ASTM D3382-22

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
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Designation: D3382 − 13 D3382 − 22
Standard Test Methods for
Measurement of Energy and Integrated Charge Transfer Due
to Partial Discharges (Corona) Using Bridge Techniques
This standard is issued under the fixed designation D3382; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 These test methods cover two bridge techniques for measuring the energy and integrated charge of pulse and pseudoglow
partial discharges:
1.2 Test Method A makes use of capacitance and loss characteristics such as measured by the transformer ratio-arm bridge or the
high-voltage Schering bridge (Test Methods D150). Test Method A can be used has been found useful to obtain the integrated
charge transfer and energy loss due to partial discharges in a dielectric from the measured increase in capacitance and tan δ with
voltage. (See also IEEE 286 and IEEE 1434)
1.3 Test Method B makes use of a somewhat different bridge circuit, identified as a charge-voltage-trace (parallelogram)
technique, which indicates directly on an oscilloscope the integrated charge transfer and the magnitude of the energy loss due to
partial discharges.
1.4 Both test methods are intended to supplement the measurement and detection of pulse-type partial discharges as covered by
Test Method D1868, by measuring the sum of both pulse and pseudoglow discharges per cycle in terms of their charge and energy.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific precaution statements are given in Section 7.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D150 Test Methods for AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulation
D1711 Terminology Relating to Electrical Insulation
D1868 Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
These test methods are under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and are the direct responsibility of Subcommittee
D09.12 on Electrical Tests.
Current edition approved Nov. 1, 2013Jan. 1, 2022. Published December 2013February 2022. Originally approved in 1975. Last previous edition approved in 20072013
as D3382 – 07.D3382 – 13. DOI: 10.1520/D3382-13.10.1520/D3382-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
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D3382 − 22
2.2 IEEE Documents
IEEE 286 Recommended Practice for Measurement of Power Factor and Power Factor Tip-up for Rotating Machine Stator Coil
Insulation
IEEE 1434 Guide to the Measurement of Partial Discharges in Rotating Machinery
IEEE C57.113 Guide for PD Measurements in Liquid-Filled Power Transformers
IEEE Standard C57.124 Recommended Practice for the Detection of PD and the Measurement of Apparent Charge in Dry-Type
Transformers
2.3 AEIC Documents
AEIC T-24-380 Guide for Partial Discharge Procedure
AEIC CS5-87 Specifications for Thermoplastic and Crosslinked Polyethylene Insulated Shielded Power Cables Rated 5 through
35 kV, 9th Edition, 1987
3. Terminology
3.1 Definitions:
3.1.1 pseudoglow discharge, n—a type of partial discharge, which takes place within an expanded discharge channel and is
characterized by pulses of relatively low magnitude and long rise time.
3.1.1.1 Discussion—
Pseudoglow discharges occur within a diffused discharge channel, whose emitted glow fills the entire intervening gap or cavity
space (1). The discharge rate behavior as a function of applied voltage is similar to that of the rapid rise time pulse (spark-type)
discharges. The successive pseudoglow discharge pulses occur over the first quadrant of each half cycle and in some gases, notably
helium, their magnitude is found to diminish to zero. At this point, a transition to a pulseless glow discharge can occur. has been
observed. Its occurrence, which is manifest by distortion in the sinusoidal voltage wave, is rare. At discharge inception of a single
cavity, the pattern of pseudoglow discharges consists of a single long rise time discharge current pulse in each half-cycle. It has
become common practice to refer to this particular type of pattern as that of a glow discharge.
Pseudoglow partial discharges, which occur at low gas pressures, such as in insulating systems of electrical equipment for
aerospace applications, have unduly long rise times and a frequency spectrum that falls bellow the bandwidth of conventional
partial discharge pulse detectors (2). As a consequence, they cannot be detected by the partial discharge detectors specified in Test
Method D1868; however they can be detected and measured by either Method are not suitable for this purpose; however Methods
A or B of Test Methods D3382. have been found suitable for use.
3.1.2 pulse discharge, n—a type of partial-discharge phenomenon characterized by a spark-type breakdown which occurs in a
narrow constricted channel.
3.1.2.1 Discussion—
The resultant detected pulse discharge has a short rise time and its Fourier frequency spectrum may has been observed at times
to extend as far as 1 GHz. Such a pulse discharge may behas been readily detected on occasion by conventional pulse detectors,
that are generally designed for partial-discharge measurements within the frequency band from 30 kHz to several megahertz. (See
also IEEE 1434, IEEE C57.113, IEEE C57.124, AEIC T-24-380, and AEIC CS5-87.)
3.1.3 pulseless-glow discharge, n—an uncommon type of partial discharge , whose existence is manifest not by the usual abrupt
voltage fall discontinuities in the sinusoidal voltage wave at each discharge epoch but rather by distortions in the waveform.
3.1.3.1 Discussion—
It is generally found that the pulseless glow region develops only when preceded by a pseudoglow discharge in which the abrupt
voltage collapse magnitudes at each discharge have gradually diminished in the limit to zero. The nature of this pulseless glow
region is not fully understood, but it is believed to consist of a very weakly ionized gas volume. Further increases in the applied
voltage can have been found to potentially lead to more complex partial discharge patterns, consisting of regions of pseudoglow,
pulseless and pulse type discharges (3). Pulse type partial discharge detectors of the type described in Test Method D1868 cannot
be employedare not suitable to detect pulseless glow discharges.
3.1.4 See (1) and (3) for more information on the previous definitions.
3.1.5 For definitions of other terms pertaining to this standard refer to Terminology D1711.
3.2 Symbols:
Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Available from The Association of Edison Illuminating Companies (AEIC), 600 N. 18th St, Birmingham, AL 35291, www.aeic.org.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
D3382 − 22
3.2.1 Refer to Annex A1 for symbols for mathematical terms used in this standard.
4. Summary of Test Methods
4.1 It is possible to represent the dielectric characteristics of a specimen of solid insulating material by a parallel combination of
capacitance and conductance. The values of capacitance and conductance remain practically constant over the useful range of
alternating voltage stress at a fixed frequency. If, however, the specimen contains gaseous inclusions (cavities), incremental
increases in capacitance and conductance occur as the voltage stress is raised above the value necessary to initiate partial discharges
in the cavities. The energy loss in the incremental conductance is considered to be that dissipated by the partial discharges.
4.2 In Test Method A an initial measurement is made of the capacitance and loss characteristic of the specimen at an applied
voltage below the discharge inception level. The voltage is then raised to the specified test value and a second measurement made.
The energy loss due to partial discharges is calculated from the results of the two measurements.
4.3 In Test Method B a special bridge circuit is balanced at a voltage below the discharge inception level. The voltage is then raised
to the specified test value, but the bridge is not rebalanced. Any unbalanced voltage at the detector terminals is displayed in
conjunction with the test voltage on an oscilloscope. The oscilloscope pattern approximates a parallelogram, the area of which is
a measure of the energy loss due to partial discharges.
5. Significance and Use
5.1 These test methods are useful in research and quality control for evaluating insulating materials and systems since they provide
for the measurement of charge transfer and energy loss due to partial discharges(4) (5) (6).
5.2 Pulse measurements of partial discharges indicate the magnitude of individual discharges. However, if there are numerous
discharges per cycle it is occasionally important to know their charge sum, since this sum can be is related to the total volume of
internal gas spaces that are discharging, if it is assumed that the gas cavities are simple capacitances in series with the capacitances
of the solid dielectrics (7) (8).
5.3 Internal (cavity-type) discharges are mainly of the pulse (spark-type) with rapid rise times or the pseudoglow-type with long
rise times, depending upon the discharge governing parameters existing within the cavity. If the rise times of the pseudoglow
discharges are too long , they will evade detection by pulse detectors as covered in Test Method D1868. However, both the
pseudoglow discharges irrespective of the length of their rise time as well as pulseless glow can be are readily measured either
by Method A or B of Test Methods D3382.
5.4 Pseudoglow discharges have been observed to occur in air, particularly when a partially conducting surface is involved. It is
possible that such partially conducting surfaces will develop with polymers that are exposed to partial discharges for sufficiently
long periods to accumulate acidic degradation products. Also in some applications, like turbogenerators, where a low molecular
weight gas such as hydrogen is used as a coolant, it is possible that pseudoglow discharges will develop.
6. Sources of Errors
6.1 Surface Discharges—All discharges in the test specimen are measured, whether on the surface or in internal cavities. If it is
desired to measure only internal cavities, the other discharges must be avoided. In the case of an insulated conductor with an outer
electrode on the surface (such as a cable or generator coil), it has been found useful to use a closely-spaced guard ring connected
to ground to remove the surface discharges at the end of this outer electrode can be removed from the measurement with a
closely-spaced guard ring connected to ground. from the measurement. See Section 4 of Test Methods D150.
6.2 Since tests will be made at ionizing voltage, all connections making up the complete high-voltage circuit shouldshall be free
of corona to avoid measurement interference. See Section 5 of Test Method D1868.
6.3 Anomalous changes in insulation losses with changes in voltage stress can have been observed to occur as a result of
phenomena other than partial discharges. Such losses are a source of error in these methods, since they are indistinguishable from
discharge losses. However, these losses are often negligible in comparison with partial discharge losses.
D3382 − 22
6.4 It is possible that any temperature change in the specimen between the times at which the low-voltage and high-voltage
measurements are taken will cause a change in the normal losses and appear as changes in discharge energy, thus causing an error
in test results. This situation can be is recognized inby Method B and corrective action taken (see 11.3).
6.5 Paint used to grade potential on the surface of some insulation specimens (for example, generator stator coil) shall not be
included in the measurement, since it is possible that the conductance of such paints will change with voltage and affect the
accuracy of the method as a measure of discharge energy. It is sometimes possible to exclude the painted surfaces from the
measuring circuit by the use of guarding or shielding techniques.
7. Hazards
7.1 Warning— It is possible that lethal voltages will be present during this test. It is essential that the test apparatus, and all
associated equipment potentially electrically connected to it, be properly designed and installed for safe operation. Solidly ground
all electrically conductive parts that any person might come in contact with during the test. Provide means for use at the
completion of any test to ground any parts which: were at high voltage during the test; have the potential to have acquired an
induced charge during the test; have the potential to retain a charge even after disconnection of the voltage source. Thoroughly
instruct all operators in the proper way to conduct tests safely. When making high voltage tests, particularly in compressed gas
or in oil, it is possible that the energy released at breakdown will be suffıcient to result in fire, explosion, or rupture of the test
chamber. Design of test equipment, test chambers, and test specimens shall be such as to minimize the possibility of such
occurrences and to eliminate the possibility of personal injury.
7.2 Warning— Ozone is a physiologically hazardous gas at elevated concentrations. The exposure limits are set by governmental
agencies and are usually based upon recommendations made by the American Conference of Governmental Industrial Hygienists.
Ozone is likely to be present whenever voltages exist which are sufficient to cause partial, or complete, discharges in air or other
atmospheres that contain oxygen. Ozone has a distinctive odor which is initially discernible at low concentrations but sustained
inhalation of ozone can cause temporary loss of sensitivity to the scent of ozone. Because of this it is important to measure the
concentration of ozone in the atmosphere, using commercially available monitoring devices, whenever the odor of ozone is
persistently present or when ozone generating conditions continue. Use appropriate means, such as exhaust vents, to reduce ozone
concentrations to acceptable levels in working areas.
TEST METHOD A
8. Procedure
8.1 Conventional circuits for the measurement of alternating-voltage capacitance and loss characteristics of insulation can be used
are appropriate for this method. The transformer-ratioarm bridge shown in Fig. 1, or the Schering bridge shown in Fig. X4.2 of
Test Methods D150 are well suited to this application.
8.2 Energize the test specimen at a low voltage, V , below the discharge-inception voltage, and measure capacitance C and
1 x1
dissipation factor tan δ . Raise the voltage to a specified test level, V , and repeat the measurements for C and tan δ . Calculate
1 2 x2 2
the power loss, ΔP, in watts due to discharges at voltage V as follows:
ΔP 5 ωV C tan δ 2 C tan δ (1)
~ !
2 x2 2 x1 1
2 2
5P 2 P V /V (2)
~ !
2 1 2 1
8.3 The increment of dissipation factor tan δ − tan δ , called delta tan delta, and written Δ tan δ, is often used as an index of
2 1
discharge intensity.
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D3382 − 22
FIG. 1 Typical Transformer-Ratio-Arm Bridge (Method A)
9. Precision and Bias
9.1 This test method has been in use for many years, but no statement for precision has been made and no activity is planned to
develop such a statement.
9.2 A statement of bias is not possible due to the lack of a standard reference material.
10. Interferences
10.1 Harmonics—The test voltage must be reasonably free of harmonics in order to produce the required horizontal line below
the inception voltage. Harmonics will produce a wavy rather than a flat line. If the waviness is too severe, the voltage source will
have to be filtered to remove the harmonics. The removal of harmonics is more important when the quantities to be measured are
small.
TEST METHOD B
11. Procedure
11.1 The test method requires the placing of the test specimen, considered essentially as a high-voltage capacitor, in series with
a low-voltage capacitor, across a sinusoidal test-voltage source. See Fig. 2. Two other bridge arms provide a voltage for balancing,
at an applied voltage level below inception of partial discharges, the sinusoidal voltage across the low-voltage capacitor. Any
partial discharges that occur at higher applied voltages in the specimen will be integrated by the low-voltage capacitor to produce
an unbalanced voltage. The unbalanced voltage controls the vertical deflection of an oscilloscope beam, while a voltage
proportional to, and in phase with the test voltage, controls the horizontal deflection. A description of a suitable circuit for this test
method is detailed in Annex A2.
11.2 The oscilloscope display is simply a horizontal line below the discharge inception voltage where no unbalanced voltages
occur. Above the discharge inception voltage the display opens into an approximate parallelogram. The height of the parallelogram
represents the sum of the partial discharges per half cycle, an
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