WP2: Task 2.1 Improvements for current measurement with Rogowski coil Prototype of a Magnetic Shielded Rogowski Coil

Transcription

1 WP2: Task 2.1 Improvements for current measurement with Rogowski coil Prototype of a Magnetic Shielded Rogowski Coil ENG61 Future Grid joint workshop PTB Germany

2 Rogowski Coil Unshielded RC: ROCOIL SX-170 M: µh 2

3 Configuration of Magnetic Shield Magnetic shield was constructed by Mumetal cores and flat rings. Dimensions Core 1 (Outer) : 260 x 240 x 54.5 mm / 0.1 mm band thickness (µ at 4mA/cm ~ 60000) Core 2 (Inner) : 154 x 134 x 54.5 mm / 0.1 mm band thickness (µ at 4mA/cm ~ ) Core 3-4 (Top and Bottom) : 260 x 134 x 5 mm / 0.1 mm band thickness (µ at 4mA/cm ~ ) 3

4 Assembly of Magnetic Shield Inner Protection Box Inner Winding 400 Turns with 0,9 mm enameled copper wire Insulation of Top and Bottom Parts Applying of Magnetic Shield 4

5 Assembly of Magnetic Shield Flat Rings Outer Winding Protection box with PSP material Final Isolation 5

6 Calibration Method Current Supply Max. 6000A Measuring Bridge for Electronic Current Transformer WM3000I Reference Current Transformer Rocoil SX-170 M=3.604 µh 500A / 5A applying appropriate primary currents to the RC and the reference CT measuring the ratio error and phase displacement of the RC with the Bridge 6

7 Calibration Setup Measuring Bridge WM3000I AC Power Source Magnetic Shielded Rogowoski Coil Capacitive Bank Reference Current Transformer Unshielded Rogowoski Coil 7

8 Current Linearity Before Magnetic Shield After Magnetic Shield Primary Pos No: Current Ratio Error Phase Error A % crad ,024-0, ,025-0, ,025-0, ,025-0, ,025-0, ,024-0, ,025-0, ,024-0,004 Primary Pos No: Current Ratio Error Phase Error A % crad ,015-0, ,015-0, ,016-0, ,016-0, ,018-0, ,019-0, ,019-0, ,018-0,001 The reason of difference between ratio errors might be regarding to the tightening of Rogowski Coil. Manufacturer declares that gap error of 0.3mm would introduce an output error of less than 0.1%. 8

9 Position of Current Conductor Before Magnetic Shield Primary Current 400A Frequency : 50 Hz Ratio Error (%) Phase Error (crad) Ratio Error (%) Phase Error (crad) Ratio Error (%) Phase Error (crad) Ratio Error (%) Phase Error (crad) Pos No: d = 85 mm d = 105 mm d = 85 mm d = 105 mm 0 0,025-0,004 Deviations from Pos. 0 Deviations from Pos ,008-0,004-0,027-0,004-0,033 0,000-0,052 0, ,008-0,004-0,063-0,004-0,033 0,000-0,088 0, ,071-0,004 0,105-0,004 0,046 0,000 0,080 0, ,003-0,004-0,037-0,004-0,028 0,000-0,062 0,000 After Magnetic Shield Primary Current 400A Frequency : 50 Hz Ratio Error (%) Phase Error (crad) Ratio Error (%) Phase Error (crad) 1 Pos No: d = 105 mm d = 105 mm 0 0,018-0,001 Deviations from Pos ,018-0,001 0,000 0, ,018-0,001 0,000 0, ,018-0,001 0,000 0, ,019-0,001 0,001 0,000 d 4 0 Difference between the worst case (Conductor touching the outer winding) and reference (conductor in the center of the coil) was less than 10 ppm * The diameter of conductor is 20 mm 9

10 Position of Nearby Current Conductor 0 d Before Magnetic Shield After Magnetic Shield Primary Current 400A Frequency : 50 Hz Ratio Error d (cm) (%) Phase Error (crad) 80 0,022-0,004 Ratio Error Phase Error (%) (crad) Deviations from d=80 cm 60 0,022-0,004 0,000 0, ,017-0,004-0,005 0, ,000-0,004-0,022 0,000 Primary Current 400A Frequency : 50 Hz Ratio Error d (cm) (%) Phase Error (crad) 80 0,018-0,001 Ratio Error Phase Error (%) (crad) Deviations from d=80 cm 60 0,018-0,001 0,000 0, ,018-0,001 0,000 0, ,019-0,001 0,001 0,000 The coupling is less than 10 ppm. 10

11 High Frequency Test Results Shielded Unshielded Freq Angular Freq Primary Current DMM 1 DMM 1 Ratio Measured Values Deviation µh µh Hz A V V % crad % crad 3,604 3, , , , ,067 2,090-0,001 3,604 3, , , , ,067 2,091-0,004 0,001-0,003 3,604 3, , , , ,067 2,091-0,009 0,001-0,008 3,604 3, , , , ,067 2,091-0,014 0,001-0,013 3,604 3, , , , ,067 2,092-0,019 0,002-0,018 3,604 3, , , , ,067 2,093-0,024 0,003-0,023 3,604 3, , , , ,067 2,095-0,029 0,005-0,028 3,604 3, , , , ,067 2,097-0,033 0,007-0,032 3,604 3, , , , ,067 2,100-0,038 0,010-0,037 3,604 3, , , , ,067 2,103-0,042 0,013-0,041 3,604 3, , , , ,067 2,107-0,047 0,017-0,046 NI PXIe-1071 Digitizer Based Bridge was used. No integrator was used. Method: Appropriate currents are applied both the magnetic shielded RC and similar RC without shielded, the secondaries of them are compared with the Digitizer Based Bridge. 11

12 Frequency Response Test Results Frequency Response Error RE variation PE variation Frequency 12

13 (VTT MIKES) Current Linearity Linearity of Rogowski coil Measured againts VTT MIKES Rogowski coil dm/m [x10-6 ] Increasing current Decreasing current Applied Current Hz 13

14 (VTT MIKES) Temperature Compensation % Rogowski coil 40 Before temperature compensation % % ppm/K % % % R>10Gohm Temperature % % % 0 0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 5:30 6:00 6:30 7:00 7:30 8:00 8: % Rogowski coil with R=9500 ohm 45 After temperature compensation % resistor % 35 in parallel with the coil % 30 R=9.5k Temperature 3 ppm/k % C to 36 C % % 0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 5:30 6:00 6:30 7:00 7:30 8:

15 Summary Manufacturer Declares Influence of Conductor Position: If the conductor is moved from the central position by a distance equal to 0.5 x the inner coil radius the output will change by less than 0.1%. Influence of External Magnetic Fields: the pick-up for any orientation of the coil is less than 0.1% compared with the output of the coil Our Objective to reduce the immunity of a Rogowski coil against coupling magnetic fields by more than factor of

16 Summary Effect of current conductor position Effect of nearby current conductor Current linearity Temperature dependence < 10 ppm < 10 ppm < 5 ppm < 25 ppm Variations under these effects were decreased by approximately 100 times. Maximum primary current : 1000A, M=3,604 µh OD : 265 mm, ID : 125 mm, H : 75 mm, Weight: 12 kg Shielded RC is much heavier, More expensive than the conventional RC 16

17 Thanks for your attention