電力電容器的局部放電測(cè)量ppt課件

1、Lecture 7 PD Detection in Power Capacitors電力電容器的局部放電測(cè)量1. Partial Discharge in Power Capacitors2. Parameters and Standard3. Electrical Detection of PD in Capacitor1. Partial Discharge in Power Capacitors1.1 the characteristics of power capacitorsoInsulation structure of capacitors: oil-impregnated pa

2、pers, oil-impregnated dielectric membrane and their combination.絕緣結(jié)構(gòu)：油浸紙，浸漬薄膜及其組合oExtremely high electrical field stress exists in capacitors and partial discharges are very possible to occur inside.介質(zhì)工作場(chǎng)強(qiáng)特別高，內(nèi)部特別容易發(fā)生局部放電電力電容器的特點(diǎn)1.2 Inception and damage of PD in power capacitor 1. Partial Discharge

3、in Power CapacitorsU+cbbaadU+cbbaadCBrbrciEdu)(11CBdUErbrbiThe lifetime of capacitor suffering from PD decreases exponentially. PD is a key factor that results in expanding and incipient fault of power capacitor. 在局部放電作用下，壽命是隨著電場(chǎng)的增加而呈指數(shù)形式下降的 局部放電是造成電容器膨脹和早期損壞的一個(gè)重要因素 2. Parameters and Specification2.

4、1 Parameters to estimate the PD of capacitor lApparent charge, qlInception voltage, UiThe AC voltage across the capacitor at which the discharge magnitude exceeds a given value qg. vsCKTnq) 1(5vsCq CdRdCkCxAB)1 (kdxdvCCCCCnF40 xCpCqg3nF40 xCpCCqxg10/5 . 1視在放電量升壓過(guò)程中，觀(guān)測(cè)到的放電量超過(guò)某個(gè)規(guī)定值時(shí)的最低電壓Inception volt

5、age (stress): The AC voltage (stress) across the sample at which discharges start to occur when the voltage is increased .lExtinction voltage, Ue降壓過(guò)程中，觀(guān)測(cè)到放電量低于某個(gè)規(guī)定值的最高電壓值。The AC voltage across the capacitor at which the discharge magnitude is less than the given magnitude qg. queuiu b a 30 20 10 0 1

6、0 20 Time (min) q (pC) a is better than b2. Parameters and SpecificationlChange of q with voltage applying time放電量隨加壓時(shí)間的變化2.2 Procedure of PD detection2. Parameters and StandardsU1:pre-applied Voltage 預(yù)加電壓 Type U1 (kV) U2 (kV) U3 (kV) Requirement Note Shunt capacitors 2.15un, 1s 1.2un, 10min 1.5un,

7、10min Series-connected capacitors 4.5un, 1s 1.6un, 10min Breaker capacitors 1.8un, 1s 1.1un, 10min During last 10min, no PD impulses with increased magnitude are observed. un is working voltage. U1 U2 U3 t1 t2 t3 U2:holding voltage 保持電壓U3:measuring voltage 測(cè)量電壓u Power source: sine wave, 50Hz,60HzuTh

8、e capacitance difference before and after test should not exceed the difference caused by a fuse burning out.uA simulating small capacitors can be used when sensitivity or capacity could not meet the test requirements.2. Parameters and Standards試驗(yàn)電壓為正弦波，頻率為50或60Hz測(cè)試前后測(cè)量電容，兩次測(cè)量值之差不能超過(guò)一根熔絲斷開(kāi)的差值如果被試電容器

9、的電容值太大，在整臺(tái)上不能得到滿(mǎn)意的精度或設(shè)備容量不夠的時(shí)候，用模擬的較小電容器進(jìn)行試驗(yàn)。3. Electrical Detection of PD in CapacitorThe capacity of a power capacitor is much larger than the usual HV equipments. Large capacity of the power source is required for PD experiment of capacitors. 3.1 Power Source and Circuits(1) Power sourceCompensat

10、ion reactor is used in series or parallel with Cx so that to decrease the capacity of testing transformer 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 series試驗(yàn)電源及回路電容器的容量比其他普通高壓設(shè)備大很多 ，因此所需的試驗(yàn)設(shè)備容量也

11、很大采用補(bǔ)償電抗器與試品串并聯(lián)的方式滿(mǎn)足實(shí)驗(yàn)變壓器的容量要求(2) Detection circuits vsCKTnq) 1(5vsCq CdRdCkCxAB)1 (kdxdvCCCCCe.g.pFCx2001pCqs05. 0FCx2002sqpC50CkqsCv3. Electrical Detection of PD in CapacitorsensitivitynA Balanced detection circuit is recommended3. Electrical Detection of PD in CapacitoruThe straight detection cir

12、cuits may be used. In order to obtain high sensitivity, the coupling capacitor should be at least as large as the sample. A second sample is used as the coupling capacitor, Ck=Cx.CxZdZmeCk=CxoACx2ZmeoACx1Zd1Zd2采用直接測(cè)量回路，并用另外一個(gè)試品作為耦合電容使用平衡檢測(cè)回路(2) The influence of internal inductance3.2 Some problems n

13、eed to be noticed(1) Requirements of detection impedancesuThe capacitance range of power capacitors is larger than that of many other HV equipments，several detection impedances are needed to match the capacitor samples, so that to get the proper frequency-band and sensitivity.3. Electrical Detection

14、 of PD in Capacitor電力電容器的電容量比其它高壓設(shè)備電容量的變化范圍大, 需要準(zhǔn)備多個(gè)檢測(cè)阻抗，以匹配不同電容量大小的試品. 以便得到合適的檢測(cè)頻帶和靈敏度。uDetection impedances is required to withstand large current.檢測(cè)阻抗需要承受較大的電容電流對(duì)檢測(cè)阻抗的要求注意的問(wèn)題)1 (kdxdvCCCCC)/(kxkxtCCCCCdC(2) Connection types of capacitor elements influence detection results.3. Electrical Detection

15、 of PD in Capacitor電容器元件的連接形式會(huì)影響檢測(cè)結(jié)果。xCxCxCxCdURdCdCkxU)1 (kdxdadCCCCqUxCxCxCxCxUdURdCdCk)1 (kdxdadCCCCqU11nCCnCCCxkxkk)() 1(111dkxdkkdkdddCCCnCCCCCCUUK(3) The influence of internal inductancePower capacitor is not pure capacitance. The internal inductance comes from :internal leads, leading out wires, capacitor elements connecting in series or parallel. L0.10.3H電力電容器不是純