JPH0572170B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to calculations for protective relays, especially ground fault direction relays (also simply referred to as protective relay calculations) in protective relay systems that protect power systems. on how to do it.

[Conventional technology]

Fig. 4 is a block diagram showing the configuration of a general ground fault direction relay, Fig. 5 is a characteristic diagram showing the phase characteristics of the ground fault direction relay, and Fig. 6 is a general ground fault direction relay calculation method. This is a flowchart showing the following.

In general, a ground fault direction relay includes a current transformer 1, a transformer 2, an overcurrent protection relay 3, a direction discrimination relay 4, an overvoltage protection relay 5, an AND gate 6, a timer 7, etc., as shown in FIG. configured.

Current transformer 1 and transformer 2 detect zero-sequence current and zero-sequence voltage of the protection system, respectively. Overcurrent protection relay 3 and overvoltage protection relay 5 are connected to current transformer 1 and transformer 2.
Outputs are output when the zero-sequence current and zero-sequence voltage detected through each exceed a predetermined set value. The direction determination relay 4 determines the direction based on the product of the zero-sequence current detected by the current transformer 1 and the zero-sequence voltage detected by the transformer 2. For example, as shown in FIG.
The product of the zero-sequence current and the zero-sequence voltage is calculated in order to determine the direction of the zero-sequence current component I ₀ that has a predetermined phase ₀ relationship with the zero-sequence voltage indicated as V ₀ .

The AND gate 6 performs a logical product operation on the outputs from each of these relays 3 to 5, and when all of these outputs match, it outputs an output via the timer 7 to shut off a circuit not shown. , performs system protection operations.

As described above, the ground fault direction relay is constituted by three elements: the overcurrent protection relay 3, the overvoltage protection relay 5, and the direction determination relay 4.

The above is a case of a type of protection relay that does not use a calculation device, but in a protection relay equipped with a calculation device, the above-mentioned processing is realized by software calculation. In other words, as shown in Figure 6, the input current (zero-sequence current) and input voltage (zero-sequence voltage) taken in from the power system are digitally filtered (noise is removed, and at 50Hz,
Direction determination calculation is performed using the product of the input current and input voltage, ground fault overcurrent calculation is performed using the input current, and ground fault is performed using the input voltage. The overvoltage calculation is performed, and the earth fault direction relay calculation is performed as a whole.

By the way, in order to perform such calculations, it is necessary to sequentially sample the grid input (current, voltage) at a sampling period synchronized with the grid frequency to obtain each sample value of zero-sequence current and zero-sequence voltage. , the sine wave input, which is the system input, is exclusively
A method is used to obtain sample values by sampling every 90 degrees.

The former is called the 30-degree sampling method, and the latter is called the 90-degree sampling method.Since calculations are performed to obtain values equivalent to the average value and effective value of the system input, respectively, they are also called the average value calculation method and the effective value calculation method. FIG. 6 shows an example of the former, which is activated every 30 electrical degrees. Incidentally, since 30 electrical degrees is a (1/12) cycle, if the system frequency is 50Hz, every 30 electrical degrees means every (5/3) = 1.6 mS.

[Problem that the invention seeks to solve]

As mentioned above, the ground fault direction relay calculation shown in Figure 6 is based on the 30 degree sample type (average value calculation type).
This is a protection relay calculation of , and all the calculation processes of ~ are executed in series along the same processing system started at one startup timing, so it is a protection relay calculation of single input type. By comparison, approximately three times as much computation processing time is required.

Furthermore, such protection relay calculations are performed many times depending on the number of protection systems and the number of their phases, and the protection relay calculations for each phase as shown in FIG. 6 are completed within one sampling period. Therefore, if you try to increase the number of systems or phases to be protected, you will need a large-capacity computing device, which will increase the cost. If we use an inexpensive arithmetic device,
There is a problem in that the number of systems and phases that are subject to protection is decreasing.

The present invention solves the problems of the prior art described above, and provides a method for executing protection relay calculations that can increase the number of systems and phases to be protected while using a relatively small-capacity and inexpensive calculation device. The purpose is to provide.

[Means to solve the problem]

In order to achieve the above object, the present invention detects and processes the zero-sequence current and zero-sequence voltage of the power system at different timings to obtain the zero-sequence current value and the zero-sequence voltage value, and also detects the zero-sequence current value and the zero-sequence voltage value. calculate the product with the phase voltage value, perform a ground fault overcurrent relay calculation based on the zero-sequence current value, a ground fault overvoltage relay calculation based on the zero-sequence voltage value, and a direction determination relay calculation based on the product, and perform each calculation. When all of the following are true, the earth fault direction relay computation is established and an output is generated.In the protective relay computation execution method, the process of detecting the zero-sequence current to obtain the zero-sequence current value and then returning is performed at 90 degrees. a first processing loop that is repeatedly executed with an electrical angle period of 60 in electrical angle for every other time of the first processing loop that repeatedly executes the process of taking in, calculating the product of the zero-sequence current value and the zero-sequence voltage value, and then returning. a second processing loop that starts at a timing with a phase shift of 180 degrees and is repeatedly executed with an electrical angle period of 180 degrees; After taking in the zero-sequence current value in the processing loop 1 and calculating the product of the zero-sequence current value and the zero-sequence voltage value, from the entire relay calculation of ground fault overcurrent, ground fault overvoltage, and direction determination 60 in electrical angle for the remaining every other loop of the first processing loop, which performs the ground fault direction relay calculation and then returns.
Start at a timing with a degree phase shift,
We proposed a method for executing protection relay calculations that includes a third processing loop that is repeatedly executed with an electrical angle period of 180 degrees, and , as one phase.

[Effect]

According to the present invention, in the ground fault direction relay calculation, whereas conventionally it was executed at an electrical angle cycle of 30 degrees, it is executed at an electrical angle cycle of 180 degrees. can be reduced to (1/6) that of the conventional one. In addition, in the current detection process, voltage detection process, and arithmetic process for calculating the product of current and voltage, in the present invention, the required processing time or processing content is determined by the period of 30 degrees electrical angle, since the processing is executed at an electrical angle cycle of 90 degrees. This can be reduced to (1/3) compared to conventional methods.

In other words, it becomes possible to use a computation device with a smaller capacity and lower cost, or if the same computation device is used in terms of capacity and cost,
Accordingly, the number of strains and phases that can be protected can be increased accordingly.

〔Example〕

FIG. 1 is a flowchart showing one embodiment of the present invention, and FIG. 2 is a timing chart showing execution timings of various operations in the embodiment of FIG.

Please refer to FIG. In this embodiment, there is a processing loop A that only executes the process of sampling and taking in the zero-sequence current from the grid, a process of sampling and taking in the zero-sequence voltage from the grid, and a processing of the zero-sequence current taken in by the processing loop A. The process of calculating the product with the zero-sequence voltage taken in, followed by the process of calculating the ground fault direction relay,
, a processing loop (C and D) that executes processing, a process of sampling and taking in the zero-sequence voltage from the system, and a process of calculating the product of the zero-sequence current taken in in the processing loop A and the zero-sequence voltage taken in in the process. The protection relay calculation is executed separately in the processing loops (C and E) to be executed.

Previously, the processes of ~ were executed serially in one processing loop, which was repeated every 30 electrical degrees, resulting in a heavy processing load and a long processing time. In the example, it is divided into processing loop A, processing loop (C and D), and processing loop (C and E), and processing loop A is electrical angle
We decided to execute the processing loops (C and D) and the processing loops (C and E) at a period of 90 degrees, and each of the processing loops (C and E) at a period of 180 electrical degrees, so the processing load was light and the processing time required was also reduced. It's getting shorter.

Although processing loop B and processing loop E (particularly processing loop B) are illustrated as loops in FIG. 1, they are actually idle and do not seem to have any meaning in this embodiment. (Actually, that's true).

However, while this embodiment targets one phase, it is possible to protect multiple targets (multiple systems, polyphase) and make the flowcharts of each protection target symmetrical (identical) and combine them with each other. Then,
When attempting to give the same processing load to the four processing loops A, B, (C and D), and (C and E), processing loops B and E, which are idle in FIG. 1, become effective. An embodiment in this case will be described later with reference to FIG. 3, but the processing loop B is not necessary for one phase.

Referring again to FIGS. 1 and 2, this embodiment will be specifically described below.

In FIG. 1, processing route A is repeatedly executed with an electrical angle period of 90 degrees by the switching operation of the ring counter. Also, the processing route (C and D in series) is repeatedly executed with an electrical angle period of 180 degrees, but the processing route A
, which is executed repeatedly with an electrical angle period of 90 degrees (that is, every other processing route A), starts at a timing that is 60 degrees out of phase in electrical angle. Switching between the ring counter and the ring counter functions.

The processing route (C and E in series) is also repeatedly executed with an electrical angle period of 180 degrees, but while the processing route A is repeatedly executed with an electrical angle period of 90 degrees, The ring counter is set so that it starts at a timing that is 60 degrees out of phase with respect to the remaining every other process (that is, the remaining every other process route A that was previously taken every other process). Switching works.

Next, a more specific explanation will be given with reference to FIG. 2.

Now, if the zero-sequence current of the grid is leading the zero-sequence voltage by 60 degrees (when the maximum sensitivity angle is 60 degrees;
Consider the case of ₀ = 60 degrees in the figure. At this time, if the current and voltage of the grid are in phase and are expressed as shown in Figure 2 A, and if the digital filter calculation of the input current is performed on route A at the timing shown in Figure 2 C, then the input voltage The digital filter computation and current/voltage product computation (direction determination computation) are executed on route C, which is 60 electrical degrees later than route A, at the timings shown in FIG. 2B and D.

In addition, in the current/voltage product calculation (direction determination calculation), the current current data V _o and the past current data i _o-2 for 60 degrees (already obtained in processing loop A, so it is necessary to import it. The product is calculated, and data for the direction determination relay calculation is created. The current obtained in this way,
Based on the voltage and current/voltage product data, ground fault direction relay calculations, including ground fault overcurrent relay calculation, ground fault overvoltage relay calculation, and direction determination relay calculation, are performed at the timings shown in Figure 2 E, F, and G. .

In other words, in Figure 1, A→B→C(D)→A→B
→C(E) The calculation is repeated by the route D, and the earth fault direction relay calculation shown by , is performed at a cycle of 180 electrical degrees, so the Compared to the conventional method of performing relay calculations every 30 degrees, the reduction is approximately 1/
The processing load can be reduced to 6 processes.

FIG. 3 is a flowchart showing another embodiment of the present invention.

As described above, according to the embodiment shown in FIG. 1, the processing time or processing content required for one ground fault direction relay calculation can be reduced to approximately 1/6 of that of the conventional method. On the contrary, if the required processing time is the same, six protection relay calculations are possible, and from this point of view,
FIG. 3 shows an embodiment in which six protection relay calculations are executed.

In other words, 6 current calculations ~ and 6 voltage and direction determination (current/voltage product) calculations ~
As shown in the figure, the respective processing routes X, Y,
At the same time as placing it in Z, also place a ring counter ~.

Comparing FIG. 1 and FIG. 3, it will be seen that processing routes B and E, which seemed meaningless in FIG. 1, are effectively and appropriately used. In Fig. 3, if we pay attention to the execution route (, 〓〓, (55)) of the protection relay calculation for one phase for relay 67F ₁ , we can see that it is exactly the one shown in Fig. 1. I understand. The execution route for one phase as shown in Fig. 1 is the relay _67F1 to _67F6.
Figure 3 is constructed by combining six phases.

FIG. 7 is a timing diagram for explaining the calculation timing of the embodiment shown in FIG. 3. The calculation routes X, Y, and Z are It is performed at a sampling interval of 30 electrical degrees and an electrical angle period of 90 degrees, and each fault direction relay calculation 67F ₁ to 67F ₆ is performed at a sampling interval of 30 electrical degrees and an electrical angle period of 180 degrees.

By doing this, current calculations, voltage calculations, and current/voltage product calculations related to other relays will increase for calculation routes X, Y, and Z for every 30 electrical degrees (for example, for route X, will increase). , the advantage of allowing approximately six times as many protection relay operations as compared to the embodiment shown in FIG. 1 is brought about. Note that although the operating time (return) is slightly inferior to the conventional method shown in FIG. 6, it can sufficiently cope with the limit of 50 mS.

〔Effect of the invention〕

According to the present invention, by sequentially performing various calculation processes in parallel instead of serially, the required processing time can be reduced to about 1/6 of the conventional one when considering earth fault direction relay calculations. Not only can the burden be reduced, but if the arithmetic unit is left as is, the number of systems to be protected can be increased, providing the advantage of expanded protection functions.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention, FIG. 2 is a timing diagram for explaining various calculation timings in the present invention, and FIG. 3 is a flowchart showing another embodiment of the present invention. Figure 4 is a block diagram showing the general configuration of a ground fault direction relay.
Fig. 5 is a characteristic diagram showing the phase characteristics of the ground fault direction relay, Fig. 6 is a flowchart showing a general ground fault direction relay calculation method, and Fig. 7 explains the calculation timing of the embodiment shown in Fig. 3. FIG. Symbol explanation, 1...Current transformer, 2...Transformer, 3...
...Overcurrent protection relay (OCG), 4...Direction discrimination relay (DG), 5...Overvoltage protection relay, 6...
And gate, 7...timer.

Claims (1)

[Scope of Claims] 1. Zero-sequence current value and zero-sequence voltage value are obtained by detecting and processing the zero-sequence current and zero-sequence voltage of the power system at mutually different timings, and the zero-sequence current value and the zero-sequence voltage value are and performs a ground fault overcurrent relay calculation based on the zero-sequence current value, a ground fault overcurrent relay calculation based on the zero-sequence voltage value, and a direction determination relay calculation based on the product, and all of the calculations are satisfied. In the method for executing the protective relay calculation that generates an output when the earth fault direction relay calculation is established, the process of detecting the zero-sequence current to obtain the zero-sequence current value and then returning is performed at an electrical angle of 90 degrees. a first processing loop that is repeatedly executed with a period; and after detecting the zero-sequence voltage to obtain a zero-sequence voltage value, capturing the zero-sequence current value obtained in the first processing loop; The process of calculating the product of the zero-sequence current value and the zero-sequence voltage value and then returning is performed every other time in the first processing loop, with a phase of 60 degrees in electrical angle. a second processing loop that starts at a staggered timing and is repeatedly executed with an electrical angle period of 180 degrees; and after detecting the zero-sequence voltage and obtaining a zero-sequence voltage value, the first processing After taking in the zero-sequence current value obtained in the loop and calculating the product of the zero-sequence current value and the zero-sequence voltage value, ground fault overcurrent, ground fault overvoltage,
The above-mentioned ground fault direction relay calculation consisting of the entirety of the relay calculations for relay calculation and direction determination is performed, and then the process of returning is repeated for the remaining every other processing loop of the first processing loop. in the corner
Start at a timing 60 degrees out of phase,
A method for executing a protection relay operation, comprising: a third processing loop that is repeatedly executed with an electrical angle period of 180 degrees; and at least the following for one phase.