VGB POWERTECH 11 (2019)

VGB PowerTech 11 l 2019
Digital nuclear security level DCS main and auxiliary data distribution based on NASPIC platform
and indication signal belongs to the auxiliary
function data.
The periodic test in digital security DCS belongs
to the non-security function, and the
periodic test data belongs to the auxiliary
function data, which can not affect the execution
of the system security function.
Therefore, the relevant design is implemented
in the TU interfaced with the periodic
test device. In the periodic test, the
module fault signal, the on/off feedback
signal and the successful locking feedback
signal need to be sent to the engineer station
and the main control room for alarm
and instruction after processing.
The alarm and indication signals belong to
auxiliary function data, which are mainly
used to assist operators to monitor the status
of units and assist maintenance engineers
to analyze and locate faults, mainly
including equipment state feedback, PAMS
parameters, process parameters and alarm
signals.
Instrument control alarm and maintenance
information belongs to auxiliary function
data. Transferring such data will occupy a
large amount of communication resources
of the system. At the same time, alarm and
indication signals for operator monitoring
and maintenance engineers to analyze and
locate faults will be sent to NC-DCS and
maintenance engineer station.
Main and auxiliary data distribution
scheme
In digital security level DCS, the main and
auxiliary data are processed in the same
main processor, and the theoretical calculation
shows that the worst response time
of shutdown protection theory will exceed
the user requirements. Through the analysis
of the data of a digital security level DCS
of an engineering test reactor, the ratio of
main and auxiliary data is shown in Ta -
ble 1.
It can be seen from Ta b l e 1 that supplementary
data account for 97.62 % of the
total volume, and the main data only account
for 2.38 %. This will enable the processor
that performs protection logic and
communication to process a large number
of auxiliary data. A large number of auxiliary
function data will cause the main control
module to spend a lot of time to execute
communication transceiver, logical
processing, and so on. With the increase of
processing cycle, the response time of the
system will increase, so the response time
will exceed the requirements. In order to
solve this problem and ensure the processing
speed and time of the main channel of
the shutdown protection and special security
function, a transmission unit (TU) is
added to each protection group and logic
series of the digital security level DCS, It is
specially used for processing display,
alarm, periodic test and maintenance information
transmission functions, and the
Tab. 1. Comparison of main and auxiliary data of security level DCS.
Data function Data type Data volume Ratio
Shutdown / Dedicated M 0.875 Kb 2.38%
Alarm / Display / Periodic test A 35.825 Kb 97.62%
M- main data, A- auxiliary data
IP
TRAIN A
IIP
TRAIN B
Note: - Main function data flox, - Auxiliary function data flow
Fig. 3. Schematic diagram of main and auxiliary data distribution.
IIIP
main work is accomplished. It can separate
data flow from auxiliary function data
flow, which reduces the task and communication
traffic of protection group and logic
series, reduces the complexity of software,
shortens the response time of executing
protection function, and improves the
real-time, security and reliability of the
system.
The structure of main and auxiliary data
shunting in digital security DCS is shown in
the F i g u r e 3 . The protection group IP
and logical series A are studied. The
main data (Instrument Preprocessing Unit
PIPS-1, Protective Channel Processing Unit
RPC-1, Column A Special Safety Facility
Drive System Subgroup ESFAC-A1, Column
A Priority Management Unit ACM-A)
that perform security functions is processed
and transmitted first. Other auxiliary
data are exchanged by transmission
unit (TU) and external data information,
as are other protection groups.
The data distribution mechanism of separate
transmission of different types of signals
can effectively ensure that the data
processing and transmission of security
functions are not affected by non-security
functions. The auxiliary function data is
distributed by TU, which effectively reduces
the load of the main function data transmission
channels, and improves the realtime
and reliability of the system.
At present, the main and auxiliary data distribution
technology based on NASPIC
platform has been successfully applied to
many projects, such as engineering test reactor,
Xiapu fast reactor, ACP100 small reactor,
and has received good engineering
application results.
Comparative study of data
transmission methods with other
platforms
At present, the commonly used security
level DCS platforms in domestic nuclear
power plants mainly include MELTAC-N
platform plus of Mitsubishi Company, TXS
platform of Siemens, TRICON platform of
Invensys and Common Q platform of Westinghouse
Company [2].
By investigating the above security level
DCS platform architecture and data transmission
mode, the main data and the auxiliary
data of alarm display, periodic test
and other functions for the implementation
of shutdown protection and dedicated
safety facilities drive function are all processed
in the same processor. Compared
with the digital nuclear security level DCS
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