1 / 13

1 . Occurrence of Discharge

1 . Occurrence of Discharge. 1.1 Partial discharge 1.2 Inception of internal discharge 1.3 Inception of surface discharge 1.4 Inception of corona discharge 1.5 Discharge by electrical treeing. 1.1 Partial discharge.

ursa-griffith
Download Presentation

1 . Occurrence of Discharge

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 1 . Occurrence of Discharge 1.1 Partial discharge 1.2 Inception of internal discharge 1.3 Inception of surface discharge 1.4 Inception of corona discharge 1.5 Discharge by electrical treeing

  2. 1.1 Partial discharge • Electric discharge that do not completely bridge the electrodes are called partial discharges. • 방전크기는 작지만 점진적으로 발전하면 ultimate failure 로 유발가능 • 비파괴시험으로 방전의 진행을 detect 하는게 필수적이다. • 1.1.1 Classification • 1) Internal discharge (Figures 1.1 and 1.2) • 2) surface discharge (Figures 1.3) • 3) Corona discharge (Figures 1.4) • 4) Discharge in electrical trees (Figures 1.5)

  3. 1.1.2 Terminology • Partial discharge 대신에 미국, 영국(ionization) 프랑스(ionisation gazeuse) 독일(Ionisationsvorgange)라고함. • 파생어로는 ionization point , ionization livel • Corona 의 파생어 • 1.2 Inception of internal discharge • 1.2.1 Gas-filled cavities • Figure(1.2(a)-고체 절연체 전계 배 , (b) 배 ( c)유전체와 동일한 크기 (전계가 집중되는 위험이있음)

  4. Breakdown strength of the cavities (dimensions , type of gas , gas pressure) • Ex)a flat cavity of 0.1mm인 폴리에틸렌의 , =2.2 1atm 일때 fig 1.7에서 의 breakdown stress는 6.8kV/mm 이다. • inception stress 는 6.8/2.2 ~~3kV/mm • 부분방전 전계는 설계전계보다 낮아도 일어난다.(3.5 to 7kV/mm) • Breakdown voltage에 미치는 여러가지 요소중 예측치보다 낮은 BDS를 보이는데 그 예로 static charge in wall of cavity 에 의해 예측치는 20%만큼 감소한다.그의 방안으로 the wall을 도전성을 갖게한다.

  5. 1.2.2 Inclusions • Extruded plastics of cast resin 에는 various inclusions : dirt, paper of textile fibres and other foreign particles • inclusions에 의해 BDS는 감소하고 breakdown gas is formed and gas discharges occur. • Gooding and slade 의 metal splinters embedded in the dielectric  local field concentration • 1.2.3 oil-filled cavities • Oil-impregnated paper insulation 의 stress 는 gas-filled cavities와 유사하다.

  6. 1.3 Inception of surface discharge • Surface discharge may occur of there exists a stress component parallel to a dielectric surface.  bushings, ends of cables,the overhang of generator windings and where a discharge from outside touches the surface. • 1.3.1 Discharges in air • Figure 1.8 과 figure 1.9 에서의V와 에 의한 paschen curve 를 볼수있다.(table 1.1  dotted line)

  7. 1.3.2 Surface discharge under oil • Similar formula as for air • Contamination , moisture greatly affect the breakdown stress. • 공기중에서의 BDS 는 습도에 매우 민감하며, 절연유내의 실혐결과보다는 대개 낮은 특성을 보인다. • 1.3.3 Surface discharge under sulphur hexafluoride gas • 절연물에서의 particles 은 표면의 섬락과 부분방전의 원인이 된다. • Brokman 은 이러한 현상을 3가지 변수로 만들어보았다.

  8. (1) roughness of the surface • (2) semiconducting areas - contamination of the dielectric surface(Fig 1.11) • (3) Particle - shape and dielectric constant of particle(Fig 1.12) -particles with sharp edges are dangerous sources of discharge • The flashover voltage decreased with increasing

  9. 1.4 Inception of corona discharge • Corona discharge occur in gases at sharp points in the electrical field(Fig1.13) • Sharp edges , HV sides, laboratory floor… • 1.4.1 corona air • 1.4.2 corona in sulphur hexafluoride gas. • SF6하에서는 코로나 발생시 그의 부산물은 독성이 있다. • 1.5 discharge by electrical treeing • electrical trees start from defects in the insulation(Fig1.15)

More Related