JPS6022736Y2 - voltage detection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a voltage detection device for gas insulated equipment.

The voltage detection section of conventional gas-insulated equipment has a structure as shown in Fig. 1, and uses the high-voltage lead 1 in the conduit 4 and the capacitance between the terminal 1' and the intermediate electrode 2. A current i proportional to the voltage of the high-voltage lead 1 and its terminal 1' is drawn out from the intermediate electrode 2 via the lead draw-out bushing 7 to the outside of the case lid 60 of the case 6.

A case 6a is attached to the case lid 60, and a highly insulating gas 8 such as SF6 gas or N2 gas is sealed inside the case 6.

A capacitor C2 is provided inside the case 6a, and the current drawn to the outside via this capacitor C2 is grounded as shown in FIGS. 1 and 2, and the voltage applied across the capacitance C2 of the capacitor C2 is is transmitted to the power amplifier 11 via the transmission cable 10.

In FIG. 2, a signal voltage appearing at the end of a transmission cable 10 is amplified by a power amplifier 11, and a meter 12 and various relays 13 are operated.

In other words, 50Hz or 60Hz of gas insulated equipment lines
The voltage of
The configuration is such that the voltage is divided into s/ (C1 + C2) and the power is amplified and measured.

Here, as 02, a mica capacitor or a ceramic capacitor is used, which has a small rate of capacitance change due to temperature.

By the way, gas insulated equipment to which such a power detection device is connected usually has gas insulated switches and gas insulated breakers, which are not shown in Fig. Opening/closing surges (several tens of MHz) occur in the line.

For such high frequencies, the residual inductance of C1 is small and can be ignored, but the residual inductance of C2 cannot be ignored and is not divided by CI/(C□+C2).

In other words, a partial pressure configuration as shown in FIG. 3 with the same reference numerals as in FIG. 2 is obtained.

That is, FIG. 3 is an equivalent circuit showing a capacitor C2 broken down into an internal inductance h and a pure capacitor C'2.

For high frequency voltage of several M to several 10 MHz, C1C
'2 does not have a large impedance, and the impedance of the inductance L2 becomes very large.

Therefore, in high-frequency switching surges, the normal partial pressure ratio CI/
This results in a voltage greater than (C + C2) being applied to the voltage divider circuit terminal 14.

When an excessive switching surge voltage corresponding to the terminal of the bushing 7 in FIG.
1 and voltage dividing capacitor C2 or cause malfunction.
Occasionally, phenomena can occur that mimic the sparking of the reed drawer bushing 7 of FIG. 1, leading to havoc in the system's protection system.

As a countermeasure, reduce the residual inductance L2 of the voltage dividing capacitor C2, and also reduce the residual inductance L2 of the voltage dividing capacitor C2, and increase the
All you have to do is divide the pressure.

However, with current capacitor manufacturing technology, it is difficult to manufacture a capacitor with a large capacitance and a negligible residual inductance from several megahertz to several tens of MHz.

The present invention has been made in consideration of the above-mentioned drawbacks, and an object of the present invention is to provide a voltage detection device that prevents high-frequency surges from entering a voltage dividing circuit.

An embodiment of the present invention is shown in FIG. 4, in which the same parts as in FIG. 1 are given the same reference numerals.

As shown in FIG. 4, the high voltage lead 20 is configured as a spiral conductor.

The details of the high voltage lead 20 are shown in FIG. 5, and the portion facing the intermediate electrode 2 in FIG. 4 between the cylindrical high voltage lead 21 and its terminal 21' is configured in a spiral shape.

With this configuration, the current flowing into the intermediate electrode 2 flows through the spiral conductor 20 in a spiral shape, so that
This is equivalent to flowing in through the inductance in series.

The equivalent circuit is shown in FIG. 6, and it is equivalent to connecting an inductance L in series with the capacitance C1.

Due to the presence of this inductance h, the high frequency switching surge is added to the inductance L1, and the low voltage dividing circuit terminal 14
will not be able to participate.

As mentioned above, in conventional voltage detection devices, an excessive surge is applied to the terminal 14 due to the influence of the residual inductance L2 of the voltage dividing capacitor C2 at high frequencies.One of the reasons for this is as shown in Fig. 1. High voltage lead 1 and terminal 1' shown
The difference between the capacitance and the intermediate electrode 2 is that the electrodes are coaxial and have almost no inductance.

Therefore, by connecting the inductance L1 in series with the capacitance T, an extremely high surge will not be applied to the terminal 14.

Suppression of high frequency surges by the voltage detection device of the present invention will be explained with reference to FIG.

In Figure 6, where the same parts as in Figure 2 are given the same symbols,
Ll is the inductance 20 in FIG.

For high frequencies of several MHz to several tens of MHz, the capacitances g1 and C'2 have low impedance and are divided by the impedance of the inductances L1 and h.

If we reduce the pitch 30 of the spiral conductor 20 in Fig. 5 and increase the number of turns, we can obtain the condition L□〉〉L2. In this case, most of the high frequency switching surge V' is added to h, resulting in a low voltage. The surge level at the input terminal 14 of the voltage divider circuit can be significantly reduced.

A detailed view of the high voltage lead portion of another embodiment of the present invention is shown in FIG.

A spiral groove 22 as shown in the figure is provided between the terminal 20' and the high voltage lead 21.

Even if a high voltage lead having such a structure is attached to the apparatus shown in FIG. 4, the same effect as the present invention can be obtained.

That is, high frequency current flows on the surface of the conductor due to the skin effect.

Therefore, when a spiral groove 22 is formed on a high-voltage conductor as shown in Figure 7, the high-frequency current tends to flow through the convex part 23 in the figure, and since the convex part 23 has a spiral shape, the high-frequency current also circulates in a spiral shape. In the end, the current flowed through the inductance.

That is, the high voltage lead having the structure shown in FIG. 7 can also provide the same surge suppressing effect as the high voltage lead having the structure explained in FIG.

As described above, according to the present invention, it is possible to significantly reduce high-frequency switching surges that enter the low-voltage dividing circuit of the voltage detection section, and it is possible to prevent damage to the power amplifier due to switching surges and sparks in the mud drain bushing, thereby making it reliable. A voltage detection device with high performance can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the voltage dividing section of a conventional voltage detection device for gas-insulated equipment, Figs. 2 and 3 are explanatory diagrams of the circuit of the conventional device, and Fig. 4 is a diagram of the voltage detection device of the present invention. 5 and 7 are enlarged explanatory views of different main parts of the voltage detection device of the present invention, and FIG. 6 is a circuit configuration diagram illustrating the present invention. 1... High voltage lead of gas insulated equipment, 1'...
...Terminal, 2...Intermediate electrode, 7...
Output lead drawer bushing, 11... Power amplifier, 20... Spiral high voltage lead, 2
2...High pressure lead with spiral groove.

Claims (1)

[Scope of utility model registration request] The voltage of the high-voltage conductor of gas-insulated equipment is divided by the capacitance between this conductor and the intermediate electrode, and by the voltage dividing capacitor connected externally, and the divided voltage is transmitted through the transmission cable, and the received signal is sent to the amplifier. In the voltage detection device, an inductance portion formed by a spiral conductor or a spiral groove is formed in the high voltage lead.