Pulsed Power Technology
A Compact 500 KV/50 ns High Voltage Resistive Probe with High
Division Ratio
S.J. Mousavi, G.H. Rahimi, H. Khadem Kalan, J. Safaee, and M. Barati
Electronic and Communication Research Center, Majdzadeh, Tehran, 1355874541, I.R. IRAN
Phone :+9 8(021) 55765748, E-mail: mousavi314@gmail.com
Abstract – Resistive probes have been developed
for fast rise time, high voltage measurements in
many pulsed power applications. This paper describes the design, construction, calibration and
testing of a fast rise time resistive high voltage
probe. Physically, the compact probe consists of
two stages. The first stage is the liquid resistor portion which is responsible for the majority of the
division ratio. The second stage of the divider is
composed of discrete high frequency resistors in a
small, electrically shielded box. The probe is calibrated in time-domain and frequency domain precisely. The frequency response of the probe was
extracted by a network analyzer using a novel
technique. The time domain calibration is done by
using a homemade 2 kV/50 ns pulser with a standard Pintek HV-39pro (40 kV/220 MHz) probe.
The resistive probe can easily capture a voltage
pulse of 500 kV/50 ns generated by a Marx generator through a dummy load and then it decrease the
high voltage pulse with high enough division ratio
(14000) for sampling oscilloscope without any distortion or high voltage problem.
details. The divider was calibrated through the
16 kv/50 ns Marx Generator (MG) by Pintek HV39pro probe. The divider could successfully capture
the output pulse of MG without any distortion. The
results of time domain calibration are in good agreement with 10 MHz bandwidths obtained from the frequency calibration. Finally, the divider proves its good
performance in measuring of the 420 kv MG comparing by simulation result.
2. Principle and modeling
A voltage divider can be easily constructed as a tube
filled with a liquid resistive solution, with a top and
bottom electrode (Fig. 1). An intermediate tap (a grid,
plate, etc.) connects to the liquid solution and experiences only a fraction of the full voltage applied. The
distance between the tap and the bottom electrodes
sets the dividing ratio. The liquid column between tap
(mid electrode) and ground is called lower arm, while
the one between tap and HV electrode is called upper
arm of the LRD.
1. Introduction
Measurement of high voltage (HV), steep front, and
short duration pulses has received considerable attention in many fields, such as pulsed gas lasers, pulsed
x-ray generators and transients in power systems [l–3].
The most important instrumentation in high voltage
measurements is the divider, as the magnitude of the
voltage can vary from tens of kilovolts to hundreds of
kilovolts. For practical purposes, not only extremely
high division ratio but also wide bandwidth of the
divider should be achieved simultaneously [3].
A liquid resistive divider (LRD) often is selected
as its construction is relatively simple and it allows for
high ohmic values. The frequency response of such a
high impedance resistive divider is limited by its stray
capacitances to the high voltage and ground terminals.
This problem is usually allayed by field control, using
electrode geometries chosen to make the electric field
density almost constant along the resistor. Lengths of
divider are important in this way because it shape the
electric field. On the other hand, to obtain a divider
with high ratio; LRDs must be constructed in long
lengths. In this paper a two stage LRD which is consists of potassium dichromate solution with high division ratio and acceptable length is described. Furthermore, the overall structure of divider is depicted in
HV Electrode
Insulator Column
Solution
Mid Electrode (Tap)
Ground Electrode
Fig. 1. Simple liquid resistive divider (LRD)
For a divider implemented as a vertical column,
along all of its length, the product of the resistance
and the capacitance between any two points (neglecting the inductance) is constant when it is compensated. Resistance variations due to temperature or
concentration changes are reflected identically in
lower and upper arm of LRDs and the division ratio is
thus unchanged.
The resistive and capacitive parts of both arms are
balanced by their geometrical symmetry (i.e. by their
inverse dependence from section and length). This
292
Oral Session
means that even changes in the tube diameter along its
vertical axis will not influence the divider balance.
Use of two series divider which is called “two
stage divider” is interested for increasing the division
ratio. Fig. 2 demonstrate the circuit model of two
stage divider. Actually, the second stage is constructed
of low inductance resistors having good frequency
response.
First stage
high specific heat, which exceeds that for metals by an
order of magnitude; a high power; a rapid recovery of
electric strength after an occasional breakdown; etc.
3.1. First stage
The dissolved substance was used in LRD is potassium dichromate (K2Cr2O7). Referring to [4] Brass
material was selected for electrodes as a compatible
materials for potassium dichromate solution of LRD.
Cross section of lower arm of LRD is shown in
Fig. 3.
Second stage
Body
Mid
Electrode
Ground
Electrode
Fig. 2. Circuit model of two stage LRD
a
Referring to [4] and concerning details mentioned
above the circuit model of two stage divider can be
extracted as shown in Fig. 2. Also, the value of elements can be estimated as below:
l
l
RHV  HV ; RLV  LV ;
A
A
CHV 
0 A
 A
; CLV  0 ,
dHV
dLV
(1)
in which:
lHV  dHV is the length of high voltage arm;
b
lLV  dLV is the length of lo voltage arm;
Fig. 3. Lower arm cross section of LRD (a); structure
dimension (b)
A is the iameter of LRD;
 is the resistivity of liquid solution;
ε is the permittivity of solution.
The division ratio (DR) of this model could be
evaluated as follow:
RLV
R2
(2)
DR 
.
RLV  RHV R1  R 2
According to Eq. (2), the division ratio is affected
by lower and upper arm lengths. Decreasing the lower
LV arm length and increasing the higher HV arm
length, both lead to the more division ratio. In practice, decreasing of LV arm length to a few millimeters
is difficult. In addition, increasing of HV arm could be
result in long structure.
3. Overall structure
It is preferable to use mixtures of salts and acids solution as elements with active electrical resistances in
pulsed power. Their considerable characteristics are as
follows [4]: a high electric strength of solutions (up to
300 kV/cm for a microsecond pulse duration); a high
electric energy dissipated in a unit mass because of the
In this figure, the housing cover is made of polyamide material. By the special shape of the ground
electrode support we allow the bubbles to easily escape in the driver filling process. As shown in Fig. 3,
the mid electrode is insulated from ground electrode
by piece of Teflon substance. The LRD column is
formed by centralizing two insulators tubes. Therefore, all (ground, mid and HV) electrodes are constructed in ringing shape to reduce the area of effective electrode surfaces and increase the total resistance
of LRD. To achieve the acceptable ratio, the lengths of
upper arm and lower arm was selected 25 cm and
2 mm respectively which leads to division ratio of
125. The choice of solution concentration was performed in order to achieve 5 kΩ total resistance in
LRD. If the compact divider is interested the divider
should be submerged in the transformer oil to avoid
any unwanted flashover. In Fig. 3, b the dimensions of
final structure is shown .
3.2. Second stage
Output of first stage of LRD is fed to a low inductance
5.6 KΩ resistance as a upper element (R1 in Fig. 2) of
293
Pulsed Power Technology
subsequent stage. Final output of LRD is transmitted
to oscilloscope by 50 Ohm terminated RG-402 cable.
To sum up, the total theoretical division ratio of LRD
will be as follows :
  5600 / 50  125
–1
line fixture was associated with LRD. As demonstrate
in Fig. 7, the cut-off 3 dB frequency is around 10 MHz.
 14000–1.
CH2
4. Calibration
CH4
After assembling, we calibrated the LRD with the
standard 40 kV/220 MHz HV_39pro probe manufactured by Pintek, and a Tektronix 2 kV/250 MHz
P6150. The first reference pulse which was used as
calibration pulse is shown in Fig. 4, with 50 ns rise
time and around 1 kV magnitude. Characteristic of
pulse registered by P6150 probe. As seen in Fig. 5
LRD output appropriately follow the reference pulse.
1200
Amplitude
Fig. 6. Comparison of Marx Generator Pulse measurements
by 15HF-HVP and LRD (CH2 and CH4 represent the reference and LRD waveform, respectively)
1000
800
600
400
200
0
-200
-400
-600
-1
0
1
2
3
4
5
6
7
8
9
Time
 10–7
Fig. 4. Calibration pulse acquired with P6150 probe
Amplitude
0.1
0.08
0.06
Fig. 7. Frequency response of LRD acquired by
ROHDE&SCHWARZ FSP SPECTRUM ANALYSER
0.04
0.02
Final calibration is extracting the frequency response of LRD. In this manner, a 50 Ω transmission
line fixture was associated with LRD. As demonstrate
in Fig. 7, the cut-off 3 dB frequency is around
10 MHz.
As be seen in Fig. 7, the attenuation ratio of LDR
is about 83 dB which leads to DR of LRD as follow:
0
-0.02
-0.04
-0.06
-1
0
1
2
3
4
5
6
7
Time
Fig. 5. Registered waveforms by LRD
8
9
 10–7
In addition, calibration of LRD was done by 16 kV
MG pulse for HV performance certification. Registered waveforms are shown in Fig. 6 that certify the
good performance of LRD. The division ratio of
around 14000 is inferred.
Final calibration is extracting the frequency response of LRD. In this manner, a 50 Ω transmission
line fixture was associated with LRD. As demonstrate
in Fig. 7, the cut-off 3 dB frequency is around
10 MHz.
Final calibration is extracting the frequency
response of LRD. In this manner, a 50 Ω transmission
10(93/ 20)  104.15  14125.
5. High voltage experimental verification
To verify the LRD measurement, output pulse of a
MG with 420 kV amplitude was measured and experimental results was obtained. To compare and verify the captured pulse shape, the test stand was modeled (Fig. 8) and simulated through commercial circuit
analysis. Figures 9 and 10 display the simulation and
experimental results, respectively. These figures confirm the good LRD performance.
294
Oral Session
L1
1
R1
2
5.6u
2.5
1.5u
1
U1
2
V
R_HVLD
C1
R_Load
14.28n
IC = 500k
5k
74
0
0
0
Fig. 8. Schematic model of system is drawn in Capture CIS
KV
Time
Fig. 9. Simulation result of modeled system in Fig. 8
6. Conclusion
The compact HV and fast tow stage liquid resistive
divider is described in this paper. Also, the overall
structure and analytic model of divider is presented.
Calibration process was done with both Tektronix
P6150 2 kV/250 MHz and Pintek HV-39pro
40 kV/220 MHz probes. Frequency response of divider was registered by the ROHDE&SCHWARZ FSP
spectrum analyzer and 10 MHz bandwidth was obtained. Finally, reliable HV performance of divider
was experienced through a 420 kV Marx generator
and was certified with simulation result.
References
Fig. 10. Experimental MG pulse obtained from LRD
[1] Z.Y. Lee, Rev. Sci. Instrum., 54, 1060–1062
(1983).
[2] D.M. Barret,
S.R. Byron,
E.A. Crawford,
D.H. Ford, W.D. Kimura, and M.J. Kusher, Rev.
Sci. Instrum. 56, 2111–2115 (1985).
[3] S.A. Boggs and N. Fujimoto, IEEE Trans. Elect.
Insulation EI-19, 87–92 (1984).
[4] A.I. Gerasimov, “Aqueous-Solution High-Voltage
Resistors: Development, Study, and Application
(Review),” 49, 1, pp. 1–26 (2006).
295