Note: Descriptions are shown in the official language in which they were submitted.
CA 02232683 1999-04-16
(a) TITLE OF THE INVENTION
SYSTEMS FOR DETERMINING FAULT LOCATION ON POWER
DISTRIBUTION LINES
(b) TECHNICAL FIELD TO WHICH THE INVENTION RELATES
The present invention relates to systems for improving the accuracy of
locating
faults on electric utility power distribution systems. More particularly, the
present
invention pertains to systems that utilize conducted and radiated signals to
locate faults
on electric utility power distribution systems. Even more particularly, the
present
invention relates to power line fault locating systems that utilize travelling
conducted
wave technology, precise timing means, and electromagnetic signal detection
means,
including lightning location technology, to locate faults on a power
distribution system.
(c) BACKGROUND ART
Electric power outages are very often attributed to faults that trigger
protective
devices in the power distribution system. The faults result because of the
creation of a
low impedance, current-conducting path between a power line and another power
line,
or from a power line to ground, or from a power line to the neutral line. The
current
being conducted is termed "fault current" and is typically preceded by an air
gap arc
which results from voltage levels which exceed the local insulation level.
Such arcs
typically result from lightning striking the line, tree branches blowing near
the line, birds
or small animals bridging the insulation gap, or cracked/dirty insulators. The
protective
devices of the distribution system are designed to sense the fault current and
to switch
relays to operate circuit breakers in an attempt to clear the fault. If the
fault can be
cleared, then finding the location of the fault is typically not of high
concern. However,
if the fault is intermittent, or re-occurring, then locating the fault is of
greater concern.
Locating the fault becomes of extreme concern when the fault can not be
cleared, i.e.,
a "bolted" or "lock-out" condition exists and the fault source must be found.
One method of locating the fault is line-men (persons) walking/driving/flying
along the line until the source of the fault is found. Obviously, if the fault
occurs along
distribution lines in urban areas, then the flying method is not practical. In
these
CA 02232683 1999-04-16
2
situations, the faults can be isolated by means of evaluating the incoming
telephone calls
of the customers. If the faults occur in less populated areas, then more
scientific
methods are required to locate the fault.
The state of the art in fault locating systems, (FLS), employs recording site
sensors that are responsive to conducted voltage transient/current transient
signals which
are produced by the fault. The fault locating methods are referred to either
as impedance
(reactance) or as travelling wave/time of arrival methods. The impedance
method
analyzes the impedance characteristics of a power line by comparing normal
loading
conditions against the abnormal line impedance resulting from a fault. The
travelling
wave method, utilizes the fact that a transient waveform is generated and
conducted away
from a fault at a first time. The fault waveforms propagate in opposite
directions, along
the line from the fault with respective propagation times. Knowledge of the
times of
arrival, at opposing measuring equipment, and characteristics about the line
being
monitored help in determining the distance that the wave has travelled from
the location
of the fault.
While these conducted transient methods have merits in a single stretch of
transmission lines, an element of ambiguity is introduced when there are
multiple
primary circuits or tap points, as in a distribution subsystem, since any one
of the circuit
paths could have been the source of the fault at the same distance determined.
The
travelling wave (voltage transient/current transient) method has been
published by P.F.
Gale of Hathaway Instruments Ltd., England, in a paper entitled: "OVERHEAD
LINE
FAULT LOCATION BASED ON TRAVELLING WAVES & GPS", and by H. Lee of
B.C. Hydro and Power Authority, Burnaby, B.C. in a paper entitled "DEVELOPMENT
OF AN ACCURATE TRAVELLING WAVE FAULT LOCATOR USING THE
GLOBAL POSITIONING SYSTEM SATELLITES" .
There are several known prior art patents relating to fault locating systems.
These include the following U.S. Patents Nos.: 3,670,240; 3,781,665;
3,878,460;
4,110,684; 4,165,482; 4,475,079; 4,672,321; 4,719,580; 4,731,689; 4,731,688;
5,256,976; 4,800,509; 5,146,170; 5,070,537; 5,256,976; 5,319,311; 5,321,632;
and
5,508,619.
CA 02232683 1999-04-16
,.
3
Of general interest are the teachings of U.S. Patent Nos. 5,070,537 and
5,508,619, which teach conducted voltage surge detection and the utilization
of GPS
(Global Positioning System) technology to determine the distance to the fault,
respectively.
U.S. Patent No. 5,256,976 teaches the use of a plurality of electromagnetic
wave
detectors which are disposed within metal containers and which detect
electromagnetic
waves which are generated by a fault within a container to aid in locating a
power line
fault. Each bus in a power line network has a detector which reports
electromagnetic
wave fault data only for that bus.
The electromagnetic wave detectors taught by U.S. Patent No. 5,256,976 do not
utilize synchronized time of arrival technology in its system.
None of the prior art patents teach an improved electric power line fault
locating
system that utilizes both conducted signal information and electromagnetic
radiated signal
information, in combination with GPS technology and geographical information
about the
line, to locate a fault on a power distribution line.
(d) DESCRIPTION OF THE INVENTION
Thus, there is a need to improve the accuracy of fault locating systems,
especially
when applied to distribution subcircuits where it is not practical to include
a sufficient
number of conducted waveform monitoring sites to provide unambiguous fault
locations.
However, it is known that power line faults generate low level electromagnetic
radiated
signals caused by arcing. To applicant's knowledge, power line fault locating
systems
have not fully employed this radiated electromagnetic signal detection (arc
detection) for
locating a fault.
It is therefore an object of one aspect of the present invention to provide an
improved electric power line fault locating system that utilizes both
conducted signal
information and electromagnetic radiated signal information, in combination
with
geographical information about the line to locate a fault on a power
distribution line.
An object of an additional aspect of the present invention is to provide an
improved electric power line fault locating system that utilizes conducted
signal
CA 02232683 1999-04-16
4
information, (e. g. , the travelling wave systems and methods currently known)
and
electromagnetic radiated signal information (precise time and location) which
is produced
by lightning locating systems, to locate faults on a power line which are
produced by a
lightning stroke on or near the line.
An object of a related aspect of the present invention is to provide an
improved
electric power line fault locating system that utilizes both conducted signal
information
and electromagnetic radiated signal information using electronic arc detection
sensors
(ADS) which are adapted to detect low level electromagnetic radiation
(VHF/UHF) which
is generated by acing which is associated with faults on a power distribution
line.
An object of another related aspect of the present invention is to provide an
improved electric power line fault locating system that utilizes only
electromagnetic
radiated signal information using a plurality of electronic arc detection
sensors (ADS)
which are adapted to detect low level electromagnetic radiation (VHF/UHF)
which is
generated by arcing which is associated with faults on a power distribution
line.
By a first broad aspect of this invention, a power distribution line fault
locating
system is provided, the system comprising at least one first data manipulation
unit for
manipulating conducted fault signal data resulting from a fault on a power
distribution
line, and producing and communicating a first set of fault location data, at
least one
second data manipulation unit for manipulating electromagnetic radiated signal
data
emanating from the fault on the power distribution line, and producing and
communicating a second set of fault location data, and a fault location centre
responsive
to the first set of fault location data and to the second set of fault
location data which is
produced by the at least one first data manipulation unit and by the at least
one second
data manipulation unit, for determining a location of the fault.
By one variant of this first broad aspect of this invention, the first set of
fault
location data comprises a time of arrival at the at least one first data
manipulation unit
of the conducted signal data which is generated by the fault on the power
distribution
line, the second set of fault location data comprises a precise time of
arrival of the
electromagnetic radiated signal data emanating from the fault on the power
distribution
line at the at least one second data manipulation unit, the time of arrival of
the conducted
CA 02232683 1999-04-16
signal data and the time of arrival of the electromagnetic radiated signal
data being
accurate to microsecond accuracy as made possible by the at least one first
data
manipulation unit and by the at least one second data manipulation unit being
provide
with, and utilizing, clocks that are synchronized by Global Positioning System
(GPS)
5 receivers, and the fault location centre comprises a power line fault
locating analyzer,
which is operative to determine a first path length between the at least one
first data
manipulation unit and the fault, and a second path length between the at least
one second
data manipulation unit and the fault, by utilizing (a) the time of arrival of
the conducted
signal data at the at least one first data manipulation unit, (b) the time of
arrival of the
electromagnetic radiated signal data as determined by the at least one second
data
manipulation unit, and (c) placement and path data of related individual power
lines
which are associated with the power distribution line as provided by a
geographical
information system.
By a second variant of this first broad aspect of this invention, and/or the
above
variant thereof, the conducted fault signal data comprises conducted
electrical signals
which are produced by the fault, and the at least one first data manipulation
unit
comprises a fault recording sensor which is responsive to conducted electrical
signal fault
data, for determining an impedance characteristic of the power distribution
line by
comparing normal loading conditions against an abnormal line impedance
resulting from
the fault.
By a third variant of this first broad aspect of this invention, and/or the
above
variants thereof, the conducted fault signal data comprises conducted current
transient
signal produced by the fault, and the at least one first data manipulation
unit comprises
a fault recording sensor which is responsive to the conducted current
transient signal for
determining its time of arrival data, the conducted current transient signal
being one of
a plurality of travelling wave signals that travel in opposite directions from
a location of
the fault.
By a fourth variant of this first broad aspect of this invention, and/or the
above
variants thereof, the electromagnetic radiated signal data comprises
electromagnetic
radiation data which is generated by a lightning discharge which produced a
lightning
CA 02232683 1999-04-16
6
caused fault on the power distribution line, and the at least one second data
manipulation
unit comprises at least one electronic lightning locating system that
manipulates the
electromagnetic radiation data which is generated by lightning and identifies
a time of
occurrence and a location of a stroke of lightning that caused the fault.
By a fifth variant of this first broad aspect of this invention, and/or the
above
variants thereof, the electromagnetic radiated signal data comprises low level
electromagnetic radiation (VHF/UHF) which is generated by arcing which is
associated
with a fault on the power distribution line, and the at least one second data
manipulation
unit comprises at least one electronic arc detection sensor having circuitry
that detects
the low level electromagnetic radiation (VHF/UHF) and that manipulates the
electromagnetic radiation for purposes of determining a time of arrival of the
radiation
at the electronic arc detection sensor.
By a second broad aspect of this invention, a power distribution line fault
locating
system is provided, the system comprising at least two electronic arc
detection sensors
having electronic circuitry which is responsive to low level electromagnetic
radiation
(VHF/UHF) emanating from arcing at a fault on a power distribution line, the
electronic
circuitry manipulating the electromagnetic radiation for purposes of
determining and
communicating a time of arrival of the radiation at each of the at least two
arc detection
sensors, and a power line fault locating analyzer, which is operative to
receive the
communicated time of arrival of the radiation at each of the at least two arc
detection
sensors, to manipulate stored longitudinal and latitudinal information on each
of the at
least two arc detection sensors, and further to manipulate placement and path
data of
related individual power lines which are associated with the power
distribution line as
provided by a geographical information system for purposes of determining an
exact
location of the fault.
By a third aspect of this invention, a power distribution line fault locating
system
is provided, the system comprising at least one first data manipulation unit
comprising
at least one fault recording sensor unit for manipulating a conducted
electrical signal
which is produced by a fault on a power distribution line, and producing and
communicating a first set of fault location data, the fault recording sensor
unit being
CA 02232683 1999-04-16
7
responsive to the conducted electrical signal for determining its time of
arrival data, the
conducted electrical signal being one of a plurality of conducted travelling
wave signals
that travel in opposite directions from a location of the fault, at least one
second data
manipulation unit for manipulating electromagnetic radiated signal data
emanating from
the fault on the power distribution line, and producing and communicating a
second set
of fault location data, and a fault location centre which is responsive to the
first set of
fault location data, and to the second set of fault location data which are
produced by the
at least one first data manipulation unit and by the at least one second data
manipulation
unit for determining a location of a fault.
By one variant of this third broad aspect of this invention, the
electromagnetic
radiated signal data comprises electromagnetic radiation data which is
generated by a
lightning-caused fault on the power distribution line, and the at least one
second data
manipulation unit comprises at least one electronic lightning locating system
that
manipulates the electromagnetic radiation data such that the second set of
fault location
data comprises a precise time of occurrence and location of lightning u,~hich
produced the
lightning-caused fault on the power distribution line.
By a second variant of this third broad aspect of this invention, and/or the
above
variant thereof, the conducted electrical signal comprises a conducted
electrical signal
which is generated by the lightning-caused fault on the power distribution
line, and the
first set of fault location data comprises a time of arrival at the at least
one first data
manipulation unit of the lightning-caused conducted electrical signal, the
time of arrival
of the lightning-caused conducted electrical signal and the time of occurrence
of lightning
which produced the lightning-caused fault being accurate to microsecond
accuracy as
made possible by the at least one first data manipulation unit and by the at
least one
second data manipulation unit being provided with, and utilizing, clocks that
are
synchronized by Global Positioning System (GPS) receiver, and the fault
location centre
comprises a power line fault locating analyzer, which is operative to
determine a first
path length between the at least one first data manipulation unit and the
lightning-caused
fault, and a second path length between the at least one second data
manipulation unit
and the lightning-caused fault, by utilizing the time of arrival of the
lightning-caused
CA 02232683 1999-04-16
g
conducted electrical signal at the at least one first data manipulation unit,
the time of
occurrence of lightning which produced the lightning-caused fault as
determined by the
at least one second data manipulation unit, and placement and path data of
related
individual power lines which are associated with the power distribution line
as provided
by a geographical information system.
By a third variant of this third broad aspect of this invention, and/or the
above
variants thereof, the conducted electrical signal comprises a conducted
electrical signal
which is generated by the lightning-caused fault on the power distribution
line, and the
first set of fault location data comprises a time of arrival at the at least
one first data
manipulation unit of the lightning-caused conducted electrical signal, the
time of arrival
of the lightning-caused conducted electrical signal and the time of occurrence
of lightning
which produced the lightning-caused fault being accurate to microsecond
accuracy as
made possible by the at least one first data manipulation unit and by the at
least one
second data manipulation unit being provided with, and utilizing, clocks that
are
synchronized by Global Positioning System (GPS) receivers, and the fault
location centre
comprises a power line fault locating analyzer, operative to receive the
communicated
time of arrival of the radiation at the at least one arc detection sensor,
manipulate stored
longitudinal and latitudinal information on the at least one arc detection
sensor, and
further to manipulate placement and path data of related individual power
lines which are
associated with the power distribution line as provided by a geographical
information
system for purposes of determining an exact location of the fault.
By a fourth variant of this third broad aspect of this invention, and/or the
above
variants thereof, the electromagnetic radiated signal data comprises low level
electromagnetic radiation (VHF/UHF) which is generated by arcing which is
associated
with a fault on the power distribution line, and the at least one second data
manipulation
unit comprises at least one electronic arc detection sensor having circuitry
that detects
the low level electromagnetic radiation and that manipulates the low level
electromagnetic
radiation for purposes of determining and communicating a time of arrival of
the low
level electromagnetic radiation at the electronic arc detection sensors.
CA 02232683 1999-04-16
9
By a fourth broad aspect of this invention, a power distribution line fault
locating
system is provided, the system comprising at least one first data manipulation
unit for
manipulating conducted fault signal data resulting from a fault on a power
distribution
line, and producing and communicating a first set of fault location data, at
least one
second data manipulation unit for manipulating electromagnetic radiated signal
data
emanating from the fault on the power distribution line and producing and
communicating
a second set of fault location data, and a power line fault locating analyzer,
which is
operative to determine a first path length between the at least one first data
manipulation
unit and the fault, and a second path length between the at least one second
data
manipulation unit and the fault, by utilizing the communicated first set of
fault location
data, the communicated second set of fault location data, and placement and
path data
of related individual power lines which are associated with the power
distribution line as
provided by a geographical information system for purposes of determining a
location
of the fault.
By one variant of this fourth broad aspect of this invention, the conducted
fault
signal data comprises a conducted electrical signal which is produced by the
fault, and
the at least one first data manipulation unit comprises at least one fault
recording sensor
unit for manipulating the conducted electrical signal, and producing and
communicating
the first set of fault location data, the at least one fault recording sensor
unit being
responsive to the conducted electrical signal for determining the time of
arrival of the
conducted electrical signal at the at least one first data manipulation unit,
the conducted
electrical signal being one of a plurality of conducted travelling wave
signals that travel
in opposite directions from a location of the fault.
By a second variant of this fourth broad aspect of this invention, and/or the
above
variant thereof, the electromagnetic radiated signal data comprises
electromagnetic
radiation data which is generated by a lightning-caused fault on the power
distribution
line, and the at least one second data manipulation unit comprises at least
one electronic
lightning locating system that manipulates the electromagnetic radiation data
such that the
second set of fault location data comprises a precise time of occurrence and
location of
lightning which produced the lightning-caused fault on the power distribution
line.
CA 02232683 1999-04-16
By a second variant of this fourth broad aspect of this invention, and/or the
above
variants thereof, the conducted electrical signal comprises a conducted
electrical signal
which is generated by the lightning-caused fault on the power distribution
line, and by
the first set of fault location data comprises a time of arrival at the at
least one first data
5 manipulation unit of the lightning-caused conducted electrical signal, the
time of arrival
of the lightning-caused conducted electrical signal and the time of occurrence
of lightning
which produced the lightning-caused fault being accurate to microsecond
accuracy as
made possible by the at least one first data manipulation unit, and by the at
least one
second data manipulation unit being provided with, and utilizing, clocks that
are
10 synchronized by Global Positioning System (GPS) receivers, and the power
line fault
locating analyzer further being operative to determine a first path length
between the at
least one first data manipulation unit and the lightning-caused fault, and a
second path
length between the at least one second data manipulation unit and the
lightning-caused
fault, by utilizing the time of arrival of the lightning caused conducted
electrical signal
at the at least one first data manipulation unit, the time of occurrence of
lightning which
produced the lightning-caused fault as determined by the at least one second
data
manipulation unit, and placement and path data of related individual power
lines which
are associated with the power distribution line as provided by a geographical
information
system.
By a third variant of this fourth broad aspect of this invention, and/or the
above
variants thereof, the electromagnetic radiated signal data comprises low level
electromagnetic radiation (VHF/UHF) which is generated by arcing associated
with a
fault on the power distribution line, and the at least one second data
manipulation unit
comprises at least one electronic arc detection sensor having circuitry that
detects the low
level electromagnetic radiation and that manipulates the low level
electromagnetic
radiation for purposes of determining and communicating a time of arrival of
the low
level electromagnetic radiation at the electronic arc detection sensor.
By a fourth variant of this fourth broad aspect of this invention, and/or the
above
variants thereof, the power line fault locating analyzer is operative to
receive the
communicated time of arrival of the radiation at the at least one arc
detection sensor, to
CA 02232683 1999-04-16
11
manipulate stored longitudinal and latitudinal information on the at least one
arc detection
sensor, and further to manipulate placement and path data of related
individual power
lines which are associated with the power distribution line as provided by a
geographical
information system for purposes of determining an exact location of the fault.
In other words, the present invention in its many aspects provides a lightning-
caused power line fault locating system, which employs lightning locating
systems (LLS)
and a fault recorder sensor (FRS) as is employed in a travelling wave fault
locating
system (TWFLS), both coupled to a central power line fault locating analyzer
(PLFLA)
that receives and manipulates lightning location information and conducted
power line
fault information to determine the location of the fault. The LLS is
responsive to high
level electromagnetic radiated fields which are generated by the lightning
discharge and
is capable of recording, to a microsecond level, the time of occurrence of the
lightning
stroke, as well as being capable of locating the lightning stroke with a known
accuracy.
The FRS provides the time of arrival, also to the microsecond level, of the
conducted
travelling wave which is generated by the fault. The information from the LLS
and FRS
is further manipulated at the PLFLA using appropriate algorithms and databanks
containing geographical maps of electric utility power systems to arrive at
the location
of the power line fault. The LLS provides the initial time of the fault-
producing
lightning discharge, so that only one FRS needs to be employed.
In one embodiment of a power line fault locating system of an aspect of this
invention, for either lightning or non-lightning caused faults, in addition to
a FRS, a
modified electronic version of the sensors which are used in a LLS system is
employed.
The modified sensors, termed "arc detection sensors" (ADS), are responsive to
low level
electromagnetic radiation (VHF/UHF) which is caused by arcing which is
associated with
a fault. At least one ADS is positioned at a predetermined location to sense
the time of
arrival of the radiated arc which is associated with a fault on a power line.
The time of
arcing information from the ADS and the time of arrival of the conducted
signal from
the FRS is communicated to the PLFLA for further manipulation, using
appropriate
algorithms and databanks containing geographical maps of electric utility
power systems
to arrive at the location of the power line fault.
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In an alternative embodiment, multiple ADS units which are located about a
power distribution network are provided such that the time of arcing
information, from
each of the ADS units, is communicated to the PLFLA to provide sufficient
information
to determine the exact location of a power line fault employing time-of
arrival location
methods, which are similar to those employed in lightning locating systems,
see paper
by Kenneth L. Cummins, et al. , entitled "LINE RELIABILITY AND FAULT
ANALYSIS USING THE NATIONAL LIGHTNING DETECTION NETWORK",
presented October 1993 at the Precise Measurement Power Conference, Arlington,
VA.
The PLFLA contains longitudinal and latitudinal information on each ADS as
well as the
geographical map of the power distribution system. The ADS type of power line
fault
locating system is entirely based on arc detection and does not require input
from a FRS
to determine the location of a fault.
(e) BRIEF DESCRIPTION OF THE DRAWINGS
In the accompany drawings:
FIG. 1 is a diagram illustration of a fault locating system arrangement for
implementing the travelling wave method of locating a fault on a power line;
FIG. 2 is a diagrammatic representation of a lightning caused fault on a power
distribution system and a fault locating system employing a electronic
lightning locating
system (LLS), a fault recorder sensor (FRS) responsive to the conducted fault
waveform,
a geographical information system (GIS) providing information about the
location of the
power lines, and a power line fault locating analyzer (PLFLA), in accordance
with an
embodiment of an aspect of the present invention;
FIG. 3 is a diagrammatic representation of a fault on a power distribution
system
and a fault locating system employing a pair of arc detection sensors (ADS) in
addition
to a fault recorder sensor (FRS) responsive to the conducted fault waveform,
and a power
line fault locating analyzer (PLFLA), in accordance with an embodiment of an
aspect of
the present invention; and
FIG. 4 is a diagrammatic representation of a fault on a power distribution
system
and a fault locating system employing only multiple arc detection sensors
(ADS) with a
CA 02232683 1999-04-16
13
power line fault locating analyzer (PLFLA), in accordance with an embodiment
of an
aspect of the present invention.
(fj DESCRIPTION OF THE PRIOR ART
FIG. 1 shows diagrammatically a prior art travelling wave method which
utilizes
the fact that a transient waveform is generated and is conducted away from a
fault F at
time TO. The fault waveforms propagate in opposite directions, along line L1,
L2 from
the fault with respective propagation times Tpl, Tp2. Knowledge of the times
of arrival,
T1, T2, at opposing measuring equipment, and characteristics about the line
being
monitored help in determining the distance that the wave has travelled from
the location
of the fault.
(g) AT LEAST ONE MODE FOR CARRYING OUT THE INVENTION
FIG. 2 shows a diagrammatic representation of a fault on a power distribution
system and a fault locating system employing an electronic lightning locating
system
(LLS), a fault recording sensor (FRS) responsive to conducted fault waveforms,
and a
power line fault locating analyzer (PLFLA) in accordance with an embodiment of
an
aspect of the present invention. The LLS detects and processes the
electromagnetic
radiation which is produced by a lightning discharge and communicates the
relevant
lightning information (precise time and location) to the PLFLA, to be combined
with the
arrival time of the conducted signal recorded by the FRS, also communicated to
the
PLFLA. This conducted signal will contain a waveform which is produced by the
lightning discharge, preceded by, or followed, in rapid succession by a
waveform which
is produced by the resulting fault current. Frequently, these two waveforms
will be
indistinguishable, as the location of the lightning discharge may also be the
precise
location of the fault along the line. Critical to the manipulation of the
information is that
both the LLS and FRS record the time of their respective events, being
monitored to
microsecond accuracy. In this embodiment, the precise timing is provided by
clocks
which are, for example, synchronized by Global Positioning System (GPS)
receivers.
The use of an LLS to determine the precise time of the lightning discharge
eliminates
CA 02232683 1999-04-16
14
having to employ a FRS at more than one location along the distribution line.
As a first
step in the location procedure, the path length between the FRS and the fault
is
determined by using the time of arrival at a FRS monitoring site of the
conducted wave
which is induced by a lightning on a power line, and the time of the lightning
event as
determined by a lightning location system (LLS), coupled with specific
knowledge of the
placement/path of related power lines as provided by a properly configured
geographical
information system (GIS). In cases involving multiple tap points along the
line, more
than one location will be consistent with the determined path length. This
ambiguity will
commonly be resolved with knowledge of the approximate location of the
lightning and
its estimated location error, as provided by the LLS.
An additional feature of this method is that if the fault occurs at a point
which is
farther from the FRS than the lightning discharge, it is possible to locate
both the
lightning stroke point and the fault location. This provides additional
information about
the insulation level of the line and identifies weak points along the line.
FIG. 3 is a diagrammatic representation of a fault on a power distribution
system
and a fault locating system employing a pair of arc detection sensors (ADS) in
combination with a fault recording sensor (FRS) and a power line fault
locating analyzer
(PLFLA) in accordance with an embodiment of an aspect of the present
invention. This
embodiment employs electronic circuitry in the ADS that is responsive to the
arc that
emits low level electromagnetic radiation, and which determines the arrival
time of the
electromagnetic radiation at each ADS. While primarily designed for detecting
the arc
which is associated with faults, the ADS may also include circuitry for
detecting
lightning discharges.
The information concerning the time of the arc which is detected by the ADS,
in
combination with the information concerning the time of arrival of the
conducted
travelling wave which is sensed by the FRS and the associated line pathway
which is
provided by the GIS are sufficient for determining the location of the fault.
Upon the
occurrence of a fault, the arc will generate a radiated signal, and the
arrival times of this
radiated signal is recorded at each of the ADS detectors. In the case where
only one
ADS detects the arc, the location of the fault on the line is determined using
a procedure
CA 02232683 1999-04-16
which iteratively moves an estimated fault location along the line, and
computes the
expected arrival time at both the ADS and the FRS sites, using the
geographical
information. Since the conducted signal must propagate along the power line,
and since
the radiated signal must travel a straight-line path between the arc and the
ADS, a unique
5 solution can be obtained. In the case where two ADS sensors detect the arc,
the
difference in arrival times of the radiated waveform at the two ADS sites is
used to
determine a hyperbola that is symmetrical about a line which is drawn between
the two
ADS. The point of intersection between the power line and this hyperbola is
the initial
estimate of the fault location. This estimate can then be improved upon or
verified by
10 considering the arrival time of the conducted fault waveform at the FRS.
Note that if
the fault occurred equidistant between the two ADS detectors, then the
hyperbola would
be a straight line which is equidistant from both ADS sites (See Cummins et
al., 1993
for a discussion of "relative time of arrival" method of hyperbolic
intersections).
FIG. 4 is a diagrammatic representation of a fault on a power distribution
system
15 and a fault locating system employing only multiple arc detection sensor
(ADS) with a
power line fault locating analyzer (PLFLA) in accordance with an embodiment of
an
aspect of the present invention. Here, three (3) or more ADS sites about a
power
distribution network are provided such that the arrival time of arcing
information at each
of the ADS sites is communicated to the PLFLA to determine the exact location
of a
power line fault. The PLFLA contains longitudinal and latitudinal information
on each
ADS site as well as the geographical map of the power distribution system. The
ADS
type of power line fault locating system of an embodiment of an aspect of the
present
invention is based entirely on arc detection and does not require input
regarding the
conducted waveform to determine the location of a fault.
