JPH03194477A - Self-diagnostic method for insulation resistance measuring device - Google Patents

Abstract

PURPOSE:To measure the insulation resistance of cable in a live-line state by providing a drive detecting current transformer between a power amplification part and a transformer for injection in the main body of a device, and applying a detected primary winding current of the transformer for injection to a current transformer through a self-diagnostic switch. CONSTITUTION:When the transformer 1 for injection is normally connected, a driving current of transformer for injection flows from the power amplification part 2 and a signal is generated at the secondary side of drive detecting current transformer 3. This signal is amplified in a self-diagnostic amplification part 4 and applied to the secondary winding of leakage detecting current transformer 6 through the self- diagnostic switch 5. In the case the transformer 1 for injection is not provided, the driving current does not flow at the time when the primary winding is disconnected, and a voltage is not impressed on the secondary winding of leakage detector even if the self-diagnostic switch 5 is depressed. If the number of winding turns for primary and secondary windings of the driving detecting current transformer 3 is selected, the self-diagnostic amplification part 4 can be excluded. By this constitution, the self-diagnosis can be made for a measuring device of the insulating state including the connection state of transformer 1 for injection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a self-diagnosis method for a device that measures the insulation resistance of an electric circuit in a live line state.

[Prior art]

Figure 2 (a) shows the self-diagnosis method of the insulation resistance measuring device from 1F
).

After amplifying the power of the signal generated by the low-frequency signal generator for measurement, it is injected into the grounding wire via the injection transformer, and this signal voltage flows through the insulation resistance R9 and ground capacitance C8 and returns to the grounding wire. In an insulation resistance measuring device that uses a method to measure the insulation resistance of a circuit by detecting the current with a leakage detection current transformer, amplifying it, and extracting only the insulation resistance component in a rectifying section, the output of the power amplifying section is It has been common practice to apply a signal to the secondary winding of a leakage detection current transformer through a self-diagnostic switch. When the self-diagnosis switch is pressed in this way, a low frequency signal voltage for measurement is generated across the resistor R1, and if the leakage detection current transformer is properly connected to the main body of the device, a low frequency signal voltage for measurement is generated across the termination resistor RL. A signal voltage is generated and subsequent circuits operate. Furthermore, if the leakage detection current transformer is not connected to the main body of the device or if the secondary winding is disconnected, no voltage is generated across the termination resistor RL, so the subsequent circuits do not operate.

[Problem that the invention seeks to solve]

As described above, the conventional self-diagnosis method can diagnose the connection state of the leakage detection current transformer and the operation of the main body of the device, but has the drawback that it cannot confirm the connection state of the injection transformer. Therefore, as shown in Figure 2 (b), a method can be considered in which a tertiary winding is provided in the injection transformer and self-diagnosis is performed using the voltage generated in this tertiary winding. There are disadvantages such as incorrect connection of the tertiary winding and complicated wiring work.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for self-diagnosing an insulation state measuring device, including the connection state of an injection transformer, while performing wiring work as before.

[Means to solve the problem]

This will be explained using the embodiment shown in FIG. 1(a).

A drive detection current transformer is provided between the power amplification section and the injection transformer in the main body of the device. When the injection transformer is normally connected, the injection transformer drive current flows from the power amplifier section, generating a signal on the secondary side of the drive detection current transformer. This signal is amplified by a self-diagnosis amplifier and applied to the secondary winding of the leakage detection current transformer through a self-diagnosis switch.

The subsequent operation is the same as the conventional operation shown in FIG. 2(a). If the injection transformer is not connected or the primary winding is disconnected, the drive current will not flow, so even if you press the self-diagnosis switch, there will be no voltage in the secondary winding of the leakage detection current transformer. I won't join. It is also possible to eliminate the self-diagnosis amplifier section by selecting the number of turns of the primary and secondary windings of the drive detection current transformer.

Furthermore, as shown in Figure 1 (b), when an overcurrent flows through the grounding wire side of the injection transformer, it prevents damage to the main body of the device due to abnormal voltage generated on the primary side of the injection transformer. It can be used in common with the overcurrent detection current transformer of the overcurrent protection circuit.

(Effects) (1) Self-diagnosis including the connection status of the injection transformer becomes possible.

(2) By sharing parts with the overcurrent protection circuit, it is possible to configure the circuit without using new parts.

(3) Since a current transformer is used to detect the drive current, it can be isolated in terms of direct current, and no spillover accidents will occur in the event of a failure.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram for implementing the present invention, FIG. 1(b) is a block diagram of a case where the present invention is combined with a conventionally devised overcurrent protection circuit, and FIG. 2(a) is a block diagram for implementing the present invention. 2(b) is a block diagram showing a conventionally devised self-diagnosis method, and FIG. 2(b) is a block diagram showing a conventionally devised self-diagnosis method to solve the problem of FIG. 2(a).

Claims (1)

[Claims] A low frequency signal voltage for measurement different from the commercial frequency is applied to the ground wire of the transformer via an injection transformer to the electrical circuit, and a leakage detection current transformer coupled to the ground wire is used to feed back the measurement signal voltage to the ground wire. In a device for detecting a leakage current component of a low frequency signal and detecting a component resulting from insulation resistance among the leakage current component, a drive detection current transformer is provided between the device and the injection transformer, and the injection transformer 1. A self-diagnosis method for an insulation resistance measuring device, comprising: detecting a current flowing through a primary winding of the transformer, and applying an amplified signal to the detection current transformer through a self-diagnosis switch.