Does anyone now if there is any Standard, that required equipment grounding connection testing (resistance measurement) from equipment to the ground grid? Or a visual inspection is enough? I dont find any requirements in NFPa70. Not sure if resistance measurement from equipment (motor...
In NEMA 01 is specified that "For machines rated 601 V and higher, accessory leads shall terminate in a terminal box or boxes separate from the machine terminal housing. What about lower than 600V? Is a terminal box required by NEMA for space heater leads? Is there a table with space heater size...
I start commissioning test for some switchgear 2 years ago. I did not finish commissioning, and due to company low budget, I had to stop this work for 2 years. Are those test that have been performed still valid? Or those test should be repeated again? Is any Standard that describe this? I will...
What testing method for MV cable insulation do you thing is more reliable? A tan delta that gives a general quality of insulation for entire cable plus a pd test? Or tan delta plus VLF hipot test? I am looking to find the best way to do cable insulation testing, and I need a method that can tell...
A motor of 45 kW from a ventilation unit, (nominal current 82A) due to a bigger load, function actually at 95A-measured current. The motor is cool down by a big air volume of 15C degrease. What are the odds that this motor to be burn? All the cold air can compensate the overcurrent effect? I...
In one instalation of two identical centrifugal pumps that feed the same collector, I observe that if bouth pumps are running the current is around 13.5A, but if only one is running and the other one is in stand-by, the current is 11.8A. The nominal current of motor is 12.5A. Can someone explain...
Supose I test a thermal relay (bimetalic) using current injection-2*setting current(Is) and the tripping time is not correct. Let say is bigger. What will be the write action?
1. Adjust the setting current of thermal relay at a smaller value-Iss and inject again 2*setting current(Is). The...
Is there any prescription that say from what voltage or current thermographic scan is relevant? If not, from yours experience can you give some values?
Thank you!
I have a pump, protected by one eart-fault relay and a breaker. The earth fault relay is set to trip the electrical supply if I have a un-balance current of 4A, for a time longer than 0.5s. I measure the starting time (the time until the current goes from inrush to nominal) 30 days ago and was...
