Author Topic: Brownout Duration  (Read 4430 times)
wattMaster
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Brownout Duration « on: August 16, 2016, 04:07:26 PM » Author: wattMaster
Here's a mystery:
There's a storm outside, and lightning strikes are causing "brownouts", where the AC/Mains power temporarily goes out for a split second.
A brownout just happened, and it made my preheat fluorescent billiard light turn off and restart, but the brownout did not turn the portable air conditioner off.
What's the duration needed to turn the portable air conditioner off? And what does this tell us about the billiard light?
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Medved
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Re: Brownout Duration « Reply #1 on: August 16, 2016, 04:20:12 PM » Author: Medved
The portabvle airco may have quite large inertia in the compressor (or it may just have been not running at that time), so it haven't slowed down to need complete restart. So it depends on the electronic, how long hold off time has it's supply. It is not that uncommon for these to cover even a second interruptions. What is really needed to shut the airco down is the reset of the controller. If the controller didn't reset (e.g. the voltage was still above the reset threshold), the unit continues operating as nothing have happened at all...
For the arc discharges on a series choke (and/or HX ballast) even a single missing halfwave tends to extinguish the arc, so the starters had just restarted the lamps.
For the brownout and/or interruption to be really visible (on incandescents,...), it has to be at least 100ms long.

The cause may have been wires striking against each other in the strong winds, or an arc struck on some spark gap arrester (and then got extinguished by the network protection system in the substation briefly interrupting the current delivery)
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Ash
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Re: Brownout Duration « Reply #2 on: August 16, 2016, 04:25:22 PM » Author: Ash
Brownouts are caused by secondary effects on the line - shorts, either caused by flashovers as result of lightning strike or of powerlines hitting each other (Phase A wire hit Phase B wire etc) from storm winds. As long as the short circuit lasts, before it goes out on its own or is interrupted by some breaker at the substation. (In many power lines measures are set to limit the short circuit current of Phase to Earth, and this way reduce the secondary effects caused by flashovers, and let the arcs go out without tripping the line)

Duration of brownouts you can see you can probably estimate, atleast to order of magnitude.. which is not bad precision for many estimations of "why"

I have some charts about lightning strikes and their duration if you are interested, but none about brownouts. There is no relation between that and the duration of brownouts



The air con reaction depends on quite some stuff that is related to your unit (the max torque the motor can provide, the momentum of spinning parts - how long it takes to stop, the impedance of the circuit feeding the unit) and the state in which it was interrupted (pressure of the refrigerant it had built up to that moment, therefore the torque the motor will have to restart against)

The light depends on some factors of its own, including your specific lamp and ballast and starter used, and the line voltage

In short, too many parameters to get some usefull relation or conclusions out of it
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Re: Brownout Duration « Reply #3 on: August 16, 2016, 04:30:01 PM » Author: wattMaster
The portabvle airco may have quite large inertia in the compressor (or it may just have been not running at that time), so it haven't slowed down to need complete restart. So it depends on the electronic, how long hold off time has it's supply. It is not that uncommon for these to cover even a second interruptions. What is really needed to shut the airco down is the reset of the controller. If the controller didn't reset (e.g. the voltage was still above the reset threshold), the unit continues operating as nothing have happened at all...
For the arc discharges on a series choke (and/or HX ballast) even a single missing halfwave tends to extinguish the arc, so the starters had just restarted the lamps.
For the brownout and/or interruption to be really visible (on incandescents,...), it has to be at least 100ms long.

The cause may have been wires striking against each other in the strong winds, or an arc struck on some spark gap arrester (and then got extinguished by the network protection system in the substation briefly interrupting the current delivery)
But aren't the wires insulated? I always thought the wires going across utility poles had insulation to protect from shocks.
It seems like utility companies have to be quick to stop any accidents in making the sine wave, or people would be complaining about restarting fluorescents.
Another Question: My photoelectric switch says it has a maximum wattage of 400 Watts with fluorescent, but 500 With incandescent.
Are they talking about power factor? Could you rely on the incandescent rating if you use a high power factor ballast? Would it be possible to use a HID ballast on it?
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Medved
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Re: Brownout Duration « Reply #4 on: August 16, 2016, 05:09:42 PM » Author: Medved
But aren't the wires insulated? I always thought the wires going across utility poles had insulation to protect from shocks.

The insulation is the air (unless they touch each other), it is the leas expensive, but one of the most robust insulation material (even with flashover, it 100% regenerates, no degradation).
The protection against shock is their position (they are high enough, so you can not touch them). The minimum height is based on the maximum height of the vehicles underneath, the possible sag due to wind, heat or other expected causes and the height is regularly checked during inspections (just a trained technician's look is accurate enough, the standards count on rather large tolerances). The pole design and wire spacing should ensure the wires actually do not touch each other (nor approach so much to cause a flashover) within required conditions (a minimum wind speed is one of them), but when the area is hit by wind way in excess what the design count on, the wires may swing so wildly they may touch each other and so cause these disruptions. In any way, the protection system should ensure the thing remains safe...


It seems like utility companies have to be quick to stop any accidents in making the sine wave, or people would be complaining about restarting fluorescents.

If that happens only during heavy storms, no one sane would be ever complaining...
With such weather normal people are just happy the infrastructure didn't get damaged so the service is working and nothing got damaged by overvoltage or so after the storm and even most of the time during the storm...
Of course, normal everyday weather should not cause these problems, but an exceptional weather may do so.

Another Question: My photoelectric switch says it has a maximum wattage of 400 Watts with fluorescent, but 500 With incandescent.
Are they talking about power factor? Could you rely on the incandescent rating if you use a high power factor ballast? Would it be possible to use a HID ballast on it?

It is not only about power factor, but as well about an inrush current or possible overvoltages when breaking the circuit.
The incandescents are resistive loads, so they pose no severe power ON inrush, nor any power OFF overcvoltage at all, so therefore it means nop extra contact loading at all.
The capacitive loads (ballasts compensated by a capacitor plain parallel to the mains input) exhibit nearly a short circuit current inrush peak (causing arcing and possible contact welding when switching ON), ballasts with inductive front end (practically all others) do exhibit overvoltage spike, so arcing when the relay breaks the circuit.
The energy of these things is usually related to the apparent power drawn by the circuits, so the robustness of the switching elements to handle these events is usually rated by the apparent power level (the "VA's").

Note, these inductive and capacitive effects are wide band peak events, so inductive can not compensate the capacitive and vice versa (the power factor is compensated), so you have to sum up all loads and then compare to the switch rating.

So if the switch rating says "400W fluorescent", it means it may control non-resistive load up to 400VA, so at 120V it means loads with up to 3.5A line current.
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Re: Brownout Duration « Reply #5 on: August 16, 2016, 05:12:58 PM » Author: wattMaster
Interesting. There goes my dream of potentially having a motion detector high bay.
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Ash
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Re: Brownout Duration « Reply #6 on: August 16, 2016, 05:17:01 PM » Author: Ash
Use a contactor
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Re: Brownout Duration « Reply #7 on: August 16, 2016, 05:17:43 PM » Author: wattMaster
Use a contactor
What's a contactor?
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Re: Brownout Duration « Reply #8 on: August 16, 2016, 05:24:58 PM » Author: Ash
Relay, one that is used for switching big loads in electrical installation. The relay coil (drawing little current) is controlled by the detector module, the contacts switch the high power load
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Re: Brownout Duration « Reply #9 on: August 16, 2016, 05:25:22 PM » Author: Medved
Interesting. There goes my dream of potentially having a motion detector high bay.

Wait a minute: You wanted to use a motion detector for an HID? That would kill it very quickly, just because it is so frequently switching ON and OFF.
The motion detector may be used with HID's to switch over from reduced to full power, but that means controlling just either a logic control input of the ballast or a relay (anyway, you would need an extra controller taking care of the initial 15minutes full power warmup, as well as dimming down ramping to prevent the lamp from extinguishing). In all of these cases the contact current through the motion sensor contacts would be just few mA, the main power is then handled by the ballast/dimming controller and has nothing to do with the motion sensor...


Contactor is a kind of big relay, a high load switch (10's A up to 10's kA ) controlled by a low current electromagnet (100mA's till some A's inductive)
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Re: Brownout Duration « Reply #10 on: August 16, 2016, 05:29:45 PM » Author: Ash
Many of the motion detector kits allready have built in timer for "ON time after momentary detection", that can be set up for quite wide time range. If that is not enough, an additional stairs lighting timer device can be used (which might possibly also substitute the contactor)
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Re: Brownout Duration « Reply #11 on: August 16, 2016, 05:33:52 PM » Author: wattMaster
I know my motion detector can go to at least 20 Minutes.
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Re: Brownout Duration « Reply #12 on: August 16, 2016, 05:44:10 PM » Author: Medved
Many of the motion detector kits allready have built in timer for "ON time after momentary detection", that can be set up for quite wide time range. If that is not enough, an additional stairs lighting timer device can be used (which might possibly also substitute the contactor)

The HID's are designed for 10hours/ignition or so, even the 20 minutes or even a hour is way too short to extinguish the lamp.
The thing is, there could well be a hour without anyone moving there (so the lights at full power consuming unnecessary power), while just 10 seconds after the timer expires someone walks in and the HID's won't be even physically able to light (hot restrike time). And with most of such places, leaving the lamps burning all the time would mean the same consumption anyway.
Therefore for HID's the motion detectors are used to just control the dimming. Then it could well be set to quite short time (few minutes), so when there is nobody, really keep the system on reduced power and yet the lamp will start only once a day and the light would be restored rather immediately any time anyone enters (OK, the color may be shifted before it warms back up, but that is minor thing compare to 20 minutes of hot restrike darkness).
That is, if you really insist on HID's.
Otherwise I would go either for programmed start fluorescents (really the decent programmed start ballasts rated for these sensors, not the PTC based toys) and/or a LED (if you want a real low power illumination job).
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Re: Brownout Duration « Reply #13 on: August 16, 2016, 05:46:43 PM » Author: wattMaster
Many of the motion detector kits allready have built in timer for "ON time after momentary detection", that can be set up for quite wide time range. If that is not enough, an additional stairs lighting timer device can be used (which might possibly also substitute the contactor)

The HID's are designed for 10hours/ignition or so, even the 20 minutes or even a hour is way too short to extinguish the lamp.
The thing is, there could well be a hour without anyone moving there (so the lights at full power consuming unnecessary power), while just 10 seconds after the timer expires someone walks in and the HID's won't be even physically able to light (hot restrike time). And with most of such places, leaving the lamps burning all the time would mean the same consumption anyway.
Therefore for HID's the motion detectors are used to just control the dimming. Then it could well be set to quite short time (few minutes), so when there is nobody, really keep the system on reduced power and yet the lamp will start only once a day and the light would be restored rather immediately any time anyone enters (OK, the color may be shifted before it warms back up, but that is minor thing compare to 20 minutes of hot restrike darkness).
That is, if you really insist on HID's.
Otherwise I would go either for programmed start fluorescents (really the decent programmed start ballasts rated for these sensors, not the PTC based toys) and/or a LED (if you want a real low power illumination job).

I would choose programmed start fluorescent for this application.
I like to make plans for theoretical lighting installations, and this one would be a storage room with 5 2-lamp F32T8 fluorescent troffers.
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Re: Brownout Duration « Reply #14 on: August 17, 2016, 01:32:51 PM » Author: hannahs lights
I remember in the factory I worked in we had a fault in the local substation it would cause a brownout of maybe half to one second and some fluorescents would go out completely and then restrike others would just dim a lot this happened even across fittings fed from the same phase so really its just down to individual tubes how good the cathodes are and how sensitive the starters were.
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