Line to Ground Fault

8/6/2019 Line to Ground Fault

1/17

In an electric power system, a fault is any abnormal flow ofelectric current. For

example a short circuit is a fault in which current flow bypasses the normal load.

An open circuit fault occurs if a circuit is interrupted by some failure. Inthree

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 fault can be calculated for

power systems. In power systems, protective devices detect fault conditions and

operate circuit breakersand 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

"symmetrical fault". If only some phases are affected, the resulting "asymmetrical

fault" becomes more complicated to analyse due to the simplifying assumption of

equal current magnitude in all phases being no longer applicable. The analysis of

this type of fault is often simplified by using methods such as symmetrical

components.

Transient fault

A transient fault is a fault that is no longer present if power is disconnected for a

short time.

Many faults in overhead powerlines are transient in nature. At the occurrence of

a fault power system protectionoperates to isolate area of the fault. A transient

fault will then clear and the powerline can be returned to service. Typical

examples of transient faults include:

momentary tree contact

bird or other animal contact

lightning strike

conductor clash

In electricity transmission and distribution systems an automatic reclose functionis 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.


2/17

[edit]Persistent fault

A persistent fault does not disappear when power is disconnected. Faults in

underground power cables are often persistent. Underground power lines are not

affected by trees orlightning, so faults, when they occur, are probably due todamage. In such cases, if the line is reconnected, it is likely to be only damaged

further.

[edit]Symmetric fault

A symmetric, symmetrical orbalanced fault affects each of the three-phases

equally. In transmission line faults, roughly 5% are symmetric [citation needed]. This is

in contrast to an asymmetric fault, where the three phases are not affected

equally. In practice, most faults in power systems are unbalanced. With this inmind, symmetric faults can be viewed as somewhat of an abstraction; however,

as asymmetric faults are difficult to analyze, analysis of asymmetric faults is built

up from a thorough understanding of symmetric faults.

[edit]Asymetric fault

An asymmetric orunbalanced fault does not affect each of the three phases

equally.

Common types of asymmetric faults, and their causes:

line-to-line - a short circuit between lines, caused by ionization of air, or when

lines come into physical contact, for example due to a broken insulator.

line-to-ground- a short circuit between one line and ground, very often

caused by physical contact, for example due to lightning or

otherstorm damage

double line-to-ground- two lines come into contact with the ground (and each

other), also commonly due to storm damage

[edit]Analysis

Symmetric faults can be analyzed via the same methods as any other

phenomena in power systems, and in fact manysoftware 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.


3/17

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 thisbase 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 ofsuperposition.

To obtain a more accurate result, these calculations should be performed

separately for three separate time ranges:

subtransientis first, and is associated with the largest currents

transientcomes between subtransient and steady-state

steady-state occurs after all the transients have had time to settle

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 directlyuse 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 currentsas a superposition ofsymmetrical

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:

a positive-sequence component, in which the phases are in the same order as

the original system, i.e., a-b-c

a negative-sequence component, in which the phases are in the opposite

order as the original system, i.e., a-c-b

a zero-sequence component, which is not truly a three phase system, but

instead all three phases are in phase with each other.To determine the currents resulting from an asymmetrical 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


4/17

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. For example, for a domestic UK 230 V, 60 A TN-S or USA 120

V/240 V supply, fault currents may be a few thousand amperes. Large low-

voltage networks with multiple sources may have fault levels of 300,000

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.

[edit]Detecting and locating faults

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.[1]

In very simple wiring systems, the fault location is often found through visual

inspection of the wires. In complex wiring systems (e.g. aircraft wiring) where the

electrical wires may be hidden behind cabinets and extended for miles, wiring

faults are located with a Time-domain reflectometer.[2] The time domain


5/17

reflectometer sends a pulse down the wire and then analyzes the returning

reflected pulse to identify faults within the electrical wire.

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 Murrayloop and the Varleyloop 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.[3]

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.

A time-domain reflectometer(TDR) is an electronic instrument used to

characterize and locate faults in metallic cables (for example, twisted wire

pairs, coaxial cables).[1] It can also be used to locate discontinuities in a

connector, printed circuit board, or any other electrical path. The equivalent

device foroptical fiberis an optical time-domain reflectometer.

Description

A TDR transmits a short rise timepulse along the conductor. If the conductor is

of a uniform impedance and is properlyterminated, the entire transmitted pulse

will be absorbed in the far-end termination and no signal will be reflected toward

the TDR. Any impedance discontinuities will cause some of the incident signal to

be sent back towards the source. This is similar in principle to radar.


6/17

Increases in the impedance create a reflection that reinforces the original pulse

whilst decreases in the impedance create a reflection that opposes the original

pulse.

The resulting reflected pulse that is measured at the output/input to the TDR is

displayed or plotted as a function of time and, because the speed of signal

propagation is almost constant for a given transmission medium, can be read as

a function ofcable length.

Because of this sensitivity to impedance variations, a TDR may be used to verify

cable impedance characteristics,splice and connectorlocations and associated

losses, and estimate cable lengths.

[edit]Example Traces

These traces were produced by the Time Domain Reflectometer made from

common lab equipment connected to approximately 100 feet of 50 ohm coaxial

cable. The propagation velocity of this cable is approximately 66% of the speed

of light in a vacuum.

Simple TDR made from lab equipment


7/17

Simple TDR made from lab equipment

TDR trace of a transmission line

with an open termination.


with a short circuit termination.


with a 1nF capacitor termination.


8/17

TDR trace of a transmission line with an almost

ideal termination.

TDR trace of a transmission line terminated on an

oscilloscope high impedance input. The blue trace is

the pulse as seen at the far end. It is offset so that

the baseline of each channel is visible.

[edit]ExplanationConsider the case where the far end of the cable is shorted (that is, it is

terminated into zero ohms impedance). When the rising edge of the pulse is

launched down the cable, the voltage at the launching point "steps up" to a given

value instantly and the pulse begins propagating down the cable towards theshort. When the pulse hits the short, no energy is absorbed at the far end.

Instead, an opposing pulse reflects back from the short towards the launching

end. It is only when this opposing reflection finally reaches the launch point that

the voltage at this launching point abruptly drops back to zero, signaling the fact

that there is a short at the end of the cable. That is, the TDR had no indication

that there is a short at the end of the cable until its emitted pulse can travel down

the cable at roughly the speed of light and the echo can return back up the cable

at the same speed. It is only after this round-trip delay that the short can be

perceived by the TDR. Assuming that one knows the signal propagation speed in

the particular cable-under-test, then in this way, the distance to the short can be

measured.

A similar effect occurs if the far end of the cable is an open circuit (terminated

into an infinite impedance). In this case, though, the reflection from the far end is


9/17

polarized identically with the original pulse and adds to it rather than cancelling it

out. So after a round-trip delay, the voltage at the TDR abruptly jumps to twice

the originally-applied voltage.

Note that a theoretical perfect termination at the far end of the cable would

entirely absorb the applied pulse without causing any reflection. In this case, it

would be impossible to determine the actual length of the cable. Luckily, perfect

terminations are very rare and some small reflection is nearly always caused.

The magnitude of the reflection is referred to as the reflection coefficient or .

The coefficient ranges from 1 (open circuit) to -1 (short circuit). The value of zero

means that there is no reflection. The reflection coefficient is calculated as

follows:

Where Zo is defined as the characteristic impedance of the transmission medium

and Zt is the impedance of the termination at the far end of the transmission line.

Any discontinuity can be viewed as a termination impedance and substituted as

Zt. This includes abrupt changes in the characteristic impedance. As an example,

a trace width on a printed circuit board doubled at its midsection would constitute

a discontinuity. Some of the energy will be reflected back to the driving source;

the remaining energy will be transmitted. This is also known as a scatteringjunction.

[edit]Usage

Time domain reflectometers are commonly used for in-place testing of very long

cable runs, where it is impractical to dig up or remove what may be a kilometers-

long cable. They are indispensable forpreventive

maintenance oftelecommunication lines, as they can reveal growing resistance

levels on joints and connectors as they corrode, and

increasing insulation leakage as it degrades and absorbs moisture long before

either leads to catastrophic failures. Using a TDR, it is possible to pinpoint a fault

to within centimetres.

TDRs are also very useful tools fortechnical surveillance counter-measures,

where they help determine the existence and location ofwire taps. The slight


10/17

change in line impedance caused by the introduction of a tap or splice will show

up on the screen of a TDR when connected to a phone line.

TDR equipment is also an essential tool in the failure analysis of modern high-

frequency printed circuit boards whose signal traces are carefully crafted to

emulate transmission lines. By observing reflections, any unsoldered pins of

a ball grid array device can be detected. Additionally, short circuited pins can

also be detected in a similar fashion.

The TDR principle is used in industrial settings, in situations as diverse as the

testing ofintegrated circuit packages to measuring liquid levels. In the former, the

time domain reflectometer is used to isolate failing sites in the same. The latter is

primarily limited to the process industry.

[edit]TDR in level measurementIn a TDR-based level measurement device, a low-energy electromagnetic

impulse generated by the sensors circuitry is propagated along a thin wave

guide (also referred to as a probe) usually a metal rod or a steel cable. When

this impulse hits the surface of the medium to be measured, part of the impulse

energy is reflected back up the probe to the circuitry which then calculates the

fluid level from the time difference between the impulse sent and the impulse

reflected (in nanoseconds). The sensors can output the analyzed level as a

continuous analog signal or switch output signals. In TDR technology, the

impulse velocity is primarily affected by the permittivity of the medium through

which the pulse propagates, which can vary greatly by the moisture content and

temperature of the medium. In most cases, this can be corrected for without

undue difficulty. However, in complex environments, such as in boiling and/or

high temperature environments, this can be a significant signal processing

dilemma. In particular, determining the froth(foam) height and true collapsed

liquid level in a frothy / boiling medium can be very difficult.

[edit]TDR used in Anchor Cables in Dams

The Dam Safety Interest Group of CEA Technologies, Inc. (CEATI), a consortium

of electrical power organizations, has applied Spread-spectrum time-domain

reflectometry to identify potential faults in concrete dam anchor cables. The key

benefit of Time Domain reflectometry over other testing methods is the non-

destructive method of these tests.


11/17

[edit]TDR used in the earth and agricultural sciences

TDR is used to determine moisture content in soil and porous media, where over

the last two decades substantial advances have been made; including in soils,

grains and food stuffs, and in sediments. The key to TDRs success is its ability

to accurately determine the permittivity (dielectric constant) of a material from

wave propagation, and the fact that there is a strong relationship between the

permittivity of a material and its water content, as demonstrated in the pioneering

works of Hoekstra and Delaney (1974) and Topp et al. (1980). Recent reviews

and reference work on the subject include, Topp and Reynolds (1998), Noborio

(2001), Pettinellia et al. (2002), Topp and Ferre (2002) and Robinson et al.

(2003). The TDR method is a transmission line technique, and determines an

apparent TDR permittivity (Ka) from the travel time of an electromagnetic wave

that propagates along a transmission line, usually two or more parallel metal rodsembedded in a soil or sediment. TDR probes are usually between 10 and 30 cm

in length and connected to the TDR via a coaxial cable.

[edit]TDR in geotechnical usage

Time domain reflectometry has also been utilized to monitor slope movement in a

variety of geotechnical settings including highway cuts, rail beds, and open pit

mines (Dowding & O'Connor, 1984, 2000a, 2000b; Kane & Beck, 1999). In

stability monitoring applications using TDR, a coaxial cable is installed in a

vertical borehole passing through the region of concern. The electrical

impedance at any point along a coaxial cable changes with deformation of the

insulator between the conductors. A brittle grout surrounds the cable to translate

earth movement into an abrupt cable deformation that shows up as a detectable

peak in the reflectance trace. Until recently, the technique was relatively

insensitive to small slope movements and could not be automated because it

relied on human detection of changes in the reflectance trace over time.

Farrington and Sargand (2004) developed a simple signal processing technique

using numerical derivatives to extract reliable indications of slope movement fromthe TDR data much earlier than by conventional interpretation.

[edit]TDR in semiconductor device analysis

Time domain reflectometry is used in semiconductorfailure analysis as a non-

destructive method for the location of defects in semiconductor device packages.


12/17

The TDR provides an electrical signature of individual conductive traces in the

device package, and is useful for determining the location of opens and shorts.

[edit]TDR in aviation wiring maintenance

Time domain reflectometry, specifically spread spectrum time domainreflectometry is used for aviation wiring for both preventative maintenance and

intermittent fault location.[2] The spread spectrum time domain reflectometry has

the advantage of precisely locating the fault location within thousands of miles of

aviation wiring. Additionally, this technology is being considering for live aviation

monitoring as the spread spectrum reflectometry works on a live wire.

Utah State conducted research[3] on use of time domain reflectometry for

identifying chafing of electrical wires in aircraft. This chafing is known to cause

electrical failures on aircraft so the ability to identify potential problems prior to afailure that has life-ending implications.

In communications and electronic engineering, a transmission line is a

specialized cable designed to carry alternating current ofradio frequency, that is,

currents with a frequency high enough that its wave nature must be taken into

account. Transmission lines are used for purposes such as connecting radio

transmitters and receivers with theirantennas, distributing cable

television signals, and computer network connections.

Ordinary electrical cables suffice to carry low frequency AC, such as mains

power, which reverses direction 100 to 120 times per second (cycling 50 to 60

times per second). However, they cannot be used to carry currents in the radio

frequency range or higher, which reverse direction millions to billions of times per

second, because the energy tends to radiate off the cable as radio waves,

causing power losses. Radio frequency currents also tend to reflect from

discontinuities in the cable such as connectors, and travel back down the cable

toward the source. These reflections act as bottlenecks, preventing the powerfrom reaching the destination. Transmission lines use specialized construction

such as precise conductor dimensions and spacing, and impedance matching, to

carry electromagnetic signals with minimal reflections and power losses. Types

of transmission line include ladder line, coaxial cable, dielectric

slabs,stripline, optical fiber, and waveguides. The higher the frequency, the


13/17

shorter are the waves in a transmission medium. Transmission lines must be

used when the frequency is high enough that the wavelength of the waves

begins to approach the length of the cable used. To conduct energy at

frequencies above the radio range, such as millimeter waves, infrared, and light,

the waves become much smaller than the dimensions of the structures used toguide them, so transmission line techniques become inadequate and the

methods ofoptics are used.

The theory ofsound wave propagation is very similar mathematically to that of

electromagnetic waves, so techniques from transmission line theory are also

used to build structures to conduct acoustic waves; and these are also called

transmission lines.

Transient fault

A transient fault is a fault that is no longer present if power is disconnected for a

short time.

Many faults in overhead powerlines are transient in nature. At the occurrence of

a fault power system protectionoperates to isolate area of the fault. A transient

fault will then clear and the powerline can be returned to service. Typical

examples of transient faults include:

momentary tree contact

bird or other animal contact

lightning strike

conductor clash

In electricity transmission and distribution systems an automatic reclose function

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.

[edit]Persistent fault


14/17

A persistent fault does not disappear when power is disconnected. Faults in

underground power cables are often persistent. Underground power lines are not

affected by trees orlightning, so faults, when they occur, are probably due to

damage. In such cases, if the line is reconnected, it is likely to be only damaged

further.

[edit]Symmetric fault

A symmetric, symmetrical orbalanced fault affects each of the three-phases

equally. In transmission line faults, roughly 5% are symmetric [citation needed]. This is

in contrast to an asymmetric fault, where the three phases are not affected

equally. In practice, most faults in power systems are unbalanced. With this in

mind, symmetric faults can be viewed as somewhat of an abstraction; however,

as asymmetric faults are difficult to analyze, analysis of asymmetric faults is builtup from a thorough understanding of symmetric faults.

[edit]Asymetric fault

An asymmetric orunbalanced fault does not affect each of the three phases

equally.

Common types of asymmetric faults, and their causes:

line-to-line - a short circuit between lines, caused by ionization of air, or when

lines come into physical contact, for example due to a broken insulator.

line-to-ground- a short circuit between one line and ground, very often

caused by physical contact, for example due to lightning or

otherstorm damage

double line-to-ground- two lines come into contact with the ground (and each

other), also commonly due to storm damage

[edit]Analysis

Symmetric faults can be analyzed via the same methods as any other

phenomena in power systems, and in fact manysoftware 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


15/17

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 thisbase 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 ofsuperposition.

To obtain a more accurate result, these calculations should be performed

separately for three separate time ranges:

subtransientis first, and is associated with the largest currents

transientcomes between subtransient and steady-state

steady-state occurs after all the transients have had time to settle

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 directlyuse 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 currentsas a superposition ofsymmetrical

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:

a positive-sequence component, in which the phases are in the same order as

the original system, i.e., a-b-c

a negative-sequence component, in which the phases are in the opposite

order as the original system, i.e., a-c-b

a zero-sequence component, which is not truly a three phase system, but

instead all three phases are in phase with each other.

To determine the currents resulting from an asymmetrical fault, one must first

know the per-unit zero-, positive-, and negative-sequence impedances of thetransmission 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


16/17

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. For example, for a domestic UK 230 V, 60 A TN-S or USA 120

V/240 V supply, fault currents may be a few thousand amperes. Large low-

voltage networks with multiple sources may have fault levels of 300,000

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.

[edit]Detecting and locating faults

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.[1]

In very simple wiring systems, the fault location is often found through visual

inspection of the wires. In complex wiring systems (e.g. aircraft wiring) where theelectrical wires may be hidden behind cabinets and extended for miles, wiring

faults are located with a Time-domain reflectometer.[2] The time domain

reflectometer sends a pulse down the wire and then analyzes the returning

reflected pulse to identify faults within the electrical wire.


17/17

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 Murrayloop and the Varleyloop 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.[3]

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.

[edit]Batteries

The prospective fault current of larger batteries, such as deep-cyclebatteries used in stand-alone power systems, is often given by the manufacturer.

In Australia, when this information is not given, the prospective fault current in

amperes "should be considered to be 6 times the nominal battery capacity at

the C120 Ah rate," according to AS 4086 part 2 (Appendix H).

Documents

Line to Ground Fault