JPH0634022B2 - Parallel multi-line ground fault fault location method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a parallel multi-line ground fault home point locating system in a high resistance grounding system.

(Prior Art) A fault point locating method based on a zero-phase current shunt ratio is generally used for locating a fault point for a ground fault in a parallel two-line transmission line.
The principle of the method based on the zero-phase current diversion ratio will be described first with reference to FIGS. 3 to 4.

FIG. 3 shows a system diagram (single-phase representation) of two parallel lines, A,
B is the bus line 1 on the self-end side (grounding device ground point side) and the mating end side
L and 2L are parallel rounds between bus lines A and B. In the figure, it is assumed that a 1-line ground fault has occurred at the point F of the line 1L. The zero-phase equivalent circuit obtained from the symmetric coordinate method for the above failure is represented as shown in FIG. Where x is the distance from the self-end to the fault point F when the total length of the line is 1, ₀ is the zero-phase impedance per unit length of each line, ₀₁ and ₀₂ are the zero-phase current of each line, and ₀ f is It is the zero-phase current at the failure point, and these can be expressed by the following relational expressions. ₀ f = ₀₁ + ₀₂ (1) x _{0 01} = l _{0 02} + (l-x) _{0 02} (2) From equations (1) and (2) The above equations (3) and (4) give the distance from the self-end side of the lines 1L and 2L to the failure point, respectively.

By the way, in the system shown in Fig. 3, the other end (end B)
A device having a zero-phase impedance, for example, an arc-extinguishing reactor may be installed in the device, but in this case, the influence of the zero-phase impedance will be prominently generated, and an orientation error using the equations (3) and (4) will occur. This will be elucidated below. In FIG. 5, R _e is an arc-extinguishing reactor provided on the other end side (B end), and a zero-phase equivalent circuit when a one-line ground fault occurs at point F of the line 1L is the same as in FIG. Show.

Here, _{0 '1:} zero-phase current to the point F than B-end _0': B end of the zero-phase voltage: B end of the zero-phase impedance ₀ f: zero-phase voltage ₀ f point of failure: the zero-phase point of failure If it is a current, then ₀ f = ₀ −x _{0 01} (5) ₀ f = ₀ −l _{0 02} − (l−x) _{0 0} ′ ₁ (6) ₀ ′ ₁ ＝ _{02 −0} ′ / (7) To do. From equations (5) and (6), x ₀₁ = l ₀₂ + (l−x) ₀ ′ ₁ (8) In equations (7) and (8), ₀₁ +1 ₀ ′ ₁ = ₀ f, that is, ₀ ′ ₁ = ₀ f With _-01 From equations (9) and (10) Applying the principle of the zero-phase current diversion ratio here, And the second term on the right side of equation (13), that is, Causes an error. Zero-phase voltage is generally high in a high resistance grounding system (because of a complete ground fault, the phase voltage is in a healthy state).
The magnitude of ₀ '/ may be similar to that of ₀ f. Therefore, the fault location based on the zero-phase current shunt ratio cannot be applied to the system having the neutral point impedance, that is, the zero-phase impedance, at the other end as described above.

(Problems to be Solved by the Invention) In the present invention, as described above, the second term on the right side of the equation (13) becomes an error factor in the system having the zero-phase impedance at the other end. It is an object of the present invention to locate the distance to the failure point with high accuracy without being affected by the zero-phase impedance.

(Means for Solving Problems) The principle of the system according to the present invention will be described first. 7th
The figure shows a system diagram (single-phase representation) of parallel n lines, where A and B are the self-end side (orientation device installation point side) and each partner's busbar, 1L-
nL is each parallel line provided between the buses A and B. Re is an arc-extinguishing reactor provided on the other end side (B end) as described above. FIG. 8 shows a zero-phase equivalent circuit when a one-line ground fault occurs at the point F of the line 1L as described above.

Here, _{0 '1:} zero-phase current to the point F than B-end _0': B end of the zero-phase voltage: B end of the zero-phase impedance ₀ f: zero-phase voltage ₀ f point of failure: the zero-phase point of failure If the current is the same as above From equations (14) and (15), x ₀₁ = l ₀₂ + (l−x) ₀ ′ ₁ (17) Also, from equation (15) ₀₂ = ₀₃ …… = _{0n Using} this in equation (16), ₀ ′ _{1 = (n-1) 02} - 0 '/
(18) (17) from x ₍₀₁ + ₀ Thus _{'1) = l (02 +} 0' 1) If equation (18) is used for this equation, To get It is understood that this equation (19) is the orientation calculation equation based on the extended zero-phase current shunt ratio, and if ∝ (infinity) and n = 2 are satisfied, it agrees with the above equation (4).

Equation (19) requires zero-phase current information of the other end, that is, B electric station, in addition to the zero-phase current information directly obtained at its own end, that is, A electric station. Ideally, it can be located using only the current and voltage information of the local electric station A, but in the high resistance grounding system, the magnitude of the neutral point impedance of the transformer is much larger than the line impedance, and ₀ '= The voltage drop l _{0 02} on the line at ₀ −l _{0 02} is negligible compared to ₀ . Therefore, there is no problem believe that _{0 '0.}

From the above, as a one-wire ground fault fault localization formula for high resistance grounding parallel n line with neutral point impedance at the other end To get

Where ₀₁ : failure line zero-phase current ₀₂ : sound line zero-phase current ₀ : self-end zero-phase voltage: opposite end neutral point impedance When applying the formula (20), it is determined that there is a failure line from n lines. It is necessary to select a healthy line, and the selection of this faulty line and the orientation to the fault point will be described in detail below.

Since ₀₂ = ₀₃ = ... = _0n from equation (15), the denominator of equation (20) is Becomes

Here, x _i calculated by the following equation (20) is determined for the i line.

(However, i = 1,2,3, ..., n) Using the previous equations (17) and (18) and the relationship of ₀₁ + ₀ ′ ₁ = ₀ f, ₀ ′ ₀ Or Therefore, by using the equation (23) in the equation (21), x ₁ = nl− (n−1) x x ₂ = x ₃ = ... x _n = x, and x ≦ nl− (n−1 ) X, it can be seen that the calculated value x _i of the faulty line is the maximum, and that the distance to the fault point is given by the calculated value x _j of other than the faulty line. Therefore, it is possible to select the faulty line and locate the faulty point in the following manner.

First, the previous equation (21), where i = 1,2,3, ..., n To calculate. According to the above formula Is calculated. The iL line with the maximum value is selected from these x ₁ , x _2, ..., x _n as the faulty line. Furthermore, other than x _i x _j
Is selected as the reference value up to the failure point.

FIG. 2 is a flow chart showing the procedure of the above process in detail, and it is judged in step (1) whether a ground fault has occurred. When the zero-layer voltage ₀ is greater than or equal to the preset set level L, the process proceeds to step (2). In step (2), the current per line that flows into the zero-phase impedance of the other end is calculated. In step (3), the current component flowing in the zero phase impedance is removed. In step (4), the distance is calculated by the current diversion ratio. In step (5), select the faulty line. At step (6), the fault point orientation values are averaged (calculation errors are averaged). Step (7)
Outputs the above standard value. Finally, in step (8), it is determined whether or not the ground fault has disappeared, and if YES, the process ends.

As described above, according to the principle of the present invention, it can be applied to a parallel multi-line transmission line with high resistance grounding and has a neutral point impedance (zero phase impedance) at the other end, and in principle, there is almost no error. The feature is that there is no problem and highly accurate orientation is possible.

(Embodiment) A concrete embodiment using the method of the present invention is shown in FIG. Zero-phase currents ₀₁ to _0n for each line are obtained by the current transformers 1CT to nCT provided at the ends of the lines 1L to nL. 1AXCT to nAXCT are auxiliary current transformers for converting the zero-phase currents ₀₁ to _0n into voltages of appropriate values, and PT is an instrument transformer to obtain the zero-phase voltage ₀ of the system. AXPT is an auxiliary transformer. AF is an analog filter provided for cutting the harmonic components contained in the zero-phase voltage ₀ and zero-phase current ₀₁ to _0n information obtained from the system, respectively, and removing the folding error. Each S / H is a sample and hold circuit, and based on a command from the control circuit CON, for example, performs 12 times (30 ° interval) simultaneous sampling based on the command from the control circuit CON and holds the sample value. To do. MPX is a multiplexer that sequentially switches and outputs the sample value, and A / D is an AD converter that converts the analog sample value into a digital amount. The CPU is an arithmetic unit such as a microprocessor that stores the digital information and at the same time performs a predetermined arithmetic operation, and OUT is an output circuit.

The MPX, A / D, and CPU perform predetermined operations based on commands from the control circuit CON, like S / H.

If a ground fault occurs in any line, zero-phase voltage ₀ occurs and zero-phase currents ₀₁ to _0n flow in each line at the same time, so these are stored in the CPU as sampling data. Then, the CPU extracts the fundamental wave component from the sampling data, and since the set level L and the line length 1 for the zero phase voltage ₀ are known, the calculation is performed according to the equation (21). This calculation output is nothing but the distance x to the faulty circuit and its fault point.

(Effects of the Invention) As described in detail above, according to the present invention, in addition to being applicable to a system having a neutral point impedance at the other end in a high resistance grounding parallel multi-line transmission line, in principle, almost no error occurs. In other words, it has the effect of realizing highly accurate fault location.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart showing a processing procedure according to the present invention, FIG. 3 is a single line system diagram of a parallel two-line transmission line, and FIG. Fig. 5 is a single-line system diagram with a neutral point impedance at the other end, Fig. 6 is a zero-phase equivalent circuit diagram at the time of failure, and Fig. 7 is a parallel diagram for explaining the method of the present invention. FIG. 8 is a single-phase system diagram of the n-line transmission line, and FIG. 8 is a zero-phase equivalent circuit diagram at the time of failure. 1L to nL …… Line Re …… Device with neutral impedance AF …… Analog filter S / H …… Sample hold circuit MPX …… Multiplexer CON …… Control circuit A / D …… Analog digital converter CPU …… Arithmetic unit

Claims (1)

[Claims] 1. A zero-phase voltage of a self-terminal electric station that occurs at the time of a one-wire ground fault in a system of a high resistance grounding parallel multi-line transmission line in which a transformer installed at the other end of the bus has a neutral point impedance. And the zero-phase current flowing in each line as input, x _i However, i = 1,2,3, ... n n: Number of lines _0i : Line zero-phase current ₀ : Own zero-phase voltage: Opposite bus end transformer neutral point impedance l: Calculated by line length, and output this calculation It is determined that the i-line is a failed line from x _{i, which} has the maximum value from x ₁ , x ₂ , ..., X _n , and x _i
A parallel multi-circuit ground fault fault location method in which the operation output x _j other than is located at the distance from the local electric station to the fault point.