JPH0128911B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealed gas insulating device using a highly insulating gas such as SF ₆ as an insulating medium. To explain in more detail, this invention includes a capacitive coupling plate placed around a high voltage conductor in a sealed tank, and a Rogovski coil placed around this capacitive coupling plate to prevent corona generation. The present invention relates to a sealed gas insulating device that detects where an abnormality such as the above occurs.

Conventionally, this was the first sealed gas insulator of this type.
I got what is shown in the figure. In this sealed gas insulation device, a grounded cylindrical sealed tank 1 is filled with a highly insulating gas such as SF ₆ as an insulating medium.
Further, a high voltage conductor 3 is coaxially disposed within this sealed tank 1 with a spacer 2 interposed therebetween. 4 is a power source that supplies high voltage power to the high voltage conductor 3, and is connected to the high voltage conductor 3 via a line impedance 5, and is also directly connected to the sealed tank 1. The capacitive coupling plate 6 is made of a short cylindrical conductor.
In order to detect abnormalities such as the occurrence of corona, it is disposed coaxially around the high voltage conductor 3 and is electrostatically coupled to the high voltage conductor 3. A low-voltage capacitor C ₂ is connected between the capacitive coupling plate 6 and the sealed tank 1, and a corona detection unit 7 is connected to the low-voltage capacitor C ₂ , which receives the voltage between its terminals as input.
R is a sense resistor connected in parallel with the low voltage capacitor _C2 .

In the conventional sealed gas insulating device configured as described above, if a corona S occurs at a certain position on the high voltage conductor 3, the voltage of the power source 4
FIG. 2 shows the waveforms of E ₀ sin ωt, the corona current i _s (t), and the input voltage e(t) of the corona detection section 7. The corona current i _s (t) due to the generation of the corona S flows as a steep pulse-like current shown by b near the peak of the power supply voltage E ₀ sinωt, and therefore the power supply voltage decreases only for a short time as shown by a. This voltage is divided by the capacitance C1 of the capacitive coupling plate ₆ and the capacitance of the low voltage capacitor _C2 , but if the resistance value of the detection resistor R is selected to be small, it will be input to the corona detection section 7. The input voltage e(t) contains only high frequency components as shown by c. By detecting the magnitude of such pulses, the corona detection section 7 can determine whether or not corona is occurring within the entire device, as well as the degree of danger of the corona.

However, with conventional equipment like this, it is not possible to detect the position where corona is occurring, so even if corona is detected, it is not possible to tell where the abnormality is occurring, so it is necessary to inspect the entire equipment to confirm the abnormal position. I needed to.

Therefore, in order to solve the problems of the conventional device as described above, the present invention has a configuration that can detect not only high-frequency voltage but also current using corona, and it is possible to detect corona generation sources either before or after the detection point. The object of the present invention is to provide a new sealed gas insulating device that can detect and determine the presence of gas.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. Detection resistors R _C and R _L are connected between these detection resistors, respectively.
A multiplier 12 operating at high frequency for multiplying the R _C and R _L signals, a gate circuit 13 to which the output of the multiplier 12 is applied, and the output of the gate circuit 13 determines the corona occurrence position and its location. A determining unit 14 for determining the direction is connected as shown.

Next, the operation will be explained. As described above, when the corona S occurs, the steep corona current i _s (t) shown by b in FIG. 2 flows.
On the other hand, when the high voltage conductor 3 and the sealed tank 1 take the form of a coaxial cable, and a steep corona current flows through a portion thereof, a surge propagates to both sides around that portion. The characteristic impedance of this line is Z
If the surge voltage and current at a certain point are v(t) and i(t), respectively, then v(t)=±Zi(t) (1) holds true. Here, either sign of ± is established depending on the difference in the propagation direction of the surge. For example, if the direction of i(t) is determined as shown by arrow P in FIG. 4, + for surge 21 propagating from left to right, and - for surge 22 propagating from right to left. corresponds. In the waveform of i(t) in FIG. 5, the solid line represents a surge propagating from left to right, and the broken line represents a surge propagating from right to left.

Now, when we investigate what kind of voltage is induced in each part of the device when a surge associated with the corona generated in a closed gas insulated device propagates, we first find that the voltage e _C induced in the capacitive coupling plate 6 is is expressed as e _C = R _C C ₁ v'(t) (2). However, v'(t) means dv(t)/dt, and _C1 is the capacitance between the capacitive coupling plate 6 and the high voltage conductor 3, which is expressed by the following equation.

C ₁ =2πε ₀ l/lnr ₂ /r ₁ (3) Here, ε ₀ is the permittivity of vacuum, l is the length of the capacitive coupling plate 6 as shown in FIG. 4, and r ₁ and r ₂ are These are the radii of the high voltage conductor 3 and the capacitive coupling plate 6, respectively.

According to equation (2), the waveform of e _C is a differentiated form of v(t), as shown in FIG.

Next, the voltage e _L induced in the Rogovski coil is
is expressed as e _L =Mi′(t) (4) assuming that R _L is sufficiently larger than the internal impedance of the coil. Here, i'(t) means di(t)/dt, and M is the mutual inductance between the Rogovsky coil 11 and the high voltage conductor 3, which is expressed by the following equation.

M=nε ₀ A/2πr ₃ (5) where n is the number of turns of the coil, A and r ₃ are the cross-sectional area and average radius of the Rogovsky coil as shown in FIG.

According to equation (5), the waveform of e _L is a differentiated form of i(t), and as shown in FIG. 5, there are two types, a solid line and a broken line, depending on the direction in which the surge advances.

The output w(t) of the multiplier 12 becomes w(t)=R _C C ₁ Mv'(t)·i(t) (6) from equations (2) and (4). Substituting the differential of equation (1) into this equation yields w(t)=±R _C C ₁ M/Z[v′(t)] ² (7). Here, the + and - signs correspond to the positive direction surge 21 and negative direction surge 22 in FIG. 4, respectively. That is, w(t)≧0 or w(t)≦0 depending on the direction in which the surge propagates.
This is shown in FIG. 5 by solid and broken line waveforms. Therefore, depending on whether w(t) is positive or negative, it is possible to determine from which direction the surge has propagated to the detection point, that is, the direction of the corona generating device.

Furthermore, in reality, in a sealed gas insulated device, the characteristic impedance changes discontinuously at the inlet and outlet, so the surge is reflected at these parts and returns to the original direction. Therefore, a phenomenon occurs in which the sign of the output w(t) of the multiplier 12 is reversed when the reflected surge returns. In such a case, the direction of the corona source needs to be determined by capturing the first wave of the surge. A gate circuit 13 is provided for this purpose, and closes to block any input signal after a certain period of time has elapsed after an abnormal signal is generated due to the occurrence of corona. Note that the above-mentioned certain period of time until the gate circuit 13 closes must be less than or equal to the time it takes for the abnormal signal to travel back and forth between the detection section and the end of the device. The determining unit 14 determines the size and direction of the corona source based on the output of the gate circuit 13.

In the embodiment described above, the detection section, that is, the capacitive coupling plate 6, the Rogovski coil 11, the detection resistors R _C and R _L , the multiplier 12, the gate circuit 13, and the discrimination section 14 are arranged in one place. By providing these at several locations as appropriate, the location of the corona source can be determined more precisely.

Further, although the above-mentioned embodiment is a phase-separated type, that is, an example in which the high voltage conductors are arranged coaxially, the present invention can also be applied to a three-phase integrated type in which all three phases are housed in a single sealed tank. In this case, if the capacitive coupling plate and the Rogowski coil are arranged to surround the entire three-phase high voltage conductor, it is easy to obtain the same effect as in the above embodiment. You will understand.

As is clear from the above description, according to the present invention, a Rogovsky coil is provided in addition to the capacitive coupling plate, and the position of the corona source can be determined by focusing on the propagation direction of the surge accompanying corona generation. This has the excellent effect of streamlining equipment maintenance and inspection.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view showing the schematic configuration of a conventional closed type gas insulating device, Fig. 2 is a voltage and current waveform diagram for explaining the operation of the closed type gas insulating device shown in Fig. 1, and Fig. 3 The figure is a partially cutaway perspective view showing a schematic configuration of an embodiment of the present invention, FIG. 4 is a partially enlarged view of FIG. 3, and FIG. 5 is an operation of the embodiment shown in FIGS. 3 and 4. It is a voltage and current waveform diagram for explanation, and the same parts are indicated by the same symbols. 1... Sealed tank, 3... High voltage conductor, 6...
Electrostatic coupling plate, 11...Rogovsky coil, 12
... Multiplier, 13 ... Gate circuit, 14 ... Discrimination section, R _C and R _L ... Detection resistor.

Claims (1)

[Scope of Claims] 1. In a sealed gas insulating device in which an insulating medium is filled in a sealed tank and a high voltage conductor and a capacitive coupling plate are arranged surrounding the high voltage conductor, the area around the capacitive coupling plate is a Rogovski coil disposed in the electrostatic coupling plate and a multiplier that operates at a high frequency by applying the outputs of the capacitive coupling plate and the Rogovsky coil; 1. A closed type gas insulating device, comprising: a determining section that determines a direction. 2. In a sealed gas insulating equipment in which an insulating medium is filled in a closed tank and a high voltage conductor and a capacitive coupling plate are arranged surrounding the high voltage conductor, a Rogovski coil, a multiplier that operates at a high frequency when the outputs of the capacitive coupling plate and the Rogovski coil are applied, and the multiplier closes to block the output after a certain period of time has elapsed after the output of the multiplier is generated. What is claimed is: 1. A closed type gas insulating device comprising: a gate circuit for determining the direction of a source of an abnormal signal based on the polarity of the output that has passed through the gate circuit;