JPH0572164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for executing calculations for protection relays (also simply referred to as protection relay calculations) in a protection relay system that protects an electric power system.

[Conventional technology]

FIG. 4 is a block diagram showing the configuration of a general protection relay, and FIG. 5 is a flowchart showing a general protection relay calculation method.

This type of protection relay, for example, as shown in FIG. 4, is composed of a filter 11, a high setting relay 12, a low setting relay 13, cooperative timers 14, 15, an OR gate 16, and the like.

That is, the filter 11 extracts only a desired frequency component (for example, 50 Hz) from the input (current) of the power system detected via the current transformer CT. The high setting relay 12 operates when the current drawn through the filter 11 exceeds its set value (high setting value meaning a high current value), and controls a coordinated timer 14 which produces an output after a relatively short time limit. drive

The low setting relay 13 operates when the current taken in through the filter 11 exceeds its set value (low setting value meaning a low current value) and controls a coordinated timer 15 which produces an output after a relatively long time limit. drive

Thus, the OR gate 16 generates an output in a relatively short period of time (for circuit breakage, not shown) when the power system input (current) detected via the current transformer CT exceeds a high setting value. When the input (current) of the power system exceeds a low set value, output is generated for a relatively long time period, and a two-stage reverse time protection operation is performed.

This is the case of a protection relay that does not use a calculation device, but in a protection relay that includes a calculation device, the above-mentioned processing is realized by software calculation. That is, as shown in FIG. 5, after digital filter processing is performed on the system input (current) (reference), the detection calculation (effective value calculation) of the input (electricity) amount is performed (reference), Thereafter, a two-stage time limit protection relay calculation including comparison with the high setting value and the low setting value of the input amount is performed (see).

By the way, in order to perform such a detection calculation of the amount of input (electricity), it is necessary to obtain sample values by sequentially sampling the grid input at a sampling period synchronized with the grid frequency. A sine wave input that is a cycle, electrical angle 30
A method is used that uses sample value data obtained by sampling every 90 degrees. The former is 30
The latter is called the 90-degree sampling method, and since each sample value data is used to calculate the average value and value equivalent to the effective value of the system input, the average value calculation method and the 90-degree sampling method are called the 90-degree sampling method. Also called method.

Note that FIG. 5 shows an example of the latter, which is activated every 90 electrical degrees in one cycle of system input. Incidentally,
Since 90 degrees of electrical angle corresponds to 1/4 cycle, if the system frequency is 50Hz, every 90 degrees of electrical angle is
This means that every 5mS. In other words, what is shown in Fig. 5 is a 90-degree sample type (effective value calculation type) protection relay calculation method, and all calculations (digital filter processing calculation, input amount detection calculation, and protection relay calculation) are performed in the same way. It can be said that it is started at one startup timing and executed in a serial format.

Note that this calculation is performed a corresponding number of times depending on the number of protection systems to be protected and the number of phases thereof, and the calculation for each phase as shown in Fig. 5 is performed once per cycle of each phase waveform. It is necessary to complete the sampling period within one sampling period, which occurs at a rate of .

[Problem that the invention seeks to solve]

However, since there is a limit to the processing capacity (speed) of the arithmetic device that performs the protection relay calculation, there is a limit to the number of power systems that can be monitored (objects of the protection relay calculation). For example, if a microcomputer is used as the arithmetic unit, the protection system is 3-phase, and only an overcurrent relay is installed, 10 to 10 systems (30 to 50 phases) is the limit considering the processing capacity of the microcomputer. .

In reality, not only overcurrent relays but also various protection relays such as distance relays, ground fault direction relays, and differential relays are implemented, so the number of systems that can be monitored becomes even smaller (several to 10 systems). degree).
In other words, if a protection relay calculation is to be performed with a large number of systems to be monitored, a correspondingly large-capacity calculation device will be required, resulting in high costs. On the other hand,
If a relatively small capacity and inexpensive arithmetic unit is used, there is a problem that the number of systems that can be monitored will be reduced.

The present invention solves these problems and provides a protection relay calculation execution method that makes it possible to perform protection relay calculations on a large number of systems to be monitored while using a relatively small-capacity and inexpensive calculation device. The purpose is to

[Means for solving problems]

In order to achieve the above object, in the present invention, a low setting value and a high setting value are set as setting values for the digital protection relay, and the amount of electricity taken in from the power system is larger than the low setting value and lower than the high setting value. When it is small, the protective relay is activated if the state continues for a relatively long time, and when the amount of electricity is larger than the high setting value, the protective relay is activated if the state continues for a relatively short time. In a method for performing a step-type inverse-limit protection relay calculation in which the protective relay calculation is performed depending on the amount of electricity taken in from the power system, the amount of electricity taken in from the power system is one cycle of the system input. The first sample data obtained by processing the first sample data at a certain first timing
and second processed data obtained by processing second sample data at a second timing different from the first timing in the system input (for example, a sum of ), the first sample data is obtained and processed by starting at the first timing.
a first execution route that ends after obtaining processing data; and a first execution route that starts at the second timing, obtains and processes second sample data, and executes the second execution route.
processing to obtain the processed data, and then importing the first processed data obtained in the first execution route,
A process of calculating an amount of electricity as a calculation result between the first processed data and the second processed data (for example, the sum of the first processed data and the second processed data), and then calculate the amount of electricity. a second execution route that terminates if the former is not greater than the latter as a result of the determination, and the second execution route in the determination process, if the quantity of electricity is larger than the constant K, a third execution route of proceeding to the protection relay calculation at the step-shaped inverse limit and waiting for the completion of the protection relay calculation, and then terminating the calculation; did.

[Effect]

For example, when executing a 90-degree sample type (effective value calculation type) protection relay calculation, some calculations for digital filter processing and input electricity amount detection are performed in the first execution route, and in the second execution route. , the remaining calculations for detecting the amount of input electricity, and the process of determining whether or not to enter the protection relay calculation (if it is determined to enter, the process of subsequently executing the protection relay calculation)
I do.

The first execution route and the second execution route are executed alternately at intervals of 90 electrical degrees. Compared to the conventional method of combining both routes at once and performing them each time, the processing (arithmetic) capacity of the computer is low.

Further, in the second execution route, depending on the result of the determination process, there is no need to enter the protection relay calculation, so the processing load is reduced (compared to the conventional method in which the protection relay calculation is executed every time).

〔Example〕

FIG. 1 is a flowchart showing one embodiment of the present invention. Figure 2 shows data processing start timing (startup timing of the first execution route that performs some calculations for digital filter processing and input electricity quantity detection), judgment calculation start timing (input electricity quantity detection start timing), The remaining calculations for the calculation and the process of determining whether or not to enter the protection relay calculation (if it is determined to enter, the process of subsequently executing the protection relay calculation)
(startup timing of the second execution route),
FIG.

In Figure 1, START→→→
If the RETURN route is the first execution route, then START→→→→→→→
The RETURN route is the second execution route,
The third execution route is branching from →→OR→→RETURN and branching from →OR→→RETURN.

Timing switching has a so-called ring counter function that sequentially switches the program execution route between the first execution route and the second execution route in the order of A → B → A → B for each startup command. For example, in response to a 50Hz input from the system to be protected, it is activated every 5mS, which is an interval of 90 degrees in electrical angle.

As a result, there are two main programs (first
execution route and second execution route).
Each program will be activated every 10mS (180 degree samples). In other words, the input data processing that belongs to the second execution route and the input data processing that belongs to the first execution route are performed in a timing relationship as shown in Fig. 2B, that is, at timings with an interval of 5 mS from each other. , the detection calculation (determination calculation) of the input electric quantity (effective value) as shown in FIG. 2C is possible. In the determination calculation, the result β obtained from input data processing belonging to the first execution route is taken in, and the result α obtained from input data processing belonging to the second execution route is taken in.
Find the sum (ED). The value of this sum becomes the input electrical quantity (in this case, the effective value). Note that FIG. 2A shows the system input waveform.

Here, if we consider a steady state without a system failure (a state in which the protective relay calculation does not work), the relay output of the process belonging to the second execution route is "present",
Both judgment boxes for whether the operation flag is present will be “NO” (the operation flag will be explained later).
Data processing is performed to take in the current value _io of the system input at the current time and obtain ( _io ) ² .

Then, add (i _o-3 ) ² to this value obtained by the process belonging to the first execution route 5 mS ago, i.e. from the current time.
The square value of the current value i _o-3 of the grid input 5 mS ago is added, and the sum (that is, the effective value ED of the grid input current) is
is calculated (judgment calculation process). The timing at which this determination calculation process is performed is the timing shown in FIG. 2C.

Next, this effective value ED and the low setting value K are compared (processing), but since we are assuming a steady state, the judgment result is "NO".
RETURN and return to the start. Conventionally, protection relay calculations were performed every time even in a steady state, but here we aim to reduce the amount of processing by only processing data and comparing with the low setting value and not moving to protection relay calculations. It's on.

Next, processing operations when a system accident occurs will be explained. In this case, in the judgment process that follows the judgment calculation, it is normal that the effective value ED becomes larger than the low setting value K and the judgment is YES, so the process proceeds and the operation flag is set. Subsequently, the effective value detection type protective relay calculation module is activated via OR, and the protection relay calculation is executed. The actual value detection type protective relay calculation module is a two-stage time-limit protection relay calculation that performs high setting relay calculation in parallel with low setting relay calculation.

In addition, low setting relay calculation is a calculation in which when the effective value ED of the grid input current exceeds the low setting value and this state continues for a relatively long time, the relay is then operated to interrupt the grid. High-setting relay calculation is a calculation in which when the effective value ED of the system input current exceeds the high-setting value and this state continues for even a relatively short period of time, the relay is then operated to disconnect the circuit.

If the effective value detection type protective relay calculation module is started, once RETURNed, and then comes to judge whether the relay output is present for the processing of the second execution route, if the protective relay is operating by the function of the module. , (the relay output is in the "present" state), so the judgment is "YES", the process proceeds to reset the operation flag, and the
It will be possible to respond to the expected return after that.

On the other hand, if the protection relay was not operating, the determination of relay output "present" would be "NO" in the process, and in this case, the system would not be disconnected yet. Therefore, the process proceeds to determine whether the operation flag is set, and if the operation flag is set, the process proceeds to step via OR to continue the operation of the effective value detection type protection relay calculation module. Such a state is repeated in the effective value detection type protective relay calculation module until either the low setting relay calculation or the high setting relay calculation is accomplished and a relay output is generated.

According to such an execution method, the high setting relay calculation or the low setting relay calculation of the effective value detection type protection relay calculation module is executed when the transition to the protection relay calculation is determined in the determination process. and only when it is determined in the process that the operation flag is set. Normally (when the system is normal), it is determined that the operation flag is not set in the process, so the process
, only the processing (calculation) of whether to proceed to the protection relay calculation is performed.

Conventionally, a certain amount of program processing time was required to execute the protection relay calculation regardless of whether there was an accident in the grid or not, but according to the present invention, when a fault occurs in the grid, the determination process is determined to be YES. Therefore, it is the same as before in that it requires a certain amount of program processing time after that, but in the event of a non-fault in the system, the determination process will be determined as NO.
The program processing time required to execute protection relay calculations can be reduced to about 1/3 of the conventional time.

FIG. 3 is a flowchart showing another embodiment of the present invention. In the figure, if 3a corresponds to the process performed in the second and third execution routes in Figure 1 (hereinafter, for convenience, the entire process will be referred to as α processing), then 2a corresponds to the process performed in the first execution route. This corresponds to the processing performed (hereinafter referred to as β processing for convenience). α processing 3a and β processing 2a target relay A.

In addition to relay A, if there are relays B, Y, and Z to be calculated, then in Fig. 3, 3b
corresponds to α processing (targeting relay B), and 2
b corresponds to β processing (targeting relay B).
Similarly, 3y is α processing (targeting relay Y)
2y corresponds to β processing (targeting relay Y), 3z corresponds to α processing (targeting relay Z), and 2z corresponds to β processing (targeting relay Z).

That is, for relay A, if α process 3a is in the second execution route and β process 2a is in the first execution route, for relay B, α process 3b is in the first execution route of relay A, β process 2b is in the second execution route of relay A, and so on, so that the first execution route and the second execution route of each relay are respectively symmetrical (i.e., the same) as a whole. It will be seen that processing and β processing are divided.

The reason why this is done will be explained below. In the embodiment shown in FIG. 1, one of the two programs (the first execution route and the second execution route) (the first execution route) only includes data processing, so there is a margin. .

Therefore, in the embodiment shown in FIG. 3, the protection relay modules 3a to 3z (so-called α processing) and the data processing modules 2a to 2z (so-called β processing) performed at the previous timing are alternately executed in the first execution. The processing time required for each of the two program routes is the same by placing them on the first and second execution routes and performing protection relay calculations alternately on the first and second execution routes every 10 mS. This means that the number of protection relay operations is multiplied.

In other words, it is impossible to imagine that all of the many protective relays placed in various systems would work at the same time, so conventionally, for example, 12 protective relays (3 for each system) were used within the processing time of the arithmetic unit. stand (3
phase), the limit was 4 systems), but
The present invention attempts to demonstrate through the embodiment shown in FIG. 3 that it is possible to implement at least twice as many as 24 units (for 8 systems). If we assume that each system has three phases without considering simultaneous (all system) accidents, it will be possible to store 2 {2+3(n-2)}=4+6(n-2) units. However, n is the number of units in the conventional method. Conversely, considering the number n that can be accommodated using the conventional method, the fact that 4+6 (n-2) protection relays can be accommodated means that the processing time can be reduced accordingly.

In reality, there are various protection relay calculation modules, so it is not as simple as this, but it is certain that at least the number of protection relays that can be accommodated can be increased compared to the conventional method.

〔Effect of the invention〕

According to the present invention, data processing (corresponding to the above-mentioned β processing) and protection relay calculation (corresponding to the above-mentioned α processing)
By using a parallel execution route instead of a serial execution route and staggering the startup timing, the required processing time can be reduced to approximately 1/2 of that using the conventional method. ) or increase the number of protectable relays that can be accommodated.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention, FIG. 2 is a timing diagram showing the relationship between data processing start timing and judgment calculation start timing in the embodiment of FIG. 1, and FIG. FIG. 4 is a flowchart showing another embodiment of the invention, FIG. 4 is a block diagram showing the configuration of a general protection relay, and FIG. 5 is a flowchart showing a general protection relay calculation method. Description of symbols, 1...Protection relay, 11...Filter, 12...High setting relay, 13...Low setting relay, 14, 15...Coordination timer, 16...OR gate, CT...Current transformer.

Claims (1)

[Claims] 1. A low setting value and a high setting value are set in advance as setting values for the digital protection relay, and the amount of electricity taken in from the power system is larger than the low setting value and higher than the high setting value. When it is small, the protective relay is activated if the state continues for a relatively long time, and when the amount of electricity is larger than the high setting value, the protective relay is activated if the state continues for a relatively short time. As shown in the figure, in a method for performing a protection relay calculation in a step-type inverse limit, in which the protective relay calculation is performed depending on the amount of electricity taken in from the power system, the amount of electricity taken in from the power system is included in one cycle of grid input. The first sample data obtained by processing the first sample data at a certain first timing of
and second processed data obtained by processing second sample data at a second timing different from the first timing in the system input. When the first sample data is obtained and processed starting at the first timing, the first sample data is obtained and processed.
a first execution route that ends after obtaining processing data; and a first execution route that starts at the second timing, obtains and processes second sample data, and executes the second execution route.
processing to obtain the processed data, and then importing the first processed data obtained in the first execution route,
A process of calculating an amount of electricity as a result of calculation between the first processed data and the second processed data, and then compares the amount of electricity with a constant K representing the low setting value to determine the magnitude relationship. a second execution route that ends if the former is not greater than the latter as a result of the determination; and in the determination process in the second execution route, if the quantity of electricity is greater than the constant K; , a third execution route that transitions to the protection relay calculation at the step-shaped inverse limit and ends upon completion of the protection relay calculation.