DTU-2000 series (Distribution Terminal Unit) is a distributive data acquisition and control system based on
microprocessor. In common SCADA (Supervisory Control and Data Acquisition) system, DTU performs the tasks of
collecting and processing of station data for both analog and digital signals; then DTU-2000 receives the command
from host in master station and transmit back the acquired data, also to perform the function“check before
execution” for station facilities to ensure a safe and reliable execution in system control.
The design of DTU-2000 series is fully modularized with different I/O cards which combines with the communication
ability. The idea for design of DTU-2000 is to be an aesthetic product with quanlity of long-term stability, easy
maintenance, convenient wiring and flexibility in expansion. In the requirements of today’s power utility such as
engineering, operations, and maintenance departments; DTU-2000 series offers flexible and economical solution.
The combination of different types of I/O cards made DTU-2000 to fulfill the different applications from small
distribution to large substation or any generation stations. DTU-2000 series comes in an open architecture through
internal fully protected high-speed I/O LAN (Local Area Network) easy for new additional new processing modules.
When DTU-2000 expands from small system to large or complex system, the existing cards and modules do not
become obsolete. The DTU-2000 series can serve as communication server or the IED as below :
IED
To use DTU as the IED equipment, there are two independent communication channels are provided by DTU CPU
Card. One links to the host computer and the other one links to the power meter or IEDs for obtaining I/O information
for such equipment and also transferring the output control command. Furthermore, the DTU also provides with I/O
cards (AI, DI, AO, DOH and more) to collect the field information and to carry out the output of control command.
DTU-2000 series is generally installed at on-site power stations to apply the monitor and control of signal
performance. DTU-2000 series is designed in multiple processor technique. Each I/O Card has its own processor
that is responsible for the basic data acquisition function. The basic functions are as follows.
A. Data Acquisition Processing
DTU acquires digital and analog signal from station plus processing and storage in the memory and ready to transmit the data back to communication server or control center.
B. Sequence of Event Report
DTU provides the SOE function (Sequence of Event) to monitor the status and sequence, or any changes of equipments at the station. An event is defined as a single change of state. Each time an event is detected, RTU will time tag the event and save a description of the event and the time tag in a first in first out (FIFO) butter. There is 1024 events butter in DTU.
C. Control Output
Two types of control command can be transmitted from the Master Station to devices in the power system via the DTU. One is Trip / Close command, the other is Direct Set point command.
There are two types of control output using Trip/Close command. One is ON / OFF operation output to control CBs, ABSs and the other is Regulation operation output (raise / lower) to control the position of transformer taps. Two types ofTrip / Close commands are supported.
D. Communication Function
The communication function of DTU can be divided into internal communication and external communication.
• SCADA Master: CDC Type II, DNP3.0, IEC870-5, CDT (China).
• DTU Sub-Master: ModBus RTU, DNP3.0, IEC870-5.
• IED : ModBus RTU, DNP3.0.
E. Self-diagnostic Function
DTU is designed with self-diagnostic function. Every abnormal status of DTU is recorded as System Event, or indicated by LED excitation on the panel. The System Event record can be retrieved by test set and store in its
hard disk, which is very easy to detect errors in maintenance.
F. Programmable Algorithm Function
DTU has the capability of user definable “Sequential Algorithm”. The “Sequential Algorithm” within DTU can communicate through a common variable database which consists of analog inputs, digital inputs, accumula
tor inputs, pseudo points, alarm (system) status, digital output, and system clock.
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