JPS62209372A - Method for live wire type measurement of constant of distribution line by current neutralizing method - Google Patents

Abstract

PURPOSE:To make it possible to measure the constant of a distribution line simply and accurately, by injecting triangular wave voltage to take out the leak current of the distribution line and transferring the constant of the distribution line to a constant element to be controlled using an auxiliary conductor. CONSTITUTION:On the way of the distribution line of a user, triangular wave voltage (e) is injected as one for testing by an injection device IT. The voltage (e) passes through the earth electrostatic capacitor and earth insulating resistor of each line to be guided to the ground and a current is refluxed through the earth resistor of second kind earth construction provided to the neutral point of a pole transformer in the secondary side thereof. At this time, an auxiliary conductor 5 is connected so that a current flows through a clamp type current transformer CT to a reverse direction to be refluxed to a constant element 6 to be controlled and, when the constant of the distribution line coincides with the value of the element 6, the interlacing magnetic flux of the current transformer CT comes to zero. A control circuit 7 is operated so as to bring detection voltage to zero. As a result, each constant of the distribution line of the user can be known on the basis of the value of the element 6.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention measures wiring constants such as insulation resistance to ground while the wiring is in a live state, for example, in the wiring of a low-voltage consumer to which commercial frequency voltage is supplied. Regarding how to.

(Prior art) For example, to measure the ground insulation resistance of general low-voltage customer wiring, open the customer's service switch, connect the load side all together, and connect it to the earth using a megger (DC type insulation). The method of measuring with a resistance meter (resistance meter) has traditionally been used, but this method has the inconvenience of temporarily causing a power outage on the consumer side.Especially in recent years, as the number of consumers equipped with computer-like equipment has increased, these equipment It also has a large impact on.

The reality is that due to changes in family structure and lifestyles, the number of households where people are away during the day is increasing, which is causing problems in fulfilling the obligation to take measurements at regular intervals.

For this reason, a method similar to the past method was proposed so that the insulation resistance to ground can be measured while the line is still live.

a. The zero-phase current transformer method uses a clamp-type current transformer to distribute electricity to customers' homes. A device that measures the leakage current of a batch of wires.

b. From the relationship between the DC component in the leakage current flowing at that time and the applied DC voltage when applying a DC voltage in series to the grounding wire of the second type grounding work installed on the secondary side of the pole transformer. Something that calculates insulation resistance.

C0 Uses low frequency alternating current voltage instead of the direct current voltage mentioned in the previous section.

However, in the case of a single-phase three-wire power distribution system, the a-attraction type has a defect that cannot be detected because the voltages on both sides of the grounding wire are in opposite phases, canceling each other out, and in the case of a single-phase two-wire power distribution system. Since leakage can only be detected in the non-grounded wire, the insulation resistance of the grounded wire can only be estimated by analogy, and all wires can be measured at once.
It contains a fatal flaw that is not theoretically consistent with the regular measurement made by .

In addition, the b and c methods can only calculate the value for all distribution lines connected to the secondary side of the pole transformer, and it is possible to determine whether the insulation failure is caused by the outdoor distribution line or by any customer's indoor wiring. The purpose cannot be achieved because it is not possible to identify the cause of the problem.

Therefore, as shown in Fig. 8, a sine wave voltage with a high frequency different from the commercial I, 1 wave is injected in series using a clamp-type injector 1 to the distribution lines to the target low-voltage consumers. A method has also been announced in which only the injected frequency component is extracted from the current taken out by a detection clamp type current transformer 2 that is electromagnetically coupled to the distribution line in the vicinity of the injector 1. In this case, when rewritten as the ground circuit to be measured, the equivalent circuit shown in Fig. 9 is obtained, but since the ground resistance RG is extremely small compared to the ground impedance of the power distribution line on the electric whale side, the circuit in Fig. 9 is It can be replaced with the circuit shown in Figure 10.

In addition, in FIGS. 8 to 10, RsO' Rs
l"s2 is the insulation resistance to ground of each line on the power supply side including distribution lines of other customers, CsO'Cs□"s2 is the capacitance to ground of each line on the power supply side, R6 is the grounding resistance of the neutral point, R
PO, R, R are the ground insulation of each line of the target customer's wiring! ! !
2 Resistance, C, C, , C is the ground capacitance, 柁
12 Z Z is the load impedance between each line on the power supply side, sl
' s2 2,,. 2 is the impedance between each line of the target customer.

Ma1. MA2 is the commercial frequency voltage between each line, MARO is the injection voltage.

e is the detected voltage, i, , i, i is the customer wiring 21
! This is the injection current flowing through each line of 2.

At this time, C+C+C snow C(lb) ZI Fil! ! rJ xHowever, R;
All wires collectively ground insulation resistance C; All lines collectively ground capacitance! If we consider only the injected current separately according to the principle of superposition, we can write the angular velocity of the injected voltage as ω.

(Problem to be solved by the invention) However, in order to find the insulation resistance, the injection current i! The average current (2) obtained by synchronously switching the values of equation (2) to extract the component in phase with the injected voltage Malo is, but what is the ground capacitance C2 and the ground insulation resistance R?
Since both values differ depending on the target customer, and the value of the ground resistance RG differs depending on the ground, it cannot be treated as a fixed ratio, and therefore errors cannot be avoided. Due to the increase in wiring length and the spread of wiring inside metal pipes, the ground capacitance C increases and reaches a maximum of 0.31LF! Therefore, the error due to the l# sound cannot be ignored.

Therefore, the reality is that this method, which has already been announced, has not yet been commercialized.

In view of the above points, it is an object of the present invention to provide a measuring method that can easily determine distribution line constants such as wiring bulk insulation resistance to ground for each low-voltage customer in a live line state.

(Means for Solving the Problem) The present invention uses a clamp-type injector to inject a triangular wave voltage as a test voltage into the distribution line to be measured, and detects leakage current in the distribution line with a clamp-type current transformer. , a reverse direction Tf flows through the secondary side of the clamp-type current transformer through an auxiliary line containing controlled constant elements corresponding to each constant of the distribution line, and the detected voltage of the clamp-type current transformer becomes zero. The present invention is characterized by a live-line distribution line constant measuring method using a current neutralization method in which the controlled constant element is controlled as described above and the constant of the distribution line is transferred to the controlled constant element.

(Example) Hereinafter, the method of the present invention will be explained using FIGS. 1 to 7.

FIG. 1 is a block diagram showing the principle of the present invention, and TS
are the secondary windings of the pole transformer, Wt, W2. W3 is the target customer wiring, IT is a clamp type injector for injecting the test voltage, 3 is a triangular wave voltage generation circuit that supplies a triangular wave voltage to the clamp type injector IT, and CT is for detecting ground leakage current. Clamp type current transformer, 4 is a detection circuit for extracting the secondary voltage of the clamp type current transformer CT, 5 is a current neutralizing auxiliary line for flowing reverse current to the clamp type current transformer CT, 8
is the controlled constant element 1 & element connected to the auxiliary 55, 7 is a circuit that controls the controlled constant element 6 in the direction where the secondary core pressure of the clamp type current transformer CT becomes zero, RRR is the ground insulation resistance, and C
A.

A' N' B CM and CB are ground capacitances, and R8 is a ground resistance.

In order to facilitate understanding of the present invention, the outline of FIG. 1 will first be explained.

When a test voltage is injected by connecting the injector IT to the middle of the distribution line connecting the low-voltage distribution line to the consumer as shown in the figure, the injection voltage e induced at the same value in each line of the distribution line will be The current is led to the earth through the ground capacitance and ground insulation resistance, and is circulated through the ground resistance of the second type grounding work installed at the neutral point of the secondary side of the pole transformer. At this time, the same injection voltage is induced in the auxiliary line, but this auxiliary line 5
If the current flows through the clamp type current transformer CT in the opposite direction and is connected so that it circulates through the controlled constant element 8, the effect of the current flowing back through the distribution line will be canceled, so the constant of the distribution line and the controlled constant element 8 will be canceled. If the values of control constant element 6 match, the clamp type current transformer CT
The interlinkage magnetic flux of is canceled out and becomes zero, and naturally the detected voltage also becomes zero. Therefore, if the control circuit 7 is operated so that the detected voltage is monitored and becomes zero, and the controlled constant is automatically adjusted to find the zero point of the detected voltage, the controlled constant element 6 becomes each of the target customer's wiring. It becomes the same value as the constant, and by knowing the value of the controlled constant element B, it is possible to conversely know each constant of the consumer wiring.

To explain in more detail, a triangular wave voltage e(t
52), the equivalent circuit is shown in FIG. However, r; the total wire-to-ground insulation resistance R of the target customer's low-voltage wiring; the neutral point grounding resistance C; the target customer's low-voltage wiring! All line collective ground capacitance e; Injected triangular wave voltage ma: Detection voltage of the clamp type detector.

At this time, the charges stored in q and c! If i: r is expressed as a flowing current, then q=cri (1)!
! Therefore, R(dg +i)+ridt x -CrRJ+(r +R)i w e (
2) The voltage equation xxxdt xx holds true, where e = E(F -1) (2T≧t≧0)
When expressed as (3), (2) can be rewritten as , so replace it with further and convert it into an operator expression:' = R4-F' q+ a (pT-1) (5)
x I! Solve i=Complete ■ "Here (2 (tzu) handiwork! !! α X (2ε-cxt---"" ) ) (6
a) l ε −αt (1−(1+αT)ε ) (8b) is obtained.

Therefore, the current through the detector is i+ (!J-i+ cr rlij dt
l+aT)Cr ε-(xtx, xx
xxl゛αt −αt−−2αT)) +2ct (2ε 1 ε −αT +t−(1−αT)(r−R) Ce ) (7
)xpx.

This 'I current circulates through the detector and becomes its primary current 11, which induces a detection voltage in its secondary winding. Now, regarding the detector, average length of magnetic path Average cross-sectional area of alternating magnetic path S Effective magnetic permeability Color Secondary ala N Secondary effective burden resistance R2 Secondary current 12 Total number of interlinked magnetic fluxes If expressed as φ, then φ-K(i, -Ni2)
(8) K = 4e main
(8a) is erect and also merN −” −Ri
(9) Since t22, rearranging the above, −αt (1+(EC(1÷aT)(r −R) ε
) (1G)x
! p is required. Therefore, we can solve the equation (lO) by rearranging it as r >>R#R(lla)! ! Since p, we can rewrite (11) by including this condition. However, in a repetitive waveform, mat = o ” - mat
=27 (12a) Therefore, we can determine the integral constant A by this.

Here, as shown in FIG. 4, r, R, and C, respectively!
x! Let us consider that three types of CC control constant elements, corresponding to r, R, and C, are set to cause a reverse current to flow through the detector, and a current neutralization method is applied.

When reverse current flows, the output voltage is -5,1° is given by

When starting measurement rc=lOO(15a) R-0 (15b) C=O(15C) Depart from. This is the state of equation (13).

For the first term of equation (13), at the deflection time of the injection triangular wave voltage e. A time τ when a certain period of time Tc has elapsed since then.

Integrating up to
1B) The condition for Cα to be zero is .

To explain again, the detected voltage given by equation (13) is a voltage with a waveform as shown in the upper part of Fig. 5,
This is the insulation resistance r expressed by a single curve as shown in the lower part of Figure 5.
A component that is inversely proportional to , and a C curve type
It consists of a damping constant α component represented by α and a damping constant β component represented by the Cβ curve, among which the component that is inversely proportional to r is the shaded part in Figure 5! At the rise time of the curve as shown in . It can be seen from equation (lea) that if we integrate and average until a certain time T has elapsed from then, the positive and negative strokes CC cancel each other out and become zero. Therefore, if the integrated voltage is obtained by switching the detection voltage m for a certain period of time T that satisfies the following, the integrated voltage will not include any component related to the insulation resistance r, and! An integrated voltage exclusively related to capacitance C is obtained.

Therefore, when the presence of this integrated voltage is detected (15c)
The operation of C is canceled by controlling C in the direction of increasing from the state of the equation, and that operation is the 6th! This is done by a circuit like the block diagram shown in the figure.
The explanation is as follows.

The detection voltage given to the switching circuit 8 is:

Here, switching is performed with the time width T as described above, and the capacitance C- is further averaged by the integrating circuit 3.
The DC voltage is proportional to C. The voltage x supply At this time, when the value deviates to the positive side, the up/down counting circuit performs an addition counting operation, and conversely, when the value deviates to the negative side, it performs a subtraction operation.The output of the counting circuit is sequentially given to the discrimination storage element 13, and the signal It operates to add or subtract after determining the state of the switching mechanism of the given channel, memorize the state, and cause the switching mechanism 14 to input and hold the signal.

The controlled constant element 8 is constituted by a capacitance having a value proportional to 29 to 2 degrees, and the element of the channel held by the switching mechanism 14 is selectively connected to the external terminal C9.

As a result, the operation of C is canceled out by the compensation operation of C, and the operation stops when the integrated voltage falls within the range of the rain level voltage mentioned above. At this time, naturally C'v C, (17) is obtained.

Therefore, equation (14) is -CC2ε-l--213T)(r-6)!
It can be rewritten as ε. At this time, according to equation (+5b), the second term in the third term of this equation should be zero, but there is a small amount of resistance and induction in the circuit that flows the reverse current (compensation current for neutralization). There is a reactance, and therefore, although the value is small, a component that changes extremely quickly due to this term appears as a negative voltage at the rising edge of the waveform. Therefore,
By extracting and comparing the voltages immediately before and after the deflection point of the applied triangular wave voltage, it is possible to determine the presence or absence of the aforementioned high-speed pulse component. That is, as shown in FIG. 7, the instantaneous detected voltage values are sampled and held using the sampling command pulse φl immediately before the deflection point of the triangular wave voltage and the sampling command φ2 immediately after, and by comparing the values, the high-speed pulse component can be determined. can be detected, so compensate the grounding resistance R using the controlled constant element R8 using the same circuit and method as the static capacitance compensation described above! I can do it.

When the compensation is completed in this way, R~Ro(19)! Therefore, when considered in conjunction with equation (17), (14)
The components proportional to C and C in the equation, i.e. the second term and the third !
The C term disappears, and only the component inversely proportional to r remains! There is.

Therefore, as shown in Fig. 7, if another sample and hold circuit is made to hold the instantaneous value of the detected voltage by a sampling command φ3 just before the end of the radius of the triangular wave voltage, the value will be the first term of equation (14). This is because t is obtained by adding t −27 (20) to . Once this value is detected, the insulation resistance can be compensated for in exactly the same manner as for capacitance and ground resistance, and the compensation operation is completed when r ``tro(21)!'' is reached.

As a result, the detected voltage of the detector becomes almost zero when the compensation operation is completed, and the ground insulation resistance, ground capacitance, and ground resistance of the distribution line neutral point of the target customer are reduced to 3.
The insulation resistance to ground can be found by separately measuring the value of the controlled constant element.

(Effects) As detailed above, the present invention injects a sinusoidal voltage into the distribution line as in the method shown in Figure 8, and extracts only the injected frequency component of the current taken out by the clamp type current transformer. The difference is that a triangular wave voltage is injected and the leakage current in the distribution line is taken out by a clamp type current transformer, and the clamp type current transformer is extracted by an auxiliary line containing controlled constant elements corresponding to each constant of the distribution line. By flowing a reverse current to the secondary side and controlling the controlled constant element so that the detected voltage of the clamp type current transformer becomes zero, the constant of the distribution line is transferred to the controlled constant element. , the constant of the distribution line to be determined.

For example, insulation resistance can be easily and accurately measured.

Furthermore, since this method neutralizes the current passing through the detector and detects its zero point, the effects of the reproducibility characteristics of the magnetic circuit due to repeated use of the detector and the nonlinearity associated with the magnetic circuit etc. Since it is not subjected to any interference, accuracy is not compromised even at high amplification for detecting extremely small amounts.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the principle of the live-line distribution line constant measurement method according to the present invention, Fig. 2 is a waveform diagram of the triangular wave voltage injected into the distribution line, and Fig. 3 is a waveform diagram of the triangular wave voltage injection. Equivalent circuit, Fig. 4 is the equivalent circuit of Fig. 1, Fig. 5 is a detection voltage waveform of a clamp type current transformer and its decomposed waveform diagram, and Fig. 6 is a block diagram for explaining an example of control of controlled constant elements. figure,
FIG. 7 is a diagram of detected voltage waveforms and signal waveforms for sampling commands. FIG. 8 is a conceptual diagram of a conventionally proposed live wire-to-ground insulation resistance measurement method, FIG. 9 is an equivalent circuit of FIG. 8, and FIG. 10 is an equivalent circuit that is further simplified from FIG. 9. IT...Clamp type injector CT...Clamp type current transformer C...Distribution line constant x, x r, C...Controlled constant element CC 5...Auxiliary line patent applicant Kansai Electric Power Company Toko Seiki Co., Ltd. Representative Patent Attorney Takashi Suzue - Figure 1 Pillar I Transformer Outside Figure 2 Figure 3 Figure 4 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] (1) Inject a triangular wave voltage as a test voltage into the distribution line to be measured using a clamp-type injector, detect the leakage current of the distribution line with a clamp-type current transformer, and A reverse current is caused to flow through the secondary side of the clamp type current transformer through an auxiliary line including a control constant element, and the controlled constant element is controlled so that the detected voltage of the clamp type current transformer becomes zero, A live-wire distribution line constant measurement method using the current neutralization method, which transfers the constant of the distribution line to a controlled constant element.