STANDARD. Third edition. High-voltage test techniques –. Partial discharge measurements. This English-language version is derived from the. voltage testing techniques, was submitted to the IEC-CENELEC parallel vote and was The text of the International Standard IEC was approved by. between conductors and which can or can not occur adjacent to a conductor. - IEC High-voltage test techniques – Partial discharge measurements.
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A general correlation between the measurement according to IEC standard and measurements in the UHF range is not possible. By the use of a. 3 days ago PDF | Defect classification using partial discharge (PD) measurement has Around RF and IEC PD pulses have been recorded. Partial Discharge IEC - Download as PDF File .pdf), Text File .txt) or read online.
IEC [High-voltage test techniques Partial discharge measurements, third edition], published in December , covers besides classical analogue instruments also requirements for digital measuring systems.
Moreover, the maintaining of specific characteristics of PD measuring systems by the user in a record of performance is recommended. In this context it should be noted that currently the new standard IEC is under preparation, which covers non-conventional electromagnetic and acoustical PD detection methods. These topics, however, are outside of the scope of this brochure.
Partial discharges are defined in IEC as: localized electrical discharges that only partially bridges the insulation between conductors and which can or cannot occur adjacent to a conductor. Partial discharges are in general a consequence of local electrical stress concentrations in the insulation or on the surface of the insulation.
Generally, such discharges appear as pulses having a duration of much less than 1 s. From a physical point of view self-sustaining electron avalanches may happen only in gaseous dielectrics. Consequently, typical discharge types occurring in ambient air, such as glow, streamer and leader discharges, may also happen in gaseous inclusions due to imperfections in solid and liquid dielectrics. The pulse charge of glow discharges is in the order of few pC. Streamer discharges may create pulse charges ranging from about No.
A transition from streamer to leader discharges may occur if the pulse charge exceeds few pC.
High-voltage test techniques - Partial discharge measurements
Original PD current pulses are characterized by a duration as short as few ns, as exemplarily shown in Fig. The shape of such pulses, however, is strongly distorted if traveling from the PD site to the terminals of the test object. Different to this behavior the current-time integral is more or less invariant.
As a consequence, not the peak value of the PD current pulses but the current-time integral, i. Here the high voltage bushing capacitance C1 represents in principle the coupling capacitor Ck.
The measuring impedance Zm is connected to the tap of a capacitive graded bushing, usually intended for loss factor measurements. External electromagnetic noises disturbing sensitive PD measurements can be eliminated at certain extend if a balanced bridge is employed. Partial discharges on electrical PD measurement associated with the PD are in general a consequence of local electrical stress con- quantity apparent charge, which is expressed in terms centrations in the insulation or on the surface of the insu- of pC.
IEC From a physical point of view self-sustaining elec- [High-voltage test techniques — Partial discharge mea- tron avalanches may happen only in gaseous dielectrics. Moreover, also happen in gaseous inclusions due to imperfections the maintaining of specific characteristics of PD mea- in solid and liquid dielectrics.
The pulse charge of glow suring systems by the user in a record of performance discharges is in the order of few pC. Streamer discharges is recommended. A transition from streamer to tap coupling mode which is generally utilized for induced WG leader discharges may occur if the pulse charge exceeds voltage tests of liquid-immersed power transformers.
Here the high voltage bushing capacitance C1 represents in principle the coupling capacitor Ck.
The measuring Original PD current pulses are characterized by a dura- impedance Zm is connected to the tap of a capacitive tion as short as few ns, as exemplarily shown in Fig. Con- graded bushing, usually intended for loss factor mea- sequently, the frequency spectrum covers the VHF and surements.
The shape of such pulses, however, is strongly distorted if traveling from the PD site to the terminals of External electromagnetic noises disturbing sensitive the test object. Different to this behavior the current-time PD measurements can be eliminated at certain extend if integral is more or less invariant. As a consequence, not the a balanced bridge is employed. These antennas can be classified as internal invasive or external non-invasive sensors, according to whether they are mounted inside or outside the HV equipment.
UHF sensors are normally coupled in the resonant metallic chambers of GIS compartments [ 24 ], power transformers [ 2 ], and metal-enclosed switchgears [ 18 ]; in addition they are also coupled in cable accessories [ 15 ] and rotating machines [ 25 ]. In the research presented in this paper, the two non-conventional approaches introduced previously have been considered for their implementation in on-line PD measuring or monitoring applications for MV switchgears.
The measuring method that operates in HF with HFCT sensors enables autonomous evaluation of the insulation condition, not only of the switchgears to be controlled but also of the installation where these switchgears are in operation. This solution is of interest when a general oversight of the facility is pretended. However, in order to discriminate if a detected defect is within a specific switchgear, further assisted analysis is required. The advantages of applying this method are as follows: High sensitivity is obtained when the sensors are located close to the PD source and when they are hundreds of meters from it.
Hence, as mentioned before, with this method a high field of vision is achieved and use of a few measuring units positioned in strategic points in a MV installation is sufficient for its supervision. If two or more HFCT sensors are placed in a MV or HV installation, the measurement of the PD pulses with a common time reference allows the location of the defects by the time-of-flight analysis. When a HFCT sensor is installed in the earth connection of a cable terminal connected to a certain asset e.
The measuring method that operates in UHF implementing antennas as sensors is focused on the autonomous supervision of the insulation condition of the elements integrated in the proper individual switchgears including the cable terminations connected to them but not in the rest of the electrical installation where these assets are operating.
This solution is of interest for PD detection in switchgears that function in critical MV installations such as, for example, in those that provide electrical energy to major electrical consumers, hospitals, airports, metallurgical industries, etc.
The advantages of applying this method are as follows: High immunity to electric noise interferences and corona discharges in air, since the frequency spectrum of these signals in the UHF range is very low and in some emplacements negligible.
Partial Discharge IEC 60270
High sensitivity in PD detection inside the metal enclosed switchgears due to the inner electrical resonance and low-inherent losses. Possibility of assuring that when an insulation defect is detected with an antenna placed in a switchgear, this defect is confined inside this switchgear including the cable terminations connected to it. In the research presented in this paper, a measuring method that operates in UHF measuring with antennas and another that operates in HF using HFCT sensors are proposed for their characterization and evaluation.
In addition, the study has been completed with the realization of measurements by applying the conventional method according to IEC standard.
This last method was implemented in order to provide reference measurements for comparative purposes.Paulina Elena Voicu. A logic system performs the comparison and operates the gate of the instrument, as described above, for pulses of the correct polarity.
IEC The contents of the corrigendum of October have been included in this copy. Measuring Methods, Sensors, and Measurement Devices 2. Common-mode signals will be detected as having equal polarities; partial discharge signals from either component will be detected as having opposite polarities.
One disadvantage of this method is, however, that the RIV level is weighted according to the acoustical noise impression of the human ear, which is not correlated to the PD activity. Performance tests shall be performed periodically or after any major repair, and at least every five years.