JPS5837772B2 - Distance relay method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance relaying method for detecting faults in power transmission lines, and in particular to implementation by a digital device.

Various failures occur in power systems.

For example, lightning can cause a ground fault on power lines. Accidents such as short circuits may occur.

It is necessary to protect power transmission lines from such disturbances.

For this purpose, various protective relays have been developed, and protective relay systems considered to be optimal depending on the power transmission line structure are adopted.

Conventionally, protective relays for this purpose have been constructed using dedicated analog circuits, such as one for detecting a drop in voltage, one for detecting the distance to the fault point, the direction of the fault point, etc.

Therefore, there are disadvantages such as a large number of types of protective relays being required, high manufacturing costs, and difficulties in management and operation.

On the other hand, with the recent progress in digital computers, attempts have been made to implement the above-mentioned protective relays using general-purpose digital meters.

The present invention completely digitizes a distance relay device, which is a main element of a protective relay, and provides a distance relay method that is realized based on digital values obtained by sampling. purpose.

The present invention provides a judgment equivalent to the operation judgment of a distance direction relay device conventionally constructed by an analog circuit, using the zero point of the input AC amount introduced therein. In other words, this study focused on the fact that if the magnitude of the input AC amount at any given time and the point at which the input AC amount changes from positive to negative or from negative to positive can be determined using digital calculations. .

The derivation of this zero point and the input AC amount, and the digital processing of the AC amount to allow the digital computer to efficiently perform the digital calculation will be described in detail below.

FIG. 1 is an explanatory diagram for explaining an embodiment for zero point detection according to the present invention, and A(t) in the figure is a sine wave.

Now, the absolute values of the sine wave A(t) at times a and b before and after the zero point D of this sine wave A(t) are A(a) and A, respectively.
(b) , the time between time a and b is It, the point of sine wave A(t)h at time a is a', and the point of sine wave A(t)h at time b is b / , If the time point on the time axis when connecting a/ point and b' point is C, the time between a and c is Jtlt
The time At2 between cb is determined by the following equations.

At this time, if time a and time Jt are known, it is easy to find time C.

Comparing the difference Jta between the point of fcc obtained by KL and the zero point D of the sine wave A(t), this difference Jta is A
It is clear from the results of calculation 2 that when t=1, the maximum angle is about 5 degrees or less.

The smaller Jt is than π/2, the more accurately the zero point D of the sine wave A(t) can be detected.

Figure 2 is an explanatory diagram of the principle for determining impedance, reactance, and resistance according to the present invention. The sine waves are A(t) and B(t), and the sine waves are waves A(t) and B(t)
to sample.

General K Absolute value A of sine wave A(t) at a certain time nK
(n) and the point in time (n-1) K> before the sampling period
If A(n)・A(n-1)≦0 when A(n-1) of the sine wave A(t) is sequentially multiplied by the magnitude A(n-1) of the sine wave A(t)
The zero point of this sine wave A(t) exists between and (n-1).

With the above method, the zero points of sine waves A(t) and B(t), for example, the zero point between time points a and b for sine wave A(t)K, and the time points d and e for sine wave B(t)K. Detect the zero point between the sine waves A(t) and B(t) at each time point.
Substituting the absolute value of into the equation ( ]), Jt2 and At
Find 2'.

The phase difference φ between the sine waves A(t) and B(t) can be expressed by the following equation.

However, the following equation is when both sine waves A(t) and B(t) pass through the zero point in the same direction (both sine waves change from negative to positive, and when L<'d changes from positive to negative) ) is the calculation formula.

Here, the number of sampling periods of the sine wave between both zero points of sU is the zero point of KA(t)K between a and b in Fig. 2, and B(t)K between s d j e. When there is a zero point, S is 2.

Next, a case will be described in which a zero point is detected between times d and e for the sine wave B(t)K, and a zero point between times g and h for the sine wave A(t)K.

At this time, one sine wave is detecting the zero point from negative to positive, and the other sine wave is detecting the zero point from positive to negative, so A(t) and B(
The phase difference φ between t) cannot be determined by the equation (3) described above, but can be determined by the following equation.

In FIG. 2, when there is a zero point between d and e and between g and h, s = 2.

φ=π−(lt,? + S A t+l t1”
)""(4)L and below explain the concept K of the phase difference detection method that is the basis of the present invention, and f? :． .

On the other hand, the maximum value of the sine waves A(t) and B(t) is Am,
When Bm is A(t), B(t)U is generally expressed by the following formula.

A( t) = Am s in (J t 2 + Z
1 1 t) ・--”・”(5) B(t)=B
m s in (J t 2+ Z2 At) −=−
``(6) 1, the maximum values Am and Bm are as follows.

Just L. Z1 and Z2 are A(1) and B(t
) is the number of sampling periods AtO up to the point in time when is obtained.

Now, if we pay attention to equations (7) and (8). Sine wave A
(t), B(t) at a certain sampling period At, each sampling time (l t2+Z11 t,, J t,,'
+Z2, dt) and the sine wave A(t) at that point
, B(t), and the sine wave A(t
), B(t) maximum values Am and Bm can be determined at each sampling time point.

Next, using these relationships. We will discuss the case of finding voltage, current, phase difference between them, impedance, reactance, and resistance.

General K impedance Z, reactance X and resistance R are expressed as follows.

Here, ■ is the maximum value of the voltage, and is determined by equation (7).

(2) is the maximum value of current, which is determined by equation (8).

φ is the phase difference between the two, which is determined by equation (3) or equation (4).

(9) How to obtain all the characteristics of a conventional Moh relay using the impedance Z, reactance X, and resistance R found in ~0 calculations. The following operation formula may be used.

Here, Zo settling impedance, Xo-Zoco
sφo, Ro-ZoSinφ0, φ0 represent characteristic angles.

1. In a reactance relay, the reactance X in equation (10) is the set value X.

It is possible to determine whether or not it is within the 9 protection range by comparing it with the following.

Based on this idea, it is also possible to provide the characteristics of an offset mow relay and an impedance relay.

In addition, it is possible to provide a characteristic that is a combination of the Moh characteristic and the actance characteristic.

Furthermore, by taking advantage of the features of computers, it is also possible to create Maw relays with various shapes and characteristics.

Next, a specific embodiment of the present invention will be described.

1. First, FIG. 3 shows an embodiment of the input circuit of the present invention, where A is an oscillator that generates an output pulse at a predetermined period, and C and D are sine waves A(t) and B(t), respectively. Hold circuit, E is a control circuit, F is a scanning circuit, G is an analog-to-digital converter (A-D converter), H is a buffer register, ■ is an arithmetic unit, oscillator A, hold circuit C
The circuit consisting of and D is a device for creating information to be taken into a computer, the circuit consisting of a scanning circuit F, an A-D converter G and a buffer register H is a computer input device, and the arithmetic unit ■ is an arithmetic processing section of the computer. , the control device E can be said to be a control unit that controls the operation of the computer according to a certain program.

Next, the operation of this circuit will be explained.

1. Oscillator A emits a pulse-like signal at an arbitrary sampling period Jt, and holds circuits C and D and control circuit EK
Give an input signal.

In other words, the signal is applied to the hold circuit C for the full sine wave A(t) at the time of dropping and the hold circuit D for the sine wave B(t), and the values of the sine waves A(t) and B(t) at this time are held. do.

However, if the hold time of the hold circuits C and D is t, this hold time tii is shorter than the sampling period At, and within the time of the hold time t. This is a value that allows the held data to be imported into the computer.

In this way, the values of the sine waves A(t) and B(t) at each point in time are held as analog data.

Next, this hold value is taken into a computer input circuit consisting of a scanning circuit F, an AD converter G1 and a buffer register H.

That is, the control circuit E is driven by the output of the oscillation circuit A, and the control output signals S1, S2, S3 and 84 of the control circuit E are driven by the output of the oscillation circuit A.
The scanning circuit F, the A-D converter G, and the buffer register H are sequentially controlled, and the analog data stored in the hold circuits C and D is applied as digital data to the arithmetic unit (2).

FIG. 4 is a flowchart showing the processing contents of the arithmetic processing section of the computer, which is the main part of the present invention.

In this flowchart, steps 101 to 111
is the flow of zero point detection, and steps 123 to 127 are the flow of phase detection.

1. At step 101, a start 25E command is issued due to an interrupt or the like.

This interrupt is to start this flow. Second
This may be the sampling pulse mentioned in the explanation of the figure, or it may be the case where the computer is used for other judgment purposes.

Step 103 determines which type of interrupt it is.

K is NO if the interrupt is not for this detection flow
, the computer is released from the task of making this determination, and moves to another step, step 104.

When the discrimination result in step 103 is YES, the value of the sine wave A(tn) at time tn is read in in step 105.

In step 107, the time point tn− one sampling period before
The value A (tn-1) at IK and the current value A (
A(tn-1)XA(t
n).

In step 109, it is determined whether the calculation result in the previous step 107 is zero 1 or negative.

That is, A is A(tn-1) XA(tn)
If ≦0, it is on the YES side. If not, proceed to the NO side.

When the discrimination result in step 109 is YES, in step 111K. Execute equations (1) and (2) LA
Calculation for (t) The zero point of L and the sun before and after it? The times Jtll and Jtl2 between the ring times are calculated.

In this manner, the zero point of the sine wave A(t) with KL as a reference is derived from the sampling time tn-1 or tn.

In this case, since the zero point is included within one period Jt, A(
To derive the maximum value Am of t), K is ZIJt in equation (7)
Since the term Z1 is unnecessary, in step 112 Z1
=0.

If the discrimination result in step 109 is NO, the process moves to step 115, where B(tn-1)XB(tn) is calculated for AC B(tn).

And when passing through this route, A(t) includes zero point and 1
Therefore, in order to execute equation (7), Z1=Z1+1 is set.

In step 117, B(t
) to determine whether it is time to derive the zero point.

If the discrimination result in step 117 is YES, that is,
If B(tn-1)XB(tn)≦O, go to step 119K and change AC
Perform calculations to derive the zero point of At11′,it
1, calculate r.

Similar to A11, at11' is the time between the zero point of calculation L and the previous sampling point, and Jt,' is "tl
Similarly to 2, it is the time between the zero point of calculation 7 and the subsequent sampling time.

in this case. Since the zero point is included within one period At, B(
In order to derive the maximum value Bm of t), Z2Jt in equation (8)
Since the term is unnecessary, it is set as Z2-0 in step 120.

When the discrimination result in step 117 is NO, B(t
) has no zero point within its one period Jt, so Z2=Z2+1 is set to execute equation (8).

1. When step 121 is selected, as at point C in Figure 2, neither A(t) t B(t) has a zero point, so in step 121, equation (3) or (4) is JtK multiplication coefficient S for phase difference calculation of
Increase by 1. Correct S=S+1K.

The discrimination result in step 109 or 117 is YE
When S (with zero point), proceed to step 123, and here execute either equation (3) or (4) based on the relationship between the lead and lag of the two ACs A(t) and B(t). Discriminate what should be done.

In step 125, the product S-Jt of the number of springs S and the sampling period At is calculated.

In step 127, the phase difference φ is calculated using equation (3) (based on the fourth floor KL).

Next, for power detection K, the peak values of voltage and current and the zero phase difference φ between the two are required.

First, steps 171 to 177 for deriving the peak value will be explained.

In step 171, stn(J j12 +Z1- A
t) At step 175, ViSin(,!it12′+
Z2·Jt) is obtained, and in step 173, the peak values of the two alternating currents A(t) and B(t) are calculated.

Next, the flow of impedance detection will be explained in steps 191 to 197.

In the flow described above, if B(t) is non-negative.
From equations (9), (10), and (11), Z,
R calculated in all steps 191, 193 and 195 (12
) Calculations are made in Steps 197 to 199 to determine whether the accident is within the protection range or outside.

φ obtained in step 127 is (9), (10),
(Used when executing formula 10.

Here it is! r:. Although we have mainly described the case using the voltage A(t) standard, the same method can be used to detect cases where both of these conditions are satisfied at least once for the current B(t) standard.

As described above, the present invention uses a computer to determine the distance and direction of the fault point from the detector installation point in the form of impedance, reactance, and resistance from voltage and current! Since the function of the conventional analog distance relay is performed by a computer, it has the effect of reducing the manufacturing cost of the relay and making management and operation easier.

[Brief explanation of the drawing]

Figures 1 to 4 all show embodiments of the present invention, and Figures 1 and 2 are diagrams explaining the principle of operation. FIG. 3 is a diagram showing the configuration of an input circuit to the computer, and FIG. 4 is a flowchart for explaining the operation of the distance relay. A(t), B(t)...Sine wave, A...
...Oscillator, C, D...Hold circuit, E.
...Control circuit, F...Scanning circuit, G...Analog-digital converter, H...
... Buffer register, ■ ... Arithmetic device.

Claims (1)

[Claims] 1. Among the sampling values obtained by simultaneously sampling the AC input amounts related to the voltage and current of the power system at a predetermined sampling period, the current sampling value and the sampling period before the sampling period have different signs. Determine the zero point of the husband's AC input amount from both sampling values L,
Derive the time at each zero point and the current sampling point l for each of the two AC input amounts, derive the time between the points passing the zero point between the two AC input amounts, and calculate the sampling value at each sampling point and the zero point. The maximum value of each AC input amount is calculated from the time from . Determine the impedance, reactance, and resistance, and set the predetermined value related to the protection area of the power system and the impedance,
A distance relaying method characterized by detecting line abnormalities from reactance and resistance.