GB2201249A - Measuring transformer - Google Patents
Measuring transformer Download PDFInfo
- Publication number
- GB2201249A GB2201249A GB08703386A GB8703386A GB2201249A GB 2201249 A GB2201249 A GB 2201249A GB 08703386 A GB08703386 A GB 08703386A GB 8703386 A GB8703386 A GB 8703386A GB 2201249 A GB2201249 A GB 2201249A
- Authority
- GB
- United Kingdom
- Prior art keywords
- measuring
- current
- coil
- transformer
- measured
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/181—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using coils without a magnetic core, e.g. Rogowski coils
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F38/00—Adaptations of transformers or inductances for specific applications or functions
- H01F38/20—Instruments transformers
- H01F38/22—Instruments transformers for single phase ac
- H01F38/28—Current transformers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
- Measurement Of Current Or Voltage (AREA)
- Transformers For Measuring Instruments (AREA)
Abstract
In a measuring transformer such as in Fig 1a with a measuring circuit such as in Fig 3, the measuring coil (T) is made of a material, e.g. manganin, the specific resistivity of which is greater than 9.10<-8> OMEGA m and the temperature coefficient of which is between +/-2.10<-3>K<-1>. <IMAGE>
Description
Linear transmitting measuring transfor.ar1 applicable as current transformer
The present invention reletes to a linear transmitting measuring transforier, based upon magnetic voltage measuring, applicable as current transformer.
The measuring transformer according to the invention comprises at least one circular closed coreless measuring coil encircling once or several times a conductor conducting a current to be measured, and a measuring resistor and/or a capacitor with a shunt loss resistor connected in series to the measuring resistor, the easuring.resistor and the capacitor connected to the measuring coil terminals.
The measuring transformer according to the invention is actually suitable for replacing the customary current transformers with iron-core coils.
Measuring transformers1 where current easu- rement is based upon magnetic voltage measuring, are known from technical literature.
According to t.he principle of the magnetic voltage measuring - see 0.g, Chattok, A.P.: @On a magnetic potentiometer", Phil.Mag. and I. of Science, 24/1887/94-96 - the induced voltage ii between two spatial end points of the axis of r pliable measuring coil proportional to the magnetic voltage.
Keeps the axis of the measuring coil a closed line, in which case the end points of the axis coincide with each other, the induced voltage ui is proportional to the first derivative of the electric exitation
wherein @1 = N1#i1. and ii means the current to be measured, which passes
N1-times through the closed line of the axis of
the measuring coil, and
M means the mutual inductance between the measuring
coil and the conductor conducting the current ii to be measured.
The prior art of the invention will now be reviewed by eans of the accompanying drawings.
In the drawings
Fig. la and lb is r diagrammatic view of a measuring coil encircling e conductor conducting a current to be measured; Fig. 2a and 2b is a diagrammatic view of another embodiment of c measuring coil encircling a conductor conducting a current to be measured;
Fig. 3 is a schematic circuit. diagram of a measuring transformer.
As shown in Figures 18, lb, 2a and 2b, a conductor V, in which a current i1 to be measured flows, is led through the circle-like closed axis of a measuring coil T. Between coil terminals K1 and K2 an induced voltage ui can be messured. The induced voltage ui is proportional to the first derivative dil of the
dt current il.
In the respect of measurement accuracy, it is suitable the measuring coil T in Figures la and ib being wound uniformly and ring-shaped.
The measuring coil T. shown in Figures 2a and 2b consists of a number of linear coil sections S joined in series to each other forming a closed circle- -like polygon. Between the linear coil sections S there are intermediate gaps H. These intermediate gaps H cause inaccuracy at the measuring. The accuracy cen be increased in this case by insetting ferroxagnetic inserts into the intermediate gaps H.
An advantage of this embodiment is however that the measuring coil T comprising series-connected coil sections S is easy to be fitted around the conductor V, encircling it, without cutting the conductor V in two.
Figures la and 2a show measuring arrangements where the conductor V is led only once through the closed axis of the easuring coil, while in Figures lb and 2b the conductor is enclosed N1-times (three times) by the measuring coil.
In the above cases the current il to be measured in encircled only by one measuring coil T, but if necessary there can be two or even more measuring coils connected in series, arranged coaxially around the conductor V.
The known measuring arrangement of a measuring transformer shown in Fig. 3 comprises a conductor Vconducting the current i1 to be measured, a measuring coil T (e.g. the measuring coil of Fig. la, lb, 2e or 2b) being magnetic coupled with the conductor V, a measuring resistor Rk,a capacitor C connected in series to the measuring resistor Rk and a shunt loss resistor r connected in parallel to the capacitor C. The measuring resistor Rk and the capacitor C are connected to the measuring coil terminals K1, respectively K2.
On the'measuring resistor Rk a measuring signal Uk, on the capacitor C a measuring signal uc can be measured.
The inductive coupling of the measuring coil T with the conductor V is designated with a mutual inductance M,
The impedanc. Z of the measuring coil T is the resultant of the series-connected inductance
L and resistance R of the measuring coil T.
The induced voltage us in the measuring coil T - the current il being encircled Nl-tiDes by the closed axis of the measuring coil, T can be determined by the following equation:
This induced voltage ui generates a secondary current 12 in the closed circuit of the measuring coil T.
For more detailed examination of the above measuring arrangement and for demonstrating its disadyantages especially in respect of application as measuring transformer let's consider the following schematic models:
1.) The shunt lose resistor r r The circuit of the measuring coil T is closed in this case through the measuring resistor.
Rk. The secondary current i2 can be calculated on the bess of the following differential equation:
l.A) Supposed that
di2 .
L# > > i2#(R + Rk),
dt the secondary current
Consequently, the measuring signal uk is proporitonal to the current i1 to be measured: Uk = i2 # Rk = M/L#i1#N1#RK = const # i1
Let's term this model "self-integrating type measuring transformer".
Realising a self-integrating type reasuring transformer at industrial frequency (50 cps, or 60 cps) is unreasonable, because of the necessary measuring coil dimensions. It is also disadvantageous that the measuring accuracy is restricted by the tempe reture-dependence of the coil resistance R. For moderating this inaccuracy
Rk > > R is to be realised.
1.B) In the case of
di2 i2.(R + Rk), L
dt the secondary current i2 can be approximated by
Consequently, the measuring signal Uk is proportional to the differential quotient of the current all to be measured. Let's term this model in the followings "differentiating-type measuring transformer".
If applying measuring device of large input resistance, the resistance of the me- ssuring resistor Rkcan also be comparatively large, so that the temperature-dependende of the coil resistance Rrespecting the messuring accuracy isn't critical.
Since the current i1 to be measured is many times in the heavy-current electrotechnics an approximate sinusoidal wave, tha derivative of which is also a sinusoidal wave, a differentiating- -type measuring'transformer can be applied As simple measuring transformer, e.g. at thermal current protection of electric motors, tripping devices of power circuit breakers, etc.
At practical measuring and current protecting applications an output signal is required, that is not only porportional to the amplitude of the current to be measured but that is in the same phase, too.
A possible solution of the above problem is, the output signal - e.g. the measuring signal
Uk - being integrated by a known electronic integrating circuit.
Let's term a model like this "vol tage-integratlng type measuring transformer".
The applicability of voltage-integ- rating type measuring transformers is limited by the so-called "drift-problem" and by its temperature- -dependence (see e.g. Lebeda, S.; Mähler, A.: "Ro gowaki-coils for exact current measuring at electrode control of arc melting furnaces", Brown Boveri Publications 68/1981, pages 387-389),
2.) In the case of the shunt loss resistor r being much larger than the measuring resistor Rk (r > > Rk), the measuring signal uc is the output signal of the measuring arrangement.Supposed that the input resistance of an instrument connected to the measuring coil terminals K1 and K2, an approximation r # # can be sllowed, in which case the measuring signal Uc is determined by the following relation:
Let's term this model "current-integrating type measuring transformer",
At given engular frequency z and supposed that #2-LC I l, the integrated measuring signal Uc is proportional to the current i1 to be measured, and at the same time they are in-phase.
The measuring error caused by the temperature-dependence of the coil resistance should be reduced by realizing a fairly large ratio Rk.
R
The measuring error caused by a given engular frequency # should be reduced by realizing a rather R + R@ large ratio - . To keep the measuring error teL within en error range specified for current transformers there should be realized such large ratios R@ R + R@
and and ,,that the application of current R integrating type measuring transformers as current transformer is unreasonable.
To realize a signal-to-noise ratio suitable for electric units of customary measuring arrangements, the integrated measuring signal Uc - i.e. the output voltage of the measuring transformer should be about within the voltage order of 1 V,
Rk R + RK
If the requiered large ratios and are R #L realized, the integrated measuring signal Uc can amount even the order of lOOO V, which makes the insulating of the measuring coil complicated.Under extreme circumstances current transformers can be exposed even to-ambient temperature changes of over 60 oK, which affect - in case of a measuring coil T made of copper wire - a coil resistance change of about 25 %. For appropriate moderating this resistance change a ratio
Rk/R = 102...103 should be realized.
A fluctuation of the angular frequency CA) of 1-2 % necessitates a ratio = 10...102, wich means a ratio
Realizing the above conditions by a measuring coil made e.g. of copper wire or other usual coil materials results unreasonable coil dimensions.
It is conceivable that using the above types of measuring transformers as current trsns 'former isn't suitable for different reasons.
It is object of the invention to provide a measuring transformer of simple construction, based upon magnetic voltage measuring. providing linear signal transmission in a wide current range of the current to be measured, and being applicable as current transformer.
A further object of the invention is to provide a temperature-independent signal trsnsmission, which means that the measuring accuracy is also tem- perature-independent within a comparatively wide temperapture range.
It is also an object of the invention to provide a measuring transformer of reasonable dimensions, and necessitating low manufacturing costs.
All these objects are accomplished by means of a measuring transformer comprising at least one circular or circle-,like closed measuring coil encircling once or several times a conductor conducting a current to be measured, a measuring resistor for detecting a measuring signal proportional to the differential quotient of the current to be measured and/or a capacitor with a shunt loss resistor for detecting a measuring signal proportional to the current to be measured, connected in series to the measuring resistor, the measuring resistor and the capacitor being connected to the measuring coil terminals, wherein the measuring coil is according to the invention made of a material. the specific resistivity of which is greater than 9#10-8 8 Q m and the temperature coefficient of which is between -2#10-3 and +2#10-3 K-1. This material can be advantageously e.g. manganin. The specific resistivity of manganin is 4,3#10-7 #m, its temperature coefficient is about loss @-1 The measuring coil can be wound single-layer or multilayer. It can be formed as a cir ocular closed coil or a polygon-shaped closed coil consisting of linear coil sections.
The choice of material of th mea- suring coil according to the invention has the following results - the coil resistance is temperature-independent in-a wide temperature range; - the voltage stress between the layers of the measuring coil
is small even at short circuit current values,
therefore the inner insulation of the measuring
coil cen be prepared relatively simply; - the dimensions of the measuring transformer are
reasonable.
All these advantages enable the measuring transformer according to the invention to be applied as current transformer.
When the measuring transformer according to the invention being applied e.g. in form of a current-integrating type measuring transformer, in which case the measuring resistor is negligible, the resistance and the inductivity of the measuring coil and the resistance of the shunt loss resistor can be rated so that the output voltage of the measuring transformer, i.e. the integrated measuring signal is linear proportional to the current to be measured.
The invention will now be described in connection with some preferable embodiments by referring to Figs. 3 and 4.
Fig. 3 shows a schematic circuit diagram of a measuring transformer according to the invent ion;
Fig, 4 shows a schematic vektor diagram of the dynamical function of the measuring transformer shown in Fig. 3.
The measuring transformer shown in
Fig. 3 comprises r Rasring coil T being inductively coupled with a conductor V conducting r current il to be measured. The inductive coupling of the measuring coil T with the conductor V is characterized by a mu tual inductance M, The impedance Z is the resultant of the series-connected inductance L and resistance R of the measuring coil T.
A measuring resistor Rk and a capacitor
C with a shunt loss resistor r connected in series to the measuring resistor Rk are connected to the measuring coil terminals K1, K2. A secondary current i2 flows in the closed circuit of the measuring coil T. On the me asuring resistor Rk 5 measuring signal Uk, on the capacitor C an integrated measuring signal Uc can be peasu- red.
a) In case of a differentiating type measuring transformer the following relations should,be extant: @ #L < < R Rk < $lt; R (I)
and r r o , wherein CO is the angular frequency of the fundamental harmonic of the current il to be measured.
In this case practically only the me- asuring resistor Rk is connected to the coil terminals Kl and K2.
to meet the above requirements - relations (I) -, the measuring coil T can be wouno of relatively fine wire - wire of relatively smell diameter -, therefore the measuring transformer can be re- alized by reasonable dimensions.
Since in this case
wherein the resistance R of the measuring coil T is - according to the invention - practically t,emperature- lindependent. an exact signal transmission canbe provided by means of a measuring resistor Rk of relatively small resistance. Nevertheless, the measuring resistor Rk should advantageous.ly be rated so that the measuring signal Uk s i20Rk is within a voltage range of 1 V, which results at the rated value of the current il to be measured an appropriate signal-to-noise ratio.
The measuring accuracy of this measuring transformer being rated at the fundamental harmonic of the current il to be measured is decreased by increasing order of higher harmonics. Therefore, in case of the measuring signal uk being used for determining, the transconductance of a current (e.g. for detecting the dynamic slope of a short-circuit current) the measuring circuit should be rated so, that the relations (I) are extant at higher angular frequncies. Advantageously, the measuring transformer should be rated at the angular frequency of the highest not negligible harmonic of the current 4 1 to be measured. - Determining the transconductance of a current is however almost important field of application of this type of measuring transformer.
will the measuring 'signal uk of 'the above measuring transformer be integrated by an electronic integrating circuit, the measuring arrangement functions as voltage-integrating type measuring transformer, the output signal of which is amplitude-proportional end in-phase to the current il to be measured.
Integrating exactly.by electronic means is still relatively complicated. The measuring transformer according to the invention is however quite advantageous also in this relation, since the coil re-.
sistance R of the measuring coil T is practically temperature-independent and therefore the measuring accuracy of the measuring transformer isn't influenced by the temperature, respectively, the measuring resistor
Rk can be rated within a quite wide resistance-interval.
b) For getting a current-integrating type measuring transformer the capacitor C with the shunt loss resistor r should be connected to the coil terminals
K1 and K2, wherein the measuring resistor Rk is negligible (Rk t 0; see Fig. 3). In this arrangement the shunt loss resistor r replaces the lose factor ts 8 of the capacitor
C (see Fig. 4) and the input resistance of a measuring trans former T. For required adjusting the shunt loss resistor r involves a regulating resistor, too. So the shunt loss resistor r is a resulting equivalent component.
In case of the actual values of the resistance R and the inductance L of the measuring coil
T, the capacitor C and the shunt loss resistor r meeting the relations @
R > > and #2#LC = 1 (II)
#C at the given angular frequency # of the fundamental harmonic of the current ii to te measured, the integrated measuring signal uc is linear proportional to the current i1 to be measured. Under these circumstances it can be achieved that the integrated measuring signal UC c is amplitude-proportional and at the same time in-phase to the current il to be measured. This dynamic state is shown by means of a vector diagram in Fig. 4.
- On the basis of Fig. 4 the following system of equations can be constructed: UR#cos# + UL#sin# = Ui
UC + UR#sin# = UL#cos# IC = I2#cos# I@ = I2#sin# wherein UR = I2#R; UL=I2##L;
and
The solution of this system of equations is the following:
The vectors of Fig. 4 (Ui, U,C, UL, URn
I1, I2, IC, Ir) designated with capitals are ordered to the voltages, respectively currents of Fig. 3 designated with congruent small letters.
Since the resistance R of the measuring coil T in this dynamic state is practically temperatu re-independent, the temperature-changes don't influence the measuring accuracy. Advantageously, the shunt loss resistor r is also temperature-independent.
For providing e good signal-to-noise ratio the measuring signal UC should be within the voltage order of 1 V.
As conceivable from the relations. (III) and (IV), the measuring transformer according to the invention, being used as current-integrating type measuring transformer, enables current measuring of high accuracy within about one frequency order of the angular frequency # of the current i1 to be measured and within a relatively wide current range.
Being applied as current transformer, the measuring transformer according to the invention provides relatively exect measuring of the higher harmonics of the current i1 to be measured. This feature can be explained by the fact that the induced voltage
Ui changes linear proportional to'the angular frequency # of the fundamental harmonic of the current i1 to be measured, while the ratio uc/u@ changes inversely proportional to the same angular frequency @ . ough the change of #L is disturbing, it causes predominantly only phase angle.
In the following the invention will be explained in more detail on the basis of a numerical rating example:
A current-integrating type measuring transformer according to the invention being applied as bar-type current transformer in an encapsulated equipment of 400 kV and SF6-gas:
Nominal current of the measuring transfor
mer: I1 = 1500 A
Nominal frequency of the measuring trans
former: f 1 50 Hz
Number of the current's to be measured
flowing through the closed axis of the meas- uring coil: N1 = 1
The measuring coil is prepared in a form similar to the embodiment in Fig. 2e. It consists of two ring-shaped parts, each of them assembled of twelve linear coil sections Joined in series to each other.
Diameter of the coil sections : 40 mm
Height of the coil sections t 90 mm
Medium diameter of the ring
-shaped parts :380 mm
Total height of the measuring coil z 85 mm
Material of the measuring coil: manganin wire, p 0,16 mm
Total mass of the winding :2,5 kg.
Further electric particulars: Capacitance of the capacitor z C r 1,4 F Loss factor of the capacitor : tg# = 1.19 10-3 Resistance connected to the output
of the measuring transformer : Ro I l M# The above measuring transformer is reted in a way that its phase angle and transmission error at the nominal frequency f*50 Hz) is zero.
The following table shows calculated values of phase angle and transmission error in the case of the frequency of the current to be measured being different from the nominal frequency f.
Frequency of the Transmission error Phase angle current to be measured (%) (grad) (Hz)
49 1,2 10-4 5,2 10-2
51 2,8 10-4 2,8 10-2
100 1,3 101 1,5
200 7,7 10-1 3,8
300 1,9 6,0
400 3,4 8,1
500 5,3 10,2
1000 21,1 20,5
On the strength of the Above tabie it is conceivable that the phase angle calculated for even the 10th harmonic is - compared with the fundamental harmonic t relatively small, only about 1,02 grad.
The usefulness of the invention appears first of all at its application as differentiating type or currentintegrating type measuring transformer. Compared with the customary current transformers the measuring transformer according to the invention provides higher measuring accuracy with smaller size oi the measuring coil at the same time.
Applying the invention as current-integrating measuring transformer r measuring signal can be provided which is proportional and in-phase to the current to be measured. This is a new useful effect of the invention, since integrating a signal of a magnetic voltmeter purely by means of passive elements and with the.required accuracy of current transformers hasn't been eccomplished before.
The measuring transformer according to the invention complies with the standardized re quirements o'f the current transformers with iron-core coils Its transmission is linear proportional to the current to be measured in a wide current range.
The invention is useable in a wide scope of application. For measuring and for circuit protection the measuring transformer' according to the invention has the same, common output, in contrast with the customary current transformers, wich should be provided with a measuring iron-core and a separate relay core,
Since the output of the measuring transformer according to the invention is of 1voltage generator's characters - in contrast with the customary current transformers having an output of current ge nerators character1 -, digital measuring devices and electronic protection relais can be matched better to it.
The total mess of the measuring transformer according to the invention is considerably less than the.mass of the known current transformers.
The invention provides a correct long @range signal transmission.
In consequence of the measuring coil resistance being practically temperature-independent, the invention ie applicable between extreme temperature-limits.
It is also advantageous that an accidental cable break doesn't cause any danger.
The measuring transformer according to the invention can be realized simply and at relatively lower cost.
Claims (5)
1. Linear transmitting measuring transformer applicable as current transformer. comprising at least one circular or polygon-shaped closed magnetic measuring coil encircling once or several times a conductor conducting a current (i1) to be measured1 said measuring coil being wound single-layer or multilayer, a measuring resistor for detecting a measuring signal (Uk) proportional to the differential quotient of the current (il) to be measured and a capacitor with a shunt loss resistor for detecting an integrated measuring signal (Uc) proportional to the current (i1) to be measured connected in series to the measuring resistor, said measuring resistor afld said capacitor being connected to the measuring coil terminals, wherein the measuring coil (T) is made of a material, the specific reslstivity os which is greater than 9#10-8#m and the temperature coefficient of which is between @2#10-3 k-1.
2. Linear transmitting measuring transformer applicable as current transformer, comprising at least one circular or polygon-shaped closed magnetic measuring coil encircling 'once or several times a conductor conducting a current (i1) to be measured, said measuring coil being wound single-layer or multilayer and a measuring resistor for detecting a measuring signal (auk) proportional to the differential quotient of the current (i1) to be measured connected to the measuring coil terminals, wherein the measuring coil (T) is made of a material, the specific resistivity of which is greater than 9#10-8 #m and the temperature coefficient'of which is between #2#10-
3 k-1
3,.Linear transmitting measuring transformer applicable as current transformer, compri- sing at least one circular or polygon-shaped closed magnetic measuring coil encircling once or several times a conductor conducting a current (i1) to be measured, said measuring coil being wound single-layer or multilayer'and a capacitor with a shunt loss resistor for detecting an integrated measuring signal (uc) proportionalto the current (i1) to be measured connected to the measuring coil terminals, wherein the measuring coil (T) is made of a material, the specific resistivity of which is greater than 9#10-8 #m and the temperature coefficient of which is between #2#10-3 k-1.
4, Linear transmitting measuring transformer according to any of claims 1 to 3, wherein the measuring coil (T) is made of manganin.
5. A transformer according to any preceding claim substantially as herein described with reference to and as show@ in Figures 3 and 4 of the accompanying drawings.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873701779 DE3701779A1 (en) | 1987-02-13 | 1987-01-22 | AS A CURRENT TRANSFORMER, LINEAR TRANSMITTER |
| GB08703386A GB2201249A (en) | 1987-02-13 | 1987-02-13 | Measuring transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08703386A GB2201249A (en) | 1987-02-13 | 1987-02-13 | Measuring transformer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8703386D0 GB8703386D0 (en) | 1987-03-18 |
| GB2201249A true GB2201249A (en) | 1988-08-24 |
Family
ID=10612277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08703386A Pending GB2201249A (en) | 1987-02-13 | 1987-02-13 | Measuring transformer |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE3701779A1 (en) |
| GB (1) | GB2201249A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5473300A (en) * | 1990-03-27 | 1995-12-05 | Watson; Michael B. | Cable coupling transformer |
| EP0723159A1 (en) * | 1995-01-14 | 1996-07-24 | Kommanditgesellschaft Ritz Messwandler GmbH & Co. | Current measuring device with measuring transducer |
| WO1998058267A1 (en) * | 1997-06-16 | 1998-12-23 | Trench Switzerland Ag | Toroidal core current transformer with integrated measuring shunt |
| EP1059536A1 (en) * | 1996-10-23 | 2000-12-13 | Chi-Sang Lau | Alternating current sensor |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB537129A (en) * | 1939-12-12 | 1941-06-10 | Venner Time Switches Ltd | Improvements in the temperature correction of watt-hour meters and other instruments |
| GB1078459A (en) * | 1965-04-23 | 1967-08-09 | Telemecanique Electrique | Improvements in/or relating to apparatus for detecting or measuring alternating currents |
| EP0074297A1 (en) * | 1981-08-26 | 1983-03-16 | Merlin Gerin | Hybrid compensated current transformer |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1281545B (en) * | 1963-05-29 | 1968-10-31 | Siemens Ag | Iron core converter with air gap for current measurement |
| DE1181802B (en) * | 1963-06-21 | 1964-11-19 | Siemens Ag | Winding with good frequency transmission and low resonance voltage increase for transformers, transducers or the like. |
| DE1791011A1 (en) * | 1968-08-28 | 1971-10-14 | Grosskopf Rudolf Dr Ing | Ammeter |
| DE2656817A1 (en) * | 1976-12-15 | 1978-06-22 | Siemens Ag | Potential separation current measurement sensor - uses magnetic voltage sensor with single or multiple windings |
| GB2034487B (en) * | 1978-11-14 | 1982-10-06 | Central Electr Generat Board | Alternating current measuring devices |
-
1987
- 1987-01-22 DE DE19873701779 patent/DE3701779A1/en active Granted
- 1987-02-13 GB GB08703386A patent/GB2201249A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB537129A (en) * | 1939-12-12 | 1941-06-10 | Venner Time Switches Ltd | Improvements in the temperature correction of watt-hour meters and other instruments |
| GB1078459A (en) * | 1965-04-23 | 1967-08-09 | Telemecanique Electrique | Improvements in/or relating to apparatus for detecting or measuring alternating currents |
| EP0074297A1 (en) * | 1981-08-26 | 1983-03-16 | Merlin Gerin | Hybrid compensated current transformer |
Non-Patent Citations (1)
| Title |
|---|
| }ELECTRICAL MEASUREMENTS AND MEASURING INSTRUMENTS} (1970)PAGE 670 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5473300A (en) * | 1990-03-27 | 1995-12-05 | Watson; Michael B. | Cable coupling transformer |
| EP0723159A1 (en) * | 1995-01-14 | 1996-07-24 | Kommanditgesellschaft Ritz Messwandler GmbH & Co. | Current measuring device with measuring transducer |
| EP1059536A1 (en) * | 1996-10-23 | 2000-12-13 | Chi-Sang Lau | Alternating current sensor |
| WO1998058267A1 (en) * | 1997-06-16 | 1998-12-23 | Trench Switzerland Ag | Toroidal core current transformer with integrated measuring shunt |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3701779A1 (en) | 1988-08-04 |
| GB8703386D0 (en) | 1987-03-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Dorf | The electrical engineering handbook-six volume set | |
| Ramboz | Machinable Rogowski coil, design, and calibration | |
| Ward et al. | Using Rogowski coils for transient current measurements | |
| US4749940A (en) | Folded bar current sensor | |
| KR960011531B1 (en) | Current sensor | |
| US8847576B1 (en) | Phase compensation method and apparatus for current transformers | |
| Habrych et al. | HDI PCB Rogowski coils for automated electrical power system applications | |
| Hill et al. | An ac double bridge with inductively coupled ratio arms for precision platinum-resistance thermometry | |
| US4322710A (en) | Electrical resistors | |
| GB2201249A (en) | Measuring transformer | |
| Wang et al. | Design of printed-circuit board Rogowski coil for highly accurate current measurement | |
| EP3116001A1 (en) | Impedance-compensated current transformer | |
| US3287680A (en) | Electrical device | |
| US3445753A (en) | Variable standard mutual inductance circuit with air core transformer and tap changing cascaded autotransformers | |
| Malewski | Wirewound shunts for measurement of fast current impulses | |
| West et al. | An improved two-stage current transformer | |
| Binnie et al. | Leakage inductance and interwinding capacitance in toroidal ratio transformers | |
| GB2154806A (en) | Clip-on current measuring device | |
| Wibowo et al. | Design and testing of Rogowski coil based PCB double helix for gas insulated switchgear 150 kV aplication | |
| Edgcumbe | Industrial electrical measuring instruments | |
| Wieserman et al. | High frequency, high temperature specific core loss and dynamic BH hysteresis loop characteristics of soft magnetic alloys | |
| JPH0836003A (en) | Resistance-value measuring method | |
| RU2191391C2 (en) | Current pickup | |
| Brooks | The accuracy of commercial electrical measurements | |
| Olsen | Electronics: a course book for students |