Patent ID: 12255033

The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

PREFERRED EMBODIMENTS OF THE INVENTION

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. Note, the headings are for organizational purposes only and are not meant to be used to limit or interpret the description or claims. Furthermore, note that the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not a mandatory sense (i.e., must).” The term “include”, and derivations thereof, mean “including, but not limited to”. The term “connected” means “directly or indirectly connected”, and the term “coupled” means “directly or indirectly connected”.

FIG.1illustrates an exemplary circuit breaker which can be on-line monitored by the method according to an embodiment of the present invention. The circuit breaker as shown inFIG.1is a vacuum circuit breaker, comprising a stationary contact and a movable contact (not shown) enclosed in an insulation pole1, and an actuating mechanism2for actuating the closing and opening action of the movable contact. The actuating mechanism2has a plurality of elements including a linkage mechanism and a spring. The linkage mechanism is for transmitting a driving force from an active element for example, a motor or the spring actuator, to the movable contact. As shown inFIG.1, for example, the linkage mechanism may be a four-bar linage which comprises a first lever21, a second level22, a third lever23pivotally connected to each other in sequence. The first lever21is connected to a driving shaft20driven by an active element, and the third lever23is pivotally connected to a fixed point25on the base of the circuit breaker. For example, the fixed point25may be one of the fulcrums of the linkage mechanism. A push rod24on one end is pivotally connected to the movable contact at a distance from the pivot point between the third level23and the fixed point25. The other end of the push rod24is connected to the movable contact in the insulation pole1. By driving the driving shaft20rotating via the motor or the spring, the movable contact can be moved up and down in a longitudinal direction in the pole1by the force transmission from the first lever21, the second level22, the third lever23and the push rod24, so as to contact or be separated from the stationary contact and thus close or open the circuit.

FIG.2illustrates the force applied on the linkage mechanism of the circuit breaker as shown inFIG.1. In a balanced closed state of the circuit breaker, the movable contact abuts against the stationary contact under a force from the linkage mechanism. In this case, the stationary contact would apply a counter force F2(also referred to as contact force) on the movable contact which is in turn conducted to the third lever23through the push rod24. Once the movable contact is separated from the stationary contact in the opening period, the counter force F2on the movable contact, the push rod24and the third lever23would decrease dramatically and even become zero. Likewise, during the closing period of the circuit breaker, the counter force F2applied on the movable contact by the stationary contact would dramatically from zero to a relative high value.

FIG.3AandFIG.3Bare graphs of an exemplary travel curves of a circuit breaker respectively in normal condition and defective condition for an opening operation.FIG.3Cillustrates a comparison of the travel curves fromFIG.3AandFIG.3B. A circuit breaker having the defect can still operate but will eventually develop into a failure. A defect stage occurs between normal stage and failure stage. The graph ofFIG.3A,FIG.3BandFIG.3Cinclude an x-axis indicative of time and a y-axis illustrating travel at each corresponding unit of time, and the travel curve30presents the normal operation and the travel curve31presents the defective operation. A group of operating conditions covers the circuit breaker timing. Timing is explained inFIG.3A,FIG.3BandFIG.3Cfor the opening operation. The operating conditions include at least one of: opening/closing speed of a movable contact of the circuit breaker, total travel of the movable contact, timing of the opening/closing, travel of the movable contact, and over travel of the movable contact. The opening/closing speed of a movable contact of the circuit breaker is calculated between two points on the travel curve as defined by the speed calculation zone. The speed calculation zone is part of the circuit breaker type specific default settings and matches the points used for off-line timing. The total travel of the movable contact refers to the distance traveled from minimum to maximum position, so it includes over travel of the movable contact. The timing of the opening/closing refers to the time calculated between the two points on the travel curve as defined by the speed calculation zone. The travel of the movable contact refers to the distance from where the movable starts to move until it reaches a position where the arcing contacts meet per design. This position is referred to as the “travel” and is measured from the fully closed position. The operation cycle covers a period when the circuit breaker starts from closing to opening or vice versa.

It can be observed that there exists a first dissimilarity between the normal travel curve30and the defective travel curve31in terms of each of the operating conditions. This holds true for closing operation, as well. The skilled person should understand that such dissimilarity can be used as indicator for the defect occurring in the circuit breaker.

FIG.4AandFIG.4Bare graphs of an exemplary traces of low-frequency components of the force applied to the fixed point of the element of the actuating mechanism of the circuit breaker respectively in normal condition and defective condition for an opening operation.FIG.4Cillustrates a comparison of the exemplary traces fromFIG.4AandFIG.4B. The graphs ofFIG.4A,FIG.4BandFIG.4Cinclude an x-axis indicative of time and a y-axis illustrating the force at each corresponding unit of time, and the force curve40presents the normal operation and the force curve41presents the defective operation. When comparing the travel curve30ofFIG.3Aand the force curve40ofFIG.4A, it can be observed they resemble each other. When comparing the travel curve31ofFIG.3Band the force curve41ofFIG.4B, it can be observed they resemble each other, as well. In particular, in either of the force curves40,41ofFIG.4AandFIG.4B, its operating condition related parameters may be observed and calculated, which correspond to and reflect the operating conditions concerning the respective one of the travel curves30,31ofFIG.3AandFIG.3B. Therefore, the first dissimilarity involving the travel curves30,31ofFIG.3AandFIG.3Bmay find its counterpart (a second dissimilarity) involving the force curves40,41ofFIG.4AandFIG.4B. In other words, it is possible to derive the first dissimilarity by calculating and monitoring the second dissimilarity, which in turn may be used to indicate the defect occurring in the circuit breaker.

FIG.5is a schematic illustration of an apparatus for monitoring a circuit breaker ofFIG.1according to an embodiment of present invention. As an example, the element23of the actuating mechanism2, and the actuating mechanism2may be a linkage mechanism21,22,23having the fixed point25as one of its fulcrums, and its third level23is pivotally engaged with the fixed point25. The force applied between the third level23and the fixed point25will be used for monitoring the condition of the circuit breaker. As an alternative, the element may be of the spring. The apparatus5includes a force sensor50, a microprocessor51and a memory52. An internet of things may include the circuit breaker, the apparatus for monitoring the circuit breaker according to any embodiments of present invention, and a server having the microprocessor of the apparatus for monitoring the circuit breaker.

FIG.6shows a mechanical arrangement of the force sensor and the actuating mechanism according to an embodiment of present invention. The force sensor50may be configured to measure a force applied to the fixed point25of the element21,22,23of the actuating mechanism2of the circuit breaker in present operation cycle and generate a first data set representing the measurement of the force F1in the present operation cycle. The force F1may be divided into two components, including the horizontal component F1xand the vertical component F1y. In this embodiment, for example, the force sensor50may be shaped like a rectangular cuboid. The force sensor50includes a pair of ears501,502extending from one of the two faces. The ears501,502each has a fastening means B1, B2for fixing the force sensor50to a frame of the vacuum circuit breaker as shown inFIG.1such that the force sensor50may be secured relatively stable with respect to the stationary contact of the circuit breaker. The fastening means B1, B2, for example, may be a bolted joint for assembly of the ears501,502of the force sensor50and the frame of the vacuum circuit breaker. Because any relative movement between the two can be avoided due to the fastening means B1, B2, the body of the force sensor50may be used as the fixed point25(the fulcrum) of the linkage mechanism21,22,23. The force sensor50has a hole500formed through two of its faces. The internal surface of the hole500may be formed with material whose characteristics changes when a force or pressure is applied, for example the so-called “force-sensitive resistor”. They are normally supplied as a polymer sheet or ink that can be applied by screen printing. The element23(the third lever) of the actuating mechanism2may have a hole230at one of its ends, and be pivotally coupled with the force sensor50(behaving as the fulcrum) via a pin231arranged through both of the hole230of the element23and the hole50of the force sensor50. During an operation of opening/closing of the vacuum circuit breaker, due to the pivotal engagement, the force exerted by the third lever23to the force-sensitive part of the force sensor50(the internal surface of the hole500) may be measured, giving the force curves as exemplified inFIG.4AandFIG.4B.

FIG.7is a graph of an exemplary traces of the force applied to the fixed point of the element of the actuating mechanism of the circuit breaker respectively in normal condition and defective condition for an opening operation. For example during the opening operation, the measurements of the force F1is transmitted to an input of a low-pass filter53of the microprocessor51. The low-pass filter53envelopes the measurements of the force F1to facilitate reducing high frequency noise and facilitate reducing unwanted non-peak related signal information. The output of the low-pass filter53may be represented by the graphs as shown inFIG.4AandFIG.4Bin normal condition and defective condition for the opening operation. The output of the low-pass filter53is transmitted to a digital input of microprocessor51as the operating condition related parameters of the element in the closing operation.

As mentioned above, by monitoring the second dissimilarity involving the force curves40,41ofFIG.4AandFIG.4Brespectively representing the normal condition and defective condition of the circuit breaker, the operation condition of the circuit breaker may be determined. Based on this principle, the microprocessor51may be configured to judge a health condition of the circuit breaker in consideration of normal operating condition related parameters of the element according to a history profile when the circuit breaker operated normally and current operating condition related parameters of the element in the present operation cycle extracted from the force represented by the first data set.

For example, the history profile may be stored in the memory52. The microprocessor51may be further configured to obtain a second data set representing force applied to the fixed point in a plurality of operation cycles from the history profile and extract operating condition related parameters for each of the operation cycles from the force represented by the second data set. In this embodiment, an offline normal data set {C_1, C_2,n. . . , C_n} of the target circuit breaker may be stored in the memory52(the second data set), while C_i (i=1, 2, . . . , n) each represents the force curve measured by the force sensor50in a respective one of the n normal operation cycles. From the low-frequency components of the n force curves, by applying finger print creation method, the operating condition related parameters of the element23of the actuating mechanism2may be observed and calculated. In order to get the low-frequency components, the extraction of the operating condition related parameters may be adapted to low-frequency extraction, for example, by a low-pass filter. Such operating condition related parameter being extracted from the second data set, for example, concern with at least one of: opening/closing speed of a movable contact of the circuit breaker, total travel of the movable contact, timing of the opening/closing, travel of the movable contact, and over travel of the movable contact. Therefore, each component of the second data set C_i can be transferred to X_i including at least of the operating condition related parameter. Also, the offline normal dataset {C_1, C_2, . . . , C_n} becomes {X_1, X_2, . . . , X_n}.

The microprocessor51may be further configured to divide the second data set {C_1, C_2,n. . . , C_n} into two groups respectively corresponding to a first number and a second number of the plurality of operation cycles from the history profile. In this embodiment, for example, the offline normal second data set is evenly split into two parts, and the operating condition related parameters may be divided into D and D*accordingly, while D includes features of some normal samples in the first number, and D*includes features of the rest of the samples in the second number. D is considered as a benchmark matrix for residual calculation, and D*will be used for threshold determination.
D={X1,X2, . . . ,Xm}  (1)
D*{Xm+1,Xm+2, . . . ,Xn}  (2)wherein: the first number counts from 1 to m, and the second number counts from m+1 to n.

In terms of the operating condition related parameter D and D*, the microprocessor51may be configured to identify historical dissimilarity involving the respective one of the second number of the operation cycles and the first number of the operation cycles. In this embodiment, for example, the historical dissimilarity of each measured data Xtcan be calculated:

Rt=mean⁡(DT⊗Xt)(3)DT⊗Xt=[X1T⊗Xt⋮XmT⊗Xt](4)X⊗Y=∑i=1t⁢(xi-yi)2(5)where Stis the calculated dissimilarity.

In terms of the operating condition related parameter, the microprocessor51may be further configured to identify current dissimilarity, which is the dissimilarity of timely monitored data to historical normal data, involving the current operation cycle and the first number of the operation cycles. In this embodiment, for example, the microprocessor51may calculate the historical dissimilarity set Rtrain=[Rm+1, Rm+2, . . . , Rn] of all the feature vectors in D*, according to equation (3). Threshold value is determined as,
Thre=N·max(Rtrain)  (6)where N is recommended to be 3˜4.

The microprocessor51may be configured to give the judgement of the health condition of the circuit breaker based on a comparison of the historical dissimilarity and the current dissimilarity. In this embodiment, for example, the status determination is quite straight forward—for any measured data Xt, the corresponding status is abnormal if Rt>Thre, otherwise is normal.

During each operation cycle, the force measured at a fixed point of the actuating mechanism models the health condition of the circuit breaker, which varies from normal condition to defective condition of the actuating mechanism. By measuring and analysing the force during each operation cycle, a health condition of the actuating mechanism, which corresponds to a dissimilarity between current condition and historical healthy condition in terms of the operating condition related parameters, may be determined.

A technical effect of the circuit breaker monitoring apparatus and methods described herein featured in terms of high accuracy because of using force sensor and proper time-frequency analysis method, high intelligence due to automatic model developing based on data-driven solutions.

Though the present invention has been described on the basis of some preferred embodiments, those skilled in the art should appreciate that those embodiments should by no way limit the scope of the present invention. Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore fall in the scope of the present invention which is defined by the accompanied claims.