Tpu2000 And Tpu2000R Internal Operation - ABB TPU2000 Technical Manual

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide
Register Scaling and Re-Mapping and User Definable Register (UDR) Configuration
Process
In the evolution of SCADA hosts, different capabilities have been implemented in conjunction with a protocol's
implementation. Some SCADA manufacturers have limited the range of numbers accepted at the host level.
Other SCADA manufacturers have reserved alternate definitions of most significant bit placement. Still, other
SCADA manufacturers have restricted the amount of commands, which a host may send over a network.
ABB's implementation of Register Scaling and Re-Mapping is one method of dealing with certain restrictions or
limitations of a SCADA host's protocol implementation. For example, if a host device only accepts numbers from a
value of 0 to 4095 (12 bit unipolar) or –2047 to + 2048, how can that host device interpret the Van (Voltage a to
neutral) in the TPU2000 which reports the value as a number from 0 to +4,294,967,295 (32 bit number)? The
answer is that one of the devices must take the 32 bit data and scale it into a format usable by the other device.
Many hosts share this limitation and are unable to undertake the mathematical machinations to scale the data
value. The ABB TPU2000 and 2000R permits scaling of its own internal data. The procedure is straightforward in
that a simple configuration screen is presented to the operator and menu of choices is selected to complete the
configuration procedure.
Re-mapping is especially instrumental in increasing network throughput by allowing all information to be accessed
via one network transaction. Within the TPU2000 and 2000R, multitudes of values are available for retrieval via a
network connection. However, different protocols require that each group of information can only be accessed via
a single network query. Thus if three different groups of information are required via the network, three network
accesses must occur. However, if the information is re-mapped to a single memory area in the relay, only one
network access need be undertaken to gather the data. Network throughput is increased. Register scaling and
re-mapping is common to all ABB TPU2000 and 2000R relays. The Register Scaling and Re-Mapping procedure
is the same for DNP/Modbus/Modbus Plus/Standard Ten Byte Protocols. Modbus uses this method to group data
so that throughput may be improved by obtaining the data in one network scan.
TPU2000 and TPU2000R protective relays provide for scaling and re-mapping functionality. The TPU does not
support this capability. Figure 5-25 illustrates the example of re-mapping Van to one of 32 possible Modbus
register locations. The example table configuration entries are shown in the Figure. A definition of each
configuration entry and mathematically derived configuration examples follow.
TPU2000 and 2000R Internal Operation
The TPU2000 and TPU2000R reads the raw analog values received from the CT and PT physical connections.
The microprocessor-based relay then converts the analog values to a raw digital numeric value from the relay's
internal Analog to Digital Converter (A/D) hardware platform. The conversion of the voltage and current readings
is not complete. The TPU2000 and TPU2000R microprocessor then takes the raw converted value and performs
a mathematical calculation providing a numeric value which is displayed on the relay's front panel MMI or through
network accesses.
A protection engineer would recognize the terms as such:
PRIMARY VALUES – the metering values displayed on the protective relay's front panel interface.
SECONDARY VALUES – the current or voltage received by the CT or PT attached to the unit.
SCALED VALUES – the value received by the host device (or calculated by the IED and transmitted to the host)
through the communication interface.
The mathematical calculations involved require the CT Phase, CT Neutral, and PT ratios in order to convert the
raw A/D to an understandable value, displayed on the front panel MMI or available for access via a network
connection. Thus, the information Van (Voltage A to Neutral), is displayed on the front panel MMI is in converted
format (not raw A/D readings), and the data received via the Modbus/Modbus Plus Registers (40265 and 40266)
is reported in Volts in a 32 bit representation. The maximum value able to be physically metered by the relay is
74