. The output of the current and voltage transformers are then sent to transducers. The output of these transducers(0-1ma) are sent to the analog card of RTU. A/D converter converts these analog signal to digital form for use in the microprocessor of RTU. On the other hand status signals are taken from voltage free contacts of CB(52a) to status card to monitored Status of CB . After processing RTU transmit this digital data to master station through Power line carrier (PLC) & microwave communication. The RTU sends data to the master in response to queries sent by the master (poll-response method). Typically only information that has changed since the last query is sent to the master.

Remote Terminal Unit (RTU)Architecture:

1 built in communication port to master(IEC 870-5)
1 built in communication port to local HMI
1 built in communication port to local test and maintenance PC
3 built in communication port as spare.
Power supply Unit (48VDC to +/-12V,24V,5V)
Analog, Status & Control Card
STAC Board
MEMCOW (Memory communication and watchdog)
A/D Converter
Relay

Status, Analog, Control (STAC) Board (60195-c.)

The purpose of the board is to provide an interface between the CPU and the status, analog, and control input/output boards

Memory,Comm. & Watchdog (MEMCOW) Board (60197)

Pentium 166 MHz microprocessor

32 MB SDRAM memory

4 ISA card slots, 4 PCI card slots

2 on board serial ports

BIOS contain QPL's proprietary software.

CPU cooling fan

CPU Motherboard(6O230) The motherboard has the following features:

The purpose of the board is to provide the CPU with 4 more serial ports, a system watchdog, timer outputs, and miscellaneous inputs and outputs. The MEMCOW also has a Serial EEPROM for holding RTU configurations and IED tables. Note, if the MEMCOW Board is replaced in an RTU then the configuration is lost and the RTU has to be reconfigured.

Memory,Comm. & Watchdog (MEMCOW) Board (60197)