JPS6028219B2 - Digital relay inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for a digital protective relay system (hereinafter referred to as a digital relay) that protects a power system using a digital computer.

The protection system only operates when an accident occurs in the power system, and can be said to be in a standby state where it only monitors the power system at all times.

Faulty protective relay equipment can cause malfunctions (for example, a Moh relay operates when an external fault occurs) or malfunctions (for example, a Moh relay does not operate when an internal fault occurs) due to a defective device when an accident occurs in the power system. ) shall not be present. For this reason, it is extremely effective to provide an automatic inspection function in the protective total electrical equipment layer and automatically inspect the device at regular intervals to identify any defects in the device in advance. Although there are various methods for automatic inspection, a method in which a check current is superimposed on the CT circuit is most effective in the sense of widening the failure detection range as much as possible.

FIG. 1 shows an example. In the figure, 1
1 is a current transformer (hereinafter referred to as C) connected to the power transmission line TL of the power system.
Reference numeral 12 denotes a potential transformer (hereinafter referred to as PT) connected to the bus line BUS of the power system, and transmits a current signal and a voltage signal of the power system to the protective relay 13, respectively. 14 is a cancellation CT for superimposing an inspection current.

Normally, the auxiliary relay 15 (not shown) is kept in an inoperative state, its normally closed contact 15b is closed, and its normally open contact 15a is kept open. Therefore, all of the power flowing in the secondary direction of CTII flows into the protective relay 13. During inspection, the auxiliary relay 15 (not shown) is operated to close its normally open contact 15a and open its normally closed contact 15b. Then, the current in the Ch circuit is canceled by the back electromotive force generated in the winding 14b of the canceling CT 14, and no longer flows into the protective relay 13. In this state, when the auxiliary relay 16 (not shown) is operated, its output contact 16a is closed, and the inspection power source 17 is applied to the winding 14, the inspection current flows to the protective relay 13 via the winding 14b and the contact 15a. By using the canceling CT in this way, a check current that is not affected by the power flow can be applied from the CT circuit to the protective relay 11,
Highly accurate automatic inspection becomes possible. The protective electrical equipment 13 to be inspected at this time can be applied not only to analog relays that are widely used in the industry, but also to so-called digital relays that use digital computers, which have been rapidly developed in recent years. . However, such an inspection method requires a canceling CT 14, an auxiliary relay, etc., and since contacts 15a and 15b are used on the secondary side of the canceling CT 14, in order to deal with problems in the CT circuit caused by defects in these contacts, It is necessary to take measures such as making the canceling CT have characteristics that easily saturate. In view of these points, the present invention aims to simplify the device by omitting the canceling CT in a digital relay inspection device, eliminates the influence of a defective auxiliary relay contact, and changes the inspection current due to power flow. The purpose of this invention is to provide a digital relay inspection device to eliminate the influence of

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block configuration diagram for implementing the present invention, and the same parts as in FIG. 1 are given the same reference numerals and the explanation thereof will be omitted.

CTI I and PT12 each supply current information and voltage information of power system TL to digital protection relay 23. In the digital protection relay 23, 231 and 232 are input converters, which convert the chord current and voltage introduced from the CTI 1 and PT 12, respectively, into voltage information of an appropriate size that is easy to process. Filters 2331 and 2332 introduce the outputs of the input converters 231 and 232, remove harmonic components, and output fundamental wave components.

234 is an A'D conversion circuit that converts analog quantities into digital quantities, which samples the outputs of filters 2331 and 2332 at predetermined intervals and converts them into digital data.

Therefore, this A/D converter 234 has a built-in sample and hold circuit. A direct memory access (DMA) circuit 235 writes the output of the A/D conversion circuit 234 to a predetermined address in the memory circuit 236.

237 is a central processing unit (CPU) that executes relay operations according to the program written in the program memory circuit (read-only memory RoM) 238 and using the data written in the data memory circuit 236. .

Reference numeral 239 is an output circuit that issues a command to remove the breaker and a display output based on the calculation results of the CPU.

Reference numeral 17 denotes a power supply for inspection, and during inspection, one inspection current is supplied to the power flow input IL at the input converter 231 of the digital protection relay 23 via the contact 16a of the auxiliary relay 16 (not shown).
superimposed on

FIG. 3 shows the state of data stored in the memory 236 during inspection of the digital relay configured as described above.

Note that the inspection time here refers to the period from when the inspection start command is issued until the inspection work is completed. In the figure, A is an inspection current, which is applied as a current IT to the primary winding of the input converter 231 from the inspection start time T (contact 16 on). B is the power flow of the system TL, and a constant current (power flow) IL flows regardless of whether before or after the inspection start time T.
The data memory section 236 in the digital relay stores the waveform of data in which the inspection current A and the current B are superimposed. The state of the waveform is shown in FIG. 3C. In Fig. 3C, if we focus on the data at time m Tm, the data i of C uses the data of A and B,
It is expressed as...'・I.

Here, in the '11 formula, icm is the data memory section 236
Although the value can be read from i^skin i8m, it cannot be read individually. Here, note that the waveform size of the current B does not change before and after the inspection start time T, and input the data sampling timing (for example, 50
Hz), and i before the inspection start time T.
Data iBm-NL from N cycles before Bm is stored in memory section 2.
Read from 36. In this case, it is clear that i8m=.BmN.L. Therefore, i^m=・skin−iBm, that is, 1^m=1ｽ−IBmN·L. As a result, the present invention can eliminate the influence of tidal current from the input during inspection. FIG. 4 is a flowchart showing an example of automatic inspection according to the present invention, which is executed by the CPU shown in FIG.

In this case, it is assumed that the illustrated data memory 236 stores a sufficient amount of excess tidal flow data. Fourth
In the figure, step 41 recognizes that the inspection has started. Step 42 stores sampling data of the power flow of one cycle in the past from the time when the inspection was started.

Step 43 provides a command to drive the auxiliary relay 24 through the output circuit 239 and applies a check input.

In step 44, the true inspection input current value i^ is obtained by subtracting the data iBm-N·L just N cycles ago from among the data stored in the data memory circuit 236 from the current data i^. get m.

In step 45, the true inspection input current iT value obtained in step 44 is used to calculate the amplitude value of the inspection input iT.

Various methods can be used to calculate the amplitude value, but one example is data i^m-3 (with a phase difference of 900 from i^m).
(assuming 300 samplings), it is obtained by the following equation. 11 AI2 = i mi m ten i house m - 3 ...(
2} In step 46, it is checked whether the value calculated in step 45 is within a predetermined range using the following equation, and if it is within the range, it is determined in step 47 that the inspection is good.

If it is outside the range, it is determined in step 48 that the inspection is defective.
IK 12>IIAI2>IK-12. ．．・．． ．．・
'3''3} In the formula, K is the predetermined magnitude of the inspection input, and ≈ indicates the allowable error.

According to the present invention, by canceling the influence of tidal current, any value can be reduced by 4, and therefore highly accurate inspection can be performed. Through the inspections shown above,
In FIG. 2, an input converter 231, a filter 2332
, A/D conversion circuit 234, direct memory access 235, and memory section 236 are subject to inspection.
Failures can be detected with extremely high sensitivity even when there is a slight change in data due to element failure or the like. Further, according to the present invention, the canceling CT 14 and the auxiliary relay 15 shown in FIG.
And the wiring part thereof can be omitted. In the above description, an example has been described in which a sufficient amount of past current data is stored in the data memory circuit 236, but the present invention is also fully applicable to a case where the amount of stored data is insufficient.
In other words, data for one cycle immediately before the inspection starts is stored in another area in the data memory circuit, and data with the same phase as the power flow at the time of inspection is extracted from among the stored data. By taking it out and canceling it, it is possible to cancel the current in exactly the same way as in the previous example. A flowchart in this case is shown in FIG. In Fig. 5, when the inspection starts at step 51, 52
In step , the current data of one past cycle is stored in a special area within the data memory circuit 236. In the next step 53, when the inspection input is applied as in the example in Figure 4, 5
In step 4, the inspection current data is canceled using the data stored in step 52. Since the steps from 55 onward are exactly the same as in the example shown in FIG. 4, their explanation will be omitted here, but even if the amount of data stored by this method is small, the present invention can be easily carried out as long as there is only one past cycle. Can be applied.

In the above example, the current characteristics of the digital relay were inspected, but as described below, the current characteristics and voltage characteristics can also be inspected.

FIG. 6 is a diagram showing another embodiment of the present invention, and the same parts as in FIG. 3 are given the same reference numerals, and detailed description thereof will be omitted.

In FIG. 6, the current and voltage of the system are introduced to the digital relay 23 by CTII and PT12. 19 is an actor that simulates the impedance of the system.

During inspection, the voltage input to the digital relay 23 is set to ST1 by closing the normally open contact 18a and opening the normally closed contact 18b.
2 to the voltage for inspection at both ends of the reactor 19. Assume that the digital relay 23 is programmed to obtain the characteristic shown in FIG. It is assumed that the reactor 19 is set in advance so that the impedance seen by the relay 23 is at point A in FIG. 7 based on the inspection current and voltage. When such an inspection input is given, it is checked whether the digital relay 23 operates or not. At this time, inspection point A is checked by using the current data with the power flow canceled according to the flowchart shown in Fig. 8. This makes it possible to keep the temperature close to the operating limit, allowing highly accurate inspections to be carried out. In Figure 8, 8
When it is recognized that the inspection has started in step 1, the auxiliary relay contact 16 is connected through the output circuit 239 in step 82.
a, 18a, and 18b are driven, and inspection input current and voltage are applied. In step 83, from among the data stored in the data memory circuit 236, the data iBm-N.L from just N cycles ago is subtracted from the current current data i, so that the embodiment shown in FIG. Similarly, the true inspection input current value i is obtained.

In step 84, the true inspection input current value and inspection voltage obtained in step 83 are used to calculate the Moh characteristic shown in FIG. 7.

In step 85, it is determined whether the calculation result indicates operation, and if it is operation, it is determined in step 86 that the inspection is acceptable. If it is not operating, it is determined in step 87 that the inspection is defective. Furthermore, in the above example, the application of the inspection current is superimposed on the input converter section using the inspection winding, but as shown in FIG. The present invention can be applied in exactly the same manner to the method of superimposing images in H.233.

As described above, according to the present invention, it is possible to perform inspections unaffected by currents without using a CT for canceling currents when inspecting digital relays, simplifying the downsizing of the device,
Great improvements can be made in terms of improving reliability.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a conventional protective relay layer, Fig. 2 is a configuration diagram showing an embodiment of the present invention, and Fig. 3 is a diagram showing how the inspection current and power flow are superimposed, and the preliminary power flow data. Figure 4 shows how the power flow component is canceled in the evening and the true inspection current is obtained.
The figure is a flowchart of one embodiment for carrying out the present invention, FIG. 5 is a flowchart of another embodiment, FIG. 6 is a diagram showing the configuration of another embodiment of the present invention, and FIG. Figure 8 is a flowchart of the embodiment shown in Figure 6.
FIG. 9 is a circuit diagram showing another example of the input converter. 1 1... Current transformer (CT), 23... Digital relay, 231, 232... Input converter, 234...
・・A/D converter, 236 ・・Data memory circuit, 2
37...CPU, 238...Program memory circuit, 2
39...Output circuit. Figure LIFigure 2Figure 3Figure 4Figure 5Figure 7Figure 6Figure 8Figure 9

Claims (1)

[Claims] 1. A power flow extracted from a power system is converted into a signal of a desired size by an input converter, and this signal is converted into a digital signal and then written into a data memory circuit. In a digital relay that performs a desired relay operation using data in the data memory circuit according to a programmed program, during an inspection period, an inspection current is superimposed on the power flow extracted from the power system and written in the data memory circuit, and A digital relay inspection device that subtracts power flow data written in the data memory circuit before application of inspection current from superimposed data. 2. In claim 1, after an inspection start command is issued, tidal flow data is written in a special area of a data memory circuit, and then a check current is superimposed on the tidal current data and written in the data memory circuit, and this superimposition is performed. A digital relay inspection device that subtracts the current amount written in the special area from the amount of current written in the special area. 3. The digital relay inspection device according to claim 1, wherein the input converter has a tidal current input portion, an inspection current input portion, and a common output portion. 4. In claim 1, the part that converts the power flow component of the input converter and the part that converts the input check current are magnetically separated, and the respective output electric quantities are combined by a filter. Features: Digital relay inspection device.