Doble-2000 RTD Paper
Transcript of Doble-2000 RTD Paper
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RTD as a Valuable Tool in Partial Discharge Measurementson Rotating Machines
Z. Berler, I. Blokhintsev, A. Golubev, G. Paoletti, A. Romashkov
Cutler Hammer Predictive Diagnostics
Abstract : This paper presents the authors’ practical experience
in the on-line measurement of partial discharges in medium
voltage motor and generator stator windings using the RTD as a
partial discharge detector. Results of off-line calibration on
several machines are also presented.
IntroductionOn-line measurement of partial discharges (PD) has proved to be an
effective tool in evaluating the condition of stator insulation in high
and medium voltage electric motors and generators [1]. This method
is widely used in addition to the traditional off-line insulation tests
performed during scheduled outages.
Most of PD technologies available now on the market for on-linemeasurements function within the radio-frequency band of PD
signals. Such technologies have the common problem resulting from
very rapid attenuation of the high frequency signal as it travels
through the winding. Therefore, sensors commonly installed at
winding terminals have a limited zone of sensitivity and provide
valuable information for that zone only [4]. The evident solution to
this problem is the use of PD sensors imbedded into the winding to
get information on the winding itself. Some of the PD technology
vendors suggest installing specially designed sensors into a winding,
but this approach is relatively expensive and requires an extensive
machine outage and invasion into the winding assembly.
Alternatively, most of the HV machines already have RTD detectors
embedded into the winding by the manufacturer and these detectorscan be used for partial discharge measurements [2,4]. Cutler-
Hammer has over two years of experience using RTDs as PD
detectors. The special PD transducer (RFVS) was designed for
connection to the RTD wire at the RTD terminal block located on
the frame of the motor or generator. The transducer does not disturb
temperature measurements and only passes high frequency PD
signals to the PD instrument. Over 300 machines, primarily HV
motors, were tested during the past two years with good results.
RTDs were used for both the initial survey/evaluation and for on-
going periodic measurements and data trending.
RTDs are currently very effective in trending of machine PD activity
when used with an analyzer that can effectively reject noise and
process PD data. With sensor calibration the use of RTDs can be
further applied to allow comparisons between different machines.The issue of sensor calibration requires further evaluation to help
advance the technology and use of RTDs in determining the
machine’s insulation condition. Several machines have been
calibrated, but more field data is necessary for the establishment of
good quantitative data. This paper proposes a calibration procedure
and presents the results of off-line calibration
on several machines. The problems and the vision of future
improvements are also discussed.
Why do We Need the RTD as a PD Detector?The traditional approach for PD detection in rotating machines uses
sensors installed near machine line terminals. What is the value of
data obtained from such sensors and what additional information is
required to reliably assess winding insulation condition? Based on
our experience, PD sensors located near machine line terminals
provide valuable information for line terminals and, possibly, for a
ring bus, but not for the winding.
The example below presents the data obtained on-line from a
37,000kVA, 13.8kV generator and confirms this statement. The
generator has an 80pF coupling capacitor installed on each line
terminal and also 12 RTDs evenly distributed around thecircumference of the stator core. Six RTDs are placed on the exciter
and six on the turbine ends of the machine. Figure 1 presents three
sets of oscillograms taken from 80 pF coupling capacitor (Plot #1)
and from RTD#1 (Plot #2) and RTD#7 (Plot #3). All of them are on
the same phase “A”. RTDs are also located in the same slot on the
exciter and turbine ends respectively. The oscilloscope was triggered
from the PD pulse originating near the line terminals on phase A
and also from the pulse originating near each of the two RTDs. One
can see that the coupling capacitor provides no response to the PD
originating in the winding on either side of the generator. The
opposite is true as well. The attenuation of PD signal along the slot
is also very high and exceeds 10 times. Therefore, for a complete
analysis, it is necessary to install additional sensors into a winding
or to use RTDs to get information about the winding condition.
1 >1 >1 >1 >
2 >2 >2 >2 >
3 >3 >3 >3 >
1) CC_ A: 40 mVolt 200 ns2) RTD01: 40 mVolt 200 ns3) RTD07: 40 mVolt 200 ns
Triggering from lin e terminal PD.
1 >1 >1 >1 >
2 >2 >2 >2 >
3 >3 >3 >3 >
1) CC_ A: 40 mVolt 200 ns2) RTD01: 40 mVolt 200 ns3) RTD07: 40 mVolt 200 ns
Tri ggeri ng fr om slot PD on the exciter
end.
1 >1 >1 >1 >
2 >2 >2 >2 >
3 >3 >3 >3 >
1) CC_ A: 40 mVolt 200 ns2) RTD01: 40 mVolt 200 ns3) RTD07: 40 mVolt 200 ns
Triggering from winding PD on the
turbi ne end.
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Figure 1. PD pulse attenuation in a winding
The effects of signal attenuation discussed above may cause
mistakes in evaluating stator winding insulation condition, if sensors
located at machine line terminals were the only ones used for
assessment. The example below at figure 2 presents PD test results
of three 13.8kV motors of a similar design at the same facility. All
describing motors have permanent RFCT sensors placed on surge
capacitor grounding conductors. The test was also provided withtemporal PD sensors connected to RTD terminals. Figure 2 (top)
shows maximum PD magnitudes recorded from RFCT sensors.
Based on these results, we can conclude that the motor1 is in a good
state and the motors 2 and 3 have moderate level of discharges. The
data from three RTD’s showed highest reading for each motor are
shown on figure 2 (bottom). Conclusions, based on this data, are the
same as above for the motors 2 and 3. But the conclusion is different
for the motor 1. It has high level of PD at the zone of RTD01 and is
the first candidate for additional testing and internal inspection.
RFCT Sensors
Motor1 Motor2 Motor3
RTD Sensors
Motor1 Motor2 Motor3
Figure 2. PD maximum magnitude by RFCT’s and RTD’s.
Why do We Need Calibration?The real need to calibrate or normalize a PD measuring circuit on a
rotating machine exists today. As the science of Partial Discharge
measurement was making its first steps, it was agreed that
calibration on rotating machine is a very difficult procedure.
Therefore, it was decided to utilize the Partial Discharge Magnitude
parameter measured in millivolts or Volts [1]. Based on that, the
only valid procedure of using PD data is through relative
comparison of PD data collected using the same vendor’s
technology over time on the same machine or between similar
machines. This situation was bearable while the number of PD
technology users was relatively small and most of sensors’
installation, data collection and interpretation were provided by a
qualified expert.
Now the situation is different. As PD technology is maturing, real-
life cases reveal the need for a standardized PD measuring circuit
calibration procedure. For instance, paper [3] reported a 19,000HP
motor failure just because the 80pF couplers were installed about
4m away from the motor line terminals. That caused signal
attenuation by a factor of 5 and resulted in misinterpretation of the
PD data. As a result the authors of [3] have now normalized all
their PD sensors with pulse generator and oscilloscope and are now
using normalized data for relative comparison between monitored
motors. This is an example of how uncalibrated sensors defeated
the original predictive expectations of the on-line PD sensors.
The reason of such a difference can be easily understood from
simplified diagram below showing typical sensors connection in a
motor terminal box. PD in a winding or near line terminals
produces small surge traveling to the feeder. In general, pulse
current induced by PD, which is really detecting by PD measuring
instrument, is split into several branches. Part of the current goes
through 80pF coupling capacitor, part of the current goes throughsurge capacitor circuit and the rest of it goes through the feeder.
The current distribution through described branches and part of PD
signal detected by any particular PD sensor depends upon
impedance of each branch including inductance of every used wire.
Therefore, the presence or absence of any element in this diagram
and their wiring, how many cables is used per phase and a surge
impedance of the single cables and many more reasons - all this will
affect PD reading from sensors.
Surge
Impedanceof Cable
5-30 Ohms 50 Ohm
Impedance
80 pF
Capacitor
Surge
Capacitor 500,000pF
RFCTRFCT
Winding
PD
Feeder
Figure 3. Sensors layout in motor terminal box
Authors, who are using universal PD analyzer, which is able to read
PD data from PD sensors installed by different PD technology
vendors, face the problem described above on everyday basis. The
example presented below on figure 4 compares PD magnitudes from
80pF couplers and RFCT’s placed on surge capacitor grounding
conductor measured on-line on 13.8 kV motor at the same time.
Both sensors were of the same manufacturer. The first three bars
present data obtained from 80pF coupling capacitors on the phases
A, B and C and three last bars are related to data obtained fron
RFCT’s. One can see two times difference in signal magnitudes.
Where is the truth?
Figure 4. PD magnitude from two different types of sensors on
13.8kV motor
1The table below summarizes our experience with different sensors,
we have used in both off-line and on-line PD tests on mediumvoltage motors. The better numbers, as a rule, can be reached at off-
line test, when all auxiliary equipment can be disconnected. In any
case, the variations in sensitivity even for the same sensor can be
very significant and confirm the necessity of a calibration.
1 The table does not cover all possible variations in measuring
circuits and sensor layouts and can be somewhat different for
PD instruments using different frequency band.
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Table 1Sensor Type Sensitivity
Range [V/nC]
Comments
Capacitor
(1nF loaded
50Ohm)
2.0 – 0.5 Depends upon surge impedance of
auxiliary devices and feeder or bus.
Capacitor
(80pF loaded50Ohm)
1.0 – 0.2 Same as above and inductance of
measuring circuit.
RFCT(5 Ohm)
on surge capacitor
ground
0.3 – 0.1 Depends upon surge impedance of
auxiliary devices and feeder or bus.
RFCT(12.5 Ohm)
on surge capacitor
ground
0.8 – 0.2 Same as above.
RTD 0.3 – 0.05 Depends upon machine design and
less upon leads length.
Another issue that further promotes the need for sensor
normalization, or calibration, is the increasing flow of practical datacollected by different vendors. For instance, the author of [5]
reported the analysis of over 13,000 test samples. This data is not
very useful for other users since normalization to conventional
measurement units was not done. The above clearly indicates the
need to establish a field calibration procedure to allow for the future
advancement of the benefits of the varying PD technologies
available today. Without such flexibility, the end user is limited to
possibly outdated technology, and will not be able to benefit from
advancements in the future.
Calibration Procedure and UnitsThe approach described below is offered as a possible and useful
solution to the development of an acceptable field calibration
procedure for various PD sensors.
It is well known that the partial discharge transient wave, which is
detected by a PD sensor, experiences very high attenuation and
shape modification while travelling through the stator winding. This
causes a difference in the response of a sensor to a signal originating
in different points in the winding and therefore, becomes the main
problem complicating sensor calibration. The ideal solution is in
calibration of every sensor to all possible PD locations. This
approach is impractical due to the extreme complexity and unknown
PD source location during on-line testing. Two terms are proposed
to establish a uniform calibration standard, and provide a basis for
consistent calibration between various PD sensors and sensing
technologies.
Sensiti vity to PD at Sensor Location (Sensitivi ty) - we can calibrate
a sensor by injecting a known charge close to a sensor and
determining its sensitivity in terms of nC/Volt. Such sensitivity
applies primarily for partial discharges originating close to a sensor.
Signal attenuation is not taken into consideration in this factor. On
the other hand, attenuation is a very important factor for PD signals
distant to a sensor. Therefore, if sensitivity defined as it is described
above is used, data obtained on-line from a sensor in terms of nano-
Coulombs presents the lower limit estimation of an apparent charge
for discharges originating close to a sensor. In other words, a
discharge value can be greater for PD near the sensor, but it can not
be less. In spite of the approximate character of this approach, it is
still more accurate than millivolts alone. It creates the opportunity to
compare data taken from different sensors, taken from different
machines and even for machines of different rated voltages. All of
the above is true, to the same extent of approximation, for all
quantities which can be derived from “raw” PD data. These
quantities could be PD power or PD current and so on. Thequestion left without an answer is the applicability of such
approximation or, in other words where is the limit, beyond which a
comparison looses any practical sense? The answer to this question
is in the term described below and called the “Zone of Sensor
Sensitivity”.
Zone of Sensor Sensit ivi ty - This term is more qualitative than
quantitative. It limits the boundaries of a spatial zone that can be
assessed using a particular sensor. We use 20dB attenuation of a
signal as the criterion to determine the border of the Zone of Sensor
Sensitivity. One can not evaluate PD data reliably beyond that zone
of a particular sensor. From the example given above, we can
evaluate the line terminal insulation condition based on the 80 pF
capacitor readings, but we can not seriously discuss the winding
condition due to the inability of the line terminal PD sensors to
detect winding related PD signals. Any conclusions beyond the
Zone of Sensor Sensitivity would be just a guess based on previous
experience on similar machines with similar operating conditions,
but not on the real data. The knowledge obtained based on the Zone
of Sensor Sensitivity, for various PD sensor technologies, allows for
better planning concerning the number and location of sensors for a
particular application and provides a check on the reliability of the
information obtained. The Zone of Sensor Sensitivity can be
determined during off-line calibration.
We calibrate the PD measuring circuit in terms of apparent charge
using the procedure similar to that described in ASTM D1868 or
IEC 270 Standards. Therefore, we inject a known charge through a
differentiating (dosing) capacitor into a known point and record theresponse of all sensors in Volts. Consequently, sensitivity of a
sensor in terms of nano-Coulomb per Volt for a particular injection
point can be calculated. Zone of Sensor Sensitivity can also be
determined. Figure 5 presents the example of the calibrating circuit
for a radio frequency current transformer placed on the surge
capacitor-grounding conductor on a motor. The same circuit is used
to calibrate any type of PD sensor. Aluminum foil is wrapped
around the accessible part of the winding or the bus bar near the
calibrated sensor. The foil capacitance to the HV conductor is
commonly in the order of several hundreds to one thousand of pico-
Farads. This exceeds the capacitance of the dosing capacitor by
about 10 times. This capacitance is connected in series with the
dosing capacitor. As a consequence, the dosing capacitor limits the
injected charge. Therefore, an injected charge can be calculated as
the product of pulse magnitude and the dosing capacitance. A small
RFCT is additionally inserted into the charge injecting circuit and
measures injected current. This is an additional method to obtain an
injected charge. An injected charge is calculated as the area under
the oscillogram of the injected current. The first peak of the
oscillogram is used for injected charge calculation. In all cases, we
have had within 20% agreement between the injected charges
measured in both ways. This proves that either of the two methods
can be used.
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Response from all available sensors is measured for every point of
pulse injection. Therefore, cross-coupling coefficients between
different sensors can additionally be determined while obtaining the
sensitivity of any particular sensor. In order to detect the Zone of
Sensor Sensitivity, a pulse is injected into different points distant
from a calibrated sensor and a distance resulting in 20dB attenuation
is determined. Figures 6 “a” and “b” show photographs of the in-
field calibration on a 800MW 2-pole generator.
Figure 5. Calibration Circuit.
Figure 6a. Pulse Injection into the Endwinding Area.
Figure 6b. Pulse Injection into Line Terminals Area.
Sample Calibration ResultsThe results of calibration on small generator and two HV motors are
presented below.
12.5 MW, 13.8 kV Generator
This 42-slot generator is equipped with 12 RTDs distributed evenly
around the circumference of the stator core. Two RTDs are placed in
a slot, one on the exciter and another on the turbine end. RTDs 1-6
are placed on the exciter end and RTDs 7-12 are placed on the
turbine one. Therefore, 6 slots are equipped with a RTD. The
distance between the two nearest slots containing a RTD is 6 slots.
Fourteen signals were recorded simultaneously for every injection
point
• 12 RTDs were connected to the instrument through our
specially designed RFVS sensors and PD analyzer’s signal
conditioning module;
• T1 line terminal was connected to the instrument through a
1,000pF, 20kV coupling capacitor sensor and our PD
analyzer’s signal conditioning module;
• RFCT measuring injected current was loaded with 50 Ohms at
the oscilloscope end.
Figure 7 shows the RTD response in terms of Volts per nano-
Coulomb for pulse injection into four different points. Three of them
are related to slots containing RTDs and one to the Slot 22, which is
between RTD9 and RTD10. The other two related to RTDs were
placed in the Slot 18, which is at RTD # 10, and Slot 25, which is at
RTD # 9. All three RTDs showed approximately the same
sensitivity. The response drops by about 10 times if the pulse is
injected 3 slots away from the RTD. The attenuation of a signal
along a slot is about 5 times.
Figure 8 presents the coupling capacitor response to a PD injection
into different slots on both the exciter and the turbine ends. The
response drops very rapidly while moving the injection point away
from the line Slot 18. At the same time, this sensor is insensitive toany pulse injected at the turbine end.
Both Figures 7 and 8 indicate that a different level of criteria is
required for evaluation of PD located internal to the winding versus
at the line terminals. To detect PD near a winding RTD, using the
RTD as the PD sensor, a sensitivity of ~ 0.06V/nC would be applied
whereas PD occurring at the line terminals is detected with a
sensitivity of ~ 1V/nC. Using only a line-terminal PD sensor would
mask the low level of internal PD, which is detectable using the
RTD. For example, equal partial discharges at the line terminals
versus internal to the winding near an RTD would yield a
measurement of 1 volt for the PD at the line terminal and less than
0.1V for the same magnitude of PD internal to the winding. Such a
wide range of voltage measurements, at the line terminal, makes it
almost impossible to detect partial discharges internal to the winding
using only line-terminal PD sensors. With separate measurementsobtained using RTD’s, these internal partial discharges can now be
detected using the sensitivity of ~ 06V/nC; therefore a measurement
of 0.1 Volts at the RTD can be properly evaluated without the
masking of higher voltage measurements associated with having
only the line terminal type of PD sensor.
RFCT and Dosing
Capacitor
Aluminum FoilAluminum Foil
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Sensors Response to Injected Charge
0
0.02
0.04
0.06
0.08
0.1
0.12
RTD1 RTD2 RTD3 RTD4 RTD5 RTD6 RTD7 RTD8 RTD9 RTD10 RTD11 RTD12
Sensor Name
S e
n s i t i v i t y [ V / n C l ]
Sl18 RTD10_Tr Sl22_Tr Sl25 RTD9_Tr Sl32 RTD8_Tr
Figure 7. RTD Response to Injected Pulse
Coupling Capacitor Response to Injected Charge
0
0.5
1
1.5
2
2.5
T1 Line Sl18 Sl20 Sl25 Sl29 Sl32 Sl18 Sl22 Sl25 Sl32
Injection Point
S e n s i t i v i t y [ V / n C ]
Figure 8. Coupling Capacitor Response to Injected Pulse.
7550 HP 13.2 kV Synchronous Motor
The motor has 72 slots and is equipped with 12 RTDs placed at the
ring bus side of a slot. RTDs are distributed evenly along the
winding, every six slots. The sensitivity of different RTDs variesfrom 0.05V/nC to 0.07V/nC with an average value of 0.06V/nC.
RTDs located at a greater distance from the RTD terminals showed
sligthly less sensitivity, possibly related to the RTD wire routing..
The signal attenuation from the opposite end was very stable for all
RTDs and varies from 4.5 to 5.3 times.
8000 HP 13.2 kV I nduction M otor
This 4 pole motor has 96 slots and is equipped with 12 RTDs. Two
RTDs are located in the same slot approximately in the center of the
core. Six slots in total are equipped with RTDs. Wires from both
RTDs placed in the same slot come out of the slot in opposite
directions. This motor has a large diameter and a relatively short
core of about 1.5 m. In spite of the short core and approximately
centrally located RTD, they show 6 – 7 times better response to pulses injected from the side of the RTD wires.. A wire works as a
RF antenna as well and therefore the effective length of antenna is
greater for a pulse injected from a RTD wire side of the core. The
motor also showed moderate scatter in RTD sensitivity for different
RTDs. It varies from 0.2 to 0.28 Volt per nano-Coulomb, which is
about +15 to 20%. RTDs located closer to the RTD terminals at the
motor showed higher sensitivity. Higher signal attenuation as a
result of longer wires is the most probable reason for the observed
scatter. The effect of signal attenuation from the RTD to the RTD
terminals is most significant for RTD wires protected by a spiral
steel shield. Sensitivity for such RTDs is commonly in the range
from 0.015 to 0.02 Volt per nano-Coulomb.
The above results of RTD calibration confirm that RTDs can be
used as PD detectors in PD technologies based on high frequency
pulse recording.
The difference in sensitivity between different machines may behigh, therefore, a calibration is recommended for quantitative
comparison between different machines or between sensors of
different design. Note that relative comparison over time or between
machines of the same design is not a problem without any
calibration. Several examples of PD tests using RTDs presented
below also confirm that RTDs are a very valuable tool in PD
technology.
Off-line Test
This off-line test was performed on a 12.5MW, 13.8 kV generator
described above. Test voltage of 8 kV (phase to ground rated
voltage) was applied to one phase at a time. The other two phaseswere grounded. PD data was collected in the form of traditional
phase-resolved PD distribution with phase resolution of 2 degrees
and magnitude resolution of 0.5dB by Cutler-Hammer “Twins” PD
analyzer [6]. The sensitivities obtained from the calibration for
RTD’s and the 1,000pF coupling capacitor were used when
processing PD data. The flat projection of the Phase-Resolved PD
Distribution (PRPDD) on the phase-magnitude plane (top view)
obtained during “B” phase test is presented on Figure 9.
Figure 10 shows integral quantities calculated for data taken from all
of the PD sensors in three subsequent tests. In spite of significant
difference in signal magnitude (in terms of millivolts) obtained from
sensors of different types (Fig. 9), one can see the reasonable scatter
in integral quantities calculated from the coupling capacitor and
RTD data using the sensitivity of the sensor.
Figure 9. Phase B PD data.
Exciter End Turbine End
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Phase 1 Phase 2 Phase 3
Figure 10. Charts show PD Intensity, Maximum Apparent
Charge and Pulse Repetition Rate Respectively.(All Calculated from PD data above 0.1 nC.)
On-line Test
This on-line test was performed on a 7500 HP 13.8 kV motor. Themotor is equipped with three permanent radio-frequency current
transformers (RFCT) placed on the surge capacitor grounding
conductor in the motor terminal box and with 6 RTDs embedded
into the winding. RTD 1 & 4, RTD 2 & 5 and RTD 3 & 6 are
installed on the phases A, B and C respectively. RFVS sensors were
used to obtain temporary connections to RTD terminals in the RTD
connection box on the motor frame.
The flat projection of PRPDD from all available sensors is presented
on Figure 11, and maximum apparent charge is on Figure 12. It is
very important to mention that data presented for each sensor is
unique for a particular sensor. Any possible crosscoupling from
sensor to sensor was rejected by the “Twins” analyzer. As one can
see, both magnitudes from the RFCT and RTD are in approximately
Figure 11. Phase-Resolved PD data.
the same magnitude range and C-phase showed higher PD activity at
the line terminals as well as inside the winding. This is evident by
correlating the Maximum Apparent Charge for Phase C, shown in
Figure 12, with the higher Maximum Apparent Charges also shown
for RTD #3 and #6, both of which are installed at Phase C. This is
also visually evident by reviewing the PRPDD of Figure 11 below.
Phase C (CC_C) indicates more PD activity, and this is also evident
for RTD 3 and RTD 6 below.
Figure 12. Maximum Apparent Charge.
Conclusions
1. The attenuation of high frequency signals in rotating machine
windings is the main factor which complicates PD
measurements on such equipment. Sensors commonly placed
near machine line terminals are insensitive, as a rule, to distantPD originated internal to the machine winding. Additional
sensors placed in the winding are required to reliably detect
partial discharges. Resistive Temperature Detectors (RTDs)
already placed in a winding by the machine manufacturer can
be used as high frequency antennas to collect partial discharge
pulses from the depth of the winding. The use of RTDs allows
PD data to be obtained without an outage to install invasive
sensors into winding slots.
2. RTDs commonly have good sensitivity to PD originating
nearby. Therefore, if used complimentary to conventional PD
detectors, these provide better information on partial discharges
in the entire stator winding and yield a more reliable winding
insulation assessment.
3. Calibration is recommended to scale PD data taken from RTDs,
and other types of PD sensors, of different machines, to the
same base. This calibration correlates the characteristics of the
various PD sensors which may have different characteristics for
high frequency applications. Such calibration would also
correlate different responses from similar RTD’s, or other PD
sensors, to the same discharge on machines of different
designs. Note that relative comparison over time or between
machines of the same design is not a problem without any
calibration. In this case, the use of RTD’s can be trended,
similar to sensors which would require an outage for invasive
installation.
4. The calibration procedure was designed with the aim to scalesensors of different design to the same basis. Two terms
“Sensiti vity to PD at Sensor location” and “Zone of Sensor
Sensitivity ” is suggested to perform sensor calibration in terms
of apparent charge.
5. Over two years of practical experience confirms that RTDs can
be used as a very valuable tool for on-line and off-line PD
measurements on a rotating machine (with an adequate PD
analyzer that can process data and efficiently reject all types of
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noise). The key advantage is that the use of PD predictive
technologies can be easily implemented with existing RTDs.
References
1. Draft of the IEEE P1434 “Guide to Measurement of Partial
Discharges in Rotating Machinery, 1998.
2. K. Itoh, Y. Kaneda, S. Kitamura et al. “New Noise RejectionTechnique on Pulse-by-Pulse Basis for On-Line Partial
Discharge Measurements of Turbine Generators”, IEEE PES
Paper # 96WM 154-5-EC
3. Osman M. Nassar, Thani S. Al-Anizi. “Saudi Aramoco
experience with partial discharge on-line motor monitoring
equipment”, IRIS Rotating Machine Technical Conference,
March 10-13, 1998, Dallas, TX USA.
4. I. Blokhintsev, M. Golovkov, A. Golubev, C. Kane “Field
Experiences on the Measurement of Partial Discharges on
Rotating Equipment”, IEEE PES’98, February 1-5, Tampa, FL
5. V. Warren “On-Line Partial Discharge Monitoring: Where do
We Stand and What Next?” EPRI Utility Generator and
Predictive Maintenance & Refurbishment Conference,
December 1-3, 1998, Phoenix, Arizona.
6. Z. Berler, A. Golubev, A. Romashkov, I. Blokhintsev “A New
Method of Partial Discharge Measurements”, CEIDP-98
Conference, Atlanta, GA, October 25-28, 1998.