MULTIOBJECTIVE OPTIMAL STRUCTURAL VIBRATION CONTROL USING fuzzy logic control system
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to be chosen on the basis of an experimental trial-and-error study of the control objective.The initial design of an FLC can be optimized using an optimization procedure(e.g.,GAs). TWO-BRANCH TOURNAMENT GA
The GA is a computational representation of natural selec-tion,making the analogy that in survival of the?ttest an in-dividual more?t in its environment is akin to a more optimal design(Goldberg1989;Holland1992).This analogy includes representing designs as individuals in a population,performing a selection(survival of?ttest),and crossover(mating)of a generation of these designs(from a mating pool)to create children,who in turn become the population in the next gen-eration.An individual design is represented by a chromosome, generally a binary string of1s and0s that represent the design parameter values(value of the design variables)for each in-dividual.
The GA has also been adopted for multiobjective optimi-zation(Fonseca and Fleming1995;Crossley et al.1999).Most of these algorithms are based on a?tness function formulated as either a weighted sum of all objectives or some form of ranking,which assigns a better?tness value to designs based on their dominance.Among its many features,the GA uses a population of points to conduct its search.Because the GA is evaluating an entire population in each generation,this pro-vides an opportunity to generate a set of nondominated designs in one run.The two-branch tournament algorithm is based on this feature of the https://www.sodocs.net/doc/0b17792587.html,e of a selection operator for mul-tiobjective optimization is the major difference of the two-branch tournament approach(Crossley et al.1999)when com-pared to other GA-based multiobjective optimization methods. It generates a representation of Pareto-optimal designs,rather than a single Pareto-optimal design,making an ef?cient use of the GA’s population-based search.
Chromosome Representation
Each design is represented by an n-bit-long chromosome. Here,n is the sum of the length required to represent each design variable,which can be determined by
(r?1)p r
r
2<(U?L)?10?2(1) where U and L=upper and lower bound of the design vari-able,respectively;p r=required decimal precision;and r= required length in bits used to represent the design variable.
Initial Population
The GA starts from a population of chromosomes as a set of initial designs.The initial population is chosen randomly. Population size(i.e.,the total number of chromosomes in the population)has been chosen such that the number of design points are suf?ciently large that it encompasses the global op-timum solution.A larger population results in convergence in fewer generations.
Fitness Function
The GA uses a?tness function value for the selection op-erator;therefore,this function re?ects both the objective and a penalty for constraint violation.The?tness function has been constructed in the manner of a sequential unconstrained min-imization technique(i.e.,an objective with external penalty functions to handle the constraints).Because the GA does not require derivatives,or even continuity of the function,several options are available to describe the?tness function(Fonseca and Fleming,1995).For the present study,the?tness func-
tions,which have to be minimized,have been obtained by combining the objective functions?i and the constraint func-tion g i for n cons number of constraints,given by
n cons
f=??c max[0,g](2)
11i i
?
i=1
n cons
f=??c max[0,g](3)
22i i
?
i=1
where?i,c i,and g i=i th objective function,i th penalty coef-?cient,and i th constraint violation,respectively.In this study, to simplify the selection of the coef?cients,c i,all the con-straints have been formulated in a scaled form and the same value of c i has been used for all the constraints.In the scaled form,constraint functions have been posed as given in(4)to enforce a value greater than the allowed value,or as in(5)to enforce a value less than the allowed value.These functions are negative valued when the constraints are satis?ed and pos-itive valued when violated
actual value
g=1??0(4)
i allowed
actual value
g=?1?0(5)
i allowed
Selection Criteria
The two-branch tournament selection approach is such that designs are competitive on one of the two objectives.The pro-cedure for this selection is shown in Fig.1and enumerated in the following steps:
1.Place the entire population of the current generation in
the pot.
2.Select two individuals randomly from the pot without
replacement.
https://www.sodocs.net/doc/0b17792587.html,pute the?rst?tness,and copy the better performing
individual to the parent pool.
4.Repeat steps2and3until the pot is empty.
5.Re?ll the pot with the population from the current gen-
eration.
6.Select two individuals randomly from the pot without
replacement.
https://www.sodocs.net/doc/0b17792587.html,pute the second?tness,and copy the better perform-
ing individual to the parent pool.
8.Repeat steps6and7until the pot is empty.
At the end of the above steps,the parent pool is full.A new population is generated from this population of the parent pool using crossover and mutation operations.
Crossover
The crossover operator is used to produce two offspring from the selected parents.To select the parents for crossover from the new population,a random number between0and1 is generated.If this random number is less than the probability of crossover,then the chromosome is selected for crossover (Michaelwicz1996).The selected chromosomes are randomly paired for crossover.A single crossover site is selected ran-domly.
Mutation
To maintain variability of the population,a mutation oper-ation is also performed on certain individuals.The mutation is performed on a bit-by-bit basis,with a certain probability of mutation.This operation is also performed with the help of
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FIG. 1.
Flowchart of Two-Branch Tournament GA
a random number between 0and 1.If the random number is
less than the probability of mutation,then the bit under con-sideration will be switched (i.e.,0to 1or 1to 0).Selection of Nondominated Designs
This algorithm generates the two best designs,one for each objective,in each generation.Thus,a large number of feasible designs are obtained at the end of the algorithm.All of these obtained feasible designs are not Pareto-optimal designs.Each of the designs in the list generated by GA is compared with all other designs for dominance.If design 1is better than de-sign 2for both the objectives,then design 1dominates over design 2or,in other words,one can say design 2has been dominated by design 1.If a design has been dominated by any other design,the design will be discarded or else it will be retained in the list.After a comparison of all of the designs in this way,all the retained designs are nondominated designs and form a Pareto-optimal set of designs.
BENCHMARK PROBLEM
The example taken for this study is the ?rst generation benchmark problem on structural control given in Spencer et al.(1998).Details of this benchmark problem are available in Spencer et al.(1998),but a brief description has been given here for completeness.It is a three-story,single-bay,model building with an active mass driver at the third ?oor.The eval-uation model is a high-?delity,linear,time-invariant 28-state state-space representation of the input-output model of the physical structure.The model has been presented in continu-ous time as follows:
x ˙(t )=Ax (t )?B u (t )?E x ¨(t )(6)g y (t )=C x (t )?D u (t )?F x ¨(t )?v (t )
(7)m y y y g z (t )=C x (t )?D u (t )?F x ¨(t )
(8)
z z z g In these equations,x is the state vector;x ¨g is the scaler ground
acceleration;u is the scaler control input;y m =[x m ,x ¨a 1,x ¨a 2,
x ¨a 3,x ¨am ,x ¨g ]T
is the vector of measured responses;z =[x 1,x 2,x 3,x m ,x ˙1,x ˙2,x ˙3,x ˙p ,x ¨a 1,x ¨a 2,x ¨a 3,x ¨am ]T is the vector of control-lable responses;v is the vector of measurement noises (sen-sors);and A ,B ,E ,C y ,D y ,F y ,C z ,D z ,and F z are matrices given for the benchmark problem that represent the structural properties and position vectors.Eq.(6)represents the state-space equations of motion,and (7)and (8)are the output and controlled response equations,respectively.EV ALUATION CRITERIA
The evaluation criteria for this example problem has been given in detail in Spencer et al.(1998),and a brief description has been presented here for completeness.Stochastic Evaluation Criteria
The excitation (ground acceleration)x ¨g is a stationary ran-dom process with a power spectral density
2224
S (4?????)
0g g g S (?)=(9)
¨¨x x 222222
g g (???)?4???
g g g where the natural frequency ?g and the damping ratio ?g are
variables lying in the intervals 20rad/s ??g ?120rad/s and 0.3??g ?0.75.The spectral intensity S 0[(10)]has been chosen such that it keeps a constant RMS value of the ground acceleration x ¨g =0.12g ,irrespective of changes in ?g and ?g
0.03?g
2S =
g (10)
02
??(4??1)
g g When this random ground disturbance has been applied to the structure,the performance of the controller has been mea-sured by the following nondimensional criteria:
???d d d 123
J =max
,,(11)1??
????,?g g
x x x 3o 3o 3o
???¨¨¨x x x a 1a 2a 3
J =max
,,(12)2?
?
????,?¨¨g g
x ¨x
x a 3o a 3o a 3o ?x m J =max
(13)3????,?g g
x 3o ?˙x m J =max
(14)4????,?˙x g g
3o ?¨x am J =max
(15)
5??
??,?¨x g g
a 3o
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FIG. 2.Membership Function Used for Input and Output Variables of
FLC
where ?represents the RMS value of the variable shown as a subscript.The interstory drifts d i are the relative lateral dis-placements between ?oors (d 1=x 1,d 2=x 2?x 1,d 3=x 3?
x 2);x ˙i is the lateral velocity of the i th ?oor relative to the ground;x ¨ai is the absolute acceleration of the i th ?oor;x m and x ˙m are the displacement and velocity of the actuator piston relative to the third ?oor,respectively,and x ¨am is the absolute acceleration of the actuator piston.The normalization con-stants and are the worst-case RMS values of the ?,?,?˙¨x x x 3o 3o a 3o third-?oor displacement and velocity relative to the ground and the absolute acceleration of the third ?oor,respectively,over all the allowed values of the ?g and ?g ,for the uncon-trolled case.
Deterministic Evaluation Criteria
The ground acceleration is one of the two historical earth-quake records:NS component of the 1940El Centro and 1968Hachinohe earthquakes.The performance of the controller un-der the applied seismic excitations has been measured by the following nondimensionalized criteria:
?d (t )??d (t )??d (t )?
123J =max max
,,(16)6????x x x earthquake records
t
3o 3o 3o
?x ¨(t )??x ¨(t )??x ¨(t )?
a 1a 2a 3J =
max
max
,,(17)7????x ¨x ¨x ¨earthquake records
t
a 3o a 3o a 3o ?x (t )?m J =max max
(18)8????x earthquake records
t
3o ?x ˙(t )?m J =max max
(19)9????x ˙earthquake records
t
3o
?x ¨(t )?am J =
max
max
(20)
10????
x ¨earthquake records
t
a 3o
where x 3o and x ˙3o =largest peak uncontrolled values of the
displacement and velocity relative to the ground,respectively;and x ¨a 3o =largest peak uncontrolled absolute acceleration for the corresponding earthquake record.FLC DESIGN
The FLC has been designed using ?ve membership func-tions for each of the input variable (acceleration and velocity)and seven membership functions for the output variable (con-trol input u )for ?ner input-output mapping.The input subsets are NL =negative large,NE =negative,ZE =zero,PO =positive,and PL =positive large.The output subsets are NL =negative large,NE =negative,NS =negative small,ZE =zero,PS =positive small,PO =positive,and PL =positive large.A generalized bell-shaped membership function has been used because it can approximate almost all other types of membership functions based on its parameter [(21)].The shape of the generalized bell shape membership function has been de?ned by the parameters a ,b ,and c (MATLAB 1999).Here,a is the half-width of the membership function at 0.5mem-bership grade;b de?nes the slope of the membership function;and c is the position of the center of the membership function
1
?=
(21)
x 2b
x ?c 1?
??
a
The membership functions for the input and output variables have been shown in Fig.2.Two inputs,namely,the third-?oor absolute acceleration and the third-?oor pseudovelocity,have been used in this study.The choice of a velocity and an ac-celeration component for feedback can be explained in the
context of the state of the system in the fundamental mode of
vibration.These feedback components help in generating the initial inference rule base (e.g.,if velocity is zero and accel-eration is high,the structure is at its extreme position and control action is not needed because it is going to return to its neutral position due to the restoring force).On the other hand,if the acceleration is zero and the velocity is high,then the structure is in its neutral position and control action should be applied so that it remains close to its neutral position in order to reduce the maximum displacement.At the intermediate states (i.e.,between the extreme and neutral position),if ve-locity and acceleration are of the same sign,the structure is returning to its neutral position due to its restoring force,and,if the acceleration and velocity are of opposite sign,then the structure is moving toward its extreme position and accord-ingly the control action should be applied.Thus,both a ve-locity feedback and an acceleration feedback are necessary for an improved decision on control action.Initially,the inference rules have been selected on the basis of the available data for the controlled structural response and control command for the linear quadratic Gaussian controller presented by Spencer et al.(1998).These inference rules have then been re?ned using the information about velocity and acceleration in the case of the fundamental mode of vibration.The inference rules were further ?ne-tuned during the optimization of the controller,observing the contribution from various rules and the position of various membership functions after one run of the optimi-
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FIG. 3.Inference Rules for FLC Used in This Study TABLE 1.
Speci?cations of FLC Used in This Study Parameters Variables/operators Number fuzzy subsets (membership functions)
Input variables Acceleration x ¨a 35Pseudovelocity x ˙a 35Output variable Control signal u 7
Aggregation Maximum Fuzzy inference Mamdani type (MATLAB 1999)
Defuzzi?cation
Center of gravity (COG)
zation.The adopted inference rules in this study are shown in
Fig.3.Speci?cations of the FLC used in this study are given in Table 1.
OPTIMIZATION OF FLC
In the present study,a multiobjective optimal FLC design approach results in a set of Pareto-optimal designs.Details of the optimization are discussed in the following subsections.Formulation of Optimization Problem
The objectives in the optimization problem are to minimize the maximum of the nondimensionalized peak interstory drift J 6[(16)]and the maximum of the nondimensionalized peak acceleration J 7[(17)]due to the given earthquake excitation;J 6and J 7have been used as the two objective functions ?1and ?2,respectively,to formulate the ?tness function f 1and f 2as given by (2)and (3).
The parameters speci?ed prior to the solution of the opti-mization problem are the properties of the structure and the earthquake excitation signals,which remain constant.In ad-dition,the uncontrolled response of the structure has also been computed and provided as a constant parameter for the opti-mization problem.The uncontrolled response parameters pro-vided were the worst-case stationary RMS displacement ?x 3o and the velocity of the third ?oor relative to the ground,?˙x 3o the RMS absolute acceleration of the third ?oor,peak dis-?¨x 3o placement x 3o and peak velocity x ˙3o of the third ?oor relative to the ground,and the peak absolute acceleration x ¨3o of the third ?oor,corresponding to the respective earthquake.
Design variables of the FLC are the parameters of the input and output membership functions (i.e.,a ,b ,and c )for each of the generalized bell-shaped membership function described earlier.Due to symmetry,parameters of only half of the input and output membership functions have been considered as de-sign variables,and the other half have been computed using the symmetry about the membership function ZE (e.g.,if the membership function parameters a ,b ,c for membership func-tion NE are 0.5,2.0,and ?0.5,then these parameters for membership function PO will be 0.5,2.0,and 0.5).Parameter c for all the ZE input and output membership functions has been taken as 0.0.The inference rules have not been consid-ered as design variables,but these rules have been ?ne-tuned after the ?rst run of the optimization on the basis of the con-tributions from various rules and the position of the various membership functions.
Spencer et al.(1998)speci?ed the design constraints for the maximum capacity of the actuator for the active mass driver (e.g.,maximum limit on displacement,acceleration,and con-trol command for the actuator).These constraints can be di-vided into two groups:(1)for the ?rst ?ve evaluation criteria (i.e.,J 1to J 5,which are the maximum limits on the RMS displacement,acceleration,and control command);and (2)for the last ?ve evaluation criteria (i.e.,J 6to J 10,which are the maximum limits on peak displacement,acceleration,and con-trol command for the actuator).These constraints can be for-mulated as given by the following equations:
???(22)x x m m
max
???(23)¨¨x x am am
max
???(24)u u max
max ?u (t )??u (25)max
t
max ?x (t )??x (26)m m max
t
max ?x ¨(t )??x ¨(27)
am am max
t
where and u max =maximum limit of the RMS control
?u max input and the maximum control input,respectively;and ?x m max
=maximum limit of the RMS displacement and the max-x m max imum displacement of the actuator piston relative to the third ?oor,respectively;and =maximum limit of the ?x ¨¨x am am
max max
RMS absolute acceleration and the maximum absolute accel-eration of the actuator,respectively.
These constraints have been formulated in a scaled form as given in (4)and (5),so that the same value of the penalty coef?cient c i could be used for all the constraints.It is clear from the (22)to (27)that the constraints are nonlinear and discontinuous,which cannot be handled easily by a traditional optimization algorithm.Such constraints can be handled using GA,because GA does not require the computation of deriva-tives or the continuity of the objective function and con-straints.
Solution Procedure for Optimization
The FLC has been implemented in the SIMULINK model (SIMULINK 1998)of the benchmark problem (Spencer et al.1998)using Fuzzy Logic Toolbox (MATLAB 1999)(Fig.4).The parameter used for the SIMULINK model have been spec-i?ed for the benchmark problem (Spencer et al.1998)which are an integration time step of 0.0005s,sampling time of 0.001s,ADC and DAC resolution of 12bit with a saturation at ?3V ,and sensor noise of 0.01-V RMS (i.e.,0.3%of the span of the ADC).
Two inputs,namely,the third-?oor absolute acceleration and the third-?oor pseudovelocity have been used for the FLC.The details of the FLC are as discussed in the preceding section.The two-branch tournament GA,discussed in the third section,has been used for the optimization of the controller.Param-eters used for GA have been taken on the basis of guidelines given in Grefenstette (1996)and Williams and Crossley (1998).In this study,the population size has been taken as 100members (designs).An upper limit on the number of gen-
JOURNAL OF STRUCTURAL ENGINEERING /NOVEMBER 2001/
1335
FIG.
4.
SIMULINK Model for Building with FLC
TABLE 2.
Initial Parameters and Constraint Limits
Parameters and constraints
Value
(a)Worst-Case RMS uncontrolled response of third ?oor
(?g =0.3,?g =37.3rad/s)
?x 3o 1.31cm
?˙x 3o 47.9cm/s ?¨x 3o
1.79g
(b)Peak uncontrolled response of third ?oor for 1940
El Centro earthquake
x 3o 3.37cm
x ˙3o 131.0cm/s x ¨3o
5.05g
(c)Peak uncontrolled response of third ?oor for 1968
Hachinohe earthquake
x 3o 1.66cm
x ˙3o 58.3cm/s x ¨3o
2.58g (d )Actuator constraints
?u max 1.0V ?x m max
3.0cm ?¨x m a max 2.0g u max 3.0V x m max 9.0cm x ¨am max
6.0g
FIG. 5.Pareto-Optimal Performance Index J 6versus J 7
erations has been taken as 500.The probability of crossover and the probability of mutation used in this study are 0.6and 0.003,respectively.A single crossover site has been adopted.Numerical values of various initial parameters and constraints have been given in Table 2.NUMERICAL RESULTS
The optimization of the FLC has resulted in a set of non-dominated (Pareto-optimal)solutions.Variation of the perfor-mance index J 6with J 7,which have been used as the two
objectives of the multiobjective optimal design of the FLC,has been shown in Fig.5.The variation of the RMS perfor-mance index (i.e.,J 1versus J 2,corresponding to these Pareto-optimal designs)has been shown in Fig.6.From Figs.5and 6it is clear that the performance of the FLC in terms of the performance indices J 1,J 2,J 6,and J 7has been found to be better than that obtained using other controllers reported in the literature (Battaini et al.1998;Breneman and Smith 1998;Kim and Ghaboussi 1999;Kose et al.1998;Lu and Skelton 1998;May and Beck 1998;Spencer et al.1998;Young and
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FIG. 6.Variation of Performance Index J 1versus J 2for Pareto-Optimal
Solutions
FIG.7.Variation of Control Signal for Worst-Case Stability Test of
FLC
Bienkiewicz 1998)for the benchmark problem.The modal space sliding-mode control proposed by Adhikari et al.(1998)is an exception.The results show that the performance in this controller in terms of the acceleration response (J 7and J 2)can be improved at the cost of much higher interstory drift re-sponse (J 6and J 1)and vice versa.
The objective of this study was to develop a strategy to get a set of Pareto-optimal designs for the FLC.Performance in-dex J 6and J 7have been chosen as the two objectives to achieve using the full capacity of the actuator.Constraints on the actuator capacity [given by (22)–(27)]have automatically put a bound on the other performance indices (J 3,J 4,J 5,J 8,J 9,and J 10).The performance indices J 3,J 4,J 5,J 8,J 9,and J 10relate to the RMS and peak energy requirement and actuator capac-ity.While these indices may be higher than those obtained in the other studies on the benchmark problem,reported in the literature,the current approach results in improved utilization of the available resources (actuator capacity).
The stability of the FLC has been examined for each of the Pareto-optimal designs using the extreme (worst)initial con-ditions (Casciati 1997;Battaini et al.1998)and has been found to be stable.Results for the design for which the system has taken the longest time (20s)to reach the neutral position is shown in Fig.7(shown only up to 10s for clarity).For all other cases the settling time for this stability test was found to be less.CONCLUSIONS
Contributions emerging from this paper are as follows:?An approach for a multiobjective optimal design of a FLC has been demonstrated.The advantage of this approach is that it gives a set of Pareto-optimal designs,for making an appropriate selection.
?Performance of the FLC in terms of the structural re-sponse (acceleration and interstory drift)has been found to be better than that obtained using other controllers re-ported in the literature for the benchmark problem.
?The major advantage of this controller is its simplicity and the use of a limited number of measured structural responses.
?As the controller design is based on fuzzy logic,it incor-porates an inherent robustness and uncertainty handling capability.
?To incorporate nonlinearities in the model of the structure,the controller need not to be modi?ed because the FLC can also handle nonlinearities.
?As the optimization method is based on GA,the objective function and constraints have to be incorporated in a sin-gle ?tness function.This gives ?exibility in assigning weights to the objective and constraints in a suitable way.REFERENCES
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NOTATION
The following symbols are used in this paper:
A,B,E,C y,D y,
F y,C z,D z,F z
=state-space matrices for evaluation model;
a=half-width of generalized bell-shaped mem-
bership function at0.5membership grade;
b=slope of generalized bell-shaped membership
function;
c=position of center of generalized bell-shaped
membership function on region of discourse;
c i=i th penalty coef?cient;
d i=interstory drift of i th?oor;
f i=i th?tness function;
g i=i th constraint;
J i=i th evaluation criteria;
k=discrete time step index;
L=lower bound of design variable;
m1,m2=two randomly selected member(designs)of
GA population;
n=length of chromosome in bits;
n cons=number of constraints;
p r=required decimal precision for design varia-
ble;
r=required length in bits to represent design
variable;
S0=spectral intensity to model ground accelera-
tion;
S¨¨x x
g g
=magnitude of constant two-sided spectral
density for white noise used to model ground
excitation;
T=sampling time;
t=time;
U=upper bound of design variable;
u=scalar control input;
u k=scalar control input at time t=kT;
u max=maximum limit of control input;
v=measured noise vector for evaluation model;
x=state vector for evaluation model;
x˙ai=pseudoabsolute velocity of i th?oor;
x¨ai=absolute acceleration of i th?oor;
x˙am=pseudoabsolute velocity of actuator piston;
x¨am=absolute acceleration of actuator piston;
x¨am
max
=maximum limit of absolute acceleration of
actuator piston;
x˙g=pseudoabsolute velocity of ground;
x¨g=absolute acceleration of ground;
x i=displacement of i th?oor relative to ground;
x˙i=velocity of i th?oor relative to ground;
x m=displacement of actuator piston relative to
third?oor;
x˙m=velocity of actuator piston relative to third
?oor;
x m
max
=maximum limit of displacement of actuator
piston relative to third?oor;
x3o=peak third?oor uncontrolled displacement re-
sponse relative to ground for each respective
historical earthquake;
x˙3o=peak third?oor uncontrolled velocity re-
sponse relative to ground for each respective
historical earthquake;
x¨3o=peak third?oor uncontrolled absolute accel-
eration response for each respective historical
earthquake;
y=vector of directly measured response;
z=vector of controlled response;
?g=damping ratio of stationary random process;
?x=membership grade in fuzzy subset corre-
sponding to value x;
?d
i
=RMS interstory drift of i th?oor;
?u=RMS control signal;
?u
max
=maximum limit of RMS control signal;
?¨x
ai
=RMS absolute acceleration of i th?oor;
?¨x
am
=RMS absolute acceleration of actuator piston;
?¨x
am
max
=maximum limit of RMS absolute acceleration
of actuator piston;
?¨x
g
=RMS ground acceleration;
?u
max
=RMS displacement of actuator piston relative
to third?oor;
?˙x
m
=RMS velocity of actuator piston relative to
third?oor;
?x
m
max
=maximum limit of RMS displacement of ac-
tuator piston relative to third?oor;
?x
3o
=worst-case stationary RMS uncontrolled dis-
placement of third?oor relative to ground;
?˙x
3o
=worst-case stationary RMS uncontrolled ve-
locity of third?oor relative to ground;
?¨x
3o
=worst-case stationary RMS uncontrolled ab-
solute acceleration of third?oor;
?i=i th objective function;and
?g=natural frequency of stationary random pro-
cess.
JOURNAL OF STRUCTURAL ENGINEERING/NOVEMBER2001/1337
浅谈输电线路运行与维护(2020年)
浅谈输电线路运行与维护 (2020年) Safety is the prerequisite for enterprise production, and production is the guarantee of efficiency. Pay attention to safety at all times. ( 安全论文) 单位：_______________________ 部门：_______________________ 日期：_______________________ 本文档文字可以自由修改
浅谈输电线路运行与维护(2020年) 输电线路是供电的脉络，对用户供电起着至关重要的作用，所以对输电线路的要求是安全第一，同时经济性也要跟上来，因为供电公司现在已经是一种企业的运作模式，所以要求对经济性方面也要进行提高，为了使线路安全高效的运行，我认为对输电网络可以进行以下三个方面的加强和改进:增加建设项目投资，提高运行工作水平和提高故障的防范措施。 一、增加设备投资方面: 1、加强输电线路结构的完整，增加线路回路或增设变压器，把原来的旧变压器换成节能变压器。由于线路输送功率增加，有一些旧线路的导线截面较小，以致电压损耗和线路损耗都很大。在不可能升压的情况下，可以更换截面较大的导线，或加装复导线来增大线路的输送容量，同时达到降低线损的目的。
2、在用户处或靠近用户的变电所中装设无功补偿设备。在负荷的有功功率保持不变的条件下，提高负荷的功率因素，减小负荷所需的无功功率Q，也就减少线路和变压器中的有功功率和电能损耗。无功补偿设备如同步调相机、静止补偿器、电力电容器。无功需要量大时可用同步调相机，无功需要量小时可用电力电容器，冲击性负荷用静止补偿器。无功补偿设备的放置地点要根据实际情况而定。 3、提高电力网的电压等级。例如把6kV的电力网升为 10kV，把35kV的电力网升压为110kV等。这种方法对降低电能损耗比较明显，但投资也明显增加。采用该方法时，应当通过技术经济比较。 4、在无功功率充足的地方，加装能升高电力网运行电压水平的设备，如调压变压器。因为电力网运行时，线路和变压器等电气设备的绝缘所允许的最高工作电压，一般允许不超过额定电压的10%。因此，电力网运行时，应尽量提高运行电压水平，以降低功率损耗。但必须注意，在系统中无功功率供应紧张时，
10kV线路的安装、运行及维护范本
操作规程编号：LX-FS-A71512 10kV线路的安装、运行及维护范 本 In The Daily Work Environment, The Operation Standards Are Restricted, And Relevant Personnel Are Required To Abide By The Corresponding Procedures And Codes Of Conduct, So That The Overall Behavior Can Reach The Specified Standards 编写：_________________________ 审批：_________________________ 时间：________年_____月_____日 A4打印/ 新修订/ 完整/ 内容可编辑
10kV线路的安装、运行及维护范本 使用说明：本操作规程资料适用于日常工作环境中对既定操作标准、规范进行约束，并要求相关人员共同遵守对应的办事规程与行动准则，使整体行为或活动达到或超越规定的标准。资料内容可按真实状况进行条款调整，套用时请仔细阅读。 10kV线路是电力系统的重要组成部分，担负着输送和分配电能的重要任务。 1 10kV架空线路的安装 10kV线路由电杆、导线、横担、金具、绝缘子和拉线等组成。 1.1 10kV线路的基本要求 1.1.1 10kV线路路径选择的要求
（1）架空线路的路径尽量选择捷径，地形不复杂，投资较少。 （2）应尽量少占农田，避开洼地、冲刷地带及易被车辆碰撞的地方。 （3）应尽量避开爆炸物、易燃物和可燃液（气）体的生产厂房、仓库、贮罐等。 （4）应尽可能把线路架设在公路、道路的两侧，便于运输、施工和以后的运行维护。 （5）线路路径的选择既要照顾当前的需要，又要考虑到今后的发展，并要满足城市规划和电网规
小学、初中英语词汇表(带读音)
Pep小学、初中英语词汇表（共619个单词） 名词n ,noun[naun] 形容词adj ,adjective['?d?iktiv] 数词num ,numeral['nu:m?r?l, 'nju:-] 代词pron ,pronoun['pr?unaun] 动词v ,verb[v?:b] 副词adv ,adverb['?dv?:b] 冠词art ,article['ɑ:tikl] 介词prep ,preposition[,prep?'zi??n] 连词conj ,conjunction[k?n'd???k??n] 感叹词int ,interjection[,?nt?'d?ek??n] a,[?n,?n]一(在元音字母前代替不定代词a) an, [?n,?n]一(在元音字母前代替不定代词a) about[?'baut]（关于，大约）, after['ɑ:ft?]（之后）, afternoon[,ɑ:ft?'nu:n]（下午）, again[?'ɡen, ?'ɡein]再一次, ago[?'ɡ?u]以前, air[??]空气，空中, v t. & vi. 晾晒, 烘干 all[?:l]全部, along[?'l??]沿着, 向前，往前 am, [?m]是（用于第一人称） and, [?nd, ?nd, ?n]和, 与, 及，然后，接着angry['??ɡri]生气的, 恶劣的, 狂怒的 animal['?nim?l]动物, 兽, 牲畜 answer['ɑ:ns?]回答，答案, ant[?nt]蚂蚁, any['eni]任何的, 一点, 一些 apple, ['?pl]苹果; 苹果树 April['eipr?l]四月, are, [ɑ:]是（用于二三人称的复数） ask[ɑ:sk问要求, 请求,at, August['?:ɡ?st]八月, aunt[ɑ:nt]阿姨,姑母, 姨母; 伯母, 婶母, 舅母auntie aunty['?nti:, 'ɑ:n-](aunt的昵称)伯母;婶母;姑母;姨母;舅母 autumn['?:t?m]秋天，秋季，成熟期, 渐衰期 B Back[b?k]（后面）, bad[b?d]坏的, bag[b?ɡ]包，书包, ball[b?:l]球, 舞会 banana[b?'nɑ:n?]香蕉, bank[b??k]银行，河岸, basketball['bɑ:skitb?:l]篮球, bathroom['bɑ:θrum]浴室, be, [bi:, bi][be to-v]表示必要、打算、可能性、假设等或用来表示将来安排 bean[bi:n]菜豆,豆 bear[b??]n熊, vt. & vi.1 承担, 负担 beautiful['bju:t?ful]美丽的,很好的 bed[bed]床, 河床,苗圃, 花坛 bee[bi:]蜜蜂, before[bi'f?:]conj以前, prep. (表示位置)在…前面 begin[bi'ɡin]开始, best[best]最好的, between[bi'twi:n]在….之间, big[biɡ]大的, 成功的,重要的, 重大的;bigger较大的；biggest 最大的 bike[baik]自行车, bird[b?:d]鸟, birthday['b?:θdei]生日, black[bl?k]黑色的, blackboard['bl?kb?:d]黑板, blue[blu:]蓝色的, blow[bl?u]吹, boat[b?ut]小船, book[buk]书, 书籍账簿,vt. 1 登记, 记账 borrow['b?r?u]借，借入， boots[bu:ts]靴子, n擦靴人 bowl[b?ul]碗, 钵, 盘 box[b?ks]盒子，箱子, pencil['pens?l]铅笔, 彩色铅笔 pencil box文具盒, boy.[b?i]男孩, 少年 bread[bred]面包, 生计 breakfast['brekf?st]早餐, bright[brait]明亮的,聪明的, 愉快的，鲜艳的 bring[bri?]带来,造成，引起 brother['br?e?]兄弟, bus[b?s]公共汽车,巴士 but[b?t, b?t]但是, prep. 除…以外 buy[bai]买, 交易, 买卖 by[ba?]乘, 在…近旁; 在身边 bye[ba?]int.再见adj. 次要的 C Cake[keik]蛋糕, can[k?n, k?n]v能，会, n罐, 罐头 car[kɑ:]小汽车, 轿车 card[kɑ:d]卡, 纸牌, 扑克牌，办法, 手段, 妙计careful['k??ful]仔细的, 小心的 carry['k?ri]运，搬,提, 挑, 背 cartoon[kɑ:'tu:n]漫画, 动画片 cat[k?t], 猫 chair[t???]椅子, 大学教授职位 cheap[t?i:p]便宜的, 低俗的, 卑鄙的 cheese[t?i:z]奶酪, chess[t?es]国际象棋, chick[t??k]小鸡, 少妇 chicken['t?ikin]鸡肉, child[t?aild]孩子, 儿童，子女 children['t??ldr?n]孩子们, chocolate['t??k?lit]巧克力, city['siti]城市,都市，全城居民 class[klɑ:s]班级, 阶级, 社会阶级 classroom['klɑ:sru:m]教室, clean[kli:n]干净的，打扫, 正派的, 正大光明的clear[kli?]清晰的, 清白的，畅通的 clearly['kl??l?]明朗地,明确地，明亮地 clever['klev?]聪明的, 灵巧的, 精巧的 climb[klaim]爬, 上升, 增长 clock[kl?k]钟, 挂钟；watch [w?t?] 手表，看，观察close[kl?uz]关, 终结, 结束 clothes[kloz, kloez]衣服, coat[k?ut]外套, coffee['k?fi]咖啡, 咖啡豆 coin[k?in]硬币, cold[k?uld]寒冷, heat[hi:t] 高温, 炎热 have a cold感冒, colour['k?l?]颜色, 脸色, 气色，肤色 come[k?m]来, come back回来, come out出来, come to school来到学校, computer[k?m'pju:t?]电脑, 计算机
浅谈输电线路运行与维护
浅谈输电线路运行与维护 电力是人民生活中必不可少的一项能源，无处不在，对社会的生产、人民生活中起着至关重要的影响，人民的生活、正常的社会秩序已经离不开电力供应，在一切以经济建设为中心、经济迅猛发展的今天，电力系统的稳定供应，也彰显出越来越重要的作用。输电线路能够安全稳定的运行，是需要保障的基本要求，必要通过经常性的检查、维护维修，有效及时的了解输电线路的状况，及时了解天气、外界环境变化对输电线路造成的影响，及时的发现安全漏洞、运行缺陷，这样才能在根本上解决输电线路存在的问题、隐患，保障输电线路的稳定、安全运行。文章是笔者根据中国现有的实际电力供应情况，并结合笔者多年的相关工作经验，针对输电线路中存在的安全隐患问题进行分析，提出与之相应的检测、维护方法和对策，更好的保障输电线路的安全、稳定运行。 标签：输电线路；隐患；运行；安全维护 1 输电线路的运行与维护的重要性 电力与人们的生活息息相关，已经渗透到人民生活的每一个环节，在居民的日常生活中，电视机、电冰箱、洗衣机、空调等的运行都离不开电，学校、超市、商城、车站等等公共场所更是离不开电力的供应，因此可见电力对人民生产生活的重要性。为了能使人民的正常生活秩序、社会秩序得以正常运行，保证人民可以安全的使用电力资源，首先必须要了解电力的重要性，只有输电线路的安全运行，才能提供可靠的电力保障，保证提供电源与用户用电直接的匹配和正常运转、保证各地区用电线路的正常连接、保证城乡居民都可以正常的更好的安全用电，所以必须保证电力运行的安全性、可靠性、经济性，目前用电用户的人数多、范围广、用电功率差别大、供电距离远近不同、输电线路传输量和规模严重不足等等原因，如果没有正常的对输电线路进行维护，就会出现不能及时供电的现象，因此保证输电线路的安全运行，显得尤为重要。 2 加强电网建立与维护的管理工作 2.1 保证设备状态保证输电线路安全运行 使有效的资源达到优化配置，发挥其最大的效力，有效的组织人力、物力、财力等要素，根据实际具体情况开展供电设备的检修，将输电线路划分不同的区段并加以管理，有序展开各项工作，突出重点巡视检修环节，节约费用的同时确保输电线路的安全运行。注意巡视检查的方式方法，可以通过定期巡视和特殊巡视相结合，区分重点地段和非重点地段，组织专业的技术人员针对重点地段存在的问题进行认真分析，并对重点设备、部件进行细致的检测、试验，确保及时有效的解决问题。 2.2 提高职工的素质水平
10kV配电线路的运行和检修
10kV配电线路的运行和检修 摘要：为提高电力线路的运行水平，要求电力线路工作者认真做好线路的运行维护工作，找出配网的薄弱点及问题所在，提出预防和降低配电线路故障率的办法，并结合实际情况不断提升维护技术水平，提高配电网的专业化管理水平和安全运行水平，从而使配网建设、改造、运行管理工作趋向科学化。 关键词：配电线路；故障；巡检；安全运行 10kV配电线路是连接变电站和各类用户的"纽带"，在供电网络中，其作用十分重大。但由于10kV配电线路点多面广，因此也成了故障高发的"群体"。为了提升供电可靠性，做好对10kV配电线路的科学运维与科学检修是很有必要的。 一、10kV配电线路的常见故障及防范 1.10kV配电线路常见故障 由于10kV配电网绝缘水平低，线间距离较小，架空线路通过的地方多为丘陵、山地、空旷地方集邮污染的工业园区，线路易遭受雷击、外力破坏和设备等故障，致使线路跳闸。根据一般运行的经验，10kV架空线路的故障有如下几种：
（1）自然灾害因素造成的事故 雷电、强对流天气、大雾、霜冻等气象灾害每年都有发生，且呈逐年递增趋势，对配电线路设施破坏极大，尤以雷击为甚。雷击导致10kV架空配电线路事故通常有绝缘子击穿或爆裂、断线、配变烧毁、避雷器击穿等。电气设备存在的缺陷是造成雷击事故的重要原因。雷击电流不能快速流入大地。避雷线引下线被盗，雷击电流无法流入大地。 （2）外力破坏造成的故障 因10kV线路面向用户端，线路通道远比输电网复杂，交跨各类线路、道路、建筑物、构筑物、堆积物、树木等较多，极易引发线路故障。因此外力破坏亦是10kV架空配电线路的多发事故之一，这类事故根据破坏源头可分为；①树木生长超过10kV架空线路的安全距离，造成线路接地；②车辆或施工机具碰撞触10kV架空线路及杆（塔），引起线路接地；③风筝碰触引起10kV架空线路相间短路速断跳闸； ④铁塔的塔材、金属被盗引起杆塔倾斜或倒杆（塔）；⑤杆塔基础或拉线基础被雨水冲刷严重引起倒杆（塔）。 （3）设备故障导致线路跳闸事故 由于制造质量以及安装水平等原因，导致户外电气设备存在着缺陷，设备之间的连接接触面不够，接触电阻过大；或这又由于负荷电流大，引起连接处发热烧毁，导致线路缺相运行。
最新小学英语单词自然拼读法
一、循序渐进，逐步掌握自然拼读法 对于小学生而言，自然拼读法的掌握并不是一蹴而就的事情，而是一个循序渐进，逐渐积累熟练的过程，因此，作为小学英语教师，在引导学生掌握自然拼读法时，一定要由简到繁，由易到难。在自然拼读法的教学中，我一直坚持采用“五阶段分解法”，将自然拼读法的学习分成五个阶段，层层递进。第一阶段：引导学生建立字母与字母自然发音之间的直接联系，让学生掌握代表英语44个基本音的字母和字母组合，比如掌握单辅音（p,d,k…）、辅音字母组合（c h,sh,th…），元音包括短元音（a,e,i…）、长元音（ai,ee,ie…）和其他元音（er,or,oi…）的发音等等；第二阶段：引导学生能够成功拼读元音+辅音（辅音+元音）。如：m-ymy，g-ogo等等；第三阶段：引导学生能够成功拼读辅音+元音+辅音。如d-o-gdog，h-o-thot；第四阶段：引导学生成功拼读双音节或多音节单词。如sw-ea-t-ersweater；第五阶段：引导学生听音辨字，即听到单词读音就能拼出该单词。所以说在教学中，教师一定要分清层次，引导学生逐步去学习，一步步的打牢基础。 二、强化练习，熟练运用自然拼读法 学习是一个持续推进，反复强化的过程，最忌三天打鱼、两天晒网。不管哪一门学科，要想掌握相关知识，都必须不断的学习、练习、强化记忆。尤其是关于语言的学习，一定要不断回顾，不断练习。小学自然拼读法的学习，同样如此。在教学中，笔者发现许多教师在教学过程中，只传授给学生最基本的方法，然而却忽视引导学生进行认真的练习，导致学生学过之后，遗忘率很高，影响了教学效果。笔者认为，对于教师而言，一定要将强化练习融入自然拼读法的教学中，比如，在讲解字母和字母组合的基本音时，如果教师讲过之后，没有督促学生进行练习，加深记忆，学生肯定记不清、记不牢、容易混淆，只有不断加强督促，加强检查，引导学生去记忆，去练习，才能将44个字母和字母组合的基本音刻印在学生的脑子里。此外，掌握了基本的字母和字母组合的发音后，教师就应该引导学生进行单词的拼读和拼写练习。在教学过程中，在引导学生掌握字母和字母组合的发音后，我首先会组织学生进行拼读练习，每天都会在黑板上写出很多
输电线路运行维护与状态检修技术 邹铭威
输电线路运行维护与状态检修技术邹铭威 发表时间：2018-06-07T14:58:38.973Z 来源：《电力设备》2018年第2期作者：邹铭威 [导读] 摘要；随着我国的经济快速地发展，人们对于电力供应的要求越来越高，这促使我国的电力系统也在不断地升级更新。 （广东电有限责任公司清远供电局输电管理所 511500） 摘要；随着我国的经济快速地发展，人们对于电力供应的要求越来越高，这促使我国的电力系统也在不断地升级更新。因为存在很多限制因素，目前，在实际的运行中，我国的电网的供电可靠性、稳定性及安全性需进一步地提高。对电网的稳定供电来说，当务之急是进一步对输电线路实行维护与检修。线路的运行维护与检修技术是使线路安全运行的基本手段和措施，能够有效地提高线路运行的社会经济效益。本文简单分析了输电线路的运行维护与检修技术。 关键词：输电线路；运行维护；检修技术； 全网供电过程中，输电系统一直发挥主要作用，而输电线路作为系统重要载体，如果线路架设相对比较偏远，则会增加其施工难度和作业量，同时极易受到其他因素的影响，如自然因素等。在此基础上，需要根据相关检测技术，将输电线路运行维护和检修工作进行贯彻落实，确保新监理维修质量得到全面提升，进而确保全网供电的顺利进行。 1 分析输电线路的检修原理和作用 1.1 检修原理 在对输电线路进行状态检修时，其主要是按照电气设备实际情况进行，即设备性能特征与工作状况等，然后结合情况选择最佳检修技术与方法，属于设备诊断重要方式之一。按照设备类型的相同，可以对其工作状态与运转情况进行对比分析，利用系统工程形式实现设备的全面判断，在此过程中，及时发现设备现存问题。按照相关参数标准，针对极易出现隐患问题进行预测和分析，并向其提供有效预防措施，能更好保证输电线路的运行。根据当前实际情况来看，就输电线路而言，对其进行状态检修时，不仅可以满足成本较低需求，而且还具有较高的检修效果，属于应用较为广泛的一种检修手段。 1.2 检修作用 因为输电线路具有分布范围广、贯穿距离长等特点，如单一线路需满足该市整体供电需求。所以，输电线路在城市用电方面的作用比较显著，然而，当前输电线路仍然处于较为严峻形势，若是仍然采取传统检修方式，则会造成人力资源发生不必要浪费，且检修效率不断下降。在此基础上，对输电线路给予检修至关重要，同时对其检修方式和检修技术进行优化和完善，还能实现检修实效性的目的，需要相关人员给予高度重视。 2 输电线路运行维护 2.1 完善相关规程 当输电线路运行时，应该加大日常管理和监控力度，具体措施包括：第一，结合当前实际状况，制定相应制度规范，明确管控工作，以实现有章可循的目的。第二，对于已经完成铺设工作的输电线路，应对其养护和维护等条例予以明确，并高度重视每项检查环节，确保线路具有较高的安全性。第三，强化线路日常检查，只有通过对线路的认真巡查，才能及时发现安全隐患，以保证线路可以安全运行。 2.2 人为毁损措施 目前，在输电线路运输过程中，偷盗线路、毁损线路问题相对比 较常见，并对输电线路造成较多危害，致使线路无法正常运行。基于此，对线路破坏给予防控至关重要，同时也是确保线路运行的关键措施，其防控措施包括：与当地执法部门取得联系，加大不法人员巡查力度，并对违法行为进行严惩与处理；加强线路保护相关宣传，以宣传教育的方式强化居民保护意识，同时还应对有关知识、法规进行不断普及，确保群众可以自觉参与线路保护工作，构建群众保护团队，对不法分子进行有效监督，使线路损坏情况得到有效缓解。 2.3 雷电损害措施 雷电作为自然灾害，通常具有不确定性、突发性特点，当输电线 路遭雷击后，其危害相对较大。因此，在雷雨条件下，应特别做好线路防范措施，即输电线路进行日常维护时，还应掌握雷电可能会造成的危害，通过对其妥善处理，防止因小失大。另外，雷电损害措施可以采取：增加线路避雷防护的方式进行，如增加相关雷电保护装置，通过消雷设备、避雷针的合理添加，避免线路出现雷电伤害。 3 输电线路运行的检修技术 3.1 雷电检修 输电线路运行中，如果遭遇雷击线路会随之受到损坏，进而影响线路发挥其价值。为了保证线路检修顺利进行，向检修人员安全和健康提供保障，防止事故的出现，应对线路认真做好雷电检测，即雷电检测中，对相关数据进行详细研究，针对符合条件线路，可以将雷电定位系统给予设置，并对线路沿路地区雷电密度、频率进行综合考量，从而制定有效防雷措施。例如：尽可能了解雷电电流和地形等联系，并分析雷击和线路跳闸间规律等。 3.2 绝缘子检修 对绝缘子进行检查时，可以利用过离线实验的方式进行，其检测内容包括：电压查验与线路绝缘电阻测定，就线路绝缘子而言，应对其进行定期线路检查，以便于全面了解线路运行情况。与此同时，还需对线路的劣化率进行科学制定，确保整个检查过程具有科学性特点，而进行绝缘子检修时，其查验方法包括：分布电压与电量测定等，具体选择哪种检修方式，需要结合线路运行情况决定，确保检查方法更具可行性。 3.3 树木检测 一般情况输电线路周边会种植较多树种，在树木不断生长下，会对线路日常送电带来一定影响，属于不可避免因素，严重可能造成供电中断等故障。因此，在满足我国退耕还林原则的基础上，进行原有覆盖面积的扩增，并对输电线路认真做好树木检测工作，通过对线路运行情况的具体掌握，以保证线路可以正常运行。 4 结束语 综上所述，保证电能正常输送，不仅可以更好满足各地区用电需求，而且还能确保电网系统实现稳定运行的目的。根据当前我国电
高中英语Unit3Underthesea练习试题人教版
Unit 3 Under the sea 【导语】捕鲸业是世界上古老的行业之一，它的历史发展和现状如何呢？ The whaling industry is one of the oldest industries in existence.It has undergone vast changes since its beginning，primarily due to the creation of the International Whaling https://www.sodocs.net/doc/0b17792587.html,mercial whaling still continues throughout the world，but the whaling quotas are restricted by the commission，thereby helping conserve the whale populations. Whaling refers to hunting wh ales primarily for their oil，meat and bones.Whaling dates back to prehistoric times，most prevalent in Norway and Japan.The hunt became an industry in the 1600s in the Arctic regions，mostly by the Dutch and British.American colonists started whaling in the 1700s.Nantucket whalers were the first to kill a sperm whale，and the discovery of spermaceti in the whale's head made the sperm whale one of the most highly prized catches.Whaling ships set out from New England into the Pacific for extremely long voyages to hunt down these whales. Whaling industry has been a part of a variety of countries' industries.The following countries were the earliest pioneers in the whaling industry：England，France，Germany，Iceland，Japan，the Netherlands，Norway and the American colonies (although they were not a country at the time)．The following countries still practice whaling in some form or fashion：Canada，Greenland，the Grenadines，Iceland，Indonesia，Japan，the Netherlands，Norway，Russia and the United States. 【词海拾贝】 1．vast adj.广阔的；巨大的 2．primarily adv.首先；最初 3．commission n．委员会 4．commercial adj.商业的 5．quota n．配额 6．prevalent adj.盛行的 7．sperm whale 巨头鲸；抹香鲸 【问题思考】 1．What helps conserve the whale populations? _______________________________________________________ 答案：The whaling quotas.
小学四年级上册英语单词发音归类
小学四年级上册英语单 词发音归类 Company number：【WTUT-WT88Y-W8BBGB-BWYTT-
小学四年级上册英语单词发音归类 a-e /e/ cake make face name shake date race game gate hate plate grape wave Dave Jane Jake Kate a // cap map dad hand bag man fat fan hat cat at apple candy Jack i-e/a/ five rice nine kite nice fine like time bike bite side ice white Mike i // pig big six sit milk fish thin picture is it this miss bit rabbit English window sister fifteen o-e// nose Coke home note rose hope Jones bone old toes no o // dog box body mom orange hot not lot lost Tom John u-e /ju:/ use cute excuse UK USA pupil student tube mule u // duck up cup cut but bus us uncle under fun mum study -e /i:/ he she we be -e- /e/ red bed ten pen pencil leg let get desk seven egg elephant friend
小学英语单词辨音
小学英语单词辨音 5个元音字母的发音规则： Aa 开音节[ ei ] 闭音节[ ? ] 在[w]音后发[ ] Ee 开音节[ i: ] 闭音节[ e ] Ii 开音节[ai ] 闭音节[ i ] Oo 开音节[?u] 闭音节[ ] [u:] Uu 开音节[ju:] 闭音节[Λ]若是在j、l、r、s后读[u:] 练习 给出例词，请找出与划线部分相同的例词，并将其标号填入题前括号内。 Aa （）1、cake A:take B:cat （）2、name A:bag B:plane （）3、China A:about B:want （）4、after A:class B:wash （）5、What A:watch B:father （）6、cat A:flag B:baby （）7、late A:game B:any （）8、have A:happy B:past （）9、animal A:apple B:past （）10、make A:plane B:away Ee （）1、me A:these B:bed
（）2、he A:Chinese B:egg （）3、she A:best B:we （）4、let A:evening B:red （）5、lesson A:desk B:open （）6、mess A:me B:letter （）7、hen A:letter B:Chinese （）8、vegetable A:hen B:apple （）9、eng A:pen B:me （）10、pen A:he B:egg Ii （）1、ring A:shine B:miss （）2、mistake A:big B:find （）3、milk A:pick B:child （）4、nine A:line B:dish （）5、drive A:live B:bright （）6、pig A:finished B:pilot （）7、bike A:time B:city （）8、swim A:kite B:sit （）9、drink A:fish B:time （）10、find A:high B:chicken Oo （）1、nose A:dog B:boat （）2、those A:go B:not （）3、lose A:stop B:old
输电线路运行与维护
1.导、地线的连接要求 同一档距内，一根导线上只允许有1个直线连接管和3个补修管；当张力放线时不应超过2个补修管。 接续管或补修管与耐张线夹间的距离不应小于15m；接续管或补修管与悬垂线夹的距离不应小于5m；接续管或补修管与间隔棒的距离不宜小于0.5m。 重要跨越档内不得有接头 2.导线对地距离的确定 500kV以下的线路，由线路的绝缘强度确定。 500kV以上的线路，线路对地面物体的静电感应影响来确定。 3. 500kV输电线路的限距要求 两边导线5m以外的房屋,在导线最大风偏时,对房屋的净空距离应≥8·5m； 我国500kV线路单回线路走廊的一般宽度55～60m。 4.导线与地线间的距离要求 在环境温度+15℃，无风情况下，档距为L的档距中央导线与地线的距离按下式计算：D≥0.012L+1 (m) 5. 按照我国规程规定:送电线路导线水平相间距离10m时，允许档距为525m，相间距离为11m时，允许的档距为650m。 6.对架空线路运行导线及地线的要求 保证安全的弧垂、对地及交叉跨越距离、线间距离，合理的导、地线配合要求等。总体上，选择具有良好电气性能、机械性能和经济性能的导、地线，采用合理的施工工艺，保证安全可靠的运行参数。 7. 运行中导线的工作温度不得超过其允许值 在环境温度为25℃时，钢芯铝绞线、铝合金绞线最高温度不超过70℃； 大跨越及事故情况下：最高温度不超过90℃； 铜绞线最高温度不超过80℃；钢绞线最高温度不超过125℃； 耐热铝合金绞线的最高允许温度为150～200℃。 8.年运行费用 为维持线路正常运行而每年所支出的费用，包括电能损失费、折旧费修理费和维护费等。 9.导线截面的选择 依据：①年运行费用低，符合总的经济效益。②具有足够的机械强度 ③运行中导线的工作温度不得超过其允许值 原则：按经济电流密度选择，以机械强度、发热、电晕及电压降等技术条件来加以校核。 对35kV及以上电压等级的线路，一般按经济电流密度选择导线截面。 10.导、地线的选型要求 导线材料应具有良好的导电率，足够的机械强度和耐振性能，一定的耐化学腐蚀能力，能保证线路造价经济。 11.电力系统对架空输电线路的基本要求 1、保证供电安全可靠 2、良好的电能质量 3、经济供电。 12.普通架空地线－不与杆塔绝缘，只起引雷入地的作用； 绝缘架空地线－与杆塔绝缘，起引雷入地的作用，还可作载波通讯的通道。 13. 限距――导线间、导线对地、对周围物体及交叉跨越物的最小允许距离。 14.决定导线线间距离的因素有哪些？ 有悬垂绝缘子串长度，运行线路标称电压和导线的最大弧垂，还有导线覆冰和覆冰脱落时的跳跃大小。
10kV线路的安装与维护要点
1 线路的运行及维护 线路的巡视与检查，是为了经常掌握线路的运行状况，以便及时发现和消除设备缺陷，预防事故，并确定检修内容，确保线路的安全运行。 1.1.1 巡视检查的周期巡视检查的周期，要根据线路的电压等级、季节特点及周围环境来确定。对于10kV线路、市区线路每月一次；郊区线路每季度不少于一次，如遇自然灾害或发生故障等特殊情况时，需临时增加巡视检查的次数。 1.1.2 巡视检查的种类电力线路的巡视检查有定期性巡视、特殊性巡视、故障性巡视、夜间巡视、监察性巡视、预防性检查和登杆检查等。 （1）定期性巡视，是线路运行人员日常工作的主要内容之一。通过定期性巡视可及时掌握电力线路各部件的运行状况和沿线情况。 （2）特殊性巡视，是在导线结冰、大雪、大雾、冰雹、洪水泛滥和解冻、沿线起火、地震及狂风暴雨之后，对电力线路全线或某几段某些部件进行详细查看，以发现线路设备遭受的变形或损坏。 （3）故障性巡视是为了查明线路的接地、跳闸等原因，找出故障地点及情况。重合闸装置无论是否重合良好，均应在事故跳闸或发现有接地故障后立即进行巡视检查。 故障性巡视时应遵守下列规定： 1）巡视时应详细进行检查，不得中断或遗漏杆塔。
2）夜间巡视时应特别注意导线落地，对线路交叉跨越处，应用手电查看清楚后再通过。 3）巡视中如果发现断线，不论停电与否，均应视为有电。在未取得联系与采取安全措施之前，不得接触导线或登上杆塔。 4）巡视检查人员全部巡视检查完负责线段后，无论是否发现故障，都应及时汇报，听取指示。 5）在故障巡视检查中，发现一切可能造成故障的物件或可疑物品均应收集带回，作为事故分析的依据。 （4）夜间巡视是为了检查线路导线连接处、绝缘子、柱上开关套管和跌落式熔断器等的异常情况。 （5）监察性巡视，由主管领导或技术负责人进行。目的在于了解线路及设备状况，并检查、指导运行人员的工作。 （6）预防性检查，是用专用的工具或仪器对绝缘子、导线连接器、导线接头和线夹连接部分进行专门的检查和试验。 （7）登杆检查，是为了检查杆塔上部各部件连接、腐朽、断裂及绝缘子裂纹、闪络等情况。带电进行检查时应注意与带电设备的安全距离。 1.1.3 巡视检查的内容 （1）沿线情况 1）沿线有无易燃、易爆物品和腐蚀性液气体。
高考英语一轮复习Unit3Underthesea词汇训练新人教版选修7
Unit 3 Underthesea 基础知识默写篇 一、分层单词 写作词汇 1. vt.放弃;遗弃;抛弃 2. vt.当场见到;目击 n.目击者;证人;证据 3. vi.& n.暂停;中止 4. vt.拖;拉;扯 5. vi.逃避;逃跑 vt.逃离 6. n.住所;住宿 7. n.关系;血缘关系;交往 8. adj.好的;整齐的;匀称的 9. adj.生动的;鲜明的;鲜艳的 10. adj.纯的;纯粹的;纯洁的 11. prep.在……对面 adj.相对的;相反的 12. vt.催促;极力主张;驱策 13. vi.思考 vt.映射;反射;思考 14. adj.意识到的;知道的 阅读词汇 1.jog vi.&vt. 2.dive vi.& n. 3.suck vt.& vi. 4.conservation n. 5.target n. 6.boundary n.
7.pension n. 8.annual adj. & n. 9.narrow adj. 10.shallow adj. 11.steep adj. 12.awesome adj. 13.seaside n.&adj. 14.telescope n. 15.teamwork n. 16.dimension n. 拓展词汇 1. n.深(度);深处→adj.深的adv. 深深地 2. adj.好吃的;可口的→ n.味道;品位;鉴赏力v.尝;品尝;有……的味道 3. adj.意识到的;知道的→ n.意识;认识 4. vi.思考vt.反射;思考→ n.反射;思考 5. adj.锐利的;锋利的;敏捷的→v.(使)变得锋利 6. vt.催促;极力主张;驱策→ n.紧急;迫切;催促→adj.紧急的;迫切的;催促的 7. vt.恐吓 vi.受惊吓→adj.害怕的 二、高频短语 1. 帮助(某人)摆脱困境或危难 2. 对……知道、明白;意识到…… 3. 举起;阻碍 4. 整理;收拾 5. 在此期间;与此同时 6. 靠近 7. upside down 8. (be) scared to death 9. aim at
小学英语单词记忆法
小学英语单词记忆法 作者：u899292/用户名：u899292 一、拼音式记忆法 如：数字“十”ten，可以联想成ten的拼音发音。男人们“men”汉语拼音便是men…… 二、谐音记忆法 1.单词读音谐音法 如：apple单词的汉语谐音是“阿婆”画图“一个阿婆手里拿着一个苹果”联想，看到图画联想到apple的读音，汉意。 2.字母音与汉字音相结合谐音记忆法 如颜色单词红色red，记住一句话，阿姨地里的苹果红了……这一句话，不仅让学生加深了三个字母r，e，d的粗读，还记住了这个单词的顺序，同时又记住了这个单词的汉意“红色”，这样一句话，可谓一石三鸟，在实际的教学中收到了良好的效果…… 三、形近串连记忆法 如tea茶叶，eat吃，teacher教师，meat肉，这些单词形近，老师吃茶吃肉，这样一句话，让学生一下子便记住了四个单词。Purple people紫色的人们，monday moon 星期一，月儿升…… 四、字母谐音及外形和故事结合记忆法 单词eleven “十一”很多同学记忆吃力，即便是当时记住了，可是很短时间又忘了,一种方法想忘记都难，三个阿姨（e）走娘家，（她的娘家门牌号是11.）第一个阿姨带去了一把勾子（l这个字母形状像勾），第二个阿姨呢，竟带去了一把剪刀（v像剪刀），第三个阿姨特别有意思，把自己的大门扛了去……想必是娘家的大门坏了…… 五、循环记忆法 这种方法是一个传统的记忆方法，也是来是们使用的做多的方法，人的大脑有一个特点，对某个信息反复刺激才能记住，例如，三年级的学生每天规定记忆的词汇量是五个单词，第二天记忆十个其中包括第一天的五个，第三天背十五个其中包括前两天的，照这样累计，这种方法也许对于孩子来说是枯燥无味的，但每个单词却都对大脑刺激无数次，从而记得比较牢。
输电线路运行与维护
输电线路运行与维护 发表时间：2018-01-28T19:49:55.200Z 来源：《电力设备》2017年第28期作者：蔡建隆 [导读] 摘要：随着我国经济的不断发展和社会进步，而如今出现越来越多的大面积停电事故，究其原因，则是输电线路的运行出现了故障问题。 （国网甘肃省电力公司陇南供电公司） 摘要：随着我国经济的不断发展和社会进步，而如今出现越来越多的大面积停电事故，究其原因，则是输电线路的运行出现了故障问题。所以加强对输电线路的运行与维护，就是输电线路的安全运行的最有力的保证。本文对输电线路的运行与维护进行探讨。 关键词：输电线路；运行维护 我国地域辽阔，输电线路遍布大江南北，并且架设区域在野外。而我们陇南输电线路状况：一、设备：（一）野外工作环境极差，山大沟深，夏天草深林密，各种剧毒蛇虫多；冬天野猪、熊横行，对运维检修极为不便。尤其是线路巡视，基本靠人工步行；检修时用的工具材材靠人背肩扛。（二）老输电线路设备多，改造缓慢，停电检修机会少，部分线路带病运行。（三）从北到南四季分明，自然灾害多：（1）A：成县、武都、文县片雷去灾害机率大，B：武都、文县片塌方、山体滑坡多（2）A：当地城市建设、老百姓建房、各种施工危害隐患多，B：种植经济林逐年增多，C：农业种植反季节塑料大棚增多，D：畜牧养殖场增多。所以不可避免的受自然环境与人类活动影响。 一、输电线路运行与维护工作 针对输电线路可能存在的隐患与面临的环境风险，应根据输电线路的动态检测数据，结合实际运行情况，有效利用光源、合理利用望远镜、直升机及无人机等巡视工具，设法从不同角度观察线路每个部件的各个面，查找其中的异常情况。与人工巡线、无人机巡线、直升机巡线相配合，进行线路运行和维护。 1、组织管理 良好的组织管理是做好线路运行与维护工作的基础，输电线路的运行与维护需要从组织机构、专业分工上做好组织管理，建立严格的责任流程和制度，定期进行状态检修和运行分析。 2、状态检修 状态监测包括在线监测和非在线监测两类，非在线监测主要是周期性的巡检和离线监测，在线监测则基于光电传感计算和先进的计算机算法，来完成输电线路的电气监测、机械力学监测、环境监测。状态巡视是指运行和维护人员定期进行巡视和巡检，积极发现设备可能存在的安全隐患。 3、运行分析 在定期进行状态检修和监测的基础上，还需要进行运行分析，集成各类输电线路的运行信息，对其进行状态诊断，根据构建的线路健康诊断模型，应用智能诊断算法进行输电线路运行状态分析，根据运行分析的结果制定方案，并下达相应的任务。基于状态检修与状态监测实施的运维工作，具有良好的可靠性与预见性，有利于及时发现事故隐患，降低盲目停电检修带来的损失，节省人力和物力成本，提升运维效率，从而提升输电线路的经济运行水平。 二、输电线路运行维护问题分析 电网的重要构造是输电线路，是输送、配电的重要载体。如果电路发生故障，那整个输电系统将瘫痪。所以电路维护是电力运用的重点考察工作之一。其构造如图所示： 3.1 电力输电线路在设计方面的缺陷 虽然电网建设发展速度较快，供电可靠性也在不断完善，但是电网输送能力的需求提高，电网建设的空间却越来越狭小。比如地区地形复杂，电网线路的协调要求有一定的困难，所以说合理的构建方案对电网运输技术指标和施工质量起着至关重要的作用【2】。电网设计既要保证线路长度的合理性又要降低投资成本，还要保障线路设计安全可靠。 3.2 电力输电线路质量没有达到标准 目前，电力输电线路质量还受科技等因素影响，并不是十分先进，采用的制作材料还有一定的落后性。 3.3 电力输电线路的监察巡视工作有一定难度 电力输电线路的监察巡视是一项长期并且艰巨的任务，因为电路多设置在野外，设置点分布不均匀，勘察有一定难度，还有是输电线路受外力干扰，根据目前的技术水平还不能根治，故障在未来时间将长期存在，所以电路检查工作要做好长期工作的准备。