JPH04370684A - Sealed type lighting arrester - Google Patents

Abstract

PURPOSE:To lessen voltage drop on the grounding lead of a lightning arrester and a grounding mesh as much as practicable. CONSTITUTION:A bus bar 11 of a gas insulated apparatus (GIS) is installed in a bus bar tank 13 in which SF6 gas 12 is encapsulated. A lightning arrester tank 16 is mounted on this bus bar tank 13, and an arrester element 17 is provided in the arrester tank 16. An arrester grounding lead 18 is connected with a grounding mesh 15, and a bushing 19 is set between the arrester grounding lead 18 and arrester tank 16 to generate insulation therebetween. A protection device 20 for lessening an influence of transient voltage appearing on the arrester grounding lead 18 and grounding mesh 15 is installed between the arrester grounding lead 18 and the arrester tank 16. This protection device 20 is formed, concretely described, for example from a non-linear resistant element which presents a high resistance in the large current region and a low resistance in the small current region. This accomplishes suppressing impression of over-voltage between the bus bar 11 and the main circuit insulation of bus bar tank 13 even in the event of flowing of a steep discharge current.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to gas insulated equipment (GIS).
) The present invention relates to a sealed lightning arrester for protection, and particularly relates to a sealed lightning arrester that can increase the protective effect of the lightning arrester even if the arrester is activated by a steep lightning surge voltage or the like.

0002

[Prior art] Gas insulated equipment (hereinafter referred to as GIS)
In general, lightning arresters installed in substations, etc., have their grounding wires connected to the substation mesh, and the AC resistance of the substation's grounding mesh is usually 1Ω or less, which is a sufficiently low value. .

FIG. 8 shows a sealed lightning arrester in a conventional GIS. In the figure, reference numeral 1 is a busbar, and this busbar 1 is placed in a busbar tank 3 filled with SF6 gas 2. 3 is connected (earthed) to a ground mesh 5 via a GIS ground line 4.

As shown in FIG. 8, the busbar tank 3 is provided with a surge arrester tank 6, and this surge arrester tank 6 has a built-in surge arrester element 7. It is connected to the ground mesh 5. Further, the surge arrester grounding line 8 and the surge arrester tank 6 are insulated by a bushing 9.

[0005]

[Problems to be Solved by the Invention] In a conventional sealed lightning arrester, when a steep overvoltage such as a lightning surge voltage E is applied to the bus 1, as shown in FIG. flows. For example, if a steel tower near a substation is struck by lightning and a lightning surge enters the substation due to reverse flashover, the peak value of the discharge current of the lightning arrester will be 20,000 A.
, the time to the wave crest is 1 μs, so the current steepness is 20
000A/μs.

[0006] In this way, when a steep current flows through the arrester element 7 to the arrester grounding line 8 and the grounding mesh 5, these systems not only act as resistive impedance, but also cause an inductance drop Ldi/dt, which Inductance drop becomes the main voltage effect.

FIG. 9 shows the overvoltage generated in various parts due to such a steep arrester discharge current, and FIG. 9(a) shows the steep discharge current waveform flowing through the arrester, and FIG. 9(b) shows the limiting voltage waveform of a single zinc oxide arrester with respect to the discharge current. FIG. 9(c) is
The transient voltage waveform appearing in the ground system is also shown in Figure 9(d).
Each shows a voltage waveform that is a combination of the limit voltage and the ground system voltage.

Voltage-current (V-I) of zinc oxide type lightning arrester
As shown in Fig. 10, the characteristics are extremely excellent in non-linearity, reaching a high limiting voltage even in a small current range.Therefore, the time response of the limiting voltage waveform shown in Fig. 9(b) is also
This shows a faster response to the rising voltage than the discharge current waveform shown in FIG. 9(a).

On the other hand, the grounding system of the lightning arrester grounding wire 8 and the grounding mesh 5 has Ldi/dt as shown in FIG. 9(c).
The inductance drop 11 is larger than the resistance drop 12 and becomes the main voltage drop. The peak value of the inductance drop Ldi/dt occurs at the point where the steepness of the rise of the current i is maximum. The maximum value of current steepness di/dt occurs in a small current range before the current peak value shown in Fig. 9(a), but the limiting voltage of zinc oxide type arresters is relatively high even at small currents, as mentioned above. Therefore, the total voltage obtained by combining the waveform of FIG. 9(b) and the waveform of FIG. 9(c) is as shown in FIG. 9(d).
As shown in the figure, the waveform has a maximum value in a short time domain. This voltage is applied to the main insulation of the GIS between the busbar 1 and the busbar tank 3. Therefore, the GIS main insulation must be determined to withstand not only the voltage limit of the lightning arrester but also the overvoltage including the voltage drop in the grounding system.

As can be seen from the inductance drop 11 of Ldi/dt, the magnitude of the transient overvoltage appearing in such a grounding system increases as the lightning arrester grounding wire 8 becomes longer and as the grounding mesh 5 becomes more incomplete. , and further the current steepness di/
The larger dt is, the higher the value becomes, which is not preferable.

However, due to the layout of the GIS, the surge arrester grounding wire 8 may be long and the inductance L may have to be large, and no matter how safely the grounding mesh 5 is stretched, the conductor itself may have an inductance drop. (descent), which makes the GIS uneconomical.

The present invention has been made in consideration of the above-mentioned circumstances, and it is an object of the present invention to provide a sealed lightning arrester that can minimize the voltage drop in the grounding system, which is a combination of inductance drop and resistance drop. shall be.

[0013]

[Means for Solving the Problems] As a means for achieving the above object, the present invention provides a method for arranging a busbar in a busbar tank, connecting a lightning arrester tank having a built-in lightning arrester element to the busbar tank, and In a sealed type lightning arrester for GIS protection in which the grounding side of the arrester element is insulated from the tank, in order to reduce the influence of transient overvoltage appearing on the grounding system between the grounding side lead of the arrester element and any of the tanks. It is equipped with a protective device.

In the present invention, the protective device is a nonlinear resistor that exhibits high resistance in a large current range and low resistance in a small current range, or a capacitor that has a time constant that can alleviate the rise of overvoltage appearing in the ground system. Alternatively, it is preferable that the protective gap is configured to discharge at a predetermined voltage, or that the protective gap and the non-linear resistor are connected in series.

[0015]

[Operation] In the sealed type surge arrester according to the present invention, a protection device is provided between the ground side lead of the surge arrester element and the bus tank or the surge arrester tank. Therefore, when a steep discharge current flows, the overvoltage that appears in the ground system is
The voltage applied between the GIS busbar and the main circuit insulation of the busbar tank is suppressed as much as possible, making it possible to reduce the voltage drop in the ground system as much as possible.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sealed lightning arrester according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of a sealed lightning arrester according to the present invention, and in the figure, reference numeral 11 indicates gas insulated equipment (GIS).
), and this bus bar 11 is arranged in a bus bar tank 13 filled with SF6 gas 12.
is connected to the ground mesh 15 via the GIS ground line 14.

As shown in FIG. 1, the bus tank 13 includes:
A lightning arrester tank 16 is provided, and a lightning arrester element 17 is built into the lightning arrester tank 16, and the lightning arrester element 17 is connected to the ground mesh 15 via a lightning arrester grounding wire 18.
It is connected to the. Further, the surge arrester grounding wire 18 and the surge arrester tank 16 are insulated by a bushing 19.

As shown in FIG. 1, a protection device 20 is provided between the surge arrester grounding wire 18 and the surge arrester tank 16, and this protection device 20 prevents the surge arrester from flowing when a steep discharge current flows through the surge arrester. The overvoltage appearing in the ground system can be suppressed as much as possible from being applied between the GIS bus bar 11 and the main circuit insulation of the bus tank 13.

The conditions required of this protection device 20 will be explained with reference to the equivalent circuit shown in FIG. In the figure, code 22
is the overvoltage of the grounding system, 23 is the gap between the arrester tank 16 and the arrester grounding wire 18, 24 is the inductance L1 of the grounding mesh 15, and 25 is the inductance L2 of the arrester tank 16 and the arrester grounding wire 18.

In FIG. 2, in order to significantly reduce the overvoltage e appearing in the gap 23 when the protection device 20 is activated, it has a sufficiently low impedance compared to the impedance due to the inductance of (L1 +L2).
Further, after the overvoltage e ends, it is necessary to restore the impedance to a sufficiently high value, and this is a condition required of the protection device 20.

Specific examples of the protection device 20 that satisfy these conditions are shown in FIGS. 3 to 6, respectively.

FIG. 3 shows the protection device 20 for the nonlinear resistor 28.
The case where this non-linear resistor 2 is applied as an element is shown.
As 8, for example, a zinc oxide element or a silicon carbide resistor can be considered. These are the voltage-current (
As shown in the VI) characteristics, it exhibits high resistance in the large current range and low resistance in the small current range, meeting the above conditions.

FIG. 4 also shows that the capacitor 29 is connected to the protection device 2.
0 element, this capacitor 2
By increasing the capacitance of 9 to obtain a time constant that can alleviate the rise of overvoltage appearing in the grounding system, the voltage appearing in gap 23 in FIG. 2 can be made sufficiently higher than overvoltage e. It can be set to a lower value.

FIG. 5 shows a case where the protective gap 30 is applied as an element of the protective device 20. By appropriately setting the discharge voltage of the protective gap 30, the voltage appearing in the gap 23 of FIG. The value can be made sufficiently lower than the overvoltage e. Note that the conditions for this protective gap 30 are that it has a function of discharging at a predetermined voltage without discharge delay or variation, and that there is little wear and tear due to discharge current.

Furthermore, FIG. 6 shows a case where a system in which a protective gap 30 and a non-linear resistor 28 are connected in series is used as an element of the protective device 20. By limiting the protection gap 3
0 wear can be further reduced.

By using such a protection device 20, overvoltage as shown in FIG. 9(d) can be prevented from occurring in the GIS.
The voltage is no longer applied to the main insulation part of the
) can be set to a value close to the arrester limit voltage shown in ). Therefore, an increase in the required insulation level of the entire GIS is suppressed, and an economical GIS can be obtained.

FIG. 8 shows a second embodiment of the present invention, in which a protection device 20 is housed within a lightning arrester tank 16. In other respects, the structure is the same as that of the first embodiment, and the operation is also the same.

[0029] Therefore, the protection device 20 is connected to the lightning arrester tank 1.
6, the protection device 20 is not exposed to wind and rain, so there is no need to store the protection device 20 in a separate airtight container or the like, and the protection device 20 can be made compact.

In this way, by configuring the protection device 20 with a system in which the nonlinear resistor 28, the capacitor 29, and the protective gap 30, or the protective gap 30 and the nonlinear resistor 28 are connected in series, stable performance can be achieved. protective equipment can be easily obtained.

In both of the above embodiments, the case where the protection device 20 is provided between the lightning arrester tank 16 and the lightning arrester grounding wire 18 has been described, but it may also be provided between the busbar tank 13 and the lightning arrester grounding wire 18. Similar effects can be expected.

[0032]

As explained above, the present invention provides a protection device between the ground side lead of the surge arrester element and the bus tank or the surge arrester tank to reduce the influence of transient overvoltage appearing on the ground system. Therefore, it is possible to minimize the voltage drop in the grounding system and obtain an economical GIS.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a sealed lightning arrester according to the present invention.

FIG. 2 is an equivalent circuit diagram of FIG. 1.

FIG. 3 is an explanatory diagram showing a specific example of using a nonlinear resistor as an element of a protection device.

FIG. 4 is an explanatory diagram showing a specific example of using a capacitor as an element of a protection device.

FIG. 5 is an explanatory diagram showing a specific example of using a protection gap as an element of a protection device.

FIG. 6 is an explanatory diagram showing a specific example in which a protection gap and a non-linear resistor are connected in series as elements of a protection device.

FIG. 7 is a configuration diagram showing a sealed lightning arrester according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram showing a conventional sealed lightning arrester.

[Figure 9] (a) is a graph showing the steep discharge current waveform flowing through the arrester, (b) is a graph showing the limiting voltage waveform of a single zinc oxide arrester against discharge current, and (c) is a graph showing the transient that appears in the grounding system. Graph showing a voltage waveform; (d) is a graph showing a voltage waveform obtained by combining the limit voltage and the ground system voltage.

FIG. 10 is a graph showing the VI characteristics of a zinc oxide type lightning arrester.

[Explanation of symbols]

11 Bus line 12 SF6 gas 13 Busbar tank 15 Ground mesh 16 Lightning arrester tank 17 Lightning arrester element 18　Surge arrester grounding wire 19 Bushing 20 Protective device 28 Nonlinear resistor 29 Capacitor 30 Protection gap

Claims (1)

[Claims] Claim 1: A sealed type for GIS protection in which the bus bar is placed in a bus tank, a surge arrester tank containing a built-in surge arrester element is connected to the bus tank, and the ground side of the surge arrester tank and the surge arrester element are insulated. In lightning arresters,
A sealed lightning arrester, characterized in that a protection device is provided between the grounding side lead of the lightning arrester element and any of the tanks for reducing the influence of transient overvoltage appearing in the grounding system.