JPH0546771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an offset mode type distance relay, and particularly to an offset mode type distance relay used for back-up protection in a main system.

[Technical background of the invention]

In recent years, in the field of power system protection, due to the increasing social importance of power transportation, it is common to have dual protection for the main power system by providing back-up protection in addition to the main protection. A distance relay system using a distance relay is often used as a backup protection device.

Note that distance relays determine failures by measuring the positive sequence impedance from the relay installation point to the failure point, and the time limits of the first to fourth stages are set depending on the measured distance. It is usually configured to make a decision. Here, we will mainly discuss offset mode type distance relays used for fourth stage protection.

As an example, the operating condition equation for an offset motor joint distance type electric appliance based on the phase difference calculation calculation method is shown in equation (1), and the relationship between the introduced amounts is shown in the vector diagram in Fig. 2.
The operating characteristics on the R-X chart are shown in FIG.

(Z _F + Z _B )｜I〓｜｜V〓｜cos(θ−)−Z _F・Z
_B ｜I〓｜ ² −｜V〓｜ ² >K ₀ …(1) However, I〓; Input current V〓; Input voltage Z _F ; Front offset impedance setting value Z _B ; Backward offset impedance setting value θ; Phase angle of input voltage V〓 with respect to input current I〓; Maximum sensitivity angle K ₀ ; Suppression term to prevent unstable response when input amount is small In equation (1), input current I〓 and input voltage V〓 are In the case of short-circuit relays, it is the line-to-line value, and in the case of ground-fault relays, it is the phase value. Then, the relationship of equation (1) is expressed on the maximum sensitivity angle (θ=), and equation (2) is obtained from the relational expression of V = I = Z.

(Z _F + Z _B )｜Z〓｜｜I〓｜−Z _F・Z _B ｜I〓｜ ² −｜
Z〓｜ ² ｜I〓｜ ² >K ₀ …(2) To make the relationship between the input current |I〓｜ and the distance to the failure point Z〓 easier to understand, by transforming equation (2), equation (3) becomes FIG. 4 shows this as a current-distance characteristic.

｜I〓｜ ² _＞ K ₀ / (Z _F − _{| Z} Minimum operating current within Z _B < Z < Z _F ) | I〓min
| is determined by the point where the right-hand side of equation (3) is minimized.

Therefore, let the denominator of the right side = Y (formula (4)) and convert this to
Differentiating with Z〓, we obtain equation (5).

Y=Z _F −｜Z〓｜) (｜Z〓｜−Z _B )=｜Z〓｜ ² + (Z _F +
Z _B )｜Z〓｜−Z _F Z _B …(4) Y′=−2｜Z〓｜+(Z _F +Z _B ) …(5) When formula (5)=0, that is, |Z〓 At the point |=Z _F +Z _B /2 (3
) The right side of the equation takes the minimum value, so by substituting |Z|=Z _F +Z _B /2 into equation (3) and defining the current value at that time as |I〓min|, we obtain equation (6). .

｜I〓min｜＞K ₀ {4/(Z _F −Z _S ) ² }…(6) [Problems with background technology] As is clear from the above equation (6), the minimum operating current Imin of the relay is (Z _F −Z _S ), that is, it depends on the setting value of the relay, and it shows that when the setting value changes, the relay operating sensitivity, which is one of the important performances of the relay, fluctuates.

In contrast to such conventional offset mode type distance relays, as mentioned earlier, power system protection is becoming more and more important as the social importance of power transportation increases. There is a need for an offset mode distance relay having highly reliable operating characteristics in which the operating sensitivity of the relay does not change depending on the setting value of the relay.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an offset mode type distance relay that has constant operating sensitivity characteristics regardless of the setting value of the relay.

[Summary of the invention]

In the present invention, as shown in the above-mentioned elucidation results, in the conventional device, the constant term is K ₀ as the minimum operating current.
Focusing on the fact that {4/(Z _F − _{Z B} ) ² }, we preliminarily calculate the suppression amount from the reciprocal of the constant term and the known constant I _N as follows: {(Z _F − Z _B ) ² I _N ² /4 }, the amount of motion (Z _F −Z _B ) |Z〓||I〓| ² −Z _F Z _B |I〓| ² −|Z〓| ² |I〓| ² and the amount of inhibition {( By calculating and comparing Z _F − _{Z B} ) ² I _N ² /4}, we try to eliminate the term {4/(Z _F − Z _B ) ² }, which causes the minimum operating current to fluctuate. It is something to do.

[Embodiments of the invention]

First, the reason why the constant term that causes fluctuation in the minimum operating current can be eliminated will be explained with reference to the functional block diagram shown in FIG.

That is, the offset mode type distance relay Ry has a voltage of
It consists of a current sampling section a, a set value input section b, an operation amount creation section c, a suppression amount creation section d, and a determination section e. Then, from the system voltage V and current value I from the voltage and current sampling section a and the respective set values Z _F and Z _B from the setting value input section b, the operation amount creation section c generates the operation amount (Z _F + Z _B ) IV. −Z _F Z _B ｜I〓｜ ² −｜V〓｜ ² is created,
On the other hand, the suppression amount {(Z _F −Z _B )IN /2} ² is created in the suppression amount creation section d from each setting value Z _F , Z _B from the setting value input section _b and the known constant I _N Then, the operation amount and the suppression amount are determined by the determination section e, and the result is output.

Therefore, the operating condition expression in the determination section e is as follows:
(7) is obtained.

(Z _F + Z _B )｜I〓｜｜V〓｜cos(θ−)−Z _F・Z _B ｜I〓
| ² − | V〓 | ² > {(Z _F − Z _B ) I _N /2} ² …(7) However, I _N is a known constant (current sensitivity). Similarly to above, equation (7) is converted to θ= Considering the angle of maximum sensitivity and using the relationship V〓=I〓Z〓, we obtain equation (8).

(Z _F +Z _B )｜Z〓｜｜I〓｜ ² −Z _F・Z _B ｜I〓｜ ² −｜Z〓｜
² ｜I〓｜ ² > {(Z _F −Z _B ) I _N /2} ² …(8) To make the relationship between current I〓 and distance Z〓 easier to understand,
By transforming equation (8), equation (9) is obtained.

｜I〓｜ ² ＞{(Z _F −Z _B )I _N /2} ² /(Z _F −｜Z｜)
(｜Z｜−Z _B )…(9) However, (Z _B <｜Z〓｜＜Z _F ) Here, the minimum value within the operating range of the offset mode distance relay (Z _B <｜Z〓｜＜Z _F ) Operating current｜Imin｜
is defined by the point |Z〓|=Z _F +Z _B /2, similar to the above equation (3), so by substituting this into equation (9), equation (10) is obtained.

|Imin| ² > (Z _F −Z _B ) ² I _N ²・1/4/Z _F −Z _B /2・Z _F
−Z _B /2=I _N ² (10) As is clear from the above equation (10), the minimum operating current value according to the present invention depends only on the known constant I _N , and each setting value of the relay It is not affected by Z _F and Z _B. FIG. 5 is a current distance characteristic diagram showing this situation. Further, even when the rear offset impedance is negative as shown in FIG. 6, the condition is satisfied. In this case, equation (11) can be obtained by replacing Z _B in equation (7) with −Z′ _B (negative setting value).

(Z _F −Z′ _B )｜I〓｜｜V〓｜cos(θ−)＋Z _F・Z′ _B
｜I〓｜ ² −｜V〓｜ ² > {(Z _F +Z′ _B )I _N /2} ² …(11) Here, as above, considering the maximum sensitivity angle, V〓＝I〓Z〓
Using the relationship, the minimum operating current |Imin| is (12)
The current-distance characteristic is shown in FIG.

｜Imin｜ ² > (Z _F + Z′ _B )・I′ _N ²・1/4/Z _F + Z′ _B /
2・Z _F +Z′ _B /2=I _N ² (12) As is clear from equation (12), even if the rear offset impedance is a negative integer value, its minimum operating current value changes. There isn't.

FIG. 8 is a block diagram of an embodiment of the offset mode type distance relay according to the present invention constructed using a digital processing device such as a microcomputer.

Each phase current I〓 _R , I〓 _S , I〓 _T of the power system is from current transformer 1,
Further, each phase voltage V〓 _R , V〓 _S , V〓 _T is introduced into a digital distance relay 4 from a transformer 2 via an input converter 3 . After the harmonic components are removed from each of the introduced electrical quantities by a filter circuit (FIL) 5, a sample hold circuit (S/H) 6, a multiplexer (MPX) 7 and an analog/digital converter circuit (A/D) 8 are used. is converted into a digital quantity and stored in a random access memory (RAM) 9. The operating output of the relay uses the amount of electricity stored in this random access memory (RAM) 9,
A digital arithmetic circuit (CPU) 10 performs calculations to be described later, and the determination results are outputted via an output interface circuit (I/F) 11.

FIG. 9 is a block diagram of the relay operation determination calculation performed by the digital calculation means. In this case, as an example, an R-phase element in a short-circuit offset mode type distance relay and a case where the rear offset impedance is positive will be shown.

In Fig. 9, 12a and 12b are the phase currents I〓 _R and I〓 _S from the grid, respectively, and 13a and 13b are the phase voltages respectively.
V〓 _R and V〓 _S , both of which are values that are periodically sampled by the digital distance relay and converted into digital quantities. 14 and 15 are relay setting values Z _F and Z _B , respectively. 16 is a calculation means for the line current I〓 _RS , 17 is a calculation means for the line voltage V〓 _RS , and 18, 19, and 20 are respectively (Z _F + Z _B ), based on the relay setting values Z _F and Z _B , (Z _F ·Z _B ) and Z _F −Z _B /2.

21 is the line current I from 16〓 _RS and the line voltage V from 17〓 sum of the setting values from _RS and 18 (Z _F + Z _B )
From (Z _F + Z _B ) I〓 _RS・V〓 Means for calculating _RS , 22
is the means for calculating the square of the amplitude value |V〓 _RS | from the line voltage V〓 _RS from 17, and 23 is the means for calculating the line current I〓 _RS from 16 and the calculation result from 19 Z _F・Z _B. From Z _F・
_{Means for calculating Z B | I〓 RS} ^{| _} The calculating means 25 calculates from the calculation results of 21, 22, and 23 {(Z _F + Z _B )I〓 _RS V〓 _RS −
Means for calculating Z _F・Z _B | I〓 _RS | ² − | V〓 _RS | ² }, 2
6 is a size determination means, and the calculation result of 24 and 25
Using the calculation result of (13), if the condition is satisfied, a judgment output, that is, a relay operation output is output.

{(Z _F +Z _B )I〓 _RS・V〓 _RS −Z _F・Z _B ｜I〓 _RS ｜ ² −｜V〓 _R
S ｜ ² }−{(Z _F −Z _B ) _IN /2} ² >0...(13) If we use the judgment formula of formula (13), we can determine the setting value as shown in formula (10) above. The operating current sensitivity of an offset mode distance relay can be defined by a known constant I _N.

FIG. 10 is a flowchart for explaining the arithmetic processing, and the arithmetic means of FIG. 9 will be explained using this flowchart.

That is, in step 1, the system electrical quantities I〓 _R , I〓 _S ,
The instantaneous values converted into digital quantities from V〓 _R , V〓 _S and the setting value of the relay selected from the human system Z _F ,
Read Z _B. In step 2, the index for distinguishing the time-series data of the amount of electricity introduced is increased by one from the value one sampling ago, and the index at the present time is again set to m. In step 3, each instantaneous value I〓 _R , I〓 _S ,
I〓 _Rn , I〓 _Sn , V〓 _R with V〓 _R , V〓 _S as data at time m
_n ,
V〓 Store in _Sn . In step 4, from the data in step 3, the line quantity I〓 _RSn = I〓 _Rn −I〓 _Sn , V〓 _RSn = V〓 _Rn
−V〓 _Sn
Calculate. In step 5, calculate (Z _F + Z _B )I〓 _RSn・V〓 _RSn from the data in step 4, and then proceed to step 6.
Now, calculate |V〓 _RSn | from the data in step 4,
In step 7, Z _F , Z _B ,
Calculate |V〓 _RSn | ² . In step 8, the operation amount is determined from the results of step 5, step 6, and step 7, {(Z _F +Z _B )I〓 _RSn・V〓 _RSn −Z _F・Z _B |I〓 _RSn |
² −
|V〓 _RSn | ² } is calculated, and in step 9, the suppression amount,
Calculate {(Z _F −Z _B ) _IN /2} ² . In step 10, the calculation result A of step 8 and the calculation result B of step 9
If the judgment result is positive, proceed to step 11 and output the relay operation output.
Furthermore, if the determination result is not positive, the relay is inoperative.

In the above embodiment, the offset mode type short-circuit distance relay for the R phase has been described, but the structure can be similarly configured for the S phase and the T phase. Also, regarding the ground fault relay, the part where the line-to-line quantity of the short-circuit relay is introduced may be replaced with a phase quantity. The present invention is not limited to digital relays, and any type of relay may be used as long as it forms the operating condition equation of the present invention. Furthermore, the rear offset impedance is not limited to the positive case, and if it is negative, it goes without saying that the calculation may be performed by replacing the impedance Z _B with -Z' _B.

〔Effect of the invention〕

As explained above, according to the present invention, by setting the suppression term in the operating condition equation of the offset mode type distance relay to {(Z _F − Z _B ) I _N /2} ² , the minimum operating current value is influenced. Since the configuration is configured to eliminate the variation due to the set value, it is possible to provide an offset mode type distance relay that always has a constant operating current sensitivity regardless of the set value of the relay.

[Brief explanation of the drawing]

Figure 1 is a functional block diagram explaining the basic concept of the offset mode type distance relay according to the present invention, Figure 2 is a vector diagram showing the relationship between the amount of electricity introduced in the offset mode type distance relay, and Figure 3 is the R-X
Fig. 4 is a diagram showing the operating characteristics of an offset mode type distance relay as shown in a diagram.
A distance characteristic diagram, FIG. 5, is a current-distance characteristic diagram, FIG. 6, of the offset mode type distance relay according to the present invention.
The figure is an operating characteristic diagram of an offset mode type distance relay expressed on an R-X diagram when the rear offset impedance is negative, Figure 7 is a current-distance characteristic diagram for the case of Figure 6, and Figure 8 is a diagram of the present invention. A schematic diagram showing the overall configuration when a digital distance relay is applied as an embodiment of the offset mode type distance relay according to the present invention, and Fig. 9 is a block diagram showing an example of operation determination of the offset mode type distance relay according to the present invention.
FIG. 10 is a flowchart explaining the calculation process. a...Voltage, current sampling section, b...Setting value input section, c...Operation amount creation section, d...Suppression amount creation section, e...Judgment section, 1...Current transformer, 2...Transformation 3...Input transformer, 4...Digital distance relay, 5...Filter circuit, 6...Sample and hold circuit, 7...Multiplexer, 8...
A/D conversion circuit, 9...Random access memory, 10...Digital arithmetic circuit, 11...Output interface circuit, 16...Line current I〓 _RS
Calculating means for 17...Line voltage V〓 _RS calculating means,
18... Calculation means for (Z _F + Z _B ), 19... Z _F・Z _B
Calculating means for 20... (Z _F - Z _B ), 2
1... (Z _F + Z _B ) I〓 _RS・V〓 Calculating means of _RS , 22...
｜V〓 _RS ｜ ² calculation means, 23...Z _F・Z _B ｜I〓 _RS ｜ ² calculation means, 24...{(Z _F − Z _B ) I _N /2} ² calculation means, 25 ...(Z _F +Z _B ) I〓 _RS・V〓 _RS −Z _F・Z _B ｜I〓 _RS
｜
² −|V〓 _RS | ² calculation means, 26...size determination means.

Claims (1)

[Claims] 1. Operation _amount {(Z _F + _{Z B} ) In an offset motor type distance relay that derives IV-Z _F・Z _B |I| ² − |V ^|
The above suppression amount is expressed as relay setting values Z _F , Z _B and known constants.
An offset mode type distance relay characterized in that I _N to {(Z _F − Z _B ) I _N /2} ² . 2. The offset mode type distance relay according to claim 1, characterized in that the setting value Z _B of the relay is replaced by -Z' _B (negative setting value).