JPH0648893B2 - Digital relay with time delay characteristics - Google Patents

Description

TECHNICAL FIELD The present invention relates to a digital relay in which an operation time required for fault elimination is set when a system fault is detected.

[Prior Art] A conventional induction disk type relay has a time delay characteristic as shown by a curve X in FIG. In the figure, the horizontal axis I represents the input value, the vertical axis T represents the relay operating time, I _min represents the minimum operating input, and T _min represents the minimum operating time. Also, the shaded area indicates the operating range, that is, the margin width in which the operating time can be determined for the input. This property is important because it is necessary to minimize the effects of accidents, but the important thing is that
The characteristic is that the operating time is long for a small fault current and the operating time is short for a large fault current. The above operating time indicates that the accident elimination may be delayed to some extent when the fault current is small, and conversely, when the fault current is large, prompt accident elimination is required. The operating time is obtained from the time delay characteristic.

When the characteristics of this induction disk type relay are realized by a conventional digital relay, the calculation and setting of the above operating time are processed according to the flow shown in FIG.

That is, in block 1, current / voltage information of the electric power system is input, and the current / voltage information is sampled at a predetermined sampling frequency and subjected to analog / digital conversion, and then numerical calculation is performed. In block 2, whether or not an accident has occurred in the power system is detected based on the result of the numerical calculation, that is, the current or voltage value data. If it is not an accident, in block 3, a process that should be executed after the accident process or a normal process is executed. In the case of an accident, when setting the operating time of the relay in the timer circuit, the operating time is expressed by the function X showing the time-delay characteristic of FIG. 8 or the time-delay characteristic of FIG. 8 by the step-delay characteristic of FIG. The operation is performed based on this stage time-delay characteristic and set as a timer value in the timer circuit (block 5). If you do not set the timer value,
That is, when the timer value is not calculated, it is determined whether or not the operation time calculated based on the time delay characteristic is equal to or longer than the preset timer value (block 6). In, the operation time is trip output (output as it is), and if the operation time is less than or equal to the timer value, in block 8, the timer value of the timer circuit is counted up so as to match the operation time.

However, in the case of the above-mentioned processing, the shock applied to the system increases when the accident current changes during the accident. The shock applied to this system will be described below.

For example, in the two-machine system shown in FIG. 10, the generator G _A
It is assumed that the generator G _B and the generator G _B are sending electric power P _AB from the generator G _A to the generator G _B with a phase difference θ ₁ between them. At this time, it is assumed that a three-phase ground fault accident occurs at the point A near the end of the bus A and the accident is eliminated after the accident duration time t _f . Also the 11th
As shown in the figure, it is assumed that the phase difference opens up to θ ₂ during the accident duration t _f . The fault current at this time is I _f . At this time, the generator G _A receives an acceleration force of P _AB · (θ ₂ −θ ₁ ).

Also, the devices that make up the system are damaged in proportion to the product of the magnitude of the fault current and the duration of the fault. Such impacts such as acceleration and damage caused by an accident are “shock applied to the system”.

Now, at time t = t _n , the magnitude of the fault current is I ₁
Suppose that an accident occurred. This accident time characteristics shown in FIG. 8, as shown in FIG. 12, the fault is cleared time when I ₁ (operation time) because T ₁ is chosen, t = t _n + T
Accident elimination in ₁ . Therefore, the fault current I ₁ is
_The shock applied to the above system is (I
₁ × T ₁ ).

It is assumed that at time t = t _n , an accident with an accident current I ₂ has occurred. This accident is eliminated at t = t _n + T ₂ . Therefore, the shock at this time is (I ₂ × T
₂ )

Thus, the fault current at time t = t _n is I ₁ becomes accident occurs, the operation time T ₁ corresponding to the fault current I ₁ is set. After that, at time t = t _n + t _ni , it is assumed that the fault current changes from I ₁ to I ₂ in a direction in which the fault current increases due to a change in fault resistance, for example. At this time, assuming that the operating time T ₁ initially set is used as it is, t _ni is
Assuming that the minimum value is as close to 0 as possible, the fault current I
The state of ₂ will continue for T ₁ . Therefore, the shock of the system at this time is (I ₂ × T ₁ ).

That is, the system shock when the fault current is I ₂ is S ₁
= I ₂ × T ₂ but the maximum shock when the fault current changes from I ₁ to I ₂ is I ₂ × T ₁ = I ₂ × {T ₂ + (T ₂ −T ₁ )} = I ₂ × T ₂ + I ₂ × (T ₂ −T ₁ ), resulting in an extra shock by S ₂ = I ₂ × (T ₂ −T ₁ ).

[Problems to be Solved by the Invention] Since the calculation of the operating time and the count-up of the timer in the conventional digital relay with time delay characteristics are performed by the flow shown in FIG. When I changes from I ₁ to I ₂ , the shock applied to the system until the accident is cleared is (S ₁ + S ₂ ) in Fig. 12.
Therefore, it becomes much larger than the minimum shock value S ₁ , and the original purpose of the digital relay, that is, the purpose of system protection is not achieved.

The present invention has been made in view of the above problems, and during an accident,
An object of the present invention is to obtain a digital relay with a time delay characteristic that can reduce the shock applied to the system before the accident is cleared when the accident current changes from I ₁ to I ₂ .

[Means for Solving the Problems] The digital relay with time delay characteristics of the present invention changes the current value after the occurrence of an accident until the operation time _Top elapses after the occurrence of the accident. If you check and if the current value is changing, the past history specified by the product of the current value before the change and the duration of the current value so that the protection function according to the change can be achieved. Correcting operation time T using the value
_op 'is calculated based on the following formula, This correction operation time T _op 'is when different from the operation time T _op is the correction operation time T _op' was so provided the operating time correction means for setting a timer circuit.

[Operation] In the digital relay with time delay characteristics according to the present invention, when the accident current changes with time after the occurrence of the accident, the operation time T calculated when the occurrence of the accident is detected.
_{Since op} is corrected to the correction operation time T _op ′ which is corrected according to the momentary change of the fault current, protection corresponding to the change of the fault current can be easily realized.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 7.

FIG. 1 is a block diagram showing the configuration of a digital relay with time delay characteristics of the present invention. In the figure, 41 is a high-speed input device, 42 and 43 are storage units, 44 is an arithmetic processing unit, 4
Reference numeral 5 is a timer circuit in which the operation time and the correction operation time are set, 46 is a determination circuit, 47 is an output circuit, and 48 is a timer circuit for timed cooperation.

The storage means 42 has, for example, a data area for storing a conversion table showing the characteristics shown in FIG. 8 or FIG. 7, that is, a table showing the relationship between the operating time T _op and the current value, and system data. Has a data area for temporarily holding the. The storage unit 43 also stores a processing program for arithmetically processing the system data.

With the above configuration, system data such as current / voltage information which has been digitalized at a certain time interval is temporarily held in the data area of the storage unit 42 via the high speed input device 41. After that, the arithmetic processing unit 44 arithmetically processes the system data according to the procedure of the processing program stored in the storage unit 43. If an accident is detected from the result of the arithmetic processing, the operating time _Top is first calculated from the conversion table of the storage unit 42 and set in the timer circuit 45 according to the magnitude of the accident current.

Next, during the period from the occurrence of the accident to the elapse of the operation time T _op , the change in the accident current value after the occurrence of the accident is checked, and if the accident current value is changed, the change is made. The correction operation time T _op ′ is calculated by using the past history value defined by the product of the previous current value and the duration of the current value, and the correction operation time T _op ′ is different from the operation time T _op. In this case, the correction operation time T _op ′ is set in the timer circuit 45. The processing relating to the correction operation time T _op ′ is realized by the operation time correction means, and this operation time correction means
It may be realized by configuring the arithmetic unit 44 with a discrete circuit or by software processing.

The details will be described below.

The relationship between the time limit (T) and the current value of the time delay characteristic relay is that I · T = K (K is a constant) (1) between the input current (I). Therefore, if an accident occurs, the second
In block 5 of the figure, the operating time is obtained from the equation (1) (actually, the same characteristic as in FIG. 8, that is, T _min and I
_It is obtained from a conversion table showing the hyperbolic time delay characteristic with _min as an asymptote), and the value is set in the timer circuit 45. That is, an accident occurs at the time t _n, the accident current I (t _n) in accordance with the timer value T _op (t _n) is set. Now, at the next calculation timing (t _{n + 1} ), if the operation time is equal to or less than the timer value when the accident continues due to the processing of blocks 1 and 2 (determination in block 6, that is, after the accident occurs, Until the operating time T _op has expired), in block 9, the necessity of correcting the timer value is checked by the following equation.

Generally, equation (3) is used.

If correction is required, then in block 10, I (t
_{n + 1} T _op corresponding to the value) (t n _{+ 1)} is (1) (actually sought from the aforementioned conversion table), as its value is (4) the correction operation time T _op 'by formula Will be corrected.

When correction is made when t = t _{n + l} , When t = t _{n + l + m} , the following formula is obtained when further correction is made.

Also, when setting a new time, all the time until then is reset.

The above formulas (4) to (6) are It is based on. The past history value will be described in detail.

For example, in FIGS. 3 and 4, the fault current I (t
The accident elimination time (operation time) T _op in _n ) is T _op = T
(T _n ), and for I (t _{n + l} ) T _op = T (t
_{n + l} ). T _op corresponding to the _fault current is T (t
_n ) and T (t _{n + 1} ). Now, at t = t _n , I (t
the accident occurrence of _{n), t = t n +} l fault current in the I (t
_{n + l} ). If the timer is reset without any correction, the accident is eliminated at time t = t _{n + l} + T (t _{n + l} ), so the shock (S) of the system until the accident elimination is S = I (t _n ) × (t _{n + l} −t _n ) + I (t _{n + l} ) × T (t _{n + l} ), and only I (t _n ) × (t _{n + l} −t _n ). You will receive extra shock. Therefore, at t = t _n , I (t
_n ) accident occurs, and I (t _{n + l} ) at t = t _{n + l}
I (t _{n + l} ) considering the history of the accident
T _op in Then, the shock of the system until the accident is eliminated is S = I (t _n ) × (t _{n + l} −t _n ) + I (t _{n + l} ) × {I (t _n ) × (t _{n + l} −t _n )
/ I (t _{n + l} )} = I (t _n ) × (t _{n + l} −t _n ) + I (t _{n + l} ) × T (t _{n + l} ) −I (t _n ) × (t
_{n + l} −t _n ) = I (t _{n + l} ) × T (t _{n + l} ), which is the same shock as when the fault current of I (t _{n + l} ) continued from the end, resulting in an extra You can prevent the shock from affecting the system.

As described above, by correcting the timer value every time it is necessary considering the past history and resetting it, the original time delay characteristic shown in Fig. 5 is always maintained even if the accident current changes during the accident. Obtainable. Although the original time delay characteristic in which the past history is taken into consideration is realized as described above, the operation output is output after the time set in the timer circuit 45 has elapsed.

In the determination circuit 46 of FIG. 1, a command is given to the output circuit 47 on the condition that there is a signal of both the operation command from the timer circuit 45 and the operation command from the arithmetic processing unit, and the output circuit 47 is given.
Sends a device control signal. The operation command from the arithmetic processing unit 44, that is, the accident continuation signal output while the arithmetic processing unit 44 detects an accident is I (t _n ) −I _min ≧ Iε (Iε is Small constant)
In this case, I _min is a value determined by the system configuration and is a value preset in the storage unit 42. Further, the minimum operation time T _min is the redundancy included in the processing algorithm (for example, the arithmetic processing device 4
In 4, the operation signal is output to the timer circuit on condition that the operation signal is output K times consecutively. A value t _0, which is determined by), is a value determined by the output from the conversion table to determine the operation time by the input T _op. This minimum operating time T _min is not directly related to the determination of T _op ′ considering history.

When applied to an actual system, time coordination between relays is required in addition to the above characteristics. Therefore, in the present invention, timed cooperation is realized by the flow shown in FIG. That is, next to block 2 in FIG.
Is provided, and the cooperative time processing is performed before entering the route for calculating the time delay characteristics in FIG. By doing so, first, when an accident occurs, the timed cooperative processing calculation is first executed before the timed characteristic calculation is executed, and thereafter, the timed characteristic calculation is executed, so that the timed cooperation is considered as shown in FIG. Multi-stage time delay characteristics can be easily realized. This cooperation time is set in the timer circuit 48.

According to the above-mentioned embodiment, since the optimum time delay characteristic is obtained by the operating time correction means, when the accident current changes from I ₁ to I ₂ during an accident, the shock applied to the system before the accident is eliminated is reduced. At the same time, since the timed cooperation processing calculation is first performed only under the accident occurrence condition, the timed cooperation between the relays can be easily realized.

As described heretofore, according to the present, time characteristics with digital relay of the present invention, since comprise the operating time correction means, the optimum time characteristics can be obtained, in an accident, the accident current from I ₁ I ₂
If it changes to, it is possible to reduce the shock applied to the system until the accident is cleared.

[Brief description of drawings]

1 to 7 show an embodiment of a digital relay with time delay characteristics of the present invention. FIG. 1 is a configuration block diagram, FIG. 2 is a flow chart showing a procedure of operating time setting processing, 3 and 4 are diagrams for explaining the history, and FIG.
FIG. 6 and FIG. 6 are views showing the characteristics of the relay, FIG. 7 is a view showing the characteristics of FIG. 8 as the step time characteristics, and FIGS.
FIG. 8 shows a conventional example, and FIG. 8 is a diagram showing time-delay characteristics,
FIG. 9 is a flowchart showing the procedure of the operating time setting process,
0 to 12 are diagrams for explaining a shock applied to the system. 42 ... storage unit, 44 ... arithmetic processing unit (digital processing unit), 45 ... timer circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A method of inputting current / voltage information of a power system, sampling at a predetermined sampling frequency, performing analog / digital conversion, and then performing a numerical operation at a predetermined time interval using a digital arithmetic processing device. The operation time T calculated based on the conversion table, which is a time-dependent characteristic indicating the relationship between the operation time T _op and the current value, when the presence or absence of a system accident that has occurred in the power system is detected.
_{In a} digital relay with time characteristics, in which _op is set in a timer circuit, the change in the current value after the occurrence of the accident is checked from the occurrence of the above accident until the operation time T _op elapses. If the current value is changing, the correction operation time T _op ′ is calculated based on the following equation using the past history value defined by the product of the current value before the change and the duration of the current value. Then This correction operation time T _op 'if differs from the operation time T _op is the correction operation time T _op' and operating time correction means for setting a timer circuit, in between the output and the accident continues from the timer circuit A digital relay with a time delay characteristic, comprising: a judgment circuit which gives a command to an output circuit on condition that both signals of an accident continuation signal from the digital processing device to be output are present.