according to iec standard 60270 a partial discharge (pd) is...according to iec standard 60270 a...

SEPTEMBER 5TH 2017

SANTIAGO DE CHILE

MARCO BONGIORNO

CAMLIN PRODUCT SPECIALIST

PARTIAL DISCHARGE: ONLINE MONITORING APPROACH

IN POWER TRANSFORMER

• INNOVATIVE APPROACH FOR PARTIAL DISCHARGE

MONITORING IN POWER TRANSFORMERS

• IMMEDIATE DATA ANALISYS

• USER FRIENDLY APPROACH

WHAT IS A PARTIAL DISCHARGE?

According to IEC Standard 60270 a Partial Discharge (PD) is :

“Localized electrical discharge that only partially bridges the insulation between conductors and which can or can no occur adjacent to a conductor”.


Neglecting Partial Discharge (PD) activity can lead to further degradation of the insulation system, resulting in possible complete discharges


Additionally, three notes follow the above definition:

– NOTE 1: Partial Discharges are in general a consequence of local electric stress concentrations in the insulation or on the surface of the insulation. Generally, such discharges appear as pulses having a duration of much less than 1 us [...].

– NOTE 2: “Corona” is a form of partial discharge that occurs in gaseous media around conductors which are remote from solid or liquid insulation. “Corona” should not be used as a general term for all forms of PD.

– NOTE 3: Partial discharges are often accompanied by emission of sound, light, heat and chemical reactions.

NEW

INSULATION

AGED

INSULATION

DEGRADATION

AND AGEING

PARTIAL

DISCHARGES

Accelerating (cause)

Increasing(effect)

QUESTION: For insulation materials, does Partial Discharges represent a cause or an effect of the ageing mechanism?

WHY PARTIAL DISCHARGE?

Confirmation that H2 development is due to PD and not to stray gases▪ Stray gassing is due to the refining process and the possible presence of certain incompatible

materials in the transformer or additives in the oil.

Early warnings compared to DGA (e.g., after oil treatment)

Potentially faster response in correlation with Load/Temperature/Voltage/OLTC/Short-circuits

BENEFIT OF PARTIAL DISCHARGE

PD detection in bushings and correlation with Bushing Capacitance/Tandelta

DGA vs PD Fault due to PD DGA 2 gas

H2, CODGA 3 gasDuval

DGA 8 gas PD monitoring

PD detection ★ -- ★ ★★

PD location -- -- -- ★★

PD identification -- -- -- ★★

Sporadic PD activity

-- -- -- ★★

-- not effective★ relatively effective (50%)★★ very effective (90%)

Other faults DGA 2 gasH2, CO

DGA 3 gasDuval

DGA 8 gas PD monitoring

Overheating oil – Hot spot

★ ★★ ★★ --

Fault in paper ★★ -- ★★ --

Arcing -- ★★ ★★ --

Localized defects in bushings

-- -- -- ★★

Ref: IEEE Std C57.113-2010

ϕ[deg]

[V]

ϕ[deg]

[V]

ϕ[deg]

[V]

Phase U Phase V Phase W

Statistical evaluation of• Amplitude• Repetition Rate

PHASE RESOLVED PD PATTERN

Floating corona Shield300 ppm C2H2>1000 ppm H2High Energy Event

Unknown defect>5 ppm C2H2

<20 ppm H2Small PDStress ring puncturing

5 ppm C2H2>300 ppm H2Active PD

Phase-Phase discharges5 ppm C2H2>300 ppm H2Intermittent PD

PRPD COLLECTION

How to interpret PRPD patterns?

What picture/signature/shape should be expected?

Should an expert be consulted?

How is it possible to identify presence of PD activity?

Where the PD defect is??

How is it possible to determine its severity?

What about criteria to determine severity over PRPD

patterns?

Even if the severity is low, how is it possible to understand

if the severity changes over the time?

...QUESTIONS

MARKET DEMAND - ISSUES

Partial Discharges is a broadly successful diagnostic technique used in the factory during acceptance tests, but is not yet widely in use for on-line applications.

Market acceptance of on-line PD monitoring has been negatively impacted by significant difficulties in interpreting the data which often results in utilities remaining tied with system providers, or ‘PD experts’ sharing sensitive data and paying high prices for consultancy services.

INVESTING TIME AND EFFORTS ON

HEALTHY TRANSFORMERS

NOT BENEFICIAL FOR THE UTILITY

PRIMARY TARGET:

To provide a green/yellow/red indication summarizing if the transformer is affectedby internal PDs or not.

MARKET DEMAND - PURPOSE

PD monitors should help Asset Managers in having 100% confidence on which unitsare healthy in order to focus all efforts just on the faulty ones.

SECONDLY:

Automatic identification of which is the phaseaffected by discharges is crucial.

A B C

H1X1

H2X2

H3X3

Offline tests must be properly planned. Useful preliminary info in order to save time and therefore costs:

EXAMPLE: PD SUSPECTED

Which tank?

Is the PD in the bushing? Which bushing?

In case of further acoustic locations, any idea to reduce

the rime required?

MARKET DEMAND - SUMMARY

Market demand for PD Monitoring systems being:

– Cost affordable• No standards for PD

• DGA is typically preferred

– Reliable in terms of hardware• Providing systems…not problems

– Able to provide meaningful warnings• No Panic

– EASY TO INTERPRET

15

Provide simple but reliable information:

Are there PD phenomena inside the transformer?• Is the PD changing?

• In which phase?

• Any correlation with DGA, LOAD, VOLTAGE, etc?

*IEEE C57.127-2007: PD sources in outer parts (leads, etc.) can be detected and located more easily than PD in inner parts. PD within the winding block might be impossible to detect or location might be false even at high levels of activity.

** No literature at all

CAMLIN PD SYSTEM TARGET

Furthermore:

Reduce the need for expert data interpretation

Defer expert need for PD location* and PD identification**

U V W

60

30

1545

Real Time Data Processing

NOISE

POSSIBLE PD

Embedded DB

ϕ[deg]

[V]

PD Pattern PD Trend

STARTING POINT: HOURLY PD SUMMARY 1 Hour

DATA FLOW

17

For all channels:• Amplitude (in V o nC)• Repetition rate

TRENDS

18

10: Intensive amplitude with intensive repetition rate

9: Intensive amplitude with moderate repetition rate

8: Moderate amplitude with intensive repetition rate

7: Moderate amplitude with moderate repetition rate

6: Intensive amplitude with small repetition rate

5: Small amplitude with intensive repetition rate

4: Moderate amplitude with small repetition rate

3: Small amplitude with moderate repetition rate

2: Small amplitude with small repetition rate

1: Minimal event

0: Not meaningful activity

Amplitude increase only

Repetition Rate increase only

Both Amplitude and Repetition Rate increase

Amplitude

Rep

etit

ion

Rat

e

“PD STATUS” AS A MATRIX

19

To INFORMATIONSFrom DATA

PD Status Trend

20

99%Minor Activity (0+1+2):

Medium Activity (3+4+5+6):

Severe Activity (7+8+9+10):

1%

0%

OFF: Transformer OFF

PD PERSISTANCE

21

90 MVA4 months – No PD

300 MVA2 years – No PD

63 MVA3 months - Medium PD

400 MVA1 month – No PD

600 MVA4 months – Minimal PD

CASE #1 Fleet Condition Assessment

22







Inspired by Duval’s Triangle, extensively used for DGA analysis, the Camlin Triangle indicates in which phase the PD activity is predominant

23

CAMLIN PD TRIANGLE

24







CASE #2 Faulty design - Capacitive Stress Ring in 63 MVA distribution

Floating Corona shield detected in 400 MVA AutotransformerCASE #3

CASE #4 PD activities discrimination: HV bushing and Main Tank

2 MONTHSOF DATA

CASE #4 PD activities discrimination: HV bushing and Main Tank

THANK YOU

according to iec standard 60270 a partial discharge (pd) is...according to iec standard 60270 a...

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