JPS6335125A - Distance relay - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Technical Field of the Invention) The present invention relates to a distance relay, and more particularly to a distance relay that measures distance using differential equations.

(Prior Art) In recent years, as the number of cable systems and star converters in power systems has increased, current and voltage waveform distortions in the event of a system fault have tended to become lower order. Conventional distance relays that measure steady-state impedance have had major problems such as a delay in operating speed due to filters and an increase in errors. On the other hand, it is possible to realize a differential equation that holds true even in a transient state during a system fault using a microcomputer (
1) Although the R value and the R value are obtained from the equation, it is necessary to solve simultaneous equations in order to obtain the two unknowns.

That is, at different times tm and tn, vm・1m
The relationship between the voltage and current values in the time width holds true, but if the L and R values are constant within the time being considered, equation (2) can be solved as a simultaneous equation, and (
3) The value and R value are determined as shown in the formula.

As is well known, when a system failure occurs, the L and R values become values that correspond to the system impedance up to the failure point, so it is possible to determine whether the failure point is internal or external based on the result of equation (3).

Here, the differential value j of the current can be determined using 1-ware, but it can also be calculated from the current value using software. - As an example, an approximate equation for obtaining the current differential value is shown in equation (4).

However, L, N, and Kk (k = 0 - N) are constants, and at least KO (0, 140) According to equation (4), the approximation error is zero at at least two frequencies, and the error at the intermediate frequency is Since the values can be made small, it becomes possible to calculate the L and R values using approximate expressions over a wide frequency range.

Note that in equation (4), the differential value Jm is obtained as the sum of the current differential values of time widths and tm-1 that differ by one sampling time, so the equations for calculating the L and R values are modified as follows. That is, if we set the equation (2) here, the L value and the R value can be obtained from the following equation (7).

FIG. 2 is a diagram showing the hardware configuration of a conventional distance relay that performs the above calculation. In Figure 2, 1 is the power transmission line to be protected, 2 is the transformer, 3 is the current transformer, 4 is the converter, 5 is the input converter, 6 is the analog/differential conversion circuit (VD conversion circuit), and 7 is the This is an arithmetic processing section. In this case, the system voltage is introduced via a transformer 2, converted to an appropriate voltage level by an input converter 4, and then passed through a prefilter to obtain an output V.

Similarly, the system current is introduced via a current transformer 3 and passes through an input converter 5 to obtain an output l. And both output beam conversion circuit 6
The signals are simultaneously sampled at regular intervals, sequentially converted into digital quantities, and manually input to the arithmetic processing section 7 consisting of a microcomputer.

FIG. 3 is a functional block diagram showing the processing contents in the arithmetic processing section 7. As shown in FIG. In FIG. 3, reference numeral 8 denotes a current differential calculation means that calculates the current differential amount J from the input current data, for example, as shown in equation (4) above. Reference numeral 9 denotes a current calculation means, and reference numeral 10 denotes a voltage calculation means, which respectively perform the calculations shown in equation (6) to obtain the current ijI and the voltage amount V. 11 is a denominator value calculation means of the R value calculation formula shown in equation (7), and the denominator value Um=
ImJn-JnJrT+ is obtained. 12 is a numerator value calculation means in the L value calculation formula of equation (7), and the numerator value tm=I
Similarly, 13 is the numerator value calculation means in the R value calculation formula, and the numerator value rm=VmJn-Vn
Get Jm. Reference numeral 14 denotes an L value calculation means that calculates the L value by dividing the denominator value U and the numerator value t of the L value. 1
Reference numeral 5 denotes an R value calculation means, which similarly calculates the R value by dividing the denominator value U and the numerator value r of the R value. These calculated values and R values are introduced into the relay operation determining section 16 to perform operation determination according to the characteristics of the distance relay, and output the results.

(Problems to be Solved by the Invention) The above method is based on a differential equation that holds true even in a transient state during a system fault, so it is not affected by the frequency of current or voltage in principle. However, when an approximation formula is used to calculate the current component value, it may be affected by the degree of approximation, but by using the fourth formula, within the frequency range where the approximation holds true.

It is possible to calculate the value of R with high precision, and it can contribute to improving the frequency characteristics of the distance relay. In this distance relay, the denominator value Um is, when n = m-1, Um = xmrm-1-Im-, Jm-...(8)-K
. It becomes R. Here, if ωT〈π, then Ko will be a constant positive value, but if harmonic components are included, Um will be equal to O. Therefore, the value of R can be calculated from equation (7), or This results in increased instrument errors and quantization errors.

The present invention was made in order to solve the above problems, and an object of the present invention is to provide a stable and reliable distance relay.

[Structure of the invention]

(Means for solving the problem) The configuration for achieving the above object will be explained using FIG. 1 corresponding to the embodiment. It is detected that the output of the first means 11 is below a predetermined level A sixth means 17 is provided to disable the relay output by the output of the sixth means 17.

(Function) Therefore, when Um: 0 occurs due to harmonic components, the relay output becomes invalid due to the output of the sixth means 17, and quantization errors etc. do not increase.

(Example) An example will be described below with reference to the drawings. An embodiment of the present invention will be explained with reference to FIG. The hardware configuration is the same as that shown in FIG. 2, so the explanation will be omitted here.

In FIG. 1, the output U of the denominator value calculation means 11 is an L value,
The signal is input to the R value calculating means and is also introduced to the Um level detecting means 17. The output of this level detection means is NOT
AN with the output of the relay operation determination section 16 via the circuit 18
D is constituted by the circuit 19. Detection of 0m level (
8) From the formula, Um = Im'm-t lm-1Jrr
l=KoIo<K-(9)K may be a constant positive value, and this can be handled by extremely simple means.

In the above embodiment, the output of the Um level detection means was explained by blocking the output of the relay operation determination section, but since it is sufficient that the final output of the distance relay can be blocked, the relay operation determination section or the L value calculation means , the response of the R value calculation means may be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, in a distance relay using a differential equation, errors caused by the main current transformer, main transformer, input converter, etc., and quantum errors occurring during analog/digital conversion can be avoided. This prevents unnecessary response of the distance relay during the single-phase or two-phase restart no-voltage confirmation time when line PT is applied, as it prevents excessive amplification of conversion errors, etc., and prevents unnecessary response of the distance relay using the calculation results based on the current value. It is possible to provide an extremely effective function without accidentally blocking the response of the distance relay in the event of an actual near-end accident.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of a distance relay according to the present invention, FIG. 2 is a block diagram of a general Dinotal relay, and FIG. 3 is a functional block diagram of a conventional distance relay. 1...Power transmission line 2...Transformer 3...
Current transformer 4, 5... Human power converter 6...
A/D conversion circuit 7... Arithmetic processing unit 8... Differential calculation means 9... Current calculation means 10... Voltage calculation means 11... Denominator value calculation means 12.13...
-Numerator value calculation means 14...L value calculation means 15...R value calculation means 1
6...Relay operation determination section 17...Level detection means 18...NOT circuit 19
...AND circuit agent Patent attorney Nori Chika Trust
Hiroshi Mitsumata Figure 2

Claims (1)

[Claims] Input the voltage signal and current signal of the power system, obtain the voltage measurement, current value i, and current differential amount j, and calculate the relational expression v that holds between each of the above electrical quantities and the inductance L and resistance R of the power system. =R_i+L_j and at different times t_m
and a first means for obtaining an electrical quantity i_mj_n−i_nj_m from the voltage quantities v_m, v_n, current quantities i_m, i_n, and current differential quantities j_m, j_n at t_n;
A second means of obtaining _mv_n−i_nv_m and j_
A third means for obtaining mv_n−j_nv_m is provided, and the distance is measured by a fourth means for calculating the inductance L_m and a fifth means for calculating the resistance R_m using the quantity of electricity from each of these means. A distance relay comprising: a sixth means for detecting that the output of the first means is below a predetermined level; and the output of the sixth means disables the relay output.