WO2012146924A1

WO2012146924A1 - Electrical measurement apparatus having a detector providing an identification signal and corresponding method

Info

Publication number: WO2012146924A1
Application number: PCT/GB2012/050914
Authority: WO
Inventors: Ian Sykes; Julia Szajdzicka; Paul Clay
Original assignee: Northern Design (Electronics) Limited
Priority date: 2011-04-27
Filing date: 2012-04-26
Publication date: 2012-11-01
Also published as: GB2493688B; US20140125313A1; GB2493688A; CA2834345A1; NZ617310A; GB201106993D0; US20170269127A1; AU2012247307B2; AU2012247307A1; MX2013012530A; EP2702417A1

Abstract

A three - phase toroidal current transducer comprises a cuboid detector body (12), having three cylindrical passages (14) each for receiving a single - phase cable of a three - phase load (not shown). Each of the three passages (14) has an embedded toroidal winding (not shown) which is used to detect a current in the load cable (also not shown). Signals representing the current in each of the three individual load cables are sent to a meter (not shown), which may be located remotely. The signals are transmitted along a multi-core signal cable (16), which has a standard connector (18) for a plug-in connection to the meter. One of the wires in the multi-core signal cable (16) is connected to a component in the transducer (10) that identifies the rating of the transducer, so that the meter can determine this automatically when the signal cable is plugged in.

Description

ELECTRICAL MEASUREMENT APPARATUS HAVING A DETECTOR PROVIDING AN IDENTIFICATION SIGNAL AND CORRESPONDING METHOD

The esen invention relates to an electrical measurement apparatus, ami method, and is concerned particularly with an electrical measurement apparatus and method suitable for use in an electrical me aring system.

In conunerciaX premises particularly, th electricity s ge of several devices o appiiancea hereinafter referred to generally as loads"^', is often monitored using separate meters for eac load. In such cases, in order to derive valuable dat about the ene gy u age of each load it is necessary to collate me ered values manually, and subsequently ente the dat manually o a compute for processing. i¾ previousl cdftsider d example of electricity me e brings together fixed numbe of metering unit and combines them i a unitary o ing/ together with a common visual display and processing means to manipulate and presen the data collected by the individual meterin units. Signal vires axe, used to carry the measurement signals from current detectors such as current transducers or transformers located locally at each load. The combined multi-meter load is particularl suite to moder premises in which th electrical supply en ers the bu lding at a singl location, an is controlled from a single control panel,

Modern electronic electricit meters are designed to

measure variety of load type and sizes_* OIOU/MOM FCT/GB-MU/U9Q914

Current inputs fc thft n»t«rs ar« standardised to accept « specific si¾n«X fc:yj¾e_:: and value «rhi repreeents a- larger measured value of current ..at, the load. A range of externa current mn*t&zw*tie or traneducers iref used to conve th detected ^ im y^ current into repreeentative

^eecondary" aignal that may be measured by the mtAvinq. teXi exampl a meter may accept a 0.333 Vac signal which repreaenta any nominal primary nxxtmnt detetroined by the aelection :..©£^' an appropriate external current transducer. Typica external traneducera ma be of a split or toroicJal yp#; auch as IQ# Aii/0,333V or 500 ftmp/0,333v.

When a metering system is installed the uaeir mus select the moat appropriate tranaforxner*/transducers for the measured load dependent on the maximum current that the load would draw in normal operation. These devices may be physically locate some distance away from the meters themselves, * example the traijaformers tranedubWs wa be located in a eeparate switch encloaur* «*· in a differen room. Many meter* may b installed together and may fee connected -tat different ranges of transformers/transducers.

During commissionin of feb meterin system the installing engineer muat program the individual meters to provide readings tha ar scaled in proportion t© the specific t naformers r transducers p whic they are respectivel connected. This often presents the practical problem of identifying which set ·.©*; wires is associated with which remotely located transduce /trans ormer.

J To: assist with this, the installing engine r ar f lly labels the i es with the load size and type before;

i stalling, the transf rsiers/transducers. I this sta is forgotten <¾r performed inaccurately it may be necessary to remove th installation and start again..

If mistakes are made during installation or coirsrtissioning these saay remain undetected for long periods, and indeed may never foe picked up. H we , such mistakes can be costly. For example if a 200 Am : transducer is connected to a meter which is prograramed to scale for a ISC Κχνφ

transducer, hen 200 Amps is detected by the transducer the secondary signal will provide Q.333 V to the eter. Th meter is scaled to assume that Q.333 V i equivalent to 150 Amps so will display readings which are in erro by the ratio 150/200 (i.e. a 25% error). This discrepancy ma not b obviotxs to the meter reader, and the power/energy readings accepted .may lead to errors in billing and

possibly the taking of inappropriate management decisions based on the erroneous data. Larger errors in scaling may be less likely to escape detection.

Preferred embodiments of the present invention aim to address at least some of th a oremehtio ed shortcomings in the prior systems.

The present invention is defined in the attached

independent claims, to which refe ence should now be made. Further* preferred features may foe © nd_: in th sub-claims appended thereto. Acco ding to the presen in en ion there is provided, electrical measurement apparatus or measuring an

electrical parameter of device, the a at s_^ comprising a m^ er and a detector, wherein the de c r is χζ$ή ύ to detect the electrical parameter and transmit a measurement signal to the meter, which signal is representative of the detected electrical parameter, arid wherein th detector is a ng d to provide to th meter an identi i?«tion signal for identifyin the detector to the meter.

In. a preferred arrangement the¹ idehtification sig al may be derived from a c rap nent in the detector or in a

electrical connection between th detector and the meter, o a component associated wit either.

Th identification signal may be derived frqi! the presence and/d. valae of th component. Preferably the detector com ises a component havin ;a measurable value, which measurable valu serve a the identificatio signal.

Th detector m b arranged to communica with the mete vi reless!y. Alternatively, or in. addition, the detector may be: connected to the mete by wire. In a preferred

arrangemen th detector comprises a resistive element, th value of which is measured b h ^ meter to: determine the identity o the detector.

Th meter may comprise identification means* which

preferably comprises ^a circuit, which is arranged in use to receive the identi ication signal and to s it to identi the detector.

4 The indention als includes a detector for use in. the measurement of ¾ΪΪ electrical parameter of a d vice, w erein the detector is arranged to detec the electrical paamete and transmi a measu m n signal to a meter, which signal is representative of the detected electrical arame r, and wherein the detector is: arranged to provide to meter an identif cation s gnal fo identifying the detector to the me r. The detector may be according to any statement herein.

The electrical parameter to be measured may comprise electrical current and/o power, The invention also includes a method of meas r g an electrical parameter of a device, the method comprising detecting the electrical parameter using a detector/ and transmitting a measurement signal to a meter, which signal is representative of the detected electrical parameter, and wherein the method further comprises providing to the met r an identification signal for identif ing the detector to the meter.

The method may comprise identifying the detector by

detection and/or measurement f a component in or

associated with the detector, th presence and/or value of which component serves to identify th detector.

Th invention may comprise any combination of the features: or limitations referred t herein, except suoh a

combination of features as are mutually exclusive. A preferred embodiment of the present invention will now be

5 descr ed b way of example only, with re erenc to the, accompanying diagrammatic drawings, in which:

Figu e 1 shows schematically a detector, in the form f a curren transducer, for use in apparatus according to a embodimen of the present invention and

Figure 2 is a schematic circuit diagram of the current transducer of Figure 1.._.

Turning to Figure 1, there is shown, generally a 10, a three - phase toroidal current transducer: com sing a cuboid detector body 12, having three cylindrical passages 14 each fo receiving a single ™ phase cable of a three ··^■ phase load (not shown}_* Each of the three passages 14 has a embedded toroidal wi di g (not shown) which is used to detect current in the load cabl (also not shown) .

Signals representing the current in each o the three individual load cables are sent t a mete {not shown) , which may be located remotely. T e signals are transmitted along a multi-core signal cable 16, which has a standard connector 18 for plug-in connection to the meter.

As will be described below, one of the wires in the multi- core signal cable 16 is connected to a componen in the transducer 10 that identifies the ratin of the transducer, so that the meter ca determine this automatically he the signal cable is plugged in.

Figure £ shows the circuit o the transducer 10. The three currents in the three single ~ phase load cables are represented by II, 12 and 13, and the three toroidal

6 windings ar represented by Ylj T2 and T3. In each case a burden r sis or, respectively Rbl_:, Rb2 and Rfc3 is connected etween ground, and a s g al line to: produce voltage sign ls vi, V2 and V3 fo supply via cable 16 to the meter. Other 5 wires n the cable. 16 include a ground connection VO and a- connection to a identification resisto Hi, itself

connected to g unds the value of. the ident ica ion resistor Ri can be

10 de ^rm½"^ei!< fey resistor ~ detector circuit in the

processor in the meter, and this is used to. set the ating of the transducer 10 which, the meter uses when calculating the c r en i« the load cables. For example, the meter may fee programmed to determine that an identification resisto I S having a value o 2 kQ me s that the transducer is rated at 100Α/0»333ν, which means that if_: a voltage o 0, 333V is measured at any of VI1, Vi2 or Vi3 this represents a current of 100& in the respective load cable.

20 Of course the identi ication component need not b a

resistor. ¾ith appropriate circuitry the meter could determine the rating of the transducer by detecting the value of different type of component. However a resistor provides a particularly inexpensive solution.

25

furthermore the current detector need no be a transducer, but could for example fo a transformer. In such a case the circuit would be different as there would be two voltage ident ication lines for each of the single ~ phase

30 currents. Again a simple resisto could be used as the

identifίcation componen .

7 The ex^'iftple given above is of a three - phase load

measurement, but the invention is equally applicable to a single - phase load* which would require th us of fewer wires in the cable 16,

During a powering up of the meter the resistor - detecto circuit in the meter determine® the value of the resistor and automatically configures the mete scaling and

calibr tion to suit the transducer connected, without error o ambiq ity to save tim during commissioning.

The standard connector 18 is easily plugged into the meter, which also saves time during installation and commissioning of the meter system.

Embodiments of the invention, aim to add a low cost

component to the transducer or se of transducers which is detected y an additional measurement circuit i the mete . resistor is sufficient for this purpose* and adds

negligibl cost to the transducer. Resistor values can be accurately measured by the mete to determine which

transducer is fitted at the end of the secondary wires.

The accuracy of the resisto detector could be sufficient as to diff rentiate between many primary scaling factor a d, if required^ transducer types. An example of how this could work is laid out in the table shown below:

1 Resistor I CT Primary Assumed i CT Typ Assumed !

! Type A {Small Spirt CT) I

1.2KQ ,A _Amn I Type B (Medium Slit CT) I

1.3kQ ou Amp I Type C (Large Spli CD

M«4kQ Ί I Type D (Small Ring CD I

8 1.5kQ Type E (targe Ring CT) |

2kD Type A (Small Split CT)

2.2kO Type B (Medium Slit CT)

2.3kfl 100 Amp Type C (Urge Split CT) 1

2.4kO Type D {Small Ring CT) I

2.5kQ Type £ (Large; Ring CT)

2kQ Type A (Small Split GT) |

3.2ΚΩ J p& (Medium Slit CT) |

"S^' ka 150 Amp T ype ^'c^'"'^ CT)

3.4kQ Type D (Small Ring CT)

"¾5kO Type e (Large Ring CT) I

4kQ Type A (Small Split CT) i ^"4.2kQ Typ B (Medium Slrt CT)

4.3k¾ 200 Amp Type C (Large ipWt GT) I

^! 4.4k3¾ Type D (Small Ring CT) i

4.5kn Type E (Large Ring CT)

, 5k¾ Type A (Small Split CT |

S.2kQ Type B (Medium Slit CT) j

S.3kQ 300 Amp Type C (Large Split CT)

^' 5,4kfl Type D (Small Ring CT) S.SkfJ Type E (Large Ring CT) I

Whilst endeavouring in the, foregoing specifica ion to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect t any patentable fea ure or combination of features referred to herein, and/or shown in the drawings, whether o not particular emphasis has bee placed thereon.

9

Claims

2. Electrical m asurement- apparatus for measu ing- a:n electrical paramete of a device, the apparatus comprising a meter and a detector, wherein the detecto is arranged to detect the electrical parameter and transmit a measu eme t signal to the meter, which signal is representative of the detected electrical param t and wherei the detector is arranged to provide to the meter an identification signal for identifying th detector to the meter<

2. Electrical measurement apparatus according to Claim 1, wherein the identification signal is derived from a

component in the detector or in an electrical connection between the detector and the meter, or associated with either .

3, Electrical measurement apparatus according to Claim 2, wherein the identification signal is derived from the presence end/or value of th component . . Electrical measurement apparatus according to any of Claims 1 to 3 wherein the detector comprises a component having a measurable value, which measurable value serves as th identi i ation signal.

5. Electrical measuremen apparatus according to any of th preceding claims, wherein th detecto is arranged to communicate with^' the meter wirel ssly, §♦ Electrical measurement., apparatus according to any of e preceding claims, wherein the detector may be connected t th meter by wi e,

7. Eie<?t3fic?al measur ment apparatus according to any of the rec ding^' claims, wh e n the detector comprises a resistive element, the value of which is measured by the meter to determine the identity of the detector.

8. Electrical measuremen apparatus according to any of the preceding claims, wherein the meter comprises

identif cation means, which comprises a circuit arranged in use to receive the identi cation signal and to use it to identify the detector,

$. h detector for use in the measurement of an

electricai parameter of a device, wherein the detector is arranged to detect the electrical parameter and transmit a measurement signal to a meter, which signal is

representative of the detected electrical parameter, and wherein the detector is arranged to provid to a meter an identifica ion signal fo identifying the detector to the mete .

10. A method of measuring an electrical parameter of a device, the method comprising detecting the electrical paramete using detectorv and transmitting a ai asurement signal t meter, which signal is representative of the detected electrical parameter, and wherein th method further comprises providing to the mete an ideritif.c t.ion signal fo identifying the detector to the meter. II. A me h d according to Claim 10, comprising identif ing the detector, by detection and/or measurement of a corn ones in or associated with th detector^ the resen e and/or value .of which component serves as_: the ident fica ion signal .