電力變壓器的局部放電及測量課件

1、Review of Lecture 71. Partial Discharge in Power Capacitors2. Parameters and Standard3. Electrical Detection of PD in CapacitorContents: Parameters to estimate the PD of capacitor Apparent charge, qInception voltage, UiExtinction voltage, UeChange of q with voltage applying time1Power SourceCompensa

2、tion reactor is used in series or parallel with Cx so that to decrease the capacity of testing transformerReview of Lecture 7Currents through L and C while the two elements connected in parallelVoltages across L and C while the two elements connected in series2Review of Lecture 7Detection circuits S

3、traight detection circuitsBalanced detection circuit3Review of Lecture 7Some problems need to be noticedDetection impedances is required to withstand large current.Several detection impedances are needed to match the capacitor samplesConnection types of capacitor elements influence detection results

4、.4Lecture 8 PD Detection in Power Transformers電力變壓器的局部放電及測量5Contents1. Significance of PD detection in Transformer電力變壓器測量局放的重要性2. PD Propagation in Windings4. Detection Circuits for Transformers5. Calibration6. The Influence of Discharges in Bushing3. Test Procedure and Permissible Apparent Charge7.

5、 Electrical Location of PD in Transformers局部放電在繞組中的傳播測試程序和允許放電水平變壓器局部放電的測試回路校正套管放電的影響變壓器局部放電的電氣定位方法61. Significance of PD Detection in Transformerpower frequency withstand test impulse withstand test PD often affects the transformers properties in a long-term period. The withstand strength in a shor

6、t time does not change significantly. Withstand test is destructive, the voltage is so high that insulation is easy to be damaged.工頻耐壓試驗沖擊耐壓試驗局部放電通常影響變壓器的長期運行性能，而對短時的耐壓強度影響不大。耐壓試驗是有損試驗，容易對絕緣造成破壞The voltage of PD test is much lower, and the testing duration is longer (0.51h).局部放電試驗的試驗電壓相對較低，試驗持續(xù)時間也較長

7、72. PD Propagation in WindingsEquivalent circuit of a transformer windingC-ground capacitance per unit lengthL-inductance per unit length, parasitic inductance K-series capacitance per unit length, longitudinal capacitance O-neutral point A-high voltage end單位長度對地電容單位長度的串聯(lián)電容 單位長度的電感，即寄生電感 中性點高壓端8Equi

8、valent circuit of a winding with a cavity discharge source2. PD Propagation in Windings92. PD Propagation in WindingsVoltage response along the winding沿繞組的電壓響應(yīng)103. Test Procedure and Permissible Apparent ChargeU1:pre-applied Voltage 預加電壓U2:measuring voltage 測量電壓Um :the maximum line voltageDuring obs

9、ervation, some impulses occasionally occurring with high magnitude can be neglected.在整個試驗時間內(nèi)連續(xù)觀測，個別較高的脈沖可以忽略The noise level is required to be less than 50% magnitude of the highest detected impulse.外圍噪聲水平應(yīng)低于規(guī)定的視在放電量的50%When test voltage is raised to U2 and decreased from U2, the inception and extinc

10、tion voltages are recorded.在電壓升至U2及由U2降低的過程中，記錄起始可能的放電電壓和熄滅電壓113. Test Procedure and Permissible Apparent ChargeDuring the first step under the test voltage U2, the maximum apparent charge is recorded.During the second step under the test voltage U2, discharge impulses need to be observed continuous

11、ly and the maximum apparent charge is recorded.U1:pre-applied Voltage 預加電壓U2:measuring voltage 測量電壓Um :the maximum line voltage在電壓U2的第一階段應(yīng)讀數(shù)并記錄No record is required under test voltage U1.在U1階段無需觀測記錄在電壓U2第二階段整個時間內(nèi)，應(yīng)連續(xù)地觀測和記錄局部放電水平12 If the following results are obtained, the PD experiment can be passe

12、d.3. Test Procedure and Permissible Apparent ChargeDuring the test procedure, the test voltage never suddenly decreases.During the last 30 minutes, the magnitudes of all observed impulses are smaller than the permissible apparent charge and do not increase towards the permissible apparent charge.如果滿

13、足兩個條件，則試驗合格試驗過程中，試驗電壓不產(chǎn)生突然下降在施加電壓U2的第二階段的30分鐘內(nèi)，所有測量的視在放電量連續(xù)維持在低于規(guī)定的限值，并且不表現(xiàn)出明顯地、不斷地傾向允許最大限制值增長的趨勢134. Detection Circuits for TransformersTwo ways of the test：induced voltage test and applied voltage test.Principles of PD circuit selection 兩種試驗方法：感應(yīng)加壓方式，直接加壓方式 試驗回路選擇采用盡量短的引線在試驗中對主縱絕緣都能同時得到所應(yīng)施加的電壓To e

14、xecute the test with required voltage on both main insulation and longitudinal insulation.To use high voltage leads as short as possible.144.1 Detection circuits for single-phase transformers4. Detection Circuits for Transformers(a)(b)(c)(d)單相變壓器的測試回路applied voltageinduced voltage154.2 Detection Cir

15、cuits for Three-Phase Transformers4. Detection Circuits for TransformersUA=0.25U, UB=0.75U, UC=UUBC=1.75U,UAC=1.25UUA=0.5U, UB=U, UC=0.5UUAB=1.5U,UBC=1.5U三相變壓器的測試回路164. Detection Circuits for TransformersUA=0.5U, UB=0.5U, UC=UUAC=1.5U,UBC=1.5UUA=0.5U, UB=0.5U, UC=UUAC=1.5U,UBC=1.5U175. CalibrationCo

16、0.1CxCx: entrance capacitance 入口電容Co：50100pFCalibration impulse injected from the HV terminalCalibration impulse injected from the measuring terminal高壓端校正入口校正Ck: capacitance of bushing 套管電容185. CalibrationExecute calibration at the place close to the detection terminal.Requirements of calibration:Put calibration unit as close as possible to the HV terminal in order to avoid influences of parasitic capacitances.Record the detected apparent charges and the relevant detection and calibration places.在測量部位和