Power Loss Terminology?
Power Loss Terminology?
(OP)
I am an Electrical Engineering intern currently employed at a small Biotech facility.
I am writing to ask about whether there are any specific terms that you would use for describing power loss. For example I mean something like a dip in the power where one would notice the lights dim quickly for a second or two but not affect anything powered by the UPS. Also is there any standard terminology as far as certain amount of time that power would have to be gone before it is called a complete power failure. Would the gap in time, here at the facility it is 8 seconds, to transition from normal power to the back-up generator?
Thanks in advance.
I am writing to ask about whether there are any specific terms that you would use for describing power loss. For example I mean something like a dip in the power where one would notice the lights dim quickly for a second or two but not affect anything powered by the UPS. Also is there any standard terminology as far as certain amount of time that power would have to be gone before it is called a complete power failure. Would the gap in time, here at the facility it is 8 seconds, to transition from normal power to the back-up generator?
Thanks in advance.






RE: Power Loss Terminology?
If the voltage drops to zero for any length of time at all, then you have had a "power failure" or an "outage" or a "power loss".
If the voltage has dropped 10% below normal you have had a "brown out" or a "voltage sag".
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Power Loss Terminology?
Also sometimes refered to as "Dark"
"Would the gap in time, here at the facility it is 8 seconds, to transition from normal power to the back-up generator?"
You would have to check the manufactures info on the transfer time but typically the generator should be on line in 10 seconds, so your gut is about right. You should have some records of this acceptance test, somewhere.
RE: Power Loss Terminology?
If you can access this presentation, it should give you some leads for additional Googling.
The ITIC (CBEMA) curve is often referenced as the standard for short-term voltage fluctuations.
10 second loss of power on transfer to engine-generator is a common requirement. It's achievable if equipment is properly maintained and tested.
RE: Power Loss Terminology?
RE: Power Loss Terminology?
RE: Power Loss Terminology?
But to rephrase the question, would the company that provides to power for the facility be able to provide data for a voltage sag, power loss, etc if one occuried? I was just wondering is there a way to obtain that easily.
RE: Power Loss Terminology?
RE: Power Loss Terminology?
Normally information on voltage sags will not be available from the utility. This data usually comes from customer-owned metering, unless there is a special project set up for utility measurements. Voltage sag data gathering is an option on some newer utility substation relays and meters, so it wouldn't hurt to ask.
I would avoid the term "power loss" in this context. It may be confused with losses that are associated with current flowing through resistance (I²R losses).
RE: Power Loss Terminology?
Typically computer type equipment will continue to work if the outage is less than one cycle. Lighting on the other hand may sustain longer outage.
If you are a user Refer to ITIC or perviously known CBEMA curve that defines duation of a power outage that is accetable for computer equipment. Since most facilities now a days have them as critical equipment, this 'definition' will apply to most users.
Most utility compnay will only call it an outage if they fail to restore power by automatic switching. So if a reclosure closed and holds in third attempt to clear a temporary fault, all of user equipment may be down, but utility compnay might say it was not an outage.
So the answer is it depends.....
RE: Power Loss Terminology?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Power Loss Terminology?
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Power Loss Terminology?
The only option is to use a sophisticated recording instrument yourself (RPM, Dranetz/BMI, etc) to show them what is happening at you facility.
BTW, the word 'transient' is typically used (in my experience, anyway) for a short (micro-to-milli-second) disruption, also called a 'spike', and typically caused by switching events.
Words used for longer-term events are 'sags' or 'surges', which describe voltage decreases and increases, respectively, over time spans of several cycles to minutes or hours.
An 'outage' has, I believe, been explained already.
RE: Power Loss Terminology?
Also thanks to everyone else who posted.
RE: Power Loss Terminology?
RE: Power Loss Terminology?
It may make more sense to hire a testing compnay with this type of equipment to do the monitoring and write the report and help you present it to NStar with your concerns.
RE: Power Loss Terminology?
RE: Power Loss Terminology?
RE: Power Loss Terminology?
Also, many of the newer relays (Schweitzer for example) have "event capture" capabilities that give sequence of events as well as magnitude and duration values for viewing whatever occurence you program it to look for. If your POCO doesn't have these, the relays themselves aren't that expensive either (particularly if you can justify the expense by adding in their protective capabilities).