Ask me about industrial electricity 2: electric boogaloo

The Something Awful Forums > Discussion > Ask/Tell > Ask me about industrial electricity 2: electric boogaloo

Three-Phase: Aug 5, 2006; by zen death robot

One thing I also see on drives and exciters are cable mechanisms - where there's a circuit breaker inside a cabinet, but it's connected via a cable or lever to an operating handle on the outside of the cabinet. The handle is also interlocked so you cannot open the cabinet without throwing the handle to the OFF position.

_{On most doors, that interlock is easily defeated with a small screwdriver so an engineer can enter the cabinet while it's energized. Same thing with motor control center bucket doors.}

Three-Phase fucked around with this message at 14:46 on Feb 18, 2012

# ? Feb 18, 2012 14:40

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# ? May 11, 2024 15:50

Guy Axlerod: Dec 29, 2008

Three-Phase posted:

As an aside: I was joking around with co-workers about how cool it would be to have an ordering option to include an ABB engineer with the larger drives.

"So there's the new Megadrive... wait, who the hell's that guy?"
"Oh, he's Paul. You add an '-ENG' to the end of the part number, and they also ship a engineer in that other crate."
"Hallo! Ich kam mit dem Hochspannungs-Laufwerk!"
"I can't understand a word he says, but he showed me how to replace the IGBTs."

I work with a guy who used to do ABB field service. I'd be happy to put him in a box and ship him out to you.

(He's really not that bad, just tells some bad jokes sometimes.)

# ? Feb 18, 2012 15:09

Stonelegs: Apr 15, 2003; I'll have a coke...

We've got a few larger orders with ABB and all the boxes say "DO NOT OPEN UNLESS ABB REPRESENTATIVE IS PRESENT" or somesuch. What's so special about their poo poo?

# ? Feb 19, 2012 03:21

Three-Phase: Aug 5, 2006; by zen death robot

Stonelegs posted:

We've got a few larger orders with ABB and all the boxes say "DO NOT OPEN UNLESS ABB REPRESENTATIVE IS PRESENT" or somesuch. What's so special about their poo poo?

I don't know, but lot of the equipment isn't cheap. You want four galvanic isolated 4-20mA analog input channels with 12 bit resolution? That's about a thousand dollars for an AI825 S800 I/O card, or $250 per channel.

I'm not going to go into details for several reasons, but you can easily fill a cubic-foot cardboard box with nearly a hundred thousand dollars worth of ABB's higher-end stuff - things that are the brains and communication hubs for their automation equipment.

It's odd too, you have a little cardboard box smaller than a half a loaf of bread containing a device that costs over $10,000. If I ran ABB, those would ship in a ruggedized attache case, not a $1 cardboard box. But that's just me.

Three-Phase fucked around with this message at 04:21 on Feb 19, 2012

# ? Feb 19, 2012 04:15

Frozen Horse: Aug 6, 2007; Just a humble wandering street philosopher.

Three-Phase posted:

In a lot of installations, the circuit breaker and relay control power runs off 120VDC. This is so you can have a bank of batteries to run the breakers even if there's a power outage, and if need be, you can get car batteries out of ten people's cars and operate the breakers in a pinch. In real life, the circuit breakers and critical power systems in Jurassic Park would probably have been run off 120VDC, so that whole priming thing would have been unnecessary. The 120VDC system allows a facility to "pull itself up by its bootstraps" in the event of a power failure.

Why not just drive the controls off of the line feeding the breaker (appropriately stepped-down)? If it's dead, then the breaker controls are a moot issue.

Three-Phase posted:

It's odd too, you have a little cardboard box smaller than a half a loaf of bread containing a device that costs over $10,000. If I ran ABB, those would ship in a ruggedized attache case, not a $1 cardboard box. But that's just me.

That's one of the things I like about one of the instruments we've got around the lab (an oxygen-content sensor). It was in that price range, and took several months to ship for reasons not exactly clear, but when it arrived it came in a very spy-movie style aluminium briefcase.

# ? Feb 20, 2012 04:04

Meow Meow Meow: Nov 13, 2010

DuckConference posted:

All of the big buildings here seen to have 347V lighting, is this only a thing in canada?

I'd assume so, since 347V is single phase of a 600V three phase system. USA would be 277V, if they were to use a single phase of their 460V system.

# ? Feb 20, 2012 04:28

Three-Phase: Aug 5, 2006; by zen death robot

Frozen Horse posted:

Why not just drive the controls off of the line feeding the breaker (appropriately stepped-down)? If it's dead, then the breaker controls are a moot issue.

One important thing to consider is that larger breakers require electrical power to both close and open. (ABB does have a new medium-voltage AMVAC breaker that stores electricity in a capacitor and can be set to automatically open the breaker in a power failure, or remain closed, or trip after a small time delay.)

Usually on low-voltage equipment, you have a circuit breaker and a contactor to control a load. The contactor acts like a switch, and the breaker provides isolation and protection from shorts (and sometimes overloads, ground faults, etc.). On medium-voltage equipment, the circuit breaker is remotely controlled and performs double duty.

Let's have a possible scenario here:

code:

Bus: 13.8kV (assume infinite bus, transformer primary breaker omitted)
 |
3/0 triplex cable (plus ground), shielded and cable tray rated, 15kV class 
 |
Transformer A: 13.8kV to 2400V, 5MVA (209A primary, 1200A secondary)
 |
Bus bars
 |
1200A A-MAIN Circuit breaker and protective relay 
 |
Breaker A-1: GE 469 Multilin (1000 HP induction ventilator fan, 225FLA, 6xFLA starting)
Breaker A-2: GE 469 Multilin (1000 HP induction ventilator fan, 225FLA, 6xFLA starting)
Breaker A-3: GE 469 Multilin (1000 HP induction water pump, 225FLA, 6xFLA starting)
Breaker A-4: GE 469 Multilin (1000 HP induction water pump, 225FLA, 6xFLA starting)
Breaker A-5: SEL 501(A) (To transformer A-5, 2400V to 480/277, 500kVA, 120A primary)
Breaker A-6: SEL 501(B) (To transformer A-6, 2400V to 208/120, 500kVA, 120A primary)
Breaker A-7: ? Relay (synchronous condenser for PF correction of Bus A)

Typical operations is to start one of the large motors at a time, with at least 30 seconds between closing each of the breakers enforced by the PLC.

So lets all the protective relays are run off the bus power. You have a power failure when a squirrel (let's call him Todd) is violently electrocuted across two phases somewhere else in the power system, and the upstream breaker opens. Suddenly all your motors stall.

After three unsuccessful retries, the upstream recloser faults out. Your motors coast to a stop and an eerie quiet fills your plant. A half-hour later eventually the charred and burning body of Todd is removed from where he initially was, clearing the fault path. The upstream power is restored.

Now your "A" transformer is trying to start four induction motors at once because all the breakers on the bus are still closed. Instead of pulling about 900A, your four motors trying to start are instantaneously trying to pull over 5000A. This is also ignoring any loads connected to the A-5 and A-6 transformer, as well as the synchronous condenser attached.

A few things could happen: The Multilins detect that both the bus voltage has now dramatically dropped since the transformer is saturating, and the motors are having a really hard time starting, and trip out all the motors. The 1200A bus main breaker may also trip out before the Multilins even have a chance to act.

Remember, in this scenario the breaker cannot open if it has no control power. The only option would be for one of the workers to suit up and manually trip breakers A1-7 on the bus, then close breaker A-MAIN, and then start the motors and loads up again one by one. They also might be delayed because the Multilins may have a time delay in them to prevent the motors from restarting immediately after having a really hard, failed start. (Unless you jumper the emergency restart pins in the back, in which case you'll want management to sign something that says if the motors get damaged, it's not your fault.) So now things are a mess, and Todd is joking around in squirrel heaven about how he stopped production at the plant.

-

Grover, if you could, please check/critique my scenario here, I want to make sure what I'm describing is accurate.

Three-Phase fucked around with this message at 15:07 on Feb 20, 2012

# ? Feb 20, 2012 14:44

grover: Jan 23, 2002; PEW PEW PEW

People don't think often about it because our residential panels are 100% mechanical, but power is rather critical to the electrical distribution of industrial systems, and not just in the obvious sense- when the power goes out, a number of things need to happen automatically, including opening/closing breakers, and starting the emergency generator. Most switchgear has a battery bank that operates the PLC (industrial computer) that monitors power and open/closes breakers. If those batteries are dead, nothing happens until power is restored.

Three-Phase's scenario is typical of a large industrial process. You've got a 1200Amp main breaker feeding four motors that each draw 225Amps, and a couple transformers supplying other loads in the building (lights, computers, smaller pumps, etc.) The problem here is that while running, there's a lot of magnetic forces acting against the current you put into it, but when stopped, motors are just coils of copper wire, and are essentially a short circuit- it's why the lights in your house dim when your air conditioner starts, and in this example, each motor draws 1350A on startup! It's only briefly, though, and transformers and transmission line are designed to handle it, and will run OK even though 1350A>1200A. But you don't want to start all these giant motors at the same time, or you're going to have problems! So the PLC ensures you only bring in one motor at a time and let it come up to speed before starting the next. Even in this case, you probably don't want to run all four 1000hp motors at once; I'd wager two of the four motors are redundant so that the operation doesn't stop even if one motor breaks or is taken offline for maintenance.

Incidentally, one of the worst things you can do to a motor is cut power, wait a few moments for it to slow to a random point, and then restore power- if you bring it in out-of-phase, you can do all sorts of damage. Normally, there are other protective systems on the motors that will detect this and trip them offline, but it's still not good.

grover fucked around with this message at 19:24 on Feb 20, 2012

# ? Feb 20, 2012 15:29

Three-Phase: Aug 5, 2006; by zen death robot

^ - I should create a one-line for a hypothetical industrial plant we can use for explaining and looking at different scenarios. I'm thinking some interesting stuff like generators, PF correction, metering, bus ties and backfeeding, etc.

One other problem is opening the breaker of a synchronous (not an induction) motor. My understanding is that if you have a running synchronous motor where:

1. The breaker is CLOSED and the motor is running at synchronous speed
2. The field discharge resistor contact is OPEN
3. The exciter is ACTIVE

And you suddenly open the breaker, you must immediately CLOSE the field discharge resistor contractor and DEACTIVATE/FAULT the exciter. Otherwise the synchronous motor will be acting as an open-circuited generator, and that's extremely bad on the windings and other equipment. Basically you can induce an insanely high voltage on the stator windings that can potentially blow through and short the stator windings. Then your $x0,000 to $x00,000 motor is effectively trashed and needs to be replaced or rewound.

An additional problem is if you OPEN the breaker for a large synchronous generator. Even if you kill the excitation on the rotor, you've suddenly lost a load. It's like if you are cruising down the road at 70 miles per hour when suddenly you shift into neutral while still pushing down on the gas pedal. There's nothing to limit the speed of the engine, all that energy goes into increasing the speed that the shaft rotates. So that means if you don't stop the prime mover, like blowing off steam going through a turbine or bypassing the turbine, the thing will accelerate until it gets damaged or destroyed. If a turbine flies apart, it can kill people too. I've heard of metal parts being thrown through ceilings and floors and walls like a howitzer shell.

I think the only real difference between a synchronous motor and a synchronous generator is that the synchronous motor will have some starting means (such as a pony motor or armitissour windings (an induction motor within the synchronous motor, basically) where the generator doesn't need that.

(Sorry, it's an old habit to capitalize verbs/statuses/actions when talking about this stuff.)

Three-Phase fucked around with this message at 18:25 on Feb 20, 2012

# ? Feb 20, 2012 18:16

helno: Jun 19, 2003; hmm now were did I leave that plane

Here are a few things in regards to excitation of syncronous generators.

The difference in excitation current required to make rated terminal volts at no load is way less than is required at full load. So if you dump the load the terminal voltage will increase alost instantly.

The time constant for rotor current is measured in whole seconds so it takes a really long time to raise or lower things. That field dicharge resistor will drop the rotor field to nothing pretty fast.

On the exciters I work on it is not actually a breaker but a pair of SCR's that initiate dexcitation. The resistor is actually just a big folded sheet of steel.

# ? Feb 20, 2012 20:11

Three-Phase: Aug 5, 2006; by zen death robot

helno posted:

Here are a few things in regards to excitation of syncronous generators.

The difference in excitation current required to make rated terminal volts at no load is way less than is required at full load. So if you dump the load the terminal voltage will increase alost instantly.

The time constant for rotor current is measured in whole seconds so it takes a really long time to raise or lower things. That field dicharge resistor will drop the rotor field to nothing pretty fast.

On the exciters I work on it is not actually a breaker but a pair of SCR's that initiate dexcitation. The resistor is actually just a big folded sheet of steel.

Ahh, I didn't realize the time constant was so large on the generators. But of course you still don't want to inadvertently have the FDR out of the circuit or the exciter on at that point, right?

I believe the exciters I've worked on have both a mechanical two-pole contactor (to the FDR) as well as a set of SCRs in parallel hooked up to a firing board. Those SCRs discharge the field if there's a really rapid boost in voltage, I think it's set to about half of where the field would flash over at an arc gap. If that fails, there's an arc gap that can flash over across the field.

The ones I've worked on typically have an FDR from about 1-10 Ohms. Forgot how many kW they're rated at, they're probably really overbuilt.

Three-Phase fucked around with this message at 21:20 on Feb 20, 2012

# ? Feb 20, 2012 21:17

grover: Jan 23, 2002; PEW PEW PEW

Three-Phase posted:

Ahh, I didn't realize the time constant was so large on the generators. But of course you still don't want to inadvertently have the FDR out of the circuit or the exciter on at that point, right?

Depends on the generator and the governor settings. "Small" diesel generators react a lot more quickly.

# ? Feb 20, 2012 23:12

Cute as heck: Nov 6, 2011; Cutie Pie Swag~

Hey 3P, I have a question

I miss you

Love, DDL

# ? Feb 20, 2012 23:26

Three-Phase: Aug 5, 2006; by zen death robot

Cute as heck posted:

Hey 3P, I have a question

I miss you

Love, DDL

Oh poo poo, you're Daniel Day Lewis, right?

I didn't recognize that name even after checking your post log. So I sort of sent a moderator report saying that you were being a "creepy motherfucker". So hopefully a mod reads this, and understands it was Dan, and you were not, in fact, being a "creepy motherfucker". Sorry about that! What can I say? I'm an idiot.

Three-Phase fucked around with this message at 00:40 on Feb 21, 2012

# ? Feb 21, 2012 00:01

moana: Jun 18, 2005; one of the more intellectual satire communities on the web

Take the kissing to IRC and stop sending me reports, you dumbshits, or I swear to christ I'll send you to Pet Island < :mad:

# ? Feb 21, 2012 01:47

zapradon: Feb 21, 2012

I just found this wonderful thread, and have read nearly all of it (I think.)

Earlier, there was some discussion of Powerware UPS. I was recently called to do some troubleshooting in a data center with a wildly mixed setup of various kinds of UPS'. One Powerware 9395 had very strange CT readings through out the cabinet. Moving the CT along any of the cables or to different cables would cause the readout to swing wildly, as much as 20-2000A. We tried several other CT's and a clamp-on, with the same results.

Other 9395's on the same floor were also a bit squirrely, but not quite as bad as that one.

Other floors were normal, so I'm suspecting some strange ground/neutral issue, but I'm only a lowly electronics engineer. Any ideas?

Thank you for this terrific thread.

# ? Feb 21, 2012 19:54

Three-Phase: Aug 5, 2006; by zen death robot

So wait, when you take a clamp ammeter and move it to different locations along a power cable, you get varying readings? Is this cable somehow shielded or triplexed?

I'm wondering this - is your clamp ammeter true-RMS? Have you looked at the output waveforms from the UPS on a scope?

# ? Feb 21, 2012 21:34

SeaBass: Dec 30, 2003; NERRRRRRDS!

zapradon posted:

I just found this wonderful thread, and have read nearly all of it (I think.)

Earlier, there was some discussion of Powerware UPS. I was recently called to do some troubleshooting in a data center with a wildly mixed setup of various kinds of UPS'. One Powerware 9395 had very strange CT readings through out the cabinet. Moving the CT along any of the cables or to different cables would cause the readout to swing wildly, as much as 20-2000A. We tried several other CT's and a clamp-on, with the same results.

Other 9395's on the same floor were also a bit squirrely, but not quite as bad as that one.

Other floors were normal, so I'm suspecting some strange ground/neutral issue, but I'm only a lowly electronics engineer. Any ideas?

Thank you for this terrific thread.

Any mechanical loads on the buses feeding those 9395s?

# ? Feb 22, 2012 01:16

grover: Jan 23, 2002; PEW PEW PEW

zapradon posted:

I just found this wonderful thread, and have read nearly all of it (I think.)

Earlier, there was some discussion of Powerware UPS. I was recently called to do some troubleshooting in a data center with a wildly mixed setup of various kinds of UPS'. One Powerware 9395 had very strange CT readings through out the cabinet. Moving the CT along any of the cables or to different cables would cause the readout to swing wildly, as much as 20-2000A. We tried several other CT's and a clamp-on, with the same results.

Other 9395's on the same floor were also a bit squirrely, but not quite as bad as that one.

Other floors were normal, so I'm suspecting some strange ground/neutral issue, but I'm only a lowly electronics engineer. Any ideas?

Thank you for this terrific thread.

20-2000A... but at what frequency?

Powerware 9395 are transformerless UPS, which rectify 480VAC line voltage to 548VDC (or higher) when charging, and then invert battery voltages as low as 432VDC back up to 480VAC... all without transformers. They instead use motherfucking voodoo magic, by switching the inverter and rectifier IGBTs at 10s of kHz frequencies, and use this in conjunction with small inductors as boost converters to regulate the output voltage and current. Your clamps were likely seeing some of the high frequency current, which has high reactance (and high impedance) on straight lengths of cable, and I would imagine would give you highly variable readings like you got. I'll have to try this with my oscope next chance I get and see what it looks like

# ? Feb 22, 2012 01:26

zapradon: Feb 21, 2012

grover posted:

20-2000A... but at what frequency?

Powerware 9395 are transformerless UPS, which rectify 480VAC line voltage to 548VDC (or higher) when charging, and then invert battery voltages as low as 432VDC back up to 480VAC... all without transformers. They instead use motherfucking voodoo magic, by switching the inverter and rectifier IGBTs at 10s of kHz frequencies, and use this in conjunction with small inductors as boost converters to regulate the output voltage and current. Your clamps were likely seeing some of the high frequency current, which has high reactance (and high impedance) on straight lengths of cable, and I would imagine would give you highly variable readings like you got. I'll have to try this with my oscope next chance I get and see what it looks like

I did some quick testing on a 9315 I had access to elsewhere, and the rectifier runs at about 12.5kHz, and the inverter at about 24kHz. There were noise peaks of 3-5V in the mid frequencies. However, that one didn't have the weird currents. There are confusing warnings in the manual about ground-neutral connections, but I have no idea if they could cause what we were seeing. Some combination of incorrectly wired ground/neutral connections, perhaps even interacting with derived neutrals on PDUs? You're right. It's voodoo.

# ? Feb 22, 2012 01:55

zapradon: Feb 21, 2012

SeaBass posted:

Any mechanical loads on the buses feeding those 9395s?

No telling. It was a client site that apparently has each customer installing their own UPS's (a nightmare scenario, it sounds like to me.)

The site manager was unable to find site wiring schematics for us to look at.

# ? Feb 22, 2012 01:59

grover: Jan 23, 2002; PEW PEW PEW

zapradon posted:

I did some quick testing on a 9315 I had access to elsewhere, and the rectifier runs at about 12.5kHz, and the inverter at about 24kHz. There were noise peaks of 3-5V in the mid frequencies. However, that one didn't have the weird currents. There are confusing warnings in the manual about ground-neutral connections, but I have no idea if they could cause what we were seeing. Some combination of incorrectly wired ground/neutral connections, perhaps even interacting with derived neutrals on PDUs? You're right. It's voodoo.

9315 is older an technology transformer-based UPS with SCR rectification (inherently 120Hz switching w/big cap bank to smooth it), and though it does a similar function, works entirely differently on the inside. 9390 and 9330 are similar to 9395, though, if you have access to those.

grover fucked around with this message at 02:10 on Feb 22, 2012

# ? Feb 22, 2012 02:04

zapradon: Feb 21, 2012

Three-Phase posted:

So wait, when you take a clamp ammeter and move it to different locations along a power cable, you get varying readings? Is this cable somehow shielded or triplexed?

I'm wondering this - is your clamp ammeter true-RMS? Have you looked at the output waveforms from the UPS on a scope?

We actually used several different CT's including differential, true-RMS, and others. Same results with all. Cable is straight-up stranded cable, I'm guessing 0 or 1AWG-ish (I looked but can't remember now.)We're planning a trip back with a rogowski coil next I think.

# ? Feb 22, 2012 02:05

zapradon: Feb 21, 2012

grover posted:

9315 is older an technology transformer-based UPS with SCR rectification (60Hz w/big cap bank to smooth it), and though it does a similar function, works entirely differently on the inside. 9390 and 9330 are similar to 9395, though, if you have access to those.

Oh sorry, thinking about too many things at once. It was a 9390, transformerless.

I'm told it's fairly similar to the 9395.

# ? Feb 22, 2012 02:10

grover: Jan 23, 2002; PEW PEW PEW

zapradon posted:

Oh sorry, thinking about too many things at once. It was a 9390, transformerless.

I'm told it's fairly similar to the 9395.

Yeah, the 9390 and 9395 use virtually identical technology. I think they even share some of the same controller cards. And you do need to be very careful to handle the neutral properly; they have a dedicated set of IGBTs to derive the neutral voltage, and it can be thrown all out of whack of you don't provide a solidly grounded wye source.

Edit: for those of you trying to follow along, this is what we're talking about.

grover fucked around with this message at 02:25 on Feb 22, 2012

# ? Feb 22, 2012 02:19

Three-Phase: Aug 5, 2006; by zen death robot

You have to be REALLY CAREFUL if this thing is already online and powering mission-critical loads, but can you bypass the UPS? I believe with some Powerware systems, there is an option that allows you to bypass the UPS so that you can do maintenance safely while your critical load is still energized. Just to make sure the problem is directly related to the UPS and not your power line.

You'll see these circuit breakers marked "MBP and MIS". Be sure to read Eaton's instructions extremely carefully if you are running a critical load like a production server, an iron lung, nuclear reactor control rod servo motors, etceteras so you don't get in trouble/kill people.

Grover, isn't there also a way in software to bypass the UPS, or is that to just shut it down? (The last time I shutdown an Eaton Powerware 93XX at work, despite running all the required paperwork, resulted in some "unexpected fun".)

Three-Phase fucked around with this message at 03:53 on Feb 22, 2012

# ? Feb 22, 2012 03:41

zapradon: Feb 21, 2012

grover posted:

Yeah, the 9390 and 9395 use virtually identical technology. I think they even share some of the same controller cards. And you do need to be very careful to handle the neutral properly; they have a dedicated set of IGBTs to derive the neutral voltage, and it can be thrown all out of whack of you don't provide a solidly grounded wye source.

Edit: for those of you trying to follow along, this is what we're talking about.

From what I've been seeing earlier in this thread, it's not inconcievable that they could be trying to run on delta supplies, or have grounds wrong, I suppose.

What sorts of "out of whack" might you see? We've also had cases of supposedly isolated monitor gear blowing up when they throw the battery breakers. So far all of this has been on 9395's only.

# ? Feb 22, 2012 03:46

zapradon: Feb 21, 2012

Three-Phase posted:

You have to be REALLY CAREFUL if this thing is already online and powering mission-critical loads, but can you bypass the UPS? I believe with some Powerware systems, there is an option that allows you to bypass the UPS so that you can do maintenance safely while your critical load is still energized. Just to make sure the problem is directly related to the UPS and not your power line.

You'll see these circuit breakers marked "MBP and MIS". Be sure to read Eaton's instructions extremely carefully if you are running a critical load like a production server, an iron lung, nuclear reactor control rod servo motors, etceteras so you don't get in trouble/kill people.

We'll have to make some arrangements, but it might be possible. At this point, I'm trying to get an idea what symptoms I might see that would indicate a power problem, since we've been unable to duplicate it with what we've got so far, it's looking more and more like a potential site problem. These seem to be very noisy UPS' also, tho.

# ? Feb 22, 2012 03:52

Three-Phase: Aug 5, 2006; by zen death robot

Can you get a "real-deal" power quality meter like a Dranetz PowerVisa? That way you can see the actual output waveform for voltage, and you can also get current clamps up to 3kA. (For about, maybe $10-$15k for the meter, clamps, and software license.)

# ? Feb 22, 2012 03:55

grover: Jan 23, 2002; PEW PEW PEW

Three-Phase posted:

You have to be REALLY CAREFUL if this thing is already online and powering mission-critical loads, but can you bypass the UPS? I believe with some Powerware systems, there is an option that allows you to bypass the UPS so that you can do maintenance safely while your critical load is still energized. Just to make sure the problem is directly related to the UPS and not your power line.

You'll see these circuit breakers marked "MBP and MIS". Be sure to read Eaton's instructions extremely carefully if you are running a critical load like a production server, an iron lung, nuclear reactor control rod servo motors, etceteras so you don't get in trouble/kill people.

Grover, isn't there also a way in software to bypass the UPS, or is that to just shut it down? (The last time I shutdown an Eaton Powerware 93XX at work, despite running all the required paperwork, resulted in some "unexpected fun".)

It's not only possible, but standard practice to install redundant UPS systems so that you can secure one while operating on the other(s), and to have a maintenance bypass switch so that you can bypass the entire UPS system for major maintenance or replacement or whatever reason. (Most companies like to transfer from utility power to emergency generators while on maintenance bypass so that an errant utility failure doesn't take their facility down.) All high-end double conversion UPS systems also have what's called "static bypass", where a solid-state static switch (often in conjunction with a mechanical contactor) can engage in the event of an internal component failure and this ensure continuous power to the critical load, even if the UPS has failed. To transfer to maint bypass, you always place the UPS in static bypass first. Otherwise, the UPS would end up with the output feeding the input once the maint bypass breaker is closed, and possibly out-of-phase since the UPS output isn't necessarily paralleling the bypass input source (though it usually is). As maintenance is required on all model UPSs, transfers like this are routine and done safely all the time.

Transformerless UPS units present a new challenge in implementing this. Most notably, the lack of a transformer and single-model-economies-of-scale means lack of a 208V model 9395; they're all 480V. (As are comparably sized Liebert NX/NXL and APC Symmetra PX UPS.) Put a 208Δ-480Y step-up transformer on the input, and a 480Δ-208Y step-down on the output, and now you've fixed the voltages and have your neutral, but your maint bypass is 60� out-of-phase with your UPS's output and you get a nice big BANG when you try to transfer. In the old days, it was easy: you turn the first transformer backwards* and go 208Y-480Δ then 480Δ-208Y. +30� and -30� cancel, and you're in-phase. But you can't do this when you need a solidly grounded neutral. Therefore, you need to use custom-wound Δ-zigzagY transformers with 0� phase-shift to keep your UPS in-phase with maintenance bypass switch.

*To do it right, you'd get it custom-wound, as you always want the transformer primary coil inside the secondary for highest energy efficiency and lower magnetization current, though an off-the-shelf delta-wye wired-up backwards would work in a pinch.

grover fucked around with this message at 04:17 on Feb 22, 2012

# ? Feb 22, 2012 04:03

zapradon: Feb 21, 2012

Three-Phase posted:

Can you get a "real-deal" power quality meter like a Dranetz PowerVisa? That way you can see the actual output waveform for voltage, and you can also get current clamps up to 3kA. (For about, maybe $10-$15k for the meter, clamps, and software license.)

I've been agitating for a Fluke 435 without much success so far..

# ? Feb 22, 2012 18:18

SeaBass: Dec 30, 2003; NERRRRRRDS!

zapradon posted:

No telling. It was a client site that apparently has each customer installing their own UPS's (a nightmare scenario, it sounds like to me.)

The site manager was unable to find site wiring schematics for us to look at.

Yeah, it can definitely end up being a mess.

Site managers typically don't have much beyond what was originally installed. You might have better luck with the customer's electrical contractor for getting as-built one lines.

# ? Feb 22, 2012 18:44

grover: Jan 23, 2002; PEW PEW PEW

zapradon posted:

I've been agitating for a Fluke 435 without much success so far..

We've got a couple Fluke 435s and a Dranetz for power monitoring. They're bulky enough that I don't generally travel with it it unless I think I'm going to need it, which means I never have one when I do

So, I've started keeping a Fluke 345 in my tool bag now. Not quite as good as a 435, but still gives incredibly good info and I'm much more likely to actually have it handy. I keep flinging it around like it's a $20 multimeter, though, and am terrified I'm going to forget myself and smash it...

grover fucked around with this message at 00:04 on Feb 23, 2012

# ? Feb 23, 2012 00:01

Three-Phase: Aug 5, 2006; by zen death robot

The coolest thing I found in the Dranetz is that it can give you a FFT for:

-Voltage
-Current
-Power

What's amazing is that you can get a positive or negative value for harmonic power in watts. I think it looks at the phasors for current and voltage versus the fundamental. So you can see a load generating harmonic power and sending it back into the electrical power system. Not sure how accurate this is, but I think it gives you some idea of what's going on in the power system. The Dranetz will also give you a K-factor number.

Last time I saw that was on a 2400V system where I was seeing a minimal amount of harmonic power being generated by the load, like 500W of 5th harmonic versus about 5MW of fundamental.

Three-Phase fucked around with this message at 01:33 on Feb 25, 2012

# ? Feb 25, 2012 01:28

Three-Phase: Aug 5, 2006; by zen death robot

Ah, perfect. I just found the settings for doing split-phase monitoring. There's a system I'm working on where we have A, B, and C phase current transformers, but only phase A and B PTs.

# ? Mar 8, 2012 02:35

ncumbered_by_idgits: Sep 20, 2008

I have been an industrial electrician for fourteen years now, working in a plant that has 480 volt electrical service. I'm very familiar and comfortable with what I do every day.

That being said, the stuff you guys are talking about is way over my head. You all are some bad motherfuckers up in here.

# ? Mar 9, 2012 01:35

Three-Phase: Aug 5, 2006; by zen death robot

We've got 480V loads all over the place. Still gotta treat the low voltage stuff with the utmost respect because it's so common. What's scary is when you're inside a cabinet where you have a 600VDC source, and on the busbars are bolted two 800A fuses in parallel with one another.

If you're interested in big loads, here's a sort of cable I've been using:

15kV Triplex 2AWG to 750kcmil

I think that the bend radius for the 500kcmil triplex is over five feet. They bring it in on a spool that's about 10 feet in diameter and must weigh a ton.

Three-Phase fucked around with this message at 05:10 on Mar 9, 2012

# ? Mar 9, 2012 02:14

I heart bacon: Nov 18, 2007; It's burgin' time!

grover posted:

After all, in a recent poll of electricians, not one of them reported ever having received a fatal electric shock.

If anybody told me they had, I would be shocked! :downsrim:

Where I work, there is a lot of 480V 3 phase equipment and a half dozen or so 4160v motors. One of the things they taught us was to stay on the hinge side of a cabinet when closing a circuit. That way if there were an arc flash and the explosion threw the door open, you would still be protected from the flash.

# ? Mar 25, 2012 00:31

ncumbered_by_idgits: Sep 20, 2008

I work in a facility that is probably small and uncomplicated compared to what some of you guys are talking about here but I still have a question.

Just for reference, we have four buildings, one each:
480/3 - 800 amp service
480/3 - 1600 amp
240/3 - 600 amp
240/3 - 200 amp

I am curious what kind of attitude facilities of a similar size have in regard to electrical safety. I participate in a few online electrical forums and it seems that most of those guys are 70E "by the book" types. I feel however, that the members of those forums who don't agree with the prevailing opinion tend to keep their opinions to themselves for fear of ridicule.

I'd love to hear what it's like in the real world. I'll wait for a couple replies to post my experiences and thoughts. Thanks.

Edit: To be more specific, my question pertains to management rather than the guys in the plant.

ncumbered_by_idgits fucked around with this message at 02:09 on Mar 25, 2012

# ? Mar 25, 2012 01:33

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# ? May 11, 2024 15:50

grover: Jan 23, 2002; PEW PEW PEW

ncumbered_by_idgits posted:

I am curious what kind of attitude facilities of a similar size have in regard to electrical safety.

The attitude I've seen is one of widespread and chronic complacency. They'll wear PPE if you call them them out on it, but get pretty bitchy about it.

After all, the shock-hazard of a 2000A 208V panel is no different than a 120V receptacle. :suicide:

# ? Mar 25, 2012 01:46

The Something Awful Forums > Discussion > Ask/Tell > Ask me about industrial electricity 2: electric boogaloo

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