JPS6399720A - Digital protective relay - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a digital protection relay for detecting faults in the power system, and is an undervoltage relay with current compensation. It is related to vessels.

[Conventional technology]

Figure 10 shows, for example, ConferenceP published by IEE.
ubl 1cation N11249 Apri I
This is a circuit configuration diagram of a conventional undervoltage relay with current compensation (hereinafter referred to as UVZ) shown on pages 50 to 54 of 1985. In the figure, (1) is a voltage transformer, (2)
) is the current transformer, (311(4) is the voltage and current transformer
input converter, f5) is a phase shifter, (6)
is a setting device that sets the amount of current compensation, (7), (81 is a half-wave rectifier that allows only the half-wave period of AC to pass, (9) is a setter that provides a detection level, and Q (I is used to compare and judge the size. The comparator, αυ, is a timed circuit, and the UVZ indicated by □□□
h゛, 1.

Next, the operation will be explained with reference to FIG. The voltage and current obtained from the power grid are connected to their respective input converters (
3) Insulated and introduced by crying (4).

The current I is phase-shifted by an angle φ in the shifter (5), but
This angle is selected to correspond to the phase difference between voltage and current at the time of a power transmission line fault, and is approximately 75°. This move +1j
The current 11φ is set by a setting device (
6), the current compensation amount of Zl can be obtained. Voltage V
and the current compensation amount ZI, respectively, in the medium wave rectifier (7).
When the rectified value kO is added to the comparator Qt3 through (8), as shown in FIG. 11, with the origin on the ZI axis,
An oval locus surrounded by a size ko is obtained, and if the voltage V is within the range of this oval, the comparator 00 outputs an output. This output is checked at a predetermined time 11fi by the time limit circuit aυ, and the determination result is output to the OUT terminal.

[Problem that the invention seeks to solve]

Conventional Uv'Z is based on the above method, so it can only perform one judgment process every half cycle of AC.
Regarding the time it takes to detect an accident after it occurs, the maximum missed time is half a cycle and the judgment time is half a cycle, so one cycle is required, and there is a problem that the accident detection time is slow.
c. Also, since the circuits Ji+ and J are analog circuits, the effects of drift and aging of components can be considered.
Therefore, there were problems such as it took time to adjust and the detection sensitivity could not be made high. Furthermore, since it is not possible to receive digital signals from digital transformers and digital current transformers, which have recently been developed, a problem has arisen in that the range of use is limited.

This invention was made in order to solve the above-mentioned problems, and since it uses a microprocessor to perform direct arithmetic processing on the mathematical formula, it can be judged based on speech speed, and there is no need to take into account drift or aging. The purpose is to obtain UVZ.

[Means for solving problems]

The UVZ according to the present invention realizes an undervoltage coupling WL device that converts voltage and current into digital values and adds current compensation through arithmetic processing, and reduces the number of sampling data used for arithmetic processing. It not only enables high-speed detection, but also achieves high reliability by reducing the effects of drift and aging, which are problems with analog circuits.

[Effect]

In order to realize the characteristics of UVZ in this invention, a current compensation coefficient is provided, and the magnitude of the difference calculated by calculating the difference with the voltage is compared with the magnitude of the current compensation amount multiplied by a constant. A first determining element that determines the magnitude of the voltage itself, and a second determining element that determines whether the magnitude of the voltage itself is large or small by comparing it with a predetermined value.
It is equipped with two judgment elements, and is digitally processed so that an accident is detected when either the first or second judgment element is judged, so it has the effect of being able to judge at high speed.Furthermore, the digital calculation process prevents drift and Long W1 with little change over time
It is possible to maintain stable characteristics.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (2) and a4 are filters, which, as is well known, remove frequencies above 72 of the sampling frequency among harmonics contained in voltage and current. The α power is a multiplexer that holds the value until the next sampling period, and the output of the sample hold αG and (lLQ) is sequentially switched and transmitted to the analog-to-digital converter (g). The OI is a microprocessor and the memory ( A) A program stored in advance is used to perform calculations, and the results are output to the output circuits Gυ and Iwa.

Figure 2 is a waveform diagram showing a sample hold operation in which voltage ■ and current I are sampled at the same time as sample signals and held until the next sample signal arrives. , it will be converted into a digital value and processed.

FIG. 8 is a vector diagram for explaining means for realizing the characteristics of an embodiment of the present invention, which is actually realized by digital calculation. The same applies when a vector diagram appears in the following explanation.

When the phase of the current I is shifted by φ and the magnitude is doubled, pect/I/(zl) is derived, and the difference from the voltage V is calculated, resulting in a vector (V-Zl). Vector (v-
Assuming that the size of zi ) is proportional to the size of the vector (zl), find kXIZII with k as a constant, IV-Zll≦kxlZIl ・・・・・・・・・・・・
・・・・・・・・・ When calculating ■, a circle with a radius of 1 (IZII) centered on the tip of vector ZI becomes the range where voltage ■ exists.The characteristics inside this circle are determined by the first judgment. It is expressed as an element and a characteristic.

On the other hand, the magnitude of the voltage V is determined, and this is the constant value k.

If we find a range smaller than , we will get the formula 0, which will be a circle centered at the origin.

IVI≦l(o ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・ ■This is expressed as a characteristic (c) as a second determination element.

Therefore, by calculating the logical sum of the first and second determination elements, the characteristic shown by the solid line in FIG. 8 is obtained, and by outputting the determination output from the output circuit Q in FIG. UVZ
It turns out that Q3 detected it.

FIG. 4 is a flowchart illustrating an example of an arithmetic processing method for realizing UVZ of the present invention.

In the following explanation, the sampling frequency is set to 12 different voltage and current frequencies, that is, 80 degrees electrical angle with respect to the voltage and current frequencies, and the symbol is T. Assuming (1), the previous data is 80°, 60°, 90°, etc.
t-T), (t-2T), (t-aT), . . . Therefore, if the phase difference is θ, the voltage and current are as follows: v (t-nT)=-Vain(ht〇)-80°×
n)=Vsir+l(art+θ)-nT)...
・・・・・・・・・・・・91. ■i(t n
T)=Isin(ωt −nT) ・・・・・・・・・
・・・・・・・・・・・・・・・・・・ ■However, n ” 1 + 2 + 8 +...・The following explanation is an example, (tl, (t-T)
.

The data of (t-aT) and (t-4'l') are used.

First, the first determination element 4 will be explained.

Using the data of i (t) (to) and 1 (t-T)@, if we shift the phase angle of the electric current by the phase angle φ = 75°, we get i (tl75°) = I (ωt + 75°)" 1 0
,25885ina+t+0.9659cxs
ωt ) ・−= ■On the other hand, i(t T)=Isin
(ωt 80°)Ω41 sin ,,,(--I
cos art==咀i (l l-!-1casωt
・・・・・・・・・・・・・・・・・・・・・・・・
Substitute ■■ into ■ nbai (tl75°) = 0.25881 (tl + 0.9
659 (v'J 1ftl-2i (t-T)
) = 1.9ats (i(tl-r (t-T)
)・・・・・・・・・・・・・・・・・・ ■What? : Can be realized by +, subtraction □□□, and multiplication -. Multiplying this by the current compensation iZ (to) gives Zi (tl75°)
By subtracting (to) m v(t)H and zi(t+'y5°), we get the difference D(tl=vft) Zi(tl75°)=v(t
) −1,98192(1(t) −i (t −T )
) −・・−・−・'−・ This means that the operation in ■ has been executed. Similarly, 1(t-a'r)i, 1(
t-4T)%, v(t-a'r)ra 8T=90
°Previous data, i(tl75°-3T) = Istn(ωt+75°-5
T) = x, 9ats(i(t-s'l')-i(t-
4'l'))...■ is the current compensation amount zc(η, and D(t-aT)=v(t-gT)-1,9ax9
Z (i (t-8'l')-i (t-4T)
)-in is required for castle calculation.

In the case of a sine wave, BT = 2 of the data with a 90° phase difference.
It is well known that the square root of the sum of products represents the magnitude of a sine wave. Therefore, for subtraction) squared (to) and subtraction - squared 1
Finding the square root 14'3 of the sum of 411 14'lJ, we get (
To D t) + D2 (t-aT) ) '/22 V'1 = ((xt+ Zl (tl75°)) + (v(t-a
'r)-Zi (1+75°3T))):(v”ltl
-2Xl, 9319Z Mt) (1(t)-i (t
-'11))+1.9a192Z" (iit)-i
(t-T))" + v'tt-aT)-2x1.9a
i9Z v(t-5T)(i(t-sT)-i (t-
4T))+1.98192Z"[i (t-a'r)
-i(t-4'I') )" ) '"(V"-2V
ZlQ1111(75°-9)+(Zl)")'t-・
・−・・−・−−−−−−@) and υ, 0 formula corresponds to the left side of 0 formula. On the other hand, the magnitude of the current compensation amount is Z(31
) squared (b) and the sum of the squared decoy of the zcl force! Square root of 4Q! 471, and multiplying this by the constant k t4!1 is k (Z2i'(tl75°) + Z2i(tl75°-
3T))'= 1(Zl (sir+2(ωt4-75
°)+9iJ12(ωt+75°-5T)l! 'z:k
ZI・・・・・・・・・
・・・・・・ ○, and formula 0 corresponds to the right side of formula 0.

Therefore, by applying the formula ■ and the @ formula to the formula 0, we get (V2-2VZICDS(75°-θ) + (Zl)2)
”!≦k (ZI ),,,,,, ■The result of the comparison operation (stripes) appears. Expanding the 0 formula to find the voltage V, y2-2VZLcoa (75°-θ) + (ZI )2≦2(ZL)”−, v≦(cas(75°−θ juice(Q (
75o-y)-(1-to2))(Z1)-@
Therefore, the relational expression between the current compensation amount ZI and the voltage V can be expressed as a function of the phase difference (75°-θ).

The shift of the current compensation amount + eye angle was set to 75°, but if it becomes - film and set as -, ■≦(■(φ-θ) cc+s2(φ-#)-(11
2) ) (Zl) 11. ■It can be expressed as a combination.

In Figure 5, with k set to 08 and k = 1.2,
The phase difference between the vector of current compensation amount (ZI) and the voltage V (
The coefficient (a) of the magnitude of V with respect to (ZI) when changing 75° - θ) from 0° to 180° (a) 8 (75°
−θ)±(75°−〇)−(1−■l).

In addition, (treetop and (b) in Fig. 6 are illustrations of Fig. 5, and respectively =0.8.φ=75° and :l:1.
2. This shows the range of ■ in equation 0 when φ=75°, and the radius o centered at the tip of the vector (Zl),
An internal timeness of Bx (Zl) and radius 1.2X (ZI) is obtained. Therefore, if the voltage V is inside this circle,
The determination condition for the calculation is satisfied, and the first determination element @ is obtained.

The second determination element will be explained with reference to the arrow. The voltage V is v
Itl! 31+ squared ω and v(t-3T)z squared F
Finding the Wako square plate of il+, (vftl+v (t-8'l'))3/2=(v2
sLr12 (ω is 10) + v2sir + 2 ((+1 t
+θ−3T) Port=V ・・・・・・・・・・・・
Become an older brother.

To determine when the voltage V has decreased to a predetermined value below θ, a comparison operation βG is performed between the square root δ and a constant koH, and (vftl + v”(t-8T) = V≦ko
If -="-"-9, this becomes a circle passing through the origin and having a radius kO, and if the voltage ■ is within this circle, the judgment condition for the calculation is satisfied, and the second judgment element (c) is obtained.

Therefore.

If the logical sum group of the first and second determination elements is obtained, the characteristic shown by the solid line in FIG. 8 can be obtained at the OUT terminal.

FIG. 7 is an explanatory diagram for calculating the UVZ detection time according to the present invention. (a) is voltage V, (b) is current l
, the phase is 75° behind V, and (C) is the current compensation amount, φ = 7
5°, (2) applies current compensation to the voltage ■, and (
v-z+), (e) is the amplitude value calculation result of formula 0, (f) is the sampling time, and the time (t-5T)
It is assumed that the accident occurred at point F, 1a after the point.

The amount of current compensation (c) after the accident occurs is determined by the currents 1 (t-4T) and 1 (t-a'r) after the accident occurs, so
The value becomes accurate from time (t'-IT) onwards. Therefore, the amplitude value calculation in (e) becomes the correct value after the accident after the time when 1(t-4T) becomes the established value.
The maximum detection time for which Equation 0 holds true is after the accident ((t-
4'r)-(t-sT)l+(t-(t-4T))+(
(t+T)-tl=6T or 30°X 6 = 1
The time is equivalent to 80°, which is 1/2 cycle of the power system. Specifically, in a 50Hz power system -(
15o) ×(//2)sw=:IQmsec Terror.

In addition, in the above embodiment, a method of using data around 1,3T=90° was shown as a method for determining the magnitude of the sine wave, but data at every 30' or 60°4A is
ltl+ v2(t-T)-s7chovat) v(t
-'r) )l/'2=v(SIr+2(- of ωt+)
1-5in2(a+i+θ-T) -, fj 5in(
ωt+θ)sui ((II to 1θ−T)port(vft
l-v(t-T)+:(t-2'l")l'
2=V(sir+2(ωt+t/)−5in”
(act +0-T)4-sin2(act + t
j-2T) l'2=±V ・
・・・・・・・・・・・・ Even if it is used like Ov”2, the calculation can be performed in the same way.

In the case of this formula 0, since data at time t and (t-T) is used, 1! In the calculation of the amount of compensation, assuming that 1(t-T) and Bt-2T) = - evening are used at the time of (t-T),
The detection time is ((t-2T)-(t-aT))+(t-(t-2T)
) + i (t + i') - 1) = 4T, that is, if the power system is 50Hz, (1150) x (800
4/3600) m = 6.67m5ec high-speed detection becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, in order to realize the UVZ characteristics using a digital arithmetic processing method, a current compensation coefficient is provided, and the magnitude of the difference amount obtained by calculating the difference with the voltage and the current compensation amount are determined. A first determination element that determines the magnitude by comparing the magnitude of the voltage multiplied by a constant, and a second determination element that determines the magnitude of the voltage itself by comparing it with a predetermined value. Since it is configured to have a good structure, accidents can be detected at high speed, and stable characteristics can be maintained over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram showing UVZ according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of sample and hold operation, Fig. 8 is an explanatory diagram showing the characteristics of this invention, and Fig. 4 is an arithmetic processing method. FIG. 5 is a diagram of the relationship between the voltage of the first determination element and the amount of current compensation, FIG. 6 is a characteristic diagram of the first determination element, and FIG. 7 is an explanatory diagram for calculating the detection time. , Figure 8 is a circuit diagram of the conventional UVZ, Figure 9 is the conventional UV
It is a figure showing the characteristic of Z. (1) is a voltage transformer, (2) is a current transformer, +3),
+4) is the input converter, (5) is the phase shifter, (6) is the setting device, (71, (81) is the half-wave rectifier, (9) is the setter, α
O is a comparator, αυ is a time limit circuit, (b) is UVZ%@, α
◆ is a filter, (A), aQ is a sample hold, Q power is a multiplexer, (to) is an analog-to-digital converter,
QI is a microprocessor, (1) is a memory, QI>
, ＠ is the output circuit, slope, (c) is the characteristic of UVZ),
@, C3111μs, 01. □□□ is input data, (to). (To), 13G/Country is the difference calculation means, 4, 01. side, G
η, 0 is a multiplication operation means, nu, o4
．． ! 4n, ω, I0 is the square calculation means, (42, 14
fP, the leap is the addition calculation means, @Crow, t471, the cormorant is the square root calculation means, the decoy, the open is the comparison calculation means, the figure is the setting value,
Flash is a disjunctive means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A digital protective relay that detects faults in the power system by sampling the voltage and current of the power system at a certain end, digitally converting the voltage and current, and then performing arithmetic processing based on the values, the current being phase-shifted. means for shifting the phase of the phase shifter by a predetermined amount by a calculation; means for converting the phase shift calculation result into a predetermined size by a magnification calculation; and means for calculating the size of the magnification calculation result by a first amplitude value calculation. and means for obtaining a difference between the voltage and the magnification calculation result by performing a difference calculation; means for calculating the magnitude of the difference calculation result by a second amplitude value calculation; and a predetermined value for the first amplitude value calculation result. a first determination element that determines the magnitude by a comparison operation between the calculation result multiplied by a multiplication factor and the second amplitude value calculation result; and a predetermined value by calculating the magnitude of the voltage by an eighth amplitude value calculation. A digital protective relay, comprising: a second determination element that determines the magnitude by a comparison operation with the first determination element and the second determination element, and an accident is determined by a logical sum of the first determination element and the second determination element.