JPH02246726A - Method of detecting monitoring failure of digital relay - Google Patents

Abstract

PURPOSE:To detect the defect of an intermittent mode arising from the semidefect of elements reliably by detecting the defect phenomenon at a frequency of occurrence in a specified period of time. CONSTITUTION:As a defective mode of each element including a semiconductor to constitute a protective relay there is a so-called semidefect in which the defective condition is intermittent in a short time. When no failure condition continues up to the set value of a confirming timer under such semidefect, no defect can be detected indefinitely by a standing monitoring. On that account, when either of monitoring items 11 is operated (the defect is detected), a timer 12 detects the occurrence frequency at not lees than a constant value and issues an alarm to outside. The defect caused by the semidefect of a component or by an intermittent mode can surely be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an automatic monitoring system for a protection relay device that protects an electric power system.

(Conventional technology) Automatic monitoring is an important feature for protective relay equipment.

Protection relays do not operate when the power grid is normal, but only operate when a fault occurs in the grid.

Therefore, it is absolutely necessary to avoid a situation where the protective relay itself has a failure and cannot operate when a system fault occurs. For this reason, the concept of automatic monitoring in protection relays was developed.

There are two modes of protection relay failure. That is, there are two modes: a mode that causes the relay to malfunction, and a mode that causes the relay to malfunction.

Detecting modes that lead to malfunction is relatively easy. The output of the protection relay can be constantly monitored and an alarm can be issued if the output continues for a certain period of time. Accidents that occur in power systems do not last long. Therefore, since the protective relay continues to output its operating output for a longer time than the maximum duration of an accident that can occur in the power system, it is determined that the protective relay has failed. This failure detection method is generally called "continuous monitoring." On the other hand, detection of malfunctions on the malfunction side is relatively slow because malfunction phenomena do not become apparent during normal times. ``Automatic inspection'' is necessary to detect this malfunctioning malfunction. For example, lock the protection function once every cycle, apply a simulated AC input similar to a system fault, and confirm that the protection relay responds correctly. This type of “constant monitoring” and “
Conventionally, protection relays have established a high degree of operational reliability through automatic monitoring, which consists of automatic inspections.

(Problems to be Solved by the Invention) FIG. 7 shows an average configuration of a digital relay. In the figure, 73 is an input converter, which receives the voltage of the power system from the instrument transformer 71 and the current port from the current transformer 72.
Convert it to a voltage signal of an appropriate size. 74 is an A/D converter that sequentially converts a plurality of analog signals output from the manual converter 73 into digital signals. 75 is the memory part and A of 74
/D converter output system voltage, current digital conversion data, etc. are stored. 76 is a calculation unit MPU, which is usually composed of a microcomputer. 77 is a memory (ROM) for storing calculation programs. 78 is an input interface (D/I) for importing external conditions.
The setting value of the protection relay is also read from this input ink face. 79 is the output ink face (Dlo)
A trip command to a 710 circuit breaker installed in the power system is also issued via this 79 output ink face.

Such digital relays are usually strictly monitored at all times. Regarding the constant monitoring method of digital relays, see Electric Kyodo Research (Volume 41, No. 4 “Digital Relay J
As it is explained in detail in Chapter 5), it will not be discussed in detail here, but some examples are as follows.

The A/D converter at 74 is monitored by applying a predetermined analog reference quantity to the input and verifying that the correct value is obtained as the output. The memory section of 75 is 711M P U
Predetermined data is written to the memory, and it is monitored to confirm that the same value is read. 77 program memory (RO
M) is the sum of all addresses of the stored memory code (
This is monitored by checking that the checksum) is a predetermined value.

Continuous monitoring of digital relays uses a confirmation timer to confirm that the above-mentioned monitoring failure continues for a certain period of time or more. The confirmation timer is generally set to about 10 seconds. Of course, it may be set longer or shorter than that. This confirmation time determines whether the malfunction that has occurred is due to a system fault or a malfunction due to a failure of a protective relay.

In recent years, many protection relays have been manufactured as digital relays that use microprocessors. Digital relays follow the method established in the analog relay era to identify a failure of a protective relay as a system fault using a confirmation timer, but improvements are expected in the following points.

(1) There is a so-called semi-failure in which the failure state of each element including the semiconductor that constitutes the protection relay is intermittent in a short period of time. In such a semi-defective state, if the failure state does not continue until the set value of the confirmation timer, the defect cannot be detected by constant monitoring forever. It goes without saying that semi-defective mode also exists in analog relays.

(2) Digital relays may inherently have a mode in which failures occur intermittently. For example, if a program is executed in a time-sharing manner, a failure may occur only at a specific calculation timing. Also, when the data is good, the data may be cleared and initialized using software. In such cases, failures may not be reliably detected using a method that detects the continuity of failures using a confirmation timer.

(3) Digital relays may perform monitoring using monitoring data separate from system data, so it is not necessarily necessary to confirm that a malfunction continues for a certain period of time to identify it as a system fault.

[Structure of the invention]

(Means for Solving the Problems) The present invention detects that the half-defective component or the defect that occurs in the intermittent mode described in the previous section occurs more than a certain frequency within a predetermined time, and determines it as a defect. It is something to do. Detecting the frequency of occurrence of a phenomenon has been difficult to achieve with analog circuits, but it can be easily achieved with digital relays using microcomputers. Furthermore, it is not necessarily appropriate in practice to find a one-off, non-reproducible failure and to alert the outside as a failure of the device.

(Function) As described above, by detecting failure phenomena at a frequency that occurs within a predetermined time, it is possible to reliably detect failures in intermittent mode caused by semi-defective elements or the like.

(Example) FIG. 1 shows the configuration of the present invention. In the figure, reference numeral 11 denotes a constant monitoring function section, which includes N various monitoring items. Although some of the details of the individual monitoring contents have been described, they are detailed in the above-mentioned Electric Kyodo Research (Vol. 41, No. 4, ``Digital Relay''), so they are omitted here. 12 is a timer according to the present invention;
When any of the 11 monitoring items operates (defective detection),
It detects that the frequency of occurrence is above a certain value and issues an alarm to the outside. The 12 timers can be implemented in both software and hardware.

Next, concrete implementation means of the 12 timers will be shown. FIG. 2 is a flowchart, in which calculations for the monitoring function are performed at 21. 22
Then, it is determined whether the monitoring results are good or bad. If it is good, the process goes to 23 and the counter value is decremented by n. However, when the counter value becomes negative, it remains at zero. If the result of step 22 is defective, go to step 24 and add M to the counter value. However, M
, n are positive integers, and M is greater than n. When the counter value exceeds P at 25, an alarm is issued to the outside as a monitoring failure at 20. When the counter value does not exceed P at 25,
Control ends without issuing an alarm to the outside. The operations in FIG. 2 are typically performed at regular time intervals. In FIG. 3, the operation of the flowchart shown in FIG. 2 will be explained. Here, as an example, the value of M is 10, the value of n is 1, and the value of P is 30.
shall be. In this case, when a monitoring failure is detected more than once in ten calculations, an external alarm is issued as a monitoring failure. Further, if a defect is detected less than once in 10 times, no alarm is issued. If the detection frequency of defects is extremely low and does not pose a practical problem, it is more convenient to continue operating the device without issuing an external alarm. Third
(a) in the figure shows a case where monitoring is determined to be defective. In this case, the defect detection frequency exceeds 1 in 10 calculations, leading to an external alarm being issued. (b) shows a case where monitoring is not determined to be defective. In this case, even if a defect is detected twice, the defect does not continue, so the counter value will eventually return to zero.

In the flowchart of FIG. 2, the count value in the case of failure is added and subtracted in the case of good, but the reverse is also true.

That is, the normal value is set to P, and when the counter value is defective, M is subtracted, and when the counter value becomes zero or a negative value, an external alarm is issued.

If there is no defect, the counter value is incremented by n, but P
Do not set it to a larger value.

FIG. 4 shows another embodiment. In the figure, at 21, calculations for the monitoring function are performed as in the previous example. At 42, the results of the monitoring calculations are stored in memory. The memory stores results for a certain amount of time in the past. 43, the past predetermined time TI
If it is determined to be defective M or more times during that period, an alarm is issued to the outside at step 26. If the number of times is M or less in T1 time, the calculation is terminated without giving an external alarm. The flowchart in FIG. 4 is also repeatedly executed at predetermined time intervals. FIG. 5 shows an example of the effect when M is set to 5 and T1 is set to 10 seconds in the calculation of FIG. 4.

(a) is an example where it is determined to be defective, and (b) is an example where the occurrence frequency is low and no external alarm is issued.

FIG. 6 shows yet another embodiment. In the figure, reference numeral 61 denotes a monitoring defect detection function, which, like 21 in FIG. 2, determines whether or not there is a monitoring defect at a constant calculation interval. 62 is a defect counter which issues an alarm to the outside when the number of defects exceeds a predetermined value M.

G3 is a flip-flop function, which becomes set when a monitoring failure occurs. 64 is a one-shot timer, which outputs an output for a certain period of time T2 when a monitoring failure occurs. 64
The output of the one-shot timer is connected to the 65 inverter, and the 65 inverter output becomes the reset input of the 63 flip-flop. Therefore, the 63 flip-flop is set when a monitoring failure occurs and reset 12 hours later. The reset output of the 03 flip-flop makes the count value of the 62 failure counter zero.

The function of the block diagram shown in Fig. 6 is to issue an external alarm as a monitoring failure when M times of placement failure are detected within 12 hours after the occurrence of the first monitoring failure. Do not give an alarm.

All of the embodiments described above can be implemented in both software and hardware.

〔Effect of the invention〕

The method for detecting when a failure of a digital relay device occurs more than a certain frequency has been described above. Conventionally, an alarm could not be issued to the outside unless the device became completely defective and the defective state continued for a certain period of time, but with the present invention, even semi-defects in which the defective state continues intermittently can be detected and an alarm is issued to the outside. It became so.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a flowchart for realizing a monitoring timer according to the present invention, FIG. 3 is a diagram showing the operation of the flowchart according to FIG. 2, and FIG.
5 shows the operation of the flowchart according to FIG. 4, FIG. 6 is a block diagram of another embodiment of the present invention, and FIG. 7 shows a conventionally used digital FIG. 2 is a block diagram of a relay. 11... Continuous monitoring function section 12... Timer 21
... Monitoring function calculation section 22 ... Defective judgment section 23.
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Claims (3)

[Claims] (1) Convert the AC amount of the power system into digital data,
In a digital relay device that protects a power system by arithmetic processing of the digital data, a monitoring failure detection method for a digital relay is characterized in that it detects that a device failure occurs more than a certain frequency and issues an alarm to the outside. method. (2) A counter is provided that adds or subtracts by M when a defect is detected, and subtracts or adds by n when no defect is detected, thereby detecting that defects occur more than a certain frequency. Monitoring failure detection method for the digital relay described. (3) The digital relay monitoring defect detection method according to claim 1, wherein the method detects that the defect has occurred a predetermined number of times or more within a fixed time from the time when the defect is first detected.