JP2688276B2 - Protective relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

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

[Prior art]

FIG. 2 illustrates the algorithm of the digital operation type power direction relay shown in the product C, for example, the method of Table 4-1-3 of "Electrical Cooperation Research, Vol. 41, No. 4 Digital Relay" P45. FIG. As a calculation principle formula for obtaining the electric power direction, formula (1) is shown in the above table. V · I cos θ = v _m i _m + v _m-3 i _m-3 (1) However, V, I; voltage and current amplitude value θ; voltage and current phase difference i _m , v _m ; time Sampling of current and voltage at m
Data i _m-3 , v _m-3 ; Sampling data of current and voltage 3 samples before time m Furthermore, here, the sampling time width β is 30 in electrical angle.
In this case, the sum of the inner product value of the current and voltage at the time m and the inner product value at a time 90 ° apart from the time m is obtained. Now, as shown in FIG. 2, the amount of electricity input to the relay is: i (t) = I _p sin (ω _o t) …… (2) v (t) = V _p sin (ω _o t + θ) …… (3) and assuming that the value of ω _o t at time m is α, each sample value is given by equations (4) and (5). i _m = I _p sin α (4) v _m = V _p sin (α + θ) (5) Further, the sample value at the time of mk is expressed by the formula (6).
Given by (7). i _mk = I _p sin (α-k β) (6) v _mk = V _p sin (α-k β + θ) (7) where I _p , V _p ; current and voltage amplitude value, θ; The phase difference between current and voltage, k; k = 1.2.3 .... Here, focusing on the right side of Expression (1), the following is found. 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 {sinαsin (α + θ) + cosα cos (α + θ)} = I P V P cosθ ...... (8) i.e., 3 samples of separation of data, the electrical angle It's a 90 ° gap.

[Problems to be solved by the invention]

Since the conventional protective relay is configured as described above, "The system frequency is always constant, and in order to be established as a digital relay, the sampling time width β must be accurate for frequencies such as 50Hz and 60Hz. Need to be specified in. The principle of operation is constructed based on the premise. Therefore, for the frequency fluctuation of the system, sin (α-3β) sin (α-3β + θ)} = cosαcos in equation (8)
The premise of (α + θ) is broken and the equal sign is not established, which is affected by the calculation principle that cannot be ignored in terms of protection ability. In addition, unless the sampling time width β is changed depending on the frequency, the error becomes large and it is practical. There was a problem that it disappeared. 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 in the case of 60Hz, 5ms in the case of 50Hz) is required (the processing time of the processing device is neglected), and in the conventional calculation principle, It is difficult to further shorten the detection time, and there is a problem 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 Problems]

A protective relay according to the present invention is a temporary storage room for current data and a temporary storage room for voltage data in which current data and voltage data obtained by detecting current and voltage of a power system are sampled with a predetermined sampling time width, quantized, and temporarily stored. Of the current and voltage data stored in the temporary storage room of the temporary storage room and the calculation order of the sampling value and the calculation order of the voltage data, and the first electric quantity and the second electric quantity
Of the four sampling arithmetic circuits for arithmetically processing and outputting the electric quantity and the first sampling arithmetic expression whose product quantity is the product of the electric power amplitude value and the voltage amplitude value to the fourth power. The first electric quantity is divided by the second electric quantity consisting of the second sampling arithmetic expression in which the cube of the voltage swing value is divided to obtain the electric power direction component, and the electric power direction component is larger than zero. A determination amount deriving unit for determining whether or not and outputting the determination result is provided.

[Operation]

The protective relay according to the present invention derives a product quantity of current and voltage sampling data of a power system to obtain a first electric quantity and a second electric quantity, obtains a power direction component from the electric quantity, and determines a criterion. Judge in light of. Then, sampling is performed among the three components of the electric quantity, namely, the component related to the phase difference (θ) between the current and the voltage, the related component of the second harmonic (2α), and the component related to the sampling time width (β). Since the components related to the time width and the second harmonic are removed from the phase difference component and only the components related to the phase difference of the current and voltage are defined, the order of capturing the input sampling data is specified.
High precision and stable against frequency fluctuations, 50 ^HZ , 60 ^HZ
A relay with a common sampling time width can be obtained.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a distribution path for digitized current data, 2 is a distribution path for voltage data, 3 and 4 are temporary storage rooms for current data, 5 to 9 are temporary storage rooms for voltage data, and 10 is a storage room. , 13,15,16,18 are addition circuits, 19,25 are subtraction circuits, 11,
12, 14, 17, 20, 20, 21, 26 and 28 are multiplication circuits, 22 to 24 and 27 are division circuits, and 29 is a determination amount derivation unit. Next, the operation will be described. First, in the distribution paths 1 and 2 for the current and voltage data, digital data strings ... i _m-1
... i _{m + 1} ... and ... v _m-2 , v _{m-1 ,,} v _m , v _m1,, v _{m + 2} are always constant sampling time width β (in the present invention, like the conventional digital relay, Depending on the system frequency, electrical angle 30
It is not necessary to specify the degree or its multiples. ), The current and voltage data are temporarily stored in the temporary storage chambers 3, 4, 5-9, i _m-1 , i _{m + 1} ; v _m-2 , v _m-1 , v, respectively. It is assumed that _m , v _{m + 1} v _{m + 2} are stored. The loading / unloading of the data in / from the temporary storage rooms 3 to 9 is controlled by another control system (not shown). For example, when the latest data, i _{m + 3} , appears in the data distribution path (of course, v _{m + 3} also appears in the data distribution path 2 in synchronization with this). Temporary storage room for current data At 4, the data i _{m + 1} is cleared and the next data i _{m + 2} is stored. In the temporary storage room 3 for the current data, the data i _m-1 is cleared and the data i _m is cleared. At this time, the control of clearing and storing the data of the current data in the temporary storage rooms 3 and 4 is also controlled by another control system. The operations of the temporary storage rooms 5 to 9 for voltage data are exactly the same as those of the temporary storage room for current data. That is, in the voltage data temporary storage room 9, v _{m + 3} , 8
_{V m + 2, v m +} 1 is the same 7, the same 6 v _m, vi _m-1 in the same 5 are respectively housed in. Therefore, the adder circuit 10 has a temporary storage room for current data.
The outputs from 3 and 4 are input, and the equation (9) is derived and output. i _{m + 1} i _m-1 = I _p sin (α + β) + I _p sin (α−β) = 2I _p cos α · cos β (9) Further, in the multiplication circuit 11, the current data temporary storage room 3
And the output of the voltage data from the temporary storage room 6 are respectively input, and the formula (10) is derived and output, In the multiplication circuit 12, the outputs from the temporary storage room 4 for the current data and the temporary storage room 8 for the voltage data are input,
Equation (11) is derived and output. Next, in the adder circuit 13, the voltage data temporary storage room 6,
Input the outputs from 8 respectively, derive the formula (12) and output it. V _{m + 1} v _m-1 = V _p sin (α + β + θ) + V _p sin (α-β + θ ) = 2V _p sin (α + θ) cos β (12) In the multiplication circuit 14, the output of the voltage data from the temporary storage room 7 is input and 2V _m is derived and output. Further, in the adding circuit 15, the voltage data temporary storage room 5,
Input each output from 9 and derive and output Equation (13), v _{m + 2} v _m-2 = V _p sin (α + 2β + θ) + V _p sin (α-2β + θ) = 2V _p sin (α + θ) cos2β (13) In the adder circuit 16, the outputs from the multiplier circuits 11 and 12 are input, and the formula (14) is derived and output. Further, in the multiplication circuit 17, the outputs from the addition circuits 10 and 13 are respectively input, and the equation (15) is derived and output, and (i _{m + 1} i _m-1 ) (v _{m + 1} v _{m- 1} ) = 2I _p sin αcos β · 2V _p sin (α + θ) cos β = I _p V _p (1 + cos2β) {cos θ-cos (2α + θ)} (15) In the adder circuit 18, the output from the multiplier circuit 14 and the adder circuit 15 , Respectively, and formula (16) is derived and output. v _{m + 2} + v _m-2 + 2v _m = 2V _p sin (α + θ) cos2β + 2V _p sin (α + θ) = 2V _p sin (α + θ) (cos2β + 1) (16) In addition circuit 19, multiplication circuit 14 and addition circuit 15 (17) is derived and output, and v _{m + 2} + v _m-2 −2v _m = 2V _p sin (α + θ) cos2β−2V _P sin (α + θ) = 2V _P sin (Α + θ) (cos2β-1) (17) In the division circuit 22, the outputs from the division circuit 14 and the addition circuit 15 are input, and the equation (18) is derived and output (however, v _{m +2} + v _m-2 ≠ 0, V _p cos2 β ≠ 0, V _p sin (α + θ) ≠ 0
And). Also. In the multiplication circuit 21, the outputs from the addition circuit 16 and the division circuit 22 are input, and the equation (19) is derived and output (however, v _{m + 2} + v _m-2 ≠ 0, V _p sin ( α + θ) ≠ 0, V _p cos2β
≠ 0. ), In the division circuit 23, the outputs from the multiplication circuit 14 and the addition circuit 18 are input respectively, and the equation (20) is calculated and derived (however, v _{m + 2} + 2v _m + v _m-2 ≠ 0, V _p sin (Α + θ) ≠ 0, V _p (cos2
β + 1) ≠ 0). In the multiplication circuit 20, the outputs from the multiplication circuit 17 and the division circuit 23 are input, and the equation (21) is calculated and output (however, V _p
(Cos2β + 1) ≠ 0. ), In the division circuit 24, the outputs from the multiplication circuit 14 and the subtraction circuit 19 are respectively input, and the formula (22) is derived and output (however, v _{m + 2} −2v _m + v _m-2 ≠ 0, V _p sin (α + θ) ≠ 0, V
_p (cos2β-1) ≠ 0). Then, in the division circuit 27, the multiplication circuit 14 and the addition circuit 15
(23) is derived by inputting the output from each of the above, and is output (provided that v _m ≠ 0, V _p sin (α + θ) ≠ 0), In the subtraction circuit 25, the outputs from the multiplication circuits 20 and 21 are respectively input, and the equation (24) is derived and output (however, v _{m + 2}
＋ 2v _m ＋ v _m-2 ≠ 0, v _{m + 2} ＋ v _m-2 ≠ 0, V _p cos2 β ≠ 0, V _p (cos2
β + 1) ≠ 0). In the multiplication circuit 28, the outputs from the division circuits 24 and 27 are input, and the equation (25) is derived and output (however, (v _{m + 2} −
2v _m + v _m-2 ) v _m ≠ 0, V _p (cos2β-1) ≠ 0), In the multiplication circuit 26, the outputs from the subtraction circuit 25 and the multiplication circuit 28 are input, respectively, to derive the equation (26) and output it (however, (v _{m + 2} −2v _m + v _m−2 ) v _m ≠ 0, v _{m + 2} ＋ 2v _m ＋ v _m-2 ≠
0, v _{m + 2} + v _m-2 ≠ 0, V _p (cos2β-1) ≠ 0, V _p cos2β (cos2
β + 1) ≠ 0). Finally, the determination amount derivation unit 29 derives the power direction component I _P V _P cos θ from the calculation result of the multiplication circuit 26. 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. For the power direction relay, use the formula (26) below as the formula (27).
The condition is determined (not shown). I _P V _P cos θ ≧ 0 (27) Outputs an operation signal as a relay when a positive or zero condition is satisfied in equation (27). The modifications of the above embodiment can be roughly classified into two. According to the control procedure of the data of the present invention, even if m is changed in the formula (26), β of the second formula is
It is possible to obtain the component in the power direction as s2β. Generalizing and substituting m + k (k is an integer) for m in Expression (26), the following expression is obtained. However, (v _{m + k + 2} −2v _{m + k} + v _{m + k-2} ) v _{m + k} ≠ 0, v _{m + k + 2} +2
v _{m + k} + v _{m + k-2} ≠ 0, v _{m + k + 2} ＋ v _{m + k-2} ≠ 0, V _P sin (α + kβ
+ Θ) cos2β ≠ 0, cos2β ± 1 ≠ 0. ) Expression (26) corresponds to the case of k = 0. Now, in the second, even if m is changed in the equation (26), if the second equation β is set to cos2lβ (l is an integer) according to the data control procedure of the present invention, the power direction It is possible to obtain the ingredients. 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 ) v _m ≠ 0, v _{m + 2l} +2 _m + v
_m-2l ≠ 0, v _{m + 2l} + v _m-2l ≠ 0, V _P sin (α + θ) (cos2β +
1) ≠ 0 and cos2lβ-1 ≠ 0. ) Equation (26) corresponds to the case of l = 1. This is because the second equation in equation (26) Was indicated by, and if l, Is obtained. As described above, the gist of the present invention is to obtain a sampling value of current and voltage, calculate the sampling value using a required circuit, and calculate the multiplication expression on the right side of Expression (24) or Expression (31). Is to derive. That is, the division formula of the judgment amount calculation is I _P V _P ⁴ cos with the numerator as the first electric quantity
2β (cos2β-1) (cos2β + 1) cosθ is derived. In addition, V _P ³ cos2β (cos2β-
1) Derive (cos2β + 1). The above-mentioned calculation formula is designed to remove the second harmonic of the calculation result and regulate the acquisition of sampling data of current and voltage so as to derive the amount related to the amplitude value of the phase difference between voltage and current. Then, the operation of the division formula determines whether the power direction component I _P V _P cos θ obtained by dividing the first amount of electricity by the second amount of electricity is greater than zero according to the determination criterion, and protects. I am trying to get the output of the relay. Here, the related terms related to the components of the current and voltage phase differences (θ) and the sampling time width (β) of the first and second electric quantity calculation formulas are referred to as follows. cos2β (cos2β-1) (cos2β + 1) cosθ is the first sampling arithmetic expression, cos2β (cos2β-1) (cos2β +
1) is the second sampling arithmetic expression. Therefore, according to the present invention, the sampling time width β
Can be set independently of the system frequency, so 50Hz, 60Hz
Thus, the sampling time width β can be shared, and the more the processing capacity of the processing device improves, the shorter the sampling time width β can be set. Specifically, in order to obtain a solution as a power direction relay, it is 5 sample data from m-2 to m + 2 (4 sample data from m to m-3 in the conventional relay),
In the case of the present invention, it is possible to set it within an electrical angle of 90 °. That is, high speed operation becomes possible. Furthermore, during this 5 sample data, if the frequency of the system is a frequency fluctuation that can be regarded as almost constant, that is, for protection until the hydropower generator starts up to the rated frequency, etc. Applicable. Another feature of the present invention is that timed cooperation is easier than in conventional relays. That is, in the conventional relay, the time coordinated from the power source end to the load end is taken in hardware by the tap value, the suppression spring, the contact interval, etc., but in the present invention, the sampling time width β is shortened toward the load side, If the sampling time width β is set longer on the power supply end side, in the event of an accident, almost the same current will flow through each end and flow toward the accident point, so that time-based cooperation can be reliably achieved with relays of the same principle. . At this time, in addition, if the consideration is given such as increasing the number of collation of the calculation results toward the power source end side, it also contributes to the improvement of reliability. Furthermore, 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 using the sampling values of the current and the voltage, and the first electric quantity is set to the second electric quantity. Since the circuit is configured to judge whether the power direction component obtained by dividing by the amount of electricity is greater than zero, stable characteristics can be obtained even with frequency fluctuations, and a relay that shares 50Hz and 60Hz sampling time widths. There is an effect that can be done. Also,
It is effective in obtaining a relay that can operate at high speed due to its excellent time coordination.

[Brief description of the drawings]

FIG. 1 is a block diagram of a protection relay according to an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining an algorithm of a conventional power direction relay. In the figure, 3 to 4 are temporary storage rooms for current data, and 5 to 5.
Reference numeral 9 is a temporary storage room for voltage data, 10 to 28 are arithmetic circuits, and 29 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 including: a determination amount derivation unit that determines whether the following power direction component obtained by dividing by is greater than zero and outputs the determination result. Serial first electrical quantity ^{_{I P V P 4 cos2β (cos2β}} -1) (cos2β + 1) cosθ second electrical quantity ^{_{V P 3 cos2β (cos2β-1}} ) (cos2β + 1) , where the power direction component I _P V _P cosθ, I _P : Amplitude value of current V _P : Amplitude value of voltage β: Sampling time (interval) width θ: Phase difference between voltage and current