JPH10262327A - Differential protection relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make differential protection possible without adding an auxiliary transformer to the external portion of a relay by providing a particular constant multiplying means to a digital data obtained from an analog/digital converter circuit. SOLUTION: When a bit length of digital data to be transmitted to a remote terminal and a bit length of digital data of local terminal transmitted to the self-end is X, and a bit length of an analog/digital converter circuit is Y, then X<Y relation is maintained, and constant multiplying means 10A, 10B are provided which multiply a constant [1/(2<(y-x)> )×K/minimum sensitivity of differential protection relay 1A, 1B (K is constant)]. Those multiplied by the constant multiplying means 10A, 10B are transmitted to the remote terminal and differential protection operations are carried out by a judging section (PU) 19A, 19B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay device, and more particularly to a differential protective relay device for protecting a system by transmitting system electricity at both ends of a transmission line via transmission means. .

[0002]

2. Description of the Related Art FIG. 5 is a system configuration diagram of a conventional PCM differential protection relay device to which a digital transmission system is applied.
In FIG. 5, A and B are electric stations, and the transmission line 11 is a protection section.
Circuit breakers 12A and 12B are connected to both ends of the. The current at each end is taken by current transformers 13A and 13B at both substations and is introduced into differential protection relays 1A and 1B.

The currents taken into the differential protection relays 1A and 1B are converted into predetermined electric quantities by input converters 14A and 14B, and the electric quantities of unnecessary frequency components are removed through filters 15A and 15B. , Sampling and holding circuit (S /
H) Hold at 16A and 16B until next sampling.

The held electric quantities are converted into digital data by analog / digital converters (A / D) 17A and 17B, and then are determined by decision units (PU) 19A and 19B.
Sent to B. The A / D outputs of the electrical stations A and B at both ends are transmitted to each other via signal transmission devices (CCs) 18A and 18B, respectively, and are determined by the determination units (PUs) 19A and 19 of the respective terminals.
Sent to B.

The bit lengths of the digital data transmitted to the partner terminal, the digital data of the partner terminal transmitted to the own terminal, and the digital data output from the analog / digital conversion circuit are the same. Judgment unit (PU) 19
A, the 19B, determines the presence or absence of fault current flowing into the protected section transmission lines using A substation current data I _A and B substation current data I _B.

[0006] The judgment result is output as a trip command to the circuit breakers 12A and 12B. This determination is the current data I _A, it is carried out by (1) as an example with reference to I _B. The characteristics in the horizontal axis _{Σ | I | = | I A} | + | I B |, the longitudinal axis _{| I d | = | I A} + I B | take, ends data I _A
When the phase difference between I and I _B is kept constant, for example, at 180 degrees, the ratio characteristic as shown in FIG. 6 is obtained.

| I _A + I _B | ≧ K1 (| I _A | + | I _B |) + K 0 · Minimum sensitivity ············ (1) (K 0 and K 1 are constants)

As shown in FIG. 7, the input converters 14A and 14B have a switching circuit 71 for switching the conversion ratio, and the switching circuit sets the minimum sensitivity of the differential protection relay to "0.5".
A, 1.0A, 1.5A, 2.0A ".

For example, the minimum sensitivity viewed from the transmission line is 800
Assuming that A, the conversion ratio of the current transformer at the substation A is 8000/5
, The minimum sensitivity of the differential protection relay at the substation A is 0.5
When A (800A × 5/8000) is selected and the conversion ratio of the current transformer at B substation is 4000/5, the minimum sensitivity of the differential protection relay at B substation is 1.0A (800A × 5/400).
Select 0).

[0009]

In the system in which the minimum sensitivity is switched by the switching circuit as described above, differential protection may not be possible depending on the conversion ratio of the current transformer. For example, as shown in FIG.
Assuming 0A, the conversion ratio of the current transformer at the A substation is 8000 /
In the case of 5, the minimum sensitivity of the differential protection relay at the substation A is 0.
5A (800A × 5/8000) may be selected.

However, the conversion ratio of the current transformer at the B substation is 600
In the case of 0/5, it is desirable to select the minimum sensitivity of the differential protection relay at the substation B of 0.667A (800A × 5/6000), but there is no corresponding minimum sensitivity of 0.667A in the switching circuit. Therefore, it was necessary to add an auxiliary transformer 81B having a conversion ratio of 3/4 outside the differential protection relay at the substation B.

If an auxiliary transformer is not provided externally as described above, a differential current flows when no accident occurs, so that differential protection cannot be performed. Also, in the case of the method of multiplying by 3/4 by software instead of providing an external auxiliary transformer, it is necessary to set the magnification in addition to selecting the minimum sensitivity of the differential protection relay, and the setting operation is complicated. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. By setting the minimum sensitivity of a differential protection relay by a continuous set value, a differential protection relay can be provided without adding an auxiliary transformer outside the relay. It is an object of the present invention to provide a differential protection relay capable of dynamic protection.

[0013]

According to a first aspect of the present invention, there is provided a differential protection relay device wherein each terminal current value of a power system is converted into a predetermined electric level by an input conversion unit and is sampled at a predetermined period. A sampling circuit for detecting the sampling data, an analog / digital conversion circuit for converting the sampling data into digital data, a transmission means for transmitting the digital data to a counterpart terminal, and an input of the minimum sensitivity of the differential protection relay. And a calculation circuit for performing a predetermined differential protection calculation using the digital data and the digital data of the partner terminal obtained at the partner terminal and transmitted to the own terminal via the transmission path. In the protective relay device, the bit length of the digital data transmitted to the partner terminal and the partner transmitted to the self-terminal. The bit length of the digital data for the child X, the bit length of the analog / digital converter Y
Assuming that (X <Y), the digital data obtained from the analog / digital conversion circuit has a constant [1 / (2
^(YX) ) × K / minimum sensitivity of differential protection relay (K is a constant)].

According to a second aspect of the present invention, a differential protection relay device detects sampling data by converting each terminal current value of a power system into a predetermined electric level by an input conversion unit, and sampling at a predetermined period. A sampling circuit for converting the sampling data into digital data, an analog / digital conversion circuit for transmitting the digital data to a partner terminal, a setting means for inputting the minimum sensitivity of the differential protection relay, A differential protection relay device comprising: a digital data and an arithmetic circuit for performing a predetermined differential protection operation using the digital data of the partner terminal obtained at the partner terminal and transmitted to the own end via the transmission path, The bit length of the digital data transmitted to the partner terminal and the digital data of the partner terminal transmitted to the own end. The bit length of over data X, when the bit length of the analog / digital converter and Y (X <Y), the analog / digital converter constant digital data obtained from ^{[1 / (2 (YX)} ) × K (K is a constant)].

In the differential protection relay device according to the first and second aspects of the present invention, the bit length of the digital data of the partner terminal transmitted to its own terminal is X, and the bit length of the analog / digital conversion circuit is X. Let Y (X <Y) be the constant [1 / (2 ^(YX) ) × K / the minimum sensitivity of the differential protection relay] or the constant [1 / ( 2 ^(YX) ) × K (K is a constant)].

By fixing the number of digits of the minimum sensitivity for any of the minimum current values, the quantization error at the minimum sensitivity can be kept constant and the matching with the partner terminal can be achieved. , Can be used as it is as data for differential protection.

According to a third aspect of the present invention, there is provided a differential protection relay device according to the first aspect, further comprising a filtering means for extracting a predetermined frequency component.

According to a fourth aspect of the present invention, there is provided a differential protection relay device according to the first aspect, further comprising means for setting the minimum sensitivity of the differential protection relay to a continuous value having a predetermined step width.

According to a fifth aspect of the present invention, in the differential protection relay device according to the first aspect, the sampling circuit and the analog / digital conversion circuit and the input conversion unit, the sampling circuit, and the analog / digital conversion circuit of another relay are provided. Equipped with means to share.

According to a sixth aspect of the present invention, there is provided a differential protection relay according to the first aspect, wherein when the differential protection relay is used as a main protection relay, an input conversion unit for retrofit protection is used as an input conversion unit of the main protection relay. There was a means to share.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a P according to a first embodiment of the present invention.
It is a lineblock diagram of an embodiment of a CM differential protection relay device. In this embodiment, the bit length of the digital data transmitted to the counterpart terminal and the bit length of the digital data of the counterpart terminal transmitted to the own terminal are X, and the bit length of the analog / digital conversion circuit is different from the conventional configuration. When Y is
There is a relationship of X <Y and a configuration in which multiplication means is added. In FIG. 1, the same parts as those in FIG.

As shown in FIG. 2, the input converters 14A,
14B does not have a switching circuit for switching the conversion ratio. 10A and 10B are constant multiplication means newly added in the present embodiment. As an example,
Here, the bit length X is 16 bits, and the bit length Y is 1
When it is 2 bits, the constant [1 / (2 ^(16-12) ) × K
/ Minimum sensitivity of differential protection relay (K is a constant)], the multiplied value is transmitted to the partner terminal, and the determination units (PU) 19A and 19B determine, for example, the determination formula (1) The differential protection operation is performed by

Next, the meaning of multiplying by a constant will be described. Since one of the 16 bits is assigned to a positive or negative sign, the magnitude of the electric quantity is 0 to 32768.
It can be represented by (2 ¹⁵ ) digit digital quantity. Since the input converters 14A and 14B have no switching circuit, the input full scale is constant.

For example, the input full scale 102.4
If the minimum sensitivity is 0.5 A and K = 2, the constant of the constant multiplying means is [1 / (2 ^(16-12) ). ^Times.K / the minimum sensitivity of the differential protection relay (K is a constant). ] = 1/16 × 2
/0.5=0.25. Therefore, the number of digits at the minimum sensitivity current of 0.5 A is 32768 digits ×
0.5A / 102.4A × 0.25 = 40 digits.

When the minimum sensitivity is 1.0 A and K = 2,
The constant of the constant multiplication means is [1 / (2 ^(16-12) ) × K
/ Minimum sensitivity of differential protection relay (K is constant)] = 1/16
× 2 / 1.0 = 0.125. Therefore, the digit number of the minimum sensitivity current of 1.0 A is 32768 digit.
t × 1.0A / 102.4A × 0.125 = 40dig
it.

When the minimum sensitivity is 0.667 A and K = 2, the constant of the constant multiplying means is [1 / (2 ^(16-12) ).
× K / minimum sensitivity of differential protection relay (K is a constant)] = 1 /
16 × 2 / 0.667 = 0.187. Therefore, the digit number of the minimum sensitivity current of 0.667 A is 32
768 digit × 0.667A / 102.4A × 0.
187 = 40 digits.

As described above, the digit number of the minimum sensitivity is fixed for any minimum current value. Minimum sensitivity d
By fixing the number of digits, it is possible not only to keep the quantization error at the minimum sensitivity constant, but also to match the current with the partner end, so that it can be used as it is as data for differential protection.

Since the conventional minimum sensitivity corresponds to the number of turns of the input converter, for example, "0.5A, 1.0A, 1.5
A, 2.0A ", but in the present invention, since the minimum sensitivity is set by the setting means, for example," 0.500A, 0.501A, 0.502A,...
., 2.000 A ".

For example, the minimum sensitivity viewed from the transmission line is 800
Assuming that A, the conversion ratio of the current transformer at the substation A is 8000/5
, The minimum sensitivity of the differential protection relay at the substation A is 0.5
When 00A (800A × 5/8000) is selected and the conversion ratio of the current transformer at B substation is 6000/5, the minimum sensitivity of the differential protection relay at B substation is 0.667A (800A × 5
/ 6000) enables differential protection.

According to the present embodiment, there is no need to add an auxiliary transformer outside the relay. Also, instead of providing an external auxiliary transformer, there is no need to set the magnification other than selecting the minimum sensitivity of the differential protection relay, as in the method of matching by software.

FIG. 3 is a block diagram showing an embodiment of the PCM differential protection relay device according to claim 2 of the present invention. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description will be omitted. The characteristic part of the present embodiment is a multiplication unit 10A.
Is set to [1 / (2 ^(YX) ). ^Times.K (K is a constant)], and the rest is the same as FIG. In the present embodiment, the same effect as described above can be obtained.

FIG. 4 is a block diagram showing an embodiment of a PCM differential protection relay device according to claim 3 of the present invention. 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description will be omitted. The feature of this embodiment is that a digital filter (DF) (41A) is added to FIG.

According to the present embodiment, by adding a digital filter means (DF), it is possible to remove the DC component included in the input current and reduce the quantization error after A / D conversion. Besides, it is possible to remove harmonics contained in the current.

Further, according to the present invention, the input converter, the sampling circuit and the analog / digital converter of the PCM differential protection relay and the input converter, the sampling circuit and the other converter of the other relays are eliminated because the switching circuit of the input converter is eliminated. An analog / digital conversion circuit can be shared, and hardware can be reduced, thereby simplifying hardware and improving reliability.

[0035]

As described above, according to the present invention, even when the conversion ratios of the current transformers at both terminals are different, not only the differential protection can be performed, but also the input current transformer of another relay can be protected. Sharing can be achieved, and hardware can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a PCM differential protection relay device of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of an input converter to which the present invention is applied.

FIG. 3 is a configuration diagram showing another embodiment of the PCM differential protection relay device of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the PCM differential protection relay device of the present invention.

FIG. 5 is a configuration example diagram of a conventional PCM differential protection relay device.

FIG. 6 is a ratio characteristic diagram of the PCM differential protection relay device.

FIG. 7 is an example of an input converter of a conventional PCM differential protection relay device.

FIG. 8 is an installation example diagram of an external auxiliary transformer of a conventional PCM differential protection relay device.

[Explanation of symbols]

 1A, 1B Differential protection relay 10A, 10B Constant multiplication means 11 Protection section Transmission line 12A, 12B Circuit breaker 13A, 13B Current transformer 14A, 14B Input converter (CT) 15A, 15B Filter (FIL) 16A, 16B Sampling Hold circuit (S / H) 17A, 17B Analog / digital converter (A / D) 18A, 18B Signal transmission device (CC) 19A, 19B Judgment unit (PU) 41A, 41B Digital filter (DF) 81B Auxiliary transformer

Claims (6)

[Claims] An input converter converts a current value of each terminal of a power system into a predetermined electric level, and performs sampling at a predetermined period to detect sampling data, and converts the sampling data into digital data. An analog / digital conversion circuit, transmission means for transmitting the digital data to a partner terminal, setting means for inputting the minimum sensitivity of the differential protection relay, and automatic transmission via the transmission path obtained from the digital data and the partner terminal. And an arithmetic circuit for performing a predetermined differential protection operation using the digital data of the other terminal transmitted to the terminal, wherein the bit length of the digital data transmitted to the other terminal and X represents the bit length of the digital data of the partner terminal transmitted to the end.
The bit length of the analog / digital conversion circuit is represented by Y (X
<Y), the digital data obtained from the analog / digital conversion circuit has a constant [1 /
(2 ^(YX) ) × K / minimum sensitivity of differential protection relay (K is a constant)]. 2. A sampling circuit for detecting a sampling data by converting each terminal current value of a power system into a predetermined electric level by an input conversion unit and sampling at a predetermined period, and converting the sampling data into digital data. An analog / digital conversion circuit, transmission means for transmitting the digital data to a partner terminal, setting means for inputting the minimum sensitivity of the differential protection relay, and automatic transmission via the transmission path obtained from the digital data and the partner terminal. And an arithmetic circuit for performing a predetermined differential protection operation using the digital data of the other terminal transmitted to the terminal, wherein the bit length of the digital data transmitted to the other terminal and X represents the bit length of the digital data of the partner terminal transmitted to the end.
The bit length of the analog / digital conversion circuit is represented by Y (X
<Y), the digital data obtained from the analog / digital conversion circuit has a constant [1 /
(2 ^(YX) ) × K (K is a constant)]. 3. The differential protection relay device according to claim 1, further comprising digital filter processing means at a stage subsequent to the analog / digital conversion circuit. 4. The differential protection relay device according to claim 1, further comprising means for setting the minimum sensitivity of the differential protection relay to a continuous value having a predetermined step width. 5. An input converter, a sampling circuit, and an analog / digital converter of a differential protection relay, and an input converter, a sampling circuit, and an analog / digital converter of a relay of another element.
2. The differential protection relay according to claim 1, wherein a digital conversion circuit is shared. 6. The differential protection according to claim 1, wherein when the differential protection relay is used as a main protection relay, an input conversion unit for back-up protection is shared by an input conversion unit of the main protection relay. Relay device.