JPS6321420B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relay device used for protecting a transformer.

A normal ratio differential relay (hereinafter referred to as _DfRY ) is used as a protective relay for transformers. This type of D _f RY is constructed as shown in FIG. In FIG. 1, 10 is a transformer, and current transformers 11a and 11 are connected to the input and output terminals of the transformer 10.
b is provided. The outputs of the current transformers 11a and 11b are input to a scalar sum detection section 12 and a vector sum detection section 13. The output of the scalar sum detection section 12 is applied to a minus input terminal of a first comparison section 16 via a ratio setting section 14 and a first rectification section 15 in sequence. The output of the vector sum detection section 13 is applied to the positive input terminal of the first comparison section 16 via the second rectification section 17 .
The first comparator 16 outputs the difference between both inputs, and supplies the output to a first level detector 18, which is a Schmitt trigger or the like. The output of the first level detection section 18 is supplied to the drive section 20a of the contact 19a.

The output of the vector sum detection section 13 is a fundamental wave component.
It is supplied to a first filter 21a that passes I _f1 and a second filter 21b that passes second harmonic component I _f2 . The output that has passed through the first filter 21a is applied to the plus input terminal of the second comparator 23 via the third rectifier 22. On the other hand, the second filter 2
The output that has passed through 1b is given to the suppression rate setting section 25 via the fourth rectifying section 24. The output of this setting section 25 is supplied to the minus input terminal of the second comparison section 23. The output of the second comparison section 23 is supplied to the drive section 20b of the contact 19b via the second level detection section 26. An output as a protective relay is obtained between the terminals 27a and 27b only when the AND condition of the contacts 19a and 19b is satisfied.

Next, to describe the operation of the conventional protective relay device described above, the scalar sum I _R (corresponding to the passing current) obtained from the output of the scalar sum detector 12 is taken as the suppression amount,
The vector sum (I _d ) (corresponding to the difference current) obtained from the output of the vector sum detection section 13 is defined as the operating amount. In FIG. 1, first and second level detection sections 1
8 and 26 operate immediately when the input value exceeds a predetermined level, and send the output to the drive units 20a and 20b.
supply to. As mentioned above, two level detectors 1
8 and 26, for example, even if the first level detection unit 18 sends out an operating output due to the excitation inrush current when the transformer is turned on and the contact 19a turns on, the second harmonic component I _f2 is used to suppress it. second level detection section 26
If the contact 19b is not operated, the contact 19b remains off. Therefore, terminal 27 is used as a relay device.
No malfunction output is sent between a and 27b. However, conventionally, the criteria for determining the second harmonic is
It is common to set I _f2 /I _f1 = about 0.15, and it was normal for I _f2 /I _f1 of the transformer excitation inrush current to be 0.15 or more, so even in the above case, it is possible to prevent malfunction output. I didn't send it out.

However, recently, due to improvements in transformer core materials and structural changes, the second harmonic component (I _f2 ) and fundamental wave component (I _f1 ) in the excitation inrush current when the transformer is turned on have been improved.
The ratio I _f2 /I _f1 tends to become smaller. For this reason,
Some transformers have come out in which the ratio is close to 0.1 in the first wave of power supply. With such a ratio, the relay device will operate when the excitation inrush current comes. In other words, unnecessary operation outputs are sent out. As a countermeasure, it is considered to reduce the judgment value of the ratio of I _f2 /I _f1 to 0.1 or less, but if this value is too low, harmonic components ( There is a drawback that operation time is delayed due to failure (especially in the early stages of failure). Furthermore, in order to increase the suppression rate by I _f2 , a second harmonic pass filter 21b with a large Q is required, which has the drawbacks of lowering stability and delaying determination time.

Furthermore, there is also a means for locking the operation of all phases if the drive unit 20b of the I _f2 /I _f1 determination element of any one of the three phases is inoperative. However, such means complicate the configuration and reduce operational reliability. In addition, if a ground fault occurs in any phase when the transformer is turned on, the drive section 20 of the phase without the ground fault
b may cause the outputs of all phases to be locked. For this reason, the operating time of the relay device becomes longer, and there is a possibility that fault removal may be delayed.

This invention was made in view of the above-mentioned circumstances, and aims to ensure that the transformer does not malfunction even in the case of an excitation inrush current in which I _f2 /I _f1 becomes smaller than 0.1, and also to ensure protection against internal failures of the transformer. It is an object of the present invention to provide a highly reliable protective relay device that can simplify the configuration.

An embodiment of the present invention will be described below with reference to the drawings, in which the same parts as in FIG. 1 are denoted by the same reference numerals.

In FIG. 2, the output of the operating value setting section 28 is supplied to the second minus input terminal of the second comparison section 23,
The second comparator 23 derives the difference between the fundamental wave component (I _f1 ) and the second harmonic component (I _f2 ) multiplied by the suppression rate and the operating value setting amount. The derived difference is supplied to the integration circuit section 29 and integrated. The second level detection section 26 detects that this integral value has reached a predetermined level, drives the drive section 20b, and contacts 19
Turn on b.

Next, the operation of the above embodiment will be described using FIGS. 3A and 3B.

Figures 3A and 3B are explanatory diagrams of the response to the excitation inrush current, and the inrush current is I _f2 /I _f1 = 0.089 in the first wave of inrush, and I _f2 /I _f1 = 0.15 in the fourth wave. It is. In Figure 3B, the constant K is 5.64. I _f1 is the fundamental wave component included in the rush current, and assuming that the input is 8 times the minimum operating value I _p in the first wave, I _f2 = 0.089 x I _f1 = 0.089 x 8 I _p 's second harmonic. This means that it contains wave components. The constant K is set by the suppression rate setting section 25, and as described above, K=
When set to 5.64, I _f1 = 6.5I When _p input, I _f2 /I _f1 = 0.15
The operating limit is reached. This operating limit is the fourth wave in FIG. 3A.

When the setting output of the suppression rate setting section 25 and the setting output of the operation value setting section 28 are inputted to the minus input terminal of the second comparison section 23, the output becomes the shaded portion shown in FIG. 3B. This output becomes an input to the integration circuit section 29, where it is integrated. Integral circuit section 2
If the integral constant is determined so that the relay device does not cause unnecessary operation based on the value input in 9, the response when a fault current of the same magnitude as the first wave of the magnetizing inrush current flows is as shown in Figure 4. It will look like B. That is, the operating time is the time when the area of the shaded area in FIG. 4B is equal to the area of the shaded area in FIG. 3B. This operation time is about 17 mS from FIG. 4B.

When the time constant of the integrator circuit section 29 is determined as described above, the operating time characteristic becomes an inverse time characteristic as shown in Fig. 5, which is approximately 17 mS with an input of 8 times the minimum operating value I _p .
It's getting old. If the structure is configured to have such an inverse timing characteristic, the second harmonic component (the first
I _f2 / I _f1 = 0.089) A relay device can be obtained that does not operate unnecessarily in response to inrush currents, and operates at a high speed of 30 mS in response to transformer fault currents that are 5 times the minimum operating value. .

Regarding transformer inrush current, it is well known that as the transformer capacity decreases, the peak value of the first wave inrush current increases, but the attenuation rate of the peak value over time increases. On the other hand, the results of actual measurements and simulation studies regarding the second harmonic content rate show that I _f2 /I _f1 also changes with time as the transformer capacity becomes smaller.
It is becoming clear that the rate of increase in I _f2 /I _f1 is large.

Therefore, if the tendency of the magnetizing inrush current is examined in relation to the area of the shaded portion in FIG. 3B, the peak value of the first wave will be large if the transformer capacity is small. Therefore, I _f1 also increases, so (I _f1 − KI _f2 )
Also, the length of the area of the hatched portion in the vertical direction becomes longer. Also, since the attenuation of I _f1 is large and the increase of I _f2 is large over time, (I _f1 − KI _f2 )
The point where I intersects I _p (that is, the time when the amount of movement and the amount of inhibition become equal) becomes shorter, and the length of the diagonal triangle in the horizontal direction becomes smaller.

On the other hand, when the transformer capacity is large, the peak value of the first wave becomes small and I _f1 also becomes small, so (I _f1 - KI _f2 ) becomes small. Therefore, although the vertical length of the diagonal triangle mentioned above becomes smaller, the attenuation of I _f1 over time also becomes smaller.
Therefore, the increase in I _f2 becomes smaller, and the length of the triangle in the hatched area in the lateral direction becomes longer.

Figure 3B due to the difference in transformer capacity as mentioned above.
The difference in the areas of the triangles in the shaded area is small. As a result, if the time constant of the integrating circuit section 29 is determined based on the example of the magnetizing inrush current with the smallest I _f2 /I _f1 in the first wave, unnecessary operations can be avoided even with the magnetizing inrush current of all transformers. It is possible to obtain a relay device without Figure 3B
is an example of the inrush current for a transformer with a small capacity of about 15 MVA, assuming a fairly large residual magnetic flux.If the integral time constant is set to avoid unnecessary operations at this level, the magnetizing inrush current of most transformers can be achieved. It is thought that unnecessary operations will not occur even if the

FIG. 6 shows another embodiment of this invention,
The same parts as in FIGS. 1 and 2 are designated by the same reference numerals. In the embodiment shown in FIG.
Level detection section 18, contact 19a and drive section 20a
is omitted, and the output of the first rectifier 15 is converted to the second comparator 2.
The input signal is input to the minus input terminal of No. 3. With this configuration, the circuit configuration can be greatly simplified.

As described above, according to the present invention, the operation amount of the fundamental wave component of the vector sum, the suppression amount of the second harmonic component thereof, and the setting amount of the operation value setting section are supplied to the comparison section, Since the difference between these quantities is obtained and this value is integrated by the integrating circuit, the following advantages can be obtained.

B. Even for inrush currents where I _f2 /I _f1 becomes smaller than 0.1 in the first inrush wave, the I _f2 /I _f1 judgment factor is
Even if set to 0.15, unnecessary operations will not occur when the transformer is turned on.

B Despite having the above-mentioned features, due to the inverse time-limiting characteristic that the time limit becomes faster as the fault current I _d increases, sufficient transformer protection coordination cannot be achieved against internal faults in the transformer. .

Fault current 5 times the minimum operating value (approximately the rated current)
1.5 times), high-speed operation of 30ms can be achieved, ensuring high-speed removal of transformer failures.

(d) Unnecessary operations can be prevented when the transformer is turned on even when the aspect of the magnetizing inrush current changes depending on the size of the transformer capacity.

E. Suppression due to the second harmonic can be determined independently for each phase, so the transformer protection relay device for each phase can be configured independently for each phase, simplifying the circuit configuration and improving reliability. You can also aim for

(f) Since the suppression method is independent for each phase, even if a ground fault occurs when the transformer is turned on, the fault can be quickly removed.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional ratio differential relay device for protecting a transformer, Fig. 2 is a block diagram showing an embodiment of the present invention, Figs. 3 A and B, and Figs. 4 A and B.
5 are waveform diagrams and characteristic diagrams for describing the operation of the above embodiment, and FIG. 6 is a block diagram showing another embodiment of the present invention. 12...Scalar sum detection section, 13...Vector sum, 23...Second comparison section, 26...Integrator circuit section,
26...Second level detection section, 19b...Contact, 2
0b...Drive unit.

Claims (1)

[Scope of Claims] 1. A first output of a ratio differential relay element whose suppression amount is the scalar sum of current transformer outputs of the transformer terminals and whose operating amount is the vector sum, and a fundamental wave component of the vector sum. If ₁ is the operation amount and the second harmonic component If ₂ is the suppression amount, the second output of the second harmonic content determination element is provided, and when the AND condition of the first and second outputs is satisfied, In a relay device that sends relay output,
The operation amount of the fundamental wave component of the vector sum, the suppression amount of its second harmonic component, and the setting amount from the operation value setting section are each input, the difference of each amount is obtained as an output, and this value is set as a predetermined value. A protective relay device characterized in that an integrating circuit section having a time constant performs integration, a level detecting section detects that the integrated value reaches a predetermined level, and the second output is obtained. . 2 The above integral time constant is ∫ ^t _O (If ₁ −
KI _f2 - I _p ) dt, I _p is an operating value, K is a constant, and t is the time until I _f1 - KI _f2 = I _p . Range 1
Protective relay device as described in Section.