Busbar Short Circuit

Simple answer yes. Irrespective of the size, when you get ingress of water onto busbars there will be an audible bang

thank you for comment however, the matter is there is no a bang. there is only fire burned the panel. the operator said that he knew the fire not because a bang but he saw the fire in progress. could it happen? thanks

Yes, the higher the load at the time of the water entry the bigger the reaction. ( as per example, a 525V, 125A load makes a very loud bang). In your case the load was to low. I think, if you were at the panel you would have heard a crackle, this crackling would have set up heat and obviously started melting your components, before it tripped

Instead of assuming that it is possible that water has caused the fault, a through examination of the buss bar system and its surrounding environemt is necessarry. Could there be another cause, dust, metalic dust, infestation, etc.

Needles to say though, water should be never be allowed to get into the buss bar enviroment or any control panel, if this is happening you are asking for trouble.

If after examination you are still unsure what caused the fault, elimination is the next best answer. Ensure that the buss system can not get water ingress, If possible shut down the system and remove all residues from the buss system and then ensure that it remains clean and water free.

Cheers

Joe

Well, it did happen. So of course it could.

i want to say thank you again for comment. however, you said the example for 525V, 125A makes a very loud bang. My panel have 2000 A or 2KA. so i think it could be more loud bang if affected by water tripped. how about it? and how much the example of current or voltage if you said that i can heard the crackle if i stand near the panel? thanks and warm regard

Ok, then obviously only one phase was "watered" and it crackled and heated to the nearest earth.( obviously doesnt sound like a lot of moisture anyway) If water gets between two phases, it will be noisy, and persons at the panel will know about it.

You mentioned that the busbar is used for "low voltage". How low? For example a 24V busbar won't make a "bang" at all if shorted by water droplets.

thanks for comment. that is 400V busbar for LV Panel. could it burnt because of short circuit by the water droplets without a "bang"? thanks

Good day Benny, when water at busbar are, then sparkle, smokle & noise happen can. Seriously Benny, doesn't common sense and basic knowledge let you know why it "could it burnt". If not, then run as fast as you can & stay away from these busbars as you could be placing your life in serious jeopardy with the possibility of a fingergepokken, blitzenblinken g'explosion abouterhappen.

Once i deciphred this English, it made a lot of sense. Benny, heed the advice. As posted by myself, water can and will be noisy and destructive when in contact with loads of energy. You said there was water. End of story, whatever happened to your panel, silently or otherwise, water helped it along.

Benny,

If water droplets get into a bus-bar, the result will depend on the quantity and some bad luck!

The bangs that almost all are talking about do not occur every time. If the water ingress is small, the shorts will occur slowly and start to create a path on the insulators, and if the insulators are of the type that can carbonize, then the breakdown will occur progressively until there is enough heat generated to start burning the cables insulations etc. The load at the time of breakdown or the capacity of the bus-bar are irrelevant since the short will happen between the bars and between the bars and earth (body). The current flow will happen at maximum capacity of the protective devices upstream from the panel Bus-Bars.

The degree of mineral content of the water is a big factor.Pure distilled water is a very poor conductor of electricity.As the water dissolves minerals, it becomes more and more conductive, so a buildup of dirt from the bus bar to ground, when it becomes moist, can become a high resistance path to ground.

Tis will result in a slow buildup of heat, and eventually a short circuit.

The insulators for the busbar should be cleaned meticulously and regularly to prevent this.Any charred or burnt components should be replaced.Terminations should be sprayed with Glyptal Insulating enamel after proper torque values are applid to the hardware.

If in doubt, consult a local Quailified Electrician or Inspector.

HTRN

Dear Benny, It is not possible to get busbar short circuited just by water droplets. Just find out reason may be something else. Yes, if all water droplets accumulated in such way that it forms water pool or complete area got soaked and may lead to poor insulation and thereby may cause short circuit. Shorting of busbar generally caused due to fall of foreign material over the open parts of bars or due to some other reasons supports got in contact. Rest all depends upon facts at scene.

To have a <...fire...> one needs three things: a fuel source, oxygen, and a source of ignition. Water, depending on its resistivity (which is a function of what is dissolved in it), might provide a conductive path and therefore a source of heat. It is not inconceivable that an arc has formed, promoted by <...water droplets...>.

The source of the fuel is of interest. It might, for example, be an animal that has become lodged between two <...busbar[s]...>, such as a nesting bird or something else. After all, if the containment is so poor that <...water...> can get in there, then something else can too. What animal doesn't want a warm and secure place to live, for example (rhetorical question - NNTR)?

The lesson is to look after electrical systems, and keep out stuff that really ought not to be there. Therefore the maintenance regime for the installation under discussion is clearly lacking something and needs to be improved, both for this facility and all others under the business' control, to prevent loss to life, limb, process and revenue.

I have seen several boards (MCCs and switchboards) that have been flooded, up to a few feet deep, including busbars. None exploded. But as pointed out above, water comes in many different levels of purity. Flood water is typically contaminated, salty and therefore quite conductive, but does not normally have a low enough resistance to go bang.

The ones I have seen have been at typical 400V 3 phase (UK), the effects vary but the leakage current is usually enough to cause localised heating - think "huge kettle". In some cases this will not be enough to trip the supply, just enough to boil all the components for hours on end.

The board can be dried out temporarily but medium/long term it is likely scrap, just depends how long you wait before you replace it. So many small components inside will be wrecked, as well as the structure.

Water droplets will likely not cause so much damage, just depends how much and for how long.

Open power lines on poles/towers survive heavy rain. Salt spray near sea or dust in desert with no rain to wash clean need longer multiple insulator strings than standard.

Humid tropical conditions cause accumulation of moisture in unsealed enclosures. In second World War it was learnt that jungle radio equipment had to be sealed to best degree AND have a desiccant to absorb the moisture that still got in, moisture also feeds moulds on surfaces that cause leakage currents.

I have known flashovers in 11 kV generator line cubicle [Egypt, low rainfall], attributed to not connecting anti-condensation heaters. Also Jersey, Channel Islands, standby set bus-duct, not enough anti-con heaters - heating can cause moisture to accumulate in colder places away from heater. Some ventilation needed to remove moisture - air in high humidity periods fills enclosure, temperature drop causes condensation.

I once saw a film of a test to prove cause of failure of a "flameproof" [Ex(d) gas explosion prevention] junction box for electrics. It contained nothing but wires and terminals, which were overloaded to simulate known preconditions to field failure in a mine. Overheating caused insulation failure ["tracking" conduction over surface ] - that caused breakdown of insulation into flammables which burnt, increasing pressure. Black smoke poured out of edges of junction box lid, eventually flames, then lid blown off.

So yes, you can have a fire in a busbar with insulators. Many insulators are made of/covered by plastics, which are "fire resistant" not non-combustible - hurrah for good old porcelain!! An arc on a busbar will travel to the end away from the source where it applies intense heat to the end insulator. If the protection is quick, the damage is repairable.

Load tanks are used as liquid loads for electrical testing, usually with salty water - however at 11 kV good tap water proved necessary for conduction without flashover.

I suggest you need to investigate the overload and short-circuit protection of your busbar compared to its ratings and whether it has functional anti-condensation heaters.

Explosion proof enclosures will have a gap at the bottom of the threads to channel the hot gases a way out,and they cool below the ignition point by the time they exit the enclosure.

The hot vapors are cooled by the long path through the threads.The enclosure should be rated for explosive vapors if used in a mine.
Of course,things can happen too fast for the gases to escape and if sufficient pressure exists,it will explode.For instance,if explosive vapors enter the enclosure during installation or maintenance.

It is good practice to purge the enclosure with nitrogen as the lid is closed.Even so,nothing is perfect and there is always Murphy hanging around.

Even carbonated drinks have a safety valve.Look at the thread on a cola bottle.

See the gaps?That is to prevent the bottle from exploding in excessive heat or pressure.The bottle cap sealer only tightens to the first stop of the threads.If you want your cola to keep it's fizz longer,tighten it down to the absolute stop.You will feel the initial stop,but keep tightening and it will keep going until it hits a dead stop,

This bypasses the over pressure threads which always have a little leakage,and this prevents that leakage.

Try it,you will see.

I have seen 13 kv bus bars arc and melt because moisture built up on the bus bars.The transformers had heaters in the bottom to evaporate any moisture that entered,but when a lot of water surrounded the enclosure,there was some leakage.The heaters vaporized the water,tuning it to steam,causing a moisture build up on the bus bars.

The arc lasted long enough to heat up the whole cabinet which made more steam,which sustained the arc enough to melt the bus bars.If the fog becomes too thick it can cause an arc,like lightning in a thunderstorm.A tiny arc can grow very rapidly due to ionization of the air around it,then it turn destructive.

The problem was caused by the regulation requiring a catchment (curbing) basin around all transformers that had any PCB's in the oil coolers.There was a gate that was removed during rainy weather,but it was overlooked,(there were over 40 transformer enclosures at the factory) and the containment curb remained closed during the storm.This resulted in the water level getting too high and finding a way into the transformer cabinet.