JPH0421313A - Disconnection-open-phase detector - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a wire breakage/open phase detection device for detecting a wire breakage/open phase fault that occurs in a power distribution system.

[Conventional technology]

Figure 8 is a block diagram showing part of the distribution system that supplies three-phase power to loads. In the figure, E is the power source, 1 is the main transformer of the substation supplied from the power source E, and 2 is the main transformer. 3 is a distribution line to which the bus 2 is also supplied with power, and Zr is a load connected to the distribution line 3.

FIG. 9 is a block diagram showing a conventional wire breakage/open phase detection device for detecting a wire breakage fault when it occurs at point F0 in FIG. 8. In the figure, PTa, PTb, P
Tc is a potential transformer (PT), Ta, Tb, and Tc as voltage detection means for detecting the voltage of A phase, B phase, and C phase, respectively.
4 is an input quadrature transformer for insulation to which the secondary outputs of the instrument transformers PTa, PTb, and PTc are applied, and 4 is an input quadrature T.
a.

A negative phase detection filter circuit to which the secondary side outputs of Tb and Tc are added; 5 is a rectification and smoothing circuit that rectifies and smoothes the eight negative phase detection filter circuits 4; 6 is a rectification and smoothing circuit when the rectification and smoothing output exceeds a predetermined level. This is an 8 level detection circuit that outputs a detection signal SC of a disconnection accident.

FIG. 10 is a circuit diagram showing a symmetrical equivalent circuit in the case where A-phase disconnection occurs at 11 points in FIG. 8. In the figure, Ea is the A-phase voltage of power supply E,
-0 is the positive phase, negative phase, and zero sequence impedance of the power supply, respectively; zt+, Ztz are the positive phase, negative phase impedance of the main transformer of the substation, respectively; Zs+, Z4□ are the positive phase, negative phase impedance of the distribution line, respectively. , Z rl + Zra are the positive-sequence and negative-sequence impedances of the load, respectively, Rg is the grounding resistance, (:, 0', Co is the zero-to-ground capacity of the own line, and the zero-to-earth capacity of all lines other than the own line, respectively. .V1
' is the positive sequence voltage on the power supply side at the disconnection point, ■1 is the positive sequence voltage on the load side at the disconnection point, Vx'' is the negative sequence voltage on the power supply side at the disconnection point, ■2 is the negative sequence voltage on the load side at the disconnection point , ■ is the current flowing through the circuit.

Next, the operation will be explained.

The basic principle of the device shown in Fig. 9 is to utilize the fact that a negative sequence voltage v2 is generated on the load side at the disconnection point, and output a detection signal SC when this negative sequence voltage v2 exceeds a predetermined level. It is said that Next, the reason why the negative phase voltage v2 occurs will be explained.

Assuming that there is a break in the A phase at 11 points in FIG. 8, the symmetrical equivalent circuit at this time is as shown in FIG. 10. In FIG. 10, the zero-phase circuit becomes an oven at point a, so there is no need to consider it.

Therefore, the current from the power source Ea flows through the positive phase circuit and the negative phase circuit as shown. Also Z s+, ZltZt
++ Zt** Zl+* Zlz) Each impedance is small, and the load impedance of Z rl+ Zra is relatively large. As a result, the positive sequence voltages v,',v, and the negative sequence voltages v2' on the power supply side and the load side at the disconnection point F1.

V2 can be expressed by the following formula.

V+'=Ea-Zg+l4Ea V+ = (Zt++Z4++Zr+) I) ZrlI
V,'=Z,□IJqO V2 = (Ztz+Zlz+Ztx)I ”i
ZrdHere, if the load Z, is a general static load, Zr = 12, so this is 2. Then, it ends up being E a ”F 2 Z r I. In other words, the voltage drop corresponding to the power source Ea is almost Z rl, Z
It can be seen that this occurs at r2, and there is a relationship of 1→V 2 &, -E a.

From the above, Negative sequence voltage v,'= on the power supply side at the disconnection point F1.

It can be seen that the negative phase voltage V*=-Ea on the load side at the disconnection point F1.

In the device of FIG. 9, the potential transformer PTa.

Input the voltage detected by PTb and PTc into quadrature transformers Ta and T.
b and Tc to the negative phase detection filter circuit 4, the negative phase voltage 2 is detected, and the voltage obtained by rectifying and smoothing this negative phase voltage by the rectifying and smoothing circuit 5 is outputted by the level detection circuit 6. When it is detected that a predetermined level (eg -Ea) has been exceeded, a detection signal SC is output.

[Problem to be solved by the invention]

Since the conventional disconnection/open phase pressure detection device is configured as described above, it can detect unbalance of load zr and voltage transformer PTa
, PTb, PTc errors, etc. A negative phase voltage corresponding to the error is constantly generated, and it is difficult to distinguish between the negative sequence voltage corresponding to this error and the negative sequence voltage generated at the time of disconnection, and it is difficult to detect the open phase voltage. In addition, there were other problems such as the inability to distinguish between phases that were missing.

This invention was made in order to solve the above-mentioned problems, and it is possible to reliably detect disconnection and open-phase accidents in the power distribution system without being affected by the negative phase voltage of the error mentioned above. It is an object of the present invention to obtain a disconnection/open phase detection device that can also identify open phases.

[Means for Solving the Problems] The disconnection/open phase voltage detection device according to the present invention utilizes the fact that, for example, a torque relationship occurs, and for this purpose, detects each phase voltage, The vector relationship between them is examined using an arithmetic device.

[Effect]

When it is determined that the above-mentioned vector relationship is established, the arithmetic device according to the present invention generates a detection signal indicating the accident phase.

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

For example, when a disconnection accident of phase A occurs at point F1 or point F2 in FIG. The two-phase phase voltage Vb.

The vector relationship with Vc is V b + V c V a = ... (1
). For this reason, in the present invention, the phase voltages Va, Vb, and Vc are constantly detected and a calculation is made to determine whether the relationship in equation (1) above is satisfied. In addition, if a disconnection accident occurs in phase B or phase C, the following vector relationship will occur.

Next, the reason why the above formula (1) holds true will be explained.

"In case of disconnection at point F1" In the equivalent circuit of FIG. 10. Figure 2 shows the phase voltages Va', Vb'Vc', Va on the power supply side and the load side in equations (4) and (5) above.
, Vb, and Vc, and Va on the load side,
It can be seen that the vectors Vb and Vc have the relationship shown in equation (1) above.

``Case of disconnection at point F2'' The symmetrical equivalent circuit in this case is shown in FIG. Note that Z atZ atZ in this Figure 3 is equivalent to 6 (Z, l+Z t+), (Z
−2+ Z tz). Also, 2411212゜Z
s. are the positive-phase, negative-phase, and zero-sequence impedances of the distribution line on the load side at the disconnection point, respectively, and Z(1', Zs2Z4゜'
represent the positive-phase, negative-phase, and zero-sequence impedances of the distribution line on the power supply side at the disconnection point, respectively.

In FIG. 3, Z*t+ + lt2. Z4+
+ Z4xZso' 241. Zs2. Zta
Each impedance of is small, and Zrl+Zrx is relatively large. Also, R, , Co′, Co of the zero-phase circuit
The impedance of is extremely large compared to others. Therefore,
Most of the current (2) from the power source Ea flows through the positive phase circuit and the negative phase circuit as shown by the solid line in the figure, and the current flowing through the zero phase circuit shown by the dotted line is extremely small. The result is as follows.

L' = Ea (Lt+ + Z4m') I&
, EaL = (Zl r + Zr+)I ”
r Zr + IVx': (Lta + 14 m
') I Saki OVP =-(Z4x + La
B5-ZrzI also -V, -V. '=V*V-'
Therefore, Vo 40'Misaki■, (','V2'''
rO) Here, co is the ground capacity of the own line, and Co' is the ground capacity of all lines other than the own line, so further R, (usually 30Ω)) ωCo'Zso' Saki01 z5゜SakiO It's fine.

Therefore, since v, > va', V, = v* = -ZT, I think it's a mistake.

Here, since - for boat fishing, Z rl = Z ra, so if we put this and Zr, we get the result.

Ea=22. It becomes I. That is, the voltage drop that opposes the power supply voltage Ea occurs mostly at Zr1Zrz, and, moreover, vl Saki-Ea Saki--Ea O Opponent--Ea Therefore, Va=V.

+V.

+v2 =--Ea Vb”V.

+a"V+ + a V z =--Ea (1-a"+a) ■ Ea (1+a" +a-2a2) =--Ea (-2a2 =a" Ea V c = V a +aV+ + a 2 =-- Ea (1-a+a") =--Ea (1+a+a2-2a) and -Ea (-2a) = aEa. Figure 4 shows each phase voltage Va in equation (7) above,
It shows the vector relationship between Vb and Vc, and it can be seen that the relationship is expressed by the above equation (1).

FIG. 1 is a configuration diagram showing a disconnection/open phase pressure detection device according to the present invention based on the above-described principle, and parts corresponding to those in FIG. 9 are given the same reference numerals and explanations are omitted.

In Fig. 1, 7a, 7b, 7c are potential transformers PT.
Each phase voltage Va, Vb, detected at a, PTb, PTc,
Input Vc to quadrature transformers Ta and Tb.

8 is a multiplexer that sequentially takes out the outputs of the sample and hold circuits 7a7b and 7c; 9 is a multiplexer 8;
an A/D converter that converts the output of the
0 is based on the above digital data (1) and (2).
), a CPU as an arithmetic unit that performs calculations to check the relationship between equations (3), 11 is a ROM that stores the CPU to O calculation program, 12 is a working RAM for the CPU10, and 13
14 is a digital output circuit that outputs the detection signal SC when the relationships in equations (1), (2), and (3) above are established;
This is a pass line that connects PLIIO and each part.

Next, the operation will be explained.

The phase voltages VaVb and Vc sampled at predetermined intervals by the sample and hold circuits 7a, 7b, and 7c are sequentially extracted by the multiplexer 8 and sent to the A/D converter 9.
After being converted into digital data, it is sent to CPU10. CP[Jlo executes arithmetic processing to detect whether the above equations (1), (2), and (3) hold using data indicating each phase voltage Va, Vb, and Vc, and calculates the above (1). .

When either equation (2) or (3) is established, a detection signal SC is outputted through the digital input circuit 13.

FIG. 5 shows a flowchart of arithmetic processing by the CPU 10. This calculation process is based on the power distribution system fundamental wave (50 or 60Hz
) is executed periodically, for example, every 30 degrees of electrical angle.

In FIG. 5, first, in step STA, processing is performed to detect a one-line accident and determine its accident phase, and if it is determined that there is an accident on the - line, the next step STB is to perform the above (1)
), (2), and (3), and outputs a detection signal SC according to the determined content. In addition, if it is determined in step STA that there is no accident, in the next step STB,
- It is determined that there is no wire breakage, and therefore the detection signal SC is not output.

Then, in step STC, the process waits for the end of the cycle corresponding to the electrical angle 30@, and returns to step STA in the next cycle.

FIG. 6 is a flowchart showing detailed processing of step STA.

In FIG. 6, in steps STI and ST2°Sr1, it is sequentially checked whether or not each phase voltage Va, Vb, Vc has decreased below a predetermined level Vs.
If all c exceeds Vs, it is determined in step ST4 that there is no accident, and the connection is made to step STB in FIG. 5 ([phase] in FIG. 6).

Further, when Va<vs in step STI, the process proceeds to step ST5, where the relationship vb<vsO is checked.

And if Vb<Vs, then Va.

Since both vb have decreased, it is determined in step ST6 that the accident is not only in one line, and the connection is made to step STB in FIG. 5 ([phase] in FIG. 6). vb in step ST5 above.
is sufficiently large, the process advances to step ST7 and Vc<V
Examine the relationship between s. If Vc<Vs, both Va and Vc have decreased, so it is determined in step ST6 that the accident is not a one-line accident, and step STB in Fig. 5 ([[
phase]). When Vc is sufficiently large in step ST7, only Va has decreased, so in step ST8 it is determined that there is a fault in the A phase-line, and the connection is made to step 5TB in FIG. 5 (0 in FIG. 6).

If Vb<Vs in step ST2, the process proceeds to step ST9, where the relationship VC<VS is checked. V
If c<Vs, both Vb and Vc have decreased, so it is determined in step 5TIO that the accident is not only on one line, and the connection is made to step 5TB in FIG. 5 (0 in FIG. 6). If Vc is sufficiently large in step ST9 above, step 5T
II determines that it is a B phase-line fault, and steps 5T in Figure 5 are performed.
Connect to B (0 in Figure 6).

Further, when Vc<Vs in step ST3 above, Vc
Since the voltage has dropped, the process proceeds to step 5T12, where it is determined that the fault is in the C phase-line, and then the connection is made to the secondary step STB (■ in FIG. 6).

FIG. 7 shows the process of step STB in FIG. 5 in detail. In the figure, [phase], ■, ■, 0 are in FIG.
,0.0 are connected.

In order to check whether the vector relationships shown in the above equations (1), (2), and (3) hold through the arithmetic processing of the CPU 10, each vector Va, Vb is used.

When the phase relationship and magnitude relationship of Vc are determined individually, and each of the above two relationships satisfies a predetermined condition, one of the above equations (1), (2), and (3) is established. It shall be assumed that FIG. 7 shows a process for determining the above-mentioned phase relationship and size relationship.

If the determination in step ST8 in FIG.
The process advances to step 5T13 in the figure. First, phase voltage Va
, Vb, and Vc to line voltage Vab.

Vca is determined, and then in step 5T14, the phase difference between this line voltage Vab and Vca is determined as P=l arg(Vab)-
Find arg (Vca)I (arg: phase angle). In step 5T15, it is checked whether this phase difference P is smaller than a predetermined magnitude ε1 (for example, ε1=101). P is ε.

If it exceeds , it is determined in step 5T16 that the disconnection is not just one line, and the process ends.

If P<ε1, proceed to step 5T17, where V
Expresses the relationship between the magnitudes of a, Vb, and Vc. Q is a predetermined magnitude ε2 (for example, for rated phase voltage 63.5V, εg=
10V), and if Q exceeds ε2, it is determined in step 16 that there is no disconnection in just one line, and the process ends. If Q ε2, step 5T
20, it is determined that there is a disconnection/open phase of the A phase-line,
The detection signal SCa is output.

In FIG. 6, step 5TII or step 5T1
If there is a determination of 2, the process proceeds to step ST21 or step 5T22 in FIG. In these steps 5T21 and 5T22, steps 5T13 to 5T22 described above are performed.
Processing similar to that of 5T20 is performed. However, in that case, the line voltages Vab, Vca, phase voltages Va, Vb, Vc, etc. used in steps 5T13 to 5T20 are replaced as shown in the diagram. After the process of step ST21, step 5723 or 5T24
Then, it is determined that there is a disconnection/open phase in the B phase - line, and the detection signal SCb is output, or it is determined that the disconnection is not only in the - line, and the process ends. Also, step 5T22
After processing, proceed to step 5T25 or 5T26, and
It is determined that there is a disconnection or open phase in the phase line, and the detection signal S
Press Cc or determine that the - wire is not the only disconnection, and end the process.

As described above, the magnitudes of P and Q determined by the formulas shown in steps 5T14 and 5T17 are set to the predetermined value ε2. Vector Va if smaller than ε2.

The phase relationship and magnitude relationship of Vb and Vc must be as shown in Figure 2 or Figure 4 (example for A phase), that is, the above formula (1) must be satisfied. I'm trying to judge. The calculation formula for calculating P to check the phase relationship and Q to check the size relationship is shown in step 5.
T14 5In addition to the formulas shown in T17, any one of the formulas listed on the horizontal axis of the table below can be used to calculate P, and the formula to calculate Q can be listed on the vertical axis of the table below. Any one of these can be arbitrarily selected and used in combination.

Note that the calculation formulas for calculating each P and Q above are related to the A phase, and in the case of the B phase and C phase, VabVca, Va, V
b and Vc are steps 5T21 and 5T2 in FIG. 7, respectively.
Appropriately according to 2! Can be replaced.

[Effects of the Invention] As described above, according to the present invention, a vector relationship is established in which the fault phase phase voltage on the load side at the disconnection fault point is approximately equal to half the sum of the phase voltages of the other two healthy phases. Since the structure is configured to determine whether the line is in good condition by arithmetic processing, it is possible to reliably detect disconnection faults and faulty phases without being affected by the negative phase voltage of the error that always exists when the line is healthy. It will be done.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a wire breakage/open phase detection device according to an embodiment of the present invention, Fig. 2 is a vector diagram for explaining the invention in detail, and Fig. 3 is an equivalent diagram of the symmetrical portion of the power distribution system in the event of a wire breakage. A circuit diagram showing the circuit, FIG. 4 is a vector diagram for explaining the invention in detail, FIGS. 5, 6, and 7 are flow charts showing the operation of the embodiment, and FIG. 8 shows the power distribution system. FIG. 9 is a block diagram showing a conventional wire breakage/open phase detection device, and FIG. 10 is a circuit diagram showing a symmetrical equivalent circuit of a power distribution system at the time of wire breakage. PTa, PTb, and PTc are potential transformers, and 10 is an arithmetic unit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) Voltage detecting means for detecting the phase voltage of each phase of a three-phase line, and whether or not each phase voltage obtained from the above detecting means satisfies a predetermined relational expression. In a wire breakage/open phase detection device comprising a calculation means for determining a state, and an output means for outputting a wire breakage/open phase detection signal when a wire breakage/open phase state is detected by the calculation means, Disconnection characterized by determining that the phase is in a disconnection/open phase state when the phase voltage vector of the generated phase is approximately equal to half the vector sum of the phase voltage vectors of two other healthy phases.・Open phase detection device. (2) In the disconnection phase detection device according to claim (1), it is determined whether the phases of the phase voltage vectors of each phase satisfy a predetermined relational expression, and the magnitude of these voltage vectors is It is determined whether or not the phase voltage vector satisfies a predetermined relational expression, and if both the above phase relational expression and the above magnitude relational expression are satisfied, the phase voltage vector
A disconnection/open phase detection device characterized in that it determines that the relationship is approximately equal to half of the vector sum of phase voltage vectors of a phase, and thereby determines that the phase is in a disconnection/open phase state.