Live testing - could this be a Part P assessment failure?

[Engineer54]

E54,
I know HV stuff needs cleaning, and I had envisaged a method, as you say, along with the same principles also that are used for water fire extinguishers which are used on LV electrical equipment.
However, I was under the impression that it was normally dry blast cleaning or dry ice cleaning that was used.
Though I can believe it possible to use water, after all water is an insulator...

Only if it's deionised water at those sort of voltages!! Samples of water in the water wagon need to be tested, prior to firing up at the lines/strings. If parts per million exceed the maximum allowable then it can't be used. Never seen those other methods you mentioned used, probably raw material and the means to get those materials to the lines/strings etc, would be too expensive. Air blasting as i remember was tried, but some of these built-up deposits are set like concrete, and need soaking and pressure to shift them...

 

[netblindpaul]

E54, You bit, as I thought you would!
Remember water is H2O and that is that.
We used dry ice on our drives which had deposits set like concrete almost.
Also there seems to be a Co. 'tother side of the pond that uses walnut shells and other stuff, like we use over here for delicate blasting of soft materials.

 

[Engineer54]

E54, You bit, as I thought you would!
Remember water is H2O and that is that.
We used dry ice on our drives which had deposits set like concrete almost.
Also there seems to be a Co. 'tother side of the pond that uses walnut shells and other stuff, like we use over here for delicate blasting of soft materials.

Dry ice is water yes, but in a completly different form and not as easy to store. The equipment is going to be far more expensive to blast at what can be high distances too,. They use water because it's cheap, the equipment to pressurise it, is also relatively cheap. I'm not saying there are not other means of achieving the same ends, just that all are going to be a more expensive proposition to run and maintain, than water and a simple high pressure pump!! It's a proven system that Works!!! ...And great fun to operate too! ...lol!!!

 

[netblindpaul]

No mate Dry is is solid CO2 (excuse the lack, of subscript).

 

[Engineer54]

Sorry thinking of something completly different ... that and age is my excuse!!...

Oh, ...and H2O is not just water, and that is that!!! If it was there would be an awful lot of water chemists and engineers out of a profession!! Water is full of contaminates depending on the source. Would you really use tap water to top-up a battery?? No you would use deionised or distilled water, or that battery ain't gonna last too long....

 

[Les Dove]

I would have to agree with tuttle, if you look at page 140 OSG (little red book) there is just one RCD reading per group of circuits not one RCD reading per circuit. I contacted Hager a year or so ago and their tech dept said to test at the origin of supply otherwise you would need to dis-connect all the other neutrals to get correct readings.

 

[hyperloop]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

 

[HandySparks]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

No. The point of doing RCD testing is to verify the performance of the RCD. The tester causes a specific differential current to flow and checks for time to trip. Since the test current is determined by the test instrument, independent of the circuit resistances, it makes no difference where on the load side the test is made.

Testing of the circuit wiring should be done by R1, R2, Zs prior to the RCD test.

 

[Engineer54]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

I'm sorry to say, that it's you that don't understand the point of RCD testing, or indeed how to conduct them!!!

Check with the manufacturers, all will tell you to test there RCD's/RCBO's outgoing/load terminals... There are one or two that require a short conductor(s) (a matter of a few inches) connected to the load terminals and test from those conductor ends.

Nothing to stop you testing from remote locations mind, but just as confirmation of tripping, but not for your actual notifiable readings...

 

[deploydasausage]

thanks to everyone that posted, i only just discovered that i was conducting rcd tests wrong. ...testing at the board will save me loads of time!!!

 

[wallyanker]

I was taught at College to test at the board, working live with CU cover off is acceptable in certain situations, like testing. If for any reason you can not open the CU with power on, test at the nearest available point.

 

[Engineer54]

I was taught at College to test at the board, working live with CU cover off is acceptable in certain situations, like testing. If for any reason you can not open the CU with power on, test at the nearest available point.

Can't think of any other way of conducting Ze, Zs, Polarity, RCD/RCBO tests etc!! lol!!
I think an assessor would be wanting to see a candidate perform such tests, ...Wouldn't He?? lol!!

 

[SPARTYKUS]

Surely not, he'd be risking, well, risking his LIFE!

 

[Engineer54]

Surely not, he'd be risking, well, risking his LIFE!

Yep, they ought to ban all these silly live tests, they only generally show-up problems anyway!! lol!!

 

[wallyanker]

Seems like the safest way to do it to me but I am not sure if switching on with the cover removed is a big no no in all situations.

Its impossible to conduct the live tests without the cover off!!