Recent Advances in Civil Engineering and Mechanics
Traceability of AC High Voltage Measurements Up to 100 kV at NIS
ALI M. EL-RIFAIE1, HALA M. ABDEL MAGEED2, OMAR M. ALADDIN2
1
High Voltage Laboratory, 2Electrical Quantites Laboratory
National Institute for Standards (NIS)
Tersa st., Haram, Giza
EGYPT
alisystem11@yahoo.com halaabdelmegeed@yahoo.com omarmaladdin@yahoo.com
Abstract: - AC high voltage measurements traceability up to 100 kV has been achieved at the National Institute
for Standards (NIS), Egypt. The Phenix High Voltage divider (KVM100) with a full range of 100 kV AC is
being used with its display in parallel with a high sensitive digital voltmeter. The traceability has been realized
by calibrating this digital voltmeter then using it to calibrate the divider display readings. In addition, the
divider ratio has been calibrated. Accurate and traceable high voltage values have been obtained associated
with their expanded uncertainties. Enhanced uncertainties have been achieved using this calibration technique.
Key-Words: - AC High Voltage, Accurate Measurements, Transformation Ratio, Traceability, Calibration
Technique, Uncertainty.
Phenix display reading as well as the DVM readings
are recorded.
The measurement of the DVM is then multiplied
by the estimated transformation ratio to determine
the corresponding high voltage AC readings. The
sources of uncertainty and the uncertainty budget
have been estimated. Enhanced uncertainties have
been obtained in this traceable calibration.
1 Introduction
Accurate measurement of high voltages and
currents is vital in monitoring power flows in
electric power systems, metering electric power
and energy [1]. The electric power industry for
instrumentation, and testing applications require
accurate high voltage measurements [2,3]. These
measurements are done through several methods,
the series resistance micro-ammeter, the resistance
potential divider, the generating voltmeter and the
sphere gaps are all possible methods; however a
high voltage divider remains the most common
method to measure the high voltage output of a high
voltage source [4].
In this paper, the traceability to the International
System of Units (SI) for 100 kV high AC voltage
measurements has been provided. This is achieved
by calibrating a HP 3458A high precision digital
voltmeter (DVM) via the Fluke 5720A traceable
calibrator; then this high precise DVM is placed in
parallel with the display of the Phenix High Voltage
divider (KVM100) with a full range of 100 kV AC.
The Fluke 5720A calibrator which is traceable to
the Josephson Voltage Standard (JVS) [5-7] is used
to produce 1 kV at the high voltage side of the
Phenix divider, while the voltage at the low voltage
side is measured via the calibrated HP 3458A DVM;
this is done to accurately determine the Phenix
divider transformation ratio (TR). A Haefely Trench
100 kV AC source of one/two stages (PZT100) [8]
is used to supply the high voltage side of the
KVM100 with a voltage up to 100 kV at 50 Hz, the
ISBN: 978-960-474-403-9
2 Calibration of the Phenix KVM100
Divider
In order to determine the voltage transformation
ratio (TR) of the Phenix KVM100, several methods
might be used. The binary step up method [7] is one
method that relies on a sequence of steps that
combine and separate the used dividers to accurately
determine the values of the used resistors. One other
method is to use a turn's ratio meter that can
estimate the TR of the voltage divider at different
test voltages.
In this paper the traceable calibrator and digital
voltmeter are used to determine the TR of the
KVM100. The Fluke 5720A calibrator supplies the
high voltage side of the KVM100 with 1000 V AC
at 50 Hz, while the DVM is measuring its output
voltage from the low voltage side terminals. The TR
is estimated from the equation:
(1)
272
Recent Advances in Civil Engineering and Mechanics
Where VCalibrator is the actual value of the calibrator
voltage and VDVM is the actual value of the average
for 40 DVM voltage readings corresponding to the
calibrator voltage. Figure 1 shows the block diagram
for the Phenix divider calibration to estimate its
transformation ratio. The temperature and relative
humidity of the calibration laboratory have been
adjusted and fairly controlled to (23±1)C
4 Results and Analysis
The uncertainties of the calibration results of the
DVM, the Phenix KVM100 divider and the Phenix
KVM100 display results up to 100 kV AC have
been investigated.
The uncertainty is defined as the range of error
of a measurement within which the true value of the
measurand is estimated to lie within a stated level of
confidence [9]. Type A and Type B evaluations are
the two approaches to estimate the uncertainty
sources. Type A evaluations of standard uncertainty
components are founded on normal distributions,
while type B evaluations are founded on a suitable
chosen distributions. The combined standard
uncertainty equals to the Root Sum Square (RSS),
of all the uncertainty contributions [9,10]
The uncertainty budgets have been evaluated for
all calibrations. All components of the combined
standard uncertainty (Type A and Type B) have
been taken into consideration.
The expanded uncertainty has been evaluated by
using the coverage factor k = 2, to give a level of
confidence of approximately 95% according to the
ISO GUM [10,11].
The detailed uncertainty budget for calibrating
the 100 kV at 50 Hz (as an example) has been listed
in table 1. Table 2 illustrates the actual values of the
AC voltages from 2 kV up to 100 kV at 50 Hz and
their expanded uncertainties. Figure 3 shows the
actual values of the Phenix readings with their
expanded uncertainties. Although it seems that the
expanded uncertainties increase with the increase of
the voltage ranges their percentage values decrease.
There is a degradation of the percentage
uncertainties with respect to the voltage ranges to
reach 0.01% from 80 kV to 100 kV. At lower
voltage
ranges
the
percentage
expanded
uncertainties are slightly higher but they don’t
exceed 0.05%. It is clearly shown that very small
uncertainty values have been achieved for high AC
voltages using this calibration technique.
Fig. 1: Block Diagram of Phenix divider calibration
3 Calibration of the Phenix KVM100
Display
The Phenix KVM100 consists of a high voltage
divider and 4 ½ digit LCD display (with both low
and high voltage ranges). Its two main parts are
connected by connecting cables. The calibrated HP
3458A DVM is used as a reference standard to
calibrate the KVM100.
The Phenix KVM100 divider is connected to the
PZT100 AC source. Figure 2 illustrates the
KVM100 Phenix calibration block diagram. By
applying the calibrated TR, the actual values of the
input high voltages from 2 kV to 18 kV (at the low
range) and from 20 kV up to 100 kV (at the high
range) have been acquired.
Actual Values with their Expanded Uncertainties
(kV)
100
96
92
88
84
80
76
72
68
64
60
56
52
48
44
40
36
32
28
24
20
16
12
8
4
0
Actual Values
Expanded Uncertainties
2
4
6
8
10
12
14
16
18
20
30
40
50
60
70
80
Voltage Ranges (kV)
Fig. 2: Phenix Calibration Block Diagram
ISBN: 978-960-474-403-9
Fig. 3: Actual values of the Phinex readings
273
90
100
Recent Advances in Civil Engineering and Mechanics
Table 1: Uncertainty Budget of Calibrating 100 kV at 50 Hz
Uncertainty
Sources
Repeatability
of the DVM
readings
Resolution
of the DVM
readings
calibration
certificate of
the calibrator
Repeatability
of the
calibrator
readings
Repeatability
of the
Phenix
readings
Resolution
of the
Phenix
readings
Standard
Uncertainty
Probability
Distribution
Divider
Ci
Uncertainty
Contribution
9.48 E-03 V
Normal
1
1
9.48 E-03 V
5.00 E-6 V
Rectangular
3
1
2.89 E-6 V
1.30 E-5 V
Normal
1
1
1.30 E-5 V
9.82 E-3 V
Normal
1
1
9.82 E-3 V
4.72 V
Normal
1
1
4.72 V
5.00 V
Rectangular
3
1
2.89 V
Combined standard uncertainty
Effective degrees of freedom
Expanded Uncertainty at confidence level 95%, (k = 2)
±5.53 V
∞
±11.06 V
Table 2: Actual values of the voltages from 2 kV to100 kV at 50 Hz and their expanded uncertainties
Nominal
Values
(kV)
2
4
6
8
10
12
14
16
18
20
30
40
50
60
70
80
90
100
ISBN: 978-960-474-403-9
Measured
Values
(kV)
2.028
3.960
6.014
8.005
10.006
12.008
14.022
16.041
18.033
20.025
29.984
39.980
50.130
60.040
70.030
80.070
90.250
100.190
Actual
Values
(kV)
2.047
3.984
6.054
8.057
10.014
12.290
13.981
15.985
17.985
20.035
29.981
39.951
50.052
59.947
69.334
79.952
90.080
99.958
±Expanded
Uncertainty
(V)
1.01
1.51
2.23
2.56
3.19
3.87
4.43
4.97
5.93
6.67
9.87
11.06
11.06
11.06
11.06
11.06
11.06
11.06
274
±Expanded
Uncertainty (%)
0.05
0.04
0.04
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.01
0.01
0.01
Recent Advances in Civil Engineering and Mechanics
5 Conclusion
A new calibration technique has been used at NIS to
disseminate the traceability to the high voltage AC
measurements (up to 100 kV). The traceability to
the SI units has been obtained. Measurements have
been carried out using a high voltage meter
(KVM100). The KVM100 divider and its display
have been accurately calibrated. The actual values
of the Phenix readings as well as calibration
uncertainties have been calculated.
The percentage expanded uncertainties for the
voltage ranges from 2 kV to 100 kV don’t exceed
0.05% of their values. These percentage expanded
uncertainties have been decreased to 0.01% at the
higher ranges. Improved uncertainty results have
been attained using this calibration methodology.
[4]
[5]
[6]
[7]
References:
[1] G.J. FitzPatrick and E.D. Simmon, "High
voltage and current metrology at NIST.
Precision measurements of the past, present,
and the future," Annual Report Conference on
Electrical
Insulation
and
Dielectric
Phenomena, 2001, pp. 277-280
[2] C.K. Dwivedi and M. B. Daigavane "Multipurpose low cost DC high voltage generator
(60 kV output), using Cockcroft-Walton
voltage multiplier circuit" International
Journal of Science and Technology Education
Research Vol. 2 (7), pp. 109 - 119, July 2011
[3] Guizhen Wang, QiutingJia and Gang Cao," A
measurement method of high DC voltage"
ISBN: 978-960-474-403-9
[8]
Electrical
&
Electronics
Engineering
Symposium (EEESYM), 2012
J R Lucas, High Voltage Engineering - 2001,
Chapter 11" High Voltage Direct Current
Transmission," pp. 184-204
Hala M. Abdel Mageed, and Ali M. El-Rifaie,
“Electrical Metrology Applications of
LabVIEW Software,” Journal of Software and
Engineering Applications, March 2013, pp.
113-120
Hala M. Abdel Mageed, and Ali M. El-Rifaie,
“Electrical Quantities in Terms of the
International System of Units,” Processing
World Congress on Engineering 2013
Conference, 3-5 July, London, UK
Sang Hwa Lee, Kwang Min Yu Jeon Hong
Kang, MunSeog Kim, Kyu Tae Kim," A
Josephson voltage-traceable DC high-voltage
divider evaluation using the binary step-up
method" Measurement 45 (2012), pp.488-492
http://www.haefely.com/pdf/LL_KIT.pdf
Fluke Corporation, “Calibration: Philosophy
in Practice,” 2nd Edition, Legal Department,
Everett, WA 98206-9090, May 1994
[10] “The Expression of Uncertainty and
Confidence in Measurement,” United
Kingdom Accreditation Service, NA-MAS, M
3003, 1st Edition, January 2007.
[11] Uncertainty Guide to the Expression of
Uncertainty in Measurement, JCGM 100,
2008
[9]
275