JPS58211671A - Inspecting device for internal trouble of winding of transformer - Google Patents

Abstract

PURPOSE:To enable the early detection of a short-circuit trouble occurring inside a coil, by arranging a current transformer on the neutral point side of each of windings connected in parallel, and detecting and comparing simultaneously a current flowing through each winding. CONSTITUTION:The figure shows that a plurality of current transformers are arranged in a constitution of windings of a UHV transformer having high-voltage windings 3a- 3f and medium-voltage windings 4a-4f, and the current transformers 20a-20f are arranged at the positions of lead wires on the neutral point sides of the medium-voltage windings 4a-4f, respectively. The output signal leads of the current transformers 20a- 20f, which are not shown in the figure, are connected to control devices in a transformer control chamber, which are arranged separately from a group of transformers, and a circuit is constituted so that the outputs from the current transformers are compared with each other and that, when the values thereof are different from each other, a trip signal of the transformer is delivered as occasion calls. Such a constitution enables the quick detection of a short-circuit trouble between winding turns, etc., and the immediate specification of a unit transformer wherein the trouble occurs.

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention relates to a transformer having many windings connected in parallel, such as a UHV transformer. Regarding an internal accident detection device.

<Technical Background of the Invention> Due to the increase in power demand, UHV kite transmission is currently being planned and development of various UHV power transmission equipment is underway. Among these UHV power transmission equipment, transformers are one of the most important. However, compared to conventional transformers, the voltage and customer base are significantly higher than that of conventional transformers, which poses various problems.
Maximum operating voltage 1100I (capacity 200 per V11 bank)
0MvA to 3000MVA 6 Therefore, due to restrictions on the transportation of JNR freight cars, transformers are manufactured by dividing each unit into 2 to 4 parts, and are used on site by connecting them in parallel through lead ducts. will be done.

Although the KtJHV transformer has a very complicated structure, due to its large capacity, its reliability is required to be simpler than before. In addition, in the unlikely event that an accident occurs, we can quickly detect the problem and minimize the accident.
Measures to prevent accidents from spreading to other equipment must be considered.

FIG. 1 shows the winding configuration of one equivalent of a conventional 500 KV transformer. The transformer body 1 includes a high voltage winding 3,
The medium-voltage winding 4 and the low-voltage winding 5 are wired to form a single-phase winding transformer, and the separate load voltage regulator tank 2 has an excitation winding connected to the low-voltage winding 5 of the transformer body. 6 and a voltage adjustment winding M7 are housed therein, and the voltage adjustment winding 7 is connected to the transformer body 1 and the on-load tag switch 1O. In addition, the high voltage line end 8 and the medium voltage line end 9 of the transformer body l
VC is a current transformer 11 for measuring the current flowing through each winding.
．． 12 are arranged.

<Problems with the backbone technology> In Figure 1, the role of the current transformers 11 and 12 placed at the ends 8 and 9 of Takasho and Nakasho narrow roads is not only to measure DC during normal operation, but also to measure In the event of an internal accident in a voltage transformer, such as when dielectric breakdown occurs from the winding to the tank, causing a ground fault, or when a short circuit occurs between the winding turns inside the winding, abnormal DC is detected. (It also plays the role of issuing the No. We will quantitatively examine and explain the accidental current that occurs in the following.A short-circuit accident between winding turns is a short-circuit accident in which one turn of the winding wire is short-circuited due to dielectric breakdown. This means that an abnormal current flows through that turn.In order to quantitatively examine this abnormal current, it is necessary to Find the impedance between the main winding (specified winding), connect the main winding source, shorten the 7-minute winding, and calculate the current flowing through some windings. Table 1 below shows that for an example of a 500KV transformer as shown in Figure 1, one terminal short circuit occurs in any one of the high voltage winding, medium voltage winding, and low voltage winding. The impedance between each winding is calculated by considering the winding.In addition, in the case that an inter-turn short circuit accident occurs during operation, it is calculated whether the high voltage side, medium voltage side or dark source is connected in response to each accident. In this case, the current change due to high voltage/medium voltage line current is p, u
, (bar unit) and are also shown. The impedance is the rated capacity for one leg of the coil @ total Heath V (1).

Table 1 below shows the calculated value of the change in circulation when one terminal is shorted, and the method of calculating the value will be explained using an example.

Let us now consider the v current change that occurs in the high voltage winding when a one-turn short circuit occurs in the high voltage winding and the power supply is connected to the high voltage side.

Table 1 shows the impedance between the high voltage winding and the single-turn shorted winding.
As shown in , it is 220 inches. The meaning of 220- is that when the load winding of the high-voltage winding is only a one-turn shorted winding, when the rated current is poured from the high-voltage winding side, the voltage of the high-voltage winding is 220- of the rated voltage. This means that Therefore, if a one-turn short circuit occurs in the high voltage winding while the surface pressure winding is operating at the rated voltage and rated current, a current of 100/22g = 0.451)-11 will flow through the shorted winding relative to the rated current. It will increase to supply energy to the line.

In this way, in the autotransformer shown in Figure 1, regardless of whether an l-turn short circuit occurs in the high-voltage or medium-voltage winding, and regardless of whether the power supply side is on the high-voltage or medium-voltage side, A short circuit fault could be detected as a direct current change of 38% to 59% of the line current (as shown in Table 1) using a current transformer attached to the line end. In addition, current changes also occur when the device is operated at a voltage of 11ti, but this change is within ±10% at most, so it could be distinguished from the case of an inter-turn short circuit accident.

However, in the case of a UHv transformer, a short-circuit accident between turns cannot be detected with a current transformer arranged as shown in FIG. This is because, as explained earlier, a υIIV transformer has many windings connected in parallel, and even if a one-turn short circuit occurs in one winding, the current change will have no effect on the line current. This is because it is so small that it cannot be distinguished from the DC change caused by the operation of the F$4 rectifier during load.

Figure 2 shows the winding configuration of an assumed U HV transformer,
It is something that A 1-phase autotransformer has two transformer bodies IA and 113 connected in parallel, and each transformer body IA and 113 are connected in parallel.
A, IB include high voltage windings 3a, 3b, :3c,
3d, 3e, 3f.

Medium voltage windings 4a, 4b, 4c, 4d, 4e, 4
Three legs of f are housed and connected in parallel, and are connected to an autotransformer. There are also two load pressure regulating regulators 2A and 2B, each of which houses Narita A11 regulating windings #7A and 7B; Six winding legs are connected in parallel. In FIG. 2, the low voltage winding and excitation winding are omitted. Even in such a case, the relationship is exactly the same as the change in the winding current u1 outside the coil 1 leg in the event of a short-circuit accident within the winding. (t
The impedance between windings in the case of a JHV transformer can be considered to be the same as in Table 1. ) However, when considering the total current of the six-legged winding, the circulation current is ~59%, 6. a-~9.
8%) Voltage under load IiI! , the current change due to the operation of the regulator ±lO becomes indistinguishable from a deer and cannot be detected as an accident.

The same applies to conventional 500 KV transformers when the number of parallel coil legs is large.

<Purpose of the Invention> The present invention has been made to eliminate the drawbacks of the above-mentioned prior art, and when a large number of coil legs are connected in parallel, such as in a UHV transformer, accidents such as cicadas between turns of strands may occur. The purpose of the present invention is to obtain a highly reliable transformer winding internal fault detection device that can accurately and early detect faults inside a transformer winding.

<Summary of the invention> In order to achieve the above object, the present invention-1-j: U HV
In a transformer winding configuration in which multiple coil legs are connected in parallel and connected as an autotransformer like a transformer, a current transformer is placed on the neutral point side of each winding connected in parallel, and each winding is connected in parallel. By simultaneously detecting and comparing the current flowing through the wire, short-circuit accidents occurring inside the coil can be detected at an early stage.

<Embodiment of the Invention> An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a circuit configuration diagram according to the present invention in which a plurality of current transformers are arranged in the UHV transformer winding configuration shown in FIG. 2 above.

In FIG. 3, current transformers 20'a, 20b, 20c
, 20d, 20e.

20f are medium voltage windings 4a, 4b, 4c, 4d, 4, respectively.
It is placed at the neutral point side exit lead position of e and 4f. Although omitted in the figure, current transformers 20a, 20b, 20c,
The output signal leads of 20d, 20e, and 20f are connected to a control device in the transformer control unit located separately from the transformer group, and the outputs from each current transformer are always compared, and if the values differ, the necessary The circuit is configured to issue a trip signal for the transformer LE in response to the change.

<Other Embodiments of the Invention> FIG. 4 is a circuit configuration diagram showing another embodiment according to the present invention. Fig. 4 ij is exactly the same as Fig. 3 except for the position where the current transformer is arranged.

In Fig. 4, there are three medium voltage windings 4 in each unit transformer body IA, IB of current transformers 21A, 21B &'12.
a.

4b, 4c, 4d, 4e, and 4f are arranged on the neutral point side of the output leads after they are connected in parallel. The output signal leads of current transformers 21A and 21B are the same as in the previous embodiment.

<Effects of the Invention> In the transformer winding internal fault detection device according to the embodiment of the present invention configured as described above, the following various effects can be obtained.

(1) Since the passing current of windings connected in parallel can always be observed in comparison, it is possible to prevent internal winding accidents, short circuits between winding turns, etc. in any one winding or in one unit transformer.
If an imbalance occurs in the current, the accident can be quickly detected and dealt with.

(2) When the on-load voltage regulator is operated, the current change V+ of the windings connected in parallel is detected equally by each winding, so it is clear that This can be distinguished from the phenomenon occurring when an accident occurs inside the wire, and the occurrence of an accident inside the winding can be determined with high accuracy. Also,
This operating principle is independent of the number of windings connected in parallel.

(3) When an accident inside a winding is detected, the winding or unit transformer that caused the accident can be immediately determined.

Therefore, it does not take much time to recover from an accident, such as when a spare transformer that has been disconnected is installed in a substation.

(4) Since the current transformer for detecting internal winding faults is placed on the neutral point side exit lead of the medium voltage winding, the lead voltage is relatively low, making it difficult to install the current transformer. Even in the insulating configuration, the insulating reliability is not particularly reduced.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing the winding configuration of a conventional single-turn single-phase transformer, Fig. 2 is a wiring diagram showing the winding configuration of an assumed UHV transformer, and Fig. 3 is a wiring diagram showing the winding configuration of an assumed UHV transformer. FIG. 4 is a connection diagram showing a winding internal accident detection device, and FIG. 4 is a connection diagram showing another embodiment of the present invention. IA, IB...Unit transformer body 2A, 2B...Direct voltage at load, 11 regulators 3.3a, 3b, 3c, 3d, 3e, 3f...High voltage winding 4.4a, 4b, 4c, 4d, 4e, 4f...Medium voltage winding 5...Low voltage winding 6...Excitation winding 7, 7A, 7B...1 voltage I! L1 regular winding 8...
- High voltage line end 9... Medium voltage line end 10... On-load tap changer 11.12.20a, 20b, 20c, 20d, 20e
, 2Of , 21A, 21B ---Current transformer Fig. 1//

Claims (2)

[Claims] (1) Multiple legs of transformer windings are housed within one or more transformer tanks, each with an electrical V? :,
When connected in parallel to form a single-winding, single-phase transformer, a current transformer is placed on the neutral point side lead of each medium-voltage winding connected in parallel, and the current flowing through the leads is measured. A transformer winding internal fault detection device is characterized in that it detects a transformer winding internal fault from the current balance of the medium voltage winding. Tei (2) In the product described in claim 1, the current transformer is arranged at the neutral point side medium voltage winding lead after being connected in parallel for each transformer tank. Transformer winding internal fault detection device.