WO2024197374A1

WO2024197374A1 - Method for monitoring distribution transformer output energy

Info

Publication number: WO2024197374A1
Application number: PCT/BR2024/050124
Authority: WO
Inventors: Eduardo BREGANT; Douglas PROSTT
Original assignee: Landis and Gyr Equipamentos de Medicao Ltda
Current assignee: Landis and Gyr Equipamentos de Medicao Ltda
Priority date: 2023-03-29
Filing date: 2024-03-27
Publication date: 2024-10-03
Anticipated expiration: 2025-09-29

Abstract

A system comprising: a distribution transformer (DT) capable of providing one or more output voltages, the DT comprising a respective DT output line for each output voltage; one or more transducers, each transducer comprising a set of transducer primary coils and a set of transducer secondary coils, each set of transducer secondary coils comprising a respective first transducer output cable and a respective second transducer output cable; an electric metering system comprising: one or more meter service drop outputs; and at least one additional electrical connection point; wherein: each DT output line is coupled to a respective one of the sets of transducer primary coils; the first transducer output cable of each set of transducer secondary coils is connected to one of the one or more meter service drop outputs; and the second transducer output cable of each set of transducer secondary coils is connected to one of the at least one additional electrical connection point; such that the electric metering system monitors one or more energy outputs of the DT.

Description

Method for monitoring Distribution Transformer output energy

FIELD OF THE INVENTION

The disclosure relates to the monitoring of non-technical losses in energy distribution.

BACKGROUND TO THE INVENTION

In energy distribution, “non-technical losses’’ refers to energy that is produced and consumed, but is not billed. This may, for example, be due to meter read errors or unmetered supplies, but may also be due to energy theft. Energy theft generally involves either tampering with electrical meters, or tapping into unmetered portions of an energy distribution network.

Energy is generally conveyed from power generation sites via high-voltage cables, distributed via medium-voltage distribution cables up to areas of consumption, and then converted to lower voltages by distribution transformers (DTs) for distribution to consumer locations including private homes. The medium voltages (MV) of power lines generally prohibit energy theft, as the party stealing power would require specialist equipment such as their own DT. As a result, illegal tapping of energy distribution networks usually occurs after the DT but before the first electric meter, where the line is low voltage but unmonitored.

A known means of combating such theft is the use of a DT meter (DTM). A DTM is an energy meter fitted directly after the DT that meters the entire energy output of the DT. Given the high operating electric currents of DTs output, a DTM is generally a sophisticated and expensive industrial meter capable of measuring very high currents. Since industrial energy meters are generally sensitive to e.g. dust and environmental conditions, the DTM is generally provided with a protective enclosure separate and external to any protective enclosure provided around the DT. Information recorded by DTMs is not generally used for any billing process, but may rather be used to compare the total output of the DT to the total billed by end users to detect any discrepancy caused by non-technical losses. Fig. 1 shows a typical arrangement wherein a DT 106 is positioned near the top of a pole 100 which serves to support medium-voltage transmission lines 102. A medium-voltage line 104 runs from the transmission lines 102 to the DT 106. The DT converts down to a lower voltage for the subsequent line 108. A DTM is affixed to the pole 100 as close to the DT 106 as possible, so that the length of low-voltage, unmetered line 108 between the DT and the DTM is as short as possible. This is because any tapping of the line 108 by an energy thief would go undetected. Given the inaccessible location of the DTM 110, the DTM 110 may comprise a communications module 112 (such as a radio antenna) to communicate metering information back to the DTM operator.

Another known means of combating energy theft is Cabinet Metering Systems (CMS). In this scheme, electric meters corresponding to particular end users are also placed on top of poles so as to be out of easy reach of anyone wishing to tamper with the meters. The CMS meters corresponding to a particular DT may be at the top of the same pole as the DT, or may be atop separate poles with cables running in between from the DT to the CMS meters. In this manner, all power lines that extend down into private homes are already metered by the CMS. Each CMS meter can be merely a residential meter, without any need for an industrial meter, as each CMS meter meters only the portion of the DT output directed towards a particular user. CMS meters do not, and generally cannot, monitor the entire DT output as a DTM does. As a result, CMS meters do not detect energy theft directly, but instead act to prevent energy theft by making meters more difficult to tamper with and lines more difficult to tap.

An exemplary CMS scheme 200 is shown in Fig. 2, where the pole 100 supports a DT 106 and a CMS, the CMS containing residential meters 204a, 204b, 204c. It is noted that there may be further CMSs corresponding to the DT 106; Fig. 2 shows only a single CMS for simplicity. A medium-voltage line 104 runs from a transmission line to the DT 106, which converts down to a low-voltage line 108. The line 108 connects to each of the residential meters 204a, 204b, 204c, each of which has a respective output 206a, 206b, 206c that runs to a respective end user, e.g. a private residence. Any or all of the residential meters 204a, 204b, 204c may further comprise a communications module 208 (such as a radio antenna) for communicating metering information to end users and/or the operator of the metering system. Alternatively, the CMS may further comprise a controller 210, also referred to herein as a meter concentrator 210, which collects information from all three meters 204a, 204b, 204c and passes the information to the communications module 208 for transmission. SUMMARY OF THE INVENTION

The inventors have recognised that there is a need for a means of detecting nontechnical losses that does not require an expensive external DTM (which may, for example, have to be an industrial meter). They have additionally recognised the practical difficulties of installing a DTM, such as the need for an additional secure enclosure and potential differences in communication protocols between the DTM and an existing CMS meter.

Embodiments of the present disclosure provide a means of adapting an existing CMS meter to function effectively as a DTM and monitor the entire energy output of a DT, without requiring the use of a separate DTM. The cabinet already present around the CMS meter avoids the need to fit a further cabinet, and any communication apparatus of the CMS meter can be used to communicate data regarding the DT, avoiding any differing protocols.

According to one aspect of the present disclosure there is provided a system comprising: a distribution transformer (DT) capable of providing one or more output voltages, the DT comprising a respective DT output line for each output voltage; one or more transducers, each transducer comprising a set of transducer primary coils and a set of transducer secondary coils, each set of transducer secondary coils comprising a respective first transducer output cable and a respective second transducer output cable; an electric metering system comprising: one or more meter service drop outputs; and at least one additional electrical connection point; wherein: each DT output line is coupled to a respective one of the sets of transducer primary coils; the first transducer output cable of each set of transducer secondary coils is connected to one of the one or more meter service drop outputs; and the second transducer output cable of each set of transducer secondary coils is connected to one of the at least one additional electrical connection point; such that the electric metering system monitors one or more energy outputs of the DT.

This has the advantage that the output of the DT can be monitored using only existing residential meters, with only a few new connections and the addition of a transducer. The expense and expertise required to fit a separate DTM are thus avoided. The at least one additional electrical connection point may be a common electrical connection point for the electric metering system.

Each of the at least one additional electrical connection point may be a busbar.

The system may be a three-phase electrical system in which: the DT comprises three DT output lines, one for each phase; the system comprises three transducers; the electric metering system comprises three busbars and three meter service drop outputs, each meter service drop output associated with a corresponding one of the busbars; and each first transducer output cable is connected to one of the meter service drop output, with the respective second transducer output cable being connected to the corresponding busbar.

The system may be a two-phase electrical system in which: the DT comprises two DT output lines, one for each phase; the system comprises two transducers; the electric metering system comprises two busbars and two meter service drop outputs; and each first transducer output cable is connected to one of the meter service drop outputs, with the respective second transducer output cable being connected to the corresponding busbar.

The system may be a single-phase electrical system in which: the DT comprises only one DT output line; and the system comprises only one transducer .

The electric metering system may comprise a residential meter.

This has the advantage that residential meters are generally cheaper than external (for example, industrial) DTM meters. Additionally, in areas where CMS schemes are in use, residential meters may already be installed in CMSs in close proximity to DTs.

The electric metering system may be surrounded by an enclosure that provides mechanical protection.

This has the advantage that the invention is protected by an enclosure that is already present for the protection of the residential meters. There is no need to, for example, fit a separate external enclosure to protect a new DTM. The electric metering system may be a Cabinet Meter System.

This has the advantage that, where CMS meters are already in use, metering of the DT can be implemented with minimal modifications and no need for a new dedicated DTM.

The system may further comprise an alarm that activates when a door of the enclosure is opened, activation of the alarm resulting in at least one of an audible sound and halting a supply of energy to end users.

This has the advantage that anyone tampering with the meter will be detected as a result of the alarm noise, and/or thwarted by the halting of the power supply.

Other meter service drop outputs of the electric metering system may be used to monitor energy and/or power consumption of end users.

This has the advantage that a residential meter already provided and in use for monitoring the power consumption of end users may be used to meter the output of a DT with minimal modification and no need to provide a separate dedicated DTM.

The electric metering system may further comprise a communications module operable to transmit information regarding said power consumption of end users, wherein the communications module is further used to transmit data regarding the output energy of the DT or any other electrical information associated therewith.

This has the advantage that a communications module already in use to transmit information regarding end user power consumption may further be used for DT metering. This is much simpler than providing a separate antenna as part of a newly added DTM, and avoids any issues with e.g. differing communication protocols for each antenna.

The DT may receive at least one input voltage from a transmission line.

Each transducer may comprise a current transformer.

According to a further aspect of the present disclosure there is provided a method comprising: providing one or more transducers, each transducer comprising a set of transducer primary coils and a set of transducer secondary coils, each set of secondary coils comprising a respective first transducer output cable and a respective second transducer output cable; coupling each set of primary coils to a respective distribution transformer (DT) output line of a DT; providing an electric metering system comprising: one or more meter service drop outputs; and at least one additional electrical connection point; connecting the first transducer output cable of each set of transducer secondary coils to one of the meter service drop outputs; and connecting the second transducer output cable of each set of transducer secondary coils to the at least one additional electrical connection point; such that the electric metering system monitors one or more energy outputs of the DT.

These and other aspects will be apparent from the embodiments described in the following. The scope of the present disclosure is not intended to be limited by this summary nor to implementations that necessarily solve any or all of the disadvantages noted.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present disclosure and to show how embodiments may be put into effect, reference is made to the accompanying drawings in which:

Fig. 1 shows a prior art system with a distribution transformer (DT) and a DT meter affixed near the top of a pole supporting high-voltage transmission lines;

Fig. 2 shows a prior art cabinet metering system;

Fig. 3 shows an electric meter connected according to an embodiment of the disclosure in a single-phase system;

Fig. 4 shows a 3-phase implementation of the system of Fig. 3; and

Fig. 5 shows an alternative 3-phase implementation of the system of Fig. 3.

DETAILED DESCRIPTION

Embodiments will now be described by way of example only.

It is noted that the term “residential meter” is used herein to mean, generally speaking, a meter designed to accept the full current of a metered power line passing through the body of the meter. Such meters are generally used for relatively low-current and low- voltage applications such as residential homes, but the term “residential” is used merely to identify this type of meter, not to refer specifically to meters used for such homes. Typically meters of this type may be used up to currents of at most, very broadly speaking, 150-200 A, provided that the accompanying voltage is not too high. The term “residential meter” is also intended to encompass such meters that have been somehow modified, such as by alterations to gains or filters within the meter.

The contrasting term “industrial meter” is generally used herein to refer to a CT-rated meter wherein a current transformer is sampled via a probe so that only a greatly reduced current passes through the meter itself. For example, such a meter may meter a 500 A current by reducing it to a 5 A current. Such meters are typically more expensive and specialised than residential meters, and generally require more sophisticated computing infrastructure for their operation.

Fig. 3 shows an arrangement of a DT 106 and an electric metering system 304, for example in a CMS arrangement, adapted according to an embodiment of the present invention. To allow for a simple illustrative example, Fig. 3 depicts a single-phase implementation. A more complex 3-phase implementation will be described below with regard to Fig. 4.

It is noted that the electric metering system need not be part of a CMS scheme. Generally speaking, any electric metering system associated with the DT 106 may be used to implement the disclosure.

As in Fig. 2, the DT 106 generally receives a medium-voltage input 104, for example from a transmission line. This is converted down to a lower output voltage on a line 108. This line 108 is then connected to a transducer 308 (for example, a current transformer) having primary coils 310 and secondary coils 312. The line 108 connects to the primary coils 310, and is down-converted to a lower current in the secondary coils 312. The secondary coils have two outputs, a live output 314 and a neutral output 316 (also referred to herein as a first output 316 and a second output 314).

Also shown in Fig. 3 is an electric metering system 304, typically a residential metering system. The metering system 304 has electric meters (otherwise referred to herein as meter modules) 304a, 304b, 304c. While three modules are shown in Fig. 3, it will be appreciated that the metering system 304 may have as few as 1 module, or may have more than 3 modules. For example, it is common for CMSs to have 12 modules.

It is noted that, in some CMS schemes, there may be multiple CMSs provided for a single DT 106. For example, it may be that one or more CMSs are atop the same pole 100 as the DT 106, and one or more other CMSs are atop other poles. Cables will generally then run between the poles to connect the DT 106 to each CMS. In such cases, it is envisioned that the system of Fig. 3 need only be implemented in one of the CMSs associated with a given DT 106. This will most likely be one of the CMSs atop the same pole 100 as the DT 106, but need not necessarily be.

Each module has at least one respective meter service drop output 306a, 306b, 306c through which energy from the busbar is supplied to the energy consumer. While the meter modules 304a, 304b, and 304c shown in Fig. 3 each have one service drop output, it is noted that meter modules may have more than one such output. For example, it is common for a single meter module to have one, two, or three service drop outputs. (An example is discussed below with regard to Fig. 5.)

Furthermore, the metering system 304 generally has at least one additional electrical connection point. In Fig. 3 this is shown as a busbar 302. However, the connection point may take the form of, for example, a common electrical connection point for all the meter modules 304a, 304b, 304c.

Typically each meter module 304a, 304b, 304c meters the supply to a different end user. However, it is usual that there are some spare module slots of meter modules to provide for increased usage and new connections in the future. One of these spare modules (e.g. 304a in Fig. 3) may be connected as described below in order to monitor the power output of the DT 106.

The current output of the DT 106 is generally too large to be passed directly through the metering system 304; doing so would likely render the metering system 304 unable to function. The lower current from the outputs 314, 316 of the secondary coils 312 is therefore provided instead to the spare meter module 304a. The first output 314 is connected to the additional electrical connection point (in Fig. 3 this is the busbar 302) while the second output 316 is connected to the service drop output 306a of the spare meter module 304a. The spare meter module 304a thereby meters the output of the DT 106, with current reduced by the transducer 308 to avoid damage to the metering system 304. Based on the Superposition Theorem, the spare meter module 304a measures only the current generated by the secondary coils 312.

As shown in Fig. 3, the CMS may be equipped with a communications module 208, which may include, for example, a radio antenna. In this regard, there may be a scheme wherein the metering system 304 stores readings in one or more local registers, which are then collected by a controller 210 (also referred to herein as a meter concentrator 210) for transmission via the communications module 208. If this is the case, there may be one local register per meter module 304a, 304b, and 304c, or there may be a single local register for use by all the modules. It is noted that, in this manner, data gathered from metering the DT 106 may be transmitted alongside, and using the same communications protocols as, data collected from metering end users via other meter modules.

As shown in Fig. 3, the electric metering system 304 may be protected by an enclosure 202 similar to the one shown in Fig. 2, to prevent unauthorised access and offer protection from the elements. The enclosure 202 may be a pre-existing enclosure provided as part of a CMS scheme.

It is noted that the transducer 308 shown in Fig. 3 has only two output cables, 314 and 316. Occasionally transducers used in metering may have a third output that provides a reference voltage sampled from an electrical contact the passing through the insulation of the cable 108. In implementations of the present disclosure this third connection is generally unnecessary, as the connection to the metering system 304 already provides a reference voltage. A transducer can therefore generally be used that does not feature a reference output.

Fig. 4 shows a further implementation of the disclosure in a 3-phase system. Several features of Fig. 4 correspond to features of Fig. 3 and are as described above. In a 3- phase system, the DT 106 may generally provide 3 output voltages, each on a respective line 408a, 408b, 408c. Each of these lines may then be coupled to a separate transducer, each transducer having a set of primary coils 410a, 410b, 410c and a set of secondary coils 412a, 412b, 412c. Each set of secondary coils 412a, 412b, 412c may then have a corresponding first output cable 414a, 414b, 414c and second output cable 416a, 416b, 416c, so that each phase may be carried on a separate pair of output cables. The output cables 414a, 414b, 414c, 416a, 416b, 416c then connect to a metering system 404.

The disclosure may be implemented in a 3-phase system using 3 single-phase meter modules 404a, 404b, 404c, each having a single meter service drop output 406a, 406b, 406c. As it is still envisioned that the metering system 404 will also generally be in use for metering end user supplies, the metering system 404 in Fig. 3 is shown with 5 modules, merely for illustrative purposes. In this example, the additional modules 406d and 406e (and any further additional modules beyond those shown) may be used to provide metering for end users.

In a 3-phase system, the metering system 404 may further comprise 3 busbars 402a, 402b, 402c rather than the single busbar of Fig. 3. The 3 busbars 402a, 402b, 402c each correspond to one of the meter service drop outputs 406a, 406b, 406c. Each of the 3 live outputs 414a, 414b, 414c may then be connected to a respective busbar 402a, 402b, 402c, with each of the 3 neutral outputs 416a, 416b, 416c being connected to a respective service drop output 406a, 406b, 406c. For example, neutral cable 414a may connect to busbar 402a, and the corresponding live cable 416a may connect to the meter service drop output 406a that corresponds to busbar 402a. The result is again the monitoring of the entire output of the DT 106 using a metering system 404 which may comprise residential rather than industrial meters.

Fig. 5 shows a 3-phase implementation of the disclosure similar to that shown in Fig. 4. However, in this implementation DT metering is implemented using a monolithic 3-phase meter module 504a. The 3-phase module 504a comprises three meter service drop outputs 406a, 406b, 406c, and plays an equivalent role to the three single-phase modules 404a, 404b, and 404c shown in Fig. 4.

In a 3-phase system, either the scheme of Fig. 4 or the scheme of Fig. 5 may be implemented depending on what meter modules are available and/or what is already present in an existing CMS. It is generally envisioned that either scheme is equally suitable for implementing the disclosure.

Thus, it can be seen that embodiments described herein provide a means of using a residential meter to monitor the output of a DT to detect non-technical losses, without the need to provide a dedicated industrial DTM. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1 . A system comprising: a distribution transformer (DT) capable of providing one or more output voltages, the DT comprising a respective DT output line for each output voltage; one or more transducers, each transducer comprising a set of transducer primary coils and a set of transducer secondary coils, each set of transducer secondary coils comprising a respective first transducer output cable and a respective second transducer output cable; an electric metering system comprising: one or more meter service drop outputs; and at least one additional electrical connection point; wherein: each DT output line is coupled to a respective one of the sets of transducer primary coils; the first transducer output cable of each set of transducer secondary coils is connected to one of the one or more meter service drop outputs; and the second transducer output cable of each set of transducer secondary coils is connected to one of the at least one additional electrical connection point; such that the electric metering system monitors one or more energy outputs of the DT.

2. The system of claim 1 , wherein the at least one additional electrical connection point is a common electrical connection point for the electric metering system.

3. The system of claim 1 , wherein each of the at least one additional electrical connection point is a busbar.

4. The system of claim 1 , wherein the system is a three-phase electrical system in which: the DT comprises three DT output lines, one for each phase; the system comprises three transducers; the electric metering system comprises three busbars and three meter service drop outputs, each meter service drop output associated with a corresponding one of the busbars; and each first transducer output cable is connected to one of the meter service drop output, with the respective second transducer output cable being connected to the corresponding busbar.

5. The system of claim 1 , wherein the system is a two-phase electrical system in which: the DT comprises two DT output lines, one for each phase; the system comprises two transducers; the electric metering system comprises two busbars and two meter service drop outputs; and each first transducer output cable is connected to one of the meter service drop outputs, with the respective second transducer output cable being connected to the corresponding busbar.

6. The system of claim 1 , wherein the system is a single-phase electrical system in which: the DT comprises only one DT output line; and the system comprises only one transducer.

7. The system of any preceding claim, wherein the electric metering system comprises a residential meter.

8. The system of any preceding claim, wherein the electric metering system is surrounded by an enclosure that provides mechanical protection.

9. The system of claim 8, wherein the electric metering system is a Cabinet Meter System.

10. The system of claim 8 or 9, further comprising an alarm that activates when a door of the enclosure is opened, activation of the alarm resulting in at least one of an audible sound and halting of a supply of energy to end users.

11 . The system of any preceding claim, wherein other meter service drop outputs of the electric metering system are used to monitor energy consumption of end users.

12. The system of claim 11 , wherein the electric metering system further comprises a communications module operable to transmit information regarding said power consumption of end users, wherein the communications module is further used to transmit data regarding the output energy of the DT or any other electrical information associated therewith.

13. The system of any preceding claim, wherein the DT receives at least one input voltage from a transmission line.

14. The system of any preceding claim, wherein each transducer comprises a current transformer.

15. A method comprising: providing one or more transducers, each transducer comprising a set of transducer primary coils and a set of transducer secondary coils, each set of secondary coils comprising a respective first transducer output cable and a respective second transducer output cable; coupling each set of primary coils to a respective distribution transformer (DT) output line of a DT; providing an electric metering system comprising: one or more meter service drop outputs; and at least one additional electrical connection point; connecting the first transducer output cable of each set of transducer secondary coils to one of the meter service drop outputs; and connecting the second transducer output cable of each set of transducer secondary coils to the at least one additional electrical connection point; such that the electric metering system monitors one or more energy outputs of the DT.