1、1Review of Lecture 71.Partial Discharge in Power Capacitors2.Parameters and Standard3.Electrical Detection of PD in CapacitorContents:Parameters to estimate the PD of capacitor lApparent charge,qlInception voltage,UilExtinction voltage,UelChange of q with voltage applying time2Power SourceCompensati
2、on reactor is used in series or parallel with Cx so that to decrease the capacity of testing transformerReview of Lecture 7 I LI cI e Lu Cu u e Currents through L and C while the two elements connected in parallelVoltages across L and C while the two elements connected in series3Review of Lecture 7D
3、etection circuits CxZdZmeCk=CxoACx2ZmeoACx1Zd1Zd2Straight detection circuitsBalanced detection circuit4Review of Lecture 7Some problems need to be noticeduDetection impedances is required to withstand large current.uSeveral detection impedances are needed to match the capacitor samplesuConnection ty
4、pes of capacitor elements influence detection results.xCxCxCxCdURdCdCkxUxCxCxCxCxUdURdCdCk)()1(111dkxdkkdkdddCCCnCCCCCCUUK5Lecture 8 PD Detection in Power Transformers电力变压器的局部放电及测量61.Significance of PD detection in Transformer2.PD Propagation in Windings4.Detection Circuits for Transformers5.Calibra
5、tion6.The Influence of Discharges in Bushing3.Test Procedure and Permissible Apparent Charge7.Electrical Location of PD in Transformers71.Significance of PD Detection in Transformerpower frequency withstand test impulse withstand test PD often affects the transformers properties in a long-term perio
6、d.The withstand strength in a short time does not change significantly.Withstand test is destructive,the voltage is so high that insulation is easy to be damaged.工频耐压试验冲击耐压试验局部放电通常影响变压器的长期运行性能，而对短时的耐压强度影响不大。耐压试验是有损试验，容易对绝缘造成破坏The voltage of PD test is much lower,and the testing duration is longer(0.
7、51h).局部放电试验的试验电压相对较低，试验持续时间也较长82.PD Propagation in Windings A O C K L Equivalent 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单位长度对
8、地电容单位长度的串联电容 单位长度的电感，即寄生电感 中性点高压端9Cb nC mC cC bC cu P O P A uc +cC bC Cdx dxk/dx du m n l ox x Equivalent circuit of a winding with a cavity discharge source)()(cosh)()(cosh0000lxxxlxtghxltghCKxlQumx)0(cosh)(cosh0000 xxxxtghxltghCKxQunxKC2.PD Propagation in Windings102.PD Propagation in Windings 0 p
9、u 0 x l x xu nVoltage response along the winding)(cosh)(000 xlxtghxltghckQul沿绕组的电压响应113.Test Procedure and Permissible Apparent Charge 30min 5s 5min U1 U2 mmUUU3/31U1:pre-applied Voltage 预加电压U2:measuring voltage 测量电压Um:the maximum line voltage3/5.12mUU pCq5003/3.12mUU pCq300oDuring observation,some
10、impulses occasionally occurring with high magnitude can be neglected.在整个试验时间内连续观测，个别较高的脉冲可以忽略oThe noise level is required to be less than 50%magnitude of the highest detected impulse.外围噪声水平应低于规定的视在放电量的50%pWhen test voltage is raised to U2 and decreased from U2,the inception and extinction voltages a
11、re recorded.在电压升至U2及由U2降低的过程中，记录起始可能的放电电压和熄灭电压123.Test Procedure and Permissible Apparent ChargepDuring the first step under the test voltage U2,the maximum apparent charge is recorded.pDuring the second step under the test voltage U2,discharge impulses need to be observed continuously and the maxim
12、um apparent charge is recorded.30min 5s 5min U1 U2 mmUUU3/31U1:pre-applied Voltage 预加电压U2:measuring voltage 测量电压Um:the maximum line voltage3/5.12mUU pCq5003/3.12mUU pCq300在电压U2的第一阶段应读数并记录pNo record is required under test voltage U1.在U1阶段无需观测记录在电压U2第二阶段整个时间内，应连续地观测和记录局部放电水平13 If the following results
13、 are obtained,the PD experiment can be passed.3.Test Procedure and Permissible Apparent Chargep During the test procedure,the test voltage never suddenly decreases.p During the last 30 minutes,the magnitudes of all observed impulses are smaller than the permissible apparent charge and do not increas
14、e towards the permissible apparent charge.如果满足两个条件，则试验合格试验过程中，试验电压不产生突然下降在施加电压U2的第二阶段的30分钟内，所有测量的视在放电量连续维持在低于规定的限值，并且不表现出明显地、不断地倾向允许最大限制值增长的趋势144.Detection Circuits for TransformersTwo ways of the test：induced voltage test and applied voltage test.Principles of PD circuit selection 两种试验方法：感应加压方式，直接加
15、压方式 试验回路选择采用尽量短的引线在试验中对主纵绝缘都能同时得到所应施加的电压uTo execute the test with required voltage on both main insulation and longitudinal insulation.uTo use high voltage leads as short as possible.154.1 Detection circuits for single-phase transformers4.Detection Circuits for Transformers a A Z X x a A Z X x CK A
16、a x X Z A Z X a x CK (a)(b)(c)(d)单相变压器的测试回路applied voltageinduced voltage164.2 Detection Circuits for Three-Phase Transformers4.Detection Circuits for Transformers a A B C X Y Z Z b c x y z o +（a-1）a A B C X Y Z Z b c x y z o +（a-2）+ABCABCUA=0.25U,UB=0.75U,UC=UUBC=1.75U,UAC=1.25UUA=0.5U,UB=U,UC=0.5U
17、UAB=1.5U,UBC=1.5U三相变压器的测试回路17 a A B C X Y Z Z b c x y z o (b)a A B C X Y Z Z b c x y z o (c)4.Detection Circuits for TransformersABCUA=0.5U,UB=0.5U,UC=UUAC=1.5U,UBC=1.5UUA=0.5U,UB=0.5U,UC=UUAC=1.5U,UBC=1.5U185.Calibration a A B C CO uo oil tank(earth)X Y Z Z b c x y z o a A B C CO uo X Y Z Z b c x y
18、 z o Co0.1CxCx:entrance capacitance 入口电容Co：50100pFHCuK00)1(00kxCCHCuKCalibration impulse injected from the HV terminalCalibration impulse injected from the measuring terminal高压端校正入口校正Ck:capacitance of bushing 套管电容19 C0 C0 u0 u0 Z Z 5.CalibrationlExecute calibration at the place close to the detectio
19、n terminal.Requirements of calibration:lPut calibration unit as close as possible to the HV terminal in order to avoid influences of parasitic capacitances.lRecord the detected apparent charges and the relevant detection and calibration places.在测量部位和校正部位要接近为了避免接线杂散电容的影响，标定单元尽量靠近高压端应记录测量部位和校正部位校正要求20
20、6.The Influence of Discharges in Bushing QX QK CK CX Cd ux uk ex;ek xkkxkxCCQQeekkxxQCCQ e.g.Cx=2500pF,Ck=250pF Qk=20pC,Qx=200pC21多端测量定位法7.Electrical Location of PD in TransformersLocation by multiple-terminal test u0 M M M M C0 C0 q3 q1 q2 q4 O O O O Z2 Z1 B O Am D Z3 C u0 a Z4 A X Calibrationq at
21、measuringterminalsRatio of qinjectionpointinjectionchargeA(q1)Am(q2)a(q3)X(q4)q1/q2q2/q3q3/q4A-Oq0q1AOq2AOq3AOq4AOq1AO/q2AOq2AO/q3AOq3AO/q4AOAm-Oq0q1AmOq2AmOq3AmOq4AmOq1AmO/q2AmOq2AmO/q3AmOq3AmO/q4AmOX-Oq0q1AxOq2AxOq3xOq4xOq1xO/q2xOq2xO/q3xOq3xO/q4xOa-Oq0q1aOq2aOq3aOq4aOq1aO/q2aOq2aO/q3aOq3aO/q4aOA-Bq0q1ABq2ABq3ABq4ABq1AB/q2ABq2AB/q3ABq3AB/q4ABAm-Dq0q1AmDq2AmDq3AmDq4AmDq1AmD/q2AmDq2AmD/q3AmDq3AmD/q4AmDCalibration 校正PD measurement 局放测量q at measuring terminalsRatio of qA(q1)Am(q2)a(q3)X(q4)q1q2q3q4q1/q2q2/q3q3/q422The end
