Michael Uspensky
Reliability
Assessment of the Digital Relay Protection System
The quantitative assessment attempt of
reliability indicators for the specific digital structure of
the relay protection system by analogy with an assessment of
similar digital systems in other industries is given in this
work. The reliability models of system components are
provided. The calculation sequence is shown. Calculation
results give an optimistic evaluation of such protection
creation and indicate the influence of the number of
autonomous protection blocks reserved by the central
protection and recovery time on the system availability.
DOI:
https://doi.org/10.24411/1932-2321-2019-13001
L.H. Hasanova
Method of Conversion of
Double Fed Machine
Into Synchronous Operation Mode and its
Simulation
Double fed induction machines, made on
the base of wound rotor machines, thanks to the rapid
progress in the converter equipment (due to widespread use
of fully controlled thyristors and power transistors)
nowadays are widely used as generators (wind power and small
hydropower) as well as the motor-where relatively small
speed adjustment range (30-40%) is required, by restrictions
of the frequency inverter on the installed capacity. There
are cases when the technology of their application as a
generator and motor mode imposes their long-term operation
in sub-synchronous rotational speed, i.e, without speed
control. In this case, it is proposed to use only the
rectifier side of the frequency inverter feeding the rotor
winding of a double fed induction machines, switch into a
synchronous mode of operation. This will greatly increase
the delivery of reactive power into the grid and use the
generator more efficiently. Presented a developed
mathematical model of double fed induction machines, which
allows to study of all operation modes of double fed
induction machines in single set-up–by immediate designation
(sub- and super-synchronous speed control); in synchronous
generator mode with a significant reactive power output into
the grid, as well as in squirrel cage induction generator
mode.
DOI:
https://doi.org/10.24411/1932-2321-2019-13002
Farhadzadeh E.M., Muradaliyev A.Z.,
Rafiyeva T.K., Rustamova A.A.
Maintenance of
Reliability of Methodical Support of the Management of
Objects EPS
One of the basic problems of
development of intellectual control systems of maintenance
service and repair of the equipment and devices of electro
power systems is increase of reliability of methodical
recommendations. The risk of the erroneous decision exists,
first of all, because of presence among statistical data of
operation of gross blunders, abnormal values. If to that
still to add difference not casual samples statistical data
of operation from theoretical representative samples random
variables from a general data set, to consider multivariate
character of statistical data of operation and absence of
methods of the analysis small samples multivariate data,
difficulty of the decision of this problem becomes obvious.
The method which on the basis of fiducially the approach and
theories of check of statistical hypotheses is capable to
reveal abnormal realizations is developed. And application
the express train-methods of calculation of critical
fiducially values an interval for the chosen significance
value, allows to solve this problem without special tables
and the COMPUTER.
DOI:
https://doi.org/10.24411/1932-2321-2019-13003
Neha Sharma, J P Singh Joorel
Study of Stochastic Model of a Two
Unit System
with Inspection and Replacement Under
Multi Failure
The present paper studies a two
non-identical units system model arranged in parallel with
inspection and preparation time for replacement under multi
failures. Initially, first unit (A) is in operative mode and
other unit (B) is kept as warm standby. The first unit is
subjected to two types of failures, i.e. minor failure and
major failure. On failure of the first unit, it will be
sent for inspection to check the type of failure i.e.
whether minor or major failure. If some minor failure is
found, it will be repaired and on major failure, the unit
will be replaced by the new unit. However, the system will
take some preparation time for replacement. Further, the
standby unit may also fail during the standby mode. There is
a single repairman which is always available with the
system. Different measures of reliability have been obtained
to study the effectiveness of the system such as transition
probabilities, mean time to system failure, availability,
busy period of repairman and net profit incurred and various
system parameters are analysed graphically.
DOI:
https://doi.org/10.24411/1932-2321-2019-13004
Ibrahim Yusuf, Surajo Mahmud Umar
Reliability
Modelling and Assessment of Multi Standby Hybrid System
Systems connected to an external
supporting device for their operations viewed as hybrid
systems have been manufactured to meet the demand of
industries, economic growth and populace in general.
Companies and organizations heavily rely on these systems to
conduct their business. The paper deals with the reliability
and availability characteristics of four different systems
requiring external supporting device for their operation.
The system consists of main unit connected to the cold
standby supporting devices. The failure and time of both
main unit and supporting device are assumed to be
exponentially distributed. Markov models are developed and
differential difference equations are derived to obtain
explicit expressions for the steady-state availability and
mean time to failure and perform analytical and numerical
comparisons. Comparisons show that system with five cold
standby supporting devices is the most reliable system.
DOI:
https://doi.org/10.24411/1932-2321-2019-13005
Kamlesh Kumar Shukla, Rama Shanker
Shukla Distribution
and its Application
In this paper a two-parameter lifetime
distribution named, ‘Shukla distribution’ which includes
several one parameter lifetime distributions including
exponential, Shanker, Ishita, Pranav ,Rani and Ram Awadh as
particular cases, has been proposed and investigated. Its
moments have been obtained. The hazard rate function, mean
residual life function and stochastic ordering of the
distribution have been discussed. Maximum likelihood
estimation has been explained for estimating the parameters
of the distribution. Applications of the distribution have
been explained through real life time data and its fit has
been found satisfactory over well-known one parameter and
two-parameter lifetime distributions.
DOI:
https://doi.org/10.24411/1932-2321-2019-13006
Kapil Naithani, Dr. Rajesh Dangwal
Fuzzy Reliability of a System by
Converting Trapezoidal
Intervalued Fuzzy
Number to Pentagonal Triangular Intervalued Fuzzy Number
In classical set theory there exist
only two possibility of any element belonging to the set yes
or no, that is its probability of belonging to the set
either 0 or 1, but this theory is fail to predictable in
many system where the possibility of an element belonging to
set is not exact, that is there exist some vagueness about
the element affecting the system. Therefore L. A. Zadeh
gives a new theory of fuzzyness, where the belongingness of
an element can except 0 or 1 and take any value between [0,
1]. This new approach give us much benefit to modelling the
real situation and find the reliability of any system. This
theory also useful to find the most critical event in any
fault tree model. Fuzzy theory are applicable in many areas
industrial, technical, engineering, medical etc.
DOI:
https://doi.org/10.24411/1932-2321-2019-13007
Gurami Tsitsiashvili
Calculating the
Variance of the Linear Regression Coefficient
In this paper, we choose such a
particular formulation of the problem of calculating linear
regression coefficient, when the moments of observation form
an arithmetic progression. It is proved that the variance of
the trend estimation in this case decreases proportionally
to the third degree of the length of the series of
observations. If the estimation of a linear trend is based
on several independent samples, the integral estimation of
the trend is constructed and its variance is determined by
special optimization procedure. This procedure is based on
simple geometric consideration.
DOI:
https://doi.org/10.24411/1932-2321-2019-13008
Stefan Rass, Stefan Schauer
Refining Stochastic
Models of Critical Infrastructures by Observation
The simulation of cascading effects in
networks of critical infrastructures (CIs) can be approached
in various ways, all of which at some point call for the
specification of (numeric) model parameters. Taking
stochastic models as one popular class of methods, finding
proper settings for the values that determine the stochastic
models can be a challenge. In this work, we describe a
method of graphical specification of a probability value on
a qualitative scale, and how to convert and use the obtained
value as a prior for Bayesian statistics. The connection is
made to the point of having the initial value specified only
as an “initial guess”, which can be refined using Bayesian
statistics. Eventually, under consistency conditions
depending on the application, this amounts to an online
learning approach that takes the parameter to convergence
towards their true values, based on the user’s subjective
initial guess, but never challenging a person to give a
reliable number for a probabilistic parameter.
DOI:
https://doi.org/10.24411/1932-2321-2019-13009
