JPH0328775A - Inspecting device for insulation resistance measurement of cable - Google Patents

Abstract

PURPOSE:To decide a contact condition of a cable to be measured and an insulation resistance measuring instrument by integrating a charged current of the cable to be measured to detect the amount of electric charge and supplying this detected signal to a decision circuit. CONSTITUTION:When a contact 2a of switch gear device 2 is firmly in contact with a terminal 3a of the cable 3 to be measured and other contacts are in good condition, the cable 3 is also charged with a DC high voltage supplied from the insulation resistance measuring instrument 1. When the charge current (i) is made to flow to an input terminal 15a of inspecting device 10 at the time of resistance measurement, a reset switch 26 is made to open by the detected signal of an operational amplifier 25 to flow the current (i) to a capacitor 13, and a calculation is made by an operational amplifier 12 to output an electric charge detecting signal S. When the amount of electric charge is large, voltage of the signal S is decreased lower than a set voltage of power supply 19 and a positive decision signal Sj is outputted, then a light is emitted from an LED 22 through an RS-FF circuit 21, thereby the connection of the cable 3 and measuring instrument 1 is decided as normal. If the connection is abnormal, the signal S is increased larger than the set voltage and the negative signal Sj is outputted 18, therefore the light emission 22 is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for inspecting a connection state between a cable to be measured and an insulation resistance measuring device for measuring its insulation resistance.

(Prior Art) Motor load circuits and the like are connected to a power distribution board installed in a power plant or the like via a plurality of cables. The insulation resistance of these cables is regularly measured and their maintenance performed. Inspections are being carried out.

FIG. 3 is a diagram schematically showing a cable insulation resistance measurement method. In FIG. 3, reference numeral 1 indicates an insulation resistance measuring device, and this insulation resistance measuring device 1 is connected to a cable to be measured 3 via a switchgear device 2 incorporated in a distribution board (not shown). A motor load circuit 4 is connected to the cable 3 to be measured. The switchgear device 2 has a brush-like contactor 2a, which contacts a terminal 3a of the cable to be measured 3 and is electrically connected to the cable to be measured 3. The switchgear device 2 also has a measuring terminal 2d to which a contact 2a is connected via a wire 2b and a ring switch 2c, and a connecting terminal 1a of an insulation resistance measuring device l is connected to this measuring terminal 2d. There is.

Normally, the terminal 3a of the cable 3 to be measured is connected to a power distribution board (not shown) to supply power to the motor load circuit 4. When the power distribution board is operated, the terminal 3a is disconnected from the power distribution board, and at the same time, the terminal 3a is automatically connected to the power distribution board. The contactor 2a of the switchgear device 2 comes into contact.

In the connected state shown in FIG. 3, the insulation resistance measuring device 1 applies a DC high voltage of about 500 to IOOOV to the cable to be measured 3 via the switchgear device N2.

Then, the insulation resistance of the cable 3 to be measured is measured based on the galvanometric value of the current flowing through the standard resistor constituting the measuring device (2).

(Problem to be Solved by the Invention) By the way, when using the switchgear device 2, there is a risk that a connection failure such as the contact 2a coming into incomplete contact with the terminal 3a of the cable to be measured 3 may occur. , an erroneous measurement result such as an infinite insulation resistance value of the cable 3 to be measured may be obtained.

Further, if there is a connection failure between the measurement terminal 2d and the connection terminal 2d, an erroneous measurement result will similarly be obtained.

The present invention has been made to solve these problems, and provides an inspection device for measuring cable insulation resistance that can inspect whether or not there is a connection failure between the cable to be measured and the insulation resistance measuring device. The purpose is to provide

(Means for Solving the Problems) The present invention detects the amount of charge by integrating the charging current with an integrator in a cable to be measured that is charged by applying a DC high voltage using an insulation resistance measuring device. The method is characterized in that the obtained charge detection signal is supplied to a determination circuit to determine the connection state between the cable under test and the insulation resistance measuring device.

(For Insulation) If the amount of charge of the charging current to the cable under test is equal to or higher than the set level, it is determined that the connection between the cable under test and the insulation resistance measuring device is good, and the insulation resistance measurement value of the cable under test is determined. judge it to be accurate.

If the amount of charge of the charging current to the cable under test is below the set level, it is determined that there is a poor connection between the cable under test and the insulation resistance measuring device, and the insulation resistance measurement value of the cable under test is incorrectly measured. I judge that there is.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram schematically showing a cable insulation resistance measurement method including the inspection device of the present invention.

In FIG. 2, reference numeral 1 denotes an insulation resistance measuring device, which is connected in series with the inspection device 10 of the present invention. Connection terminal 5
a is connected to the measurement terminal 2d of the switchgear device 2,
The measurement terminal 2d is connected to the contactor 2a via a lead wire 2b and a ring switch 2C. As described above, the contactor 2a is shaped like a brush, contacts the terminal 3a of the cable to be measured 3, and is electrically connected to the cable to be measured 3. A motor load circuit 4 is connected to the cable 3 to be measured.

FIG. 1 is a circuit diagram of an inspection apparatus 10 according to the present invention. In this figure, 11 indicates an integrator. This integrator 11 consists of an operational amplifier 12 and a capacitor 13 connected between its output and an inverting input terminal.
It is connected to the. The non-inverting input terminal of the operational amplifier 12 is connected to the inverting input terminal via another resistor 16, and is also connected to the other input terminal 15b. operational amplifier 12
A determination circuit 17 is connected to the output side of the circuit. The determination circuit 17 includes an operational amplifier 18 as a comparator, and the output side of the operational amplifier 12 is connected to the inverting input terminal of the operational amplifier 18.

The negative pole side of one power supply is connected to the non-inverting input terminal of the operational amplifier 18, and a set voltage of, for example, -5V is applied by this power supply 19. A digital recorder 20 is connected to the output side of the operational amplifier 12. Also, on the output side of the operational amplifier 12, there is an RS-clip flop (F-
F) 210 circuits set terminals S are connected. R.S.
-LED22 is connected to the Q output of the F・F circuit 21,
The reset terminal R is connected to the output side of the timer 23. A predetermined time is set in the timer 23. This timer 23 is further connected to the set terminal (i') of a set switch 24. This set switch 24 is used to short-circuit between the manual terminals 15a and 15b.

Furthermore, the non-inverting input terminal of another output amplifier 25 and the input terminal 1.1 are connected between the input terminals 15a and 15b. This operational amplifier 25 is used to detect the charging current 1, and its output side is connected to the input side of the timer 230 and the reset terminal of the reset switch 26, respectively.

Noset switch 26 connects capacitor 13 of integrator 11
connected in parallel.

Here, the operation of the insulation resistance measurement system will be explained with reference to FIG. Normally, the inspection device 10 of the present invention is used as an insulating device 1, and in such a state,
The insulation resistance measuring device 1 applies a DC high current ratio of about 500 to IOOOV to the cable to be measured 3 via the switchgear device 2 . Therefore, the insulation resistance of the cable 3 to be measured is measured by the insulation resistance measuring device 1 by detecting current or the like. Furthermore, since the cable to be measured 3 has capacitance, the contactor 2a of the switchgear device 2 is in reliable contact with the end -J' 3a of the cable to be measured 3, and the other connections are also in good condition. In this case, the cable 3 will be charged with current.

Now, when measuring insulation resistance, the inspection device 10 of the present invention includes:
As shown in FIG. 1, the manual terminal 1. Charging current i flows into 5a. When charging current 1 flows, operational amplifier 25
detects this and outputs a detection signal of r l{ J, so that the reset switch 26, which had been closed, is reset to the open state at the same time as the timer 23 starts operating. Therefore, a charging current i flows into the capacitor 13, and the operational amplifier 12 integrates this current 1 to calculate the amount of charge.

That is, the operational amplifier 12 outputs the 7h R detection signal S (negative direction). If the amount of charge in the charging current 1 is large, the voltage of the charge detection signal S becomes smaller (for example, 7V) than the set voltage of the power supply 19 (for example, -5V), so the operational amplifier 18 outputs a positive judgment signal SJ. . Therefore,
RS-F・T circuit 21 set human power S to rH
J is input, so the Q terminal is set to r l−{ J,
Retained. As a result, since L E I') 2 2 emits light, it is determined that the cable under test 3 and the insulation resistance measuring device 1 are well connected. It can be seen that insulation resistance measurements were carried out.

For this 1], the measuring cable 3 and the insulation resistance measuring device 1 are
If there is a poor connection between the
The voltage will be higher than the set voltage of 9, for example, -3V. Therefore, the negative judgment signal SJ from the operational amplifier 18
is output, the Q terminal of the RSR'/F circuit 21 is held at rLJ, and the LED 2 2 does not emit light. Therefore, it can be determined that there is a poor connection between the cable to be measured 3 and the insulation resistance measuring device 1, and it can therefore be determined that the insulation resistance measurement value of the cable to be measured 3 is inaccurate.

Incidentally, since the charge detection signal S from the operational amplifier 12 is also supplied to the digital recorder 20, the amount of charge Q can be determined from this recording result. It is also possible to know the maximum applied voltage (2) by the insulation resistance measuring device 1. Therefore, the capacitance C of the cable to be measured 3 can be determined using the formula C=Q/V.

On the other hand, when the set time elapses after the timer 23 completes the connection state test, it outputs a signal rHJ.

Therefore, as a result, r H J is input to the reset terminal R of the RS-1''-F circuit 21, so the circuit 21 is reset and switched from the Q terminal to r L J, and the L.
ED 2 2 goes out. Also, set switch 2
4 is closed, the input terminal 1.5a15b is short-circuited, the output of the operational amplifier 25 is stopped, and the reset switch 26 is closed. Therefore, since the charging current i can be discharged, there is no risk of electric shock, etc., and it is safe.

In the above embodiment, an alarm or the like may be used instead of the LED 22.

It goes without saying that the present invention can also be applied to the case where the cable to be measured 3 and the insulation resistance measuring device 1 are directly connected without using the switchgear device 2.

By the way, the current level of charging current i is determined by insulation resistance measuring device 1.
It changes depending on the rate of increase in the applied voltage. Therefore, the connection state between the cable under test 3 and the insulation resistance measuring device 1 cannot be accurately inspected only by detecting the charging current i. However, when detecting the amount of charge of the charging current i as in the present invention, it can always be detected accurately regardless of the applied voltage, so as described above, the cable under test 3 and the insulation resistance can be accurately measured. The connection state with the device 1 can be reliably inspected.

(Effects of the Invention) As explained above, according to the present invention, the charging current of the cable under test is integrated by an integrator to detect the amount of charge, and the detection signal is supplied to the determination circuit. Therefore, it is possible to provide a detection device that can reliably detect whether or not the connection state between the cable to be measured and the insulation resistance measuring device is good. Therefore, the insulation resistance of the cable to be measured can be accurately measured.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of the inspection device according to the present invention, Fig. 2 is a schematic diagram of a cable insulation resistance measurement method including the device of Fig. 1, and Fig. 3 is a schematic diagram of a conventional cable insulation resistance measurement method. It is a diagram. 1 ----1 insulation resistance measuring device, 2-11--switch gear device, 2a--1 contact, 3-----1 cable to be measured, 1.1--1 integral Vessel, 12, 18. 25---Obeamp, 1 3---
---Capacitor, 1 7-1--1 judgment circuit, 2 1--1--RS-flip-flop circuit, 23
-----One timer.

Claims (1)

[Claims] A device for inspecting a connection state between a cable to be measured and an insulation resistance measuring device that applies a DC high voltage to the cable to measure its insulation resistance, the device inspecting the connection state of the cable to be measured by applying the DC high voltage to the cable to be measured. 1. An inspection device for measuring cable insulation resistance, comprising: an integrator that integrates a charging current charged to a battery and outputs a charge detection signal; and a determination circuit that determines a connection state based on the charge detection signal.