CH709416B1 - Method and device for permanent current measurement in the cable distribution cabins of the 230 V / 400 V network level. - Google Patents

Abstract

The inventive method is used for permanent, non-contact measurement of currents on a single-conductor or multi-conductor sheath (6) by a) a sleeve around the sheath (6) is applied so that they the sheath (6) with their in-lying conductors (7 b) the magnetic fields generated due to the current flowing in the enclosed insulated conductors (7) are measured by the magnetic field sensors and detected as electronic data, c) by means of empirically previously determined algorithms for the relation between the currents in the individual conductors (7) and the magnetic fields generated thereby effectively flowing currents in the individual conductors (7) are calculated as a data basis for the management of power distribution networks and forwarding to a server. An apparatus according to the invention for implementing the method includes a sleeve which can be fastened around a single-conductor or multi-conductor jacket (6), in which a plurality of magnetic field sensors distributed over its circumference are arranged.

Description

Description: The invention relates to a method for permanent indirect current measurement at the distribution booths of the 230 V / 400 V network level, in order to be able to record data about the currents flowing in or out there, and to use the data obtained for the network control can that the networks can be operated more stable and homogeneous. The invention also relates to a special device for indirect current measurement in order to be able to implement this method.

The communicative networking of all parties involved in the electricity market to form an overall system with higher-level network management is referred to as a smart grid (“intelligent power network”). All data from power generators, storage systems, network operators and consumers are measured, evaluated, monitored and managed in real time, with the aim of keeping the power generation and network load as homogeneous as possible by skillful control of power and storage plants.

It is now becoming increasingly common for decentralized power generation plants to be connected to the transmission and distribution network. These are mostly smaller energy suppliers who generate their electricity from fossil fuels or from renewable sources such as photovoltaics, solar thermal, wind power or other processes. Such systems mostly feed the electricity generated directly into the lower voltage levels, predominantly into the low-voltage network, which requires an increasingly complex structure of the underlying system operation so that network stability is still guaranteed.

Relevant for the smart grids are, in particular, status information and load flow data from generating plants, consumers and transformer stations. So-called smart meters have so far been used to feed the relevant data into the communication network on the part of the end user. The latter measure the effective power consumption as well as the usage time of the end consumer and pass on the information via the built-in remote communication to the responsible energy supply company.

The smart metering method has been used since the 1990s. While in the past such intelligent electricity meters were only installed for large consumers, they have increasingly been used in households for some years now. There are already numerous countries that legally prescribe the use of intelligent meters in the context of feasibility and economy, especially in the European Union. But the USA, Canada, Turkey, Australia and New Zealand have either already implemented or at least decided to use smart meters on a larger scale. The trend towards collecting electricity consumer data is clearly recognizable.

A disadvantage of the smart metering method is its unprofitability. It is emphasized at the legal level that the use of electricity meters should be proportionate in view of the potential electricity savings. In fact, the studies show that the intelligent electricity metering method is far from worthwhile based on economic criteria. The available figures indicate operating costs that are 20 to 30 times higher than the amounts of money in potential electricity savings estimated by the energy suppliers.

The installation of a smart meter requires the admission of an installer in company or private premises, and after installation, the intelligent meter must be serviced regularly so that its reliability is also guaranteed. In addition to the pure costs of maintenance operations when intelligent counters are used across the board, the need for personnel and time for maintenance should not be underestimated. In particular, if every single household is to be equipped with such an electricity meter in the future, this means enormous personnel expenditure on the part of the operating companies and thus inefficient management.

Dealing with smart metering is also critical from other points of view. In particular, data misuse cannot be ruled out if sensitive data from thousands of individual households is transmitted to a central server. The consumer profiles can be used to draw fairly precise conclusions about the lifestyle of customers. This goes so far that even a television program consumed can be reconstructed due to its specific variation in power consumption. There are numerous problems that can arise with the digitization of such sensitive data, even retrospectively. In this respect, the fear that smart metering favors the development of a society made up of “transparent” citizens seems perfectly justified.

One of the greater challenges of status data acquisition in the distribution network arises due to the decentralized power generation systems mentioned in section [0003], which cause an increasingly polydirectional load flow. Detecting, monitoring and possibly regulating this is a non-trivial task that the smart meters cannot accomplish without a comprehensive rollout. Thus, the data material provided today for network planning, network analysis, network operation and network management is inadequate at the distribution network level. At the deepest network level, the local distribution network, for example, no corresponding data is available in Switzerland. The smart meters attached to the house connections relate to the individual electricity consumer and make network management only very limited at the present time. It will take some time before smart meters are used across the board.

In Switzerland, as an example, the different network levels are defined as follows:

CH 709 416 B1

a. Network level 1 (NE 1) - maximum voltage level:> 220 kV

b. Network levels 2, 4 and 6 (NE 2, 4 and 6) - transformation levels

c. Network level 3 (NE 3) - high voltage level:> 36 kV and <220 kV

d. Network level 5 (NE 5) - medium voltage level:> 1 kV and <36 kV

e. Network level 7 (NE 7) - low voltage level: 1 kV and lower

Low-voltage networks for the fine distribution of energy usually comprise several cable runs, which, starting from cable distribution booths, supply single and multi-family houses, typically groups of houses, as connection users in the vicinity.

In view of the problems mentioned, the question arises whether the smart meter method is actually the right one for data acquisition for monitoring, error analysis and optimization of the network management and network planning in the low-voltage range, in particular for the network level NE 7, or whether it should be limited to being a communication tool between the end consumer and the corresponding producer for billing and cost optimization.

For simple current measurement in the area of the distribution booths (NE 7), the only possibility so far is the use of so-called clamp-on ammeters. These measure the electrical current in an indirect way without having to open the circuit. To do this, the clamp ammeter is manually placed around the conductor or the busbar. In so-called all-current clamp ammeters, a magnetic field sensor is built into an air gap in the core part of the clamp. This sensor measures the magnetic effect of the conductor current. The weak signals are picked up after amplification and shown on the measured value display of the current measuring device.

However, such current clamps are limited to measurements on individual conductors. In the case of multi-core conductors, as is common in distribution cabins, and where there is at least one forward and return conductor, the opposite magnetic fields usually compensate, which results in a net current flow of zero. During maintenance in the typical case of power cables of protection class I (three-core cables), the cable sheath has to be stripped for a current measurement, so that every single wire can be made accessible, which is associated with corresponding effort.

The current clamp meters or current clamps mentioned in sections [0012] and [0013] have so far been used almost exclusively for maintenance purposes. They are only used for a short time until the necessary data have been determined. The pliers are then released from the relevant conductor and supplied until they are used again. A measuring device for permanent measurement in the form of such pliers does not yet exist. One of the challenges for such a measuring device is a practical arrangement in the distribution booth. The space in the cabins is modest and there are also no connection options to electronic devices for further processing of the measurement data.

The object of this invention is therefore to provide a method for non-contact and permanent measurement of currents in sheathed conductors, wherein the sheathing can include one or more insulated conductors. The aim of the method is to create a sensor-based planning instrument that covers the lowest voltage network levels, NE 6 and NE 7, and for this the data required for network analysis and efficient network operation, and in particular the data required for monitoring and error analysis, is available to the network operator provides to operate the networks more stable and homogeneous and thus to increase the security of supply for connection users.

For this purpose, it is a further object of the invention to provide a device for carrying out this method, namely a device for the permanent, contactless measurement of current strengths in sheathed conductors, wherein the sheathing can include one or more insulated conductors. The individual conductors can also be twisted and twisted in the sheathed conductor cable and / or arranged concentrically, as is typical for outer conductors. The device should be simple and easy to assemble. It should make it possible, without having to disconnect the cable harnesses to be measured, for the data to be sufficiently precise in order to be able to use the measuring method to indicate the current strengths determined and other relevant technical parameters. This data acquisition is to be carried out permanently, efficiently and with as little effort as possible using said device and the method operated with it. In addition, the simple construction of the device should make it possible to offer it at affordable prices.

The object is achieved by a method for the permanent, contactless measurement of current strengths in sheathed conductors, the sheath including one or more insulated conductors, and the method is characterized in that

a)

CH 709 416 B1, a sleeve is placed around the jacket, so that it surrounds the jacket with its internal conductors in a ring, and in which sleeve several magnetic field sensors are arranged and aligned around its circumference,

b) the magnetic fields generated by the current flowing in the enclosed, insulated conductors are measured by the magnetic field sensors and recorded as electronic data,

c) the empirically determined algorithms for the relationship between the current strengths in the individual conductors and the magnetic fields generated thereby, the effectively flowing current strengths in the individual conductors are calculated, as a data basis for the management of power distribution networks and forwarding to a server.

The object is further achieved by a device for the permanent, non-contact measurement of current strengths in coated conductors, the covering including a single or more insulated conductors, and the device being characterized in that it is designed as an openable sleeve with which the sheath can be enclosed, and in which sleeve several magnetic field sensors are arranged distributed over its circumference, on the basis of the magnetic fields determined by these magnetic field sensors, the effectively flowing current strengths in the individual conductors can be calculated, by empirically previously determined algorithms for the relationship between the current strengths in the individual conductors and the magnetic fields they generate.

Using the drawings, this device is described in more detail and its function, its use and the method that can be carried out with it are explained.

It shows:

Fig. 1: The device in the form of a sleeve acting as a sensor when applied to a sheathing with three conductors inside and concentric outer conductor;

2: The device is shown separately in the form of a sleeve acting as a sensor, slightly opened, with a transparent view of the magnetic field sensors arranged therein for better understanding;

3: Three current conductors to be measured are shown in cross section, surrounded by circularly arranged, schematically illustrated magnetic field sensors;

4: Four measurement images, each with three current conductors, generated with devices in which the magnetic field sensors are arranged differently;

Fig. 5: The device in the form of a sleeve acting as a sensor around a casing, in use;

Fig. 6: A distribution booth with an open door and an enlarged section of the cable entries into the distribution booth, with a cuff applied to a single jacket.

Fig. 1 shows the device in the form of a sleeve acting as a sensor. It consists of an annular, openable sleeve, with which a sheath 6 can be enclosed, which contains one or more conductors 7. In this figure, the sheath 6 contains both three phase conductors and a concentric outer conductor. The casing 6 can include a shield in the form of a copper braid. The annular sleeve shown here consists of two half-shells 1, 2 as fork fingers, which are connected to the fork root by a hinge 3 with an electrical connection 4. On the opposite side of the hinge 3, a cuff closure 5 is arranged, which releasably engages when the two half-shells 1, 2 are closed. For assembly, the cuff is placed around a sheath 6 in the open state as shown. The two fork fingers are spread apart. When these fork fingers have reached the end position, they enclose the casing 6 around their entire circumference in such a way that the sleeve is held securely on the casing 6 by the two half-shells 1, 2 coming to lie along the circumferential line of the casing 6. Instead of two half-shells 1, 2, such a measuring device or cuff can also consist of a single, elastic piece that is divided at one point, or of more than two cuff parts that can be moved relative to one another and which, in the closed state, comprise the casing 6 and can be plugged together for this purpose. As soon as the cuff closure 5 has engaged, the device can independently and permanently measure the current flows of the individual conductors 7 inside the sheath 6. The data from the measurement are fed via connection 4 on the cuff to a computer system (microcontroller), which carries out the evaluation and uses them to calculate the currents in the individual conductors. This computer system is coupled to a communication network by an intelligent communication device, as a result of which the data are read into the central server of a network operator company.

In order to understand the functioning of the current measurement for this device, the ring sleeve is shown in FIG. 2 with a partial interior view. The individual magnetic field sensors 8 and their respective central axes can be seen

CH 709 416 B1 are arranged along a circular line running centrally between the inner and outer fork edge. These are one-dimensional field sensors in the form of plates or platelets, which are used in conventional current measurement processes. They therefore have a front and a slightly smaller back plate. In the following, reference is always made to the front panel for its alignment. In the arrangement shown here, these magnetic field sensors 8 alternately assume one of two different orientations orthogonal to one another, their plate planes each enclosing an acute angle with the circumferential line. The magnetic field sensors are sensors that can measure a magnetic field in any way. Hall sensors or magnetoresistive sensors are just one example.

3 illustrates in a schematic representation, using a cross-sectional view, a further alternate arrangement of magnetic sensors 8, the ring sleeve surrounding it being hidden in this view. The three conductors 7 in the middle are surrounded by sixteen sensors 8, shown as polygons, the front plates of which are alternately oriented radially to the center of the sleeve and once orthogonally thereto. The black arrows point in the respective directions in which the one-dimensional sensors 8 mainly detect the magnetic field. All of these directionally complementary data provide an inventory of the magnetic fields across the entire cable cross-section. Accordingly, in the case of two-dimensional field sensors which are sensitive in two directions, an alternate alignment can be dispensed with.

In Fig. 4 different data images are shown, generated with different design options of the measuring device for one and the same cable configuration. Where the magnetic field lines are close together, black areas can be seen, corresponding to the measured values for the magnetic field strengths. It should be noted here that the intensely colored areas around the sensors 8, which represent positive values for the measured magnetic fields, have complementary areas, which are also colored black here, but correspondingly represent negative values for the magnetic fields. Negative values are to be interpreted in such a way that the respective digits are not relevant for the measurement. Only the areas with positive measured values (actual current flows) are recorded in the calculation. In the figure at the top right, for example, the antenna characteristic can be seen in a setup with sixteen one-dimensional magnetic fields sensors 8 that are optimally aligned for this conductor configuration, alternately with a positive and negative 45 ° angle to the radial. In relation to a compass rose placed over the illustration, the black areas between 260 ° and 015 ° have positive magnetic field values, while in the rest of the compass area the black areas represent negative magnetic field values throughout. In a colored image, the plus / minus values can be made distinguishable with different colors. A very similar picture, namely the one on the top left, results if instead only half as many, i.e. 8 sensors are arranged at twice the distance, but each form a cross profile and can therefore detect in two dimensions. Accordingly, the measurement image of a setup with mutually orthogonally aligned sensors at N positions can always be compared with that measurement image of a setup with two-dimensional sensors at N / 2 positions. As a further comparison, the measured value results for two slightly changed sensor arrangements are shown in the figures below left and right. In the case of 16 one-dimensional sensors with a completely radial alignment of a vertical on the sensor front panels, the measurement image is obtained at the bottom left and in the case of a tangential alignment of the vertical system on the sensor front panels, the measurement image is obtained at the bottom right.

The optimal arrangement of the magnetic field sensors 8 within the sleeve half-shells 1, 2 is dependent on the respective position of the conductor 7 within the sheathing 6. Thus, different arrangements of the sensors 8 with orientations in any direction are possible. The orientations of the sensors 8 can be adjusted along any axes. If the current conductor 7 is in a known position, for example in the case of guided conductor rails, it can therefore be measured with a fixed arrangement of sensors 8. If the position of the conductors 7 is assumed, the optimal sensor arrangement can be determined empirically from the determined data. The arrangement of the magnetic field sensors 8 can be adjusted in two ways: both the positioning of the sensors 8 along the circumferential line of the sleeve half-shells 1, 2 and the angle between the perpendicular to the plates and the tangent to the circumferential line of the fork fingers at the specific sensor position is adjustable. Due to the different arrangements and orientations of the sensors 8, different measured values are recorded and finally combined by a computer system, which can act as a microcontroller, to form a holistic picture.

A possible arrangement of the magnetic field sensors 8 on the circumferential line of the cuff can thus be chosen so that for certain plates a vertical on the respective front plate shows radially to the center of the ring formed by the cuff, and some magnetic field sensors on a circumferential line of the cuff are aligned so that a vertical line on the front plate forms an acute angle with the circumferential line of the cuff.

In a further variant, the arrangement can be chosen so that the plates of the magnetic field sensors 8 are alternately arranged on a circumferential line of the cuff in the circumferential direction so that a vertical on the front plate with the circumferential line of the cuff against the cuff center towards an acute angle includes, and the front plate of the next magnetic field sensor 8 is aligned on the circumferential line of the cuff such that a vertical on the front plate with the circumferential line of the cuff directed away from the cuff includes an acute angle, etc.

In any case, the data of all magnetic field sensors 8 are fed to a computer system which undertakes the evaluation of the data and calculates the currents in the individual conductors 7 therefrom.

CH 709 416 B1 FIG. 5 shows the device with its magnetic field sensors 8 in use, shown using the example of a sheath 6 with four conductors 7 inside, namely three phase conductors and a concentric outer conductor. The three phase conductors 7 are individually insulated and additionally insulated from the concentric outer conductor. The current measurement in the respective conductors 7 is carried out by the magnetic field sensors 8 located in the two sleeve half-shells 1, 2. Once the sleeve has been attached in this way, it no longer needs to be shifted, except for maintenance purposes on the sleeve itself. The magnetic field strengths permanently measured by the magnetic field sensors 8 and transmitted to the computer system, which determines the relevant current strengths in the individual conductors 7. Thus, this current sensor works largely independently.

The mode of operation, according to which the current is ultimately measured with this device, follows the Ampère's law of through-flow: If a current flows through a conductor, this causes a magnetic field, which correlates uniquely with the current in the conductor. If the resulting magnetic field is measured at a sufficient number of positions in the case of several conductors, the currents and positions of the conductors required for this can be clearly determined. By making assumptions about the possible conductor positions, the number of necessary measuring points is reduced to a practical number. Appropriate positioning of magnetic field sensors makes it possible to minimize the system's susceptibility to interference from external interference currents. The data determined empirically in this way provide the measured values M, which on the other hand can be calculated using a linearized model from the (unknown) effective currents I and the matrix W representing the geometry of the configuration. For this reason, an algorithm for the current calculation creates an approach for the matrix W and simulates a current flow in order to compare the values obtained in this way with the actual measurement. In order to minimize the error between fictitious and real measurement values, the parameters of the approach matrix are changed step by step so that the error assumes its global minimum through an iteration process. Assuming that the positions of the individual conductors do not change any further compared to the measuring device, the global minimum of error corresponds to the configuration with the real conductor positions, as a result of which the currents can be clearly calculated.

Fig. 6 shows a distribution cabin 9 with the front door open. The section surrounded by the dashed frame is shown in an enlargement. In the lower part you can see the undamaged casing 6 and the sensor device with its two half-shells 1, 2 and in the upper part the individual conductors 7 separated for assembly. The current sensor is shown in use, i.e. with connection cable 10 to the communication device. Overall, therefore, only a few such devices with magnetic field sensors 8 are required in their interior in order to obtain the status information of the entire distribution cabin 9 and thus of the end user groups connected to it.

Thanks to the data obtained in this way, network operation can take place directly on the basis thereof. All measured values can be obtained from a distribution cabin 9, whereupon they are evaluated in a microcontroller and fed into a central server for further processing via remote communication. This offers electricity providers a tool for network planning in the low-voltage range. The reliable data transmission on the low-voltage level between the main distribution area and the end user then serves firstly to optimize the network operation and secondly to expand the network as required with optimized investment costs.

On the basis of the data determined and made available, the network management in the low-voltage range can develop efficient maintenance concepts with optimized maintenance costs. Such Reliability Centered Maintenance is based on failure-based, interval-based or periodic to condition-based maintenance strategies.

Numerical index [0033]

First half-shell of the cuff

Second half-shell of the cuff

Hinge of the cuff

Electrical connection of the cuff

cuff closure

jacket

ladder

magnetic field sensor

Verteilkabine

connection cable

CH 709 416 B1

Claims (11)

claims 1. A method for the permanent, non-contact measurement of currents in sheathed conductors (7), the sheath (6) including one or more insulated conductors (7), characterized in that a) a sleeve is placed around the jacket (6), so that it surrounds the jacket (6) with its conductors (7) in a ring, and in which sleeve several magnetic field sensors (8) are arranged and aligned around their circumference, b) the magnetic fields generated by the current flowing in the enclosed, insulated conductors (7) are measured by the magnetic field sensors (8) and recorded as electronic data, c) the empirically determined algorithms for the relationship between the currents in the individual conductors (7) and the magnetic fields generated thereby, the effectively flowing currents in the individual conductors (7) are calculated as a data basis for the management of power distribution networks and forwarding a server. 2. Device for the permanent, contactless measurement of current strengths in sheathed conductors (7), the sheath (6) including a single or more insulated conductors (7), characterized in that it is designed as an openable sleeve with which the sheath ( 6) can be enclosed, and in which sleeve several magnetic field sensors (8) are arranged in the form of plates distributed over their circumference, on the basis of the magnetic fields determined by these magnetic field sensors (8) the effectively flowing current strengths in the individual conductors (7) can be calculated, using algorithms previously determined empirically for the relationship between the current strengths in the individual conductors (7) and the magnetic fields generated thereby. 3. Device for the permanent, contactless measurement of currents in coated conductors (7) according to claim 2, characterized in that the magnetic field sensors (8) are arranged rigidly distributed relative to the circumference of the sleeve. 4. Device for the permanent, non-contact measurement of current strengths in coated conductors (7) according to claim 2, characterized in that the magnetic field sensors (8) are arranged displaceably along the circumference of the sleeve in the same. 5. A device for the permanent, contactless measurement of current strengths in coated conductors (7) according to one of claims 2 to 4, characterized in that the magnetic field sensors (8) are arranged along the circumference of the sleeve in different orientations and adjustable about any axis. 6. Device for the permanent, contactless measurement of currents in coated conductors (7) according to one of claims 2 to 4, characterized in that the plates of the magnetic field sensors (8) are arranged alternately on a circumferential line of the sleeve in the circumferential direction so that a perpendicular on a plate with the tangent to the circumferential line of the sleeve at the point where the plate is arranged, and the plate of the next magnetic field sensor (8) on the circumferential line of the sleeve is aligned so that a perpendicular to the plate to the tangent the circumferential line of the cuff is orthogonal at the location where the plate is located. 7. Device for the permanent non-contact measurement of currents in coated conductors (7) according to one of claims 2 to 4, characterized in that some plates of the magnetic field sensors (8) are aligned on a circumferential line of the sleeve so that a perpendicular to these plates radially point to the center of the ring formed by the cuff, and some plates of the magnetic field sensors (8) are aligned on a circumferential line of the cuff so that a perpendicular to these plates with the tangent to the circumferential line of the cuff at the location where the plates are arranged , includes an acute angle. 8. Device for the permanent non-contact measurement of current strengths in coated conductors (7) according to one of claims 2 to 4, characterized in that the plates of the magnetic field sensors (8) are arranged alternately on a circumferential line of the sleeve in the circumferential direction so that a perpendicular a plate with the tangent to the circumferential line of the cuff at the point where the plate is arranged forms an acute angle towards the cuff center, and the plate of the next magnetic field sensor (8) is aligned on the circumferential line of the cuff in such a way that a perpendicular on this plate with the tangent to the circumferential line of the cuff at the point where the plate is arranged, away from the cuff, forms an acute angle. 9. Device for the permanent, contactless measurement of current strengths in coated conductors (7) according to one of claims 2 to 8, characterized in that it is designed as an annular sleeve with two half-shells (1, 2) which is arranged around a hinge (3) can be swung open and is thus evident, and which can be closed in the open state around a sheath (6) with one or more conductors (7) guided therein, so that it surrounds this or these conductors (7) in a ring. 10. The device for the permanent, contactless measurement of currents in coated conductors (7) according to one of claims 2 to 8, characterized in that it is designed as an annular sleeve, which is made of an elastic material and is severed at one point, and which can be expanded by expanding the severing and is thus evident, and can be closed in the open state by a sheath (6) with one or more conductors (7) therein, so that it surrounds this or these conductors (7) in a ring. CH 709 416 B1 11. The device for permanent, non-contact measurement of currents in coated conductors (7) according to one of claims 2 to 8, characterized in that it is designed as an annular sleeve which can be plugged together from two or more parts to form a ring, and which in Open or separated state around a sheath (6) with one or more conductors (7) can be closed therein, so that it surrounds this or these conductors (7) in a ring. CH 709 416 B1 CH 709 416 B1