JPH0681417B2 - Digital bus protection relay - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital ratio differential busbar protective relay device for detecting an accident in a busbar of a power system by using a current differential principle.

[Conventional technology]

FIG. 6 shows a conventional digital busbar protective relay device disclosed in, for example, Japanese Patent Publication No. 58-18863. In the figure (9)
Is an adder, (10) is a differential amount derivation arithmetic circuit, (11-1) ~
(11-n) is an absolute value deriving circuit, (12) is an adder, (13) is a suppression amount deriving arithmetic circuit, (14) is a subtractor, and (15) is a comparator.

Next, the operation will be described. Generally, there is a differential method applying Kirchhoff's first law to detect an accident on a bus. Specifically, the secondary current of each current transformer installed on all lines connected to the bus is vector-synthesized. However, if the vector sum is greater than or equal to the specified value, it is determined that the busbar has an accident.
However, in practice, the ratio principle is often used for the purpose of preventing the relay from malfunctioning due to an error current due to saturation of the current transformer, and in the embodiment of FIG. A value proportional to the sum of absolute current values is used.
An analog amount of current introduced from the current transformer is converted into a digital current amount by an analog-digital converter (not shown) and becomes currents I ₁ , I ₂ ... I _n shown in FIG. Adder (9)
Then, the instantaneous currents I ₁ , I ₂ ... I _n are added to obtain an instantaneous differential value I _D , and this is calculated by the arithmetic circuit (10). For example, the square value of the current data and 1 / 4 The cycle value of the previous data is added, and the operation amount is proportional to the square peak value of the differential value I _D.
Take out I _D ² . The derivation circuits (11-1) to (11-n) derive the absolute values of the currents I ₁ , I ₂ ... I _n sampled from the secondary currents of the respective current transformers, and add them to the adder (12). Then, the suppression amount I _R of the instantaneous absolute value is determined as | I ₁ | + | I ₂ | + ... | I _n | = I _R. Since this suppression amount I _R is still instantaneous value data, its magnitude changes at each sampling cycle, so it is introduced into the arithmetic circuit (13), integrated for 1/2 cycle, and made a value that does not change depending on the sampling cycle. Further, a square calculation is performed so as to obtain cooperation with the motion amount, and then a constant K as a suppression ratio is multiplied to obtain a suppression amount KI _R ² . Subtractor (14) intended to make the ratio characteristic of the relay, the arithmetic circuit suppression quantity KI _R ² operation amount I _D ² and the arithmetic circuit (10) (13) is introduced, the I _D ² -KI _R ² Perform subtraction. This result is compared with a constant K _O by a comparator (15), and when it is larger than the constant K _O , it is determined to be an internal accident in the bus and a signal for executing a protection operation is output.

[Problems to be Solved by the Invention]

Since the conventional digital bus protective relay device is constructed as above, as it is clear even arithmetic expression I _D ² -KI _R ^2, takes time operation because it takes square operation, also when an internal fault In order to ensure reliable operation, it is necessary to set the suppression amount KI _R ² to a certain value or less, and extreme CT during an external accident
There was a problem such as the possibility of malfunction due to saturation.

The present invention has been made to solve the above problems, and it is an object of the invention to obtain a digital busbar protective relay device which has a short calculation time and does not have a risk of malfunction even if extreme CT saturation occurs in the event of an external accident. To aim.

[Means for Solving the Problems]

The digital bus protection relay device according to the present invention operates when the differential current exceeds a certain value and the absolute value of the current proportional to the maximum value of the secondary current of the current transformer of each line | I _T ｜
The absolute value of the differential current | using an instantaneous value _{of, | | I D I T |} -
(Η ₁ | I _D | + η ₂ | I _Dt |)> K ₂ (where η ₁ , η ₂ and K ₂ are constants, I _Dt is a differential current based on 90 ° pre-sampled data, for example) Is provided, and the operation output of the differential element is locked for a certain period of time during operation of this ratio element.

[Action]

The ratio element in this invention prevents the operation by canceling the terminal current │I _T │ completely by the effect of the differential current _{│I D} │ or _{│I Dt} │ in order to make it inoperative in the case of an internal accident. Sometimes, even if a large current penetrates and the differential element malfunctions, this ratio element operates completely and locks the final output.The point is that a large current penetrates in the event of an external accident. Even if CT saturation occurs, there is always an unsaturation period for a certain period of time, and an external accident is judged within this period.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) is a bus bar, (2-1) to (2-n) are current transformers,
(3-1) to (3-n) are input converters that convert an appropriate output proportional to the secondary current of the current transformers (2-1) to (2-n) and remove unnecessary harmonic components. Vessel, (4) digital relay, (5) A /
D converter, (6) memory for temporarily storing input data, calculation results, etc. (hereinafter referred to as RAM), (7) memory for storing programs (hereinafter referred to as ROM),
(8) is a microprocessor (hereinafter referred to as CPU).

Although the secondary currents of the current transformers (2-1) to (2-n) are not shown, an A / D converter (5) composed of a sample hold circuit, a multiplexer, an analog-digital converter, etc.
The digital amount proportional to the instantaneous current value for each fixed period
It is converted to I ₁ ~I _n. This digital current input is RAM (1
The CPU executes the calculation while reading the data from the RAM according to the calculation program written in 2) and stored in the ROM. The protection performance of the digital relay is determined by how the program is set up, and its advantage lies in how efficiently the objective can be achieved (shortening the calculation time).

FIG. 2 is a waveform diagram for explaining the principle of the present invention, FIG. 3 is a principle block diagram, FIG. 4 is a one-terminal ratio characteristic diagram showing operating characteristics, and FIG. 5 is a program for making this principle. It is a flowchart. Fig. 2 shows an example of a case in which an accident current concentrates on the current transformer at the accident end and causes an extreme CT saturation during an external bus line accident. The waveform ΣI _1N is the sum of the secondary current of the inflow end current transformer, and it is assumed that the inflow end current transformer is not saturated in consideration of severe conditions. Waveform I _OUT shows the case where the secondary current of the external fault end current transformer causes excessive CT saturation due to the influence of excessive current and transient DC component current. Waveform I _D shows the vector sum of the inflow end current sum I _1N and the outflow end current I _OUT as a differential current, and acts as the operation amount of the ratio differential relay. Waveform ｜ _IT
| Is the absolute value of the current proportional to the largest value among the secondary currents of the respective current transformers, and this is called the maximum suppression amount. The normal ratio differential relay compares the size of the waveform I _{D with} the size of the waveform | I _T | and operates when the ratio of the sizes is greater than a certain value and the waveform I _D is large. K = I _D / I _R or K = I _D ² / I
As mentioned above, _R ² is designed to be fully operational in an internal accident K <
Since it is an appropriate value of 1, for example, if a DC component is included in the fault current, the current transformer will be extremely saturated and malfunction. The purpose of this principle is to
It is to be a high-performance device that does not malfunction even if saturation occurs. I _T | | waveform Note the dotted portion in solid line, but by inflow end current occurs, for simplicity, omitted, and the severe side. The waveform η ₁ │I _D │ is the absolute value of the waveform I _D multiplied by a constant η ₁ , and the waveform η _{2 │I Dt} │ is the differential amount | I calculated from the sampling data before time t of the waveform I _{D. Dt}
It is a product of | multiplied by a constant η ₂ , that is, a product of the waveform η ₁ | I _D | phase-shifted by time t multiplied by a constant η ₂ . Waveform │I _R │ is waveform │I _T │ waveform η ₁ ｜ I _D ｜ ＋ η ₂
It is shown that the difference appears only when | I _Dt | is subtracted and the difference becomes positive. Waveform (118) is a waveform | those levels occurs only when the K ₂ or more, | | I _R I _R
It is shown that the calculation result of | = | I _T | − (η ₁ | I _D | + η ₂ | I _Dt |) produces an output (118) at | I _R | K ₂ . Waveform (11
9) shows that if the waveform (118) occurs, the signal is stretched for the time T _R , and the pulse signal of the waveform (118) is made continuous like the waveform LOCK.

This output waveform LOCK locks the operation of the relay. The main point of this principle is to utilize the CT saturation phenomenon in a waveform. Any current transformer has an unsaturated period for a certain time immediately after the accident occurs, and after the second wave, it depends on the DC component attenuation in the accident current. Since there is a negative wave period corresponding to the alternating current generated and an unsaturated period corresponding to the positive wave area corresponding to the negative wave area, an external accident judgment is made during this unsaturated period and the result (lock output) is continued for a certain period of time. This prevents malfunction during the saturation period. On the other hand, at the time of an internal accident, the differential current is always greater than or equal to the CT secondary current of each line.
The waveform I _R will be erased by the differential current, and the lock output will not occur. Further, when an internal accident Toka when the current phase of each line is different, a strain wave current or the like at the time of the accident, the differential current I _D to the terminal inhibition current generated in proportion to the respective line current | I _T | Waveform even if the phase of
I _T | waveform eta ₁ to allow erased | I _D | Separately aid of eta ₂ is | I _Dt | a | I _D | make _{more, η 1 | I D | +} η 2 | I D | or eta ₁ | The larger of I _D | and η ₂ | I _Dt | is used for suppression elimination. Incidentally waveform η ₂ | I _Dt | of eta ₂ are constants eta _|>
│I _Dt │ is an appropriate value of η ₂ and is phase-shifted from │I _D │ by time t. (101) in FIG. 3 is a differential element that operates when the differential current I _D is a certain value or more, and (102) is the terminal suppression amount | I _T | of the instantaneous absolute value having the performance described in FIG. Instantaneous absolute value comparison ratio element for instantaneous comparison calculation of the differential amount | I _D |, (103) is a delay timer for delaying the output of the element (102) for a certain period of time, and (104) is a negative input terminal With the AND element of, the element (101) operates and operates when there is no output of the delay timer (103). (105) outputs an output when the output of the element (104) operates continuously a plurality of times. All the above components are processed by the digital relay (4) as software. FIG. 4 shows the relationship between the differential amount I _D and the terminal suppression amount I _T in the fundamental wave input 1 terminal ratio characteristic which is one of the basic characteristics of the present invention. Characteristic (10
6) is the operating characteristic (characteristic of element (101)) that operates when the differential amount I _D is a certain value or more, and (107) is the differential amount I _D and the suppression amount | _IT |
Is a characteristic (the characteristic of the element (102)) that operates when the ratio of is less than a certain value. Overall, the operating range of the characteristic (106) and the characteristic (107)
The overlapping part of the non-operating area of is the operating area of the relay. As described with reference to FIG. 2, the characteristic (107) has a calculation principle of | I _T |-(η ₁ | I _D | + η ₂ | I _Dt |) = | I _T |-| I
_{Since R} | K ₂ , if the constant K ₂ is K ₂ ≈0, then | I _T | and I
It shows that _D has a constant ratio relationship.

A flow chart showing the principle program of the present invention is shown in FIG. The processing block of (110) is the current transformer (2-
1) to (2-n) output proportional to the secondary current
1) to (3-n) convert to an appropriate voltage and A / D converter (5)
Indicating that those sampled at the same time a constant period in unison these instantaneous values further analog / digital conversion, reads what the output data I ₁ ~I _n has been temporarily stored in the memory (6) sequentially in . Data I _{1 to} I _n are read from the memory (6) and added by the CPU (8) (Block (113) processing), the absolute value | I _D | of the differential amount I _D is calculated (block (114) processing), and the result is temporarily stored in the memory (6). As a branch processing Matabetsu, the absolute value of the data _{I 1 ~I n | I 1 |} ~ | I n | ( processing block (111)) calculated by the maximum value of which | I _T | = | Max
[| I ₁ |-| I _n |] | is calculated (block (112) processing), and the result is temporarily stored in the memory (6). Next, the data temporarily stored in the memory (6) | I _T |, | I _D |
_Dt | is read sequentially | I _R | = | I _T |-(η ₁ | I _D | + η ₂
| I _Dt |) is calculated (block (116) processing) and | I _R |
When K ₂ (K ₂ is a constant) is determined, an output signal is output (block (117) processing). Note that this output signal is a predetermined time T _R
Is operated maintained for, again blocks during the holding time T _R (11
If me operation signal 7) is re-counts the timer, so as to hold more T _R-time processing (block (119)). Next, the amplitude value of the differential amount I _D is calculated as the process of the block (120). This is done by adding 1/2 cycle of the absolute value | I _D | The calculation is performed by a known method such as a rectification type in which the average value is calculated, or a vector type in which the sum of the current data square value of the instantaneous value I _{D and} the data square value before 1/2 cycle is calculated. Calculation results above (118)
The logical judgment of (element (102) operation) and (122) (element (101 operation) is performed by the NOT circuit 123 and the AND circuit (124), and finally, if continuous operation is confirmed a plurality of times, it is judged as a bus accident. Relay output.

In the above embodiment FIG. 5 of the treatment with block _{(116) | I R | =} | I T | - (η 1 | I D | + η 2 | I Dt |) and the but, (η ₁ | I _{D | + η 2 | I Dt |} ) instead eta ₁ of | I _D | or eta ₂ | may be utilized whichever larger, | | I _Dt I _Dt is now data | I _D | than 90 Data such as before 60 ° or before 60 ° may be used. Furthermore, (η ₁ | I _D | + η ₂ |
I _Dt |) is You may use the maximum value of. Where η ₁ , η ₂ , and η ₃ are η ₁
> Η ₂ > η ₃ constant, Is │ I _D │ t ₁ hour before (eg 60 °) data Is data t ₂ hours before (| _D |) (for example, 90 °).

〔The invention's effect〕

As described above, according to the present invention, as a countermeasure against CT saturation, since the ratio differential method that calculates the instantaneous value data of the current based on the addition and subtraction and the multiplication of the constant is adopted, the calculation time is short and the current transformer unsaturated period Only the current data of is used for external accident judgment, and it is configured to operate logically during the saturation period. Therefore, even if the current transformer during an external accident is extremely saturated, it can be surely inoperative. It has the effect of obtaining

[Brief description of drawings]

FIG. 1 is a principle block diagram of a digital busbar protective relay device according to an embodiment of the present invention, FIG. 2 is an example of a waveform diagram at the time of an external accident for explaining the principle of the present invention, and FIG. 3 is an algorithm of the present invention. FIG. 4 is an example of a characteristic diagram of the present invention, FIG. 5 is an example of a flow diagram showing a program of the present invention, and FIG. 6 is a principle block diagram of a conventional digital bus protection relay device. . In the figure, (1) is a bus bar, (2-1) to (2-n) are current transformers, (3-1) to (3-n) are input converters, (4) is a digital relay, (5) ) Is an A / D converter, (6) is a memory (RA
M) and (7) are memories (ROM), and (8) is a microprocessor (CPU). The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Anzai 1-2-2 Wadazaki-cho, Hyogo-ku, Kobe, Hyogo Prefecture Mitsubishi Electric Corporation Control Works (72) Inventor Yoshifumi Oura 1-chome, Uchisaiwai-cho, Chiyoda-ku, Tokyo 1-3, Tokyo Electric Power Co., Inc. (72) Inventor, Kunio Matsuzawa, 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Ltd. (72) Inventor, Kazuyoshi Yoshida, 1-1, Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 3 in Tokyo Electric Power Company

Claims (3)

[Claims] 1. An A / D converter that samples the currents of all lines connected to a bus at the same time at regular intervals and digitally encodes them, and outputs the output current data, operation results, etc. temporarily. A memory (RAM) for storing data in a memory, a memory (ROM) for storing a predetermined calculation program, and a microprocessor (CP) for calculation processing according to the program.
U) and the maximum value of the instantaneous absolute value data of all line currents is calculated, this is defined as the suppression amount | I _T |, and the difference obtained by adding the instantaneous value data of all line currents at the same time Momentum I
_D and the differential amount I _Dt a predetermined time before I _D , | I _T | − (η ₁ | I _D | + η ₂ | I _Dt |) ≧ K ₂ However, η ₁ , η ₂ , K ₂ Is a constant. For determining the magnitude of the differential amount I _D , and the output signal of the calculation result of the first calculation means for a fixed time T _R when the operation is determined. And a third calculation means for counting T _R again when the first calculation result outputs a motion determination output within the delay time T _R , and the calculation result of the third calculation means During the period in which the extension signal is generated, the operation output signal which is the calculation result of the second calculation means is locked. 2. The first calculation means is: | I _T |-(η ₁ | I _D | + η ₂ | I _Dt |) ≧ K ₂ (η ₁ | I _D | + η ₂ | I _Dt |) To η ₁ ｜ I _D ｜ or η ₂ ｜ I
The digital busbar protective relay device according to claim 1, wherein only the larger one of _Dt | is made to act. 3. The first calculation means is: | I _T |-(η ₁ | I _D | + η ₂ | I _Dt |) ≧ K ₂ (η ₁ | I _D | + η ₂ | I _Dt |) Where (η ₁ | I _D | + η ₂ | I _Dt1 | + η ₃ | I _{Dt 2} |) where η ₁ , η ₂ and η ₃ are constants of η ₁ ＞ η ₂ ＞ η ₃ and | I _{Dt 1} ｜ is | I Sampling data t ₁ hours before _D |, | I _Dt2 | is sampling data t ₂ hours before | I _D |. The digital busbar protective relay device according to claim 1, wherein