14-11-2012, 02:13 PM
Design of a complete multi-microcontroller based protection system for large diesel turbine generator
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Abstract
This paper presents a multi-microcontroller based protection system, which includes three relaying modules and one master
control module, to realize parallel processing and background management. The proposed protection system is suitable to be
employed as the primary and backup protection for a large diesel turbine generator. Hardware and software redundancy
techniques are used, and the bottleneck effects of the single processor system are eliminated. The hardware of the protection
systemi s modularizedw ith the samea rchitecturew ith respectt o relaying modules.T he master control module is responsiblefo r
system monitoring, communications and man-machine interfacing, it can reassign the protection functions in case of one relaying
module failure. 0 1997 Elsevier Science S.A.
Introduction
Since the 197Os, digital protective relays have attracted
attention by many researchers. Microprocessors
incorporated in the protective relaying improve
availability and reliability by continuous self-monitoring
of the overall relaying system. Besides improving
the performance, microprocessor based relays also offer
greater flexibility and the possibility of adding new
functions, while at the same time, reducing the standard
set of hardware. Many advantages are possible and
utilization of microprocessor based relays is now an
adopted practice.
Two surveys of the developments of computers for
plant protection were conducted by the Generator Protection
Working Group of Power System Relaying
Committee, IEEE [l]. Many possible digital solutions
were proposed to deal with the problems involved in
the conventional protection schemes. Protection of generator
by a digital relay has also been discussed in
papers published in the technical literature [2-41. These
papers usually either focus on one protection function
or algorithm, or utility-oriented prototypes.
Basic hardware design features
The relay hardware is a multi-microcontroller system
consisting of three relaying modules and one master
control module which provide high reliability and low
cost. The overall architecture of the protection system is
shown in Fig. 1.
The heart of the relay is constructed by four 16 Bit
microcontrollers, three of them executing all the relaying
functions. Each of the relaying modules has its own
analog/digital (A/D) interfacing subsystem and no common
memory is shared by these modules.
Measures for improving system reliability
Usually the diesel turbine generators operate in
more abominable environments compared to steam
turbine generators or hydro-generators. Hence the reliability
of protective relay has to be given more attention.
Generally speaking, the reliability of the digital relays
can be improved substantially by their self-diagnostic
capabilities. Severe noise conditions, those
involving electrostatic discharge, or, as found in automotive
environments, can do permanent damage to
the hardware, and the outage and aging of the components
also may cause the maloperation of the protection
system.
Conclusions
A low cost and highly modularized digital protection
system for diesel turbine generator is designed
and implemented. The hardware and software redundancy
techniques and reliability methods are successfully
introduced in the proposed protection system,
which can minimize the impact of any outage
of the system hardware. It also provides user friendly
operator interface, remote communication and
overall system self-monitoring. These features have
been demonstrated by the physical simulation in
the laboratory. Now this protection system is installed
on a ship based diesel turbine generator for
pre-commissioning test. This protection scheme can
also be used for utility generator protection by
adding more relaying modules and protection functions.