JPS6218919A - Digital distance relay - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a digital distance relay, and particularly to a digital distance relay using a zero-sequence compensation current.

[Technical background of the invention]

In recent power grid failure phenomena, waveform distortion of voltage and current tends to increase, so when applying conventional distance relays that focus on steady state impedance, the operating speed of filters is required to sufficiently remove distortion. The problem is a decrease in distance measurement error and an increase in distance measurement error due to the influence of distortion components. For this type of system, for example, the one shown in Japanese Patent Publication No. 53-31747 has been proposed.

This will be briefly explained below. That is, as a distance measurement method of the protective relay device, a differential equation that is established between the voltage V of the power transmission line, the electric current, the resistance R, and the inductance L is used. Since Equation (1) holds true both in steady state and transient state, by applying a distance measurement method based on Equation (1), it is possible to improve the problem of distance relays with respect to waveform distortion described above. That is,
The distance is measured by determining the inductance L value and resistance R value of equation (1). Since equation (1) has two unknowns, inductance L and resistance R, it is necessary to solve it as simultaneous equations. Here, if the inductance L and resistance R are constant within the time under consideration, the following equation holds true at different times m and n.

By solving this simultaneous equation, inductance L and resistance R
are each expressed as below.

Distance measurement is performed using the L value and R value determined by the above equation (3).

Next, this method will be explained using FIG. 2.

Figure 2 shows the hardware when a distance relay based on differential equations is configured with a digital distance relay applied with a microcomputer. 1 indicates the power transmission line to be protected;
2 is a transformer, 3 is a current transformer, 4 is an input conversion circuit, 5 is an A/
A D conversion circuit (analog/digital conversion circuit), 6 is an arithmetic processing section.

The system voltage is then introduced via the transformer 2, converted to an appropriate voltage level by the input conversion circuit 4, and then passed through a pre-filter to the output voltage and V. etc. In substantially the same way, the grid current is also introduced via the current transformer 3, passes through the input conversion circuit 4, and is output to outputs 1 and 1. etc. Both of these outputs are simultaneously sampled at regular intervals by the A/D conversion circuit 5, sequentially converted into digital quantities, and inputted as voltage data and current data to an arithmetic processing unit 6 such as a microcomputer.

FIG. 3 is a functional block diagram showing the processing contents in the arithmetic processing section 6. As shown in FIG. In FIG. 3, 13 is voltage calculation means;
14 is a current differential calculation means, 15 is a current calculation means, 16 is an L value calculation means, 17 is an R value calculation means, and 18 is a relay operation determination means. Note that the current differential calculation means 14 is a means for calculating a current differential value J from input current data, and similarly, the voltage calculation means 13 and the current calculation means 15 each calculate a voltage value V.

This is a means to obtain the current value ■. The L value calculating means 16 uses the current differential value J1 voltage value v1 current value (■) obtained by each of the above-mentioned calculating means. (3) is a means for calculating the L value i), and the R value calculation means 17 is also a means for calculating the R value from the equation (3). The obtained L value and R value are introduced into the relay operation determination means 18, and the relay operation determination means 18,
The L value and R value are used to determine the operation according to the characteristics of the distance relay, and the output is derived. The above is an explanation of the distance measurement method based on differential equations.

Here, a conventional ground fault distance relay for a parallel two-circuit power transmission line will be explained. In this case, when measuring the distance to a ground fault, there is a known distance measurement error problem due to zero-sequence compensation, which will be described next.

FIG. 4 is a parallel two-circuit system diagram at the time of an a-phase-line ground fault at point F.

In Figure 4, zo is the own line zero-sequence impedance 2, own line positive-sequence impedance z2 is the own line negative-sequence impedance zM is the zero-sequence mutual impedance between lines Ro is the own line zero-sequence current R1 is the own line positive-sequence resistance RM is the zero-sequence mutual resistance between lines, Xo is the own line zero-sequence inductance X, is the own line positive-sequence inductance
The phase current 1.1 is the adjacent line a-phase current lo, and the own line zero-sequence current lo' is the adjacent line zero-sequence current 19, which is the own line relay.

In a parallel two-line power transmission line, when a ground fault occurs, the zero-sequence impedance of the own line 2° and the inter-line zero-sequence mutual impedance zM are affected, so in order to accurately measure the distance to the fault point, it is necessary to As for the input current, the phase current 1& alone is not sufficient υ, and it is necessary to compensate with the zero-sequence current of the own line and the adjacent line.

That is, the voltage v1 at the time of failure at the relay installation point of the A terminal own line relay 19 is expressed by the following equation (4): =Z, (ilL+Kio+'io') -...
...(4) [Problems with background art] Each impedance 2°iZ4. according to the above explanation. Since ZM generally has different angles, K and K' in equation (4) are complex numbers, 4, and therefore should be vector compensated. However, in order to perform vector compensation with a conventional relay, phase shifting means such as an accelerator or the like is required depending on the line constant, which is not practical. Scalar compensation of the relay input current was performed by treating K and N' as real numbers and calculating their product with the zero-sequence current. Therefore, both the resistance component and the reactance component of impedance 2 are compensated using the same compensation coefficient.
There were problems such as (Volume 7, No. 1). The tendency of distance measurement errors of ground fault relays due to this zero-phase compensation is that in cable systems,
It is well known that this is particularly remarkable.

Incidentally, in the above explanation, a parallel two-circuit system diagram has been taken up as the object to be protected, but problems also arise for single-circuit power transmission lines as well.

[Purpose of the invention]

The present invention has been made to solve the above problems, and an object of the present invention is to provide a digital distance relay with improved distance measurement performance in the event of a ground fault.

[Summary of the invention]

In the present invention, the system voltage V, current I, and resistance R.

Differential equation established between inductance L =
Distance relay t that measures distance using L - + RI In electric appliances, when calculating ground fault distance, apply the amount of current that has been compensated for zero phase separately for resistance R and induction 2F 15 minutes. The distance is measured using the following method.

[Basic idea of invention]

First, the main point is to perform zero-phase compensation individually for the resistance R1 and inductance L of the system.

Therefore, the A terminal own circuit relay 19 of the system shown in FIG.
Focusing on this, the fault voltage M1 at the time of a phase-a line ground fault at the relay installation point can be expressed as follows using a differential equation.

However, ia ; ia-1o, :mode amount 1B=1. +KoR1o+KMBio': Resistance 8 minutes zero-phase compensation current 1L=1. +KOLio+KMLiQ'
: inductance L minute zero-phase compensation current L1; own line positive-sequence inductance Lo; own line zero-phase inductance LM; inter-line zero-phase mutual inductance In this way, each constant R and L are each zero-phase compensated, and Compensation current 1L for each of the above constants = 1a + KOL 1o + KMLlo' and l, =
1. 10Koi'o +KMR'O' are respectively obtained, and the voltage calculation values vIam''&n, the current calculation values Rm, IILn, and the current differential values Jt, m' at different times tm and tn are obtained.
JL" and express it according to equation (2), we get the following (6
).

Therefore, by solving the simultaneous equations of equation (6), the inductance L, value, and resistance R1 value become the following equation (7).

The above is the basic idea.

[Embodiments of the invention]

Examples will be described below with reference to the drawings. FIG. 1 is a functional block diagram illustrating an embodiment of a distance relay according to the present invention. Note that the hardware configuration is the same as that in FIG. 2, so a description thereof will be omitted. Also, the same parts as those in FIG. 3 are given the same reference numerals, and the description thereof will be omitted.

In FIG. 1, reference numeral 7 denotes own-line zero-sequence current compensation calculation means (input 2 f 15 minutes), which calculates the own-line zero-sequence current l input.

and zero-sequence compensation coefficient 1j1 for own line inductance R. Ko
Multiply by L and K. Derive Llo.

Reference numeral 8 denotes own line zero-sequence current compensating means (resistance R portion) similar to 7 above, and input own line zero-sequence current 1° and own line resistance 8 minutes zero-sequence compensation coefficient K. Multiply with B to derive KoRlo. In addition, 9 is an adjacent line zero-sequence current compensation operator R (Indeg 2F 15 minutes) which multiplies the inputted adjacent line zero-sequence current 1°' by the adjacent line inductance 5 minutes zero-sequence compensation coefficient KML to obtain KMLlo. ′ is derived. 10 is an adjacent line zero-sequence current compensation calculation means (resistance R portion) similar to 9 described above, and an inputted adjacent line zero-sequence current i. ' is multiplied by the adjacent line resistance 8-minute zero-sequence compensation coefficient KMR to derive KMR1o'.

Reference numeral 11 denotes a zero-phase compensation current calculation means (input 2 times 15 minutes), which receives the input a-phase current 11 and the calculation value K obtained by the calculation means 7. Ll. and the calculated value Kw L 10' obtained by the calculation means 9 are added to obtain the zero-phase compensation current IL.
It is a means of deriving the Reference numeral 12 denotes a zero-phase compensation current calculation means (resistance R portion) similar to the calculation means 11 described above, which calculates the input a-phase current j and the calculation value K obtained by the calculation means 8. Rl
This is means for deriving the zero-phase compensation current IR by adding three values: o and the calculated value KMR1o' obtained by the calculation means 9.

Calculated value (compensation current) obtained by calculation means 11.12
tL and iR are input to the current differential calculation means 14 and the current calculation means 15, respectively, and are further input to the L value calculation means 16 and the R value calculation means 17 together with the amount obtained by the voltage calculation means 13.
is input, and the L value and R value are determined by equation (7). The obtained L value and R value are then introduced into the relay operation determining means 18 to determine the operation.

In the above embodiment, the adjacent line resistance R minute zero-sequence compensation coefficient KMB% adjacent line zero-phase compensation coefficient KML is expressed as KMR=O2K
If ML = 0, the zero-sequence compensation current 1R, iL for the resistance R and inductance L will be the following formula (8), and will be only the own line zero-sequence compensation current or only the zero-sequence compensation of a single transmission line. That is clear.

〔Effect of the invention〕

As explained above, according to the present invention, in a distance relay that measures distance using the differential equation V=Lπ+RI that holds between voltage V, current I, resistance R, and inductance L of a power transmission line, As the amount of current applied to the distance measurement calculation for short circuit failure, the amount of current obtained by separately compensating for the zero phase of each of the resistance R and the inductance L is used, thereby providing a digital distance relay with improved distance measurement performance. can.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram for explaining one embodiment of the distance relay according to the present invention, Fig. 2 is a hardware configuration diagram of a general distance relay, and Fig. 3 shows a distance measurement method based on differential equations. FIG. 4 is a functional block diagram of the conventional arithmetic processing section of the distance relay used, and is a diagram of a parallel two-way power transmission system at the time of an a-phase-line ground fault. 1...Power transmission line, 2...Transformer, 3...
・Current transformer, 4...Input conversion circuit, 5...
・A/D conversion circuit, 6... Arithmetic processing unit, 7...
- Own line zero-phase current compensation calculation time (inductance L)
, 8... Self-line zero-phase current compensation calculation means (resistance R portion),
9... Adjacent line zero-sequence current compensation calculation means (inductance L portion), 10... Adjacent line zero-sequence current compensation calculation means (resistance R portion) 11... Zero-phase compensation current calculation means (in-meta-tough 25 minutes) , 12...Zero phase compensation current calculation means (resistance R portion), 13...Voltage calculation means, 14...Current differential calculation means, 15...Current calculation means, 16...L value calculation means , 17...R value calculation means, 18...Relay operation determination means, 19... Own line relay.

Claims (3)

[Claims] (1) In a distance relay that converts a plurality of electrical quantities from a power system into digital quantities and derives a relay output via a distance measuring means based on a differential equation, the power system is connected to a parallel two-circuit transmission line. , the product value of the zero-sequence current of the line to be protected by the distance relay (hereinafter referred to as the own line) among the parallel two-line transmission line and the zero-sequence compensation coefficient for the own line resistance, The line next to your own line (hereinafter,
a first means for calculating the product value of the zero-sequence current of the adjacent line (referred to as an adjacent line) and a zero-sequence compensation coefficient for the adjacent line resistance, and calculating the sum of the two; A second means for obtaining the resistance component zero-sequence compensation current by calculating the sum of the output from the own line zero-sequence current and the own line inductance component zero-sequence compensation coefficient; A third means for calculating the product of the line inductance and the zero-phase compensation coefficient and calculating the sum of the two; A fourth means for obtaining a phase compensation current, a fifth means for obtaining a differential amount of the current obtained by the fourth means, a voltage amount of the power system, an output from the second means, and the fifth means. a seventh means for determining the inductance of the power transmission line from each output from the power system; and a seventh means for determining the resistance of the power transmission line from the voltage amount of the power system, the output from the second means, and the output from the fifth means. A digital distance relay characterized in that it consists of means. (2) The first means is a means for calculating the product value of the own line zero-sequence current and the own line resistance component zero-sequence compensation coefficient, and the third means is a means for calculating the product value of the own line zero-sequence current and the own line inductance component zero. The digital distance relay according to claim 1, characterized in that the digital distance relay is means for calculating a product value with a phase compensation coefficient. (3) In a distance relay that converts multiple electrical quantities from a power system into digital quantities and derives a relay output via a distance measuring means based on a differential equation, the power system is connected to a single transmission line. At some point, the first means for calculating the product value of the zero-sequence current of the power transmission line and the zero-sequence compensation coefficient for the resistance of the power transmission line, and the sum of each phase current of the power transmission line and the output from the first means. a second means for obtaining a resistance component zero-phase compensation current; a third means for determining the product value of a zero-phase current of the power transmission line and an inductance component zero-phase compensation coefficient of the power transmission line; and the output from the third means to obtain the inductance zero-sequence compensation current, and a fifth means to obtain the differential amount of the current obtained by the fourth means; sixth means for determining the inductance of the power transmission line from the voltage amount of the power system, the output from the second means, and each output from the fifth means; and the voltage amount of the power system and the output from the second means. and seventh means for determining the resistance of the power transmission line from the output from the fifth means.