JPS61109418A - Detector for disconnection of distribution line for three-phase circuit - 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 Field of Industrial Application The invention is applicable to three-phase circuits, for example three-phase power distribution Kj! 4: This relates to a distribution line disconnection detection device for a three-phase circuit that detects a disconnection of one wire at two times while distinguishing it from load fluctuation.

Conventional configuration and its problems In general, when detecting a single wire break in a three-phase distribution line, for example, as shown in FIG. A single wire break in the distribution cotton was detected.

In the figure, ■ is a distribution bus, 2 is a distribution line, 3 is a current transformer, 4 is an auxiliary current transformer, 5 is a fundamental wave filter, 6 is a filter that detects the positive phase component i, and 7 is a negative phase bone 12 is a detection filter, 8 is a detection means for detecting the positive phase change Δ■1, 9 is a detection means for detecting the negative phase change Δ■2, and 10 is each change Δ
11 is a settling section that sets the level; 12 is a calculation means for calculating Δiz/Δi; 13 is a calculation means for calculating Δiz/Δi; Comparison means for comparing the calculation output with a preset operating range; 14 a setting unit for setting the operating range;
15 is an output relay, and 16 is its connection.

Phase currents ia, ib, and fc flowing through the power distribution line 2 are each detected by a current transformer 3 and converted into a voltage via an auxiliary current transformer 4. Then, only the fundamental wave is extracted by the fundamental wave filter 5 and sent to each filter 6.7. Here, the positive phase component j l + negative phase component 12 is detected,
It is given to the detection means 8 and 9.

In the detection means 8 and 9, the positive sequence current and the negative sequence current change Δ
■1. Δ■2 is output and given to the determination means. Kogodeji 1
The level of each change is determined based on the level set by the setting unit 11, and changes that are equal to or higher than the set level are output.

The calculating means 12 calculates ΔL/Δ■1 on the change sent from the determining means 10, and provides the result to the ratio ΦQ means 13. Here, it is compared whether the calculation result is included in the operating range set by the setting section 14, and when it is included, it is output and the output relay 15 is operated. As a result, the contact 16 is closed to notify that a one-wire disconnection has occurred or to issue an alarm.

By the way, to explain the operating principle of the above-mentioned distribution line disconnection detection device for three-phase circuits, with the a phase as the reference phase, when the a phase is disconnected, Δiz/Δ■1 is 1, and when the b and c phases are disconnected, the vector operator is α(α−−1/2+dT/2)
Then, α and α2 become α and α2 as shown by the thin lines in FIG.

Δ■2/Δ■1 during single-phase load switching and 2-phase load switching
are respectively shown by the dashed line and thick line in the figure. Furthermore, Δiz/Δ■1 during 3-phase load switching is 0.
Therefore, Δiz/Δi.

By constantly detecting this, it is possible to determine whether a single wire breakage has occurred or whether there has been a load switching.

For example, when ΔL/Δ■1 is 1, according to the above, an a-phase disconnection has occurred, and according to the symmetric coordinate method, the change is Δ■1. Δ■2 is Δ■1=(Δ■8+α
Δi, 1α2Δic>y: +Δ■2− (Δ■8 +α
21. Since it is expressed as αΔi, )/3, Δiゎ−
Δ■． A certain place that comes out.

In this case, t is Δ■1 - Δ■2, and ΔL/Δ■+=1.

Δi due to load fluctuations other than L7 or 1-2.1 wire breakage.

-Δic may occur, and even though one wire breakage has not actually occurred (4), the same judgment as one wire breakage is made, resulting in malfunction.

In order to solve this drawback, the present applicant previously proposed a concept as shown in FIG.
(See No. 3).

In addition to detection based on the principle of Δiz/Δi, they focus on system phenomena that can distinguish between wire breaks and load fluctuations1-7, and by combining the detection of these system phenomena, malfunctions due to load fluctuations can be prevented. This is an attempt to make the detection of single wire breakage more accurate.

Zunawara, when a disconnection occurs in a distribution line, the sentence of the distribution line, 1 geo! Although the load on the distribution line changes, the load on the ground 4A does not change, and by detecting the change in the load on the ground as the change in the zero-sequence voltage 9 of the distribution bus Δ■0, this change can be detected. ΔGrief. The AND condition is established that the magnitude of is within the preset operating range (1Δ9o I≧K) and the current change ratio Δit/Δ■1 is within the preset operating range (oblique perspective part in the figure). It is configured so that it is output only when one wire is disconnected to notify the user that one wire is disconnected.

In the figure, 17 is an AND gate, and 18 is an OR gate.

With this improvement measure, the detection accuracy has become higher than in the conventional example in which determination was made only by Δfz/Δ■1. However, the reality is that there is still a risk that malfunctions may occur depending on the load fluctuation situation.

OBJECT OF THE INVENTION An object of the present invention is to provide a distribution line disconnection detection device for a three-phase circuit that has higher detection accuracy.

Structure of the Invention The distribution line disconnection detection device for a three-phase circuit of the present invention detects changes Δf+ and Δ■2 in the positive-sequence current and negative-sequence current of the three-phase circuit, respectively.
and the ratio Δ■2/Δ■1 of the positive-sequence current change Δ■1 and the negative-sequence current change Δ■2 detected by the current range-divided detection means. A three-phase section in which the magnitude of the zero-phase voltage change ΔVo detected by the first calculation means for calculating the calculation, the zero-phase voltage change ΔVo detection means, and the lower stage of the zero-phase voltage change detection stage is set in advance. a second calculating means for calculating the lower judgment stage and its phase to be output when one wire breakage is larger than the corresponding value; and an output means that outputs an output when both the phases toward summer are within respective preset operating ranges.

It is an AND condition between ΔL/Δ■1 and IΔVol, not Gノ. Determine the AND condition between these and the phase of Δ9oj4
rp', the product j is higher than the above improvement plan because it is closed.
When θ is 1'9, one wire breakage is detected.

1 again i pa, Δ standing. The significance of adding the phase to the criteria for determining one-wire breakage [V] will be explained based on FIGS. 4 to 7.

Figures 4 and 5 show model systems of three-phase circuit distribution lines,
194 years old transmission line, 20 is transformer, 21 is distribution bus, F1
~F□ is a power distribution line (feeder), and a plurality of power distribution lines F1 to FIn connected to one transformer 20 constitute a transformer bank TB. Reference numeral 22 represents a grounding transformer for a 9° big amplifier connected to the power distribution bus, numeral 22 represents the impedance of the grounding transformer 22, and 23 represents a load connected to the power distribution lines F1 to F.

P in FIG. 5 represents a break point occurring in the a phase of the distribution line F1. FIG. 4 shows the state before disconnection. CI B+Clb+
Ole""'Cma+ Cmb+ ', /ll
Ic is the ground capacity of each phase of each distribution line, Cla' +
CIb' + CIc' ~C,, IIClb +
Clc'' is the ground profile of each phase before and after the disconnection point.

V-, Vb, VC is the voltage to ground, 11 times 6. .

e ca is line voltage, ia, ib, iC is phase current of power transmission cotton 19, j Ia+ Tl1l++ l+c"-j
ma+ imb+ LL is the phase current of the distribution lines F, -F, the primary current of the r/3 var grounding transformer 22,
(n/3)i is the secondary current, (Va + Vb - I V
C) / n 4: I', secondary voltage; n 4; primary-secondary winding ratio of the I-connected transformer 22;

Load 23... has a zero power supply? l! o &:l Since there is no filtering, zero-sequence current i. , 4:4.14'l, 4:f23... can be ignored.

In the state shown in FIG. 4, (va + vb + L) /n = 39o /n - moxibustion ni/3 (2) holds true. Adding the left sides and right sides of equation (1), ja+jb→Ic ++-(lli+I+b”Tlc)
1...l(j +sa 1j nb" Lc)
River - (3) Here, if we put, 3 lo @! =3 j+o+・Old・・10B.・
(5), 3io is the total zero-sequence current supplied from the secondary side of the transformer 2o, and since the secondary side is a delta connection, 31o=0. Therefore, formula (5) is I-3f+o-1---t 3 ! no
--(li) Also, from (2) 2, substituting equation (7) into equation (6), -9°/2 ”” 3 i 10+...”3j
mn ・・・・・・ (△) (A) formula is the shape of distribution cotton 1
This is a basic formula that holds true regardless of f and 1r such as 1u.

Next, we will consider the zero-sequence voltage before and after the disconnection.

(1) Before the disconnection, the zero-sequence current of each distribution line F, ~D,...
(8) becomes. Also, Q,=Q. +αM, +α2 Summer 2 Nov + &;t: iF sum voltage, 9□ is the negative phase voltage, α is Bek I Luope 1/-ri, α-e Jl 20°, α
N-e J240°.

Line voltage Y of 111 line 21, + a b + dead bc +
When the death ca is in balance, V I''C,b 6-J 3'°15.vz=.

Tonagen, using this relationship in equation (8)... (10) jωC113+α2jωC1, +αjωClIc−Rei2
(11) If we set, equation (10) becomes as follows. Here, for example, Y+o is the first distribution line F1
is the zero-sequence admittance of , and ♀1□ is its negative-phase admittance.

Substituting equation (12) into equation (A), 4,/2= (♀1゜...10♀a.) <1゜+
(♀1□10...+?-z)V+...
...(13)♀1゜＋・・・・・・＋? stomach. −♀. )'
l +z+--+ '/11g -"9'2
of ··· ··
・If we take (14), then? . , <12 are the admittances of all the distribution lines F1 to F1, that is, the transformer bank, respectively, and by substituting equation (14) into equation (13), the back side is jl.

[■] After disconnection of one line - Assume that a disconnection occurs in phase a of the first distribution line F1 as shown in P in Fig. 5. In this case, as shown in FIG.
If the subsequent voltage of phase a is G, then......(15
) holds, so it becomes .

- Generally load impedance (2,',2.''

The ground impedance (1/jωCIm”+1
/jωC+b"+I/jωc+c"), so equation (16) is also: When the load is balanced, (2," = 2,"
==, L"'), a voltage 9X shown by equation (17) remains after the disconnection point P, and this causes a current to flow that charges the earth capacity itc I-", but this current is It is supplied from the c phase. Therefore, the zero-sequence current 3 of the first distribution line FI
According to Figure 6, f+o' is 311°'=jωC+a'
Va' + jωCab'Qb' + jωCI
c' Vc '→Jω'y+a″Vx+ j ω [
2 ,,'\7b' + j ω CIc
#Vc'=jω(C+a'+C+a#)
Vm 'tenjω(Cab'→C+b'') Vi+
'+jω (C1c' ” C1c#) Vc
'-jωC1, # α-'-9X) ・・・・・・(
19) Also, since , substituting equation (20) into equation (19), we get 31
+o' = j"C+aVa' + j ωC+b
Vb '10jωCI c </c'-jωC1m'(va' vX) ...
...(21) Similarly, the zero-sequence current 3T,ll' of the m-th distribution line F1 is expressed as 3 Lo' = J ``CmaVa' (J 6J
CAbVb '+jωc ac 18/ c'
------- (22) The impedance of the power transmission line 19 can be ignored compared to the load impedance of the power distribution line, and therefore the voltage drop due to the impedance of the power line 19 can also be ignored. The voltage across the line ca does not change before and after the disconnection, and as shown above, it becomes... (23). Also, using equation (18) and the relationship: =3 (summer,'-♀.')/2 =3 (9゜'+VI'+'l/,"C's
')/2-3(9+'+L')/2
= 3 V + ' / 2 = 3 V + / 2
・・・・・・(25)(23)～(25)
If we rearrange the equations using equations (2+) and (22), we get...(26), and if we further use equation (11), we get 311°'-♀. Va' ten♀, %. ! 1 no! , 1. According to this formula (A), [0'/2=31+o' 10...+3 is
o' Toki (♀1゜ten...+91゜)9゜' + (
? ＋□＋・・・・・・]−♀１□)′V.

-3jωC1□" QI/2 ......(28) Substituting equation (14) into equation (28), -<70'/2#♀oVo' 10♀29°-3j
err C,,” V+ /2 Transforming this, ......(C) is obtained.

rnl) Change in zero-sequence voltage due to one wire disconnection (T3),
From equation (C), the change in zero-sequence voltage before and after disconnection of phase A 1 wire Δ9o
6M0-Summer. -90'.

is given by

In the case of one wire disconnection in the b phase, as equivalent to equation (18), <tx = ('9c' + va')/2
−・・・(29)H&j(13C) in equation (19)
+a'Ha' -L) is jωC11,
'-9,), and similarly to equation (25), Qb '</X=3 (Vb ' Qo '
) /2-3 (9゜'``αz9.'+α9□' -＜1.l ) / 6-3α''Q
+ ' /2 -3α'' v+ /2 That is, in equation (i), substitute jωc, 1.'' for jωC, , II, and 9. α2</ instead of .

All you have to do is put . Therefore, in the case of C phase I line disconnection, jωC+a in equation (i)
” instead of jωC, c#, and instead of Q, α9
．． All you have to do is put . Therefore, comparing equations (i) to (iii), C2 is a 120° clockwise rotation and α is a 240° rotation in the same direction, so ΔV at the time of the l wire breakage
It can be understood that the phase of o has a phase difference of 120° depending on the disconnection phase.

FIG. 7 shows this situation. This figure is based on the line voltage vabc = white, -, and the reference phase angle -c Nr determined by the transformer bank of θ(, 1)
2′+, this group? The i rainbow phase angle θ is the central angle for the a phase and the central angle for the C phase is 120° from the angle θ, and the central angle for the 1) phase is 120° from the angle θ. Then, the load θp′l height f
Within the range of ±φ from each central angle and within ∆, considering the nonce. The region where the magnitude of is larger than ■ is defined as the operating range of each phase.

(1) - 2 included in the expression (mountain)? . , c, a”.

C11+"+Clc" etc. are transformer bank TB
It is a fil specific to . Therefore, the reference phase angle θ also differs for each transformer bank TB. This reference phase angle θ is
Easy to use by the method shown in Figure 8! ■ can be found.

That is, the capacitor 24 is connected to one of the distribution lines F, -F.
By connecting a series circuit of a switch Sw and a switch Sw, θ can be determined by opening and closing the switch Sw. ′:1 When the capacitance of the capacitor 24 is C, when the switch Sw is on, from (B), if C is selected so that jωC is smaller than Yo by 1·min, then (30)831 , if,</ with switch Sw turned off.

From formulas (31) and (32), the phase of Δ9o when the I capacitor is open is Δ9o when the A phase 1 wire is disconnected, based on 9I. The phase is the same as that of ((i) 2).

As shown above, since V I'"i abe-J3°°Ob, instead of tl, self-ah"V,, -summer, -9° may be used as the standard, and according to this, when the capacitor is opened, It is possible to determine the phase of ΔVo when one wire of the a phase is disconnected using Vab as a reference, that is, the reference phase angle θ.

Below 1-, the phase of 1 mm and Δ■0 is used as the criterion for one wire breakage t
I confirmed that it would be iK.

Note that only the magnitude and phase of Δ9o are used as the criterion for L7, Δ
■2/Δ■1 may be removed, but in this case, even if 1, Δ9o
may change and fall within the operating range. In other words, it causes a misjudgment. Therefore, it is necessary to use Δiz/Δ■1 as the criterion.

The concept of the structure of this invention is shown in FIG. 31 in the figure
32 is a 6M means for determining and calculating the magnitude and phase of Δiz/Δl+. means for determining and calculating the magnitude and phase of
33 is an AND gate, 34 is an OR gate, and the output S from the OR gate 34 is for detecting that one wire disconnection has occurred in one of the a''-C phases,
The direct outputs S, ~Sc from each AND gate 33 are for detecting when one wire is broken in each phase individually.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 2 45, 1- and FIG.
IIC The same reference numerals in Figure 9 of the previous example are support 1! It is the same as the l element. These elements 1 to 16 are! +,!
z, determines and calculates whether Δiz/Δ■1 is within a predetermined operating range (see Figure 1), and outputs an alarm or warning signal -υ when it is within the operating range. It is.

22 is the same V as shown in FIG. 6, which is a pickup grounding transformer and is connected to the power distribution mother 4Jill (21), is the impedance of the grounding transformer 22. 4
0 is an auxiliary transformer, 41 is a fundamental wave filter, and 42 is a zero-phase voltage change detecting means for detecting a change in zero-sequence voltage of 9 degrees, and the detected change is Δ. is input to the determining means 43, where ΔV.

The magnitude of I7.1 is set in advance by the setting unit 44.
, it is determined whether or not the value is large. 1ΔQo l≧
Output when 1. 45 is Δ Mamoru. is a phase calculation means, and its output is input to the comparison means 46. here,
The phase of Δ9o is the X phase (
It is determined whether the current is within the operating range (see FIG. 1) of the a-phase, b-phase, and C-phases.

Outputs when G is within the operating range.

, I O&; The output is input to relay 15. 49 is the first. Second
The output means includes comparison means +3.4.6, Antogame 1-48, relay 15, and the like.

1st. When there is an output from both of the second comparison means 13 and 46, the AND gate 48 outputs an output, the relay 15 is driven, and the relay contact 16 is turned on, notifying or warning that one wire has been disconnected. Ru.

The above is described in Flowchart 1 in Figure 3. (I will explain both later.

Is the positive sequence current i+ and the opposite phase in step ■? kN:,
Calculate j 1. Positive phase change Δj+ at step ■
and calculate Bl of the reverse phase degree fraction Δ■2.

In step ■, 1Δlt l is set to 4,1 on the settling rail.
, is larger. N [“If it is l, return to Suu-sopu■.’/F, if it is S, it will be Suu Y
Move to knob ■. In step (2), it is determined whether si, r, 1Δiz l is larger than 2 at the settling level. If NO, return to step ■. If YES, move to step ■.

In step (2), the ratio Δjz/Δj+ is calculated.

In step (2), it is determined whether the ratio ΔL/Δ■1 satisfies the condition (r). The [γ] condition means that the radius (in FIG. 1) is in the range of γ1 to γ2. If No, move on to step 0 of “before wire breakage detection”.

If YES, move to step ■.

In step (2), it is determined whether the ratio Δiz/Δ■1 satisfies the [β] condition. The [β] condition means that the angle is in the range of ±β° in FIG. If No, move on to step ``before detecting disconnection''. If YES, move to step ■.

In step ■, Δt0 is calculated, and in step ■, 1Δt0 is calculated.
Mamoru. 1 is greater than the settling level I4. If No, the process moves to step O "before wire breakage detection". Y
If ES, move to step [phase].

6M in step [phase]. is the x phase (a
phase, B phase, C phase) is within the operating range. If NO, move to step ``Before detecting disconnection'' and press Y.
If it is ES, the process moves to step @ of "disconnection detected" and is output.

Effects of the Invention According to the present invention, Δjt/Δi and Δ! . Since the determination criteria are not only the AND condition with the magnitude of Δt0 but also the AND condition with the phase of Δt0, there is an effect that the detection accuracy of single wire breakage can be improved.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the structure of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a flowchart thereof, Figs. Fig. 7 is an explanatory diagram of the detection area shown in a complex plan view, Fig. 8 is an explanatory diagram of determination of the reference phase angle, Fig. 9 is a block diagram of the conventional example, and Fig. 1
Figure 0 is a complex plan view, and Figure 11 is a conceptual diagram of the structure of an improvement plan. 8... Positive phase change detection means, 9... Negative phase change detection means, 12... First calculation means, 42... Zero phase voltage change detection means, 43... Determination means , 45...second
calculation means, 49... output means

Claims (1)

[Claims] Change amount Δ■＿ of each positive sequence current and negative sequence current of three-phase circuit
1. Current change detection means for detecting Δ■_2, and positive sequence current change Δ■ detected by this current change detection means.
Ratio between _1 and negative phase current change Δ■_2 Δ■_2/Δ■_
1 and a zero-phase voltage change Δ■_
0 detection means and the magnitude of the zero-phase voltage change Δ■_0 detected by this zero-phase voltage change detection means is larger than the preset value corresponding to one wire break in the three-phase section. a second calculation means for calculating the phase of the judgment means and the second calculation means for calculating the phase thereof; A distribution line disconnection detection device for a three-phase circuit, comprising an output means that outputs an output when the operating range is within the operating range.