Patent ID: 12228596

DETAILED DESCRIPTION

Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a curve50′ showing voltage as a function of time is illustrated inFIG.1A. It can be seen that the curve50′ comprises a plurality of spikes52. Moreover, the curve50′ comprises harmonics that deviate from a sine waveform. Accordingly, the curve50′ represents an example of poor power quality.

FIG.1B, on the other hand, illustrates a graph depicting voltage curve50as a function of time. The curve50represents an example of good power quality since the curve50fulfils the following criteria:a) the supply voltage is steady and stays within the prescribed range,b) the AC frequency is close to the rated value; andc) the voltage curve is a smooth sine waveform.

As previously mentioned, in practice it is difficult and expensive to locate the source (electric device) causing a poor power quality (such as the one shown inFIG.1A) because the prior art solutions must be electrically connected to the multiconductor electricity cables. Accordingly, the prior art solutions are difficult and costly to install.

FIG.2illustrates a power quality analysis system2according to an embodiment of the invention. The power quality analysis system2is configured to carry out a power quality analysis in an electrical environment4. The electrical environment4comprises a plurality of power consuming units6,6′,6″,6′″ each being electrically connected to a main power supply8by means of a multiconductor cable12.

The electrical environment4comprises a plurality of clamp-on power quality sensors10arranged and configured to provide one or more power quality analysis measurements. The power quality sensors10are configured to provide one or more power quality analysis measurements when clamped onto the outside of or arranged in the proximity of one of the multiconductor cables12. The clamp-on power quality sensors10are configured to provide the one or more power quality analysis measurement without being electrically connected to any of the conductors of the multiconductor12. Accordingly, it is easier and less expensive to install these sensors10than the prior art sensors. Moreover, the sensors can easily be removed and arranged elsewhere in the electrical environment4.

The multiconductor cables12are electrically connected to a main power supply8. In an embodiment, the main power supply8is the mains.

By arranging the power quality sensors10in selected positions within the electrical environment4, it is possible to locate devices that cause poor power quality. Accordingly, the power quality analysis system2makes it possible to locate the electric device(s)6,6′,6″,6′″ that cause the undesired power quality issues. Thus, by using the power quality analysis system2resources and money can be saved.

FIG.3illustrates another power quality analysis system2according to an embodiment of the invention. The power quality analysis system2basically corresponds to the one shown inFIG.2. The power quality analysis system2, however, comprises a central power quality unit sensor14arranged and configured to measure the over-all power quality of the electrical environment4. Moreover, it can be seen that the main power supply8is electrically connected to the multiconductor cables12through a multiconductor cable13having a plurality of conductors. The central power quality unit sensor14is electrically connected to the connectors of the multiconductor cable13.

FIG.3moreover illustrates how a system2according to an embodiment of the invention can be used to measure current flow in a main multiconductor cable13and in a number of smaller multiconductor cables12.

The power supplied to the installation is metered by means of a single central power quality unit sensor (one main meter)14that provides measurements of high precision (e.g. approved by authorities or within standards for power measurements). The main multiconductor cable13is electrically connected to a plurality of smaller multiconductor cables12, while a number of power quality sensors10are attached to the outside of some of these multiconductor cables12.

In the following, we take a look at the metering at a single power quality sensor10′. The power quality sensor10′ comprises one or more current sub-sensors and/or one or more voltage sub-sensors. Thus, the sensor signal changes with the current/voltage/power flow in the multiconductor cable12.

In an embodiment, the clamp-on power quality sensors are configured to measure the currents flowing in the multiconductor cables by an array of one or more magnetic measurement sub-sensor(s), e.g., coils or Hall-effect sensors.

It may be an advantage to use multiple current sub-sensors in the power quality sensor to enable measurement of different superpositions of the magnetic fields generated by the currents flowing through the different conductors of the multiconductor cable, and thereby establish that the different currents are distinct from each other.

In an embodiment, the clamp-on power quality sensors are configured to measure the voltage in the multiconductor cable by an array of one or more electric field measurement sub-sensor(s), e.g. capacitive plates, capacitive probes or antennas.

It may be an advantage to use multiple voltage sub-sensors in the power quality sensor to enable measurement of different superpositions of the electric fields generated by the voltage in the different conductors of the multiconductor cable, and thereby establish that the different voltages are distinct from each other.

The signal from the power quality sensor10′ depends on the material and the dimension of the multiconductor cable12, the sensor attachment and the electricity supply. Accordingly, and the sensor signal must be “transformed” or “adjusted/calibrated” to give the actual flow (the flow that would be achieved by using a high precision meter). In a prior art system, it would be necessary to apply “a high quality sensor” configured to measure flow in the specific environment (the dimensions of the multiconductor cable12, the material of the multiconductor cable12and attachment type).

Since the present systems and methods apply a mathematical statistical model, it is possible to use a “simple” power quality sensor10′ to determine the current and/or voltage in each single conductor at the multiconductor cable12. Accordingly, the use of a mathematical statistical model makes it possible to compensate for the mixed signals measured from the outside of multiconductor cables, and thereby allows for usage of the low precision and mixed signal measurements of the clamp-on power quality sensor10′.

The power quality sensor10′ is attached to the outside of the multiconductor cable12and hereafter it is possible to sample a series of measurements from the power quality sensor10′ over a timespan.

In the same timespan, a series of measurements is sampled from the central power quality unit sensor (main meter)14.

The mathematical statistical model is used to estimate the part of the central power quality unit sensor (main meter)14current that flows through the multiconductor cable12having the power quality sensor10′ attached to it. It is possible to carry out a time-dependent transformation of the measurements of power quality sensor10′ in order to correct for the actual environment of the power quality sensor10′.

A less computer demanding approach can be obtained by using a mathematical statistical model to estimate if a time-independent transformation can be used. It may be an advantage to use the time-independent transformation, rather than the full mathematical statistical model, on the running measurements from the power quality sensor10′.

It may be beneficial from time to time, to test if the precision of the transformation is acceptable, and update it if needed, using the mathematical statistical model.

The necessary number of samples needed can be obtained by estimating the measurement error of the transformation. In this manner, the results can be detained until the desired precision is obtained.

In the following, one method to estimate the latent stochastic process using a mathematical statistic model is described. The latent stochastic process can be modelled by e.g. a state space model defined by
Yt=Ftθt+εtεt˜N(0,Vt)  (1)
θt=Gtθt-1+ϑtϑt˜N(0,Wt)  (2)
where Ytis a vector determining (e.g. describing, or defining) the observed process at time t, comprising observed data from the sensor (10,10′) and/or the meters14,14′,14″ (seeFIG.5); θtis a vector determining the latent stochastic process at time t, comprising latent process data, such as harmonics generated, device health status, current/voltage spikes, etc; Ftis the regression matrix which determines the linear relation between the latent process and the observed process at time t; Gtis the evolve matrix which determines the linear transition from time t−1 to time tin the latent process; εtand ϑtare zero mean multivariate Gaussian distributed noise vectors of the observed process and the latent process respectively; Vtis the observation variance-covariance matrix; and Wtis the evolution variance-covariance matrix.

The model parameter matrices Ftand Gtmay be estimated by e.g. the Kalman filter, using prior data from the modelled system and/or similar systems, hereunder the data provided by the user and/or experts in the field. Standard statistical methods can be used to conduct inference (e.g. estimate information) on the process. The information can be e.g. an estimated signal (e.g. trend) and/or forecasts (e.g. prognosis) of the process, and the related distributions of the estimates, variance and/or confidence intervals. Using these kinds of estimates, it is easy to e.g. raise warnings and/or alarms. For example, an alarm can be chosen to appear if the probability of an observed deviation in the process is less than 0.1% probable to occur by change.

The above model framework is a special case of the more general model framework
Yt=ft(θt)+εtεt˜δ1(Vt)  (3)
θt=gt(θt-1)+ϑtϑt˜δ2(Wt)  (4)
where ftand gtare general functions, δ1and δ2are general statistical distributions, and all other terms are as described above.

Inference on this more general model framework can be conducted by e.g. the extended Kalman filter in cases where the relation between the latent process and the observed process is non-linear, and the Kalman-Bucy filter in cases where the time is defined (e.g. described) on a continuous scale.

Other time series analysis method and/or multivariate data-analysis methods, such as Analysis of Variance (ANOVA), Markov models, Generalized Linear Models (GLM), and Multivariate Gaussian Models may as well be used to estimate the said latent stochastic process, and infer the said information.

FIG.4Aillustrates a close-up view of a power quality sensor10according to an embodiment of the invention. The power quality sensor10is attached to the outside of a multiconductor cable12having a circular cross-section and comprising three conductors16,18,20surrounded by an insulator.

The power quality sensor10comprises a built-in energy harvesting device comprising patch members22,24,26that are electrically separated by a separation member28. The patch members22,24,26can also serve as voltage sub-sensors to measure the voltage in the multiconductor cable.

The power quality sensor comprising the energy harvesting device can be attached to the multiconductor cable12by any suitable means. In an embodiment, the power quality sensor is attached to the outside of the multiconductor cable12by means of glue. In another embodiment, the power quality sensor is attached to the outside of the multiconductor cable12by means of one or more mechanical structures.

The energy harvesting device is configured to harvest electrical energy from the cable12and supply the power consuming power quality sensor10with electrical power.

It is an advantage that the power quality sensor10is configured to be mounted on a cable12by means of glue or other mechanical attachment means allowing for a quick non-invasive attachment of the power quality sensor10to the cable12.

FIG.4Billustrates a close-up view of another power quality sensor10according to an embodiment of the invention. The power quality sensor10is attached to the outside of a multiconductor cable12comprising three conductors16,18,20surrounded by an insulator. The power quality sensor10comprises mechanical locking structures38,38′ configured to maintain the power quality sensor10in a closed configuration. The power quality sensor10is cylindrical and comprises a first portion I and a second portion II rotatably or slidably attached to each other.

The power quality sensor10comprises a communication unit (not shown) configured to send wireless signals36. Accordingly, the power quality sensor10can communicate with one or more external devices.

FIG.4Cillustrates a close-up view of another power quality sensor10according to an embodiment of the invention. The power quality sensor10is attached to the outside of a multiconductor cable12comprising three conductors16,18,20surrounded by an insulator. The power quality sensor10is attached to the multiconductor cable using cable ties.

The power quality sensor10comprises a communication unit (not shown) configured to send wireless signals36. Accordingly, the power quality sensor10can communicate with one or more external devices.

FIG.5illustrates a power quality analysis system2according to an embodiment of the invention. The power quality analysis system2comprises a plurality of electrical devices6,6′,6″,6′″ each being electrically connected to a main power supply (not shown) by means of a multiconductor cable12. A power quality sensor10is clamped onto the outside of each of the multiconductor cables12. In another embodiment, the power quality sensors10may be arranged in the proximity of the multiconductor cables12.

Each power quality sensor10is configured to send a wireless signal36comprising information about the measurements made by the power quality sensor10. The signals36are received by a router42that is configured to receive information from three power quality units14,14′,14″. The power quality units (meters)14,14′,14″ are arranged and configured to measure the over-all power quality of the electrical environment, in which the electrical devices6,6′,6″,6′″ are installed.

The power quality analysis system2comprises a user interface54. The user interface54is configured to provide access to generated information such as warnings, alarms and measurements of at least a selection of the electrical devices6,6′,6″,6′″. The router42is communicating wirelessly with the user interface54that is represented by a smartphone.

The power quality analysis system2comprises a control unit40. The router4is arranged and configured to communicate wirelessly with the control unit40. The control unit40may be an actuator capable of regulating the activity of one or more of the electrical devices6,6′,6″,6′″, or another device. Regulation of the activity of one or more of the electrical devices6,6′,6″,6′″ may be carried out by changing the speed (of a pump or a motor) or by shutting down one or more of the electrical devices6,6′,6″,6′″ by way of example.

The power quality analysis system2comprises a data storage unit46and a calculation unit configured to carry out calculations by using one or more predefined mathematical statistical models48. In an embodiment, the power quality analysis system2comprises a cloud service44comprising the data storage46configured to store information received from the router42or data modified or calculated by the cloud service44. In an embodiment, the cloud service44comprises the calculation unit configured to carry out calculations using the predefined mathematical statistical model48. In an embodiment, the mathematical statistical model48is configured to estimate and/or forecast the impact of one or more of the devices6,6′,6″,6′″ of the system2.

Any suitable mathematical statistical model48may be applied and the mathematical statistical model48may conduct inference on combined data from one or more of the sensors10and from one or more of the power quality units14,14′,14″ to estimate and/or forecast the activity of one or more of the devices6,6′,6″,6′″.

FIG.6Billustrates a power quality sensor10clamped on a multiconductor cable12of an electric device6′.FIG.6Aillustrates a close-up view of the power quality sensor10shown inFIG.6B.

It can be seen that the power quality sensor10transmits a wireless signal36. This signal36generally includes information about the measurements made by the power quality sensor10. The signal36is received by a calculation unit configured to carry out calculations using a predefined mathematical statistical model.

The power quality sensor10comprises a wireless transducer32configured to transmit wireless signals36. The power quality sensor10comprises an energy harvester34configured to harvest energy (e.g. from the electric field of the cable12). The power quality sensor10comprises a power manager30configured to manage the power harvested by the energy harvester34.

FIG.7Aillustrates a power quality sensor10according to an embodiment of the invention. The power quality sensor10comprises a plurality of sub-sensors56,56′,56″,56′″,60. In an embodiment, the sub-sensors56,56′,56″,56′″,60comprise a main sensor member60and several additional sensor members56,56′,56″,56′″. The main sensor member60is electrically connected to the additional sensor members56,56′,56″,56′″ by means of an electrical connector58.

The main sensor member60and each of the additional sensor members56,56′,56″,56′″ are configured to detect an electromagnetic field caused by a current/voltage running in an underlying structure. By having several sensor members60,56,56′,56″,56′″, it is possible to arrange the sensor members60,56,56′,56″,56′″ in different tangential positions around a multiconductor cable12as shown inFIG.7C. Hereby, it is possible to process data from the sensor members60,56,56′,56″,56′″ (e.g. by means of a signal processing unit (not shown) in order to separate the measured signals (the sum of magnetic fields created by current running through each of the conductors of the multiconductor cable12, or voltage at the conductors) into contributions from each of the conductors of the multiconductor cable12. In this way it is possible to, in case of a power quality distortion, detect which of the conductors of the multiconductor cable12causes the power quality distortion. This is a major advantage over the prior art because no electrical connection to the conductors of the multiconductor cable12is needed and because the power quality sensor10functions when clamped onto the outside of or arranged in the proximity of the multiconductor cable12.

In an embodiment, the main sensor member60comprises an integrated communication unit (not shown). In an embodiment, the main sensor member60is configured to receive signals from the additional sensor members56,56′,56″,56′″ and to transmit the signals measured by the main sensor member60as well as signals from the additional sensor members56,56′,56″,56′″ to a receiving device either through a wired connection or through a wireless connection.FIG.7Billustrates a multiconductor cable12onto which a power quality sensor10, such as the one shown inFIG.7A, is configured to be clamped.

FIG.7Cillustrates the power quality sensor10shown inFIG.7Aattached to (clamped onto) the multiconductor cable12shown inFIG.7B. It is possible to use any suitable attachment structures to attach the power quality sensor10to the multiconductor cable12. In an embodiment, the power quality sensor10is attached to the power cable12by means of one or more cable ties (not shown). A shield structure generally surrounds the power quality sensor10and the entire circumference of the part of the multiconductor cable12at which the power quality sensor10extends. In an embodiment, the power quality sensor10may be clamped onto the outside of or arranged in the proximity of a multiconductor cable12that does not comprise a shield structure.

The shield structure, however, may be used to isolate the power quality sensor10and the multiconductor cable12electrically from the environment through which the multiconductor cable12runs. In an embodiment, the shield structure is a conductive enclosure used to block electrostatic fields.

The main sensor member60and the additional sensor members (sub-sensors)56,56′,56″,56′″ may be designed as coils and/or Hall-effect sensors and/or capacitive probes, which are placed in such a manner that the different sensor members (sub-sensors)60,56,56′,56″,56′″ measure different superpositions of the combined electromagnetic fields induced by the conductors inside the multiconductor cable12.

LIST OF REFERENCE NUMERALS

2Power quality analysis system4Electrical environment6,6′,6″,6′″ Power consuming unit8Main power supply10,10′ Power quality sensor12,13Multiconductor (multicore) cable14,14′,14″ Power quality unit16,18,20Conductor22,24,26Patch member28Separation member30Power manager32Wireless transducer34Energy harvester36Signal38,38′ Mechanical locking structures40Control unit42Router44Cloud service46Data storage48Mathematical statistical model50Curve52Spike54User interface56,56′,56″,56′″ Additional sensor member (sub-sensors)58Connector60Main sensor member (one of the sub-sensors)