JP2688273B2 - Protective relay - Google Patents

Description

The present invention relates to a protective relay that protects a power system.

[Conventional technology]

FIG. 4 shows, for example, the method of Table 4-1-3 of "Electrical Cooperation Research, Vol. 41, No. 4, Digital Relay" P45, product form C
FIG. 6 is a diagram for explaining an algorithm of the conventional digital operation type power direction relay shown in FIG.

The following formula is shown in the above table as a calculation principle formula for obtaining the electric power direction.

|||| cos θ = v _m · i _m ＋ v _m-3 · i _m-3 (1) where || ・ ||; amplitude value θ of voltage / current θ; phase difference i of voltage / current _m , v _m ; digital data of current and voltage at time m i _m-3 , v _m-3 ; digital data of current and voltage 3 samples before time m Further, here, sampling time width β At an electrical angle of 30
In this case, the sum of the inner product value of the current and voltage at time m and the inner product value of the current and voltage at an electrical angle of 90 ° from this time m is obtained.

Now, as shown in FIG. 4, the amount of electricity input to the relay is i (t) = I _p sin (ω ₀ t) …… (1) v (t) = V _p sin (ω ₀ t + θ) …… ( 2) and the value of the frequency ω ₀ t at the time point of time m is α, each sample value is given by the following equation.

i _m = I _p sin α (3) v _m = V _p sin (α + θ) (4) Therefore, before that, the sample value at the time point m−k is given by the following equation.

i _mk = I _p sin (α-k β) (5) v _mk = V _p sin (α-k β + θ) (6) However, I _p , V _p ; Current and voltage amplitude β: Sampling Time width θ: Leading angle (phase difference) of voltage when current is used as reference: k: k = 1,2,3, ....

 Here, focusing on the right side of Expression (1), the following is obtained.

i _m v _m + v _m-3 v _m-3 = I _p sin αV _p sin (α + θ) + I _p sin (α-3β) V _p sin (α-3β + θ) = I _p V _p {sin α sin (α + θ) + sin (α -3β) sin (α-3β + θ)} = I _p V _p {sin α sin (α + θ) + cos α cos (α + θ)} = I _p V _p cos θ (8) That is, the separation of 3 samples of data is an electrical angle. 90
It means that there is a gap of ゜.

[Problems to be solved by the invention]

Since the conventional protective relay is configured as described above, "system frequency is always kept constant,
To establish as a digital relay, the frequency
Sampling time width β corresponding to frequencies such as 50Hz and 60Hz
It is necessary to determine exactly "," is based on the premise of the arithmetic principle formula.

Therefore, for frequency fluctuations in the system, the premise of sin (α-3β) sin (α-3β + θ) = cosαcos (α + θ) in Equation (8) is broken and the equal sign is no longer established. In addition to the influence that cannot be ignored in terms of protection ability in terms of the calculation principle, there is a problem that unless the sampling time width β is changed depending on the frequency, the error becomes large and it becomes unpractical.

Furthermore, depending on the system frequency, it is necessary to set the sampling time width β to a multiple of 30 °, and in the case of formula (8), in order to obtain an effective calculation result as a power direction relay, A time equivalent to 90 ° (4.167ms for 60Hz, 5ms for 50Hz) is necessary (the processing time of the processing device is neglected). As described above, it is difficult to shorten the detection time, and there are problems such as a limit for high speed operation.

The present invention has been made to solve the above-mentioned problems, and it is not necessary to change the sampling time width β depending on the frequency to be handled while improving the characteristic change due to frequency fluctuation, that is, 50Hz, 60Hz common type operation The purpose is to obtain a protective relay that can be handled by a processing circuit.

[Means for solving the problem]

A protective relay according to the present invention detects a voltage and a current of a power system, samples voltage data and current data with a predetermined sampling time width, quantizes them, and temporarily stores the current data. Of the first electric quantity and the second electric quantity by an arithmetic storage room and an arithmetic circuit for defining and processing the sampling values of the current and voltage and the arithmetic sequence stored in the temporary storage room, and outputting them. The four arithmetic circuits and the first electric quantity to the second
And a determination amount derivation unit that outputs the determination result by determining whether or not the power direction component is greater than zero by subtracting the electricity amount of the above.

(Operation)

The protective relay according to the present invention derives the product amount of the current and voltage sampling data of the power system to obtain the first electricity amount and the second electricity amount, and obtains and determines the power direction component.
Then, in determining the power direction component, three components of the electricity quantity, that is, a component related to the phase difference (θ) between the current and the voltage, a component related to the second harmonic (2α), and the sampling time. Of the components related to the width (β), the sampling time width and the components related to the second harmonic are removed from the phase difference component so that only the components related to the phase difference between the current and voltage are taken and the sampling order of the input sampling data is Since it is regulated, it is highly accurate and stable against frequency fluctuations, and 50 ^HZ , 60
A relay that shares the sampling time width with ^HZ can be obtained.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a distribution path for digitally quantized current data, 2 is a distribution path for voltage data, 3 to 5 are temporary storage rooms for current data, and 6 to 10 are temporary storage rooms for voltage data. , 11, 13, 18, and 21 are subtraction circuits, 12, 14, 16, 17, and 19 are multiplication circuits, 15 is an addition circuit, 20 is a division circuit, and 22 is a determination amount derivation unit.

Next, the operation will be described. First, digital data strings ... i _m-1 , i _m , i are respectively allocated to the current and voltage data distribution paths 1 and 2.
_{m + 1} , ... and ... v _m-2 , v _m-1 v _m , v _{m + 1} , v _{m + 2} ... are always constant sampling time width β (in the present invention, like the conventional digital relay, Depending on the system frequency, it is not necessary to specify an electrical angle of 30 ° or a multiple thereof).
The temporary storage rooms 3-5 and 6-10 for current and voltage data are
Now, it is assumed that i _{m + 1} , i _m , i _m-1 , v _{m + 2} , v _{m + 1} , v _m , v _m-1 , and v _m-2 are stored, respectively.

The loading / unloading of the data in the temporary storage rooms 3 to 10 is controlled by another control system (not shown).

For example, if the current data i _{m + 3} appears as the latest data in the distribution path 1 (of course, in synchronization with this, the data distribution path 2
Also v _{m + 3} appears. ), In the temporary data storage room 5, the data i _m-1 is cleared and the data i _m is stored. At the same time, data i _m is cleared and data i _{m + 1} is stored in the temporary data storage room 4, and i _{m + 1} is cleared and data i _{m + 2} is stored in the temporary data storage room 3. . At this time, the clearing and storing of the data in the temporary data storage rooms 3 to 5 are also controlled by another control system.

Also, the operations of the temporary storage rooms 6 to 10 for voltage data are exactly the same as those of the temporary storage room for current data.

Temporary data storage room 6 has v _{m + 3} and also 7
v _{m + 2} , 8 also stores v _{m + 1} , 9 also stores v _m , and 10 stores v _m-1 .

The subtraction circuit 11 receives the outputs of the current data temporary storage rooms 3 and 5 as inputs, and im _{++ 1-} i _m-1 I _p {sin (α + β) -sin (α-β)} = 2I _p cos αsinβ ...... (9) is derived and output.

The multiplication circuit 12 receives the outputs of the temporary storage room 4 for current data and the temporary storage room 8 for voltage data, respectively, Then, the subtraction circuit 13 receives the outputs of the temporary storage rooms 7 and 9 of the voltage data as inputs, and v _{m + 1} −v _m−1 = V _p {(sin (α + β + θ) −sin (α −β + θ)} = 2V _p cos (α + θ) sinβ …… (11) is derived and output.

Further, the multiplication circuit 14 receives the output of the voltage data temporary storage room 8 as an input, derives and outputs 2 v _m , and the addition circuit 15
Is the input of the outputs of the temporary storage rooms 6 and 10 of the voltage data, v _{m + 2} + v _m-2 = V _p {(sin (α + 2β + θ) + sin (α-2β + θ)} = 2V _p sin (α + θ) cos2β ...... (12) is derived and output.

Then multiplying circuit 16 is input with the output of the multiplier circuit _{12, 2i m v m = I} p V p {cosθ-cos (2α + θ)} ...... (13) derived by the output, the multiplier circuit 17, the output of the subtraction circuit 11 and 13 respectively as _{input, (i m + 1 -i m} -1) (v m + 1 -v m-1) = 2I p cosαsinβ × 2V p cos (α + θ) sinβ = I p V _p (1-cos2β) {cosθ + cos (2α + θ)} (14) is derived and output, and the subtraction circuit 18 outputs the multiplication circuit 14 and the addition circuit 1
The output of 5 is input, and the following equation (15) is derived and output.

v _{m + 2} −2v _m + v _m−2 = V _p {(sin (α + 2β + θ) −2 sin (α + θ) + sin (α−2β + θ)} = 2V _p sin (α + θ) (cos2β−1) …… (15) Division The circuit 20 receives the outputs of the multiplication circuit 14 and the subtraction circuit 18, respectively, and derives and outputs the following equation (16) (however, v _{m + 2} −2v _m + v _m-2 ≠ 0, V _p sin (α + θ) (cos2β-
1) ≠ 0).

The multiplication circuit 19 receives the outputs of the multiplication circuit 17 and the division circuit 20, respectively, and derives and outputs the following equation (17) (however, v _{m + 2} −2v _m + v _m-2 ≠ 0, cos2β −1 ≠ 0).

The subtraction circuit 21 receives the outputs of the multiplication circuits 16 and 19 respectively,
Formula (18) below is derived and output (however, v _{m + 2} + 2v
_m + v _m-2 ≠ 0, cos2β-1 ≠ 0).

Finally, the calculation result of the subtraction circuit 21 is output to the determination amount deriving unit 22 to obtain the power direction component (19) (where v
_{m + 2} −2v _m + v _m-2 ≠ 0, cos2β−1 ≠ 0).

In the above description, the case where the denominator in each arithmetic expression does not become zero is described, but it goes without saying that when the denominator becomes zero, a separate process such as discarding the calculation result is performed.

 Next, FIG. 2 shows another embodiment of the present invention.

In the drawing, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

5-1 is a temporary storage room for electric current data, in which im _-2 is stored. 25, 27 and 31 are subtraction circuits, and 26, 28, 29 and 30 are multiplication circuits.

The subtraction circuit 25 is a temporary storage room for current data 4 and 5-1.
The output of each is input and the equation (20) is derived and output.

i _m −i _m−2 = I _p {sinα−sin (α−2β)} = 2I _p cos (α−β) sinβ (20) Further, the multiplication circuit 26 stores the current data in the temporary storage room 5 Then, using the output of the temporary storage room 9 for voltage data as input (2
Formula 1) is derived and output.

The subtraction circuit 27 receives the outputs of the temporary storage rooms 8 and 10 for the voltage data, respectively, and derives and outputs the following equation (22).

v _m −v _m−2 = V _p {sin (α + θ) −sin (α−2β + θ)} = 2V _p cos (α−β + θ) sin β (22) The multiplication circuit 28 outputs the outputs of the subtraction circuits 25 and 27. , Respectively, and formula (23) below is derived and output.

(I _m −i _m-2 ) (v _m −v _m-2 ) = 2I _p cos (α−β) sin β · 2V _p cos (α−β + θ) sin β = I _p V _p 2sin ² β · 2cos (α −β) cos (α−β + θ) = I _p V _p (1-cos2β) {cos θ + cos (2α-2β +
θ)} (23) Further, the multiplication circuit 29 receives the outputs of the multiplication circuit 28 and the division circuit 20, respectively, and derives and outputs the following equation (24) (however, v _{m + 2} −2v _m + v _m-2 ≠ 0, cos2β−1 ≠ 0).

Then, the multiplication circuit 30 receives the output of the multiplication circuit 26 and derives 2i _m-1 v _m-1 . The subtraction circuit 31 causes the multiplication circuits 29, 30
The respective outputs are input and the following equation (25) is derived and output (provided that v _{m + 2} −2v _m + v _m−2 ≠ 0, cos 2β−1 ≠ 0).

Finally, the calculation result of the subtraction circuit 31 is output to the determination amount derivation unit 22, and the power direction component (26) is obtained (however, v _{m + 2} −2v _m + v _m−2 ≠ 0, cos2β− 1 ≠ 0).

When the denominator becomes zero, the same processing as that described in the embodiment of FIG. 1 is necessary.

 Furthermore, FIG. 3 shows another embodiment of the present invention.

In the drawings, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding portions.

3-1 is a temporary storage room for current data, in which i _{m + 2} is stored. 35, 37, 41 are subtraction circuits, and 36, 38-40 are multiplication circuits.

First, the subtraction circuit 35 operates in the temporary storage room for current data 3-
The outputs of 1 and 4 are input, and the following equation (27) is derived and output.

i _m −i _{m + 2} = I _p {sinα−sin (α + 2β)} = 2I _p cos (α + β) sinβ (27) The multiplication circuit 36 temporarily stores the current data 3 and temporarily stores the voltage data. The output of the storage room 7 is used as the input, and (2
Equation 8) is derived and output.

The subtraction circuit 37 receives the outputs of the voltage data temporary storage chambers 6 and 8 as inputs, derives the following formula (29), and outputs it.

v _m −v _m−2 = V _p {sin (α + θ) −sin (α−2β + θ)} = 2V _p cos (α + β + θ) sin β (29) Then, the multiplication circuit 38 outputs the outputs of the subtraction circuits 35 and 37. , Respectively, and formula (30) below is derived and output.

(I _m −i _{m + 2} ) (v _m −v _{m + 2} ) = 2I _p cos (α + β) sin β · 2V _p cos (α + β + θ) sin β = I _p V _p (1-cos2β) {cos θ + cos (2α-2β +
θ)} (30) The multiplication circuit 39 receives the outputs of the division circuit 20 and the multiplication circuit 38, respectively, and derives and outputs the following equation (31) (however, v _{m + 2} −2v _m + V _m-2 ≠ 0, cos2β-1 ≠ 0).

The multiplier circuit 40 receives the output of the multiplier circuit 36 as an input, and outputs (32)
The formula is derived and output.

2i _{m + 1} v _{m + 1} = I _p V _p {cos θ−cos (2α + 2β + θ)} (32) Further, the subtraction circuit 41 receives the outputs of the multiplication circuits 39 and 40 as inputs, and uses the following equation (33). Is derived and output (however,
v _{m + 2} −2v _m + v _m-2 ≠ 0, cos2β−1 ≠ 0).

Finally, the calculation result of the subtraction circuit 41 is output to the determination amount deriving unit 22 to obtain the power direction component (26) (where v _{m + 2} −
2v _m + v _m-2 ≠ 0).

When the denominator becomes zero, the same processing as that described in the embodiment of FIG. 1 is necessary.

As described above, the gist of the present invention is to obtain the sampling values of current and voltage, and use the required circuits to calculate the subtraction equations on the right side of equations (19), (26), (33), It is to derive the judgment amount. That is, one of the subtraction expressions is composed of fractional expressions, and I _p V _p {cos θ−cos (2α−θ)} is calculated with the first term as the first electric quantity.

Also, the second term is the second quantity of electricity, Is derived (provided that cos2β-1 ≠ 0). The above-mentioned calculation formula is designed to remove the second harmonic of the calculation result and regulate the acquisition of the sampling data of the current and the voltage so as to calculate the amount related to the amplitude value of the phase difference between the voltage and the current. Then, the subtraction-type operation determines whether or not the power direction component 2I _p V _p cos θ obtained by subtracting the second amount of electricity from the first amount of electricity is greater than zero according to the determination criterion, and the protection relay's I'm trying to get the output.

The modifications of the above embodiment can be roughly classified into two. The first is that, even if m is changed in the equation (19), if the control procedure of the data of the present invention is followed, β of the second equation is
It is possible to obtain the power direction component while keeping cos2β.

Generalizing and substituting m + k (k is an integer) for m in Expression (19), the following expression is obtained.

(However, v _{m + k + 2} −2v _{m + k} + v _{m + k-2} ≠ 0,2V _p sin (α + kβ
+ Θ) (cos2β-1) ≠ 0).

 Expression (19) corresponds to the case of k = 0.

Now, the second is that, even if m is changed in the equation (19), if β of the second equation is set to cos2lβ (l is an integer) according to the data control procedure of the present invention, It is possible to obtain the power direction component.

Although it is generalized and shown by adding 1 to each subscript, it is necessary to make i _m and v _m irrelevant to the subscript l.

(However, v _{m + 2l} −2v _m + v _m-2l ≠ 0, V _p sin (α + θ) (cos2
lβ-1) ≠ 0).

 Expression (19) corresponds to the case of l = 1.

This is because the second equation in equation (19) Was indicated by, and if l, Is obtained.

It goes without saying that these two types of variations are not applicable only to the first embodiment and are applicable to all the embodiments.

In the above explanation, cos2β, or Although the voltage data is used for deriving, the current data may be used, and the effect does not change.

 Specifically, it is as follows.

(However, v _{m + 2} −2v _m + v _m-2 ≠ 0, i _{m + 2} −2i _m + i _m-2 ≠ 0, cos2
β-1 ≠ 0).

(However, v _{m + 2} + 2v _m + v _m-2 ≠ 0, i _{m + 2} −2i _m + i _m-2 ≠ 0, cos2
β + 1 ≠ 0).

It is also possible to use cos2β as follows. As an example (3
Shown in case of equation 8).

(However, v _m ≠ 0, i _m ≠ 0, i _{m + 1} v _{m + 1} −i _m-1 v _m-1 ≠ 0).

 This is clear from the equation (39) below.

(However, i _{m + 1} v _{m + 1} −i _m-1 v _m-1 ≠ 0, sin (2α + θ) sin2
β ≠ 0).

As described with reference to FIG. 1, in the above-described embodiment, as in the case of the conventional relay, "if the sine wave has an invariable frequency, the sampling time width β is set to an electrical angle of 30 ° and three samples before (or
If the latter data is used, that data is 90 ° before (or after) the current data, and if the former is the sine component, the latter is the cosine component. ]
In order to use the calculation principle that does not depend on the premise of (1), the means for prescribing how to take in the input data is shown.

Therefore, according to the present invention, the sampling time width β
Can be set independently of the system frequency, so that the sampling time width β can be shared at 50Hz and 60Hz, and the more the processing device capacity improves, the more the sampling time width β Can be set short.

Specifically, in order to obtain a solution as a power direction relay in the present invention, 5 sample data from m−2 to m + 2 (4 sample data from m to m + 3 in the conventional relay) are used, and the sampling time width β is If shortened, it will be possible to operate at higher speed than conventional relays.

Furthermore, during this 5 sample data, if the frequency fluctuation is such that the frequency of the system can be regarded as almost constant, that is, it is also applied to protection until the hydropower generator starts up to the rated frequency. It is possible.

Further, in the case of the present invention, timed cooperation becomes easier than that of the conventional relay.

That is, in the conventional relay, the tap value, the suppression spring, the contact interval, etc. are used for timed coordination from the power source end to the load end. However, in the present invention, the sampling time width β is shorter on the load side and is closer to the power source end. If β is set to be long, almost the same current will flow through each end toward the accident point in the event of an accident, so relays of the same principle can reliably perform timed coordination.

At this time, if consideration is also given to increase the number of collations of the calculation results toward the current end side, the reliability can be improved.

Further, the idea of the present invention may be applied to an impedance relay, and has the same effect as the above embodiment.

〔The invention's effect〕

As described above, according to the present invention, the first and second electric quantities are obtained by the four arithmetic circuits that satisfy the required relational expressions by using the sampling values of the current and the voltage, and the second electric quantity is calculated from the first electric quantity. Since the circuit is configured to judge whether the power direction component obtained by subtracting with the amount is greater than zero, stable characteristics can be obtained even with frequency fluctuations, and it is possible to use a relay that shares 50Hz and 60Hz sampling time widths. There are effects that can be achieved. Also,
Since the time coordination is excellent, a relay capable of operating at high speed is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a protection relay according to an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing another embodiment of the present invention, and FIG. 4 is an algorithm of a conventional power direction relay. FIG. 6 is a waveform diagram illustrating In the figure, 3 to 5 are temporary storage rooms for current data, and 6 to
Reference numeral 10 is a temporary storage room for voltage data, 11 to 21 are four arithmetic circuits, and 22 is a judgment amount deriving unit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A temporary storage room for current data and a temporary storage room for voltage data, which is obtained by sampling and quantizing voltage data and current data obtained by detecting voltage and current of a power system in a predetermined sampling time width. Calculating means for outputting a first electric quantity and a second electric quantity described below by using sampling values of current and voltage stored in the temporary storage chamber, and a first electric quantity described below as a second electric quantity. A protective relay having a determination amount derivation unit that determines whether the following power direction component obtained by dividing by is greater than zero and outputs the result. Note First electric quantity I _P V _P {cos θ−cos (2α + θ) Second electric quantity Power direction component 2 I _P V _P cos θ where I _P : Current amplitude value V _P : Voltage amplitude value α: ω ₀ t β at sampling m time point: Sampling time (interval) width θ: Phase difference between voltage and current