Everything You Need To Know To Find The Best insulation resistance tester

Choosing the best insulation resistance tester to do the job correctly is essential. With so many models on the market, people sometimes get lost in choosing the right one. So, how are you going to pick a suitable insulation tester? To find out the response, it is essential to understand which method of research is critical.

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Examine strong insulation against lousy insulation. The excellent insulation is of high resistance, while the weak have comparatively low resistance. Impairment in insulation can cause electrical leakage, which can be harmful to electrical circuits and machines. But you need to get the one that’s best for your application.

Check the tips below that will help you choose the right insulation tester megger.

What Equipment Needs Testing?

First, make a list of common tools that you plan to need for an insulation resistance inspection. Write down the device’s nominal voltage level found on the machine’s nameplate and the average amount of insulation resistance checks you expect to do annually. The nominal voltage will help decide what test voltage the tester requires. The reported annual number of insulation resistance tests could be unexpected. With further testing to be carried out, the test instrument’s overall accuracy, reliability, and convenience features become more critical.

What Are The Voltage Requirements?

The output test voltage applied to the equipment should depend on the prescribed insulation resistance test voltage of the manufacturer. If test voltage is not listed, use the industry’s best practice results. Make sure you use an insulation resistance tester to supply the necessary output test voltage. Not all insulation resistance testers are the same: some may only provide up to 1,000 VDC, while others can supply 5,000 VDC of test voltage or more.

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Where Are The Tests Going To Take Place?

Considering the testing environment and other future applications of the insulation tester megger, it can help pick additional functions. For example, using one instrument for both a traditional digital millimeter and isolation resistance testing will add convenience. Because all circuits and devices must be electrically de-energized before the insulation resistance tester is attached to the equipment, it is also less practical to bring both the optical voltage test multimeter and the insulation resistance tester to different locations.

Experience level?

Any research instrument is just as successful as the individual’s competence and skill level operating the equipment and interpreting its readings. When choosing an insulation resistance tester, remember the experience of the people conducting the insulation resistance tests. Simplicity and limited functionality can be seen as though the application requirements are minimal and the level of expertise is minimal.

Measure the Range

Present measurement is another aspect that has to be taken care of. Look whether you test leakage current or polarization current. Leakage current can be detected using an insulation tester, and then you can measure the amount of leakage in the insulation. You can use spot reading to get the leakage current. Apply the test voltage to the test part and then read the resistance after 60 seconds. You may calculate the leakage current through the insulation in this manner.

Digital or Analog Display

An analog display with a pointer or a journey will display useful information from an accomplished operator. It is essential to verify if the lead is running smoothly or only waving in between. It isn’t easy to recognize this information on an electronic monitor.

Ultimately as the point travel ceases, the operator must remember the scale readings that maximize the manual error. It can be removed using a digital model, and it has a simple role that can be quickly identified.

This has nothing to do with it being a pv system. It does have to do with intermittent insulation faults. They are a real pain to find some times. The ir tester can only test it right this second and if right this second there is no fault it will not find anything.

Sometimes you have to resort to changing out the most obvious wires one by one until the problem goes away. This is maddening to the end user but if you can't find the fault, it is the only way.

The other issue is that sometimes the apparatus that is reporting the fault is itself faulty and there is nothing wrong with the conductor insulation at all. For instance, since this is happening when it is wet out, it might be you are getting condensation on a board where the testing originates. This is happening on two different residential systems, correct? Not more than that? What inverter model? What are the string arrangement/sizes of the two systems, i.e. two strings of 10 modules? And how often does it happen? Every time is rains? You might want to try disconnecting all but one string and letting it run for a few days thru a rainy period that you are confident would cause the issue to show, then connect a different single string, and repeat, etc, until you can isolate it to one string. From there you may be able to find it, or you may need to jumper out half the string (making sure to stay above min startup voltage and divide and conquer until you identify the module or wiring that is causing it. Significant work, but maybe not as much as removing, inspecting, and replacing every module and every wire in the array. I don't have experience with an Insulation Tester but I too am interested in the best way to tshoot this problem because it will likely happen for some of the systems I have installed as they age.

As far as the voltages to ground not adding to the voltage across the + and - leads, I don't think that suggests anything is wrong for ungrounded or functionally grounded arrays.

This is happening on two different residential systems, correct? Not more than that? What inverter model? What are the string arrangement/sizes of the two systems, i.e. two strings of 10 modules? And how often does it happen? Every time is rains? You might want to try disconnecting all but one string and letting it run for a few days thru a rainy period that you are confident would cause the issue to show, then connect a different single string, and repeat, etc, until you can isolate it to one string. From there you may be able to find it, or you may need to jumper out half the string (making sure to stay above min startup voltage and divide and conquer until you identify the module or wiring that is causing it. Significant work, but maybe not as much as removing, inspecting, and replacing every module and every wire in the array. I don't have experience with an Insulation Tester but I too am interested in the best way to tshoot this problem because it will likely happen for some of the systems I have installed as they age.

As far as the voltages to ground not adding to the voltage across the + and - leads, I don't think that suggests anything is wrong for ungrounded or functionally grounded arrays.

Yes 2 systems.
#1
installed
FRONIUS w PRIMO (transformerless, less than 5 years old)
3 strings of 8
24 @ SHARP NT-185U1 panels
4.44 kW


#2
installed
SMA TL US
2 strings of 9
18 @ Canadian Solar CS6P-250M , 250 Watt modules
4.5 kW

FWIW, "Ground-fault monitoring for SMA SB TL-21: Insulation monitoring: Riso > 500 kΩ"
--------------------
On both systems, faults shuts down INV later in rainy season, every time it rains heavy.
Then it may last for weeks or month.
Major loss.
----------------------
On system #1, I voltage tested string ends to ground......
and then panel counted per panel V to fault location....
and then shuffled no less than 7 panels around on roof physically.
I tried to get all bad panels into one string and leave 2 good strings.
But to no avail. INV triggered each time.
....And...... now getting new error codes. ("low DC V")
===> Will replace all panels. I am fine with that, as is customer. They had 2 decades. And I spent many hours.
So my questions on #1 are out of curiosity only!

However, system #2 bothers me for 2 reasons:
- It is just past 10 yrs old. Not much.
- - I installed it.
I will return and remove what seems to be 1 faulty panel in each string.... and see if INV starts up.
I have my doubts.

Additional Q's:

Why don't the partial DC voltages add up to total string V?
E.g. in a string of 8 (no MLPE's)
+ to - 331 VDC
- to ground 158 VDC
+ to ground 140 VDC
(....adds up to 298 VDC)

also:
+ to - 332 VDC
-to g 203 VDC
+ to g 122 VDC
(....adds up to 325 VDC)


Also, what exactly goes wrong in these "insulation resistance low" cases? In particular when no visible damage can be found.
I read the the insulation may deteriorate over time?
Does it break up/crack/microcrack and allow moisture to penetrate?
Does this mean it actually absorbs water?

Does it change chemically and become less resistive/more conductive?

Or is it faults with connectors and nor conductor insulation?

What is the fix? Replace all panels?

It sounds to me like module glass or backsheet failure that is allowing in moisture that is compromising isolation from ground. I've seen this, and while I forget the details it definitely confused the heck out of me, too. (I had two failing modules next to each other, which made it even harder to narrow down.) If there is water getting into the module creating a conductive enough path to the frame and racking then essentially a module could be grounded at/near both its positive and negative ends. So when you measure the string positive and negative to ground you don't measure the affected panel either time. Or some portion of it.

Sorry man, I know it sucks.