JPS5831087A - Electrolytical corrosion proof method for underground buried transformer - Google Patents

Abstract

PURPOSE:To realize an electrolytical corrosion-proof transformer tank with simple installation by burying said tank in an underground hole made of reinforced concrete and disposing a sacrificial anode via an insulated wire in said hole. CONSTITUTION:In a galvanic anode method, a transformer tank 2a is buried in an underground hole 1 made of reinforced concrete and is connected to a grounding bar 7, reinforcing bars 6 and a sheathed earth 12 via insulated cables 12. A sacrificial anode 11 is installed via the cable 12 in the hole 1. When the tank 2 is submerged in the water in the hole 1 and corrosion is to initiate, the sacrificial electrode 11 submerges in the water 16 as well and provides an electrolytic protection effect. Thus, the transformer is protected electrolytically with the simple installation.

Description

[Detailed description of the invention] This BA relates to a method for cathodic protection of underground transformers.

In order to beautify the city, as well as due to the increasing demand for electricity in the city center and the difficulty in securing land, underground power distribution has become widespread, and transformers are often buried underground. This underground transformer is buried in the roadway or sidewalk.
? The installation method is shown in Figure 1.

In Figure 1, 1 is an underground hole made of reinforced concrete, 2
IIi is an underground transformer installed in this underground hole l. Underground transformer 2#'i is connected to the power supply side by a sheathed high voltage insulated cable 3 and to the load side by a low voltage insulated cable 4. One end of each of the sheath of the high voltage insulated cable 3 and the neutral wire insulated cable of the low voltage insulated cable 4 is connected to the transformer tank 2a.
The other 191illFi are grounded on the power supply side and load side, respectively. The underground transformer λ is electrically connected to the reinforcing bar 6 buried inside the concrete of the underground hole 1 by means of a fixing device 6 such as No. 1g/(c) at the top of the tank. It is connected and fixed. The grounding rod is made of steel, and the insulated cable 8 connects the transformer Tajik 2t.
sK@continued. 9ij grating lid.

It covers the top of underground animal 1.

Since the upper surface of the underground hole 1 is covered with the grating 9 in this way, rainwater and sewage can flow in, and groundwater can also flood from the drainage holes 10 and joints of the underground hole 1.
Water collects inside.

If the transformer tank 2a is exposed to water, it will cause chemical corrosion. When the inventor investigated existing underground transformers, most of them were submerged in water, with varying degrees of damage depending on the installation location and season.

Therefore, cathodic protection method can be considered as a corrosion prevention measure for transformer tanks. Cathodic protection methods include the following methods, depending on the method of flowing a protective current into the buried object to be protected, such as a transformer tank.

(1) External power supply method: A method in which AC power is converted to DC using a rectifier and anti-corrosion current is passed.

(2) Galvanic anode method: A method that uses the potential difference between different metals to flow an anti-corrosion current.

In the conventional galvanic anode method, as shown in Figure 1, the sacrificial anode 1 is buried underground outside the underground hole 1 with a height of 11' ft.
1 and the transformer tank 21L with the insulated cable 12, construction is time consuming and particularly difficult in the case of an existing underground transformer. In addition, in the conventional external power supply method, as shown in Fig. 1 6), an electrode 15 (magnetic iron, silicon cast iron, graphite, etc.) connected to the positive side of the DC generator 14 is connected to the ground outside the underground hole 1. Since it is buried inside, construction is time-consuming in this case.

Therefore, the first object of the present invention is to provide a method for cathodic protection of an underground transformer that is easy to install, and which is easy to install and can extend the life of the sacrificial anode 11 and electrode 15. Providing cathodic protection method￥ttlE2
The purpose of The present invention will be described below with reference to each embodiment shown in the drawings. In the drawings, the same members as in FIG. 1 are given the same reference numerals to avoid redundant explanation.

Figure 8 shows a conventional example without cathodic protection f11/a,
Figures 5 and 4 show examples of the present invention when applied to the galvanic anode system, and Fig. 5.4. It is installed inside. As mentioned above, in an underground transformer, the transformer tank 2a is submerged in water inside the underground hole 1, and in the submerged state where corrosion begins, the sacrificial anode 11 is also submerged in water 16.
It exerts the same cathodic protection effect as conventional buried underground. In this way, cathodic protection can be achieved simply by installing the sacrificial anode 11 inside the underground hole 1, and construction is simple. Moreover, when no water remains in the underground hole l, no anticorrosion current flows out from the sacrificial anode 11, and no rust occurs and the sacrificial anode 11 is not wasted. 5.4 The symbol 1s in Figure 4 is the sheath earth of the high voltage insulated cable.

On the other hand, in the example shown in FIG.
In the example shown in the figure, both are electrically insulated. If the transformer tank is insulated from the mal reinforcing bar 6 as shown in Figure 4,
The wear and tear of the sacrificial anode 11 during storage is reduced and its lifespan is extended. The reason is explained below.

Table 1 lists materials commonly used.

Rebar 6. Ground rod, transformer tank 2a and sacrificial anode 11
The results of measuring each natural potential are shown. In this measurement, "" is based on the saturated electrode, and the measurement was carried out using the measuring circuit shown in FIG. In FIG. 6, l'/#i saturated sweet cord electrode 8. C1).

18Fi voltmeter, 19it changeover switch.

Table 1 As can be seen from Table 1, the reinforcing bar 6 is the most responsible, followed by the grounding rod, transformer tank 2a, and sacrificial anode 11 in that order.

Electrochemical corrosion is a process in which a current flows from a high potential to a low potential, and the transformer tank 2a is connected to the reinforcing bar 6.

A large current flows from the reinforcing bar 6 to the sacrificial anode 11.

The sacrifice 1s1ii11 will be exhausted quickly. Therefore.

If the transformer tank 2a is insulated from the reinforcing bars 6 as shown in FIG.
has a longer lifespan. In Table 2.

In the examples shown in Figures 3 and 4, and the conventional example shown in Figure 2, which is not provided with cathodic protection. The measurement results of corrosion current and anticorrosion current of each member are shown. In Table 8, + indicates the corrosion current, - indicates the anti-corrosion current, and in Figure 1-4, the white arrow (1) indicates the corrosion current, and the black arrow (→) indicates the anti-corrosion current. shows.

As shown in Table 2, as in the example in Figure 3, the sacrificial anode 1
1 in the underground hole 1 can easily provide a corrosion protection effect when the underground transformer is flooded, but if the transformer tank 2a is electrically insulated from the reinforcing steel 6 as in the example shown in FIG.
Figure 3 is fake and ij! The current of the sacrificial anode 11, which was 5 eb Oym, is significantly reduced to 3 a3 mm, and the life span is increased by 7 n. Also, since there is no current from reinforcing bar 6.

In the example of Fig. 3, the transformer tank 2a is also used in the example of the 4th WJ.
The anti-corrosion current is increased and the anti-corrosion effect is improved.

An example of fixing a transformer tank while electrically insulating it from reinforcing bars in an underground hole is shown in Figure 6, which is a conventional fixing system.
As shown, the metal fitting aa fixed to the reinforcing bar 6 and the metal fitting 5b fixed to the transformer 2 are directly tightened with bolts 5c. Therefore, in the fixing device 20 of FIG. An insulating sleeve 5d with a flange and an insulating plate 6 with a hole.
I bought a 5eK and tightened both metal fittings 5a and 5b. The insulating material for 5d+56 must be one that has good water resistance, high insulation resistance, and high mechanical strength; for example, it is made of vinyl chloride.

The above explanation is for the case where the present invention is applied to the tube current anode system, but it goes without saying that it can also be applied to an external power supply system. One embodiment of this case is shown in FIG. The reference numeral goFi in FIG. 6 indicates a fixing device having a good electrical insulation structure.

In addition, considering the power distribution system, the sheath of the high voltage insulated cable 3 of the underground transformer is connected to the low voltage insulated case and grounded. Therefore, the present invention does not have to be applied to all underground transformers.

For example, since underground transformers are generally installed at intervals of 2 to 5 power poles, if it is applied to one of the 2 to S units, the adjacent transformer tank will also receive the corrosion protection effect, and the construction cost will be reduced. will be significantly reduced. An experiment was conducted regarding this effect, and the measurement results are shown in Table 3, and the contents will be explained using FIG. 8. In Fig. 8, both the φ1 and φ8 underground transformers are installed with their transformer tanks 2a insulated from the reinforcing bars 6, and the underground hole 1 on the side of the φ2 underground transformer is installed.
A sacrificial anode 11 is provided only inside. Furthermore, the conditions for connecting the transformer tank laa, the reinforcing steel 6 and the sacrificial anode 11 can be changed using switches 81 to 81 as necessary.

The contents of the experiment shown in Table 3 will be explained below with reference to FIG.

Experiment Al This experiment is for a conventional installation without cathodic protection pipe sections, with switch 81'101PF and switch S! and B@
f ON, underground transformers 1 and +2 were under the same conditions. As a result, a large corrosion current flowed through both transformer tanks 2aK in #i.

Experiment A2 This experiment was to verify the effect of the sacrificial anode 11, and each switch was set to 81mBz*8s': ON (!: The underground transformer in S1 was left as Experiment JI61, +2
The underground transformer was given the same cathodic protection as shown in Figure 3. This result shows that although most of the current flows from the sacrificial anode 11 to the reinforcing bars in each underground hole l, the corrosion current in the tank of the underground transformer +1 is significantly reduced, and the corrosion current in the tank of the underground transformer +2 is significantly reduced.
! aKt: Anti-corrosion - Negative current flows and anti-corrosion action is working.

Experiment 3 This experiment was to verify the corrosion protection effect when insulating the φl underground transformer and the reinforcing steel 6.
and 88 are ON, switch 8.1 is OFF, and the +2 underground transformer is the same as in Figure 3. This result #i, sl
The corrosion current in underground transformer tanks was further reduced.

The experiment with Muro is ◆2 underground transformer, reinforcing steel 6 and tIm! !
This is to verify the anti-corrosion effect in the case of edge 9, with switches 6I and B, f OM & switch 8.1i-OFF, and ttK, +2 of the conventional installation example of φl underground transformer company.
The underground transformer was subjected to the same cathodic protection t-m as shown in Figure 4.

This result Fi.

As in Experiment 4g, the corrosion current in the tank of underground transformer +1 decreases, and the tank gaK of underground transformer 2 decreases.
In addition to the anti-corrosion current flowing, the current from the sacrificial anode 11 is also flowing.

Experiment A In the experiment A, both underground transformers +1 and +2 were insulated from the reinforcing steel 6, and the effect of the sacrificial anode 11 was investigated.

This book verifies the corrosion protection effect of the underground transformer (S2) in the underground hole 1 containing the sacrificial anode 11 and the underground transformer S1 (S1) in the adjacent underground hole L without the sacrificial anode. , switch s, f ON, switch 8 snow and 8.
1-OFF, and the underground transformer No. 2 is the same as in Fig. 4.

This knot J! In addition, the corrosion current in the tank of the 4'L underground transformer is significantly reduced, and the corrosion protection current in the tank 2 of the 2 underground transformer increases, increasing the corrosion protection effect.
Moreover, the current of the sacrificial anode 11 was significantly reduced. The arrows in the Snow diagram indicate the flow directions of the corrosion current and anti-corrosion current in Experiment A5, respectively.

As explained above, in the past, the sacrificial anode 1 used for galvanic current *pole 2 and the electrode 15 used for external power supply method were buried underground outside the underground hole 1, which was troublesome to install. According to the present invention, the sacrificial anode 11 and the electrode 15Yt are simply connected to the underground hole 1.
Since it is only necessary to install the sacrificial anode 11 and the electrode 115 inside the ground, it is easy to install the sacrificial anode 11 and the electrode 115 in the existing underground transformer.

(9) If the sacrificial anode 11 and the electrode 15 are electrically insulated from the transformer tank aaYr reinforcing steel 6 and installed in the underground hole 1, the life of the sacrificial anode 11 and the electrode 15 can be easily extended significantly.

[Brief explanation of the drawing]

Figure 1 (al, 6)L (0) relates to the prior art, 6
) is a vertical sectional view of an underground transformer with cathodic protection using galvanic anode method, (bl#i vertical sectional view of an underground transformer with cathodic protection using external power source 2, (aIkikl,
FIG. 3 is a cross-sectional view of the fixing device for the transformer tank in (1+), taken along arrows. FIG. 2 is a circuit diagram showing an underground transformer without cathodic protection, and FIGS. S and 4 are circuit diagrams showing embodiments of the present invention, respectively. Fig. 5 is a circuit diagram for measuring the natural potential, Fig. 6 is a sectional view showing an example of a fixing method, Fig. 1 is a vertical sectional view of another dormitory according to the present invention, and Fig. 8 is a longitudinal sectional view of another dormitory according to the present invention. FIG. 2 is a circuit diagram for investigating the corrosion protection effect on an underground transformer in contact with II by application. In the drawing, 1ij is underground hole, 2a is transformer tank, 3 is high voltage insulated cable with sheath, 4 is low voltage insulated cable, 6tj is reinforcing steel. F: Ground rod, A: XGFi insulated cable, 9#-1 grating. 11Fi sacrificial anode. 13#i sheath earth. 14 is a DC generator. 15 is an electrode. 16Fi water. 17 is a saturated electrode. 18ij voltage needle, 19 is a changeover switch. 20 is a fixed device, and 81 * fh e ss is a switch. Figure 1 (0) Figure 1 (C) Figure 2 Figure 5 q lt Do l Figure 6 Figure 8

Claims (2)

[Claims] (1) When performing cathodic protection on tank pipes of transformers installed at KJI in reinforced concrete underground holes, insulate the electrodes that flow into the tank, such as sacrificial anodes in galvanic anode systems and electrodes used in external power supply systems. A method for cathodic protection of an underground transformer, characterized by placing it in an underground hole via a cable pipe. (2) When cathodic protection is applied to the tank of a transformer installed in a reinforced concrete underground hole, an insulated cable is used to connect the electrode that allows anti-corrosion current to flow into the tank, such as the sacrificial single pole in a galvanic anode method or the electrode in an external power supply method. This is a method for electrolytic corrosion protection of round underground smart voltage transformers, which is characterized by placing the transformer in the underground hole through the tube and electrically insulating the transformer tank from the reinforcing steel in the underground hole.