Buy IEC HIGH VOLTAGE TEST TECHNIQUES – PARTIAL DISCHARGE MEASUREMENTS from SAI Global. Buy IEC Ed. High-voltage test techniques – Partial discharge measurements from SAI Global. Partial Discharge measurement setup a) IEC PD measuring device This device consists of a coupling capacitor (C k), measuring impedance and the.
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Guide for electrical Partial Discharge Measurements in compliance to IEC 60270
In this context it should be noted that cur- mission of electrical power. Since that time numerous rently the new standard IEC is under preparation, papers and books appeared, dealing with the physics which covers non-conventional electromagnetic and and recognition of partial discharges.
First industrial acoustical PD detection methods. These topics, however, PD tests of HV apparatus were introduced at the are outside of the scope of this eic. One disadvantage of this method is, however, that the RIV level is weighted according to the acoustical noise Partial discharges are defined in IEC as: 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 62070 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 irc 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. Here both, the measur- peak value of the PD current pulses but the current-time ing and the reference branch, consist of a coupling unit integral, i. Balancing the bridge by adjusting able quantity for assessment the PD intensity. To ensure reproducible iev comparable PD mea- surements in IEC three basic measuring circuits are recommended, which differ by the arrangement of The standard IEC recommends besides the the measuring impedance Zm.
The most common cir- measurement of the apparent charge an evaluation of cuit employed in practice is shown in Fig. An and extinction voltage, as well as the pulse repetition rate, option of the PD coupling unit is the so-called bushing the pulse repetition frequency, the phase angle, the aver- age discharge current, the discharge power and the quadratic rate. All these quantities, however, are either derived from or related to the appar- ent charge, which can thus be considered as the most important PD quantity to be evaluated.
For measuring the apparent charge conven- tional analogue PD instruments are equipped with a band-pass filter amplifier followed by a peak level indicator.
As isc as the band-pass filter extracts the measuring frequency in a range where the spectral density of the PD Fig. Most common PD measuring circuit employed in practice Fig.
Positive and negative PD current pulses of a cavity discharge in XLPE recorded for an inverted point-to-plane electrode arrangement No. Another option for measuring the apparent charge The main feature iiec a digital PD measuring system is a very wide-band pre-amplification of the PD signal is the ability to store the following characteristic param- captured from the test object followed by an electronic eters of each PD event: This principle offers several advantages not only for the reduction of electromagnetic interferences, ti — instant time of 6270 occurrence but also for the location of PD faults in long power cables.
A bloc diagram for a computerized PD visualization of phase-resolved PD patterns. This ensures measuring system is shown in Fig. Here the digitaliza- the evaluation of all PD quantities recommended ied IEC as well as an in-depth statistical anal- ysis of the very complex PD occurrence.
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More- over, a PD pulse waveform analysis can be per- formed capable for the location of the PD site in power cables as well as for the recognition of different PD sources and also for the de- noising of PD signals. The quantitative assessment of the appar- Fig.
Principle of the quasi-integration of PD pulses ent charge transferred from the PD source to the terminals of the test object is based on the approach of Gemant and Philippoff, often referred to as a — b — c model due to the char- acteristic capacitances Ca — Cb — Cc, as illus- trated in Fig.
Rectangular pulse response of an electronic integrator satisfied, the apparent charge qa detectable at the test object terminals can be written as: Bloc diagram of an idc digital PD measuring system apparent charge alone, because the No. Therefore, knowledge rules for PD diagnosis have been established in the past which are based on practical experiences gained from comprehensive PD studies in laboratory and on-site. For maintaining the characteristics of PD measur- Each PD event causes a reading Ri of the PD instru- ing systems the following procedures are recommended ment which is proportional to qa.
To measure this quan- in IEC This means of an external adapted calibrator, as evident from should be performed prior each PD test. This should be circuit, would give the same reading on the measuring performed at least once a year or after major repair.
IS/IEC 60270: High – Voltage Test Techniques – Partial Discharge Measurements
Independent from such guide- generator connected in series with a 6020 capaci- lines IEC recommends additional test procedures, tor. In order to simulate the transient voltage across the where the results shall be maintained by the user in a “Record PD defect the pulse generator creates equidistant volt- of Performance”. This shall include the nominal character- age steps of known magnitudes U0. Per- formance tests shall be performed periodically or after If real PD events appear, the apparent charge is 60720 any major repair, and at least every five years.
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