Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2001-01-09
2003-12-09
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S460000, C324S464000
Reexamination Certificate
active
06661234
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a failure determining apparatus of a gas-insulated electrical appliance, which determines presence or absence of ground-fault or short-circuit of a charged conductor in a gas section, by detecting a change in the gas pressure in the gas section forming the gas-insulated electrical appliance.
2. Description of the Related Art
A gas-insulated electrical appliance has a cylindrical metal container housing therein a charged conductor corresponding to a single phase or three phases. The former has a risk of suffering from a ground-fault of the charged conductor to the metal container, and the latter, ground-fault of charged conductor of each phase to the metal container and short-circuit between the charged conductors of different phases. Since these inconveniences are similarly covered by the present invention, only the former case will herein be described.
A conventional failure determining apparatus of a gas-insulated electrical appliance will first be described with reference to the drawings.
FIG. 17
illustrates the configuration of the conventional failure determining apparatus of a gas-insulated electrical appliance.
In
FIG. 17
,
1
represents a cylindrical metal container to be filled with an insulating gas;
2
, a charged conductor housed in the metal container
1
; and
3
a
,
3
b
and
3
c
, insulating spacers partitioning the metal container
1
into gas sections and insulation-supporting the charged conductor
2
.
Also in
FIG. 17
,
11
represents a gas pressure detector detecting a gas pressure signal corresponding to a gas pressure of a gas section for comprehensive control through communicating piping, attached to the metal container
1
;
12
, a sampling circuit sampling a gas pressure signal issued by the gas pressure detector
11
after the lapse of a prescribed period of time by input of a ground-fault current detection signal from outside;
13
, a failure determining circuit which determines occurrence of a ground-fault if a sampled gas pressure is larger than a threshold value through comparison of the gas pressure signal sampled at the sampling circuit
12
and the threshold value.
Operations of the conventional failure determining apparatus of a gas-insulated electrical appliance will now be described with reference to the drawings.
FIG. 18
is a waveform diagram showing a gas pressure signal detected by the gas pressure detector of the conventional failure determining apparatus of a gas-insulated electrical appliance.
For one of the gas sections formed by partitioning the metal container
1
by means of insulating spacers
3
a
and
3
b
under comprehensive control through a communicating piping, when a ground-fault occurs between the charged conductor
2
and the metal container
1
, the pressure of the insulating as in this gas section suddenly increases near the arc, leading to production of a pressure wave. The gas pressure detector
11
detects a gas pressure signal based on superposition of a gas dynamic pressure signal corresponding to a dynamic pressure of the insulating gas of this pressure wave on a gas state pressure signal corresponding to the static pressure of an auxiliary gas filling the neighboring gas section connected by the communicating piping.
This gas pressure signal and a ground-fault current detection signal from outside after the lapse of a prescribed period of time from the occurrence of the ground-fault are entered into the sampling circuit
12
. Therefore, the gas pressure signal P
2
at the point in time T
2
when a prescribed period of time t from the point in time T
1
when this ground-fault current detection signal has been entered is sampled (see FIG.
18
).
In the failure determining circuit
13
, occurrence of a ground-fault is determined if the sampled gas pressure signal P
2
is larger (the gas pressure signal P
2
is larger in FIG.
18
).
Although not shown in
FIG. 17
, the gas pressure detector
11
is attached to the metal container
1
, also for the other gas sections, to determine occurrence of a ground fault by connecting the same to the sampling circuit and the failure determining circuit.
In the conventional failure determining apparatus of a gas-insulated electrical appliance, as described above, the gas pressure signal P
2
is sampled at the point in time T
2
upon the lapse of the prescribed period of time t from the point in time T
1
of input of the ground-fault current detection signal, on the assumption that the gas pressure signal detecting by the gas pressure detector
11
takes substantially the shape shown in FIG.
18
. The sampled signal is compared with a prescribed threshold value Pt, and if the gas pressure signal P
2
is larger, occurrence of a ground-fault is determined. However, the increase in gas pressure may differ from that shown in
FIG. 18
under the effect of the size of the metal container
1
arranged between the insulating spacers
3
a
and
3
b
, the arc energy upon occurrence of the ground-fault, or the duration of the ground-fault. Because a threshold value cannot be primarily set, a problem is encountered in that the presence of occurrence of a ground-fault cannot accurately be determined.
SUMMARY OF THE INVENTION
The present invention was developed to solve the above-mentioned problems, and has an object to provide a failure determining apparatus of a gas-insulated electrical appliance, which permits improvement of certainty of determination through a combination of sensors of different types for the purpose of accurately identifying a gas section in which a ground-fault occurs without being affected by conditions upon occurrence of the ground-fault such as structural restrictions including the interval between the insulating spacers, the arc energy produced upon occurrence of the ground-fault, and the duration, thus permitting reduction of the trouble eliminating operations upon occurrence of an accident.
The failure determining apparatus of a gas-insulated electrical appliance of a first aspect of the present invention determining a failure, having a cylindrical metal container, a charged conductor housed in the metal container filled with an insulating gas, and a plurality of insulating spacers insulation-supporting the charged conductor from the metal container and partitioning the interior of the metal container into gas sections, comprises a high-speed developing sensor which detects a high-speed phenomenon caused by a failure such as a ground-fault or a short-circuit within the gas sections; a first failure determining circuit which determines the presence of a failure from an output of the high-speed developing sensor; a low-speed developing sensor which detects a low-speed phenomenon caused by a failure such as a ground-fault or a short-circuit within the gas sections; a second failure determining circuit which determines the presence of a failure from an output of the low-speed developing sensor; and an arithmetic control circuit which identifies a gas section of the metal container in which a failure occurs from an output of the first and second failure determining circuits.
The failure determining apparatus of a gas-insulated electrical appliance determining a failure of a second aspect of the invention, having a cylindrical metal container, a charged conductor housed in the metal container filled with an insulating gas, and a plurality of insulating spacers insulation-supporting the charged conductor from the metal container and partitioning the interior of the metal container into gas sections, comprises a gas pressure detector which detects a change in the gas pressure of the gas sections; a first sampling circuit which fetches a change in the gas pressure from the gas pressure detector on the basis of a failure current detection signal; a failure determining circuit which determines an accident occurring gas section when a change in gas pressure fetched by the first sampling circuit is over a first threshold value; a decomposed gas detector which performs detection by ioni
Aoki Hirohide
Doi Hiroshi
Hama Hiroyuki
Honda Yoshikatsu
Kajita Naoyuki
Le N.
Mitsubishi Denki & Kabushiki Kaisha
Teresinski John
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