Junior Member
Posted April 12, 2020
Hello All,
I'm interestion to know what exact safety concerns might happen in the scenario of primary and secondary injection testing respectively.
It's my undetending that the main risk is arc flas on primary injections because this test add high current at low voltage level.
I want to know your tought..
Thanks.
Seasoned Member
Posted April 13, 2020
Maybe some slight sparking if the breaker or cables come off while testing. Essentially, there is no/very low danger.Originally Posted by Granyerd
NETA Level III
Posted April 13, 2020
Pro Subscriber
Your biggest risk of arc flash comes from connecting the high-current set to the power source. We usually supply ours with 100A 3p 480V. Like others have said, primary-injection is a low voltage, high current test, so the risk of electrical shock from the test set output is low.
As for actual testing, the risk of arc flash is reduced, but still present at very high currents. If your connection points are not strong, its possible to produce sparks that can be fairly significant at currents above 1000A.
You should also read the maintenance manual for whatever breaker you are testing because many times drawout breakers have specific size bus that must be used otherwise you risk a connection that is too loose, or a connection that will damage the breaker fingers from spreading too far.
If you connections are too loose, its possible the breaker can come off the test set when pushing extremely high currents (like >10kA). I've had to literally strap breakers to the test set before when doing instantaneous testing on 5000A mains.
You also risk overheating and damaging the current path if you do not properly apply current. I've seen finger clusters get burned many times. You will also want to be careful not to burn yourself when switching phases as the current test path will be very hot.
Experienced Member
Posted April 13, 2020
Pro Subscriber
First, I believe you would need a voltage level in excess of 50V to provide a situation for ARC FLASH (New NFPA will probably remove this requirement).
I have actually tested a 10,000A breaker at 300% (30,000A) and the measured voltage to ground was ~37V. That being said, every test set is designed differently, so I do encourage technicians to verify themselves. As stated before, the greatest threat to testers when it comes to Arc Flash is the input power supply for the test set and poor connections.
Now, that being said, the way the hi-current test set was explained to me when I was starting was it is the same equipment used for arc welding. The difference between a welding machine and the current test set is the medium being used to make connection, as a welding machine uses a poor connection rod to heat metal, and the Hi-Current test set is solidly connected to minimize heating metal, and if use of the tables in NEMA AB4 are used, heating is minimized. I do realize that this isn't exactly how it works, but it did instill in me the importance of a solid connection to prevent welding our connections to breakers, or using our clamps as short circuits (as a co-worker proved with my clamp).
The biggest concern for me is heat. Sometimes you do thermal breakers with high long time delay with cables and minimal contact. This can cause some heat up that can require some good gloves. I always try to find the best connection and surface area, but sometimes you have to trade proper rating for what's practical.
Member
Posted August 17, 2020
I see you also asked about secondary injection. I don't believe there is any inherent risk to secondary injection; assuming this only means using a test kit to test directly through the trip unit.
Many new gen breakers' "secondary injection" (I to call them tertiary injection) kits are just putting numbers in the computer. No way mini usb is putting AC current in the secondary with just a PC cable. Gotta be careful.
Junior Member
Posted December 28, 2020
Practically, the main danger of primary injection testing is heat when testing larger breakers with long trip times. The bussing or cables you are using will get hot and burn you if you grab them to switch lines.
Since the voltage is so low, there is very little shock or arc flash danger.
Secondary injection testing there is virtually no danger, unless performing the test under circumstances where you have created danger for yourself, like tripping a breaker in service accidently or something else horribly stupid.
However, I would defer to all safety materials and mandates that apply at all times.
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