RCD testing: on modern electrical systems RCD’s and RCBO’s are regularly fitted, these devices react to electricity missing from the circuit or installation such as when a person is receiving an electric shock as the electricity passes through his body to the ground (earth). Electrical Installation Condition Report. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
Earth Science Stack Exchange is a question and answer site for those interested in the geology, meteorology, oceanography, and environmental sciences. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. The enlightening image below is of a lightning strike slowed down at 10, frames per second. It can be seen that the most intense flash produced from the lightening occurs in the direction from the ground up.
Why does this final "ground-up" strike occur and why is it so electricaal brighter and faster than the initial part of strike heading towards the ground? The answer is both. Cloud-to-ground lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity that we cannot see towards the ground in a series of spurts. Objects on the ground generally have a positive charge.
Since opposites elrctrical an upward streamer is sent out from the object about to how to make electrical earth ground struck.
When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast - in about one-millionth of a second - so the human eye doesn't see the actual formation of the stroke. Source: National Severe Storms Laboratory. The reason is that when cloud-to-ground strike how to make electrical earth ground the ground, the presence of opposite charges on the ground enhances the slectrical of the electric field and the "downward leader" strike creates bridge for the "return stroke"; this per the wiki page for Lightning.
Lightning discharges may occur between areas of cloud without contacting the ground. When it occurs between two separate clouds it is known as inter-cloud lightning, and when it occurs between areas of differing electric potential within a single cloud it is known as intra-cloud lightning. Intra-cloud lightning is the most frequently occurring type. Appears that ground-to-cloud is possible, though normally only a result of a man-made object creating "unnatural" electric potential, and is the least common type of lightning.
Lightning happens when the potential difference between the clouds and the grounds becomes too large. Once the voltage reaches a critical strength, the atmosphere can no longer act as an electrical insulator. First, a stepped leader is created at the base of the cloud which is a channel through which electrons in the cloud can travel to the ground. But while moving towards the ground, it searches for the most efficient minimum electrical resistance route possible. It does so by grouns meters at a time then stopping for about 50 microseconds, then traveling another meters.
In this process it also branches out looking for the best route. As the stepped leader gets close to the ground, a positively charged traveling spark is initiated on some tall object trees, towers etc on the ground. The traveling spark moves upward and eventually connects with the stepped leader.
Once the stepped leader and the traveling spark have connected, then electrons from the cloud can flow to the ground, and positive charges can flow from the ground to the cloud. This is known as return stroke. But this flow unlike the flow from up has a well defined shortest route now. This massive flow of electrical current occurring during the return stroke combined with the rate at which it occurs measured in microseconds rapidly superheats the completed leader channel, forming a highly electrically-conductive plasma channel.
The core temperature of the plasma during the return stroke may exceed 50, K, which makes it shine so bright. In your image above as well, you can see a lot of time is lost in looking for the route, whereas the return stroke just runs through the well defined channel and hence is much faster. In the video, the downward strike created an ionized path. The brightness was less as the current was less because it was travelling through un-ionized air.
The upward strike took the ionized path. The upward strike's current brightness was much greater as the electrons flowed along the ionized path gow it had the least resistance. The current equals the voltage how to sterilize body jewelry without an autoclave by the resistance.
The less the resistance, the higher the current. The apparent speed difference is because the upward strike took a more direct path. The camera shows a two dimensional image and does not show the motion of the lightning away from or towards the camera. In a video when you see an object coming directly towards or away from the camera, you see the object get larger or smaller.
The how to build guitar pedal board differences in the video are not large enough to show the direction towards or away from the camera.
I'm pretty sure that lightning can go either how to make electrical earth ground. What that means is, an electric field is created between the clouds and the ground mske a build up of electrons on one of the surfaces. I believe that the electron build up can occur on either side. Once the field strength gets high enough, electrons begin to "leak" from hoa side of the air-gap air does not normally conduct electricity unless it is highly charged and that is what lightning is.
You see the same affect in a capacitor that is overcharged, only instead of a thin sheet of paper, gow are inside the insulator between plates. That is why you get a lot of noise thunder of coursesee a lot of light, and wireless communications and some electronics are affected. I won't repeat something provided in other answers. The only thing i would like to add is that we don't see a Ground To Cloud Lightning. Theoretically speaking Ground To Cloud could be possible since lightning is a discharge between 2 points that have extreme voltage difference.
Electtical it is not a mystery "why this happens" as said in this videobut 'how this happens". Is it a case of Geology of the location like Lake Maracaibo or the lake of the groubd lightnings? Yes and it is eaeth to examine more thoroughly since some effects do happen more frequently in certain geographical locations all it is needed to be understood is WHY and it could be not just one factor. Notice the bright flash on the top left corner at the beginning that spreads into several leaders reaching for the ground.
No ground path been established until two of those leaders reach the ground. From those two paths one of them has less resistance leading to a momentary current path among the cloud and the ground. The image is taken from an High Speed or Ultra High Speed Camera, capable how to create lil wayne on nba 2k12 10k-1m frames per second, what we see is very slow motion of a cloud discharge.
Furthermore one thing you should have in mind is that lightning is how to play swf files on windows xp just a static electricity discharge. This discharge may produce a wide range of electromagnetic radiation, from very hot plasma created by the rapid movement of electrons to brilliant flashes of visible light in the form of black-body radiation.
Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms and other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions.
Above is written that the discharge itself may produce wide range of electromagnetic radiation. The majority of that radiation should be produced once the Cloud To Ground path has been established. In case we do have a combination of positive and negative lightning on that path then perhaps a differently filtered how to make electrical earth ground of this lightning microwave, infrared, ultraviolet, or even X-ray range would have been more enlightening.
I actually don't think that hhow the radiation comes from the discharge itself as written above. It should be a combination of static electricity and radiation even before the discharge, only to be amplified at the moment of discharge. This video shows something that could be identified as ball lightning. One of the theories on how ball maje occur indicate that Si how to make electrical earth ground on soil could be a factor.
In order to prove my point on this optical illusion in the above image i add a link of another optical illusionof course on that video the train has one and only course but we see it to have both, in cases like that the human brain finds other ways to determine the direction. Based on observing this and other slow motion vround of cloud-earth lightning How to make electrical earth ground observe the following:.
Some low-intensity "pilot lightning" starts in the cloud, usually only at one point fo at most a few points, and propagates in many directions away from that point, branching out much like a river delta or electricwl tree branch.
The general direction of propagation is towards the ground, but not very strongly. The most consistent trait of the movement is away from the originbut not even that is absolute there are a few loops and upward branches. Once one of the branches touches or gets close to the ground an intense arc forms between that point on the ground and the origin of the grojnd lighning". There is no clear indication of a direction, partly because of the unavoidable camera overload.
The pilot lightning starts where the gradient of the inhomogeneous electric field is steepest, somewhere close to the concentrated collection of charge in the cloud. It does not start on the ground because the ground conducts comparatively well so that the electrial dissipate, lowering the electric field strength. The pilot lightning's propagation is driven by two factors: The electric field and a feedback mechanism.
The feedback happens because the plasma corridor created by the emerging lightning bolt conducts electricity very well and thus facilitates propagation once it has started: Electrons and ions are accelerated and extend the corridor at its front. Apparently there is a chaotic element to this, possibly because turning air into plasma is an explosive process. This multi-directional explosive expansion is also responsible for the branching.
That the lightning roughly follows the field gradient explains the general direction. The feedback sustains the lightning once it has started. The explosive expansion of the heated air explains its chaotic parts. When one of the pilot lightning branches gets close enough to the ground that an arc to the ground is completed there is a completely conductive connection between the separated charges which will lead to how to know when labor is close runaway discharge known as a lightning bolt.
It's a runaway process because higher currents increase the arc's conductivity by turning more air into plasma, so the current grows until the charges are exhausted. I do not think that the eventual main lightning bolt has a different "direction" than the pilot lightning, and I cannot find observational evidence.
Even atframes per second the intensifying appears instantaneousand the main bolt is so bright that cameras are overloaded. It may appear to the human perception as a "back strike" because it starts once the pilot lightning touches ground, much like a bounce-back event.
But I think it's just that suddenly a lot of charges flow where only few charges were flowing a millisecond earlier, in the same direction. Sign up to join this community. The best electrifal are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How to make electrical earth ground does lightning strike from the ground-up? Ask Question.
What you need to know
Ground / Earth / 0V / Common. Ground and earth mainly come from AC electricity. They are used interchangably today. In AC power distribution you literally connect one side of the circuit to the ground/earth/terra. 0V came into use because its simple. Dec 08, · The Fluke GEO Earth Ground Tester Kit is a unique earth ground tester that can perform all four types of earth ground measurement including stakeless and staked earth ground measurement. Fluke GEO Earth Ground Tester Kit is rated out of 5 by 1. Jan 29, · Ground or earth in a mains electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment. Earthing is more commonly used in Britain, European and most of the commonwealth countries standards (IEC, IS), while Grounding is the word used in North American standards.
In an electric power system , a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which current bypasses the normal load. An open-circuit fault occurs if a circuit is interrupted by some failure.
In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations.
In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure. In a polyphase system , a fault may affect all phases equally which is a "symmetric fault". If only some phases are affected, the resulting "asymmetric fault" becomes more complicated to analyse.
The analysis of these types of faults is often simplified by using methods such as symmetrical components. The design of systems to detect and interrupt power system faults is the main objective of power-system protection.
A transient fault is a fault that is no longer present if power is disconnected for a short time and then restored; or an insulation fault which only temporarily affects a device's dielectric properties which are restored after a short time. Many faults in overhead power lines are transient in nature. When a fault occurs, equipment used for power system protection operate to isolate the area of the fault. A transient fault will then clear and the power-line can be returned to service.
Typical examples of transient faults include:. Transmission and distribution systems use an automatic re-close function which is commonly used on overhead lines to attempt to restore power in the event of a transient fault. This functionality is not as common on underground systems as faults there are typically of a persistent nature.
Transient faults may still cause damage both at the site of the original fault or elsewhere in the network as fault current is generated. A persistent fault is present regardless of power being applied. Faults in underground power cables are most often persistent due to mechanical damage to the cable, but are sometimes transient in nature due to lightning. An asymmetric or unbalanced fault does not affect each of the phases equally. Common types of asymmetric fault, and their causes:. A symmetric or balanced fault affects each of the phases equally.
However, they can cause very severe damage to equipment even though the system remains balanced. One extreme is where the fault has zero impedance, giving the maximum prospective short-circuit current. Notionally, all the conductors are considered connected to ground as if by a metallic conductor; this is called a "bolted fault".
It would be unusual in a well-designed power system to have a metallic short circuit to ground but such faults can occur by mischance. In one type of transmission line protection, a "bolted fault" is deliberately introduced to speed up operation of protective devices. A ground fault earth fault is any failure that allows unintended connection of power circuit conductors with the earth. Some special power distribution systems may be designed to tolerate a single ground fault and continue in operation.
Wiring codes may require an insulation monitoring device to give an alarm in such a case, so the cause of the ground fault can be identified and remedied. If a second ground fault develops in such a system, it can result in overcurrent or failure of components. Even in systems that are normally connected to ground to limit overvoltages , some applications require a Ground Fault Interrupter or similar device to detect faults to ground.
Realistically, the resistance in a fault can be from close to zero to fairly high relative to the load resistance. A large amount of power may be consumed in the fault, compared with the zero-impedance case where the power is zero.
Also, arcs are highly non-linear, so a simple resistance is not a good model. All possible cases need to be considered for a good analysis. Where the system voltage is high enough, an electric arc may form between power system conductors and ground. Such an arc can have a relatively high impedance compared to the normal operating levels of the system and can be difficult to detect by simple overcurrent protection. For example, an arc of several hundred amperes on a circuit normally carrying a thousand amperes may not trip overcurrent circuit breakers but can do enormous damage to bus bars or cables before it becomes a complete short circuit.
Utility, industrial, and commercial power systems have additional protection devices to detect relatively small but undesired currents escaping to ground. In residential wiring, electrical regulations may now require arc-fault circuit interrupters on building wiring circuits, to detect small arcs before they cause damage or a fire. Symmetric faults can be analyzed via the same methods as any other phenomena in power systems, and in fact many software tools exist to accomplish this type of analysis automatically see power flow study.
However, there is another method which is as accurate and is usually more instructive. First, some simplifying assumptions are made. It is assumed that all electrical generators in the system are in phase, and operating at the nominal voltage of the system.
Electric motors can also be considered to be generators, because when a fault occurs, they usually supply rather than draw power. The voltages and currents are then calculated for this base case.
Next, the location of the fault is considered to be supplied with a negative voltage source, equal to the voltage at that location in the base case, while all other sources are set to zero. This method makes use of the principle of superposition.
To obtain a more accurate result, these calculations should be performed separately for three separate time ranges:. An asymmetric fault breaks the underlying assumptions used in three-phase power, namely that the load is balanced on all three phases. Consequently, it is impossible to directly use tools such as the one-line diagram , where only one phase is considered. However, due to the linearity of power systems, it is usual to consider the resulting voltages and currents as a superposition of symmetrical components , to which three-phase analysis can be applied.
In the method of symmetric components, the power system is seen as a superposition of three components:. To determine the currents resulting from an asymmetric fault, one must first know the per-unit zero-, positive-, and negative-sequence impedances of the transmission lines, generators, and transformers involved.
Three separate circuits are then constructed using these impedances. The individual circuits are then connected together in a particular arrangement that depends upon the type of fault being studied this can be found in most power systems textbooks. Once the sequence circuits are properly connected, the network can then be analyzed using classical circuit analysis techniques. The solution results in voltages and currents that exist as symmetrical components; these must be transformed back into phase values by using the A matrix.
Analysis of the prospective short-circuit current is required for selection of protective devices such as fuses and circuit breakers. If a circuit is to be properly protected, the fault current must be high enough to operate the protective device within as short a time as possible; also the protective device must be able to withstand the fault current and extinguish any resulting arcs without itself being destroyed or sustaining the arc for any significant length of time.
The magnitude of fault currents differ widely depending on the type of earthing system used, the installation's supply type and earthing system, and its proximity to the supply. Large low-voltage networks with multiple sources may have fault levels of , amperes.
A high-resistance-grounded system may restrict line to ground fault current to only 5 amperes. Prior to selecting protective devices, prospective fault current must be measured reliably at the origin of the installation and at the furthest point of each circuit, and this information applied properly to the application of the circuits. Overhead power lines are easiest to diagnose since the problem is usually obvious, e.
Locating faults in a cable system can be done either with the circuit de-energized, or in some cases, with the circuit under power. Fault location techniques can be broadly divided into terminal methods, which use voltages and currents measured at the ends of the cable, and tracer methods, which require inspection along the length of the cable. Terminal methods can be used to locate the general area of the fault, to expedite tracing on a long or buried cable. In very simple wiring systems, the fault location is often found through inspection of the wires.
In complex wiring systems for example, aircraft wiring where the wires may be hidden, wiring faults are located with a Time-domain reflectometer. In historic submarine telegraph cables , sensitive galvanometers were used to measure fault currents; by testing at both ends of a faulted cable, the fault location could be isolated to within a few miles, which allowed the cable to be grappled up and repaired.
The Murray loop and the Varley loop were two types of connections for locating faults in cables. Sometimes an insulation fault in a power cable will not show up at lower voltages.
A "thumper" test set applies a high-energy, high-voltage pulse to the cable. Fault location is done by listening for the sound of the discharge at the fault.
While this test contributes to damage at the cable site, it is practical because the faulted location would have to be re-insulated when found in any case. In a high resistance grounded distribution system, a feeder may develop a fault to ground but the system continues in operation. The faulted, but energized, feeder can be found with a ring-type current transformer collecting all the phase wires of the circuit; only the circuit containing a fault to ground will show a net unbalanced current.
To make the ground fault current easier to detect, the grounding resistor of the system may be switched between two values so that the fault current pulses. The prospective fault current of larger batteries, such as deep-cycle batteries used in stand-alone power systems , is often given by the manufacturer. From Wikipedia, the free encyclopedia. Abnormal electric current. February 5, Power System Analysis. Tata McGraw-Hill. ISBN December, Glover, J. Power System Analysis and Design.
Burton, G. Power Analysis. Categories : Power engineering Engineering failures. Hidden categories: Articles with short description Short description matches Wikidata All articles with unsourced statements Articles with unsourced statements from June Namespaces Article Talk.
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