01 - OMICRON PD Seminar - Introduction of Partial Discharge Measurement

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Introduction, History and Theory of Partial Discharge Measurement

Rene Hummel, Stephan Krber

Electric fields

What is partial discharge ?

> Partial discharge (PD) is a localized dielectric breakdown of a small portion of a solid or liquid electrical insulation system under high voltage stress.

> Definition from IEC 60270 Specification: Localized electrical discharge that only partially bridges the insulation between conductors and which can or cannot occur adjacent to a conductor.

Evidence of partial discharges

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Evidence of partial discharges

photo: VATech Hydro Austria

Evidence of partial discharges

photo: IPH Berlin

Evidence of partial discharges

photo: IPH Berlin

Evidence of partial discharges

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Evidence of partial discharges

tracking structures

Evidence of partial discharges

Video ...

video: IPH Berlin

Partial discharge / total discharge

photo: TU Berlin

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Electricity around us Important units

Charge Q [1Coulomb] = [1As]:

Charge in movement = CURRENT!!!

The more electrons per TIME interval, the higher is the current

Current = Charge per Time[A] = [Coulomb] per [s][A] = [Coulomb] / [s]

Charge = Current times TimeCharge = Current x Time

+

nucleus1st orbit

2nd orbit

electron-

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q =

Charge How to measure?

> Time Domain Integration q =

q

SI prefixes

kilo Volts [kV]

milli Ampere [mA]micro Farad [F]nano Coulomb [nC]pico Coulomb [pC]

Most used prefixes:

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Charge How it is measured

> Frequency Domain Integration

> More details in chapter FILTER

PD

C RpC

Analog PD measurement systems

PD

C RpC

Digital PD measurement systems

Filter is analogue!

PD

V

0- Detect

AD

MPD600 digital PD measurement system with digital filtering

PD

V

AD

AD

Digital Filter + PD Processor

Communications Processor

Power Management

Fiber Optic Cable

USB 2.0

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PD measurement with the OMICRON MPD software

test voltage over time

PD activity over time

voltage reading

disturbed voltage signal

What are partial discharges?

Partial discharge:

> Local electrical stress in the insulation or on the surface of the insulation

> Always generates electromagnetic signals

> Often accompanied by an emission of sound, light, heat and chemical reactions

Types of PD

> Internal PD> Void discharges, electrical treeing

> External PD> Corona> Surface discharges

Solid insulation

Outer semicon

Solid insulation

Inner semicon

Image Source: Andreas Kchler Hochspannungstechnik

External PD

Surface discharge Corona discharge

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Internal PD

Internal discharge in laminated material

Treeing

Cavity / void discharge

PD classification

Semicon layer protrusion(stress concentration at the tip)

Void (field strength doubling)

Lines ofelectrical field

En = 2