Auxiliary Plant Research Articles

Seismic performance investigation of PCS water tank designed as tuned mass damper (TMD) for nuclear containment plant considering soil-structure interaction

Tuned mass damper (TMD) has been applied in civil engineering fields to reduce the seismic response. However, few TMDs are used in the nuclear structure due to the huge additional mass of the traditional TMD device on the nuclear structure. In this paper, the PCS water tank of a nuclear structure is reconstructed into a TMD system to reduce the seismic response of the nuclear structure. The proposed novel water tank-TMD device can use its characteristics of large mass to achieve the tuned shock absorption effectively while maintaining the original function of the water tank. Moreover, more and more nuclear power structures are being built on non-bedrock sites, and the effects of soil-structure interaction (SSI) on the seismic response and seismic migration performance of nuclear power structures need to be reasonably considered. The effects of SSI and auxiliary plants on the seismic response of the nuclear containment plants equipped with PCS water tanks are first investigated. Subsequently, the performance of the water tank-TMD system in reducing the seismic responses of nuclear containment plants is analyzed in detail by considering the effect of SSI, design frequency of TMD, and design criteria of TMD. The research results show that the proposed water tank-TMD system can effectively reduce the seismic response of nuclear containment plants. Besides, it is necessary to consider the influence of SSI on the dynamic characteristics of the structure in the design of TMD when the SSI effect is strong. The water tank-TMD system designed according to the TMD criteria proposed by Sadek et al., and Salvi and Rizzi has better reduction performance compared with that designed by other design criteria.

A system for plant-wide multi-channel backup of nuclear power plant auxiliaries

A system for plant-wide multi-channel backup of nuclear power plant auxiliaries

Shaking Table Testing of a Scaled Nuclear Power Plant Structure with Base Isolation

To investigate the seismic performance and isolation effect of a high-temperature gas-cooled reactor, a 1/20 scale model including a reactor, a spent-fuel plant, and a nuclear auxiliary plant was fabricated. In addition, 220 mm lead-rubber bearings were designed and produced for use in the shaking table test, which included both isolated and nonisolated conditions. Two historical earthquake records and three artificial earthquake motions were used to input the ground motion in the tests. The results demonstrated that the seismic performance of the plant was better and that the structure was in an elastic state, under a safe shutdown earthquake event. Isolation bearings were found to effectively reduce the dominate frequency of the structure. The acceleration amplification factor of the superstructure was found to be less than 1. The isolation test results showed that the peak of the floor response spectrum at the pressure vessel support was less than 0.1 g. In the nonisolation test, the peak of the floor response spectrum was greater than 1 g. In the isolation test, the relative displacement of the structure was less than 1.1 mm, which was relatively small. The structure maintained a good isolation performance and exhibited improved safety under extreme ground motion.

Integration of ion transport membrane with conventional powerplant to enhance the plant capacity with improved power production

Ion Transport Membrane (ITM) is an emerging technology for producing O2 by separating air in its membrane. To decrease energy loss in air separation unit and to increase the overall efficiency of a power generation unit ITM is added with the gasification unit in this model. Ceramic materials are generally used to make the ion transport membrane that produces oxygen by conducting oxygen ions at a specified temperature. Potential advantages can be gained by integrating ITM technology with power generation units as 99% pure oxygen is produced from ITM. Using ITM air separator is more beneficial compared to cryogenic air separation as ITM technology helps to improve IGCC overall efficiency and also reduces plant auxiliaries than that of power generation systems integrated with cryogenic. This paper proposed a novel and effective integration of ITM, gas turbine, HRSG system, gas clean up system and gasification unit to produce sustainable energy. Environmental impacts are considered to design this integrated power generation unit. The proposed model achieved a high gross electric efficiency of 47.58% and high net power of 296730 kW which revealed its potentiality compared to available cryogenic ASU-based combine cycle power plants.

A Study on 500 MW Coal Fired Boiler Unit’s Bowl Mill Performance through Coal Sampling and Characterization: CPRI’s Experience

Coal-fired thermal power stations presently account for nearly 52 % of the total power generation in India’s power generation sector. There is a constant need to monitor the performance of the coal-fired power plant auxiliaries/ components and ensure maintenance of these to optimum levels of operating parameters to achieve the trouble-free generation of quality and consistent electric power output. Coal’s mineralogical content and its physical parameters decide the performance of the coal pulverizer in terms of optimum ground coal output and the life of the grinding elements in the coal mills/ pulverizers. The grinding media in the pulverizes are subjected to high erosion rates owing to the presence of abrasive minerals like pyrites, alumino-silicates and hard minerals like α quartz, which are attached to the coal mass as contaminants during mining. A study was undertaken along with the Pulverizers Division of M/s. BHEL for evaluation of Coal Bowl Mill, for guaranteed performance at a 500 MW capacity NTPC thermal power plant. The study was conducted to assess the effective performance of the pulverizers of this 500 MW boiler unit for its maximum capacity of 60.9 t/hr for guaranteed coal condition and assess optimum output in terms of fineness of the crushed coal during continuous loading under the designed operating parameters. The study was also carried out to ensure that the pulverizer grinding efficiency and the effective output of the finely crushed coal were achieved by proper optimization of the mill mechanical auxillaries and their operating parameters.

Lessons learned after three years of SPIDER operation and the first MITICA integrated tests

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities.In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds, called SPIDER and MITICA. SPIDER is dedicated developing and characterizing large efficient negative ion sources at relevant parameters in ITER-like conditions: source and accelerator located in the same vacuum where the beam propagates, immunity to electromagnetic interferences of multiple radio-frequency (RF) antennas, avoidance of RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have addressed to the necessary design modifications to enable full performances. The source is presently under a long shut-down phase to incorporate learnings from the experimental campaign, in particular events/issues occurred during operation, which led to the identification of improvement opportunities/necessities (e.g. RF discharges, local burns, water leaks, other damages, configuration/design upgrades to maximize chances/margin to quest target parameters).Parallelly, developments on MITICA, the full-scale prototype of the ITER Neutral Beam Injector (NBI) featuring a 1 MV accelerator and ion neutralization, are underway including manufacturing of the beam source, accelerator and the beam line components, while power supplies and auxiliary plants, already installed, are under final testing and commissioning.Integration, commissioning and tests of the 1 MV power supplies are essential for this first-of-kind system, unparalleled both in research and industry field. 1.2 MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1 MV output by combining invertor systems, DC generators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, said events have been addressed and solutions for the repair and the improvement of the system were developed.Hence, NBTF is emerging as a necessary facility, due to the large gap with existing injectors, effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.

Neighbourhood effect of weeds on wheat root endospheric mycobiota

Abstract Micro‐organisms associated with plants provide essential functions to their hosts, and therefore affect ecosystem productivity. Agricultural intensification has modified microbial diversity in the soil reservoir and may affect plant–microbial recruitment. Weeds develop spontaneously in crop fields, and could influence micro‐organisms associated with crop plants through a neighbourhood effect. We explore the effect of weed species on crop plant microbiota as potentially auxiliary plants that affect agricultural productivity. We combined field and controlled laboratory studies to analyse the neighbourhood effect of weeds on wheat root endospheric mycobiota (i.e. fungi within roots) and growth. First, we analysed the effect of weed species diversity and identity recorded in the neighbourhood of individual wheat plants on soil and wheat root mycobiota in the field. Second, we used a plant‐matrix design in laboratory conditions to test the effect of weed identity (nine weed treatments) and their ability to transmit root mycobiota to wheat roots, and the resulting impact on wheat growth. In contrast to soil mycobiota, we demonstrated that wheat root endospheric mycobiota was influenced by the diversity and identity of weeds developing in their 1 m2 neighbourhood. Wheat root endospheric microbiota strongly differs in terms of richness and composition depending on the neighbouring weed plant species. Weed species transmitted from 13% to 74% of their root microbiota to wheat roots depending on weed identity in controlled conditions. Synthesis. Weed neighbours modified wheat plant performance, possibly as a result of competitive interactions and changes in microbiota. Our findings suggest that crop root mycobiota was variable and was modulated by their weed neighbourhood. Synergistic effects between mycobiota of crops and weeds could therefore contribute to soil biodiversity and sustainable agriculture.

Condition monitoring and early fault warning of power plant auxiliary equipment using LSTM-SDAE model with an adaptive threshold

With the increasing penetration of renewable energy in the power grid, which makes power plant equipment is always in changing operating conditions. The correlation between the main and auxiliary equipment of the unit is easy to lead a potential fault, therefore, the safety and reliability of the auxiliary equipment of thermal power units have become a more challenging issue in the case of large-scale renewable energy. Adaptive condition monitoring of the auxiliary equipment can reduce maintenance costs and improve reliability in the thermal power units. Most existing studies perform poorly at extracting features from distributed control systems data and make less use of time series data. A novel adaptive condition monitoring framework and early fault warning method based on long short-term memory and stack denoising auto-encoder network has been proposed for auxiliary equipment of power plant unit. The proposed framework has two main parts, which contain condition monitoring and adaptive early fault warning. The Mahalanobis distance of a reconstruction error is defined as the monitoring indicator to reflect the condition of the equipment. The Chebyshev inequality determines an adaptive threshold for early anomaly detection that applies to changeable working conditions. The effectiveness of the proposed method was verified by the actual case of the coal mill. The adaptive threshold method can obtain the advance time of 42s and 108s, respectively.

Thermodynamic Analysis of Binary and Trinary Power Cycles Fueled with Methane–Hydrogen Blends

The development of hydrogen energetics is a possible way to reduce emissions of harmful substances into the atmosphere in the production of electricity. Its implementation requires the introduction of energy facilities capable of operating on environmentally safe fuel. At the same time, from a technological point of view, it is easier to implement a gradual shift to the use of hydrogen in power plants by burning methane–hydrogen blends. This paper presents the results of thermodynamic studies of the influence of the chemical composition of the methane–hydrogen blend on the performance of binary and trinary power units. It is shown that an increase in the hydrogen volume fraction in the fuel blend from 0 to 80% leads to a decrease in the Wobbe index by 16% and an increase in the power plant auxiliaries by almost 3.5 times. The use of a trinary CCGT unit with a single-circuit WHB and working fluid water condensation makes it possible to increase the net efficiency by 0.74% compared to a binary CCGT with a double-circuit WHB and a condensate gas heater.

Оперативное прогнозирование потребления мощности в изолированных энергосистемах

Ensuring stable power supply and proper electric power quality while continuously managing the production, transmission and distribution of electricity is the main goal of the dispatch center of any power system, including an isolated one. Continuous management is based on an electric power regime planning process. According to its results, the dispatch center sends to the electric power industry entity the planned dispatch schedule of the power generation, transmission and consumption in an hourly (half-hour) breakdown, which has to be received by the managed entity 8–10 hours before the onset of the planned day. In the operational management of the electric power regime, the dispatch center operators on duty adjust (update) the values of the planned dispatch schedule. Active power consumption in the power system is one of the most significant parameters being updated. The possibilities of improving the accuracy of operationally forecasting active power in isolated power systems are investigated taking the Kaliningrad power system as an example. The existing power consumption forecasting methods are analyzed. The influence of power plant auxiliaries on the total active power consumption in the power system is studied. Methodological principles for operational forecasting of power consumption have been developed and proposed, which are recommended for inclusion in regulatory documents as a methodology. The proposed methodology is based on a mathematical model that takes into account the consumed power variation rate on a typical day, forecasted meteorological data and the dependence of power consumption for power plant auxiliaries on the composition of the generating equipment switched in operation.

APPLICATION OF RANGE EXTENDER BASED ON SOLID OXIDE FUEL CELLS (SOFCS) FOR ELECTRICAL BUSES: EXPERIENCE OF CERES POWER (UNITED KINGDOM) AND WEICHAI POWER (CHINA) COMPANIES

In previous articles on this topic [1-3] we examined the perspectives of application of power plants based on solid oxide fuel cells (SOFCs) as auxiliary power plants as well as range extenders for heavy freight transport [1,2] and cars [3]: we considered experience of USA [1], Europe [2] and Japan [3]. We showed, that such kind of systems give opportunity to obtain electrical power from chemical energy of hydrocarbon fuel oxidation with record-high efficiency (much higher than competitive solutions) in order to supply on-board vehicle systems during stops of main engine, as well as to significantly extend the range of electrical vehicles by means of constant charge of batteries directly during motional and their discharge due to operation of electrical engine. In current manuscript, we examine the world first experience of SOFC power plant application as range extender for electrical buses. Group of Ceres Power (UK) and Weichai Power (China) companies executed a corresponding project. As a result of project execution system prototype with power output of 30 kW was developed and manufactured, tests on bus lines are planned to be executed in nearest future. The system examined in current manuscript is the most powerful in comparison to other systems studied in this set of manuscripts: 30 kW against 1.5 and 9 kW [1], 3 kW [2] as well as 5 kW [3] for systems examined in previous works. Examined system uses compressed natural gas (CNG) as a fuel; this hydrocarbon is very convenient one due to well-developed distribution network, ecological cleanness in comparison with more complex and heavy hydrocarbon mixtures. Application of low-temperature fuel cells (with proton-exchange membrane), which are more simple in manufacture, in automobile transport leads to the demand in development of hydrogen supply networks, which is not developed nowadays at all.

Моделирование теплообмена в утилизационном прямоточном котле вспомогательной энергетической установки на основе органического цикла Ренкина

Currently, there are many ways to improve the energy efficiency of different technological processes. The article presents the results of heat transfer simulating in a recovery direct-flow boiler of a ship auxiliary power plant using the organic Rankine cycle. There has been illustrated the basic circuit of the organic Rankine cycle unit. The parameters of the studied working bodies (pentane, ethanol, methanol) have been given. The process of the coolant boiling (for methanol) is considered, the process (5 s) of the coolant boiling from the liquid state to the steady state is modeled. There are presented the graphs of the dependence of the heat transfer coefficient on the length of the evaporator tube, on the specific heat of vaporization, on the surface tension, on the physical properties of the heat carrier material. There have been summarized the results of studying the dependence of the heat transfer coefficient during organic coolant boiling on such physical properties of the coolant as heat of vaporization and surface tension. Obtaining a numerical dependence that allows to calculate the heat transfer coefficient during the boiling of organic heat carriers, taking into account the physical properties of these heat carriers has been analyzed. The study was carried out by creating a numerical model of the evaporator in the ANSYS Fluent software. It has been found out that with the increasing ratio of the surface tension force to the specific heat of vaporization, the heat transfer coefficient increases. The empirical equation was also obtained for calculating the heat transfer coefficient during the organic heat carrier boiling.

Оценка последствий отказа асинхронных электродвигателей вследствие обрывов стержней короткозамкнутых обмоток роторов

Despite the great attention paid by Russian and foreign authors to the problem of timely fault detection in the squirrel-cage rotor windings of high-voltage induction motors, the papers published by them pay little attention to issues related to substantiating the need for carrying out the relevant studies. However, this is especially important for high-voltage electric motors used in power plant auxiliaries. The aim of the study is to assess the consequences from failure of induction motors used in power plant auxiliaries caused by a break of the rotor winding bars. Assessment of the failure consequences is an important component of the transition to risk-oriented management of induction motors operation. The main components of the failure consequences and the resulting economic damage are identified. It is shown that failures of high-voltage induction motors caused by broken rotor bars can lead to economic damage of several million rubles. It has been found, based on computer simulation results, that during operation of induction motors with broken rotor bars, their magnetic and electrical losses increase significantly. The study results have shown that the economic damage may also be significant during long-term operation of a large number of induction motors with this type of failure. The accomplished assessment of the failure consequences in money terms confirms the relevance and necessity to perform functional monitoring of the state of the rotor windings of high-voltage induction motors used in the system of power plant auxiliaries.

As a black start the wind power storage system has a storage capacity configuration

Through multiple simulations and statistics of its capacity deficit data, the basic value of the energy storage capacity that can cover most wind conditions is determined. Considering that during the black start process, other aspects other than the plant electricity also occupy the energy storage capacity, and the capacity compensation is made in the calculation. Finally, the verification model shows that its energy storage capacity configuration can support the black start task of the auxiliary plant in the area under most wind conditions and has certain economic efficiency.

Fuzzy Neural Optimized Fuzzy Logic Controller Based Dynamic Voltage Restorer for Power Quality Improvement with Non-linear Loads

Recently a large attention has been focused on a power quality domain due to: disturbances caused by non-linear loads, Increase in number of electronic devices and growth of renewable energy sources. Power quality measures the fitness of electric power transmitted from generation to industrial, domestic and commercial consumers. At least 50% of power quality problems are of voltage quality type. In power system voltage sags, voltage distortion introduced by harmonics, and asymmetrical voltage are considered to be the most severe affecting power quality, because both utilities and consumers are affected by these disturbances. Different methods introduced to solve power problems but the custom power devices are the most effective and efficient methods, one of which is the use of the Dynamic Voltage Restorer (DVR). The main objectives of this research are to achieve more accuracy in compensating the voltage variations and reducing the total harmonics distortion (THD) to acceptable limits. Most of the researchers applied the control strategies to compensate the voltage disturbances in critical load but did not focus on the objective of reducing the total harmonics distortion (THD). In many sensitive loads such as, airport lighting system, medical equipment, auxiliary plant of power system, and adjustable speed drives., the level of the (THD) is more important, this research focuses on mitigating the harmonics to less than 3%. An adaptive controller like fuzzy neural optimized fuzzy logic controller is proposed to improve the performance of the DVR in injecting the required voltage to restore the load voltage to its nominal value under different voltage variations which are created by MATLAB/SIMULINK program for a period of 0.15s from 0.8s and kept till 0.95s.

Assesment of group regulation feasibility in thermal power plant auxiliaries capacity control

The method of group capacity regulation of centrifugal mechanisms is proposed to solve the problem of increasing the energy efficiency of thermal power plant auxiliaries. The method is based on using a group frequency converter for basic capacity regulation of centrifugal mechanisms. Additional regulation is commonly carried out by throttling, bypassing or changing the guide vane opening angle.Analysis of auxiliary power consumption showed that due to ineffective regulation methods, the share of power consumption can reach 50 %.A mathematical model of the centrifugal mechanism that allows for studying various regulation methods is developed. The task of finding optimal control parameters for a group of centrifugal mechanisms that ensure power boiler operation is stated and solved. By the results obtained, it was determined that group capacity regulation of boiler draft mechanisms is most rational. For the feed pump, an individual variable-frequency drive shall be used.In contrast to the individual variable-frequency drive, the introduction of the group regulation method requires less investment. This method can significantly reduce the auxiliary power consumption of thermal power plants. The projected decrease in auxiliary power consumption is 10.7 %.The results show the high efficiency of the group capacity regulation of centrifugal mechanisms, so this method can become a promising direction in increasing the energy efficiency of thermal power plants

An Overview of EGS Development and Management Suggestions

The world is facing the energy challenge to over-reliance to fossil-fuels, the development of renewable energy is inevitable. From a clean and economic view, enhanced geothermal system (EGS) provides an effective mean to utilize geothermal energy to generate. Different form the conventionalhydro geothermal, the host rock of EGS is Hot Dry Rock (HDR), which buries deeper with high temperature (more than 180°C). The generationof EGS is promising. The development of EGS can be combined with the tech Power to geothermal energy. Exceed power is supposed to drive fluid working in HDR layer to obtain geothermal energy for generation. The whole article can be divided into three parts. In the first art, evaluation indexes of EGS as well as pilot EGs Projects (e.g. Fenton Hill and Basel) and exiting EGS project (e.g. Paralana and Newberry) are summarized, which points a general impression on EGS site. The dominate indexes are heat flow, geothermal gradient and thermal storage. The second part is focused on the simulation methods and working fluids selection of EGS. A detailed comparison of the main simulation software (e.g. TOUGH2 and FEHM) is carried out. With the respect of working fluid selection, the comparison between water and CO2 is researched and CO2 is a preferred option for EGS development for less fluid loss and less dissolution to HDR. The art of CO2-EGS is introduced clearly in this part. The third part is about the addition consideration of EGS plant operation, it excludes auxiliary plant support and HSE management.

Исследование самозапуска асинхронных двигателей 0,4 кВ собственных нужд электростанций

The purpose of this work is to study the self-starting of induction motors for the auxiliary needs of power plants and substations as well as the mutual influence of motors on each other under short-term voltage dips and after voltage recovery on the buses to which these motors are connected. The object of the research is the operating VIII section with the capacity of 0.4 kV of the auxiliary service system with 9 induction motors of the heat and power plant no.1 in the city of Dushanbe (Republic of Tajikistan). Simulation modeling was carried out in the software package Electrical Transient Analyzer Program (USA) using algebraic and simplified differential equations to determine the values of indicators of static and dynamic stability of auxiliary needs of power plants and substations. As a result of modeling, the values of indicators of static and dynamic stability of the auxiliary needs system of power stations are determined. Based on the results obtained the margins of static and dynamic stability of auxiliary needs of power plants and substations are constructed and the conditions for implementing the optimal self-start, which allow to ensure uninterrupted operation of responsible mechanisms with induction motors at voltage dips are determined. The developed methods for studying the self-starting of power plant and substation auxiliary need induction motors ensures more accurate determination of the values of static stability voltages and dynamic stability time. The developed simulation model allows to specify and determine the success of induction motor self-starting in the systems of power plant and substation auxiliary needs. The developed methods are recommended for more precise selection of operating values for relay protection and automation as well as technological protection in the systems of auxiliary needs of power plants and substations with induction motors for more reliable operation of the main and auxiliary technological equipment.

TGSim Plus™—Real-Time Dynamic Simulation Suite of Gas Turbine Systems for the MATLAB®/Simulink® Environment

Dynamic simulation of turbomachinery by Hardware in the Loop (HIL) real-time systems has become an essential practice, due to the high cost of real equipment testing and the need to verify the control and diagnostic systems’ reaction to emergency situations. The authors developed a full model of a power generation Gas Turbine Plant, including liquid and gaseous auxiliaries, and the electrical generator and starter motor, integrated in a MATLAB®/Simulink® simulation suite: TGSim Plus™. This allows assembling models of various gas turbine (GT) architectures by customised Simulink® library blocks and simulating steady state and transient conditions, such as complete start-up and shutdown operations as well as emergency, contingent operations and artificially injected fault scenarios. The model solver runs real-time steps at milliseconds scale. The paper describes the main modelling characteristics and typical results of steady state and transient simulations of a heavy-duty gas turbine under development by Doosan Heavy Industries and Construction (Changwon, South Korea). Comparison with benchmark design simulations obtained by a reference non real-time software shows a good match between the two environments, duly taking into account some differences in the GT models setting affecting parts of the sequence. The paper discusses also the bleed streams warm-up influence on GT performance and the start-up states trajectories dependency on control logic and on the starter helper motor torque envelope.

Determining Prototypes and Signs for Automated Diagnostics of Steam Turbine Equipment

Nowadays, turbine building plants try to equip their turbines with automatic control systems that include, in addition to their basic functions, automated fault-diagnosing procedures. The article presents the authors’ experience gained from developing diagnostic systems and evaluating state parameters both for individual components of power equipment and for a power unit and thermal power plant as a whole; in addition, the specific features pertinent to the development of such automated systems are described. Such systems can be used for the purposes of operative and postoperative diagnostics. The first group of applications includes, e.g., vibration diagnostics of turbines, and the second group may include assessing the state of the thermal expansion system components, control system, and turbine plant auxiliary equipment; determining the technical and economic indicators; etc. Development of a prototype is the basis of any diagnostic task. In comparing the equipment’s actual state with the state of the prototype, it is necessary to determine the values of the state parameters from which the diagnostic tasks are solved, i.e., the faults are detected. Diagnostic prototypes' development methods are identified: normative, statistical (expert), physical, and digital. These methods can be combined within a single diagnostic algorithm, due to which it becomes possible to achieve more reliable and efficient (less expensive) assessment of equipment malfunctions during its automatic diagnostics. The advantages and drawbacks of each method are described, and examples of implementing diagnostic tasks with different prototypes are given. Matters concerned with revealing a fault, evaluating the state of equipment components and residual life, and predicting the state parameters are solved. It is shown that one of the complex problems that has to be solved in developing a vibration diagnostic system is to substantiate the relationship between the sign and type of equipment malfunction. Using vibration diagnostics as an example, fault symptoms are grouped into boundary, factor, and correlation ones.