220kv Lightening Arrestor testing

[kssschsekhar]

Dear all

220kv Lightening Arrestor

what type of site tests are preferred during Operation and Maintenance of 220 kv Lightening Arrestor?

Can the following are helpful
1.Third hormic current measurement (online test)
2.Insulation resistance meansrement. If yes separate top stack and bottom stack and total LA. (Offline test)

Please give any site for furthur site test.

What is minium IR value of the LA preferred to discard the LA?

 

[oldfieldguy]

Doble Engineering and NETA recommend power factor testing of arrestors.

This is an off-line test. Individual elements are tested separately and the results compared with historical data from previous tests or with like items.

old field guy

 

[kssschsekhar]

Hi oldfieldguy

Thank you for the suggested test.

Could you please tell me few service providers names. Or Name of testing equipment and suppliers.

regards

 

[oldfieldguy]

I'd be more comfortable suggesting that you look at

http://www.netaworld.org/memberlist.cfm?categoryID=7

for a testing company in your area, assuming you're in the US.

The equipment is available for rental or purchase, but the testing is a somewhat specialized function.

If you're outside the US, I'm sure that there are companies with similar capabilities.

I neglected to say that an infra-red thermography of the arrestors in question is also not a bad approach. WE have detected some arrestors with significant temperature differences from adjacent units, and these were replaced. They also showed poor results on the subsequent power factor testing.

old field guy

 

[cuky2000]

Many utilities choose not to test surge arrester in service. Other requires lightning counter to monitor operability of the unit.

There are available today surge arrester monitoring system that may continually or periodically check the status or degradation of the unit

The most popular arrester field testing are:

1. Power Factor /watt loss test.
2. Infrared analysis.
3. Resistive leakage current.

Impulse test may be impractical since require onsite impulse generator.

 

[kssschsekhar]

Hi all

Thank you for suggested testing.

We are having 33nos. 220kv Lightening arrestors. these are in service for 10 years onwards. Suddenly within 2 months span one after another transmission Line Lightening arrestors failed.

Generally every year we do IR value testing and we observed always more than 5000 Mega ohms values. Recently the following insulation resistance values found for one of the arrestor.

Voltage : 5000 vdc, Meggar make Insulation tester.
Top stack - 80 Megaohms
Bottom stack - 6000 Megaohms
Total stack - 5500 Megaohms

Can this LA (Lightening Arrestor) needs any tests/replacement?

Could you please suggest any thing.

Thanking you

 

[pajce]

voltage is high enough that megger (5kV DC) test will not give you complete results for condition of insulation. DOBLE test is what you need. It applyes AC 10kV voltage across the arrestor and measures capacitance, dissipation factor, leakage current.

 

[pajce]

yes, that 80M on top stack is very low. Look at NETA standard.

 

[neman1]

80 Megaohm value of upper stack is too low compraed to other stack and there is chance of arcing or moisture ingress inside the stack. If arrestor is still in service then I suggest to perform the on -line resistive leakeage current moitoring test on this and see the value of Ir is more than 500 micro-amp. For conducting this test LA should be mounted on base of isolated ground.

 

[kssschsekhar]

Dear sir

Before this IR value measurement we performed the on -line resistive leakeage current moitoring test. we was not find any clue.

Regards

 

[neman1]

What was the value of It and Ir and how you have performed it? please reply.