JPS6047818B2 - Digital phase comparison relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field The present invention relates to a phase comparison relay device, and in particular, the present invention relates to a phase comparison relay device, and in particular, to convert information -゛ to -゛, G4, V, ↓↓β-4-Y, D
) This invention relates to a digital phase comparison relay device using a digital arithmetic device such as a digital computer.

(b) Prior Art A phase comparison relay device has conventionally been used as a protective relay device for power transmission lines.

This phase comparison relay device includes a current phase comparison relay device for detecting internal faults in power transmission lines, and a device for detecting that the center of the step-out has passed through the protected system when the power system loses synchronization. There is a voltage phase comparison relay device. The current phase comparison relay method for detecting internal faults in power transmission lines is widely used, especially in the protection of ultra-high voltage power transmission lines, due to its simple judgment principle and high ability to distinguish between internal and external faults in two-terminal power transmission lines.

However, in recent years, with the advent of multi-terminal power transmission lines as power systems have become larger and more complex, current differential relay systems, which have a higher ability to identify internal and external faults, are being adopted. The current differential relay method uses the fault current itself as the operating amount, so
Although it has a high fault identification ability, it has not been used to protect long-distance power transmission lines because it requires the transmission of current information between remote points. Due to recent advances in transmission technology,
It is now possible to transmit the current information of each terminal in the protection zone by digital transmission after analog/digital conversion.
Current differential protection of long-distance power transmission lines is now possible. It is common for one channel of the micro line to be occupied for the transmission of such current information, that is, the transmission of the three current phases and the switching conditions of the circuit breaker. When using the current differential protection relay method described above to detect internal faults in power transmission lines, and also use the voltage phase comparison relay method to detect the passing of the center of synchronization within the same power transmission line, conventional voltage There is a method using a phase comparison relay device, and a method in which, like the current information, the voltage at each terminal in the protection interval is transmitted after analog/digital conversion, and the phase relationship of the voltage waveform at each terminal is determined from the voltage information.

In either of these methods, one channel of micro circuit must be used in addition to the information transmission for current differential protection, and a total of two channels of micro circuit must be used for one transmission line protection. must be used. In addition,
In the above explanation, the case where phase comparison protection and current differential protection are combined is illustrated, but there are also cases where phase comparison protection is combined with governor control, voltage control, etc. of a generator installed in a remote location. The same thing can be said. Incidentally, the amount of transmission in the case of generator governor control may be power information, and the amount of transmission in case of voltage control may be reactive power information. (The technology for transmitting power information and reactive power information to a remote location in this way is well known, for example, in Japanese Patent Application Laid-Open No. 103647/1983.) The phase information transmission means of the conventional phase comparison relay method described above did not take measures to reduce the amount of data transmitted, so when trying to transmit it in combination with protection/control information for other uses (current information for current differential protection, etc.), it is simply a matter of reducing the number of combinations. The disadvantage was that the amount of data transmitted increased accordingly.

If voltage phase information for voltage phase protection can be transmitted with a small amount of transmission, current information for current differential protection, which uses a large amount of transmission, can also be transmitted on the same transmission channel. (c) Object of the Invention The present invention has been made in view of this point, and an object thereof is to provide a digital phase comparison relay device capable of transmitting data for phase comparison protection with a small amount of data transmission.

(d) Structure of the Invention FIG. 1 shows an example of a protective relay system to which the present invention is applied.

In FIG. 1, a power transmission line 1 is a line to be protected, and connects electrical stations A and B via shield breakers 2A and 2B. At each terminal A, B, the current and voltage of the power transmission line 1 are introduced into the protective relay device RY via a current transformer CT and a voltage transformer PD. The protective relay device RY is composed of a digital arithmetic device such as a microcomputer. The current and voltage of the power transmission line introduced into the protective relay device RY are digitally encoded and transmitted to the other end via the communication device C and the micro line 3, while the current and voltage transmitted in the same way from the other end is Used together with information for protection calculations.
) The protective relay device RY performs current differential protection within the protection section of the power transmission line 1 and voltage phase comparison protection for detecting that the center of a synchronization passes through the protection section of the power transmission line 1.

In the present invention, digital encoding of phase information for phase comparison protection has an important meaning. FIG. 2 shows an example of an encoding circuit for digitizing phase information according to the present invention. AC quantity of electricity v whose phase is compared in Fig. 2
is a predetermined level K in the level detection circuit LD. The magnitude is compared with a predetermined level K. When it is larger, r1 is output, and when it is smaller, it outputs 10J. This level detection circuit L
The output
The AND condition is taken, and the output Y is led to, for example, a 3-bit counter COUNT. counter COUNT
counts the output Y of the AND circuit AND every predetermined period, and outputs the count results Sl, S2, and S3. The counter COUNT receives a reset pulse R every predetermined period.
E is received, and the count results Sl, S2, and S3 are reset. (e) Action FIG. 3 shows a time chart explaining the response shown in FIG. 2.

In FIG. 3, the same symbols as in FIG. 2 mean the same signals. The input (2) of the level detection circuit LD is at a predetermined level K. The magnitudes are compared and output X is obtained. The output x of the level detection circuit LD is ANDed with the clock CK to obtain an output pulse train Y. The pulse train Y is counted by a counter COUNT during a period T, and outputs Sl, S2, and S3 are obtained. The counter COUNT is reset at regular intervals T by a reset pulse RE. In Fig. 3, the number of pulse trains Y between time intervals is two, and the count result S
l, S2, S3 are obtained as (A), 1, 0), and similarly, 7 pulses are counted between time t1 and T2 (S
l, S2, S3) = (1, 1, 1), the number of pulses 4 between time Tn-1 and Tn is counted (Sl, S2,
S3)=(a), 0, 1) is obtained. That is, Sl,
S2 and S3 have respective weights of 1, 2, and 4 (SlXl
)+(S2×2)+(S3×4) clocks CK were present in the period T. As can be seen from this example, the counting results of the counter CO[JNT Sl, S2,
In S3, the input of the level detection circuit LD is set to a predetermined level K every predetermined period T. Represents a digitally encoded value of greater time. The phase information thus digitally encoded into just a few bits (three bits Sl, S2, and S3 in the example shown in Figure 2) can be easily used as part of the data transmission for the current differential protection described above. It is not necessary to use a special channel of the microwire for this phase comparison protection. FIG. 4 shows an example of a transmission format in which phase information Sl, S2, S3 for this phase comparison protection is incorporated on the transmission format for current differential protection. The transmission format shown in FIG. 4 is transmitted via the communication device every period T shown in FIG. As is clear from the figure, the transmission format example in Figure 4 is a frame synchronization word, a total of three phases of current data, a-phase, b-phase, and c-phase. It consists of an 0N-0FF word hoop for transmitting 0N-OFF information such as opening/closing conditions, and the phase information is transmitted through this 0N-OFF word hoop.
It is embedded in the word recorder and transmitted. Note that 0N-OFF
Fixed bit into word, G is phase information, C is 0N-O
The FF bit is a check bit and is provided to detect transmission errors during transmission. Based on the phase information thus transmitted as a digital code, the determining section can determine the phase of the input AC quantity V before being digitally encoded.

In other words, when (Sl, S2, S3) = (0, 0, 0) is transmitted, the input V is below the predetermined level Kg, and (Sl
, S2, S3)=(1,1,1), the input V is approximately above a predetermined level k. Furthermore, (Sl, S2, S
3) When phase information other than all ROJ or all 11 is transmitted, it is determined when the input V becomes higher than a predetermined level depending on the relationship with the signals Sl, S2, and S3 transmitted in the cycles before and after the phase information. You can tell whether it is tall or small.
For example, if a signal transmitted in a certain period is (Sl, S2, S3
) = (A), 0, 1), and the signal transmitted in the previous cycle is (Sl, S2, S3) = (0, 0, 0), then the input ■ is at level K. From smaller to K. Change to a greater extent, and that K. The timing of crossing is about 1 of the period T.
12 is detected. The period T is divided into eight equal parts by the clock pulse CT, and the signal (
Sl, S2, S3) = (0, 0, 1), the input V is at level K. This is because it means that four clock pulses CK occurred in the longer period. In this way, A,
In the protective relay device RY installed at both electric stations B, various phase characteristics are obtained by well-known phase comparison techniques using the voltage phase information (Sl, S2, S3) of the own end and the opposite end.

Some examples will be explained using FIG. 5. FIG. 5 shows the phase characteristics with the voltage ■9 at electric station A as a reference vector and the voltage ■B at electric station B as a judgment vector. In Fig. 5, the y characteristic, that is, the characteristic that operates when VB exists to the left of line y with respect to VA, is the phase information of the voltage at both ends, that is, each (Sl, S2, S3) signal at both electric stations A and B. By using
This phase determination principle itself is exactly the same as the phase determination principle of a well-known transistor relay. However, in the present invention, since the protective relay device RY is constituted by a digital arithmetic processing device such as a microcomputer as described above, the only difference is that this phase determination is processed by a program. Similarly, for the X characteristic in FIG. 5, the slice level K at both ends is determined using (Sl, S2, S3), that is, voltage phase information at both ends. The above phases are obtained by determining whether the leading phase is the delayed phase. (
f) Modification (f-1) In the above explanation, the voltage phase comparison protection relay system for the purpose of protection from synchronization was explained as an example. It goes without saying that the transmission method is not limited to the voltage phase comparison protective relay method, but can also be applied to the current phase comparison relay method, which has been frequently used as the main protection for power transmission lines.

(f-2) Also phase information, that is, a predetermined slice level K. The above time encoding becomes (Sl, S2, S3) 3
Although a bit signal is used, the present invention is not limited to this, and if it is necessary to transmit phase information with higher precision, a signal of 4 bits or more may be used (4 bits or more may be used). In contrast, if precision is not required, a 2-bit signal may be used. Although the above explanation did not mention the relationship between the constant period T and the period of the alternating current amount of electricity, the constant period T is used to ensure that the phase information of the alternating current amount of electricity is transmitted to the receiving end (the other end) without error. For this purpose, the instantaneous value of the alternating current quantity must be continuously maintained at a predetermined level K.
It is sufficient that the time interval is set such that there is at least one period in which the amount of alternating current electricity is equal to or more than O (or less than O) in one cycle of the alternating current electricity quantity.

(f-3) Although two of the phase characteristics according to the present invention, the X characteristics and the y characteristics shown in FIG. It goes without saying that other arbitrary characteristics can be realized using the well-known phase comparison technique.

(f-4) Furthermore, in the text explanation, two-terminal power transmission line protection was explained as an example, but this number of terminals does not limit the present invention, and it goes without saying that it can be applied to a protection system with three or more terminals. .

Further, the example of the encoding circuit shown in FIG. 2 and the example of the transmission format shown in FIG. 4 are merely examples, and various modifications are possible. (g) Effects As described above, the present invention provides a protective relay device that uses a completely new means of transmitting phase information, and effectively utilizes limited transmission channels to determine the phase with just a few bits of signal. The biggest feature is that phase information for comparison protection can be transmitted.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a protective relay system to which the present invention is applied, FIG. 2 is a diagram showing an example of a phase information encoding circuit in the present invention, and FIG. 3 is for explaining FIG. FIG. 4 is a timing chart showing a transmission format for transmitting phase information, and FIG. 5 is a diagram showing an example of phase characteristics in a protective relay device of the present invention. RY...Protective relay device, C...Communication device, LD...Level detection circuit, COUNT...
···counter.

Claims (1)

[Claims] 1 In a device that protects the power system by transmitting phase information of the amount of alternating current electricity at each terminal of the protected section of the power system together with other information, and using at least the phase information of this transmitted signal, means for converting into a digital code a time period in which the amount of alternating current electricity is above (or below) a predetermined level within the time interval, and cyclically transmitting the digital code together with the other information at each predetermined time interval; , detecting means for detecting the timing at which the alternating current quantity of electricity crosses the predetermined level from a change in the phase information in the transmission signal, and comparing the outputs of these detecting means to determine the phase relationship of the alternating current quantity of electricity. The predetermined time interval is such that there is at least one period during which the instantaneous value of the alternating current quantity is continuously equal to or higher than (or below) a predetermined level during one cycle of the alternating current quantity. A digital phase comparison relay device characterized in that the time interval is set to .