MRC7300AThree Phase Transformer Measuring BridgeFor Resistance- and Ratio- Measurements

Transformer

measuring devices

Transformer Measuring Bridge

With the precision measuring bridgeMRC7300A it is possible to safely deter-mine winding resistances, transforma-tion ratios and phase angles of distribu-tion transformers up to 100 MVA andmore. Further it is possible to automati-cally move the tap changer of the H.V.winding to the next tap and to performcool-down measurements in tempera-ture rise tests to calculate the resistancein the case of a load disconnection @ t0.

The MRC7300A 3-phase measuring bridgecan be use by transformer manufacturers,electricity supply companies and repaircompanies having to carry out on-sitemeasurements under unfavourable condi-tions. Resistance values ranging from 50 µΩ to500 Ω can easily be measured and loggedwith the internal measuring current of amaximum of 15 A up to a power of approxi-mately 100 MVA and more. To allow a com-parison of the measured values to previousmeasurements a conversion of the tem-perature of the test object is provided inorder to compare measurements of a de-tached transformer carried out in the winterand measurements carried out in anotherseason.The provided Kelvin clips and lugs as wellas all cables required allow an easy andsafe connection of the measuring bridge tothe test object. The tap changer can bemoved and measured step by step bymeans of the automatic system which isconnected to the tap changers signallingcontrol of the transformer.The measuring range is between 0.9:1 and2500:1 in the case of the transformationratio; the resolution of the angle measure-ment is 0.1 degrees. The logging of allmeasured values is performed by a sepa-rate printer, computer or via the internalmemory.

The magnetic loading of the transformer isperformed quickly due to a relatively highstarting voltage (50V).

The unloading of the core is very safe, asthe energy is destroyed in the MRC7300Aby a ballast resistor and varistors except fora negligible rest.

Surge arresters protect the MRC7300Afrom peak voltages. During the moving ofthe tap changer to the next tap, with themeasuring current still flowing, the measur-ing circuits are disconnected from the testobject to protect the inputs amplfiers.

• Automatic measurement without any manual interaction

• Resistance measurement with high accuracy and up to 15 A current

• Ratio measurement including phase angle and magnetising current

• Dual measuring method for faster measurements

• Automatic vector group detection

• Tap changer control measures all transformer taps automatically

• Heat - up measurement including algorithm for resistance at t = 0

• Temperature measurement and compensation to 20 °C for Cu or Al

• USB port to get full external control over the instrument

• Thermo printer

FeaturesPhase selection device:

The measuring bridge MRC7300A containsa phase selection device. With this device itis possible to connect the complete trans-former with all of its high and low voltagewindings so that reconnection to other wind-ings between the individual measurements isnot necessary. This not only saves time butalso increases safety. Either by using thefront panel keyboard or by using the serialinterface, complex programs which arelogged correspondingly can be started bypressing a few keys or entering a few com-mands.For many measurements it is necessary toknow the vector group, e.g. in the case of thetransformation ratio measurement and thedual measuring method. Depending on thevector group and also on the correspondingcommands, the automatic selection of the LVwinding to a HV winding is required. 34 vec-tor groups are permanently programmed inthe MRC7300A, more can be added if nec-essary.

The internal phase selection device allowsthe measurement of the three magnetisingcurrents and the measurement of two tem-peratures via PT100.

SCHUETZ MESSTECHNIK GMBH, Rheinstrasse 7d, D-14513 TeltowSeptember 2018. Changes are subject to change witho ut notice.

Questions?

phone: +49 (0)3328 / 3179 - 0 fax: +49 (0)3328 / 3179 - 10 email: sales@schuetz-messtechnik.com

Here you will get technical assistance as well ascomplete information regarding features, prices,shipment and reselling.

www.ohmmeter.de

Made in Germany

MRC7300AThree Phase Transformer Measuring Bridge

Transformermeasuring devices

Transformer Measuring Bridge

SCHUETZ MESSTECHNIK GMBH, Rheinstrasse 7d, D-14513 TeltowSeptember 2018. Changes are subject to change withou t notice.

The phase selection device is designed forbest interference immunity. To make itEMC-safe, in particular with regard to thegreat number of terminals, all relays arebistable. It maintains its control state,which can be checked at any time, even inthe case of a supply failure. Suddenlyopened are by a power or line failure areavoided. Even in this critical case thetransformers energy is deloaded in the in-ternal damping resistor.

Dual measuring method:

With the phase selection device you canuse the dual measuring method. In thismethod, windings on the HV and the LVside which are on the same leg are seriallyconnected. To measure both windings youonly have to load and unload the core oncewhich saves time.

Tap changer measurements:

You can connect the step-by-step systemof the tap changer on the back of theMRC7300A via an adapter. The basicmethod (resistance measurement) is asfollows:

In the case of a measurement a floatingcontact is closed for one second when themeasurement is completed. This muststart the step-by-step system. The tapchanger signalling switch must give a re-spond within this second. If it does the nexttap is driven and measurement is carriedout. If it doesn’t, the measurement or theseries of measurements is stopped, thelast measured value (or the only one if notap changer was connected) is displayedand is logged.

In the case of transformers ratio measure-ment an automatic tap-to-tap measure-ment is possible. Here, the magnetisingcurrent can be measured at each tap, too.

Increase of measuring current:

The maximum measuring current theMRC7300A can provide is 15 A. This valueis reached in most cases, only a very highwinding resistance limits the current. Toreach a high measuring stability, theMRC7300A is provided with a specialmeasuring current .

Sometimes it is necessary to increase themeasuring current in order to measure ex-treme low-resistance objects such as

filament-heating transformers. The phaseselection device can only be used with amaximum measuring current of 15 A.

100 A measuring current accessoryCUR7300-100 is available which is con-trolled by the MRC7300A, provided withloading and unloading equipment and 4-pole connection directly to the winding ofthe test object. The corresponding termi-nals of the MRC7300A can also be usedto connect external current sources ofhigher voltage to reach an even fasterloading of the core or to measure higherresistances. These are options.

Heating tests:

The MRC7300A is provided with an inter-nal time clock to perform cooling curves inheating tests. For this purpose the time isstarted beginning with zero at the time theload is stopped at the test object and cool-ing begins. After connecting theMRC7300A measurements are startedand a series of measurements are carriedout at the set interval. When the end of themeasurements is triggered off (STOP keyor command) an additional regressioncalculation can be started, which deter-mines the resistance at t=0.

Safety:

A warning accessory is availablewhich warns the user and allows himto work at the test object (e.g. recon-nection) by means of red and greenlights, respectively. If the warning lightis activated no measurement is possi-ble if it is defect or disconnected.

Questions?

phone: +49 (0)3328 / 3179 - 0

fax: +49 (0)3328 / 3179 - 10

email: sales@schuetz-messtechnik.com

Here you will get technical assistance as well ascomplete information regarding features, prices,shipment and reselling.

www.ohmmeter.de

Made in Germany

Displayed result for RATIO

Measurements

Displayed result for RESISTANCE

Measurement

Transformer

measuring devices

Transformer Measuring Bridge

MRC7300A

• CUR 7300 – 100 current extension: Featuring 100 A measuring current. Provided with fast load and unload equipment.

• PT 100 1/10 DIN – temperature probe: 4-pole MiniDIN connector cable length 1,5 m F = ±(0,03°C+0,0005•|t|)

Available enhancements

SCHUETZ MESSTECHNIK GMBH, Rheinstrasse 7d, D-14513 TeltowSeptember 2017. Changes are subject to change withou t notice.

Resistance measurementRange 50 µΩ – 500 Ω autorangingTest object limits: about 30 to 250 MVA depends on typeMax. error ± 0.1 % of MV ± 1 digit Measuring Current,max. 25 A Loading Voltage,max. 50 VMeasuring Power,max. 250 VA

Ratio measurementRange 0.900 – 2,500 autorangingMax. error ± 0.1 % of actual value ± 1 digitMeasuring voltage 180 V (other voltage on demand)Measuring frequency 50 Hz / 60 Hz (line dependent)

Phase angle measurementRange (one phase) - 9.9 ° to + 9.9 °Range (three phase) - 179.9 ° to + 180 °Max. error ± 0.1 ° ± 3 digits

Magnetising current measurementRange 1 mA – 2000 mAMax. error ± 1 %

Temperature measurementRange - 20 °C to + 100 °C, linearized (for PT 100)Max. error 0.2 °K (without probe error)Type of sensor PT 100 temperature probeApplication #1: Temperature for TC-Compensation #2: Temperature other test point optional more probes with internal or external scanner (depends on number)

Start of measurement by using keypad and via USB

Interface USB Thermo Printer

Size/Weight H22 B42 T43 cm / approx. 16 kg

• Cable various length, with Kelvin lugs or Kelvin clamps

• DKD – calibration certificate from the ‚Deutscher Kalibrierdienst‘

Available accessories

Questions?

phone: +49 (0)3328 / 3179 - 0

fax: +49 (0)3328 / 3179 - 10

email: sales@schuetz-messtechnik.com

Here you will get technical assistance as well ascomplete information regarding features, prices,shipment and reselling.

www.ohmmeter.de

Made in Germany