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EP-4242670-B1 - APPARATUS AND METHOD FOR MEASURING ACTIVE ELECTRIC POWER IN AN ELECTRIC CIRCUIT

EP4242670B1EP 4242670 B1EP4242670 B1EP 4242670B1EP-4242670-B1

Inventors

  • ZAWADZKI, ARTUR
  • Molinski, Grzegorz
  • Ryba, Piotr

Dates

Publication Date
20260506
Application Date
20220308

Claims (15)

  1. A measuring apparatus (1) for measuring active electric power in an electric circuit (100), said measuring apparatus comprising: - a first measuring unit (10) operatively coupled to a first measurement point (101) of said electric circuit, said first measuring unit being configured to acquire first detection values ( v(t)) related to one or more voltages at the first measurement point (101) of said electric circuit; - a plurality of second measuring units (20) operatively coupled to a plurality of second measurement points (102) of said electric circuit, each second measuring unit being configured to acquire second detection values ( i(t)) related to one or more currents at a corresponding second measurement point (102) of said electric circuit; wherein said first measuring unit (10) and said second measuring units (20) are capable of communicating one with another, wherein said first measuring unit (10) is configured to transmit in a cyclical manner, with a predefined broadcasting frequency and during subsequent measurement intervals, broadcast messages (M B ) to said second measuring units (20), each broadcast message (M B ) including first detection values ( v(t)) acquired by said first measuring unit (10), wherein each second measuring unit (20) is configured to receive, during each measurement interval (T J ), a broadcast message (M B,J ) transmitted by said first measuring unit (10) and including first detection values ( v(t)) acquired by said first measuring unit (10) at an acquisition instant (t K ) preceding said measurement interval (T J ), wherein each second measuring unit (20) is configured to calculate, during said measurement interval (T J ), in response to receiving said broadcast message (M B,J ), third detection values (P (t)) indicative of the active electric power flowing through a corresponding second measurement point (102) of said electric circuit, characterised in that each second measuring unit (20) is configured to calculate said third detection values (P(t)) at a calculation instant (tc) included in said measurement interval (T J ) and delayed of a predefined latency time (T L ) relative to the acquisition instant (t K ) of the first detection values ( v(t)) included in the received broadcast message (M B,J ), wherein each second measuring unit (20) is configured to calculate said third detection values ( P(t)) based on first detection values ( v(t) ) received by said second measuring unit (20) up to said calculation instant (tc) and based on second detection values (i(t)) acquired by said second measuring unit (20) up to the acquisition instant (t K ) of the first detection values ( v(t) ) included in the received broadcast message (M B,J ), wherein each second measuring unit (20) is configured to calculate the acquisition instant (t K ) of the first detection values ( v(t) ) included in the received broadcast message (M B,J ) based on said calculation instant (tc) and said latency time (T L ).
  2. Measuring apparatus, according to claim 1, characterised in that said predefined latency time (T L ) has a constant and equal duration for all the second measuring units (20).
  3. Measuring apparatus, according to claim 2, characterised in that said predefined latency time (T L ) is an integer multiple of the duration time (T D ) of each measurement interval.
  4. Measuring apparatus, according to one of the previous claims, characterised in that each second detection unit (20) is configured to acquire additional detection values ( S(t) ) related to one or more additional physical quantities at a corresponding second measurement point (102) of said electric circuit.
  5. Measuring apparatus, according to one of the previous claims, characterised in that each broadcast message (M B ) includes an address value (A) addressing a second measuring unit (20), from which a response message (M R ) is desired.
  6. Measuring apparatus, according to claim 5, characterised in that each second measuring unit (20) is configured to transmit, during said measurement interval (T J ), in response to receiving said broadcast message (M B.J ), a response message (M R, J ) to said first measuring unit (10), if said measuring unit is addressed by the address value (A) included in the received broadcast message (M B,J ), said response message (M R, J ) including one or more detection values ( P(t), i(t), S(t)) calculated or detected by said second measuring unit (20).
  7. Measuring apparatus, according to one of the previous claims, characterised in that said first measuring unit (10) comprises: - a metering module (11) configured to sense one or more voltages at the first measurement point (101) of said electric circuit; - a broadcasting module (12) configured to transmit said broadcast messages (M B ) to said second measuring units (20); - a control module (13) configured to control the operation of said metering module (11) and said broadcasting module (12) wherein said metering module (11) is configured to acquire said first detection values ( v(t) ) and transmit said first detection values to said broadcasting module (12), wherein said broadcasting module (12) is configured to encode, during each measurement interval, said first detection values ( v(t) ) in a broadcast message (M B ) and transmit said broadcast message to said second measuring units (20).
  8. Measuring apparatus, according to claim 7, characterised in that said broadcasting module (12) is configured to decode, during each measurement interval, the detection values ( P(t), i(t), S(t)) included in a response message (M R ) received from a second measuring unit (20) and transmit said detection values to said control module (13).
  9. An electric power distribution system (500) including an electric circuit (100) and a measuring apparatus (1), according to one of the previous claims.
  10. A method for measuring active electric power in an electric circuit (100) comprising: - acquiring first detection values ( v(t) ) related to one or more voltages at a first measurement point (101) of said electric circuit; - acquiring second detection values ( i(t) ) related to one or more currents at a plurality of second measurement points (102) of said electric circuit; wherein said measuring method comprises the following steps: - at said first measurement point (101), transmitting in a cyclical manner, with a predefined broadcasting frequency and during subsequent measurement intervals, broadcast messages (M B ) to said second measuring points (102), each broadcast message (M B ) including first detection values ( v(t) ) acquired at said first measuring point (101), - at each second measurement point (102), receiving, during each measurement interval (T J ), a broadcast message (M B,J ) transmitted from said first measuring point (101) and including first detection values ( v(t) ) acquired at said first measuring point (101) at an acquisition instant (t K ) preceding said measurement interval (T J ), - at each second measurement point (102), calculating, in response to receiving said broadcast message (M B,J ), third detection values ( P(t)) indicative of the active electric power flowing through a corresponding second measurement point (102) of said electric circuit, characterised in that said third detection values ( P(t)) are calculated at a calculation instant (tc) included in said measurement interval (T J ) and delayed of a predefined latency time (T L ) relative to the acquisition instant (t K ) of the first detection values ( v(t) ) included in the received broadcast message (M B,J ), wherein said third detection values ( P(t)) are calculated based on first detection values ( v(t) ) received at said second measuring point (102) up to said calculation instant (tc) and based on second detection values ( i(t)) acquired at said second measuring point (102) up to the acquisition instant (t K ) of the first detection values ( v(t) ) included in the received broadcast message (M B,J ), wherein the acquisition instant (t K ) of the first detection values ( v(t) ) included in the received broadcast message (M B,J ) is calculated based on said calculation instant (tc) and said latency time (T L ).
  11. Method, according to claim 10, characterised in that said predefined latency time (T L ) has a constant and equal duration for all the second measuring points (102).
  12. Method, according to claim 11, characterised in that said predefined latency time (T L ) is an integer multiple of the duration time (T D ) of each measurement interval.
  13. Method, according to one of the claims from 11 to 12, characterised in that it comprises the step of acquiring, at each second measurement point (102), additional detection values ( S(t) ) related to one or more additional physical quantities.
  14. Method, according to one of the claims from 11 to 13, characterised in that each broadcast message (M B ) includes an address value (A) indicative of a second measuring point (102), from which a response message (M R ) is desired.
  15. Method, according to claim 14, characterised in that it comprises the following step: - at each second measurement point (102), transmitting, during said measurement interval (T J ), in response to receiving said broadcast message (M B,J ), a response message (M R, J ) to said first measuring point (101), if said second measuring point is indicated by the address value (A) included in said broadcast message (M B,J ), said response message (M R, J ) including one or more detection values ( P(t), i(t), S(t) ) calculated or detected at said second measuring point (102).

Description

DESCRIPTION The present invention relates to the field of electric power measurements in electric circuits, such as electric power distribution grids, electric power supply systems, electric switchboards, electric cabinets, and the like. More particularly, the present invention relates to a measuring apparatus and method, which allow accurately measuring the active electric power in an electric circuit. A similar apparatus is for example disclosed in document US 2014/028282 A1. As it is known, energy meters are often used to measure active power in an electric circuit. These measuring devices notoriously ensure a high level of precision but they are generally expensive and bulky, thus being normally inappropriate for use in electric circuits with a huge number of measurement points. In order to overcome these issues, there have been designed measuring apparatuses employing a central measuring unit and a number of peripheral small measuring units, which can be installed as stand-alone devices or onboard other devices (e.g. switching devices) of an electric circuit. The central measuring unit measures RMS voltages and currents (and possibly other physical quantities) at a central measurement point of the electric circuit where conductors (phase and neutral conductors) can be easily accessed. The peripheral measuring units measure RMS currents at peripheral measurement points of the electric circuit and transmit the acquired detection values to the central measuring unit through a communication bus. The central measuring unit then calculates the active electric power flowing through the measurement points of the electric circuit. Even if they show relevant advantages in terms of flexibility of installation, which makes them particularly adapted for use in electric circuits with many measurement points, currently available measuring apparatuses of this type still show relatively low levels of accuracy in measuring the active electric power flowing through the peripheral measurement points of the electric circuit. This inconvenient is basically due to the circumstance that power measurements are typically based on RMS measurements of voltages and currents, phase-shift measurements (which assume that that voltages and currents have perfectly sinusoidal waveforms) or estimations of the power factor in the electric circuit. These measuring apparatuses of the state of the art, additionally, require that relatively complex sensing means (especially for carrying the above-mentioned phase-shift measurements) are installed at each peripheral measurement point with a consequent increase of their overall costs. The main aim of the present invention is to provide an apparatus and method for measuring active electric power in an electric circuit, which allow solving or mitigating the technical problems evidenced above. Within this aim, an object of the present invention is to provide a measuring apparatus and method, which are particularly adapted for use in electric circuits having a large number of measurement points and, at the same time, which ensure high levels of accuracy in measuring active power at the various measurement points of an electric circuit. A further object of the present invention is to provide a measuring apparatus and method, which are relatively easy to install and use on the field and which are relatively inexpensive to implement at industrial level. This aim and these objects are achieved by a measuring apparatus, according to the following claim 1 and the related dependent claims. In a general definition, the measuring apparatus, according to the invention, comprises: a first measuring unit operatively coupled to a first measurement point of the electric circuit. Said first measuring unit is configured to acquire first detection values related to one or more voltages at the first measurement point of said electric circuit;a plurality of second measuring units operatively coupled to a plurality of second measurement points of said electric circuit. Each second measuring unit is configured to acquire second detection values related to one or more currents at a corresponding second measurement point of said electric circuit. The above-mentioned first measuring unit and second measuring units are capable of communicating one with another, in a wired or wireless manner. According to the invention, the aforesaid first measuring unit is configured to transmit in a cyclical manner, with a predefined broadcasting frequency and during subsequent measurement intervals, broadcast messages to said second measuring units. Each broadcast message includes first detection values acquired by said first measuring unit. According to the invention, each second measuring unit is configured to receive, during each measurement interval, a broadcast message transmitted by said first measuring unit and including first detection values acquired by said first measuring unit at an acquisition instant preceding said measuremen