JPS5853770A - Detection of disconnection for line - Google Patents

Abstract

PURPOSE:To detect the disconnection in a line for feeding power to a 3-phase load by utilizing the fact that the ratio of absolute values of differences in the variation of vector currents as determined between phases differs when one wire is disconnected from that when the load is opened. CONSTITUTION:When currents Ia-Ic respectively in phases A-C vary to Ia'-Ic', variations are represented by DELTAIa-DELTAIc. In a 3-phase-balance load, vector diagrams of the line current are as shown by A-D when one wire is disconnected in the phase A, when the single load is opened in the phase BC, when the V load is opened in the phases AB and CA and when the 3-phase load is opened. Based on this, the equation to determine the disconnection index STa in the phase A is given by STa=¦(DELTATb-DELTAIc.a)/DELTAIa¦. Similarly, the equations STb and STc to determine disconnection indexes are obtained when disconnection occurs in the phases B and C. Based on these values, various states can be judged from the table.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a disconnection of an electric line that can reliably and easily distinguish between a disconnection of an electric line supplying power to a three-phase load and an open load at a substation.

This relates to a detection method.

The distribution line is of the general type with a neutral point and is not grounded, and the system is tree-like. Accidents such as ground faults and overcurrents on distribution lines are detected using ground fault relays, overcurrent relays, etc., but there are many ways to improve the reliability of distribution lines and ensure safety. For this reason, the use of insulated wires for railway lines is progressing. However, even if an insulated wire breaks and falls to the ground, because the insulated wire has a covering, the internal conductor does not come into contact with the ground, so no zero-sequence current flows, and the substation detects this as a ground fault. In some cases, this was not possible, creating an obstacle for security and power supply.

In order to solve the above-mentioned problem, the present invention has been developed to solve the above problem.When the line current of each phase changes due to one line disconnection and load opening of the distribution line that supplies power to a three-phase load, for example, when the line current of each phase changes, Find the absolute value of the ratio of the vector change in the line current of the human phase and the vector difference of the vector change in the line current of the B phase and C phase, and also calculate the above for the remaining two phases, that is, the B phase and C phase. Find the absolute value in the same way. A wire breakage detection method for detecting a wire breakage by utilizing the fact that the sum of the three absolute values obtained in this way or the absolute value of each of them has a different relationship between when one line is broken and when the load is released. was provided.

Hereinafter, the disconnection detection method of the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing a line in which a load, L1, and a load L2 are connected to a substation Tl, and the line current 1o in the substation is in a loaded state or in a line state connected only to that load. The line current xi of the load L1 which does not change and the line current of the h load L2 whose load condition or line condition changes ■2
However, the line impedance between the substation and each load is ignored as it is smaller than the impedance of each load. Each of the line voltages has a phase difference of 120°, and even if the line condition of load L2 changes, the line voltages shown in FIG.
It is assumed that the phase difference between each line voltage and each line current at a point does not change. Therefore, the change ΔIO in the line current at the substation is the change Δ! due to the change in the line condition of the load L2. Depending only on the goose, the load L1
Since the change amount is Δ■o-0, the load L'1 will not be considered in the following explanation. Therefore, the change in the state of the line of load L2 can be shown by the equivalent circuits shown in FIG. 2 (A) to (0). However, Fig. 2 (A) is the equivalent circuit when one human phase wire is disconnected, and Fig. 2 (CB)
is the equivalent circuit when the BC phase single-phase load is released, and the same figure (C)
is an equivalent circuit when the AB/CA phase V negative load is opened, and (D) in the same figure is an equivalent circuit when the 3-phase load is opened.

In Fig. 2 (A) to (0), the line currents of phase A, phase B, and phase C in a steady state are expressed as Ia, line voltages of Ib and Ia, vab, vbC, Vca, and loads connected between each line. Let the currents be Iab, Ibc and lea, and their absolute values be iab, ibc
and ica, and the power factor angles of each load are α, β, and r, each line current is: Iamlib-1cie=iabej'-1oaej'
-a --... 11) Ib-Summer bc-1
abesibaejβ・*”-1abej“
・1211ca*Ici−Ibcmiaaej′・t1bocjβ−1” −(3) However, l!
ejzu, @"-@j"4'.

Here, when the human phase line is disconnected as shown in No. 211 CA), the current in each line after the disconnection is Im', Ib'
and Ic', the load current is 14b', Ibo
If 'Akiyo and 165 ni' is set, then Ia' = Q Ic' = -1b', and the changes in each line current ΔIa, ΔIb and ΔIc
is as follows.

ΔIa=I'a-Ia=-(iabej"-1caej
'-a) ...-(4) From (5) and (6), (Jun style and (9) -(*abej''-i paej' aa) = -ic
a(ej'-ej'-a) IIs ica =-1(ΔIbejr-ΔIcej'-a)
1B) IIs If the equation (8) is transformed, and the absolute value of the right side is taken, the following equation becomes an equation for determining the phase breakage index STa.

llb −ΔIc−a STa = l l ・・
``αeΔIa'' Similarly, the formulas for determining the disconnection index at the time of B-phase and C-phase disconnection are as follows.

=12 and 2"12-1 ・・・αυΔ1b STc Snow 1 1 ΔIc Hi I l ・・
-α2ΔIc Next, using the above formulas 00 to 12, the values of the wire breakage indices STa, STb, and STc at the time of one wire breakage and when switching various loads are determined with reference to FIGS. 3 to 7.

Figures 3 (A) to CD) show AB, CA when one incoming wire is disconnected in a three-phase balanced load, and when the BC phase single-phase load is open.
It is a vector diagram of the line current in the substation when the phase V negative load is released and the 3-phase load is released, and the line currents Ia, Ib, and Ic of the A phase, B phase, and C phase fluctuate, and Ia' respectively. , Ib' and Ic', the change amount ΔIa in each of these vector values.

, 1flb and ΔIC are shown. Figure 4 (A),
FIG. 5(A), FIG. 6(A), and FIG. 7(A) are vector diagrams showing vector value changes jla, llb, and IIs in FIG. 3(A) to (0), respectively. be. For a ship, changes in line current of each phase ΔIa, ΔI
The vectors representing b and IIs have a ratio of their respective absolute values, that is, 1ΔIa1. ':lΔIbl:l
For convenience, ΔIal is 2:1:1 for Fig. 4 (A).
5 (A), 6 (A) and 7 (
For A), the ratio is 0:1:1, convex: 1:1, and 1:1:1. ' Mountain A phase 1 wire disconnection (:) In formula 01, multiplying IIs by fish is
ΔI.

The purpose is to rotate the vector 120° counterclockwise, so the vectors lla and llb shown in Fig. 4(A)
The relationship between and IIs is as shown in FIG. 4(B). This will happen.

+1) STb at this time is determined as follows. Q
l) If IIs in equation (+) is rotated by 120 degrees, the vectors l1m, llb and Δ
The IC relationship is as shown in Figure 4 (C), 1ΔIo
-J, Iaa q l is 6, and 1ΔIbl is 1, so STb is west.

(-) Furthermore, S T c at this time is determined as follows.

■If we rotate llb in the equation by 120 degrees as in (1), we get
IIs, llb td and IIs in FIG. 4(A)
The relationship is as shown in Figure 4 (D), 1Δ1m−Δ
1b-al is west and 1ΔIol is 1, so ST
c is west.

(2) BC phase single phase load release If the same steps as described above are repeated, Fig. 5(A) becomes Fig. 5(B), Fig. 5(C), and Fig. 5CD), respectively. Further, STb and STo are both 1-1.

(3) ^B, CA phase V load phase number load release If you do the same as above, Fig. 6 (A) will become the ( of Fig. 6 (B), Fig. 6 (C), and Fig. 6 (D)), respectively. 4)
If the three-phase load is released in the same manner as described above, Fig. 7 (^) will become as shown in Fig. 7 (B), Fig. 7 (C) right, and Fig. 7 (0), respectively, and 1Δlb - ΔIo −@l*IΔIc−ΔIa
-al and 1ΔIa-Δlb, a l are both 0
Therefore, STa = STb = STc - Q.

Table 1 shows the values of STa, STb, and STo when one phase input wire is disconnected and when various loads and loads are released.

Table 1 This table shows STa, STb, and ST when one phase input wire is disconnected and when the load is open in a three-phase balanced load.

This shows that these values are different between these two states. Therefore, a value for determining a disconnection is set, for example, 1.5, and as a disconnection condition, 9-z-i-ripe or two of STa, s"rb, and STc are 1.5 (however, the value of ■ ) If it is considered as a wire breakage when it is larger than that, then as can be seen from Table 1, it is possible to detect a single wire breakage in a three-phase balanced load.

Furthermore, in order to improve the detection of disconnection, STa, STb
The value obtained by adding the three values of S T a and S T a , for example, 4.0 (however, the value of ψ is not taken) may be used as the value that determines that the wire is disconnected.

However, in the case of an unbalanced load, the values shown in Table 1 will change depending on the degree of unbalance, and the values shown in Table 1 will change depending on the degree of unbalance.Specially, the times when one wire of the A phase is disconnected and when the V negative load of the AB and CA phases is opened may overlap. Ru. Therefore, in order to distinguish between a single wire breakage and a V load release, it is necessary to set a range of unbalanced impact, and under that condition, when the human phase single wire breaks, An, and the CA phase V STa when the load is released.

By calculating STb and STa, it is necessary to determine the value at which it is determined that there is a disconnection.

The calculation of this value will be explained below.

(@) Human phase l line disconnection ""i,, (>O), and this is expressed by equation (4) or (
6) Substitute into the formulas, and then convert these formulas from 00 to +12
The equations obtained by substituting into equation 1 are as follows.

Also, ST = STa + STb + ST.

(b) AB, CAA phase load release As shown in Figure 2 (C), each line current I after the load is released
a', Ib'ji and Ic' are Ia' = Q ib' = ibaejβ aN Ic'trim - i be ejβ・-, and the changes in each current are ΔIm, ΔIb and Δf
c is numbered as shown in the following equation.

ΔIa−−iabej″+1caejr−a
=・C7ηΔlb y= i abej″
...a&jla y -i aa
ej'-a - [91ba to a9
The formulas obtained by substituting these formulas into the α0 formula to αari formula are as follows, respectively:
T=STa+STb+STc STa, STb and STc obtained in this way
For, 1a-rl≦ with (α-r) as a parameter
Draw a graph of the relationship between Y in the range of 30° and STa, STb, and STc when one phase input wire is disconnected and when the V load is opened (see 1). In this graph, Y
STa, STb and STc when =1(7)
A value A for determining a wire breakage is set in advance based on the value of , and the following three wire breakage conditions are considered based on the value A.

P; When two of STa, STb and STc (N shear force) are greater than A, the wire is broken.

Q: When at least one of STa, STb, and STC is greater than A, it is considered as a disconnection.

However, the flash value shall not be taken.

R: When ST is larger than A, the wire is broken. However, ψ
Assume that the value of is not taken.

Therefore, in order to find this person's value, change A variously so that the disconnection conditions P, Q, and k are satisfied within the ranges of 1α-r1≦30° and 0.1≦Y≦2. From the above-mentioned graph (not shown), the range in which each disconnection can be detected and the range in which V load release can be detected are made into a table (not shown). For example, if a disconnection or load release can be detected, mark it with a circle, and if it cannot be detected, mark it with an x.

From this table, it is possible to know, for each of the disconnection conditions P, Q, and K, A that makes the disconnection detection range as wide as possible and minimizes the malfunction when the V load is released. Next, by making a farce of each A, we plotted the range where wire breakage can be detected and the range where V load release can be detected from the table (not shown) above, with Y on the horizontal axis and (a-r) on the vertical axis. By creating a table, it is possible to confirm the detection of a single line disconnection in a certain Y and <a-r> range.

In this way, for the disconnection condition P, A=1.15
In this case, the condition for Y and (α-r) is 0.4≦Y
≦2.0, -30'≦a-r≦-) -10°. In addition, the disconnection condition Q is A-1,63, and the conditions for Y and <a-r> are 0.1≦Y≦2.0,
-30°≦t-7≦+10°.

Furthermore, regarding the disconnection condition k, it becomes A-3,56,
The condition for Y and (σ-r) at this time is 0.5≦Y≦2.0
, -106≦α−r≦+30°.

Therefore, if any one of the disconnection conditions P, Q, and 11 is satisfied, it is possible to determine whether one wire is disconnected or the load is released. This is clear from the fact that the human-phase single wire breakage force f in a three-phase balanced load can be detected from the value shown in the first table number ζ.

The above explanation was about detecting a disconnection in the human face, but it can also be applied to detecting a disconnection in the B phase or C phase.
It is clear that detection can be performed using the same method as described above.

As described above, the wire breakage detection method of the present invention detects load changes such as three-phase load opening, ■ load opening, or single-phase load opening, as well as one wire or wire breakage, whether it is a balanced load or an unbalanced load. It is beneficial to have one point that can be detected at a substation.

[Brief explanation of drawings]

Figure 1 shows the load L on substation TI! Figures 2 (A) to (D) are equivalent circuits when one phase input wire is disconnected, BC phase single phase load relief, and AB and CA phases. Figures 3 (A) to (D) show the equivalent circuit when the V negative load is opened and the equivalent circuit when the 3-phase load is opened, respectively. vector diagram of the line current in the substation when the AB/CA phase V negative load is opened and the 3-phase load is opened, 4th
Figure (A). Figures 5(A), 6(A) and 7(A) are vector diagrams showing vector value changes ΔIa, Δlb and jla in Figures 3(A) to (0), respectively. Figure 4 CB) to (D), Figure 5 CB) to (0)
, Fig. 6(B) to (0) and Fig. 7(B) to (
D) (Vector diagram after rotating the vectors shown in Fig. 4 (A), Fig. 5 (A), Fig. 6 (A), and Fig. 7 (＾), respectively, counterclockwise by 120 degrees Agent: Patent attorney Hiroshi Nakai Engraving of the drawing (no changes to the content) Figure 1 T+ (C) (0) Figure 8 (A) (B) (
C) (D)AB
-CA phase TμKIM release 3-phase load pre-release procedure amendment (voluntary) 56th day of chant 1゛uta^-26th Patent Office Director-General 1, Indication of case Patent application No. 152484/1984 2 Name of invention Electric wire Method for detecting line disconnection Relationship with the incident to be corrected Patent applicant Kansai Electric Power Co., Ltd. (026) Osaka Transformer Co., Ltd. Representative Address 2-11-1 Tagawa, Yodoyo-ku, Osaka 532
No. 1 [Engraving of drawings (no changes to the contents)]

Claims (1)

[Claims] 1. The amount of change in each vector value when the line currents 1a, Ib and IC of the three-phase power line change to Ia', Ib' and Ic', respectively ΔIa = Im' - Im,
ΔIb e=Ib'-Ib and ΔIc=Ic'-
From 1a, disconnection index ST at the time of A phase, B phase and C phase disconnection
a, sTb and STc Δsummera-Δlb, aSTcdayl-10,000-1-1, and calculate these STa, STb and STa
A wire breakage detection method for detecting a wire breakage by detecting that the values of are in a predetermined relationship. -2, the predetermined relationship is STa, STb and STc
The method for detecting disconnection in an electric line according to claim 1, wherein any two of the values of are larger than 1.15. 3. The predetermined relationship is STa, STb
and at least one of the values of STc is 1.6
3 (however, the value of ■ shall not be taken). 4. The predetermined relationship is STa + STb +
The method for detecting disconnection in an electric line according to claim 1, wherein the value of STa is larger than 3.56 (however, a negative value is not taken).