JPS6364518A - Protective relay - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a protective relay for protecting a healthy power system and load-side equipment from power system accidents.

(Prior art) Conventionally, the accuracy of the operating point of a protective relay is based on JISC4602.
It is defined in standards such as JEC, 174A, and IEC255.

On the other hand, it is known that the input/output characteristics of an auxiliary transformer (hereinafter referred to as AUT) are generally not linear, and when the input is large, the iron core is saturated and the output does not correspond to the transformation ratio.

For this reason, AUTs of class 1 and 0 level, whose characteristics are stipulated by JEC190 etc. and whose input/output characteristics are linear within the required range, are used, but the iron core used in the AUT is large, and the AUT itself is also large. This also poses a problem in terms of price.

(Problems to be Solved by the Invention) The object of the present invention is to provide a compact and inexpensive 3.0 class A
It is an object of the present invention to provide a reasonable maintenance relay that uses UT and can obtain the same accuracy as the conventional one.

[Structure of the invention]

(Means and effects for solving the problems) The present invention provides a protective relay that converts the output of an auxiliary transformer into a digital value via an A/D converter and operates the relay via a CPU. It is equipped with a memory that stores the nonlinearity of the transformer, and a ratio error setting section that corrects the nonlinear error according to the amount by which the output of the auxiliary transformer exceeds the range of the linear section. This is a small, low-cost protective relay that can be used in combination with an auxiliary transformer to obtain a highly accurate operating point.

(Example) An embodiment of the present invention is shown in FIG.

As shown in FIG. 1, the protective relay 11 is A'UT1
.

Converter 2. A/D converter 3. CPU4. memory 5,
1% fixed part6. AUT ratio error setting section (hereinafter referred to as ε setting section)7. It is composed of an auxiliary relay driver (hereinafter referred to as ALiRY driver) 8 and an auxiliary relay (hereinafter referred to as AURY) 9.

The amount of electricity required for protection is input via AUTl,
The secondary side output of tJTl is converted into a voltage at an appropriate level by a converter 2, and further converted into a digital value corresponding to an analog quantity by an A/D converter 3, and then sent to a CPU 4.
This digital value is used as a key and is exchanged with a value in a data table according to the characteristics of AUTl stored in advance in the memory S, and then sent to the AURY driver 8.
is input to operate AURY 9.

FIG. 2 shows an example in which the protective relay 11 is applied to a power system, and when current flows through the current transformer 10, current flows into the AUT 1 according to the current transformation ratio.

The current (2) is outputted by the AUTl as a current (2) according to its input/output characteristics, and the current (2) is converted into an appropriate voltage by the converter 2, and further converted into a digital value by the A/D converter 3.

Figure 3 is an example of the input/output characteristics of AUTl, where point B is
It shows the point (knee point) where the input/output characteristics of the UTl are no longer linear.

In addition, point 0 indicates the point of AUTI where the ideal error is 0% at the maximum current □α that requires protective operation, and point C' indicates the actual point of AUT 1 where the error is 3%, for example. , the digital value output by the A/D converter 3 is a value corresponding to C'.

Since the memory 5 stores the amount of electricity corresponding to the actual input/output characteristics of AUTl at the address corresponding to the output value of the A/D converter 3, the value of C' can be corrected as C, for example.

Further, an ε setting section 7 for correcting variations in the input/output characteristics of each AUT1 is provided, inputting the error C-C' of AUT1, and correcting the error by linear approximation calculation according to the output of AUT1.

That is, the secondary side output of AUTl is corrected according to the actual input/output characteristics using the data in the memory 5, and further
Individual variations in T1 are individually corrected by the itl fixing section 7.

That is, if the CPU 4 reads the digital value output by the A/D converter 3 and uses the content that matches the address value of the memory 5 as true data, the value of C' is corrected to the value of C.

Next, a method for more precise correction according to the input/output characteristics of each AtJT1 will be explained with reference to FIG.

It can be obtained by measuring I2α'.

I, = 1. When the error E when β is linearly approximated, I
,,: RX I, β , (■, -Ikko, K) La' =■,, (Iza-La) X H, so ■2. : [I! , 1-(Iza-I2α')I-K
]rπTakumi-ichiya(, (I-(X-I-α Explosion)) 077ryo 3-dama- becomes.

Next, the procedure for correcting the error is shown in the flowchart of FIG.

First, the metamorphic ratios R and L(t+Iza, I8.) are set in the memory 5 in advance.

The CPU 4 reads the contents of the address in the memory 5 corresponding to the digital value of the A/D converter 3 (step 1).
).

Next, this value is compared with the digital value corresponding to I□K (step 2).

At this time I! <If it is 2, proceed to the next process without making any corrections, and if 2 ≧ 2, read E from the E setting section 7 (
In step 3), the data is corrected by calculating an error corresponding to, for example, 2β - 2β' (steps 4 and 5).

As a result, even if an AUT with a larger ratio error than the conventional one is used, it is possible to achieve the same accuracy as the conventional one.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to realize a small and low-cost protective relay that does not reduce the accuracy of the operating point even when using a small and inexpensive AUT with a large ratio error of, for example, 3.0 class Bell. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the protective relay according to the present invention, FIG. 2 is a block diagram showing an application example of the protective relay according to the present invention, and FIGS. 3 and 4 are explanations of the error correction operation of the AUT. Figure 5 is the above error 3...A/D converter
4...cpu5...memory 6...
・Setting part 7... Ratio error setting part (E setting part) 8... AURY driver 9... Auxiliary relay (AURY) 10... Current transformer (CT) 11... Protective relay substitute Person Patent Attorney Nori Ken Chika Yudo Hirofumi Mitsumata No. 1 Figure 2 腅11k I/β l7CLII Kaya 4 Figure 1￥; Ta Figure

Claims (1)

[Claims] A protective relay that converts the output of an auxiliary transformer into a digital value via an A/D converter and operates the relay via a CPU includes a memory for storing nonlinearity of the auxiliary transformer, and a memory for storing nonlinearity of the auxiliary transformer. A protective relay comprising a ratio error setting section that corrects a non-linear error according to the amount by which the output exceeds the range of the linear section.