JPH09243669A - Relay for detection of change rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a relay by which a voltage change rate can be detected with good accuracy and with high sensitivity. SOLUTION: An AC voltage in a system is sampled at a time interval T so as to be A/D-converted, instantaneous values are found, and effective values at every time interval T are found on the basis of the instantaneous values so as to be stored in the order of A, B, C,.... Regarding the stored effective values, an effective-value extraction interval Tx= [ΔVmin/(E×T)]×T=N×T is found on the basis of the settling value E (volt/sec) of a change rate and on the basis of the change amount ΔVmin of a minimum quantity of electricity required to ensure a desired accuracy (where N=ΔVmin/(E×T). According to the time interval Tx=N×T, the effective values (V0 and V-NT or the like) which compute the change rate are extracted by a changeover circuit 23, ΔT/(N×T)>=E (where ΔV=V0-V-NT) is judged by a judgment circuit 25, and an operating signal 25 is sent out according to a judged result. Since Tx>T, the judgment accuracy of a relay is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay for detecting a rate of change such as a decrease in voltage or frequency generated in a power system or the like.

[0002]

2. Description of the Related Art In order to obtain the rate of change by digital arithmetic processing, for example, (4) in Japanese Patent Laid-Open No. 1-238417.
The formula is as follows. dx / dt≈Δx / Δt = (Xt-Xt-1) / ωo (1) where ωo is the reciprocal of the sampling frequency, Xt, Xt-
1 is the value of X at times t and t-1.

Equation (1) is a special example in which Δt is the sampling interval, but if the interval of the numerator or denominator is properly selected, the rate of change of X with respect to time can be obtained. For example, in a device that detects a voltage change rate in a cycle of 100 mS, when a voltage change rate of 50 V / S is set as a set value as a detection target, it corresponds to detecting a voltage change of 5 V.

On the other hand, the input electric quantity such as voltage is the maximum value (called full scale) of the input determined by the input converter and A
The measurement accuracy is determined by the resolution of the / D converter. That is, the smaller the full scale and the larger the number of digital output digits of the A / D converter, the higher the precision becomes.
/ W is fixed, so accuracy is determined by full scale. Usually, it is necessary to determine the full scale in consideration of the maximum value that occurs in the power system, and thus, this limits accuracy.

This will be specifically described below. For example, assuming that the output of the A / D converter is a binary 8 digit (8 bits) and the full scale is 102.4V, the voltage digital data is 102.4V ÷ 2 ⁶ = 102.4V ÷ 256 = 0 per bit. It becomes 0.4V.

At this time, an error occurs due to A / D conversion. This is unconditionally 1/2 error of 1 bit, and 0.2V in the above example is the quantization error. Therefore, 50
5V voltage change detection is more affected by quantization error than V voltage change detection, and therefore detection accuracy is reduced.

[0007]

As described above, in an apparatus with a fixed detection time interval, when trying to detect a small change rate, there is a problem that the detection accuracy is lowered due to the influence of the quantization error. .

The present invention has been made to solve the above problems, and an object thereof is to provide an apparatus capable of detecting a change rate with high accuracy and high sensitivity.

[0009]

[Means for Solving the Problems]

(1) A change rate detecting relay according to the present invention includes a conversion processing unit that samples an electric quantity to be detected and sequentially converts the electric quantity into a predetermined digital quantity, a setting unit that sets a change rate of the electric quantity, and the above setting. According to the change rate of the electric quantity, the data interval extracted from the digital quantity is varied, and the change rate calculating means for obtaining the change rate of the electric quantity from the digital quantity extracted at the varied interval is provided. .

(2) Further, conversion processing means for sampling the electric quantity to be detected and sequentially converting it into a predetermined digital quantity, setting means for setting the rate of change of the electric quantity, and change of the set electric quantity. A change rate calculation means for varying the data interval extracted from the digital quantity according to the rate, and obtaining the rate of change of the electric quantity from the digital quantity extracted at the variable interval at each sampling. is there.

(3) Further, the conversion processing means for sampling the electric quantity to be detected and sequentially converting it into a predetermined digital quantity, the setting means for setting the rate of change of the electric quantity, and the change of the set electric quantity. According to the rate, the data interval extracted from the digital amount is changed, and a change rate calculating means for obtaining the change rate of the electric amount from the extracted digital amount for each variable interval is provided.

(4) Further, in any one of the above items (1) to (3), the change rate is calculated by the change rate calculating means when (ΔVmin / T)> E, Tx = [ΔVmin /
(E × T)] × T = N × T to obtain Tx, and (ΔVmin /
In the case of T) ≦ E, Tx = T, and the rate of change in the amount of electricity = ΔV / Tx, where Tx: data interval (sec) ΔVmin: the minimum amount of electricity required to secure the desired accuracy. Change amount (unit: target electric amount) T: Sampling time interval (sec) E: Electric amount change rate set value (predetermined amount of change in electric amount / se
c) ΔV: It is calculated as a change amount (unit: target electricity amount) of the digital amount extracted at the Tx interval.

(5) Further, in the above (4), the value of E is: E = ΔVmin × α = (quantization error) × k × α where α: predetermined coefficient (a ≧ 1) k: predetermined This is obtained as a coefficient (k ≧ 1).

(6) Further, conversion processing means for sampling the electric quantity to be detected and sequentially converting it into a predetermined digital quantity, setting means for setting a rate of change of the electric quantity, and change of the set electric quantity. It is provided with a means for varying the sampling interval according to the rate and a change rate calculating means for obtaining the change rate of the electric quantity from the digital quantity.

(7) Further, in any one of the above items (1) to (6), depending on the magnitude of the quantity of electricity to be detected,
By changing the full-scale value of the amount of electricity, provided with a variable output means for outputting the amount of electricity corresponding to the full-scale value,
The output electric quantity is input to the conversion processing means.

(8) Further, in any one of the above items (1) to (7), the degree of the change rate is judged according to the comparison between the obtained change rate of the electric quantity and the set change rate of the electric quantity. The change rate determining means is provided.

(9) Further, from the setting means for setting the rate of change of the electric quantity, the full-scale changing means for changing the full-scale value of the electric quantity to be detected according to the full-scale changing signal, and the full-scale changing means. Conversion processing means for sampling and sequentially converting the electric quantity of the electric quantity into a predetermined digital quantity, change rate calculating means for obtaining the change rate of the electric quantity from the digital quantity, and the calculated change rate of the electric quantity. When the change rate of the amount of electricity is within the rate of change of the amount, the full-scale variable means sends a small full-scale signal, and when the obtained rate of change of the amount of electricity exceeds the rate of change of the set amount of electricity, a predetermined signal is sent out. And rate determining means.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a change rate detecting relay according to this embodiment.

In FIG. 1, reference numeral 11 is an input converter that electrically insulates the power system from the device and converts the voltage signal into an appropriate voltage signal. This is a hold circuit, and the output signal is converted into a digital signal by the A / D converter 13, is temporarily stored in the memory 15 via the bus 17, and the effective value calculation process is executed by the CPU 14 at regular time intervals. The effective value of the input signal is stored in the memory.

On the other hand, the detected value of this apparatus is input from the settling value input circuit 16 and stored in the memory 15 to be used for operation judgment.

FIG. 2 is an explanatory diagram for obtaining an effective value from an AC waveform. The AC waveform is sampled at a predetermined interval T (T = 30 ° interval in this figure), A / D converted, and the instantaneous value data is temporarily stored in the memory 15. Next, of the instantaneous value data, the instantaneous values at 90 ° intervals (instantaneous values 1 and 4, instantaneous value 2
., And the like), the effective value (A, B, C, ...) Is obtained, and this effective value data is stored in the memory 15.

The means for calculating the effective value from the instantaneous value is a known procedure, and the value obtained by dividing the square root of the sum of squares of two instantaneous values at 90 ° (π / 2 radian) intervals by the square root of 2 is the effective value. Becomes

Next, the operation determination process according to the present invention will be described with reference to FIG.
This will be described below. Reference numeral 21 is the effective value data of the input signal stored in the memory 15 at constant time (T time) intervals as described above. Reference numeral 22 is a settling value of the change rate to be detected stored in the memory 15, and when the change rate of the input signal is larger than this value, the operation signal 25 is generated.

Now, the judgment formula in the case of detecting the rate of change using the data obtained at regular time intervals is shown by the following formula, and is executed by the judgment circuit 24. (| V0-V-T |) / T = (ΔV / T) ≧ E (2) However, V0, V-T: Effective voltage value ΔV: Change in effective voltage value T: Effective voltage value Time interval E: Set value (unit: V / S)

The smaller the settling value, the more sensitive the detection becomes. However, for this purpose, the numerator on the left side of the equation (2) becomes small, so that the influence of the quantization error becomes large and the accuracy deteriorates, as described above. Now, in the equation (2), it is assumed that there is a change in the minimum voltage effective value necessary to secure the required accuracy, and this is ΔVmin. Therefore, if the settling value is smaller than ΔVmin / T, the required accuracy cannot be obtained.

Therefore, in the case of such a small set value,
The required accuracy can be secured by selecting the time interval Tx so as to be equal to ΔVmin / T. When the settling value is given by E, this Tx is expressed by the following equation. Tx = (ΔVmin / E × T) × T = N × T (3) where N = (ΔVmin) / (E × T) (4)

In the equation (3), if ΔVmin = E, then Tx = T, but since the error is set to several times to several tens of times, E becomes several times to several tens times of ΔVmin. Here, E and ΔVmin are set values, and the minimum value of T is the sampling time, so N and Tx are obtained.

The switching circuit 23 switches according to N obtained by the equation (3), selects a voltage effective value for calculating the change in the voltage effective value, and inputs it to the determination circuit 24.
Reference numeral 4 compares the set value 22 of the rate of change with the equation (2) and sends the operation signal 25 when the rate of change of the input signal is large.

The above-described change rate calculation processing will be described with reference to the flowchart of FIG. 4 and the time series diagram of FIG. (1) The set value E of the voltage change rate and the change amount ΔVmin of the minimum voltage effective value are set (S1). (2) As [input processing], sampling and A / D conversion are performed every T time, and the obtained instantaneous value is stored in the memory 15 (S2).

(3) As [effective value calculation processing], the effective value is calculated from the stored instantaneous value and stored in the memory 15 (S3). (4) As [effective value extraction processing], Tx = N · T is obtained, and the effective value of the N · T interval is extracted from the memory every T time (S4). This extraction is, as shown in FIG. 5, effective values of V- (N + 1) T and V-T, V-NT and V, which are separated by NT time (see FIG. 3).
The effective value of 0 is sequentially extracted. (5) As a [change rate detection process], a change rate (ΔV / N · T) is calculated from the extracted effective value (S5). That is, ΔV / N · T = (V− (N + 1) T−V−T) / N · T is calculated, and then ΔV / N · T = (V−NT−V0) / N · T Is calculated. (6) The calculated change rate is compared with the set value of the set change rate, and if ΔV / N · T ≧ E, an operation signal is sent (S
6).

As shown in FIG. 5, the above processing operation is started in accordance with the start command 41 generated at a constant cycle T, and two effective value data at intervals of N times T are used every T time. Then, the change amount detection process of steps S5 and S6 is executed.

Here, the quantization error is, as described in the prior art, quantization error = (1/2) × (VF / B) where VF: full-scale value of electric quantity B: full-scale value VF Is a value obtained by converting the number of bits (bit) of digital conversion corresponding to the above into a decimal value.

Assuming that one of the means for setting the value of E is ΔVmin = (quantization error) × k, the rate of change E of the settling value is E = ΔVmin × α = (quantization error) × k × α ---------- (5) However, E may be set as k: a predetermined coefficient (k ≧ 1) α: a predetermined coefficient (α ≧ 1). Where α is usually ΔVmin
Takes several times to several tens of times.

If k = 1 is set from equation (5) as one of the means for setting E, then ΔVmin = (quantization error), and E = (quantization error) × α ------ --- (6), and E may be set by the equation (6). .

As described above, according to the embodiment of the present invention, the data interval used for detecting the change amount is variably controlled according to the change rate of the settling value, so that the change rate can be detected with high accuracy. It is effective.

Embodiment 2 In the first embodiment, the time interval for calculating the rate of change is controlled by changing the data interval used, but the same effect can be obtained by executing the process for detecting the rate of change in time division. It is a thing.

The block diagram of this embodiment is similar to that of FIG. This operation will be described based on the flowchart of FIG. 6 and the flowchart of FIG. 7. (1) The set value E of the voltage change rate and the minimum voltage effective value change ΔVmin are set (T1). (2) Set a = 1 (T2).

(3) As [input processing], sampling is performed every T time, A / D conversion is performed, and the obtained instantaneous value is stored in the memory (T3). (4) As [effective value calculation processing], the effective value is calculated from the stored instantaneous value and stored in the memory (T4).

(5) As [time-division control processing], N is calculated from the equation (4) of the first embodiment (T5). (6) Compare N ≧ a, and if a is smaller than N (T
6), (7) a = a + 1 is calculated (T7),

(8) When N ≧ a at step T6,
Tx = N.multidot.T (time division number) is obtained, and as shown in FIG. 7, the effective value for each time division N.T interval is extracted from the memory (T
8). In this way, the extraction of the effective value is performed in steps T5 to T8.
The time-division control process is executed at time intervals determined by the number of time-divisions.

(9) In [change rate detection processing], the change rate (ΔV / N · T) is calculated from the extracted effective value (T).
9). (10) The obtained change rate is compared with the set value of the set change rate, and if ΔV / N · T ≧ E, an operation signal is sent (T10).

As shown in FIG. 7, the above processing operation is started in accordance with the start command 41 generated at a constant cycle T, and the change detection processing at steps T9 and T10 is executed at a cycle N times T. To be done. That is, the time division control is performed so that the number of time divisions is determined to be equal to N obtained by the equation (3).

As described above, according to the embodiment of the present invention, the execution cycle of the change detection is variably controlled by the time-division processing according to the change rate of the settling value. In comparison, the number of times the change rate is calculated (T in the first embodiment)
Each time, every N · T time in the second embodiment) decreases, so that there is an effect that the load on the CPU can be reduced.

Embodiment 3. In the second embodiment, the execution cycle T is fixed and the time interval of change rate detection is controlled by the number of time divisions, but the same effect is obtained by making the execution cycle variable.

In FIG. 8, reference numeral 51 is a frequency dividing circuit for inputting the clock 52, controlling the execution cycle, and generating a start command to the CPU. The operation of FIG. 8 will be described with reference to the flowchart of FIG. 9 and the time series diagram of FIG.

(1) The set value E of the voltage change rate and the minimum voltage effective value change ΔVmin are set (U1). (2) Obtain Tx = N · T (U2).

(3) In the frequency dividing circuit 51, the clock interval of the CPU 14 is changed to NT, and the sampling period is changed (U3). (4) As [input processing], sampling is performed every N · T time, A / D conversion is performed, and the obtained instantaneous value is stored in the memory 15 (U4).

(5) As [effective value calculation processing], the effective value is calculated from the stored instantaneous value and stored in the memory 15 (U5). (6) As [effective value extraction processing], two effective values are extracted in the order of storage in the memory (U6). This extraction can be easily performed because the sampling period is N · T time as shown in FIG.

(7) As [change rate detection processing], the change rate (ΔV / N · T) is calculated from the extracted effective value (U
7), (8) The calculated change rate is compared with the set value of the set change rate, and if ΔV / N · T ≧ E, an operation signal is sent (U
8).

As described above, according to the embodiment of the present invention, the execution cycle of the change detection is variably controlled by the clock of the CPU according to the change rate of the settling value.
Extraction of the effective value can be done very simply by extracting in sequence,
Time division processing becomes unnecessary. In addition, the calculation processing interval is NT
Each time, the load on the CPU is reduced, and the memory capacity for storing the effective value may be small, so that there is an effect of saving.

Embodiment 4 FIG. In the above embodiment, the change rate detection accuracy is improved by increasing the change rate detection time interval so that the change in the voltage effective value does not become too small. Form 4
Reduces the full scale of the input signal to
The accuracy of the data itself after D conversion is improved, and the accuracy of change rate detection is improved.

FIG. 11 shows the input converter 61 of this embodiment.
Which is an alternative to the input converter 11 described in the above embodiment. In FIG. 11, reference numeral 62 denotes an insulating transformer, which is provided with a tap on the secondary side, electrically insulates the power system from the present apparatus, and converts the voltage signal into an appropriate voltage signal. Reference numeral 63 is a full-scale switching circuit, which selects the voltage from the insulating transformer 62 with a tap in accordance with the calculated input signal at the time interval N · T and switches the full-scale value of the input signal.

The processing operation will be described with reference to the flowchart of FIG. (1) The set value E of the voltage change rate is set (V1). (2) Since the quantization error is determined by the full-scale value and the number of bits of the corresponding A / D converter as described in the related art, ΔVmin = quantization error × k, where k: predetermined Is set as a coefficient (k ≧ 1). The relationship between E and ΔVmin is as follows: E = ΔVmin × α = (quantization error) × k × α (α: a constant, α ≧ 1, usually several times to several tens of ΔVmin)
Since it is set to double, if k is set as a fixed value,
α becomes α = E / ΔVmin and is automatically calculated and determined (V2). (3) As [input processing], sampling is performed every T time, A / D conversion is performed, and the obtained instantaneous value is stored in the memory (V
3).

(4) As [effective value calculation processing], the effective value is calculated from the stored instantaneous value and stored in the memory (V
4). (5) As [effective value extraction processing], two effective values are extracted in the order of storage in the memory (V5). (6) As [change rate detection processing], a change rate (ΔV / N · T) is calculated from the extracted effective value (V6).

(7) The judgment of ΔV / N · T ≧ E is made (V
7), (8) If the determination result is No, it is determined whether or not it is the minimum full scale value (V8), and if it is (9), a full scale switching signal is sent out and the full scale switching circuit 63 The full scale value is switched to the smaller side (V9).

For example, if the system voltage is 100V and the full-scale value is 10V, then the voltage on the secondary side of the insulation transformer becomes 1V when the system voltage becomes 10V. Therefore, when the system voltage is 10V, the full-scale value becomes Switch to 10V. By this switching, ΔVmin (quantization error) becomes 1/10, so from E = ΔVmin × α, E
Becomes 1/10, and the value of E is changed and set so that the detection accuracy is improved.

(10) After changing E, steps V3 to V6
The effective value is calculated with, and if the judgment in step V7 is No,
If it is not the minimum full scale value in step V8, steps V3 to V8 are repeated until the minimum full scale value is reached, and the full scale value is changed. If the minimum full scale value is reached, the value E is compared and determined in step V6. I do.

(11) If the determination in step V7 is Yes during the process of (10), an operation signal is sent (V
10). (12) If the determination in step V7 is Yes in the processing in steps V3 to V6 for the first time, the operation signal in step V10 is transmitted.

In FIG. 11, the isolation transformer 62 is used as a transformer with a tap to switch the tap by the full-scale switching circuit, but switching means for continuously varying the voltage may be used.

As described above, according to the embodiment of the present invention, the full-scale switching circuit is controlled in accordance with the change rate of the settling value, so that the change rate is detected at every predetermined period T. Therefore, there is an effect that high-speed change rate detection can be obtained.

Embodiment 5 In the fourth embodiment, the full scale is switched according to the rate of change of the set value, but the full scale may be switched according to the system voltage in FIG.

In this case, when the system voltage is 100 V, if the full scale is 10 V, the system voltage becomes 10 V, the full scale value becomes 10 V, and if the system voltage becomes 80 V, the full scale value becomes 10 V. . That is, the full scale value is always 10V (or
(Close to that value).

In this case, ΔVmin is not set, and E
Is set to a desired fixed value (the same as in the first embodiment).
By doing so, the quantization error inherent in ΔV of ΔV / T is reduced, and the error of ΔV is reduced.
It is possible to reduce the error in the determination of / T ≧ E.

Further, in this embodiment, the system voltage is detected, but instead of detecting the system voltage, the output voltage of the full scale switching circuit 63 is detected, and the full scale is set so that this voltage becomes 10 V in the above example. May be switched.

Further, in FIG. 11, the isolation transformer 62 is used as a transformer with a tap so that the tap is selected and switched by the full-scale switching circuit, but a switching means for continuously varying the voltage may be used.

Sixth Embodiment In the above embodiment, the rate of change of the system voltage is calculated and compared with the set value of the rate of change, and the operation signal is sent according to the comparison result, but the rate of change before comparison is performed without performing comparison. At the time of obtaining, the rate of change data is sent to the outside, the normality / abnormality is judged externally, the rate of change data is evaluated by a terminal, etc., and the rate of change data is displayed in different colors in an analog manner. You may make it alarm.

Embodiment 7 Although the effective value of the AC voltage has been described above as an example of the object of change rate detection, the effective value of the AC current may be used and the same effect can be obtained. Further, even if the amount of electricity such as the frequency of the AC voltage, the AC power / reactive power, and the power factor (phase) is detected as the target of the change rate detection, the calculation formula for converting the instantaneous value into the electricity is different, but the present invention can be applied .

For example, in the case of targeting electric power, the rate of change can be detected by multiplying the instantaneous value of voltage and current and calculating the electric power from the value of the instantaneous electric power value at 90 ° intervals.

Also, when obtaining the change rate of the average value of the AC waveforms such as AC voltage and AC current, the change rate is detected by deriving the known average value from the A / D converted instantaneous value. can do. It is also applicable to the case where the rate of change of the effective value, average value, etc. is obtained from the rectified waveform obtained by rectifying the AC waveform.

[Brief description of drawings]

FIG. 1 is a block diagram of a change rate detection relay according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for obtaining an effective value from an AC waveform according to the first embodiment of the present invention.

FIG. 3 is an operation determination processing block diagram of change rate detection processing according to the first embodiment of the present invention.

FIG. 4 is a flowchart of operation determination processing of change rate detection processing according to the first embodiment of the present invention.

FIG. 5 is a time series diagram of change rate detection processing according to the first embodiment of the present invention.

FIG. 6 is a flowchart of operation determination processing of change rate detection processing according to Embodiment 2 of the present invention.

FIG. 7 is a time series diagram of change rate detection processing according to the second embodiment of the present invention.

FIG. 8 is a block diagram of a change rate detection relay according to a third embodiment of the present invention.

FIG. 9 is a flowchart of operation determination processing of change rate detection processing according to Embodiment 3 of the present invention.

FIG. 10 is a time series diagram of change rate detection processing according to the third embodiment of the present invention.

FIG. 11 is an input converter block diagram of a change rate detection relay according to a fourth embodiment of the present invention.

FIG. 12 is a flowchart of operation determination processing of change rate detection processing according to Embodiment 4 of the present invention.

[Explanation of symbols]

11 input converter, 12 sampling and holding circuit, 13 A / D converter, 14 CPU, 15 memory, 16 set value input circuit, 21 effective value data, 22
Change rate set value, 23 switching circuit, 24 determination circuit, 5
1 frequency divider, 52 clocks, 61 input converter, 62
Isolation transformer, 63 full scale switching signal.

Claims (9)

[Claims] 1. A conversion processing means for sampling an electric quantity to be detected and sequentially converting it into a predetermined digital quantity,
Setting means for setting the rate of change of the electric quantity, and changing the data interval extracted from the digital quantity according to the set rate of change of the electric quantity, the change of the electric quantity from the digital quantity extracted at the variable interval A change rate detecting relay having a change rate calculating means for obtaining a rate. 2. A conversion processing means for sampling an electric quantity to be detected and converting it into a predetermined digital quantity in sequence.
Setting means for setting the rate of change of the electric quantity, and the data interval extracted from the digital quantity is changed according to the set rate of change of the electric quantity, and the digital quantity extracted at the variable interval every time the sampling is performed. And a change rate detecting relay for obtaining the change rate of the amount of electricity from the change rate detecting relay. 3. A conversion processing means for sampling an electric quantity to be detected and converting it into a predetermined digital quantity in sequence.
Setting means for setting the rate of change of the quantity of electricity, and the data interval extracted from the digital quantity is varied according to the rate of change of the quantity of electricity set, and the quantity of electricity is calculated from the digital quantity extracted at each of the varied intervals. Change rate detecting relay having a change rate calculating means for obtaining the change rate of 4. The method according to claim 1, wherein
The calculation of the rate of change by the rate-of-change calculating means is such that when (ΔVmin / T)> E, Tx = [ΔVmin / (E
× T)] × T = N × T to obtain Tx, and when (ΔVmin / T) ≦ E, set Tx = T, and change rate of electric quantity = ΔV / Tx, where Tx: data interval collected from digital quantity (Sec) ΔVmin: Minimum amount of change in electricity required to secure desired accuracy (unit: target amount of electricity) T: Sampling time interval (sec) E: Electricity change rate set value (predetermined amount of change in amount of electricity) / Se
c) ΔV: A change rate detecting relay characterized by being calculated as a change amount (unit: target electricity amount) of a digital amount extracted at intervals of Tx. 5. The value of E according to claim 4, wherein E = ΔVmin × α = (quantization error) × k × α, where α: a predetermined coefficient (a ≧ 1) k: a predetermined coefficient (k ≧ 1) A change rate detection relay characterized by being obtained as 6. A conversion processing means for sampling an electric quantity to be detected and converting the electric quantity into a predetermined digital quantity in sequence.
Setting means for setting the rate of change of the electric quantity, means for varying the sampling interval according to the set rate of change of the electric quantity, and change rate calculating means for obtaining the rate of change of the electric quantity from the digital quantity. Change rate detection relay equipped. 7. The method according to claim 1, wherein
Depending on the magnitude of the quantity of electricity to be detected, the full scale value of the quantity of electricity is varied, and variable output means for outputting the quantity of electricity corresponding to the full scale value is provided, and the output quantity of electricity is converted. A change rate detecting relay characterized in that the relay is input to the means. 8. The method according to claim 1, wherein
A change rate detecting relay characterized by comprising change rate determining means for determining the degree of the change rate according to a comparison between the calculated change rate of the electric quantity and the set change rate of the electric quantity. 9. Setting means for setting the rate of change of the quantity of electricity,
Full-scale variable means for varying the full-scale value of the quantity of electricity to be detected according to the full-scale variable signal; and conversion processing means for sampling the quantity of electricity from the full-scale variable means and sequentially converting it into a predetermined digital quantity. A change rate calculating means for obtaining a change rate of the electric quantity from the digital quantity, and a signal for making a small full scale by the full scale changing means if the obtained change rate of the electric quantity is within the set change rate of the electric quantity. And a change rate determination relay that sends a predetermined signal when the calculated change rate of the electric quantity exceeds the set change rate of the electric quantity.