JPH0222603B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention converts analog input regarding voltage and current read from the power system into digital data, performs arithmetic processing based on a predetermined arithmetic algorithm, and generates power. This invention relates to a digital protection relay device that performs protection relay control of a power system.

[Conventional technology] Digital protective relay devices process digital data using arithmetic algorithms, so compared to analog calculation type protective relays, they improve relay accuracy and characteristics, expand the setting range, and add self-diagnosis functions. etc. are easy. However, the relay arithmetic processing section also performs calculations based on the same judgment formula, and when the setting is low, the bits of the lower digits are used for calculation processing, and when the setting is high, the bits of the higher digits are used, and the bits exceeding the calculation capacity are used. This resulted in an uneconomical and inefficient system for reducing the truncation error for .

FIG. 5 is a block diagram showing an example of the configuration of a conventional digital protective relay device of this type. This digital protection relay device has an analog-to-digital converter 1
1, a relay calculation processing section 12, a setting operation section 13, and an output processing section 15, and operates as, for example, a reactance type distance relay according to a calculation algorithm. Therefore, analog input regarding current and voltage is read from a transformer (not shown) connected to the power system, and the analog-to-digital converter 11 converts it into digital data. For example, as shown in FIG. 2, the analog-to-digital converter 11 converts the current analog input i into times t ₁ , t ₂ , ... t _o of a constant period φ.
and digital data i ₀ , i ₁ ,...i _o
Convert to At this time, digital data i ₀ , i ₁ ,
...i _o can be expressed as i ₀ =Isin ωto...(1) i ₁ =Isin(ωto+φ)...(2) 〓 i _o =Isin(ωto+nφ)...(3). Here, I is the amplitude value of current i, and ω is the angular frequency. Normally, the period φ is about 30 degrees in electrical angle, so the analog input i
The sampling rate per cycle is 12 points.
Similarly, the analog-to-digital converter 11 samples the analog input V regarding voltage read from the power system via the voltage transformer, and converts it into digital data V ₀ , V ₁ , . . . , _Vo . Next, as shown in FIG. 3, the relay arithmetic processing unit 12 calculates the inner product of the vector (Kij-Vj _-3 ) and the vector i _j-3 , and determines whether the straight line A is inside or outside based on the positive or negative result. do. That is, (K·i _j -V _j-3 )i _j-3 > = <0...(4) is performed and the drive output signal of the relay is supplied to the output processing section 15 . However, in equation (4), K is a constant determined by the settling impedance, and j is j
= 0, 1, ..., n, and when the left side of equation (4) is positive, it is in the operating region below straight line A in Figure 3, and when it is negative, it is in the operating region above straight line A. The basic functions of a reactance type distance relay can be obtained by the relay arithmetic processing unit 12 determining that the relay is in the operating region.

[Problems to be Solved by the Invention] However, when actually constructing a reactance type distance relay using a digital protective relay device, the straight line A fluctuates within the shaded area in Fig. 4 due to the expansion of the truncation error during arithmetic processing. , the percentage of errors is particularly large in low current and low settling regions. In general, this type of reactance type distance relay requires a wide range of operating conditions, such as a setting impedance range of 0.1 to 100 (Ω).
When applied to the equation, the constant K changes by a factor of 1000. Therefore, in order to perform calculations in the same relay calculation processing section 12 from low setting to high setting, as long as the determination by equation (4) is made, the relay calculation processing section 1 is used at low setting.
2 low bits are used for high settings, and high bits are used for high settings, resulting in an uneconomical and inefficient system.

Therefore, in order to eliminate such drawbacks, the present invention introduces an arithmetic operation in which the judgment formula is multiplied by a correction term that depends on the size of the set value, thereby optimizing the number of bits required for arithmetic processing. Therefore, it is an object of the present invention to provide a highly accurate digital protective relay device.

[Means for Solving the Problems] In order to solve such problems, the digital protection relay device of the present invention includes: an analog-to-digital converter that converts analog input read from the power system into digital data; and a set value. _{and a} ^setting operation section that _sets the digital data as follows: digital data related to the analog input current v: digital data related to the analog input voltage j: 1, 2,...n]; and a relay calculation processing unit that calculates the correction constants K' and S according to the set value. The present invention is characterized in that it includes a correction term calculation section that performs the following steps.

[Example] Next, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, parts having the same functions as those in FIG. 5 are given the same reference numerals.
Therefore, the embodiment of the present invention shown in FIG.
The difference from the conventional example shown in the figure is that a correction term calculation unit 14 is provided. In the present invention, based on the setting operation of the setting operation section 13,
It depends on the size of the setting value so that the relay calculation process is executed using the judgment formula (K′・i _j −V _j-3 )×2 ^-s ×i _j-3 ＞ = <0...(5) The correction constants K' and S are configured so that the correction term calculation unit 14 determines them. In this way, the correction constant K',
As shown in equation (5), the size of the vector (K'・i _j ^−V _j-3 ) is limited by the correction constant K′, and the vector is Limit the size of the inner product (K′・i _j −V _j-3 )・i _j-3 . In particular, when the setting is low, the value of the correction constant S can be made small to prevent an increase in the truncation error during arithmetic processing, and when the setting is high, the value can be increased to prevent an increase in the number of calculation bits. Note that the present invention is applicable not only to reactance type distance relays but also to other digital calculation type protective relays.

[Effects of the Invention] As described above, according to the present invention, by adding a correction term according to the set value, the influence of truncation errors during calculation processing in the relay calculation processing section is reduced, and the calculation capacity is increased. Even if it is limited, it is possible to optimize the number of bits required for arithmetic processing, have a wide setting range, and realize various types of highly accurate digital calculation type protective relays by using a digital protective relay device.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a configuration example of a digital protective relay device according to the present invention, Fig. 2 is a signal waveform diagram for explaining the operation of the analog-to-digital converter, and Figs. 3 and 4 are reactance diagrams. FIG. 5 is a block diagram showing a conventional digital protection relay device. 11... is an analog-to-digital converter, 12...
Relay calculation processing section, 13... Setting operation section, 14...
...Correction term calculation unit, 15...Output processing unit.

Claims (1)

[Scope of Claims] 1. An analog-to-digital conversion unit that converts analog input read from the power system into digital data, a setting operation unit that sets a setting value, and converts the digital data into the following determination formula (K′・i _j − v _j-3 )×2 ^-s ×i _j-3 ＞ = <0 [K', S: Correction constant i: Digital data regarding analog input current v: Digital data regarding analog input voltage j: 1, 2,...n ] A digital protective relay device comprising: a relay calculation processing section that performs calculation processing based on the following; and a correction term calculation section that calculates the correction constants K' and S according to the set value.