JPH0363299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protective relay that uses a digital computer to determine the operating state of a power system and protect equipment.

[Conventional technology]

FIG. 4 is a principle diagram showing a protective relay device disclosed in, for example, Japanese Unexamined Patent Publication No. 55-23779. In the figure, 21 is a rectifying and smoothing element that rectifies and smoothes the amount of current in the system, and 22 is a rectifying and smoothing element for rectifying and smoothing the amount of current in the system. 23 is a scalar addition element that adds each rectified and smoothed current amount, 24
25 is a rectification and smoothing element that rectifies and smoothes the vector addition amount, 25 is a comparison judgment element that compares and judges the vector addition amount (operation amount) and the scalar addition amount (suppression amount), and 26 is an output that outputs the above judgment result. is an element.

Next, the principle of operation shown in FIG. 4 is shown using equations (1) and (2).

‖ 〓 ⁱ Ii ^t ‖≧K ₁ × ( 〓 ⁱ Ii ^t ‖)＋K ₀ ……(1) (‖I ^t ‖=｜I ^t ｜+｜I ^t-3 ｜+K ₂ ×｜｜I ^t ｜− |I ^t-3 | |) ...(2) Here, Ii ^t is the amount of current sampled at time t, and the subscript i is the terminal number. Further, 〓 ⁱ Ii ^t means vector addition, ‖I ^t ‖ means rectification smoothing, Σ‖Ii ^t ‖ means scalar addition, and K ₀ , K ₁ , and K ₂ are constants.
Further, in the above example, the sampling frequency is set to 12 times the system frequency (30° sampling).

Next, the operation shown in FIG. 4 will be explained. In other words, the amount of current in each sampled power system
Ii ^t is rectified and smoothed by the rectification and smoothing element 21 as shown in equation (2) to become ‖I ^t ‖, and the scalar addition element 23
is scalar-added to become Σ‖Ii ^t‖ . In addition, each of the current amounts Ii ^t is the vector addition element 22
The vectors are added by , and further rectified and smoothed by the rectification and smoothing element 24, resulting in 〓 ⁱ ‖Ii ^t ‖. In the comparison/judgment element 25, the output 〓 ⁱ ‖Ii ^t ‖ of the scalar addition element 23 is multiplied by an appropriate constant, and together with the output 〓 ⁱ Ii ^t ‖ of the rectification and smoothing element 24 , the judgment of equation (1) is performed. . As a result, if equation (1) is established, an operation signal is output from the comparison/judgment element 25. The output element 26 gives the operation signal an appropriate time limit and outputs it as a final operation output signal.

In the above equation, K ₀ in equation (1) is the minimum operating value,
Since we are trying to obtain the differential characteristics shown by the solid line A in the operating characteristics of a general differential protective relay in Figure 5 by comparing K ₁ with Since variations occur in the characteristics, it is necessary to perform rectification and smoothing calculations as shown in equation (2), for example. This(2)
By calculating the formula, it becomes a form similar to four-phase rectification, and the operating value error can be reduced, and variations in differential characteristics due to the sampling phase can be reduced.

[Problem that the invention seeks to solve]

Conventional protective relays are configured as described above, so when handling multi-terminal information such as applying to bus bar protection, it takes a huge amount of time to process equation (2), resulting in CT saturation. In order to avoid malfunctions due to
It was necessary to change K ₀ , K ₁ , etc. Therefore, there were problems such as severe restrictions on operating time and processing capacity of the digital computer.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a protective relay that is easy to process, responds quickly, and operates stably even when CT is saturated. do.

[Means to resolve the problem]

The protective relay according to the present invention uses the principle equation (3) below, and the output of the first comparison judgment element that judges the equation (3) and the output of the second comparison judgment element that judges the equation (4). The arithmetic circuit is configured to output the final output by inputting this into the inhibit element.

Max( Max ⁱ | Ii ^t |, Max ⁱ | Ii ^t-tb |)−m ₀ ×Max( | 〓 ⁱ Ii ^t |, | 〓 ⁱ Ii ^t-ta |)≧0 ……(3) ‖ 〓 ⁱ Ii ^t ‖≧K ₀ ...(4) However, m ₀ and K ₀ are constants, and Ii ^t-ta and Ii ^t-tb represent the current sample amounts before time t _a and t _b , respectively. Hereinafter, the first comparison and determination element will be referred to as a ratio lock element, and the second comparison and determination element will be referred to as a differential element.

[Effect]

By using this principle equation, it becomes possible in principle to perform judgment calculations on the ratio lock element (first comparison judgment element) using the instantaneous value of the current in the system.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. 1, 1 is a vector addition element that takes in current amounts from multiple systems and adds the vectors, 2 is a rectification element that rectifies the vector addition amount added to the vector addition element 1, and 3 is a rectification element 2. 4 is the vector addition amount at the current time, which is vector added to the vector addition element 1, and the vector addition at a predetermined time before stored in the first storage element 3. A first maximum value derivation element that compares the amounts and derives the larger one (differential amount), 5 is a rectifier element that rectifies the amount of current taken in from multiple systems, and 6 is each rectifier rectified by the rectifier element 5. A second maximum value deriving element that derives the largest current amount among the current amounts; 7 a second storage element that stores the maximum current amount derived to the second maximum value deriving element 6; 8 a second maximum value deriving element 6; A third step that compares the maximum current amount at the current time derived by the maximum value deriving element 6 with the maximum current amount before a predetermined time stored in the second storage element 7 and derives the larger one (suppression amount). Maximum value derivation element, 9
is a first determination element that determines the magnitude relationship between the vector addition amount derived to the first maximum value derivation element 4 and the maximum current amount derived to the third maximum value derivation element 8; 10 is a vector addition element an effective value calculation element that calculates a sum of squares by inputting the vector addition amount at the current time that has been vector added to 1 and the vector addition amount at a predetermined time before stored in the first storage element 3;
Reference numeral 11 denotes a second determination element that determines the magnitude relationship between the calculated value calculated by the effective value calculation element 10 and a predetermined reference value, and 12 determines that the vector addition amount is larger than the first determination element 9. and 13 is a ratio lock element (first comparison judgment) that makes a judgment based on the principle formula (3). element), 14 is a differential element (second comparison/determination element) that makes a determination based on principle formula (4).

Next, the operation shown in FIG. 1 will be explained. First, when the block diagram of FIG. 1 is programmed using a digital computer, it can be expressed as the flowchart of FIG. 2.

That is, in step 1, the vector addition amount E _D ^t of the current amount Ii ^t of each system sampled and quantized at time t is calculated using the vector addition element 1,
In step 2, the second maximum value deriving element 6 calculates the maximum absolute value E _R ^t of each of the current amounts Ii ^t . Next ^, in step 3, the maximum value E _D ^t (differential amount) of the vector addition amount E D t and the vector addition amount _{E D} ^t-ta before the time t _a is calculated by the first maximum value deriving element 4, In step 4, the maximum value E _R ^t calculated in step 2 and
Maximum value E _R before time t _b Maximum value E _R ′ ^t of ^t-tb (amount of suppression)
is calculated by the third maximum value derivation element 8, and step 5
The differential amount E _D ′ ^t is multiplied by m ₀ and compared with the suppression amount E _R ′ ^t . If the latter is larger or equal, the ratio locking element 13 is set to operate. In other cases, the first determination element 9 determines that the comparison lock element is inactive. In step 6, the square sum E D ″t of the addition amount E _D ^t of the vector addition element 1 and the vector addition amount E _{D t} ^{−tc before} time t _c is calculated by the effective value calculation element 10, and in step 7 sum of squares
Compare the magnitude relationship between E _D ″ ^t and the constant K0 ² , and if the former is larger or equal, the differential element is activated,
In other cases, the second determination element 11 performs an operation to disable the differential element. In step 8,
Based on the determination results in step 4 and step 7, the comparison lock element 13 is inoperative, and the differential element 1
Only when 4 is an operation, the final output is performed as a comprehensive operation,
In other cases, the inhibit element 12 determines whether to output the final output as total inoperation or total recovery. In addition, step 1, step 2, and step 2
and step 3, step 3 and step 4, and steps 2 to 5 and steps 6 to 7 may be performed in reverse order. Also, if the amount of current Ii ^t in each system changes in a positive wave over time, if t _e is set appropriately,
It is obvious that the sum of squares E _D ″ ^t is the sum of squares of effective values, so the explanation here will be omitted.

When t _b = 90°, (E _D ^t ) ² + (E _D ^t-tb ) ² = |E _D | ² (sin ² ωt+cos ² ωt) = |E _D ² | Also, in Figure 2 Each determination unit can perform verification multiple times (as it is self-explanatory, the explanation will be omitted) as a measure for stabilizing the characteristics.

According to this invention, by determining the solid line A in FIG. 5 using the above-mentioned principle equation (3) and determining the dotted line A in FIG. characteristics are obtained. In addition, since the principle formula (3) is determined only by the ratio of the differential amount E _D ′ ^t and the suppression amount E _R ′ ^t , calculations can be made based on the instantaneous values, and the solid line A is a straight line passing through the origin, so the minimum It has the characteristic that the operating value K ₀ and the ratio m ₀ can be set independently. In addition, if the terminal currents are not in the same phase or out of phase as shown in Figure 3, the residual amount will be instantaneously changed regardless of the operating range.
By compensating for the time domain in which E _R ′ ^t exceeds the vector addition amount E _D ^t (the shaded area in Figure 3) with the stored vector addition amount E _D ^t-ta , this region can be eliminated and the phase characteristics This prevents the operating range from becoming narrower due to instantaneous calculations. Furthermore, in the event of an external fault, when excessive current passes through and the outflow CT becomes saturated, the relevant
The CT secondary current decreases instantaneously and an excessive differential amount appears to occur, but according to this invention, the excessive differential amount that occurs at saturation can be reduced to the maximum amount of stored system current. Since it is canceled by the value E _D ^t-tb , the ratio lock element based on the principle equation (3) does not recover, the locked state continues, and no malfunction occurs.

In addition, in the above embodiment, 2
Although a multiplication-sum operation is used, since it is basically a level judgment, it may be a rectification smoothing operation as shown in equation (2) as explained in the conventional embodiment, or an integral operation as shown in equation (5). The same effects as in the embodiment described above are achieved.

‖ΣIi ^t ‖=Σ｜ΣI _i ｜ ^t-tj =｜ 〓 ⁱ I _i ｜ ^t +｜ 〓 ⁱ I _i ｜ ^t-t1 ＋｜ 〓 ⁱ I _i ｜ ^t-t2 ＋…… ……(5) 〔 [Effects of the Invention] As described above, according to the present invention, since the arithmetic circuit is configured so that calculation and judgment can be made based on the instantaneous value of the system current in principle, rectification and smoothing as in the above-mentioned equation (2) is possible. Since there is no need for computation, the computation time is significantly shortened, the processing load on one digital computer is reduced, and accidents can be handled quickly. In addition, the external accident department
It has the advantage that very stable characteristics can be easily obtained even against CT saturation phenomena.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the operating principle of a protective relay according to an embodiment of the present invention, FIG. 2 is a flowchart of the embodiment of FIG. 1, and FIG. 3 is a diagram of the compensation principle of phase characteristics of the present invention. FIG. 4 is a block diagram of the operating principle of a conventional protective relay, and FIG. 5 is a diagram showing the operating characteristics of a general protective relay. In the figure, 1 is a vector addition element, 2 is a rectification element, 3 is a first storage element, 4 is a first maximum value derivation element, 5 is a rectification element, 6 is a second maximum value derivation element, and 7 is a first maximum value derivation element. 2 is a storage element, 8 is a third maximum value deriving element, 9 is a first judgment element, 10 is an effective value calculation element, 11 is a second judgment element, 12 is an inhibit element, 13 is a ratio lock element (the 1), and 14 is a differential element (second comparison/judgment element).

Claims (1)

[Claims] 1 A vector addition element that takes in current amounts from multiple systems and adds them vectorwise; a first storage element that stores the vector addition amount added to the vector addition element; and a vector addition element that stores the vector addition amount added to the vector addition element; a first maximum value derivation element that compares the amount of vector addition at a time with the amount of vector addition before a predetermined time stored in the first storage element and derives the larger one; and each current taken in from the plurality of systems. a second maximum value derivation element that derives the amount of current with the largest absolute value among the amounts; a second storage element that stores the maximum amount of current derived to the second maximum value derivation element; A third step that compares the maximum current amount at the current time derived by the maximum value deriving element with the maximum current amount before a predetermined time stored in the second storage element and derives the larger one.
a first determination element that determines the magnitude relationship between the maximum value derivation element, the vector addition amount derived to the first maximum value derivation element, and the maximum current amount derived to the third maximum value derivation element; and an effective value calculation element that calculates a sum of squares by inputting the vector addition amount at the current time that has been vector added to the vector addition element and the vector addition amount at a predetermined time before stored in the first storage element. and a second determination element that determines the magnitude relationship between the calculated value calculated by the effective value calculation element and a predetermined reference value, and a second determination element that determines that the vector addition amount is larger than the first determination element. and an inhibiting element that outputs an operational output only when the second determining element is determined to be smaller than the reference value.