JPH0218012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a directional relay, and particularly to a directional relay with simplified protection calculations.

Technical Background and Problems Various types of protective relays are used to protect power systems, but recently, the most recent ones have been introducing system voltage and current, converting them into digital signals, and transmitting them to microcomputers, etc. Due to this, digital directional relays that calculate and determine the direction of the fault point have come into use. An example of the phase characteristic diagram is shown in FIG. This is applied as a ground-fault directional relay that introduces zero-sequence current I ₀ and zero-sequence voltage V ₀ , and creates characteristics A and B using the introduced electrical quantities, current I〓 and voltage V〓. As a result, the polygonal special line shown in FIG. 1 is obtained.

The method for creating characteristic A will be described here, but characteristic B can also be obtained using the same concept. Current I〓,
Let θ be the phase difference of voltage V〓, let be the maximum angle of characteristic A, and let KV〓 be the minimum sensitive voltage. When the phase difference between the vector C〓 which is phased by this KV〓 and the vector D〓 (=I〓−KV〓) obtained from both vectors KV〓 and I〓 becomes 90°, it is considered as an operating output. It is obtained by

That is, the polygonal line characteristic shown in FIG. 1 requires a vector phase shift and needs to be obtained by a combination of two characteristics. These have the disadvantage that they lead to an increase in the computational processing load for the digital directional relay and further increase the capacity of the storage device that stores the program for performing the computations.

Purpose of the Invention The present invention was made for the purpose of solving the above-mentioned drawbacks, and it simplifies the protection calculation algorithm for obtaining relay characteristics, thereby reducing the calculation processing load and the hardware scale. The purpose of this project is to provide a directional relay.

Summary of the Invention The present invention attempts to determine the operation of a directional relay based on the voltage V〓 and current I〓 from the system through arithmetic processing excluding the phase determination step.

Examples of the invention Examples will be described below with reference to the drawings.

Fig. 2 is a block diagram of one embodiment of the directional relay according to the present invention, Fig. 3 is its phase characteristic diagram, Fig. 4 is a flowchart showing the calculation means for determining operation, and Fig. 5 is a characteristic diagram of another embodiment. , FIG. 6 is a characteristic diagram of yet another embodiment, and FIG. 7 is a block diagram of another embodiment of the directional relay.

In FIG. 2, numerals 1 and 2 are input converters into which voltage V and current I from the power system are introduced.
Reference numeral 3 denotes an analog/digital converter, which includes a sample hold circuit (S/H) 3a, a multiplexer (MPX) 3b, and an analog/digital converter (A/D) 3c. 4
is an arithmetic processing unit into which digital signals corresponding to the voltage V〓 and current I〓 converted by the analog-to-digital converter 3 are introduced. The arithmetic processing section 4 is constituted by a microcomputer, etc., and performs a series of digital arithmetic operations to generate an operational output.

Next, a calculation algorithm for obtaining the polygonal line characteristics shown in FIG. 3 will be explained. The characteristics shown in Fig. 3 are expressed by the following equation using the current I〓 and voltage V〓 introduced into the relay.

I〓·V〓−｜KI〓×V〓｜K′｜V〓｜... In the above calculation formula, "." represents an inner product, "x" represents an outer product, and K and K' are constants. If the phase difference between the vectors I〓 and V〓 is θ, the equation can be transformed as follows.

｜I〓｜｜V〓｜cosθ−K｜｜I〓｜｜V〓｜sinθ｜
Dividing both sides of K′V …′ by |V〓|, we get |I〓｜cosθ−K|||I〓｜sinθ｜＞K′ …″ The above equation is the two specific direction components of I〓｜I〓｜ cosθ，｜I〓
｜
sinθ, and represents a characteristic whose operating range is a region where the slope ||I〓|sinθ|/(|I〓|cosθ−K′) is less than or equal to a constant value of 1/K. The inner product calculation, cross product calculation, and amplitude value calculation of the equation can be easily obtained by well-known digital calculations.

FIG. 4 is a flowchart showing the calculation procedure, which will be explained below. First, Step11
At this step, the digital data of the voltage V〓 and current I〓 obtained by the analog-to-digital converter 3 is read. In Step 12, an inner product calculation of voltage V〓 and current I〓 is performed. In the next Step 13, a calculation is performed to find the size of the cross product of KI〓, which is proportional to current I〓, and voltage V〓. Step 14 is the amplitude value of voltage V〓｜V〓｜
K′ |V〓| which is proportional to
A dynamic calculation judgment calculation is performed using the operating condition equation of the equation, and if the equation conditions are satisfied, it is determined that the current vector at the time of the accident is included in the hatched part in Fig. 3, and the operating output is performed in the next Step 16. Derive and return to Step 11 again. The same calculations as above are repeated.

Digital calculations are performed in the arithmetic processing section 4 using the operating condition expressions as described above. It is possible to obtain a directional relay with a polygonal characteristic symmetrical to the voltage vector V shown in Figure 3.

As is clear from the above equation, a single characteristic, that is, a polygonal line characteristic can be obtained by performing only one digital calculation and without performing a phase shift calculation. It goes without saying that by making the constant K variable, the slope of the straight line can be varied, and by making the constant K' variable, the sensitivity can be varied.

Next, another embodiment will be described. In the above explanation, the size of the inner product and outer product of current I〓 and voltage V〓, and the amplitude value of voltage V〓 were used to obtain the polygonal line characteristics, but the desired polygonal line characteristics can also be obtained using the following equation form. characteristics can be obtained.

I〓・V〓≧Max｛｜KI〓×V〓｜, K′｜V〓｜｝ … Here, Max{ } is the larger of ｜KI〓×V〓｜ and K′｜V〓｜ It means to take.

The formula can be transformed as follows.

｜I〓｜｜V〓｜cosθ≧Max｛K｜｜I〓｜｜V〓｜sin
θ
｜,K′｜V〓｜｝ …′ Divide both sides by ｜V〓｜, ｜I〓｜cosθ≧Max｛K｜｜I〓｜sinθ｜,K′｝
…″ ″Equation is two specific direction components of I〓｜I〓｜cosθ,｜I
〓
When K||I〓|sinθ|K', two straight lines passing through the origin 0 with a slope of 1/K or less or -1/K or more give the operating limit range of the current I〓. When K||I〓|sinθ<K', the sensitivity K' has a linear characteristic with the maximum sensitivity angle being 0°. The overall characteristics obtained here are as shown in FIG. This characteristic also allows the desired polygonal line characteristic to be obtained with only one calculation, and eliminates the need for phase shift calculation.

Next, still another embodiment will be described. In each of the above explanations, it is assumed that no phase shift operation is used, but by introducing a single shift operation as follows, it is possible to provide further flexibility in characteristics.

That is, the following formula is used in the same way as the formula using V〓', which is obtained by shifting the phase of V〓 by ∠.

I〓・V〓′−｜KI〓×V〓′｜K′｜V〓′｜ … The formula can be transformed as follows.

｜I〓｜cos(θ−)−K｜｜I〓｜sin(θ−)｜

K'|V〓|...' As a result, the phase characteristics shown in FIG. 6 are obtained. Even in this case, the polygonal line characteristic can be obtained with only one calculation.

In the explanation so far, the right side of the equation is the voltage
Although the calculation has been performed using a quantity proportional to the amplitude value of V〓, amplitude value calculations are often obtained in the form of a quadratic expression, that is, |V〓| ² . For example, in the formula, both sides are squared, (I〓・V〓) ² ≧Max{｜KI〓×V〓｜ ² , (K′｜V〓｜
) ² }
It is clear that the same characteristics as described above can be obtained even when applied to Note that almost the same characteristics can be obtained for the equation .

FIG. 7 is a block diagram of another embodiment of the directional relay according to the present invention.

In the above explanation, the introduced electricity quantity is analog-to-digital converted and then the determination is made by digital calculation, but in this embodiment, the analog determination is made.

In the figure, numerals 5 and 6 are signal generation circuits, of which the signal generation circuit 5 generates a signal a at a specific phase of the input voltage V, for example, when it crosses the zero point, and the signal generation circuit 6 also generates a signal a at a 90° phase from the signal a. signal b
occurs. It has circuits 7 and 8 that hold the magnitude of the input current I according to the timing of generation of these two signals a and b, respectively. Here, the output of the hold circuit 7 becomes |I〓sinθ, and the absolute value deriving circuit 9 at the next stage obtains ||I〓|sinθ|. On the other hand, the output of the hold circuit 8 becomes |I〓|cosθ. Reference numeral 10 denotes a comparator circuit which compares the magnitudes of both inputs and a constant value K' to obtain a final output. For the determination here, for example, the above formula is used. It goes without saying that the determination in the comparator circuit 10 may be performed by digital calculation.

As explained below, according to the present invention, since the calculation processing configuration excludes the phase shift determination step when calculating the operating formula of the directional relay, the protection calculation algorithm can be simplified to obtain the relay characteristics, and Therefore, it is possible to provide a directional relay that not only reduces the computational processing load but also has a small storage capacity in which the computational processing program is stored and has a reduced circuit scale.

[Brief explanation of drawings]

Figure 1 is a phase characteristic diagram of a conventional directional relay, Figure 2 is a phase characteristic diagram of a conventional directional relay.
3 is a phase characteristic diagram, FIG. 4 is a flowchart showing the calculation procedure for operation determination, FIG. 5 is a characteristic diagram of another embodiment, and FIG. The figure shows further characteristic diagrams of other embodiments.
FIG. 7 is a block diagram of another embodiment of the directional relay. DESCRIPTION OF SYMBOLS 1, 2... Input converter, 3... Analog-to-digital converter, 4... Arithmetic processing unit, 5, 6... Signal generation circuit, 7, 8... Hold circuit, 9... Absolute value output circuit, 10... Comparison circuit.

Claims (1)

[Claims] 1. In a directional relay that inputs a voltage V〓 and a current I〓 from a system and processes them through a microcomputer, the inner product and the outer product of both vectors consisting of the voltage V〓 and the current I〓 are calculated. A directional relay characterized in that it responds to the magnitude relationship between the magnitude of the difference and a constant value determined by the amplitude value of the voltage. 2. In a directional relay that inputs the voltage V〓 and current I〓 from the system and processes it through a microcomputer, the size of the inner product of both vectors consisting of voltage V〓 and current I〓, and the size of the outer product of the two vectors A directional relay characterized in that it responds to a magnitude relationship between a fixed value or a constant value depending on a voltage amplitude value, whichever is greater.