JPS5930490Y2 - Electric charge measuring device for transformer insulating oil - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device for measuring the amount of charge accumulated in the insulating oil of a forced oil cooling type transformer.

In large, large-capacity transformers, transformer insulating oil (hereinafter referred to as transformer oil) is circulated at high speed through a cooler using an electric pump to cool the transformer windings.

On the other hand, since transformer oil itself is a very good insulator, it can generate triboelectricity when it comes into contact with the transformer windings and core as well as the inner surface of the cooler and passes through it at high speed.
This may cause charge to accumulate in the transformer oil, and this charge is placed in a state where it is difficult to dissipate.

That is, to explain in more detail, the transformer oil is 1013 to 1014.
It has a high volume resistivity of Qcm, and can generate a large amount of electric charge due to contact friction with transformer components.

Due to the high volume resistivity of the transformer oil, this charge is not dispersed but gradually accumulates in the oil and exists as a kind of space charge, or it is unevenly distributed on the surface of internal insulators and eventually A considerable amount of charge, ie, a voltage value, will be reached, and if this exceeds a limit value, internal discharge or dielectric breakdown will occur.

This phenomenon can no longer be ignored in equipment such as large-capacity transformers that use a large amount of transformer oil and are forced to flow for cooling purposes.

However, for reasons such as the fact that the flow charging phenomenon in oil-immersed transformers has not been clearly understood, no countermeasures have been taken to prevent charging of transformer oil.

Therefore, one end of the charge detection probe was immersed in the transformer oil.
It is conceivable to make the end of this probe and the transformer oil approximately equal potential, and to determine the amount of charge in the transformer oil by detecting the potential of this probe.

That is, in FIG. 1, 11 is a transformer tank which houses a transformer body 12 and transformer oil 13 inside.

The transformer oil 13 cools the windings 12a and the iron core 12b of the transformer body 12, rises, flows into the cooler 14 from the upper opening (not shown) of the transformer tank 11, is cooled, and returns to the inside of the transformer tank 11. The water flows through a circulation path that flows into the lower opening 11a.

The circulation of the transformer oil 13 is carried out by a cooler 14 and a pump 15 provided midway through the lower opening 11a of the transformer tank 11.
This will be done forcibly.

16... are piping that connect the cooler 14, the pump 15, and the transformer tank 11.

In such a transformer, transformer oil 1 flowing at high speed
3 comes into contact with the piping 16, internal insulators, etc., causing friction and charging, and when electric charge accumulates in the transformer oil 13, this amount of electric charge is transferred via the probe 17 installed in the piping 16. It is measured by

This section will be explained in more detail with reference to FIG.

The probe 17 is composed of a rod 17a whose detection end is made of a good conductor such as copper and a spherical electrode 17b attached to the tip thereof, and the spherical electrode 17b is disposed in the transformer oil 13.

The rod 17a of this probe 17 is insulated and supported by a lid 18 made of a high-resistance insulator commercially available as Teflon and passed through the opening of the pipe 16.

The insulating lid 18 is oil-tightly attached to the probe mounting flange 19 formed on the pipe 16 with bolts and nuts 20.

The external terminal 17C of the rod 17a of the probe 17 is connected via a blow bleed wire 21 to an aluminum conductive plate 22 which becomes one electrode forming a capacitor C, and the other electrode 23 of the probe 23 has an extremely large input impedance. It is connected to an electrometer 24.

In the charge amount measuring device configured in this manner, the probe 17 is insulated from the outside, so that the insulating oil and the probe 17 have approximately the same potential.

Therefore, the potential of the probe rod 17a is guided through the blow bleed wire 21 to the aluminum conductor plate 22, where it can be measured by the electrometer 24 through a certain capacitance C.

For example, if the electric charge in the insulating oil is
2 becomes (g) and the probe electrode 23 becomes (-), so the electrometer 24 displays the potential value of (g), and conversely, the electric charge becomes (g).
In the case of →, the potential value of (→ is displayed.

Then, by determining the charge density from this potential value, the amount of charge in the transformer oil can be measured.

This measurement is preferably performed in the shield box 25 or in a shield room to avoid the influence of the surroundings.

As mentioned above, in order to measure the amount of charge and polarity in transformer oil, it is sufficient to measure it with a probe, but if a shield box is used or the measuring device is calibrated at that time, it is difficult to maintain the transformer. This is extremely inconvenient.

The present invention takes the above-mentioned points into consideration, and aims to provide a device that can easily measure the amount of charge in transformer insulating oil without using a shield case or the like.

An embodiment of the present invention will be described below with reference to the drawings.

That is, as shown in FIG.
is connected to one electrode 26a of an electrode assembly 26 housed in a gas-tight container 27 via a blow bleed wire 21, and the other electrode 26b of the electrode assembly 26 is connected to a current detector 28.
Use equipment that is grounded through the

In this case, if the gap in the electrode assembly 25 is set so that dielectric breakdown occurs when the potential of the probe reaches a certain predetermined potential, dielectric breakdown will occur when the charge in the transformer oil reaches a certain value. A signal will appear on current detector 28.

Therefore, if this signal is used to automatically detect the amount of charge in oil, the amount of charge can be measured extremely easily, and maintenance work can be reduced since there is no need to use a shield box. can.

In the above embodiments, the charge measurement device is installed in the cooler piping system or inside the transformer, but it is also used in the transformer oil circulation system, such as before and after the cooler, before and after the pump, or at the top and bottom of the transformer tank. By installing charge measuring devices upstream and downstream of the system and making a relative comparison of the measured values, it is possible to measure the amount of charge generated in the cooler, pump, or transformer body.

[Brief explanation of drawings]

Figure 1 is a partially cutaway cross-sectional view showing an embodiment of a device for measuring the amount of charge in transformer insulating oil, Figure 2 is a partial view showing an enlarged main part of Figure 1, and Figure 3 is a partial view of the main part of Figure 1. FIG. 4 is a sectional view showing another embodiment of the invention, and FIG. 5 is a side view thereof. 17...Probe, 18...Insulator,
22.23... Electrode, 24... Electrometer, C... Capacitor, 26... Electrode assembly, 27... Gas sealed container. , 28...
Current detector.

Claims (1)

[Scope of utility model registration request] A high-resistance insulating lid that closes an opening provided in at least a portion of a transformer insulating oil circulation system, a probe having one end that passes through the lid and is placed in the oil, and a probe that is connected to an external terminal of the probe. an electrode assembly having a first electrode spaced apart from the second electrode; and a current detector connected between the second electrode of the electrode assembly and ground. Quantity measuring device.