JPH0135576B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a distance relay method that protects power transmission lines by a combination of reactance relay characteristics and ohmic relay characteristics, and particularly relates to a distance relay method that protects power transmission lines by sampling analog quantities at regular intervals. This invention relates to a digital distance relay method for obtaining a distance relay function from three sample values.

B. Summary of the Invention The present invention provides a distance relay method in which a protective operation output is obtained by the logical product of the operation outputs of an ohmic relay and a reactance relay that respond from three sample values. By determining the reactance relay characteristics from three consecutive sample values with twice the period 2φ, it is possible to obtain accurate distance relay operation while preventing erroneous tripping operations due to accident conditions.

C. Prior Art Distance relays used to protect power transmission lines are installed at substations ASS, ASS of power transmission line L, as shown in Figure 5.
Distance relays R _A and R _B are installed on the BSS, respectively, and the relays
R _A and R _B detect accidents up to the protection ranges A _P and B _P, respectively, and cut the line.

In such a distance relay, its protective relay characteristic is determined by the combination (AND) of the reactance relay characteristic _X1 and the ohmic relay characteristic _X2 , as shown by the R-X coordinate in Figure 1. Obtains protective relay function. Among these, reactance relay characteristics
_X1 specifies the distance from the substation to the protection ranges A _P and B _P , and _X2 specifies the characteristics of an ohmic relay called a blinder.
It is attached to remove it from the operating range of X ₁ , and the shatter breaker trip output is obtained by ANDing the operating outputs of both relays.

D. Problem to be solved by the invention In the conventional distance relay system, a relay that obtains the reactance relay _{characteristic} Functionality is designed with emphasis on detection accuracy. On the other hand, a relay with ohmic relay characteristic _X2 is not required to have detection accuracy as high as characteristic _X1 , but in relation to the reaction of a reactance relay, a response that does not result in erroneous protective operation is desired. This will be explained in detail below.

If a fault occurs at point _F1 in Figure 5 from a healthy state in the load range of Figure 1 when viewed from distance relay R _A , reactance relay R _AX1 of distance relay R _A and ohm relay R _AX2 responds as shown in FIG. In this case, the reactance relay R _AX1 is in a continuous operating state (ON) regardless of the presence or absence of an accident, and the ohmic relay R _AX2 changes from the recovery state (OFF) to an operating state (ON) with a delay of response time T ₁ . In this case, since the reactance relay _RAX1 is in continuous operation, the response time _T1 of the ohmic relay _RAX2 is required to be shortened for quick protective operation as a distance relay.

However, as shown in Figure 5, the substation
If an accident occurs at _F2 points outside the ASS protection range,
The reactance relay R _AX1 returns from the operating state according to the characteristic diagram of FIG. 1, and the ohmic relay R _AX2 changes from the return state to the operating state. This situation is the seventh
As shown in the figure, when the response time T ₂ for recovery of the reactance relay R _AX1 is T ₁ < T ₂ with respect to the quick response time T ₁ of the ohmic relay R _AX2 , both relays R _AX1 , R _AX2 The AND of is established,
In other words, after the ohmic relay R _AX2 becomes operational, the reactance relay R _AX1 returns and the breaker CB ₁
I ended up making the wrong trip.

One way to do this is to increase the response of the reactance relay, but this makes it difficult to increase the response to improve distance detection accuracy. On the other hand, it is conceivable to delay the response of the ohmic relay _RAX2 , but this will cause a delay in the protective operation in the event of an accident at the _F1 point, and may cause a false trip when recovering from the accident state. For example, in the case of a fault at point _F2 , the distance relay R _B of the substation BSS generally responds by cutting off the seam breaker _CB2 . Therefore, as seen from the distance relay _RA of the substation ASS, the system returns to the load region L from the fault state at point _F2 . At this time, as shown in Fig. 7, if the ohmic relay R _AX2 is at a slow return time T ₃ , the ohmic relay R _AX2 will return after the operating time T ₄ of the reactance relay R _AX1 , and the breaker CB ₂ will be switched off. After the power outage, the power outage area will be expanded by cutting the power outage to CB ₁ .

SUMMARY OF THE INVENTION An object of the present invention is to provide a distance relay system that prevents erroneous trips in protection operations and that can accurately detect the distance of a protected area by a reactance relay.

E Means and Effects for Solving the Problems In order to achieve the above object, the present invention samples the analog quantity of electricity obtained from a current transformer and a voltage transformer at a constant synchronous φ and converts it into a digital quantity of electricity, In a distance relay system that protects a power transmission line by a combination of ohmic relay characteristics and reactance relay characteristics determined from the digital electrical quantity, the ohmic relay calculation is performed using three consecutive sample values a _o-1 and a _o of the period φ. , a _o+1 to a _o-1 ² −a _o ² + a _o+1 ² = A ² to find the effective value A, and when this effective value exceeds the set value several times in a row, the operating output is The reactance relay operation is performed at a cycle twice as long as the cycle φ.
From three consecutive sample values a _o-2 , a _o , a _o+2 of 2φ, calculate the effective value A according to a _o-2 ² + a _o ² + a _o+2 ² = 3A ² , and calculate this effective value A An operating output is obtained when exceeds the set value several times in a row, and returns immediately when the value falls below the set value, and a protective operation is performed by the logical product of the operating output of the ohmic relay and the operating output of the reactance relay. output, and the ohmic relay characteristics have a vibrational response.
The reactance relay characteristic has an integral response,
To obtain an output that provides an appropriate response between the outputs of both relays upon a change from the load area to an accident condition within or outside the protection zone, and upon return to the load zone from the accident condition. In addition, high distance detection accuracy is obtained for the reactance relay.

F. Embodiment FIG. 2 is a block diagram of a distance relay showing an embodiment of the present invention. The current and voltage of the power transmission line 1 to be protected are determined by the current transformer 2 and voltage transformer 3.
These analog electrical quantities are converted into digital electrical quantities by analog-to-digital converters 4 and 5 by sampling at a constant period and encoding the sample values. The ohm relay arithmetic processing unit 6 takes in voltage and current data from the analog-digital converters 4 and 5 at a sampling period, and performs arithmetic processing on the ohm relay having the characteristic _X2 shown in FIG. The reactance relay arithmetic processing unit 7 temporarily stores the voltage and current data from the converters 4 and 5 in the memory circuits 8 and 9 to obtain the characteristics shown in FIG.
Perform calculation processing for a reactance relay with X ₁ .
The AND circuit 10 obtains the reactance distance relay output specifying the range A in FIG. 1 by taking the AND of both outputs of the arithmetic processing units 6 and 7. These arithmetic processing units 6 and 7 either give a protective operation output to the AND circuit 10 only when the timer or counter determines that the arithmetic processing results are continuously within the operating range, or the AND circuit 10 side For the first time, when there is continuous input, we get the logical AND judgment output. Here, the arithmetic processing unit 6 obtains high responsiveness to changes in the voltage and current of the power transmission line 1 by performing arithmetic processing using sample values taken out at a sampling period at each sampling time. On the other hand, the arithmetic processing unit 7 performs arithmetic processing at the same sampling time as the arithmetic processing unit 6, but the sample values used for the arithmetic processing have a cycle that is more than twice the sampling cycle stored in the memory circuits 8 and 9. By extracting the data, the accuracy of calculation processing is increased.

A protective relay method using three sample values is applied to the arithmetic processing of the arithmetic processing units 6 and 7. As shown in Figure 3a, the sample value a ₁ of voltage or current,
_In order to extract _{a 2 , .} The arithmetic processing is performed at the time when the next sample value a ₆ is taken, and the arithmetic processing is performed using the sample values a ₄ , a ₅ , a ₆ at the time when the next sample value a ₆ is taken. At the time of capture, the period is as shown in Figure 3c.
Perform arithmetic processing using sample values a ₁ , a ₃ , a ₅ of 2φ, and use sample values a ₂ , a ₄ , a ₆ at the time when sample value a ₆ is taken as shown in Figure 3 d. Perform calculation processing.

Through such arithmetic processing, the ohm relay arithmetic processing section 6 performs arithmetic processing using the latest three sample values to detect a transient data change, that is, a change from load area L to accident F ₁ or F ₂ in FIG. or vice versa, to obtain an appropriate response to the reaction of the reactance relay. On the other hand, the reactance relay arithmetic processing section 7 obtains high accuracy through arithmetic processing using sample values of relatively long periods (2φ) of voltage and current waveforms. This prevents a protection operation caused by the logical product of both outputs. This will be explained in detail below.

First, as a protective relay method using three sample values, for example, it is disclosed in Japanese Patent Application Laid-open No. 50-61641, and the product of voltage and current, current and current, or voltage and voltage is calculated for three samples, and the second By multiplying the second product value by a constant determined by the sampling period φ, subtracting the second sampling product value from the first sampling product value, and adding the third sampling product value to the result, the current Detects voltage magnitude and phase angle.

Next, it will be explained below that there is a difference in accuracy between the ohm relay calculation for every period φ and the reactance relay calculation for every period 2φ using three sample values.

In FIG. 3, let A be the effective value of the sine wave of the instantaneous values of a ₁ , a ₂ , a ₃ . The square of this effective value is the data interval φ
_The ^calculation _{formula obtained} ^{using the three} _data ^{is shown} in _{Figure 3b} ^{. 2} = A ² ...(2). Note that if the data interval φ is set to other values such as 15°, 45°, or 60°, the second term on the left side and the coefficient on the right side will only change according to the interval φ. The same thing can be said for other intervals. Here, a ₁ , a ₂ , and a ₃ include a quantization error ±Δε, so if we now show the case where A ² includes an error, the above equation (2) becomes as follows.

(a ₁ ±Δε) ² − (a ₂ ±Δε) ² + (a ₃ ±Δε) ² ...(3) Expanding the above formula, a ₁ ² ±2a ₁ Δε+Δε ² − (a ₂ ² ±2a ₂ Δε＋Δε ² )＋a ₃ ²
±
2a ₃ Δε+Δε ² =a ₁ ² −a ₂ ² +a ₃ ² ±2Δε(±1/2Δε+a ₁ −a ₂ +a ₃ ) =A ₂ ±2Δε(±1/2Δε+a ₁ −a ₂ +a ₃ ) ……(4 ) Therefore, the second term in the above equation becomes the calculation error.

On the other hand, when calculation is performed at intervals of 2φ as shown in FIG. 3c, the equation (2) corresponds to a ₁ ² +a ₃ ² +a ₅ ² =3A ² . In this case, calculating the calculation error due to ±Δε is as follows.

(a ₁ ±Δε) ² + (a ₃ ±Δε) ² + (a ₅ ±Δε) ² = a ₁ ² + a ₃ ² + a ₅ ² ±2Δε (a ₁ + a ₃ + a ₅ ) + 3Δε ² = 3A ² ±2Δε (±3/2Δε+a ₁ +a ₃ +a ₅ )...(6) Therefore, the second term in the above equation becomes the calculation error.

Here, the error when calculating with the interval of φ,
The errors when calculating at intervals of 2φ will be compared with reference to FIG. First, a ₁ − a ₂ + a ₃ and a ₁ + a ₃ + a ₅
changes depending on the sampling phase, but when calculating the maximum value of each, in the same figure, in the calculation using the interval of φ, in equation (4), a ₁ , a ₂ , a ₃ change to positive or negative, but, or The amplitude is maximum when the amplitude is , , and a ₁ −a ₂ +a ₃ = (√3+1)A (7). In addition, in the calculation with an interval of 2φ, a ₁ , a ₃ , a ₅ change to positive or negative in equation (6), but ○,,
Or, the amplitude is maximum when the amplitude is , a ₁ + a ₃ + a ₅ = 2A (8).

That is, in the interval of φ, a ₁ , a ₂ , a ₃ do not reach the maximum value at , , , , in Fig. 4, and in the interval of 2 φ, a ₁ , a ₃ , a ₅ do not reach the maximum value in , , , , . It will not reach the maximum value.

Therefore, the error in the case of the interval φ is ±2Δε (±1/2Δε+2.73A) ...(9) from the above formulas (4) and (7), and the error in the case of the interval 2φ is the above (5), From equation (8), ±2Δε (±3/2Δε+2A) ...(10) The ratio of these errors to the true value is: For interval φ: ±2Δε (±1/2Δε+2.73A)/A ² = (Δε ² /A ² ±5.46Δε/A) ...(11) For interval 2φ: ±2Δε (±3/2Δε+2A)/3A ² = (Δε ² /A ² ±1.33Δε/A) ... (12) Therefore, in the case of 2φ, the fluctuation ratio to the true value is smaller, and sampling is performed at intervals of 2φ. Reactance relay calculation, which performs protection calculation using 1φ, can also calculate distance with higher precision than ohm relay calculation, which performs sampling at 1φ intervals.

Next, the response of both relays in the event of an accident will be explained. Reactance relay calculation and ohm relay calculation each perform calculations using three sample values,
As described above, in the ohmic relay calculation, the response is made from the successive sample values of the period φ, and in the reactance relay calculation, the reaction is made from the sample values of the period 2φ.
For example, as shown in Figure 8, which shows the current waveform at the time of an accident, when an accident occurs at time t _F and the current waveform is distorted, in the ohm relay calculation, when sample value a ₉ is taken, a ₇ , a ₈ , a ₉ to calculate the sample value
Calculate using _{a 8 ,} a ₉ , a ₁₀ when a 10 is imported, and sample value a ₁₁ is calculated using a ₉ , a ₁₀ , a ₁₁ when imported
Calculate using. On the other hand, in reactance relay calculation, when sample value a ₉ is taken in,
Calculate using a ₅ , a ₇ , a ₉ , and when a ₁₀ is taken in, calculate using a ₆ , a ₈ , a ₁₀ , and when a ₁₁ is taken in, a ₇ , a ₉ , Calculate using a ₁₁ .

Here, in the ohm relay calculation, the second term is a negative term as shown in equation (2) above, so the response to the waveform distortion caused by the accident will oscillate at each calculation time point a ₉ , a ₁₀ , a ₁₁ , etc. In contrast, in reactance relay calculation, each term is positive as shown in equation (5), so there is some vibration, but it gradually rises or falls integrally.

That is, the ohm relay responds to waveform distortion with good responsiveness, but it is relatively slow until it becomes oscillatory and reaches the state in which the relay output is obtained three times in a row, and returns quickly with high responsiveness. On the other hand, reactance relay calculation responds integrally in both directions of operation and return, resulting in relatively low responsiveness. Due to the response of both relays, F ₁ and F ₂ in Fig. 5
It is possible to eliminate erroneous connections and disconnections during point accidents and their recovery.

Hereinafter, the responses of both relays to changes in each state and changes in output will be explained in detail.

FIG. 9 shows a response waveform from the load range L to _F1 point accident in FIG. 1, and timings a ₈ to a ₁₆ correspond to the sample timings in FIG. 8. this
F In the case of _{a one-} point accident, the ohm relay calculation responds vibrationally and continues to operate while repeating the operation and recovery calculation results, and as shown in the diagram, the ohm relay output is obtained at timing a ₁₆ when the operating state continues three times. . On the other hand, in the reactance relay calculation, although there is some oscillation in the calculation result due to waveform distortion, the operating state continues and the output also maintains logic "1". As a result, a trip output of the breaker can be obtained at the timing of _a16 .

Next, Figure 10 shows the response waveform in the case of _{a 2-} point F fault.The response and output of the ohm relay calculation are the same as in the case of a _1- point F fault, but in the reactance relay calculation, the calculation result increases integrally. Returned and this first
At the second return timing _a11 , the relay output becomes logic "0", and thereafter the ohm relay output becomes logic "1", and no erroneous failure or disconnection of output occurs.

Next, FIG. 11 shows a response waveform when the _F1 point accident state returns to the load region L due to accident recovery. In the ohm relay calculation, it returns from the operating state in an oscillatory manner, and the output is at timing a ₃₈
becomes logic “0”. On the other hand, in the reactance relay calculation, although there is some vibration, the change in the calculation result is small, and eventually it settles on a value that falls within the load area L, and the output maintains the logic "1" and at timing a ₃₈ . or restore the trip output of the disconnector.

Next, Figure 12 shows the substation from the F ₂ -point fault condition.
The response waveform is shown when the load region L is returned to due to the interruption (CB ₂ ) caused by the BSS relay. At this time, the ohm relay calculation obtains the response and output as in the case of Fig. 10, and the reactance relay calculation decreases integrally from the return state and enters the operating region.
At timing _a41 when this operating state continues three times, a logic "1" is obtained at the output. At this time, since the ohm relay has already become "0", it will not produce an erroneous trip output.

G. Effects of the Invention As described above, according to the present invention, the ohm relay calculation is performed using three consecutive sample values.
Reactance relay calculation requires twice the period3
Reactance relay calculation This has the effect of obtaining high distance detection accuracy, obtaining accurate protection that distinguishes between inside and outside the protection zone, and eliminating the occurrence of accidents from the load area inside and outside the protection zone, as well as the prevention of erroneous protection operations when recovering from an accident state.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram for explaining the operation of a distance relay, Fig. 2 is a block configuration diagram showing an embodiment of the present invention, Fig. 3 is a sampling waveform diagram in the method of the present invention, and Fig. 4 is a diagram of the present invention. Waveform diagram for explaining the difference in accuracy depending on the sample value in the method, 5th
The figure is a protection interval system diagram of a distance relay, Figures 6 and 7 are time charts showing the response of conventional ohmic relays and reactance relays, Figure 8 is a diagram showing the method of extracting sample values in the present invention, and Figure 9 is a diagram showing the method of extracting sample values in the present invention.
10, 11, and 12 are response waveform diagrams in the method of the present invention. DESCRIPTION OF SYMBOLS 1... Power transmission line, 2... Current transformer, 3... Voltage transformer, 4, 5... Analog digital transformer, 6... Ohm relay calculation processing section, 7... Reactance relay calculation processing section, 8, 9... Memory circuit, 10 ...Logic circuit.

Claims (1)

[Scope of Claims] 1. Analog electrical quantities obtained from the current transformer and voltage transformer are sampled at a constant synchronized period φ and converted to digital electrical quantities, and ohmic relay characteristics and reactance relay characteristics are determined from the digital electrical quantities. In the distance relay system that protects the power transmission line by a combination of , the ohmic relay operation is performed using three consecutive sample values a _o-1 of the period φ,
Find the effective value A from a _o , a _o+1 according to a _o-1 ² −a _o ² +a _o+1 ² = A ² , and when this effective value A exceeds the set value several times in a row, When the operating output is obtained and the value falls below the set value, the reactance relay operation returns immediately, and the reactance relay calculation is performed at a cycle twice the cycle φ.
From three consecutive sample values a _o-2 , a _o , a _o+2 of 2φ, calculate the effective value A according to a _o-2 ² + a _o ² + a _o+2 ² = 3A ² , and calculate this effective value A. An operating output is obtained when exceeds the set value several times in a row, and returns immediately when the value falls below the set value, and a protective operation is performed by the logical product of the operating output of the ohmic relay and the operating output of the reactance relay. Distance relay method characterized by obtaining output.