Partial discharge material limiting values

[Casper Hansen]

Hi PF

According to IEC 60885-2 and IEC 60270 the acceptance criteria in partial discharge (PD) measurements on high voltage cable insulation state that PD level should be below (< 5 pC). The insulation material that is refereed to is often XLPE which is a sensitive insulation to PD. Other materials like oil or silicone are not so sensitive to PD. So, have some of you encountered PD limiting value for other material than XLPE?

I am looking for PD limiting value on materials often used in transformers and cable joints like. Epoxy, Oil silicone and PEEK.

 

[Babadag]

In my opinion, partial discharge test applies to electrical equipment and not to the insulation
material . There are standard procedures for partial discharge of:
Cables, splices and terminations
Power transformers and bushings
Switchgear
Motors and generators
See for instance:
http://www.globaltest.com.au/Services/Partial-Discharge

 

[Casper Hansen]

In my opinion, partial discharge test applies to electrical equipment and not to the insulation
material . There are standard procedures for partial discharge of:
Cables, splices and terminations
Power transformers and bushings
Switchgear
Motors and generators
See for instance:
http://www.globaltest.com.au/Services/Partial-Discharge

PD test is applied to the equipment but that is the insulation that is being tested. For instance PD test on cables are testing the XLPE insulation barrier. If the insulation barrier was made of another material, the PD acceptance criteria would be different.

 

[Babadag]

Let's take IEC 60840 /2004 Power cables with extruded insulation
and their accessories for rated voltages above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV)
Test methods and requirements.
According to Table 1 – Insulating compounds for cables- for instance- the considered insulation materials are : LDPE, HDPE, XLPE, EPR, HEPR.
No difference I could find for partial discharge test specifically for XLPE only. See:
12.3 Electrical type tests on complete cable systems
12.3.4 Partial discharge tests
The same in IEC 60502-2/2005 :
16 Routine tests. 16.3 Partial discharge test
Here the considered insulation materials are: PVC(b), XLPE, EPR and HEPR.
The standard IEC 60885-3 it presents how to proceed only.

 

[Casper Hansen]

Let's take IEC 60840 /2004 Power cables with extruded insulation
and their accessories for rated voltages above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV)
Test methods and requirements.
According to Table 1 – Insulating compounds for cables- for instance- the considered insulation materials are : LDPE, HDPE, XLPE, EPR, HEPR.
No difference I could find for partial discharge test specifically for XLPE only. See:
12.3 Electrical type tests on complete cable systems
12.3.4 Partial discharge tests
The same in IEC 60502-2/2005 :
16 Routine tests. 16.3 Partial discharge test
Here the considered insulation materials are: PVC(b), XLPE, EPR and HEPR.
The standard IEC 60885-3 it presents how to proceed only.

Sorry for my late response.

I have found this, see Figure 9 :
https://www.cablejoints.co.uk/uploa...ement_for_High_Voltage_Cables___SEBA_OWTS.pdf

and this, see Table C2
https://www.cablejoints.co.uk/uploa...oltage__Distribution_Power_Cables___Paper.pdf

both the figure and table shows some typical PD levels for different types of cable insulation.
It makes sanse that Oil can withstand higher PD levels because it is fluid and able to "repair" itself if a possible damage in the materiel occurs. It also seems like that cable termination and joint have higher PD values as well. Do you know any standards dealing with PD levels in termination/joints?

This is all i got i did hope to find some use full IEC standards on this area.

 

[Babadag]

The article is very interesting.
At first a remark: the numbers are noted in German system then 10.000 it is actually 10^4 [pC].
In my time I was involved in cable manufacturing paper foil oil filled cable -up to 110 kV, low pressure oil -No standard required PD test then [See IEC 60141-4 for instance]. PILC was a new technic I wasn't involved in it.
We start testing PD when XLPE appeared only.
For extruded insulation cables the accessory tests are the same as for cable itself-See IEC 60502-2, IEC 60840, IEC 62067.

 

[Casper Hansen]

The article is very interesting.
At first a remark: the numbers are noted in German system then 10.000 it is actually 10^4 [pC].
In my time I was involved in cable manufacturing paper foil oil filled cable -up to 110 kV, low pressure oil -No standard required PD test then [See IEC 60141-4 for instance]. PILC was a new technic I wasn't involved in it.
We start testing PD when XLPE appeared only.
For extruded insulation cables the accessory tests are the same as for cable itself-See IEC 60502-2, IEC 60840, IEC 62067.

Yes according to the article the PD limiting values for all the other materials is way above the PD values for XLPE, which makes me think that the XLPE is a weak material to withstand PD.

I did PD measurement on a cable (testing XLPE insulation barrier) with a great result of PD level < 5 pC
I did the same PD measurement on the cable terminated in a cable joint filled with epoxy now i measure a PD level of 48 pC.

I expect the high level of PD to be inside the cable joint facing the epoxy insulation barrier and not the XLPE. That is why I am looking PD acceptance criteria (PD levels) for other material than XLPE.