JP4835286B2 - Insulation monitoring system and method for low voltage electrical equipment - Google Patents

Description

  The present invention relates to an insulation monitoring method and method for low-voltage electrical equipment that monitors insulation degradation (leakage) of a low piezoelectric path with a magnitude of an effective current of a ground line current with respect to a ground voltage of the low piezoelectric path to be monitored, and particularly, a low voltage The phase difference between the ground voltage of the electric circuit and the voltage of the control power supply taken from the low piezoelectric path is preset in the insulation monitoring device, and the insulation monitoring device shifts the phase of the control power supply voltage by the set phase difference and the ground voltage phase of the low piezoelectric circuit And a voltage phase difference setting method and method for extracting an effective current component of a ground line current of a low piezoelectric path with reference to this voltage phase.

For insulation monitoring of “low-voltage electrical equipment” such as 100V, 200V lamp circuit, 200V, 400V power circuit, etc., there are three methods: I ₀ (Izero) method, Igr (IZR) method, and I ₀ r (IZR) method There is. The names of these three methods are generally used in the industry, but are not officially defined in the literature.

(1) I ₀ method Large current (zero-phase current) flowing in the ground line on the secondary side (100V circuit or 200V circuit) of the bank for low voltage supply (bank such as 6.6KV / 100V and 6.6KV / 200V) This method detects the deterioration of insulation in the low piezoelectric path by detecting the length. This method is much simpler and requires less equipment than the other two methods described later. However, if the capacitance of the circuit to ground is large, a large charging current flows through the ground wire even when insulation is not reduced, and the detection of minute leakage current at the time of high-resistance leakage cancels this large leakage current. Therefore, high-sensitivity detection may be difficult.

(2) Igr (IGR) system A small alternating voltage (1 to 2 V) different from the commercial frequency is injected into the secondary ground wire of the low-voltage supply bank. In this method, only the effective current corresponding to the injected voltage is detected from the current flowing through the ground line. This method can detect insulation deterioration with high sensitivity without being affected by the earth capacity of the circuit, but it requires equipment for injecting voltage, or a voltage injection transformer is installed on the ground line. There is also a demerit that the installation work is complicated. A great advantage of this method over the other two methods is that it is possible to detect insulation deterioration of the ground phase.

(3) l ₀ r (eye zero are) method This method was devised to reduce the influence of the ground charging current in the I ₀ method and to solve the complexity of the equipment and construction in the Igr method. is there. In this method, the ground voltage of the low piezoelectric path to be monitored and the ground line current of the bank are input to the insulation monitoring device, and vector calculation is performed inside the device to determine the ground line current with respect to the ground voltage of the low piezoelectric path. The effective component current component is extracted, and the insulation deterioration (leakage) is determined by the magnitude of this component. If the effective current component can be extracted with high accuracy, it is possible to detect insulation deterioration with high sensitivity without being affected by the size of the ground capacity (see, for example, Patent Document 1).

In order to realize this I ₀ r system device, (a) a CT (ZCT) circuit for capturing a ground line current and (b) a VT circuit for capturing a ground voltage of an electric circuit are required. Therefore, the I ₀ method requires only the CT circuit of (a), whereas the I ₀ r method requires a VT circuit, which is twice as complex in terms of the number of input circuits of the device.

  As a measure for reducing the complexity of the input circuit, there is the following method that eliminates the need to take in the ground voltage of the low piezoelectric path in the normal state.

(3a) Voltage phase difference setting method In this method, the voltage phase difference between the control power supply voltage of the insulation monitoring device and the ground voltage of the electric circuit to be monitored is set in advance. In other words, the person calculates the phase difference between the two circuits based on the winding connection relationship between the transformer to which the control power of the insulation monitoring device is supplied and the transformer of the electric circuit to be monitored, and sets this value in advance. . Then, when calculating the effective current flowing in the ground line of the monitoring target circuit in the insulation monitoring device, the control power supply voltage is shifted (phase-shifted) by the phase difference set as described above, and with respect to the shifted voltage. The effective current component included in the ground line current is obtained.

(3b) Voltage phase difference setting method In the above method (3a), it is necessary to calculate in advance the phase difference between the device control power supply voltage and the ground voltage of the monitoring target electric circuit from the equipment drawing or the like. This is not only complicated but also causes human errors and may be set incorrectly.

  Therefore, as a method for setting the voltage phase difference without calculating, one setting-dedicated input circuit for taking in the ground voltage phase of the low piezoelectric path to be monitored is provided. When setting the voltage phase difference, the ground voltage of the circuit to be monitored is input to this dedicated input circuit, the phase difference between this ground voltage and the control power supply voltage is calculated internally, and the phase difference is calculated. Information is automatically stored as set values in the same manner as in the method (3a).

  This (3b) voltage phase difference setting method will be described with reference to FIGS. As shown in FIG. 3, the insulation monitoring apparatus 1 is configured to input current flowing through the ground line on the secondary side (100V single-phase three-wire system) of the low-voltage supply bank (6.6KV / 100V bank) to each bank. Taking in as CH1 and CH2, taking in the device control power supply from the secondary side of one bank (transformer TR1), and further providing one voltage input circuit for phase difference setting.

  As shown in FIG. 4, the vector relationship of the low-voltage side ground voltage of the transformers TR1 and TR2 is that the ground voltage V2 of the transformer TR2 is delayed by 120 ° compared to the ground voltage V1 of the transformer TR1.

  In this device configuration, FIG. 5 shows the connection when the voltage phase difference is initially set. The insulation monitoring apparatus 1 is a person who connects a voltage input circuit for setting a phase difference to the secondary side of the transformer TR2 and takes in the ground voltage. The insulation monitoring apparatus detects the phase difference between the ground voltage phase and the control power supply voltage phase. Means for obtaining the phase difference information for the current CH2 by providing means for calculating by calculation and means for setting that the ground voltage on the transformer TR2 side is taken in the phase difference setting voltage input circuit. Automatically stored as a value. Similarly, the ground voltage of the transformer TR1 is also taken into the voltage input circuit for setting the phase difference, and the phase difference of the ground voltage of the transformer TR1 with respect to the control power supply voltage phase is obtained by calculation. At this time, the ground voltage on the transformer TR1 side is obtained. This phase difference information is automatically stored as a set value for the current CH1 by means for setting that is stored in the phase difference setting voltage input circuit.

  By using the above means, it is assumed that there is no phase error in the phase difference setting voltage input circuit, and that the secondary voltage phase of each transformer is not affected by the load current or can be ignored. From the vector relationship of 4, the phase difference setting for the current CH1 is 0 °, and the phase difference setting for the current CH2 is 120 ° with a delay.

  In the insulation monitoring device 1, the phase of the control power supply voltage is shifted by these set values, and this is used as the reference voltage phase of each bank to obtain the effective component of the ground line current of the monitoring target circuit that becomes the current input of CH1 and CH2. The presence / absence of insulation deterioration is determined from the effective current.

The insulation monitoring device 1 uses a detection current of each zero-phase current transformer as an input to an analog input circuit for each channel, as seen in a general digital protection relay device, and these signals are sequentially converted into A / A by a multiplexer. Some digital signals are sequentially converted into digital signals as an input to the D converter, and a desired monitoring function is established by digital arithmetic processing by a computer. This can be used as a processing device for monitoring insulation deterioration (for example, Patent Document 2).
JP 2006-71341 A JP 2004-362510 A

  The voltage phase difference setting method (3b method) has a demerit compared to the method (3a) in that a dedicated input circuit for voltage phase setting is required. When a large number of low piezoelectric paths are monitored by a single insulation monitoring device, an increase in the number of dedicated input circuits of about one circuit can be ignored.

  FIG. 6 shows an example of an insulation monitoring device using a voltage phase difference setting method (3b method). The figure shows a case where 6 banks of insulation are monitored. The insulation monitoring device 1 is for 6 channels for taking in the ground line currents of the respective transformers Tr1 to Tr6 and for taking in the reference voltage from the control power supply voltage. An input circuit for a total of eight channels is provided for one channel and one channel for taking in the initial setting voltage. As the initial setting voltage, a person switches and takes in the ground voltage of each of the transformers Tr1 to Tr6.

  As in this example, the voltage phase difference setting method (3b method) has the following problems.

  ・ To determine the voltage phase difference between the voltage on the secondary side of the transformer and the control power supply voltage by measurement, two voltage input circuits, the control power supply voltage and the ground voltage, are required. This is only necessary when setting the phase difference, and its utilization efficiency is low.

  Of the input circuits that can be mounted with an insulation monitoring device, two circuits are required for the voltage input, and the number of insulation deterioration monitoring channels that can be used is reduced accordingly.

  -The channel that takes in the initial setting voltage is composed of an electronic circuit such as a transformer for converting the level of the input voltage and an input filter, which naturally have a phase error. It becomes an error when detecting. Let this be ε1. Also, let ε2 be the phase error that occurs in the zero-phase current transformer for taking in the ground line current and the electronic circuit of each monitoring input channel. At this time, if the two phase errors occur in the direction in which they are added, an error of ε1 + ε2 is generated as the phase error of the relevant channel. Therefore, it is necessary to manage both phase errors with high accuracy. come.

  The object of the present invention is to eliminate the need for an initial setting voltage input circuit for measuring the ground voltage of a low piezoelectric path in the insulation monitoring device, and to set the phase difference with high accuracy and to increase the number of insulation deterioration monitoring channels. It is an object of the present invention to provide an insulation monitoring method and method that can be used.

  In order to solve the above-mentioned problems, the present invention applies a ground voltage of a low piezoelectric path to be monitored to a resistor or a capacitor, and uses a zero-phase current transformer for detecting a current flowing through the resistor or the capacitor as a ground line current. The current is input by the current input circuit of the insulation monitoring device. The phase of the detection current is in phase with the ground voltage of the low piezoelectric path when a resistor is used, and is 90 ° ahead of the ground voltage of the low piezoelectric path when a capacitor is used. The phase difference between the detected current phase and the control power supply voltage is automatically determined by determining the phase difference between the detected current and the control power supply voltage, and is characterized by the following methods and methods: .

(1) A zero-phase current transformer that detects a ground line current of a low-piezoelectric path to be monitored, a current input circuit that takes in the ground-line current detected by the zero-phase current transformer, and a control power supply that takes in a control power from the low piezoelectric path An insulation monitoring device having an input circuit,
The insulation monitoring device obtains the ground voltage phase of the low piezoelectric path by shifting the phase of the voltage of the control power supply by the phase difference φ between the ground voltage of the low piezoelectric path and the voltage of the control power supply, and calculates the ground voltage phase. Extraction of the effective component current of the ground line current of the low piezoelectric path detected by the zero-phase current transformer as a reference, and monitoring the insulation degradation (leakage) of the low piezoelectric circuit with the magnitude of this effective component current An insulation monitoring method,
The insulation monitoring device includes:
Prior to insulation monitoring, the ground voltage of the low piezoelectric path is applied to the resistor or capacitor by a probe connection, and the current flowing through the resistor or capacitor is temporarily removed from the ground line of the low piezoelectric path. Means for detecting as a secondary current of the zero-phase current transformer in a circuit configuration in which the probe is passed through, and inputting to the current input circuit;
Computation means for obtaining a ground voltage phase of the low piezoelectric path from a current flowing through the resistor or capacitor input to the current input circuit, and obtaining the phase difference φ from the ground voltage phase and the voltage phase of the control power supply. It is characterized by that.

(2) There are multiple low piezoelectric paths to be monitored, and current input channels and zero-phase current transformers are also provided for the number N of monitored circuits, and the phase difference φ _N between the ground voltage and the control power supply is obtained for each current input channel. If advance, connecting the probe to the low pressure path N, which is passed through the primary side of the ZCT N for monitoring the path, obtains a voltage phase of the low-pressure path from the time of the current phase, A means for setting the phase difference φ _N between this and the control power supply voltage as the phase difference φ of the channel (CH-N) is provided.

(3) The zero-phase current transformer obtains the phase difference φ by switching only a probe to a plurality of low piezoelectric paths N in a state where the zero-phase current transformer is connected to a representative current input channel of the insulation monitoring device. The phase difference φ _N for each channel is set by providing means for indicating the relationship with the current input channel for monitoring the low piezoelectric path.

(4) The insulation monitoring device includes the control power supply voltage Vs, the ground line current I ₀ of the low piezoelectric path, the phase difference θ between the voltage Vs and the ground line current I ₀ , the control power supply voltage and the ground voltage of the low piezoelectric path. From the phase difference φ with
_{I 0 r = cosφ · | I} 0 | cosθ + sinφ · | I 0 | sinθ
= | I ₀ | cos (θ−φ)
Accordingly, characterized by comprising a calculating means for determining the active current I ₀ r.

(5) A zero-phase current transformer for detecting the ground line current of the low piezoelectric path to be monitored, a current input circuit for taking in the ground line current detected by the zero phase current transformer, and a control power supply for taking in the control power from the low piezoelectric path An insulation monitoring device having an input circuit,
The insulation monitoring device determines a ground voltage phase of the low-pressure path by shifting the phase of the voltage of the control power in the phase difference φ between the ground voltage and the voltage of the control power of the low-pressure path, the ground voltage phase Extraction of the effective component current of the ground line current of the low piezoelectric path detected by the zero-phase current transformer as a reference, and monitoring the insulation degradation (leakage) of the low piezoelectric circuit with the magnitude of this effective component current An insulation monitoring method comprising:
The insulation monitoring device includes:
The zero-phase current transformer is temporarily removed from the ground line of the low piezoelectric path, a ground voltage of the low piezoelectric path is applied to a resistor or a capacitor by a probe connection, and the current flowing through the resistor or capacitor is supplied from the ground line of the low piezoelectric path. Detected as a secondary current of the zero-phase current transformer in a circuit configuration in which the probe is passed through the primary side of the zero-phase current transformer once removed, and input to the current input circuit,
The ground voltage phase of the low piezoelectric path is obtained from the current flowing through the resistor or capacitor input to the current input circuit, and the phase difference φ is obtained from the ground voltage phase and the voltage phase of the control power supply. To do.

(6) There are multiple low-voltage paths to be monitored, and current input channels and zero-phase current transformers are also provided for the number N of monitored circuits, and the phase difference φ _N between the ground voltage and the control power supply is obtained for each current input channel. If advance, connecting the probe to the low pressure path N, which is passed through the primary side of the ZCT N for monitoring the path, obtains a voltage phase of the low-pressure path from the time of the current phase, The phase difference φ _N between this and the control power supply voltage is set as the phase difference φ of the channel (CH−N).

(7) In the state where the zero-phase current transformer is connected to one representative current input channel of the insulation monitoring device, the probe is switched to a plurality of low piezoelectric paths N to obtain the phase difference φ and switched. In some cases, the phase difference φ _N for each channel is set by adding information indicating the relationship with the current input channel for monitoring the low piezoelectric path.

  As described above, according to the present invention, a ground voltage of a low piezoelectric path to be monitored is applied to a resistor or a capacitor, and a current flowing through the resistor or the capacitor is utilized using a zero-phase current transformer for detecting a ground line current. Since the insulation monitoring device side uses the current input circuit of the insulation monitoring device to determine the phase of the ground voltage from the detected current, the phase difference between the ground voltage and the control power supply voltage is determined and set. Eliminates the need for a dedicated voltage input circuit for measuring the ground voltage of the low piezoelectric path, allows the phase difference to be set with high accuracy, and increases the number of insulation deterioration monitoring channels.

  Specifically, by converting the line voltage of each line into a current, a voltage input circuit for initial setting becomes unnecessary.

  Also, since the converted current input uses a zero-phase current transformer in the monitoring circuit, a simple probe that only penetrates the current transformer can be used to detect the phase difference between the ground voltage and the control power supply voltage. That's it.

  In addition, since the voltage circuit for initial setting can be switched to the current monitoring circuit, the function can be expanded by increasing the current monitoring by one channel.

  In addition, since the phase difference for calculating the effective component current includes the error component of the zero phase current transformer, the error component of the zero phase current transformer can be set by setting the phase difference using the same zero phase current transformer ZCT. It is possible to increase the insulation deterioration determination accuracy by offsetting.

  Moreover, since the ground voltage of the electric circuit is converted into a current and penetrated by a probe in a zero-phase current transformer actually attached to the low piezoelectric circuit, the channel can be set without making a mistake.

  FIG. 1 is a basic configuration diagram of an insulation monitoring system showing an embodiment of the present invention. This figure shows a case of a low-voltage electric facility having a two-bank configuration with transformers TR1 and TR2. The insulation monitoring device 1 enables voltage phase difference setting and insulation monitoring by the above-described (3b) method by using a 2-channel current input circuit and a control power supply input circuit. Deterioration monitoring will be described in detail.

(1) Voltage Phase Difference Setting As shown in FIG. 1, the insulation monitoring device 1 uses one current input circuit when setting the voltage phase difference without providing a voltage input circuit for setting the phase difference. In the conventional method, the phase information of the ground voltage of the low piezoelectric path to be monitored is captured by the voltage input circuit, whereas in this embodiment, the ground voltage phase is obtained by using a zero-phase current transformer (ZCT) for capturing the ground line current. Is obtained as the current phase, and the phase information of the ground voltage is obtained by the following procedure and set as the phase difference information in the insulation monitoring device.

  (S1) When setting the phase difference, the zero-phase current transformer ZCT2 is once removed from the ground line of the transformer TR2.

  (S2) A probe having lead wires 3 connected to both ends of the resistor 2 is prepared, and this lead wire is passed through as a primary conductor of the above-described zero-phase current transformer ZCT2, or the zero-phase current transformer ZCT2 serves as a primary conductor. In the case of the gripping mechanism, the lead wire is gripped.

  (S3) The probe is brought into contact with the point where the ground voltage of the monitoring target circuit is applied, and the ground voltage of the transformer TR2 is applied to the resistor 2. At this time, the phase of the current flowing through the resistor 2 is in phase with the phase of the ground voltage of the low piezoelectric path.

  (S4) The current flowing through the resistor 2 is detected as the secondary current of the zero-phase current transformer ZCT2, and is captured by the current input circuit (CH2) of the insulation monitoring device 1, and the same phase information as the ground voltage is input to this current input circuit. obtain.

  (S5) In the insulation monitoring device 1, the phase difference between the phase of the control power supply voltage and the captured current is calculated and stored as a phase difference setting value.

  The above operations (S2 to S5) are also performed for the ground voltage of the transformer TR1, and the voltage phase difference between the ground voltage of the transformer TR1 and the control power supply is calculated and stored as a phase difference set value. That is, the probe and the zero-phase current transformer set have a phase corresponding to the ground voltage of each low piezoelectric path by switching the probe to a plurality of low piezoelectric paths in a state where the probe is connected to one current input channel of the insulation monitoring device 1. Detect current. At the time of this switching, information indicating the relationship with the current input channel for monitoring the low piezoelectric path is also attached.

  Therefore, for setting the voltage phase difference, a probe in which the lead wire 3 is connected to the resistor 2 is prepared, and one zero-phase current transformer (ZCT) for detecting the ground wire current is removed from the ground wire. The lead wire of the probe is coupled to the current transformer (ZCT) as a primary conductor, the resistance current obtained in the zero-phase current transformer (ZCT) is taken in by the current input circuit of the insulation monitoring device 1, and the ground voltage in the insulation monitoring device Is extracted as a voltage signal in phase with the control power supply voltage, and a phase difference from the control power supply voltage is obtained and set as a phase difference.

  According to this setting method, the voltage input circuit for setting the phase difference becomes unnecessary. Further, the converted current input can use a zero-phase current transformer ZCT for detecting the ground line current, and a simple probe can be prepared. Further, since the voltage input circuit for setting the phase difference can be used for the current monitoring circuit, the function can be expanded by increasing the number of monitoring targets by one channel. In addition, since the phase difference setting includes the error of the zero-phase current transformer ZCT, the error of the zero-phase current transformer is canceled by the phase difference setting using the same zero-phase current transformer ZCT. It is possible to improve the insulation deterioration judgment accuracy. In addition, the probe coupled to the zero-phase current transformer can measure the ground voltage of other channels, and it becomes easy to set a plurality of channels sequentially.

  In the insulation monitoring device 1, it is necessary to consider the power capacity of the resistor 2 when the ground voltage of the transformer is converted into a current by the resistor 2. Although depending on the current flowing through the resistor, a certain amount of capacitance is required so that the resistor does not generate heat. For example, if a 200 mA circuit is used to flow 100 mA, the rated power of the resistor is required to be 20 W or more, and if a margin is included in this, a large resistor of about 40 W is required. Instead of the resistor 2, a system using a capacitor that does not require consideration for heat generation may be used. When a capacitor is used, the current phase advances 90 ° with respect to the voltage, so this is corrected for the calculation result when the phase difference is set.

(2) Example of insulation deterioration monitoring using set phase difference The insulation monitoring apparatus 1 calculates the effective and ineffective portions of the zero-phase current and the control power supply voltage of the grounding wire, and the phase difference calculated above for this By multiplying the phase difference correction coefficient determined by the above, the magnitude of the effective current with reference to the ground voltage of the electric circuit is obtained, and the insulation deterioration is determined. An example of this is shown below.

As shown in FIG. 2A, the effective part and the ineffective part of the zero-phase current I ₀ of the ground line with respect to the control power supply voltage Vs are the effective part = | I ₀ | cos θ, the ineffective part from the phase difference θ therebetween. = | I ₀ | sin θ.

The phase difference between the control power supply voltage Vs and the ground voltage of the monitoring target circuit is obtained by the above (1) voltage phase difference setting. If this phase difference is φ, the phase difference φ in FIG. And the phase difference θ, the effective component I ₀ r of the zero-phase current is obtained by the following calculation.
[number]
_{I 0 r = cosφ · | I} 0 | cosθ + sinφ · | I 0 | sinθ
= | I ₀ | cos (θ−φ)
I ₀ : Zero phase current of ground wire of each transformer, | I ₀ |: Effective value of zero phase current I ₀ of ground wire , cosφ, sinφ: Phase difference correction coefficient (φ is phase difference)
As shown in FIG. 2 (c), the insulation deterioration is determined based on whether or not the magnitude of the effective component I ₀ r of the zero-phase current obtained above exceeds a preset value. can do.

In the embodiment, the zero-phase current transformer is connected to one current input channel representative of the insulation monitoring device, and only the probe is switched to the plurality of low piezoelectric paths N to obtain the phase difference φ, and This is a case where the phase difference φ _N for each channel is set by providing means for indicating the relationship with the current input channel for monitoring the low piezoelectric path when switching. In this case, the effect of canceling the phase error between the zero-phase current transformer and the input channel of each channel cannot be expected.

In order to obtain this canceling effect, the phase difference φ _N may be set for each channel N using the zero-phase current transformer. That is, there are a plurality of low-voltage paths to be monitored, and current input channels and zero-phase current transformers are provided for the number N of monitored circuits, and the ground voltage and control power supply phase difference φ _N are set for each current input channel. In this case, the probe is connected to the low piezoelectric path N, and this is passed through the primary side of the zero-phase current transformer N for monitoring the current circuit, and the voltage phase of the low piezoelectric path is obtained from the current phase at this time. By setting the phase difference φ _N of the control power supply voltage as the phase difference φ of the channel (CH−N), even if a phase error ε 2 exists between the monitoring zero-phase current transformer and the input channel, the initial phase difference φ _N Since this phase error is set at the time of setting, a highly accurate setting is possible.

  More specifically, in a probe that converts a low piezoelectric path to be monitored into a current, for example, when a resistor is used, the phase difference between the voltage of the monitored circuit and the current flowing through the probe is 0 °. If this is taken in by a circuit having a sum ε2 of the phase error of the zero-phase current transformer and the phase error of the input channel of the circuit, 0 ° + ε2. If the true phase difference between the control power supply voltage phase and the monitoring target circuit is θ, the error is added to the initial setting phase difference calculated in the insulation monitoring device, and θ + ε2. Here, when the true phase of the current flowing through the ground line of the circuit when the leakage actually occurs with respect to the control power supply voltage of the insulation monitoring device is δ, the insulation monitoring device has a phase difference of δ + ε2 including an error. Current phase is determined based on the phase of the control power supply voltage shifted by the initial setting value (θ + ε2), so the difference between the two becomes δ-θ, and the error is canceled, resulting in higher accuracy. Can be planned.

The basic block diagram of the insulation monitoring system which shows embodiment of this invention. FIG. 6 is a relationship diagram of phase differences φ and θ in the embodiment. Diagram of I ₀ r insulation monitoring system. The vector relationship figure of the low voltage side voltage of transformer TR1, TR2. Connection diagram when setting the voltage phase difference. The example of the insulation monitoring apparatus by 3b system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation monitoring apparatus 2 Resistance 3 Lead wire TR1, TR2 Transformer ZCT1, ZCT2 Zero phase current transformer

Claims (7)

A zero-phase current transformer that detects a ground line current of a low piezoelectric path to be monitored, a current input circuit that captures a ground line current detected by the zero phase current transformer, and a control power input circuit that captures a control power from the low piezoelectric path An insulation monitoring device having
The insulation monitoring device obtains the ground voltage phase of the low piezoelectric path by shifting the phase of the voltage of the control power supply by the phase difference φ between the ground voltage of the low piezoelectric path and the voltage of the control power supply, and calculates the ground voltage phase. Extraction of the effective component current of the ground line current of the low piezoelectric path detected by the zero-phase current transformer as a reference, and monitoring the insulation degradation (leakage) of the low piezoelectric circuit with the magnitude of this effective component current An insulation monitoring method,
The insulation monitoring device includes:
Prior to insulation monitoring, the ground voltage of the low piezoelectric path is applied to the resistor or capacitor by a probe connection, and the current flowing through the resistor or capacitor is temporarily removed from the ground line of the low piezoelectric path. Means for detecting as a secondary current of the zero-phase current transformer in a circuit configuration in which the probe is passed through, and inputting to the current input circuit;
Computation means for obtaining a ground voltage phase of the low piezoelectric path from a current flowing through the resistor or capacitor input to the current input circuit, and obtaining the phase difference φ from the ground voltage phase and the voltage phase of the control power supply. Insulation monitoring system for low voltage electrical equipment. When there are multiple low-voltage paths to be monitored, current input channels and zero-phase current transformers are provided for the number N of monitored circuits, and the phase difference φ _N between the ground voltage and the control power supply is obtained for each current input channel The probe is connected to the low piezoelectric path N, and this probe is passed through the primary side of the zero-phase current transformer N for monitoring the current path, and the voltage phase of the low piezoelectric path is obtained from the current phase at this time and controlled. insulation monitoring system of the low-pressure electrical equipment according to claim 1, a phase difference phi _N is characterized by having a means for setting as said phase difference phi in the channel (CH-N) of the power supply voltage. The zero-phase current transformer is connected to one current input channel representative of the insulation monitoring device, and only the probe is switched to a plurality of low piezoelectric paths N to obtain the phase difference φ. 2. The insulation monitoring system for low-voltage electrical equipment according to claim 1, wherein a phase difference φ _N for each channel is set by providing means for indicating a relationship with a current input channel for monitoring a low piezoelectric path. The insulation monitoring device includes the control power supply voltage Vs, the ground line current I ₀ of the low piezoelectric path, the phase difference θ between the voltage Vs and the ground line current I ₀ , and the levels of the control power supply voltage and the ground voltage of the low piezoelectric path. From the phase difference φ, the following calculation:
_{I 0 r = cosφ · | I} 0 | cosθ + sinφ · | I 0 | sinθ
= | I ₀ | cos (θ−φ)
Accordingly, the insulation monitoring system of the low-pressure electrical equipment according to any one of claims 1 to 3, further comprising a calculating means for determining the active current I ₀ r. A zero-phase current transformer that detects a ground line current of a low piezoelectric path to be monitored, a current input circuit that captures a ground line current detected by the zero phase current transformer, and a control power input circuit that captures a control power from the low piezoelectric path An insulation monitoring device having
The insulation monitoring device determines a ground voltage phase of the low-pressure path by shifting the phase of the voltage of the control power in the phase difference φ between the ground voltage and the voltage of the control power of the low-pressure path, the ground voltage phase Extraction of the effective component current of the ground line current of the low piezoelectric path detected by the zero-phase current transformer as a reference, and monitoring the insulation degradation (leakage) of the low piezoelectric circuit with the magnitude of this effective component current An insulation monitoring method comprising:
The insulation monitoring device includes:
The zero-phase current transformer is temporarily removed from the ground line of the low piezoelectric path, a ground voltage of the low piezoelectric path is applied to a resistor or a capacitor by a probe connection, and the current flowing through the resistor or capacitor is supplied from the ground line of the low piezoelectric path. Detected as a secondary current of the zero-phase current transformer in a circuit configuration in which the probe is passed through the primary side of the zero-phase current transformer once removed, and input to the current input circuit,
The ground voltage phase of the low piezoelectric path is obtained from the current flowing through the resistor or capacitor input to the current input circuit, and the phase difference φ is obtained from the ground voltage phase and the voltage phase of the control power supply. Insulation monitoring method for low voltage electrical equipment. When there are multiple low-voltage paths to be monitored, current input channels and zero-phase current transformers are provided for the number N of monitored circuits, and the phase difference φ _N between the ground voltage and the control power supply is obtained for each current input channel The probe is connected to the low piezoelectric path N, and this probe is passed through the primary side of the zero-phase current transformer N for monitoring the current path, and the voltage phase of the low piezoelectric path is obtained from the current phase at this time and controlled. insulation monitoring method for a low pressure electrical equipment according to claim 5, a phase difference phi _N of the power supply voltage and sets as the phase difference phi in the channel (CH-N). The zero-phase current transformer is connected to one representative current input channel of the insulation monitoring device, and the probe is switched to a plurality of low piezoelectric paths N to obtain the phase difference φ and 6. The insulation monitoring method for low-voltage electrical equipment according to claim 5, wherein information indicating a relationship with a current input channel for monitoring an electric circuit is added to set a phase difference φ _N for each channel.

Images