Method for evaluating health state of energy storage device of high-voltage circuit breaker based on energy storage current analysis
阅读说明：本技术 一种基于储能电流分析的高压断路器储能装置健康状态评估方法 (Method for evaluating health state of energy storage device of high-voltage circuit breaker based on energy storage current analysis ) 是由 顾朝敏 董驰 夏彦卫 李晓峰 李天辉 贾伯岩 于 2019-10-31 设计创作，主要内容包括：本发明公开了一种基于储能电流分析的高压断路器储能装置健康状态评估方法,将开口式电流传感器卡在储能电机电源线上,采集电机运行的整个过程中的电流,开口式电流传感器所采集的电流值传输到机械特性测试仪,机械特性测试仪对电机电流波形进行记录。本发明采用在线监测的方式,测量装置直接布置在断路器储能装置上,不需要拆卸弹簧即可实现；测量装置在断路器运行过程中进行布置,不影响断路器正常运行；实时监测断路器储能电机的电流,保证检测数据的完整性和连续性,从而对储能装置缺陷的趋势进行分析判断,既做到了设备更换的经济性,又避免了缺陷的扩大。(The invention discloses a method for evaluating the health state of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis. The invention adopts an on-line monitoring mode, the measuring device is directly arranged on the energy storage device of the circuit breaker, and the on-line monitoring can be realized without disassembling a spring; the measuring device is arranged in the running process of the circuit breaker, so that the normal running of the circuit breaker is not influenced; the current of the energy storage motor of the circuit breaker is monitored in real time, and the integrity and the continuity of detection data are guaranteed, so that the trend of the defects of the energy storage device is analyzed and judged, the economical efficiency of equipment replacement is realized, and the defects are prevented from being enlarged.)
1. A method for evaluating the health state of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis is characterized by comprising the following steps of: the open type current sensor is clamped on a power line of a phase line of a stator winding of the energy storage motor, the current in the whole process of the operation of the motor is collected, the current value collected by the open type current sensor is transmitted to the mechanical characteristic tester, and the mechanical characteristic tester records the current waveform of the motor.
2. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 1, wherein: the open type current sensor is arranged on an energy storage motor of the circuit breaker, when the circuit breaker acts, the energy storage motor works, the open type current sensor senses the current of a power line of the energy storage motor, the open type current sensor records and uploads a current waveform to a mechanical characteristic tester, the measured current waveform is compared with a current standard waveform of the energy storage motor, and the health state of the energy storage device is judged;
the standard waveform is a standard characteristic waveform extracted from a current waveform of the type of energy storage motor in a normal state.
3. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 2, wherein: the standard waveform of the current of the energy storage motor is divided into the following four stages:
stage one: t is t 0-t 1Starting process of motor
t 0Electrifying at the moment, electrifying the energy storage motor, starting the motor to start without load after the power supply is switched on, and finishing the starting stage of the motor at the moment t1 to ensure that the motor starts to work stably; this phase is characterized by a relatively high starting current I st；
And a second stage: t is t 1-t 2Stable working process
The motor starts to rotate but does not stretch the spring to do work at the stage in the process of stabilizing the current of the motor, so that the motor is in a no-load rotating state, the motor is in a stable working state, the current of the motor tends to be stable and basically unchanged, and the current of the motor is I a；
And a third stage: t is t 2-t 3Increase of load moment
The energy storage motor does work at the stage to drive the closing spring to store energy, the magnitude of current at the stage is related to the load change, and at t 3At the moment, the motor load moment is maximum, and the motor current reaches the maximum value I m；
And a fourth stage: t is t 3-t 4Auxiliary switch cut-off
At t 4At that time, the auxiliary switch is turned off, and the current is cut off.
4. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 3, wherein: the current waveform t measured by the open type current sensor 0-t 5And comparing each stage with the standard waveform of the current of the energy storage motor to judge the health state of the energy storage device.
5. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 4, wherein the method comprises the following steps: the open type current sensor can not acquire the current waveform of the energy storage motor and judges that the energy storage motor is burnt or the power supply loop of the motor has a fault.
6. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 4, wherein the method comprises the following steps: the open type current sensor can stably collect the current of the energy storage motor without t 2-t 4The current fluctuation of the stage is judged as the breakage of the chain of the energy storage motor, so that the energy storage motor runs in an idle running mode, and electricity is generatedThe output power is constant after the machine is started, and the current keeps a constant value.
7. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 4, wherein the method comprises the following steps: the open type current sensor collects that the current of the energy storage motor is unstable at a stage t2-t4, the situation that the energy storage mechanism slips is judged, and the output power of the motor is unstable after the motor is started.
8. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 4, wherein the method comprises the following steps: the amplitude of the current of the energy storage motor collected by the open type current sensor at the stage t2-t4 is small, and the judgment is that the output power of the motor is reduced and the energy storage spring generates fatigue.
9. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 8, wherein: after the energy storage spring is analyzed and judged to be fatigue, the output power of the motor in the energy storage process is calculated, so that the change of the coefficient k of the stiffness of the spring is deduced, and whether the energy storage spring is fatigue or not is determined.
10. The method for evaluating the health state of the energy storage device of the high-voltage circuit breaker based on the energy storage current analysis as claimed in claim 9, wherein the calculation derivation process is as follows:
the power supply voltage of the motor is U, and the power factor is
The work done by the motor in the whole energy storage process is W, then
Assuming that the energy storage spring normally works at the initial stage of commissioning, the work done by the energy storage motor is W0, when the energy storage spring is fatigued, the stiffness coefficient K becomes smaller, and the work required for compressing or stretching the spring with the same displacement becomes smaller, that is: w is less than W0; w < W0 × 96% is used as a suspected spring fatigue alarm, and W < W0 × 92% is used as a spring fatigue fault alarm.
Technical Field
The invention belongs to the high-voltage circuit breaker operation state detection technology, relates to the field of high-voltage circuit breaker energy storage device health state detection, and particularly relates to a high-voltage circuit breaker energy storage device health state assessment method based on energy storage current analysis.
Background
High voltage circuit breakers are essential devices in power plants and substation power distribution equipment as switching devices in power systems. When the circuit is normally operated, the circuit is used for carrying out switching operation mode, and the equipment or the circuit is connected into the circuit or quit the operation, thereby playing a control role. When equipment and lines have faults, the fault-free part can be quickly cut off, and the normal operation of the fault-free part is ensured, so that the fault-free part plays a protective role. The high-voltage circuit breaker has double tasks of control and protection in the power system, and the condition of the high-voltage circuit breaker directly influences the safe operation of the power system.
The switching-on and switching-off performance of the high-voltage circuit breaker is closely related to the arc extinguishing capacity of the arc extinguishing chamber and the performance of the operating mechanism, and the health state of the operating mechanism of the circuit breaker is important for judging whether the fault current of the system can be successfully switched on or off. In high-voltage and even extra-high-voltage circuit breakers, the matched operating mechanisms are three types: hydraulic, pneumatic, and spring. Wherein, the spring operating mechanism has small structure, flexible operation, no oil leakage and air leakage, and high reliability. Its advantages mainly include:
① require small power supply capacity;
② both AC and DC power supplies are applicable;
③ is operable once when power is temporarily lost;
④ are not affected by weather and voltage variations.
The disadvantages are also obvious, firstly, the structure is complex, and the number of parts is large; secondly, the requirements on the precision and the performance of parts are high, and particularly, the spring and the energy storage system have great influence on the on-off performance.
In recent years, spring operating mechanisms are increasingly used in high-voltage circuit breaker operating mechanisms, and an energy storage device of the spring operating mechanism mainly means that a closing spring or an opening spring is stretched to enable the closing spring or the opening spring to have corresponding potential energy. The quality of the energy storage device directly influences whether the breaker can normally complete the closing/opening action.
In the high-voltage circuit breaker spring operating mechanism, the number and the types of the springs are large, and the reliability of the high-voltage circuit breaker spring operating mechanism has important influence on the safe operation of equipment and a power system. If the output work of the spring is small, the speed of opening and closing the circuit breaker is too low, the opening and closing of the circuit breaker are not in place, and even the failure of opening and closing of the circuit breaker is caused. The performance of the spring affects the opening and closing performance of the circuit breaker, resulting in the occurrence of circuit breaker accidents. Therefore, the performance of the spring is regularly detected, so that the fatigue reliability of the spring is ensured, and the fatigue reliability is very important for the performance of the operating mechanism. At present, the detection of the state maintenance work carried out by national grid companies mainly focuses on a main transformer and important primary equipment, and an effective detection method for a circuit breaker energy storage mechanism is not available.
Therefore, it is desirable to provide a method for evaluating the health status of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis, which solves the above problems.
Disclosure of Invention
The invention aims to provide a method for evaluating the health state of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis, which is suitable for evaluating the state of the energy storage device of the high-voltage circuit breaker of a spring operating mechanism and aims to find the defects of the energy storage device of the circuit breaker through the analysis of the current change of an energy storage motor.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a health state evaluation method of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis is characterized in that an open type current sensor is clamped on a power line of a phase line of a stator winding of an energy storage motor, current in the whole process of motor operation is collected, a current value collected by the open type current sensor is transmitted to a mechanical characteristic tester, and the mechanical characteristic tester records the current waveform of the motor.
As a further improvement of the invention, the open type current sensor is arranged on an energy storage motor of the circuit breaker, when the circuit breaker acts, the energy storage motor works, the open type current sensor senses the current of a power line of the energy storage motor, and the open type current sensor records and uploads the current waveform to the mechanical characteristic tester. Comparing the measured current waveform with the standard current waveform of the energy storage motor, and judging the health state of the energy storage device;
the standard waveform refers to a standard characteristic waveform extracted from current waveforms of a large number of energy storage motors of the type in a normal state.
As a further improvement of the invention, the standard waveform of the current of the energy storage motor is divided into the following four stages:
stage one: t is t 0-t 1Starting process of motor
t 0The power is switched on at the moment, the energy storage motor is powered on, the motor starts to start without load after the power is switched on, and the motor starts to work stably after the starting stage of the motor is finished at t 1. This phase is characterized by a relatively high starting current I st；
And a second stage: t is t 1-t 2Stable working process
The motor starts to rotate but does not stretch the spring to do work at the stage in the process of stabilizing the current of the motor, so that the motor is in a no-load rotating state, the motor is in a stable working state, the current of the motor tends to be stable and basically unchanged, and the current of the motor is I a；
And a third stage: t is t 2-t 3Increase of load moment
The energy storage motor works at the stage to drive the closing spring to store energy, and the sum of the current at the stageLoad change is related, at t 3At the moment, the motor load moment is maximum, and the motor current reaches the maximum value I m；
And a fourth stage: t is t 3-t 4Auxiliary switch cut-off
At t 4At that time, the auxiliary switch is turned off, and the current is cut off.
As a further improvement of the invention, the current waveform t measured by the open type current sensor 0-t 5And comparing each stage with the standard waveform of the current of the energy storage motor to judge the health state of the energy storage device.
Specifically, when the open type current sensor cannot acquire the current waveform of the energy storage motor, the energy storage motor is judged to be burnt or the power supply loop of the motor has a fault.
Particularly, when the open type current sensor collects the stable current of the energy storage motor, and t does not exist 2-t 4When the current of the stage fluctuates, the chain of the energy storage motor is judged to be broken, so that the energy storage motor runs in an idle mode, the output power of the motor is constant after the motor is started, and the current keeps a constant value.
Specifically, when the open type current sensor collects that the current of the energy storage motor is unstable at a stage t2-t4, the energy storage mechanism is judged to slip, and the output power of the motor is unstable after the motor is started.
Specifically, when the amplitude of the current of the energy storage motor collected by the open type current sensor is smaller in the period from t2 to t4, the output power of the motor is judged to be smaller, and the energy storage spring is fatigue.
Furthermore, after the energy storage spring is analyzed and judged to be fatigue, the output power of the motor in the energy storage process is calculated, so that the change of the coefficient k of stiffness of the spring is deduced, and whether the energy storage spring is fatigue or not is further determined.
Further, the derivation process of the above calculation is as follows:
the power supply voltage of the motor is U, and the power factor is
The work done by the motor in the whole energy storage process is W, then
Assuming that the energy storage spring normally works at the initial stage of commissioning, the work done by the energy storage motor is W0, when the energy storage spring is fatigued, the stiffness coefficient K becomes smaller, and the work required for compressing or stretching the spring with the same displacement becomes smaller, that is: w < W0, specifically, W < W0 x 96% is generally used as a suspected spring fatigue alarm, and W < W0 x 92% is used as a spring fatigue fault alarm.
Compared with the prior art, the invention has the following beneficial effects:
1. the installation is detected conveniently: the breaker can be arranged, installed and detected in the operation process, power failure is not needed, and normal operation of a power grid is not affected;
2. the state evaluation is simple: the state of the equipment is judged through current change, components on the circuit breaker do not need to be disassembled, and even remote evaluation can be carried out;
3. and (3) online acquisition, avoiding information loss: the current can be acquired online in real time, and information loss in an offline state is avoided.
4. The trend can be prejudged, and the fault can be avoided: the invention compares the current waveform collected each time with the standard waveform, finds out the variation trend of the current, thereby judging the variation trend of the equipment defect, effectively avoiding the defect expansion and avoiding the fault occurrence.
5. The method of collecting current replaces direct measurement of the spring body, the method can be carried out without disassembling a breaker, and the current sensor adopts an open type sensor, so that an original circuit cannot be disconnected, and the operation is simple and convenient;
6. in the action process of the circuit breaker, the change of the output power of the motor is judged by collecting the current waveform of the energy storage motor, so that whether the spring is fatigue or not is judged, and the spring cannot be damaged.
Drawings
FIG. 1 is a schematic diagram of the present spring operating mechanism;
FIG. 2 is a standard curve of the current of the energy storage motor;
fig. 3 is a schematic diagram of a motor current test.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the case of not making a reverse description, these directional terms do not indicate and imply that the device or element being referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the scope of the present application; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of protection of the present application is not to be construed as being limited.
The invention provides a method for evaluating the health state of an energy storage device of a high-voltage circuit breaker through the current waveform of an energy storage motor.
As shown in fig. 1-3, the current waveform of the energy storage motor of the operating mechanism represents the whole process of the motor operation, the process comprises the stages of the motor starting process, the stable working process, the load moment increase, the auxiliary switch cut-off and the like, and the whole process of the motor operation is microscopically analyzed.
The energy storage motor current waveform can be divided into the following four phases:
(1) stage one: t-t 0-t1, motor start-up procedure
And electrifying at the time of t0, electrifying the energy storage motor, starting the motor to start without load after the power supply is switched on, and ending the starting stage of the motor at the time of t1 to ensure that the motor starts to work stably. This stage is characterized by a large starting current Ist;
(2) and a second stage: t is t1-t2, and the work process is smooth
At the stage, in the process of stabilizing the current of the motor, the motor starts to rotate, but the spring is not stretched to do work, so that the motor is in a no-load rotating state, the motor is in a stable working state, the current of the motor tends to be stable and basically unchanged, and the current of the motor is Ia;
(3) and a third stage: when t is t2-t3, the load moment is increased
The energy storage motor does work at the stage, the closing spring is driven to store energy, the current at the stage is related to the load change, the load moment of the motor is maximum at the moment of t3, and the current of the motor reaches the maximum Im;
(4) and a fourth stage: t3-t4, the auxiliary switch is turned off
At time t4, the auxiliary switch is opened and the current is cut off.
When the current waveform is analyzed, t0, t1, t2, t3, t4, Ia and Im can be used as characteristic parameters, and the change of the corresponding equipment state of the circuit breaker can be judged by comparing the change of the current characteristic parameters. The spring force versus stroke characteristics can also be estimated if the type of storage motor and the parameters and dimensions of the motor and associated mechanisms are known.
In addition, the working conditions of the energy storage motor and the load can be reflected by monitoring and comparing the starting current and the stable working current each time; the problems of the output reduction of the energy storage motor and the like can be judged through the change of the running time of the energy storage motor every time.
The invention adopts the open type current sensor to collect the current of the whole process of the motor operation, the open type current sensor is clamped on the power line of the energy storage motor, the signal of the current sensor is transmitted to the mechanical characteristic tester, and the mechanical characteristic tester records the current waveform of the motor.
The measuring device has the following characteristics:
(1) the measuring device is directly arranged on the circuit breaker and can be realized without disassembling the spring.
(2) The detection device is arranged in the running process of the circuit breaker, and the normal running of the circuit breaker is not influenced.
(3) The detection is real-time monitoring, and when the energy storage motor of the circuit breaker operates, data can be acquired, so that the integrity of the data is ensured.
(4) The data has continuity, can reflect the fatigue degree and the variation trend of the spring, not only ensures the economical efficiency of detection, but also can find the defects in time and prevent the defects from further worsening.
During the concrete test, when the circuit breaker moved, the energy storage motor worked, and at this moment the power cord had the electric current to flow through, after current sensor sensed the electric current, with the current waveform record to upload mechanical properties tester. And comparing each stage of the measured current waveform t0-t5 with the standard waveform to judge the health state of the energy storage device.
The invention extracts the characteristic parameter characteristics of the waveform by analyzing the current waveform of the energy storage motor, finds the change trend of the motor current and further evaluates the health state of the energy storage device of the circuit breaker.
A method for evaluating the health state of an energy storage device of a high-voltage circuit breaker based on energy storage current analysis comprises two links of detection and evaluation, and comprises the following steps:
firstly, the current of an energy storage motor of a circuit breaker operating mechanism is tested. The testing steps are as follows:
(1) clamping the open type current sensor on a power line of an energy storage motor;
(2) connecting a current sensor signal wire to a mechanical property tester;
(3) connecting a power line of the mechanical property tester;
(4) connecting a mechanical characteristic tester;
(5) when the breaker acts, the energy storage motor works, at the moment, current flows through the power line, and after the current sensor senses the current, the current waveform is recorded and uploaded to the mechanical characteristic tester.
(6) And comparing each stage of the measured current waveform t0-t5 with the standard waveform to judge the health state of the energy storage device.
Common failure sites for energy storage devices include: energy storage motor burnout, chain fracture, energy storage mechanism slip, etc.
The current waveform of the motor can not be acquired: the energy storage motor burns out or the power supply loop of the motor fails;
the current of the energy storage motor is smooth, and the current fluctuation at the stage of t2-t4 does not exist: the chain is broken, the energy storage motor runs in an idle mode, the output power of the motor is constant after the motor is started, and the current is kept at a constant value;
the current of the energy storage motor is unstable in the period from t2 to t 4: the energy storage mechanism slips, the output power of the motor is unstable after the motor is started, and the output power is large and small, so that fluctuation exists in the current of the motor.
The amplitude of the current of the energy storage motor at the stage t2-t4 is smaller: the output power of the motor is reduced, and the energy storage spring generates fatigue.
Specifically, assume that the supply voltage of the motor is U and the power factor is The power of the energy storage motor is P ═ UI
assuming that the energy storage spring of the circuit breaker normally works at the initial commissioning stage, the work done by the energy storage motor in the energy storage process of the circuit breaker operating mechanism is W0. If the energy storage spring of the operating mechanism generates fatigue along with the increase of the service life, the stiffness coefficient K of the energy storage spring is correspondingly reduced, and the work required for compressing or stretching the spring with the same displacement is reduced, namely: w is less than W0.
When W becomes smaller than the initial period of operation, the work performed by the motor becomes smaller, and when the failure of the transmission system is eliminated, the energy storage spring becomes fatigued.
In particular, in the application, W < W0 × 96% is generally used as a suspected spring fatigue alarm, W < W0 × 92% is used as a spring fatigue fault alarm, and an alarm threshold value and the basis for shutdown troubleshooting and maintenance can be adjusted according to actual conditions in the actual operation and maintenance process.
In addition, the change of Ia is suitable for identifying the defects and faults of the energy storage motor. The defect which is difficult to find by the energy storage motor is the turn-to-turn short circuit problem caused by the turn-to-turn insulation damage of the internal coil. The internal turn-to-turn short circuit causes the number of coil turns to become small, resulting in an increase in the torque constant (an increase in the current required to obtain the same torque). Ia is the steady-state current of the motor in idle smooth rotation, so the increase of Ia can be used as a method for identifying the insulation problem of the coil in the motor.
The invention adopts an on-line monitoring mode to monitor the current of the energy storage motor of the circuit breaker in real time and ensure the integrity and continuity of detection data, thereby analyzing and judging the trend of the defects of the energy storage device, not only realizing the economical efficiency of equipment replacement, but also avoiding the expansion of the defects.
The foregoing examples, while indicating preferred embodiments of the invention, are given by way of illustration and description, but are not intended to limit the invention solely thereto; it is specifically noted that those skilled in the art or others will be able to make local modifications within the system and to make modifications, changes, etc. between subsystems without departing from the structure of the present invention, and all such modifications, changes, etc. fall within the scope of the present invention.