JPH09243686A - Method for measuring ground impedance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate measurement of ground impedance by obtaining impedance associated with ground such as impedance of a ground-concerned part, ground impedance, and impedance between devices as a matrix. SOLUTION: An admittance matrix from respective admittance when only voltage Va is applied from a voltage source Sa and only voltage Vb is applied from a voltage source Vb , and this is converted into an impedance matrix [Z]. [Z] indicates entire impedance viewed from a ground integration part C. With only the voltage Va or voltage Vb applied, ground impedance Rc is obtained from voltage Vo to an auxiliary electrode Paux and current Ic flowing in the ground integration part C. If respective impedance matrixes for a circuit network Z1 including devices A, B having the integration ground part C as a common return and a circuit network Z2 including only the ground impedance Rc are [Z1], [Z2] respectively, [Z1] can be obtained as a matrix with Rc subtracted from respective components of [Z1].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grounding system comprising N (≧ 2) devices which are individually grounded, and a grounding integrated part which grounds the N devices in common. The present invention relates to a method for providing and measuring ground impedance.

[0002]

2. Description of the Related Art Conventionally, a so-called three-terminal method using a current application auxiliary electrode and a voltage measurement auxiliary electrode has been used for measuring ground impedance. FIG. 7 is a diagram for explaining this conventional technique, where P is a ground electrode to be measured whose ground impedance is to be measured, Pi is an auxiliary electrode for applying current,
Pv is an auxiliary electrode for voltage measurement, S is an alternating voltage source for measurement,
I is a current measuring device and V is a voltage measuring device. Further, Rp is the ground impedance of the measured ground electrode P, Rv is the ground impedance of the voltage measurement auxiliary electrode Pv, and Ri is the ground impedance of the current application auxiliary electrode Pi.

In measuring the ground impedance Rp, a voltage source S for measurement is connected between the ground electrode P to be measured and an auxiliary electrode Pi for current application to pass a current i, and the voltage Vp of the ground electrode P to be measured is set. , The voltage measuring auxiliary electrode Pv is used as a reference to measure with a voltage measuring device V. That is, the voltage Vp between the electrode P and the electrode Pv is measured by the voltage measuring device V. At this time, since the internal resistance of the voltage measuring device V is large, no current flows through the electrode Pv, and therefore the ground impedance R of the electrode Pv is reduced.
There is no voltage drop due to v, and the measured voltage Vp
Is a voltage drop due to the ground impedance Rp. Therefore, the ground impedance Rp is obtained by Rp = Vp / i.

FIG. 6 shows a system having a plurality of grounds, where A and B are grounding impedances R individually.
A device grounded by the ground electrodes of a and Rb, and C is a ground integration unit that grounds the devices A and B in common by the ground electrodes of the ground impedance Rc. Here, the ground impedance Rc of the ground integration unit C is set to a predetermined value by grounding along a predetermined reference, but the ground impedances Ra and Rb of the individual ground electrodes of the devices A and B may be unknown. is there.

[0005]

However, in the conventional ground impedance measuring method, the ground impedance R
In order to know a and Rb, it is necessary to measure the ground separately, and it has not been possible to measure the ground impedance of the ground system including the ground impedances Ra and Rb and the mutual impedance Rab between the devices A and B. .

An object of the present invention is to provide a grounding system comprising N individually grounded devices and a grounding integration part for common grounding of the plurality of devices, and to matrix the grounding impedances other than the grounding integration part. It is intended to provide a method for measuring the ground impedance, which enables the measurement of the ground impedance without disconnecting each ground at that time.

[0007]

A first aspect of the present invention is a grounding system comprising N (≧ 2) devices that are individually grounded and a grounding integration unit that commonly grounds the N devices. , An auxiliary ground is provided, a voltage is applied to one of the N grounds to measure an electric current flowing through each of the N grounds to obtain an admittance, and this admittance measurement is performed for each of the N grounds. Applying a voltage to each of the remaining grounds to obtain an admittance matrix from which a total impedance matrix including the N grounds, the ground integration ground, and the plurality of devices is obtained. A voltage is applied to any one of the N grounds, and the connection is made from the current flowing to the ground of the ground integration unit and the voltage of the ground integration unit measured with the auxiliary electrode as a reference. To obtain a ground impedance of the integration unit, or by applying a voltage to ground of the ground integration unit,
Obtaining a ground impedance of the ground integrating unit from a current flowing to the ground of the ground integrating unit and a voltage obtained by subtracting the applied voltage from a voltage of the ground integrating unit measured with the auxiliary electrode as a reference; and the impedance matrix The ground impedance is subtracted from the ground impedance to obtain an impedance matrix excluding the ground impedance of the ground integration part of the ground system, and the ground impedance measuring method is configured.

According to a second aspect of the present invention, the grounding impedance measuring method according to the first aspect is characterized in that the voltage application and / or the current measurement is performed by a current transformer.

According to a third aspect of the present invention, in the second aspect of the present invention, the current transformer is a current transformer which is attachable to and detachable from a ground line.

According to a fourth aspect of the present invention, in the second and third aspects, the current transformer for applying the voltage is provided with a correction winding for monitoring the applied voltage. did.

In a fifth aspect based on the first to fourth aspects, the measurement of the ground impedance of the ground integration section is performed by applying a voltage to the ground of the ground integration section, and the one of the N grounds. At least two or more measurements performed by applying a voltage as described above were performed, and an average value of the measurement results was used to constitute a ground impedance measuring method.

According to a sixth aspect of the present invention, in the second to fourth aspects, when the ground impedance of the ground integration section is measured by applying a voltage to the ground of the ground integration section via the current transformer. In addition, the grounding wire between the voltage measuring means for measuring the voltage with the auxiliary electrode as a reference and the grounding integrated portion is penetrated through the current transformer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a diagram for explaining a ground impedance measuring method according to a first embodiment of the present invention. The same components as those in FIGS. Reference numerals are given and detailed description thereof is omitted. Sa is device A
Between the device B and the ground integration unit C, a measurement voltage source that applies the voltage Va between the device B and the ground integration unit C, and Sc represents the ground integration unit C and the same. It is a voltage source for measurement that applies a voltage Vc to the ground. Paux
Is an auxiliary electrode provided for measuring the voltage of the ground integration portion C, and Raux is the ground impedance of the auxiliary electrode Paux.

The ground in-piece dance is measured as follows. First, only the voltage Va from the voltage source Sa is applied (the voltage Vb and Vc are not applied and the part is short-circuited). At this time, the current measuring instrument I causes the current Ia flowing through the device A and the device B to flow. The electric current Ib flowing through is obtained, and the admittances yaa and yab are obtained from yaa = Ia / Va and yab = Ib / Va.

Next, only the voltage Vb from the measuring voltage source Sb is applied (the voltage Va Vc is not applied and the portion is short-circuited), and at this time, the current is measured by the device A to flow through the device A. The current Ia and the current Ib flowing through the device B are obtained, and the admittances yba and ybb are obtained from yba = Ia / Vb and ybb = Ib / Vb.

When these are expressed in the form of an admittance matrix of a four-terminal network in which the device A side and the device B side are viewed from the ground integration unit C, the following equation (1) is obtained.

[Equation 1] Therefore, this is a known method, for example,

[Equation 2] The impedance matrix [Z] is converted using the following formula. The impedance matrix [Z] of this four-terminal network represents the overall impedance as viewed from the ground integration section C.

Next, the voltage Va is supplied from the voltage source Sa or Sb.
Alternatively, when Vb is applied (the voltage Vc is not applied and the portion is short-circuited), the ground integration portion C for the auxiliary electrode Paux is provided.
Voltage Vo and the current Ic flowing through the ground of the ground integration unit C
Is measured. The voltage Vo is a voltage generated in the ground impedance Rc due to the flow of the current Ic.
Therefore, the value of the ground impedance Rc is obtained as follows. Rc = Vo / Ic ... (3)

Alternatively, when the voltage Vc is applied from the voltage source Sc (the voltages Va and Vb are not applied and the portions are short-circuited), the voltage V of the ground integration portion C with respect to the auxiliary electrode Paux.
o is measured, and the current Ic flowing through the ground integration portion C is measured. At this time, since the generated voltage Vo includes the voltage Vc of the voltage source Sc in addition to the voltage drop due to the ground impedance Rc, the voltage Vc is subtracted to obtain an accurate voltage generated in the ground impedance Rc. Therefore, at this time, the value of the ground impedance Rc is obtained as follows. Rc = (Vo-Vc) / Ic ... (4)

Next, by modifying FIG. 1 and expressing the ground impedance Rc as an ideal ground (ground resistance 0Ω) and an impedance Rc inserted in series with it, it becomes as shown in FIG. Further, the circuit network Z of the circuit of FIG. 2 is cascade-connected to the first circuit network Z1 including the devices A and B having the common integration line C as the common return line and the second circuit network Z2 having only the ground impedance Rc. When expressed as, it becomes as shown in FIG.

Assuming that the impedance matrix of the first network Z1 is [Z1] and the impedance matrix of the second network Z2 is [Z2], the impedance matrix of the entire network Z of FIG. ], The impedance matrix [Z1] is given by [Z1] = [Z] − [Z2] ... (5) from a known formula. Here, the impedance of the second network Z2 is the ground impedance Rc. Therefore,
The impedance matrix [Z1] is the ground impedance Rc from each element of the impedance matrix [Z].
Is represented by the subtraction of.

The impedance matrix [Z1] of the network Z1 thus obtained is the impedance of the ground-related parts of the devices A and B, the ground impedances Ra and Rb with the ground integration part C as a common return line, and the mutual impedance. It is an impedance matrix showing the impedance related to the entire grounding of the grounding system including Rab and the like by a two-terminal network.

From the above, according to the present measuring method, the ground impedance of the entire system with the ground integration section C as a reference (common return line) can be measured in the form of an impedance matrix. In addition, as is clear from the above description,
The impedance Rc of the ground integration part C with respect to the ground can be obtained by the equation (3) or (4).

In the above description, the grounding system has two devices as shown by A and B, that is, N = 2. However, even if N = 3 or more, the grounding system of the grounding system also has the same configuration. It is possible to measure the overall impedance matrix. When N = 3, a 6-terminal network is used, N = 4
In the case of, it is represented as an 8-terminal network.

[Second Embodiment] Regarding the measurement of the ground impedance Rc described above, a plurality of sites to which the voltage of the measurement voltage source is applied can be used (in the first embodiment, 3).
Therefore, in actual measurement, voltage is individually applied to multiple individual application sites to perform multiple measurements, and the average value of the obtained values is calculated and used to improve the measurement accuracy. Can be made. It is also possible to apply the voltage of the measurement voltage source to each of the plurality of application sites at the same time and use the measurement at that time as the average value.

[Third Embodiment] FIG. 4 shows a third embodiment of the present invention.
It is a figure for explaining an embodiment. Here, the voltage from the measurement voltage source S is applied by using a current transformer. In FIG. 4, CT is a current transformer having a winding number of m, and Le is a ground wire to which a measurement voltage is applied. As shown in FIG. 4A, a current transformer of m: 1 can be constructed by coupling a current transformer CT to the ground line Le, and the voltage of the measurement voltage source S of 1 / M times the voltage to ground wire Le
Can be applied to. Further, as shown in FIG. 4B, by winding the ground wire Le n times, an m: n current transformer can be configured, and a voltage n / m times the voltage of the measurement voltage source S can be applied to the ground wire Le. Can be applied to. In the above, by making the current transformer CT into a clamp type that can be attached to and detached from the ground wire Le,
It is possible to apply a desired voltage without disconnecting the ground line Le while maintaining the current state.

The applied voltage is, as shown in FIG.
By adding a monitor circuit composed of the correction winding Lc and the terminating resistor Rm, the same voltage as the voltage applied to the ground line Le is generated at both ends of the terminating resistor Rm so that the voltage measuring device V can monitor the voltage. It is possible to correct the error in the coupling amount of the sink. The value of the terminating resistor Rm is optimally a value close to the impedance of the portion to which the voltage is applied, but it can be deleted.

Although a current transformer is used here to apply a voltage, this current transformer can also be used in current measurement by similarly coupling it to the ground line. Of course. From the above, it is possible to apply a measurement voltage to the ground wire without disconnecting the ground wire or measure the current flowing through the ground wire, and to measure the ground impedance without changing the current status of the ground system. become able to.

[Fourth Embodiment] FIG. 5 shows a fifth embodiment of the present invention.
It is a figure showing an embodiment. As described in the first embodiment, when the voltage Vc is applied to the ground impedance Rc from the measurement voltage source Sc and the value of the ground impedance Rc is measured, the measured voltage Vo for the ground integration unit C is changed. A calculation for reducing the voltage Vc of the measuring voltage source is required.

Here, in order to make the calculation unnecessary,
As shown in FIG. 5, in addition to the ground line Le connected to the ground impedance Rc, the ground line La is arranged from the ground integration section C so as to penetrate the current transformer CT that applies a voltage,
A voltage measuring device V is connected between the penetrating ground line La and the auxiliary electrode Paux to measure the voltage Vo generated in the ground impedance Rc.

As a result, the voltage Vc of the measuring voltage source Sc applied to the ground line La penetrating the current transformer CT and the voltage Vc of the measuring voltage source Sc applied to the ground line Le cancel each other. Using the measured voltage Vo of the voltage measuring device V as it is, the ground impedance Rc can be obtained only by the calculation shown in the equation (3). That is, equation (4)
There is no need for the calculation like in.

[0031]

As described above, according to the present invention, in a grounding system comprising N (≧ 2) individually grounded devices and a grounding integrated section for commonly grounding the plurality of devices,
It is possible to obtain the impedance related to grounding such as the impedance of the ground-related part of the N devices, the ground impedance of the N devices, the impedance between the N devices, and the like, so that the ground impedance of the grounding system can be grasped. Will be easier.

In particular, by applying a voltage to the ground wire or measuring the current of the ground wire by using a detachable current transformer, the ground impedance can be measured without changing the present condition, that is, the ground. Can be achieved without disconnecting.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a ground system for explaining a measuring method according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a grounding system in which a part of the circuit of the grounding system shown in FIG. 1 is modified.

FIG. 3 is a circuit diagram for explaining the grounding system shown in FIG. 2 as a circuit network.

FIG. 4 is a diagram showing a third embodiment of the present invention and is a diagram showing a case where a voltage is applied by a measurement power source using a current transformer.

FIG. 5 is a diagram showing a fourth embodiment of the present invention, and is an explanatory diagram in the case where the voltage of the measurement power supply can be canceled.

FIG. 6 is a circuit diagram of a conventional grounding system.

FIG. 7 is a circuit diagram for explaining a conventional ground impedance measuring method.

[Explanation of symbols]

A, B: Device, C: Ground integration unit, Ra, Rb, Rc, R
v, Raux: ground impedance, Rab: mutual impedance, Pi: current application auxiliary electrode, Pv: voltage measurement auxiliary electrode, Paux: auxiliary electrode, P: ground electrode to be measured,
S, Sa, Sb, Sc: voltage source for measurement, I: current measuring device, V: voltage measuring device, CT: current transformer, Le, La: ground wire, Lc: correction winding.

Claims (6)

[Claims] 1. N (≧ 2) individually grounded devices,
In a grounding system comprising a grounding integration unit for commonly grounding the N devices, an auxiliary ground is provided, and a voltage is applied to one of the N grounds to flow to the N grounds. Each of the currents is measured to obtain an admittance, and the admittance measurement is performed by applying a voltage to each of the remaining grounds of the N grounds to obtain an admittance matrix. From the admittance matrix, the N
To obtain a total impedance matrix including a plurality of grounds, the ground integration unit ground, and the plurality of devices, and applying a voltage to any one of the N grounds to connect the ground integration unit grounds. Obtaining the grounding impedance of the grounding integration unit from the flowing current and the voltage of the grounding integration unit measured with the auxiliary electrode as a reference, or by applying a voltage to the ground of the ground integration unit, Obtaining the ground impedance of the ground integration unit from the current flowing to the ground and the voltage obtained by subtracting the applied voltage from the voltage of the ground integration unit measured with the auxiliary electrode as a reference, the ground impedance from the impedance matrix Subtracting to obtain an impedance matrix excluding the ground impedance of the ground integration part of the ground system, Ground impedance measurement method and butterflies. 2. The ground impedance measuring method according to claim 1, wherein the voltage application and / or the current measurement is performed by a current transformer. 3. The ground impedance measuring method according to claim 2, wherein the current transformer is a current transformer that can be attached to and detached from a ground wire. 4. The current transformer for applying the voltage comprises a correction winding for monitoring the applied voltage.
Alternatively, the ground impedance measuring method described in 3 above. 5. At least two of the measurement of the ground impedance of the ground integration unit, that is, the measurement performed by applying a voltage to the ground of the ground integration unit and the measurement performed by applying a voltage to one or more of the N grounds. The ground impedance measuring method according to any one of claims 1 to 4, wherein the above is performed and an average value of the measurement results is used. 6. A voltage for measuring a voltage with reference to the auxiliary electrode when the ground impedance of the ground integration unit is measured by applying a voltage to the ground of the ground integration unit via the current transformer. The grounding impedance measuring method according to claim 2, wherein a grounding wire between the measuring means and the grounding integrated portion is penetrated through the current transformer.