JPS60168057A - Ground resistance measuring device of dc line - Google Patents

Abstract

PURPOSE:To measure by direct reading the ground resistance of a DC circuit with simple circuit constitution, by connecting positive pole and negative pole side lines by a switch and a variable resistance, forming a bridge together with the ground resistance, and measuring the ground resistance. CONSTITUTION:Between a positive pole side DC line l1 and a negative pole side DC line l2, a switch SW1 of a ground resistance measuring device 1, a variable resistance VR by which the respective resistances of the lines l1, l2 attain R1 and R2, and a switch SW2 are connected. When these switches SW1, SW2 are turned on, and a bridge circuit formed by the switches SW1, SW2, the resistances R1, R2, and the each ground resistances RP, RN of the line l1, l2 is balanced through the resistance VR, the resistances R1, R2, RP and RN satisfy the condition of an expression. When only the switch SW2 is turned on in this balanced state, a current IP flowing to an ammeter M becomes IP=E/(R1+R2+ RP) based on the condition of the expression, and attains to a value corresponding to the resistance RP. With respect to a resistance R0, too, it is measured in the same way, and the ground resistance of a DC circuit can be measured by direct reading with simple circuit constitution.

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a DC line grounding resistance measuring device for measuring the grounding resistance of an ungrounded DC line. (Technology) Conventionally, this type of measuring device includes earth leak detectors and earth resistance needles that require J and J conversion. It is impossible to know.Also, a ground resistance meter that requires conversion is one in which the resistance value cannot be read with a meter, and it is necessary to convert the meter reading based on the degree of adjustment when each adjustment is made. As described above, this type of conventional measuring device has various drawbacks. [Summary of the Invention] This invention eliminates the above-mentioned drawbacks of the conventional measuring device and makes it possible to directly read the ground resistance of a DC circuit with a simple circuit. [Embodiment of the Invention] Figures 1 and 2 are diagrams for explaining the basic operation of the earthing resistance measuring device for a DC line according to the present invention. First of all
In the figure, +Ill and e2 indicate the lines of the DC circuit, and e
l is the positive line, and e2 is the negative line. E is the voltage applied to each line e, g=+ of the DC circuit, RP
is the grounding resistance on the positive side of 6, RN is the grounding resistance on the negative side, (υ
is a grounding resistance measuring device, which includes an ammeter M whose one end is grounded,
The variable resistor VR connected to the variable terminal of the ammeter M, the variable resistor VR and the positive and negative side lines e1. It consists of switches SW, , sw2 connected between e2. Note that the dividing resistors R, , R, are dividing resistances of the variable resistor VR divided by the variable terminals of the variable resistor VR. Next, the operation of the apparatus shown in FIG. 1 will be explained. First, switch SW
Turn on I and SWa. At this time, grounding resistance Rp and R
A bridge circuit is formed by dividing resistors R1 and R2 of N and variable resistor VR, and the balance of this bridge circuit is adjusted by variable resistor VR. This is adjusted with the variable resistor VR so that the indication of the current needle M becomes zero.At this time, the following [1]
The formula holds true. Rp-Rt-RH-Rt... [1] Next, to describe the method for measuring the positive ground resistance RP, leave the set position of the balanced variable resistor VR as is as described above, and press the switch. Turn off SW+, turn on switch SWi
N, and if the current flowing through the ammeter M at this time is IP, (however, the internal resistance of the ammeter M is assumed to be zero) R2 (RN+RP) +RN-RP (2) Formula i, (Rt + R2) C variable resistance VR (D is the maximum terminal resistance, always constant, and its value is known. E is the circuit voltage and its value is known. Therefore, [2] Equation 1 is the current IP flowing through the ammeter M.
and. Since the relationship between the positive electrode side grounding resistance RP is perfect, if the ammeter M is calibrated accordingly, the grounding resistance RPe can be directly read. Next, a method for measuring the negative ground resistance RN will be described. Turn on switch SW+ while maintaining the above-mentioned equilibrium state. Switch SW2 is turned OFF. At this time, let IN be the current flowing through the ammeter M. R1 (RP +RN) +RN-Rp R+ + R2+ RN Equation [8] has the same form as Equation [2], just replacing RP in Equation (2) with RN.Therefore, like Equation [2], the ammeter The relationship between Ml, the current IN, and the negative grounding resistance RN is perfect, so if you mark the ammeter M1ζ scale accordingly, you can directly read the grounding resistance RN. Here, the currents IP and IN flow in opposite directions. Is the ammeter M a bidirectional meter?
This can be solved by adding a travel circuit and making the instrument input direction the same. 1ζ, h In the explanation of Figure 1 mentioned above, the resistance value of the flowmeter M was described as zero, but in reality it has a resistance value of 1, 1, and 0, and now its resistance value is When Rm,
(For each calculation formula in Figure 1). Bridge balance equation 11] is the same force S, equation [2) and equation [8] equation 1ζ are different. That is, vI
The current flowing through the L current meter M1 is IP and I% as shown in the linear equation. (Substitute)) These changes change when the set point of the variable resistor VR changes, and Equations (4) and [,53 are the ground resistances RP and R.
Show that N influences each other. An embodiment that eliminates this inconvenience is shown in FIG. In Fig. 2 ζ, (21 is the earth resistance measuring device +
Rm (8 locations) is any fixed resistance. This value also includes the internal resistance value of the ammeter M. SW3 and SW4 are switches. The operation shown in FIG. 2 will be explained below. First, switch 5
WI, SW2 turned on, switch sw3. sw, OFF
shall be. At this time, grounding resistances RP and RN, f3 and resistance R
m and the sum of 10,000 setting resistance R of variable resistor VR (Rm+
R1), the resistor Rm, and the other setting resistor R of the variable resistor VR
A bridge circuit is formed by the sum of 2 (Rm+R2), and the balance of this bridge circuit is adjusted by a variable resistor VR. At this time, the following formula [6] holds true. Rp ・(R2+Rm) =RN ・(R1+Rm)
−= (6) Method of measuring the positive electrode side grounding resistance RP lζ
I will talk about this. The switch SW4 is turned ON and the switches SW+ to SW3 are turned OFF while leaving the set position of the variable resistor VR that maintains the above-mentioned balance as it is. At this time, the current IF flowing through the ammeter M is expressed by the following equation. Substitution) In formula (7), + (R+ +R4) is the variable resistor V
The maximum terminal-to-terminal resistance of R is a constant and known resistance value, and Rm is also a constant and known resistance. Therefore, from equation [7], the relationship between the current IF flowing through the current at M and the positive ground resistance RP can be found, and by marking the scale on the ammeter M according to this, the ground resistance RP can be directly read. Next, a method for measuring the negative ground resistance RN will be described. While maintaining the above-mentioned balanced state, switch SW3 is turned on, switches SWI and SW2 are turned on, and SW4 is turned to 0FFff. At this time, the current IN flowing through the torrent hole M is expressed by the following equation. R+ +R2" 2 Rm 10RN) Formula [8] is written in E. Similar to formula [7], the relationship between the current IN flowing through the ammeter M and the negative electrode side grounding resistance RN is found, and the current fFrM is scaled accordingly. You can directly read the ground resistance RN by writing in.As described above, the circuit shown in Figure 2 is an ammeter M.
It is not affected by the sac due to internal resistance. Figures 8 and 4 are diagrams showing an embodiment of the DC line grounding resistance measuring device according to the present invention 1, and the same parts in Figure 1 as in Figures 1 and 2 are designated by the same reference numerals. There is. First, the operation of FIG. 8 will be explained. The circuit shown in Figure 8 is the circuit shown in Figure 2 with the addition of a subtracter al) and a divider (2), and the ammeter M is divided! (2) is connected to the output. Subtractor (11 is line e to ground, and e
It outputs a DC voltage proportional to the difference between the two voltages by 1.
The output is obviously a DC voltage proportional to the circuit voltage E with respect to ground. The divider Oa performs the calculation Y-Z/X, and drives the ammeter M with its output. Embodiment 1 of FIG. 8 is constructed as described above. First, turn on switches SWI and SW2, then switch SW
3. Turn off SW4 and move the selector switch SWs to the terminal side. At this time, as in FIG. 2, the sum (
Rm+R4), the sum of the resistor Rm and the other setting resistor R2 of the variable resistor VR (Rm+Ra)), a bridge circuit is formed, and the unbalanced voltage of the bridge is connected to the resistor Rm inserted between the ground and the changeover switch SWs. The ammeter M (ζ is supplied through the ammeter M. Therefore, if the variable resistor VR is adjusted so that the indication of the ammeter M becomes zero, then R
6] The same equilibrium equation as the equation holds true. Next, a method for measuring the positive electrode side grounding resistance RP will be described. Leave the above-mentioned balanced setting position of the variable resistor VR as it is, turn on switch SW4, switch sw, ~s
Turn off w3 and turn the selector switch S W s one turn on the terminal a side. At this time, one resistor R is inserted between the ground
The current IP flowing through mlζ is the same as the equation [7] above. The voltage drop EP across the resistor Rm inserted between the ground due to the current IF is expressed as the quadratic

[9] Equation becomes as follows. Next, to measure the 1ζ negative side grounding resistance RN, turn on the switch SW3 in the above-mentioned balanced state, switch SW, , 5W
Turn off 2H and SW4, vJ change switch SWs
Terminal a side]. At this time, the current IN flowing through the resistor Rm inserted between the ground is the same as the formula (8) in n. Noshi 10] The voltages EP and EN shown in the above (9:) and [101 equations are the output voltage E of the subtracter Oυ in the divider (2).
are expressed as the following equations (11) and [12], respectively.Equation 1 (11ml, (12)) shows that the output EP (and EN) of the divider (2) is the positive polarity. Side grounding resistance RP (and negative side grounding resistance R,) and known resistance (R) + R
2) *It is expressed as a function of Rm, and there is no term for circuit voltage E, so errors due to fluctuations in one circuit voltage E do not occur. Therefore, by driving the ammeter M with the output of the divider (b) and marking the scale on the ammeter M according to equations (10 and (12)), the ground resistances Rp and RN can be directly read. 11) As shown in equations [12], the output voltages Ep and EN on the divider side are linearly proportional to the grounding resistances Rp#, J: and RN, respectively, so the range of application is as a signal to the data logger 2 calculator, etc. Next, Fig. 4 shows another embodiment, which can be used as a modification of the circuit shown in Fig. 1 if the ground-to-ground insertion resistance R in Fig. 1 is made sufficiently small.The measurement formula is is 1-4 above.
) is isomorphic to the formula [,5], and has already been briefly explained, so it will not be explained here. [Effects of the Invention] As described above, according to the present invention, the ground resistance of a DC line can be directly read using a simple circuit.

[Brief explanation of the drawing]

FIGS. 1 and 2 respectively relate to the present invention (the second figure explains the basic operation of the earthing resistance measuring device for a flow line, and FIGS. 8 and 4 each illustrate an embodiment of the present invention). This is a circuit diagram showing the circuit diagram. In the figure, VR is a variable resistor, 1M is an ammeter, and RP + R
N is a grounding resistance, SW+ to SW4 are switches, SWs is a changeover switch, 0υ is a subtracter, and (2) is a divider. In addition. The same reference numerals in each figure indicate the same or corresponding parts. Agent: Patent Attorney Masuo Oiwa Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] Measured item] A hair resistor connected between the positive pole side and the negative pole side of the C flow path, a resistor connected between the variable terminal of the variable resistor and the ground, the variable resistor and the positive pole side, The first one inserted between the negative electrode side. a second switch, a subtracter that outputs a DC voltage proportional to the difference of 1 between the voltage between the positive electrode and the ground and the voltage between the negative electrode and the ground, and divides the output of the subtracter by the voltage generated across the resistor; a divider driven by the output of the divider; and a divider driven by the output of the divider; and a divider driven by the output of the divider;
comprising a changeover switch connecting the meter to the divider,
Said 1st. A grounding resistance measuring device for a DC line, characterized in that by turning on and off a second switch, each of the grounding resistances on the positive electrode side and the negative electrode side is set to f so that the grounding resistances on the positive electrode side and the negative electrode side can be directly read according to instructions from an n-meter meter.