JPS6066620A - Transformer protection relay method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a transformer protective relay device, and particularly to a transformer protective relay system that can detect internal failures such as partial short circuits in windings with high sensitivity. Regarding.

[Background of the invention]

As a method of protecting transformers, there are many methods of detecting a vector composite current, the so-called differential current, which is obtained by converting all the currents at each terminal of the transformer into vectors, and using this as the operating force for the transformer protection operation. . Additionally, due to errors in the current transformer (hereinafter abbreviated as CT), which is the current detection means, a composite current may be generated due to the current passing through the transformer even when the transformer is in good condition. To achieve this, so-called passing current suppression is used, in which the transformer terminal currents are transformed in the same order and the scalar composite current is used as a restraining force for the transformer protection operation. Furthermore, since the above-mentioned vector composite current is also generated by the excitation inrush current that occurs when a transformer is energized, one way to prevent erroneous protection operations due to this is, for example, to prevent the excitation inrush current of the transformer from having a large number of second harmonic components. There is a so-called second harmonic suppression method that utilizes the second harmonic component in the vector composite current as a suppressing force for the transformer protection operation.

Transformer protection relay devices can be used as relay elements to suppress these various operating forces, and multiple operating forces.

The case where the suppressing force etc. is configured as one relay element is also discussed.

The present invention relates to the entire transformer protection relay device, including the overcurrent element that obtains the operating force from the vector composite current and the passing current element that obtains the suppressing force from the scalar composite current, and both of them are included. The present invention may also be applied to the case where i = one relay element, the case where one relay element is formed by combining with other operating force or restraint force, etc., but in order to clarify the gist of the invention, In the following explanation, each will be treated as an independent relay element.

First, the principle of an overcurrent element caused by a vector composite current of current flowing through each terminal of a conventional transformer and its problems will be explained using the route diagram shown in FIG.

In Figure 1, 1 is the 2@ line transformer to be protected, and 21 and 22 are the primary and secondary terminal currents of the transformer, '1 +
'1st and 2nd CT to detect 2, 3 is 1st and 2nd C
A conversion circuit that equivalently converts the T output current, 4 is a first relay element, 51 and 52 are equivalently converted currents I! ,
It indicates the input terminal of the first relay element that is manually operated. The conversion circuit 3 is composed of an OCT etc. to equivalently convert '1 p '2, but if the current ratio of the primary and secondary CTs 21 and 22 is appropriate and the output currents of the CTs are already equivalent,
The conversion circuit 3 may be simply a lead wire for connecting the primary and secondary CTs to the input terminals 51, 52t of the first relay element.

Although not shown, the input terminals 51 and 52 of the first relay element normally have a plurality of setting tags with different rated currents, and the input terminals 51 and 52 when the transformer 1 is operated at the rated current. An appropriate tag is selected depending on the magnitude of the currents It and Iz. Since this setting tap is also used to equivalently convert each input current input to the input terminal, the conversion circuit 3 is not necessarily required.

As shown in FIG. 1, the first relay element 4 has an input terminal 51.
．． The currents I+ and I2 input to the circuit 52 are vector-combined, and when the vector-combined value vA exceeds the operating level L, as shown in equation (1), a protective operation is performed.

VA=l It +I 1≧L (1) When the transformer 1 is healthy, VA is approximately zero, so no mining operation is performed. VA occurs when an internal failure occurs, but
If it is lower than the operation level L, no protection operation is performed. The operating level is generally determined by the electromagnetic operating tidy of the relay contacts, and is usually about 30% of the rated current at each tap position of the above-mentioned setting tag.

That is, relatively light failures in which only a vector composite current of 30% or less of the transformer rated current occurs are difficult to detect with conventional transformer protection switching devices.

Next, the principle and problems of a conventional transformer-made relay device that uses a biased current suppressor will be explained with reference to the route diagram in FIG. 2.

In FIG. 2, the same parts as in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The difference in FIG. 2 from FIG. 1 is that a second relay element 6 is provided, and two currents Ir and I are equivalently converted by the conversion circuit 3. The second relay element 6 receives currents IN and I input to each input terminal 71 and 72.
Scalar composition of z is performed and a scalar composite value 8A shown by equation (2) is output.

S^= l It l + l Lz l − (2) S
^ is the restraining force of the transformer protection operation, but it is combined with the vector composite value V^, which is the output of the first relay element 4, that is, the operating force, and satisfies the condition of equation (3). When a protective operation is performed.

Pmu = V * Kh8^≧L ... (3) KA is called the suppression coefficient, and it prevents erroneous protection operation due to the vector composite value ■mu caused by errors in CT etc. due to excessive passing current at the time of external failure etc. It is set to not be performed. That is, when the transformer 1 is in good condition, PA = VA KA SA ≦ 0 (4). , (It td EV is 10%) ~ L in equation (3) is the same operating level as explained in the conventional example in FIG. There is a problem that even if the total operating force Pm occurs, if the operating level L is not reached, the protective operation cannot be performed.

One of the problems with the transformer protection relay system is that it can quickly detect major failures that cause tank destruction in a short period of time due to large arc energy, and complete the protective operation before the tank is destroyed. One challenge is to detect the sensitivity of the cylinder and perform protection operations without fail, even though the arc energy is small and it takes time to avoid relatively minor failures that could lead to tank destruction.

In the latter case, the change in the transformer terminal current is small, and the vector composite current value described above is also small. However, as mentioned above, conventional voltage transformer protection devices do not perform protective operations against minor failures in which the operating force is less than a certain percentage of the rated current of the setting tap, which corresponds to the rated current of the transformer. The basic problem is that it cannot be done.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transformer protection relay system that can improve the above-mentioned drawbacks of the prior art and can detect even minor failures with high sensitivity.

[Summary of the invention]

The present invention combines a plurality of terminal currents of the same phase of the transformer to be created to obtain (L+ 10a (It 10Lx)), inputs this to the first input terminal of the first relay element, Apply 12 to the other terminal. In this case, we focused on the fact that the input terminal current of the first terminal during steady state is the same as in the conventional technology by 4, but the vector composite current in the event of an internal failure is 1X larger than that in the conventional technology, and we detect internal failures with high sensitivity. It has been made possible.

[Example of former IJIJ]

The principle of the present invention will be explained with reference to FIG. FIG. 3 is a route map that does not show the preferred embodiment of the present invention, and the same parts as in FIGS. 1 and 2 are designated by the same reference numerals and their explanations will be omitted.

What is different in Fig. 3 from Fig. 2 is that in the conversion circuit 3, the current It r Iz obtained by equivalently converting the primary and secondary terminal currents 'I+'2 of the transformer is vector-synthesized, and the current resulting from this vector synthesis is further The configuration is such that the final combined current (It+a(L+Id)) obtained by vector combining a(II+I2) with It is input to the input terminal 52 of the first relay element 4. 11 is input to the other input terminal 51 of the electric element 4. Similarly to the prior art described in FIG. Enter I2ft and enter -C.

Assuming that the first relay element 4 and the second par element 6 themselves are the same as those explained in the prior art in FIG. are equations (6) and (7), respectively.

Vo=lIs+(I虞+a(It+Iz)H−(6)S
D = I It l l h I (7) Note that a is a positive number and can be set to any value.

A protective operation is performed when the condition of equation (8) is satisfied using VD and SD.

Pa = Vo KoSD: 2L - (8) KD is the suppression coefficient, and L is the operating level.Next, in order to explain the value of the suppression coefficient KD, consider the case of an external failure. In order to prevent a false protection operation due to a passing current at the time of an external failure due to an error in CT, etc., it is sufficient if PD≦0 (9) at the time of an external failure. That is, KD may be set so that the following is true for the external failure that causes the maximum error. Specifically, it becomes,
KD may be set to (1+a) times the suppression coefficient of the prior art described in equation (3).

Next, in order to explain the value of the operating level L, consider a healthy state in which the transformer 1 is operating at its rated value. 1st shi, synthesis'ri
m (: h + a (Il + l2)) is manually input, but of this combined current, (1 + + It l is approximately zero. Even considering the slight error caused by CT etc., the value of a positive real number a Unless it is set to an extremely large value, l Is l > a I Is + It l - (12
). That is, the composite current (I + a (It + It))
The value of is almost equal to Is. Therefore, the setting tag of the relay element 40 input terminal 52 may be in the same tag position as when inputting I2 in the prior art. Therefore, the rated current at the settling tag position corresponding to the rated current of the transformer 1 is the same as in the prior art.

Therefore, as described in the description of the prior art, the operating level L is determined by a constant ratio of the rated current at the settling tag position, so it may be the same value as in the prior art.

Next, the present invention will be explained in detail in the event of an internal failure. (8
) in the equation is the suppression coefficient Kn of the conventional technology (
Consider a case where the operation level L is set to the same value as in the prior art.

The vector composite value VD at the time of internal failure is Vo ”l Zt+(Iz+a(It+Iz))l=(
1+allIt+Izl=(1+alYmu...(13)) The scalar composite value 8o is 8o=IItl+IIyuki1=Smu...(14) Therefore, the total operating force PD is as shown in equation (15), as described above. (1+a) of the total operating force P in the conventional technology
) will be doubled.

1'o =V o -Kn 8D = (i+a)Va (1+alKASA=(1+a)P
(15) Since the operation level L is the same as in the conventional technology, the detection sensitivity for internal t1 failures improves to the extent that the total operating force FD at the time of internal failure is greater than P in the conventional technology. .

For example, when the operating level L is 30% of the rated current, the conventional technology cannot detect an internal failure in which the total operating force P^ is less than 30% of the rated current. In the present invention, it is clear from the above description that when the positive real number 3 is set to 1, the total operating force PDill:P is twice as large as 15%≦PA (30%), which could not be detected with the conventional technology. internal failures can be detected.

When set to a positive real number a f 2, it is possible to detect 10%≦P (30%) of internal failures that could not be detected using the prior art. As described above, a major feature of the present invention is that relatively minor failures, which are one of the challenges faced by a transformer protective relay device, can be detected with high sensitivity and protective operations can be performed.

Another embodiment of the invention is illustrated in FIG. What is different in FIG. 4 from FIG. 3 is that in the conversion circuit 3, the primary and secondary terminal currents of the transformer are vector-combined at different conversion ratios.
This composite current (aIl+(1+a)Is) is configured to be input to the input terminal 52 of the first coupling element 40. The other input terminal 51 of the first relay element 4
, I1 is input as in the embodiment of the present invention shown in FIG.

Flute A5? The composite current (aIs+(10a)Iz) input to the input hook 52 of A is the third wave.
It is equal to the resultant current (Iz+a(It+I*l)) inputted to the input terminal 52 of the first junction element 40 in the figure.

That is, the effects of the embodiment of the present invention shown in FIG.
The effect is similar to the effect in the embodiment of the present invention explained in FIG. 3, and the explanation will be omitted below.

Still another embodiment 1c of the present invention will be explained with reference to FIG.

In Fig. 5, the present invention was applied as a protective relay device for a transformer having a common winding portion. 11f in FIG. 5, the series winding of the transformer 1 to be protected having a common winding portion, 12
is a common winding, and 23 is a CT installed on the neutral point side of the common winding to detect the current (Is+i*) of the common winding. A transformer with a common winding part is equipped with a tertiary winding that is connected in a triangular manner, but this is omitted in Fig. 5 to simplify the explanation, and the following explanation also applies to the case where there is no tertiary winding. Do it as. What is different in FIG. 5 from FIGS. 3 and 4 is that a CT 23t- is installed on the neutral point side of the common winding 12 as a means for combining the primary and secondary terminal currents '1+F, and the output current of the CT is The current I2' obtained by equivalently converting the current I2' is inputted to the input terminal 52 of the first relay element 4. The equivalent conversion of each current in FIG. 5 will be explained below.

Volume 1:! i, (the sum of the number of turns of the series winding 11 and the common winding 120) is N1.The number of secondary turns (the number of turns of the common winding 12) is N2
, k as the current conversion ratio, I+=kft (16) is input to the input terminal 51 of the first relay element 40 and the input terminal 71 of the second U-plane element 6. Second relay element 60 input terminal 7
The current I2 input to the transformer 2 is equivalently converted from the transformer secondary terminal current 12 detected by the secondary CT 22 as follows. The input terminal 52 of the first relay element 4 has (
18) As shown in formula, the composite current (j++jz) detected by CT23 is = Iz+a(It +I!+ -
(18) Equation (18) clearly indicates that the current 1,1 manually applied to the input terminal 52 of the relay element 4 of 4↓1 is It is equal to the combined current input to the input terminal 52 of the first relay 4 in the example. The value of the positive real number a is limited by the primary and secondary turns ratio. As can be seen from the above, the embodiment of the present invention explained using the vJS diagram has the same effect as the embodiment of the present invention explained with FIGS. 3 and 4. Further, since C'1' 23 is installed on the neutral point side of the common winding, there are few insulation problems and it can be installed easily.

The embodiment of the present invention explained in FIG. 5 further has the following special mission. Even in the JMJ case where the transformer 1 is healthy and in steady operation, the error in CT21 and CT23 causes the syvector composition output VD, but this value is different from the embodiment of the present invention explained in FIGS. 3 and 4. , it is not (1+a) times that of the conventional technology. This is because the CT23 installed in the common winding part is used as a means to combine the primary and secondary currents of the transformer, and the vector synthesis caused by errors in the steady state in the present invention using CT21 and CT23. The value VD is
This is equivalent to the case of using CT21 and CT22, which are conventional techniques. Therefore, the suppression coefficient that determines the suppression force for avoiding erroneous protection operations in the event of an external failure may be the same as in the prior art. As a result, the total operating force in the event of an internal failure becomes even greater than the embodiment of the present invention explained in FIGS. 3 and 4,
The effect of increasing the sensitivity of failure detection can be further increased.

In addition, in the embodiment of the present invention shown in Fig. 5, failures that cannot be detected in principle, such as ground faults in the secondary terminal of a transformer, occur, so it is possible to prevent this from occurring in combination with the conventional technology. Of course.

The above IJ is intended for two-winding transformers! 1 has been explained, but the same idea can be applied to transformers with three or more windings.

Further, a composite current obtained by combining a plurality of terminal currents of the transformer to be protected may be manually applied to not only the first relay element but also the input terminal of the second relay element.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a transformer protection relay device that reliably detects internal failures in a transformer with high sensitivity.

[Brief explanation of drawings]

1 and 2 are route diagrams for explaining a conventional transformer protection relay device, and FIGS. 3 to 5 are route diagrams showing embodiments of the present invention. 1...Transformer, 21, 22.23...CT, 3...
- Conversion circuit, 4... first relay element, 51.52...
・First g''KtKt element terminal, 6...Second relay element, 71゜゜1 figure 72 figure ¥3 figure

Claims (1)

[Claims] 1. Equipped with a first relay that calculates the vector sum of one current at each end of the transformer and a vlJ2 relay that performs scalar synthesis of the low current at each end, and detects an internal fault in the transformer from the vector sum and scalar sin. In the transformer protection relay system, the first
One terminal current of the transformer is applied to the terminal of , and the composite current of the other terminal 'Its of the transformer and each terminal current multiplied by a factor is applied to the second terminal, W, 1 and 1. A transformer protective relay device characterized in that the vector sum of the applied current to the second terminal is determined.