JP2006200898A - Interrupt insulation measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive insulation measuring device with technical advantages capable of measuring live-wire insulation in block of transformer and substation, comparing and confirming rapidly questionable measured results of insulation state, and performing insulation exploration in noisy environment of semiconductor power equipment including inverters. <P>SOLUTION: Alternating of a circuit conductor for the desired measuring leg between the two points in a direct current electrical facilities to be measured with a condenser makes it possible to implement direct current insulation resistance measurements. A power source with low frequency is prepared for performance measurement of the aforementioned condenser, also improvement of noise tolerance ability is attempted by making the Igr insulation measurement possible with the low frequency of the facility using the present voltage, and thus enhancement of reliability and efficiency is attempted for surveys of weakened insulation accident points in live line. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to hot-wire insulation measurement of electrical equipment.

  In general, insulation measurement of electrical equipment uses a DC-type insulation resistance meter, but there is a problem that measurement is not possible unless a power failure occurs.

Regarding the method of measuring ground insulation resistance while using AC electrical equipment in a non-grounded low-voltage distribution line, a DC voltage is used as an insulation detection power supply, and a reactor with an AC resistance that does not impair the characteristics of non-grounding A hot-wire insulation monitoring device that has been used for a long time has been used to obtain an insulation resistance from an applied voltage and a flowing current applied between an electric circuit and the ground through a resistor or the like. (See Figure 5)
This method is less affected by AC noise and can be measured at low cost and with high reliability, so it can be used to monitor a wide range of insulation groups, such as monitoring low-voltage circuits from a transformer at once. However, when insulation deterioration is detected by this apparatus, there is a problem that there is no means for performing exploration measurement for identifying a defective part with a live line.

  In the method of measuring ground insulation while using AC electrical equipment in a direct grounding type low-voltage distribution circuit, an AC voltage of a frequency different from the commercial frequency is applied between the circuit and the ground, and the current flowing through this voltage is added. An Igr type insulation state monitoring device as shown in FIG. 6 is used which detects a resistance current, that is, an effective current, and determines the insulation state based on the detected magnitude. (For example, see Patent Document 1 and Non-Patent Documents 1 and 2)

  However, problems such as an error current due to noise generated by power semiconductor devices and the like, and interference interference due to a noise frequency that is the same as or close to the AC power supply frequency used for insulation detection are unavoidable. (For example, see Patent Document 3)

  The Igr method is an application principle of the wattmeter method that measures the effective current by applying an AC voltage to the insulation part. There is a serious problem that the effective current due to electric power is added and the DC effective current calculated from the insulation resistance value measured by DC may not be equal.

  In order to reduce the error current caused by the loss resistance, it is necessary to lower the frequency of the detection signal, but there is a problem that the transformer used for electromagnetic coupling to the ground line becomes large and is not practical.

  As a method for superimposing a low-frequency detection signal voltage, a method has been devised in which an Igr insulation measurement voltage is applied to a ground resistance interposed between a B-type ground electrode and a D-type ground electrode, and the voltage drop is used. (For example, see Patent Document 2)

Patent Publication No. 38-15653 JP-A-6-258363 JP 2004-271285 A “Production and Electricity”, April 30, 1992, published by NEC Association “Overview and Features of Igr Insulation Monitoring System” Kozo Kataoka “High Voltage Power Receiving Equipment Regulations” issued by the NEC Association on September 20, 2002, p. 320 “Interpretation Guidelines for Operational Notification of the Chief Engineer System (Excerpt)”

To measure the insulation resistance of an AC circuit or AC electrical equipment using the DC insulation resistance meter method, remove the grounding wire for the transformer and open the switch for each circuit that can be disconnected for the other circuits. There is a problem that it cannot be measured unless it is isolated and separated for each equipment to be measured or insulation group to be measured, and as a result, it is necessary to measure power outage and current power that is difficult to power outage such as IT related There is a problem that it does not match the load situation.
In addition, since the insulation resistance measurement is individually performed on the electrical circuit and electrical equipment in the state where the electrical circuit is separated and the mutual relations are cut off, measurement leakage is likely to occur, and many man-hours are required.

  The DC type insulation monitoring device used for ungrounded distribution type AC electrical equipment is in principle the same as the DC type insulation resistance meter method, and is used in the electric circuit including the load of the same transformer feeder system. Detects and alerts wherever an insulation breakdown accident occurs without distinction. However, in order to find the point of insulation failure, it is not possible to perform measurement separately unless the insulation group of the suspicious electrical equipment is separated. There is a problem that it is not possible to search for the point of insulation deterioration at the wire.

  The Igr insulation measurement voltage applied via the ground wire between the monitored electrical circuit and the ground used by the Igr insulation state monitoring device used in the AC electrical equipment of the direct ground distribution system avoids the influence on the load equipment and the like. Therefore, it is necessary to make the force as small as possible. The alternative measurement current signal that can be used for insulation detection is a very small current of several tens of microamperes, and a sufficient signal-to-noise ratio can be obtained for noise current generated by semiconductor power devices. There is a problem that a stable measurement value may not be obtained.

In addition, semiconductor power devices that are frequently used recently generate noise in a wide range of frequencies ranging from several tens of Hz to several hundreds of kHz due to interference between the reference frequency and its harmonics, and these components coincide with the frequency of the Igr insulation measurement voltage. Alternatively, there is a problem that, when approximated, an interference error occurs, and an error that an insulation state measurement value increases or decreases occurs.

  Since the Igr system insulation state monitoring device is a wattmeter method that uses alternating current as an alternative signal voltage for measurement, if there is a loss resistance in series with the capacitance of the insulation portion, a parallel equivalent equivalent resistance corresponding to the power consumption due to this loss resistance exists. There is a serious problem that the effective current corresponding to the value is added to the measured value of the effective current representing the insulation state as the error current.

  The error due to the interference disturbance and the error due to the series loss resistance are collectively referred to as an Igr principle error hereinafter.

In order to reduce the influence of the loss resistance that enters in series, it is necessary to lower the frequency of the Igr insulation measurement voltage. However, as the frequency decreases, the superposition transformer for applying an electromotive force to the ground line becomes larger and is not practical. There is no problem.

In the method of applying the Igr insulation measurement voltage to the earth resistance interposed between the class B ground electrode and the class D ground electrode and using the voltage drop, the earth resistance between the insulation deterioration points and the earth between each earth electrode are used. There is a problem that the resistance distribution cannot be used because the resistance distribution is not fixed.

The present invention is intended to solve these problems.

  Between the electrical equipment of both sides of the insulation part to be measured for insulation of the AC electrical equipment to be measured, for example, between the transformer low voltage side electrical equipment including the load equipment and the ground side electrical equipment such as Class B grounding or Class D grounding, etc. The conductor connecting the two is connected to the capacitor in an alternating manner and is cut off in a direct current, thereby enabling measurement of the hot-wire insulation resistance by the direct current method and detecting the Igr method insulation state at an extremely low frequency complementary to this. The most important feature is that the method can be used.

  Between the measurement terminals of the insulation measuring apparatus of the present invention, the conductor connecting the two electrical facilities sandwiching the insulation part to be measured for insulation of the alternating current electrical equipment to be measured is replaced with an alternating current and cut off in a direct current manner. Provide a capacitor with performance. This capacitor can be detachably mounted via a connecting means, or can be placed as an independent device at a point in the AC electrical equipment to be measured. Of course, this capacitor can be used as long as the existing equipment is replaced by a capacitor or grounded.

  A direct current type insulation resistance measuring means capable of measuring the insulation resistance of the insulation portion between the two electrical equipments from between the insulation resistance of the capacitor and the measurement terminal as needed is provided.

  Further, a low-frequency AC power supply means is provided that can apply an Igr insulation measurement voltage having a frequency lower than the commercial frequency from between the measurement terminals to the insulation portion between the two electrical facilities.

  There is provided an Igr type insulation state detecting means for extracting an effective current from the Igr insulation measurement voltage applied to the insulation portion and the current flowing through the insulation portion and measuring the insulation state based on the extracted current. This Igr type insulation state detecting means can be detachably mounted on the present invention and can be used as a portable type, or can be installed as an independent device at a key point such as a branch circuit of an AC electrical equipment to be measured. You can also

  Capacitor current measuring means is provided for measuring the current flowing through the capacitor by the measurement voltage and judging whether the capacitor is good or bad.

  Further, a DC ground voltage / insulation drop measuring means for measuring an insulation failure of a DC machine that becomes an obstacle to the DC system insulation resistance measuring means can be provided. That is, after measuring and recording the DC voltage generated between the measuring terminals in a state where the AC replacement by the capacitor is completed, a predetermined resistance is connected to measure the voltage drop, and the DC insulation resistance is determined based on these measurement results. A method such as calculation can be applied.

It can be used by connecting this device to a power distribution system without a conductor that connects the two electrical facilities, such as a non-grounding system, through a current-carrying element.

The operation of the present invention configured as described above will be described.
In use, the measurement terminal of the present apparatus is connected to the terminals of both electrical equipments that sandwich the insulation part to be measured for insulation of the AC electrical equipment to be measured. For example, if a measurement relay terminal or both ends of a switch are used, work can be performed efficiently. After the connection, the conductors that connect the two electrical facilities, such as measurement relay terminals and switches, are released.
As a result, the conductor of the circuit to be measured is replaced with the capacitor in an AC manner, and the AC current flowing between the two electrical facilities flows to the capacitor through the measurement terminal of the apparatus, so that the AC electrical facility to be measured is blacked out. You can continue to drive without having to.

  Insulation resistance measurement by DC, DC measurement voltage is applied between both electrical equipments from the measurement terminal, and the current that flows constantly is measured except for the transient current value that charges the capacitance. This is done by calculating the insulation resistance from the direct current voltage. In addition, since the measured voltage is a known constant voltage, there is also a method in which the resistance value is scaled with the numerical value of the resistance designed and calculated in advance based on the measured voltage to which the scale of the indicating instrument is applied, and the resistance value is directly read. It is also possible to provide an alarm setting function and output an electrical signal as insulation resistance information.

Using this DC type insulation resistance measuring means, the insulation performance of the capacitor can also be confirmed at any time.

For AC noise, the accuracy of insulation measurement can be improved by removing electrical fluctuation components using an amplitude limiter and low-pass filter suitable for the application inside the DC insulation resistance measurement means. Can be increased.

Since the capacitor connecting the measurement terminals passes the operating current of the AC electrical equipment to be measured and reliability is important, it is important to check maintenance of the insulation resistance and capacitance of the capacitor.
When a low frequency voltage is applied to the capacitor from the low frequency AC power supply means, a current corresponding to the capacitance flows through the capacitor. The capacitor current measuring means measures this current, compares the current value with the design current value, and determines whether the capacitor is good or bad. For measuring the capacitor current, it is possible to take means for measuring the correct current with reference to the voltage phase supplied from the low-frequency AC power supply means.

  The voltage applied to the capacitor is also supplied from the measuring terminal to both electrical equipments sandwiching the insulation part of the AC equipment to be measured, and this can be used as an Igr insulation measurement voltage to enable insulation state measurement by the Igr system insulation state detection means. To do.

  That is, the Igr type insulation state detection means detects the Igr insulation measurement voltage applied across the insulation portion to be measured for insulation and the leakage current flowing through the insulation portion by this voltage, and the voltage and the power factor of the current are detected. The equivalent resistance value of the insulating portion is measured by performing an operation, etc., extracting the effective current component and dividing the applied voltage. The effective current Igr as an indication of the insulation state is output after being converted into a value obtained by dividing the resistance value by the voltage of the electric circuit used in the electrical equipment constituting the insulation part.

  As a means for detecting the leakage current, a current transformer, a zero-phase current transformer, or the like can be used. By using a split iron core type, a branch electric circuit or a load wiring cable is sandwiched between the live lines. Thus, movement measurement is possible, and exploration and identification can be rationally performed by a method of driving down the insulation lowering accident point while repeatedly measuring the Igr current at the important point toward the downstream of the electric circuit.

  As an alternative to the conductor that connects the two electrical equipments that sandwich the insulation part, the reactance of the capacitor that cuts the measurement terminals in a direct current and shorts in an alternating current is inversely proportional to the frequency of the applied voltage. Therefore, a capacitor with a small reactance that is negligible in view of the frequency of the AC electrical equipment to be measured shows a large value corresponding to the ratio of both frequencies for the low frequency supplied from the low-frequency AC power supply means. It will be. Therefore, the use of a low frequency voltage can save power required for determining the quality of the capacitor from the current value.

  In addition, when this low frequency voltage is used as an Igr insulation measurement voltage by adding the voltage between the two electrical equipments to the insulation part to be measured, a predetermined voltage can be obtained with a small amount of power for the same reason. There is an effect that it is possible to greatly improve the economic efficiency when performing constant monitoring.

  Furthermore, as the frequency of the Igr insulation measurement voltage decreases, the power of the low-pass filter for removing noise increases because the power is weakened by moving away from the noise frequency region emitted from the semiconductor power device or the like. The effect of being less susceptible to AC noise is also great.

  The parallel conversion value error of the loss resistance that enters in series equivalent to the capacitance of the insulation portion to be measured is not detected in the DC insulation resistance measurement.

  However, the error due to the parallel conversion value has an effect in proportion to the square of the frequency used by the Igr insulation measurement voltage in the Igr method, so that the equivalent parallel conversion resistance value increases as the frequency of the Igr insulation measurement voltage is lowered. That is, there is a great effect that the equivalent effective current value is reduced and the added current error is reduced.

FIG. 7 is an explanatory diagram regarding a parallel conversion error of a loss resistor entering in series. In the figure, C _S is the capacitance of the insulated circuit, and R _S is a loss resistance in series with this capacitance. C _P and R _P are equivalent capacitance values and equivalent resistance values when C _S and R _S in series are equivalently converted in parallel, and the conversion formula is as follows.

From this equation, it can be seen that the parallel conversion resistance value increases as the frequency decreases, that is, the effective current that causes an apparent error decreases.
Assuming that a capacitance of 30 μF and a loss resistance of 100Ω exist between the measurement terminals of the AC equipment to be measured, the equivalent parallel equivalent resistance value is calculated by changing the frequency of the Igr insulation measurement voltage, 20 Hz, 0.8 kΩ / 10 Hz 2.9 kΩ / 1 Hz, 281.8 kΩ, and it is clear that the lower the operating frequency, the higher the equivalent parallel conversion resistance value and the less the influence of the series loss resistance.

  In a load circuit such as a branch circuit with a direct ground distribution system, this device is interrupted for each phase line between the power supply side such as a switch in the middle of the circuit and the load side, and measurement is performed by using a mutual connection method. To do.

  In the case of DC insulation resistance measurement, the device is divided and connected to each phase so that an AC load current flows to the measurement terminal of the device, and one DC insulation resistance measurement means is operated. The load side insulation resistance can be measured from the connection point.

  Also, when using the Igr system insulation state detection means, this apparatus is interrupted and connected to each phase line, and only the low-frequency AC power supply means is in an all-phase operation state and synchronously tuned to each other. By operating a plurality of the devices as if they were one unit, the same Igr insulation measurement voltage can be applied and superimposed between each phase on the load side electric circuit and the ground, and the use of the Igr insulation state detection means 8 is possible. To do.

  Complementary combination of DC method insulation resistance measurement and low frequency Igr method insulation state measurement by replacing the conductor connecting between the two electrical facilities sandwiching the insulation part to be measured for AC electrical equipment to be measured with a capacitor In general, DC insulation resistance measurement that enables high-accuracy measurement enables wide-area insulation measurements such as transformers and substations in a wide area. However, because it is possible to use a split current transformer, it is possible to move and measure, using the low-frequency Igr method insulation state detection device to identify the point of insulation degradation from the transformer to the end load without power failure The usage method to do is now possible.

  Further, in the measurement of the insulation state of the Igr method, when the effective component current indicating the lowered state of insulation increases, it may be attributed to a current error due to a cause different from the DC insulation resistance generated due to the characteristics of the Igr method, that is, an Igr principle error. If there is any doubt about the presence or absence of this, it can be confirmed at any time by the DC insulation resistance measurement method, so that unnecessary exploration work as in the prior art is eliminated and the insulation maintenance efficiency can be improved.

Compared to the Igr method, the insulation resistance measurement method using DC voltage can be easily obtained with high accuracy without being affected by loss resistance and noise in series with the capacitor. It has become possible to monitor insulation resistance collectively for a wide range of insulation groups such as batch monitoring and batch insulation monitoring of substations with multiple transformers.
In other words, by interrupting this device to the conductors connecting the Class B grounding electrode and each transformer in the substation, it is possible to measure and monitor the insulation of a large number of transformers sharing the grounding electrode in a lump. Insulation machine monitoring is possible with a small capital investment.

  As for the exploration of the point of insulation degradation accident that is performed by live line without power failure of the electric equipment, the effect is conventionally expected but the use is limited to the non-grounded system because there is no appropriate method for superimposing the Igr insulation measurement voltage. In addition, an extremely low frequency Igr type insulation state detecting means can be used by replacing the conductor with a capacitor.

  When the DC system insulation resistance detection means detects an insulation drop accident alarm, switch to the Igr system insulation state detection means, and each transformer in the substation and each transformer load circuit in the collective monitoring range sharing the class B ground electrode Measure the effective current at each hierarchical branch of the load facility, and conduct a rational exploration that inevitably reaches the downstream of the electric circuit while identifying the defective branch, and inevitably reaches the insulation breakdown accident point. It became possible.

In addition, it has become possible to measure insulation resistance and insulation state of computer systems, communication systems, etc., without causing a power outage in branch circuits.

  In the high-voltage ungrounded distribution system, if this device is applied by interrupting the grounding wire of a grounded instrument transformer, the insulation insulation resistance measurement and the branch cable should be investigated to identify the location of the insulation degradation accident. Is also possible.

In addition, if a measurement relay terminal is provided on the ground wire of the shield of the high voltage cable and this device is applied by interrupting the measurement relay terminal, it is easy to measure the ground insulation resistance of the cable shield.

Two different types of insulation measurement methods, the DC method insulation resistance measurement method and the Igr insulation state detection method at a low frequency, are provided side by side, and they are complemented to each other and used efficiently to provide a cheap and highly reliable hot-wire insulation monitor. The method has been established and the system efficiency of insulation maintenance has been improved.

Capacitor performance is important because the AC current flowing through the conductor connecting the two electrical facilities sandwiching the insulation section of the AC electrical equipment to be measured is transferred from the measurement terminal of this device to the capacitor that replaces the conductor. It becomes. In the present invention, the insulation resistance and capacitance of the capacitor can be confirmed, and the low frequency low frequency power provided for confirming the capacitance of the capacitor is also applied to the insulation portion of the AC electrical equipment to be measured. By supplying an Igr insulation measurement voltage, it is possible to use a low frequency Igr insulation state detection means, and a highly reliable insulation lowering fault point identification work by the Igr method is facilitated.

FIG. 1 is an electric circuit diagram showing the configuration of the apparatus and the AC electrical equipment to be measured, which is an embodiment of the interrupt type insulation measuring apparatus (insulation resistance / insulation state detecting apparatus) according to the present invention.
In FIG. 1, 1 and 2 are measurement terminals for connecting the electrical equipment to be measured, 3 is a DC insulation resistance measuring means, and 4 is an insulation subject to insulation measurement of the AC electrical equipment to be measured connected between the measurement terminals. Capacitors 41 and 42 are means for safely passing an alternating current flowing between both electrical equipments sandwiching the portion, means for connecting the capacitors, 5 is a means for supplying low-frequency alternating current power, and 6 is a current transformer for detecting capacitor current ( CT) 61 is a connecting means for using a capacitor of existing equipment, and 7 is a capacitor current measuring means for measuring the current detected by 6 and monitoring the capacitance.
Reference numeral 8 denotes an Igr system insulation state detection means. 9 is a switch for connecting the capacitor 4 and the like to the circuit to be measured, 10 is a switch for supplying low frequency AC power, and 11 is a switch for connecting DC insulation resistance measuring means.

Reference numeral 100 in FIG. 1 is a single-wire electric circuit diagram showing an example of an AC electrical equipment to be measured for measuring an insulation resistance or an insulation state in this embodiment.
102 is a relay terminal for measuring electrical equipment on the transformer circuit side, 101 transformer low-voltage circuit ground wire, 100 single-phase three-wire power distribution transformer, 106, 107, 108 branch-circuit from the low-voltage side, etc. Consists of.
104 is a relay terminal for measurement of the grounding electrode side electrical equipment, and is composed of a grounding resistor for ground resistance R2, 109, 111D classing grounding generated between the 105B type grounding electrode, the 110B type grounding electrode and the D type grounding electrode, and the like. .
Reference numeral 103 denotes a short-circuit piece between the measurement relay terminals.

Reference numeral 200 in FIG. 1 indicates a circuit constant constituting an insulating portion of the AC electrical equipment to be measured. 201 is an insulation resistance R1 existing between the distribution line of the branch 108 and the ground, 202 is a pure capacitance C1 among a floating capacitance existing between the distribution line and the ground, a filter capacitor such as a semiconductor power device, Reference numeral 203 denotes an electrostatic capacity Cs having a loss in the electrostatic capacity or the filter capacitor, and reference numeral 204 denotes a loss resistance Rs equivalently present in series with the capacitor or the capacitor circuit.

The usage and operation of the configuration of FIG. 1 will be described.
The switches 9, 10, 11 of this device are open and perform connection work for measurement. When measuring the insulation of the AC electrical equipment to be measured while in use, the electrical circuit between the two electrical equipments sandwiching the insulation part to be insulated, that is, from the ground wire 101 to the branch circuit 106 and the like through the transformer 100 The terminal electrode 102 of the electric circuit side electric equipment constituted by the electric circuit side equipment, the terminal electrode 104 of the ground side electric equipment constituted by the B type grounding electrode 105, the resistance between the earthing electrodes 110, the D type grounding electrode 109, etc. Connect measuring terminals 1 and 2.

  In order to perform the capacitance measurement diagnosis of the capacitor, the switch 10 of the low frequency AC power supply means is closed. If a low-frequency AC voltage is applied to the capacitor 4 and the capacitor is normal, a current corresponding to the capacitor capacity design value flows. The capacitor current is detected by the current transformer 6, and the capacitor current measuring means 7 determines whether the numerical value is within the design range. In order to accurately measure the capacitor current, the signal from the low-frequency AC power supply means may be used for discrimination. After the measurement is completed, the switch 10 is opened.

In order to perform the insulation resistance diagnosis of the capacitor, the switch 11 of the DC insulation resistance measuring means 3 is closed. A DC voltage for measuring the insulation resistance is applied to the capacitor 4 and charged over a time corresponding to the capacitor capacity design value. After the completion of charging, if the measured value of the insulation resistance measuring means obtained steadily is equal to or less than the preset design value, the switch 11 is opened and the capacitor is discharged as necessary.

As a measurement preparation, the capacitor connecting switch 9 is closed. Since the capacitor 4 is connected, the measuring terminals 1 and 2 are short-circuited in an alternating manner. Next, when the short circuit piece 103 of the AC electrical equipment to be measured is removed and opened, the AC load current (the ground line current in this embodiment) flowing through the short circuit piece 103 flows to the capacitor 4 and the circuit of the AC electrical equipment to be measured. A capacitor is substituted for the short-circuit piece 3 as a conductor, and an insulation measurement standby state is set.

  The switch 11 is closed in order to perform the DC method insulation resistance measurement. Then, the DC voltage for measurement sent out by the DC insulation resistance detecting means charges the capacitor 4 of the present apparatus and also charges the capacitances 202 and 203 existing in the insulating portion of the AC electric equipment to be measured. DC insulation measurement of electric circuits with a large capacitance is often performed for diagnosis of high-voltage cables and capacitors, and there is no problem in measurement technology. When the charging to the electrostatic capacitance is completed, only a constant current flows through the insulation resistor R1 and a constant stable current value is obtained. Therefore, the DC current D (mA) and the applied measurement DC voltage E (V) are insulated. The resistance measuring means calculates and outputs an insulation resistance value K (Ω).

  The switch 10 is closed when measuring the Igr insulation state and continuously monitoring the capacitor capacity. Capacitor current measuring means 7 monitors the capacitance of the capacitor. At the same time, the voltage across the capacitor passes through measurement terminals 1 and 2 and terminals 102 and 104 of the AC electric equipment to be measured, and the transformer electric circuit side electric equipment and the ground electrode. Join between side electrical equipment. This voltage is applied to 201 (R 1), 202 (C 1), 203 (Cs), 204 (Rs), etc. that constitute the insulating parts of both electrical equipments, and a current due to the Igr insulation measurement voltage flows and the Igr insulation state The insulation state can be measured by the detection means 8.

  The operation of the Igr type insulation state detection means 8 is similar to that of a highly sensitive wattmeter. 81 and 82 are voltage signal input terminals used for power factor calculation. The input terminal 81 is connected to the transformer ground line 101, and the input terminal 82 is connected to the D-type grounding work. From this time, the Igr insulation measurement voltage Vg applied to the insulating portion is obtained. In addition, the current signal Ig flowing in the insulating portion is obtained from the zero-phase current transformer 85 installed in the transformer ground line 101 or the branch circuit 108, and the power factor is calculated between the voltage Vg and the current Ig for insulation. The effective current component included in the current flowing through the impedance is extracted, multiplied by the ratio of the Igr insulation measurement voltage and the settling voltage (ground voltage of the circuit used), and converted to the current flowing through the circuit voltage, and the Igr measurement current value Displayed as G (mA). When this numerical value exceeds the alarm set value, an alarm for insulation state deterioration is issued.

  There is a problem that the current due to the Igr principle error is added to the effective component current detected by the Igr method, that is, the Igr current value as an error in addition to the effective component current flowing through the insulation resistance. This has been improved to ensure measurement reliability, and the Igr insulation state measuring means can be used to identify the location where the insulation drop has occurred.

  When there is a doubt about the detected Igr current value, it is easy to perform comparison and verification by measuring with the DC-type insulation resistance measuring means provided therewith.

  When there is no error between the Igr current, G (mA), which represents the insulation state, and the DC insulation resistance measurement value K (kΩ), the following equation holds:

  When the deviation between the insulation state measurement result and the DC measurement value is large, the Igr current error is suspected to be involved in the Igr current, but it is generally estimated that the DC measurement value is more correct. Reflecting this result, it is possible to improve the reliability of insulation measurement by adjusting the measurement range of the monitored insulation group, such as changing the alarm management value and adding the attachment point of the detection zero-phase current transformer. It became possible to take appropriate measures.

FIG. 2 is a double-line diagram for explaining the connection when measuring the load side ground insulation by interrupting and connecting this device to the intermediate switch 307 of the single-phase two-wire distribution line that is a branch circuit from the single-phase three-wire transformer. Reference numeral 300 indicates a load circuit of the branch circuit 108. This figure is an example of a usage method in the case of searching for a circuit to be measured such as a semiconductor power device or an electronic device that is difficult to be interrupted, and an insulation failure portion such as the devices 301, 302, and 303.
According to this, it becomes possible to detect the deterioration of the insulation of the circuit to be measured and the equipment including important electronic equipment and the like at an early stage, and to prevent important matters in a predictive manner.
These devices usually use many switching power semiconductor elements and generate a lot of AC broadband noise. In many cases, this noise countermeasure includes a filter including a large amount of capacitors and the like, and it has been difficult to determine whether the insulation is good or bad due to an Igr principle error in the conventional Igr type insulation state detector. In the present invention, since the Igr method with a very low frequency can be used, highly reliable measurement is possible. However, depending on the characteristics of the electric circuit, there may be doubts about the measurement results, and DC-type insulation resistance measurement may be required.

In FIG. 2, the apparatus of the present invention is used for two sets, both on the n-phase 310 side and the w-phase 311 side of the distribution line, and each low-frequency AC power supply means is connected by a synchronous matching drive circuit. Driven by the same frequency, the same phase, and the same voltage. Therefore, across the switch 307, the same Igr insulation measurement voltage is applied between both the n-phase 310 and the n-phase 310a and between the w-phase 311 and the w-phase 311a, and the voltages applied to the load between the two electric lines are canceled out. There is no influence of the measured Igr insulation voltage on the commercial frequency voltage between the load side lines because it becomes zero. Since the n-phase 310 and the w-phase 311 are connected to the ground by the B-type grounding work via the transformer winding line, the D-type grounding work connected to the earth from the switch 307 to the electric circuit and the B-type grounding 105 on the load side, etc. An Igr insulation measurement voltage is applied to 109, and the Igr insulation state detection means 8 can be used by utilizing this.

  In the measurement preparation, the switches 9n, 9w, 308, and 309 are closed, and the branch circuit switch 307 is opened. When measuring the insulation state with the Igr type insulation state detection means 8, the connection switches 10n and 10w of both low-frequency AC power supply means are closed, and 11n and 11w are opened. Next, the input terminal lead 81 for insulation detection is connected to the n-phase 310a, and the input terminal lead 82 is connected to the D-type grounding 109 or the like to obtain an Igr insulation measurement voltage. The ground insulation state of the circuit to be measured 301 or the like can be measured by passing two wires of the power supply line connected to the switch 304 or the switches 305 and 306 to the zero-phase current transformer 85.

  When performing DC system insulation resistance measurement, the switches 10n and 10w and 11w of both low-frequency AC power supply means are opened, while only the switch 11n of the DC side insulation resistance measurement means on the n side is closed. To do. After charging the capacitors 4n and 4w and the ground capacitance 202 of the insulating part, the ground insulation resistance 201 and the like of the load side electric circuit can be measured from the switch 307 by the DC type insulation resistance measuring means 3n.

  This measurement point can be moved for each branch switch, and the insulation lowering device can be identified by the same method.

FIG. 3 shows an example of the use of insulation measurement in an ungrounded high-voltage distribution system. Reference numeral 600 denotes a high-voltage distribution path. Reference numeral 600 is an extra high voltage receiving transformer, 601 is an EVT load switch, and 602, 603, and 604 are high voltage branch line breakers.
Reference numeral 605 denotes a grounding-type instrument transformer EVT, 606 a neutral point grounding wire thereof, 607 and 609 a relay terminal for measuring the grounding wire, and 608 a short-circuiting piece thereof. After connecting the measurement terminals 1 and 2 of this device to 607 and 609 and confirming according to the measurement procedure of this device, the short circuit piece 608 is opened to interrupt the grounding circuit of the high voltage system and insulation measurement is performed. It becomes possible.
That is, in the previous procedure, the switches 9 and 11 are opened, 10 is closed, and the capacitance value of the measuring terminal short-circuit capacitor 4 is confirmed. Next, with the switches 9 and 10 open, 11 is closed, and the insulation resistance value of the short-circuit capacitor 4 between measurement terminals is confirmed. After confirmation, the switch 9 is closed and the grounding relay terminal shorting piece 608 is opened.

The DC insulation resistance for the entire system is such that the switch 10 is opened while the switch 9 is closed, the switch 11 is closed, and charging of the capacitor 4 and the electrostatic capacity 250 (Cx) of the entire system is completed. It can be obtained by a DC type insulation resistance measuring means from a DC leakage current that flows constantly.

Insulation state of the system or the high voltage branch line and its load equipment, etc., can be obtained by opening the switch 11 with the switch 9 closed and closing the low frequency AC power supply means 10 so that the Igr insulation measurement voltage is Measurement is performed by the Igr system insulation state detecting means 8 in addition to all the charging circuit and ground in the system. The Igr insulation state detection means 8 arbitrarily selects and measures the position of the current detection ZCT85, advances the measurement hierarchically downstream of branches having a large Igr current, narrows down the insulation group to be measured, and insulates It becomes possible to reasonably search and identify the state defect location 251 (Rx) and the like.

Further, the ZCT 85 and the Igr type insulation state detection means 8 can be a fixed installation type permanent device.

In addition, if this device is interrupted and connected to the relay terminals 613 and 615 provided on the shield ground line 612 of the shielded power cable, it is easy to measure the insulation resistance between the shield and the ground of the high-voltage power cable that is likely to cause water trees. .

FIG. 4 shows an example in which the interrupt insulation resistance / insulation state monitoring apparatus according to the present invention is implemented together with related technologies.
1 and 2 are measurement terminals, 81 is an input terminal for the Igr insulation measurement voltage of the Igr system insulation state detecting means 8 worn in the present invention, 83 is a terminal for connecting the signal ground line 82, and the electrical equipment to be measured shown in FIG. Connected to the D-type grounding work via the terminal 111. 20 is a measurement connection terminal when applying this apparatus to a low-voltage ungrounded distribution type AC electrical facility, and a closing element Z1 is connected to it, and insulation measurement is possible by connecting this to one point of the ungrounded distribution line. become. When used in a non-grounded distribution system, by connecting the input terminal of the Igr insulation measurement voltage to 84, it is possible to take in the voltage between the electrical facilities of both of the insulated portions of the non-grounded distribution path.

In FIG. 4, the Igr system insulation state detection means 8 which has been shown as an example of use inside the monitored electrical equipment in the first embodiment is detachably mounted in the apparatus. This is because only the Igr system insulation state detection means 8 is removed and used as a portable type, and it can be used to move to specify the insulation lowering accident point of the electric equipment to be measured and used at any measurement point.
Further, the Igr insulation state detection means 8 can be installed in any number of places as required such as a branch of a transformer low-voltage load circuit or a load facility as a stationary type. In the present embodiment, the ground wire 82 of the Igr insulation state detecting means 8 is connected to the D-type ground electrode ED of the monitored electrical equipment because the ground interposed between the B-type ground electrode and the D-type ground electrode. This is to eliminate the influence of the equivalent parallel resistance caused by the series loss resistance effect caused by the resistor 110 (R2).

Reference numeral 19 denotes an auxiliary switch used when the apparatus is stopped.
14 is a semiconductor relay for short-circuiting the measurement terminal, 12 is an electromagnetic contactor for short-circuiting the measurement terminal, and these are any of the capacitor current measurement means 7, the overvoltage detection means 13, the overcurrent detection means 21, etc. during the insulation measurement. When a measurement problem is detected, the measurement terminals are short-circuited in order to prevent the influence on the present apparatus and the AC electric equipment to be measured and to ensure safety. The semiconductor relay 14 operates in real time with the phenomenon, and at the same time, the electromagnetic contactor 12 operates instantaneously, and the measurement terminals 1 and 2 are closed by a cooperative operation.

  16 is for measuring the DC machine insulation deterioration of the AC electrical equipment to be measured by the DC ground voltage / insulation resistance measuring means. When insulation of a circuit with a DC power supply in the load electrical equipment to be measured occurs, a DC ground voltage is generated between the terminals of the capacitor 4 to give an error to the DC system insulation resistance measuring means of this device. There is a risk of damage to the equipment. Reference numeral 16 denotes a measuring means provided when a failure due to these DC machines is expected. The usage method is to record the voltage VD1 when the measured DC voltage exceeds a set value when measuring the DC ground voltage with the switches 10, 11, 17, 19 open and the switches 9 and 15 closed. After that, the switch 17 is closed, the R3 DC machine insulation measuring resistor 18 is inserted, the influence of the voltage drop due to the DC machine ground fault resistance RD of the AC electric equipment to be measured is measured, and this voltage is recorded as VD2. From the resistance value DΩ of the resistor 18 and VD1, VD2, the DC machine insulation resistance RD is calculated by the following equation.

  This resistor is also used for discharging the charge of the electrostatic capacitance of the capacitor 4 and the measured electrical equipment system at the end of measurement.

  In some cases, the capacitor 4 has a redundant design of two or more as shown in FIG.

Reference numeral 50 denotes an overall control unit that processes the above-described measurement operation according to a phenomenon according to a preprogrammed procedure, 51 is an overall operation unit thereof, 52 is also a display unit, and 53 is an output device for data and alarms. is there.

Of course, it is also easy to measure the insulation by operating this device by manual operation.

  Centralized measurement such as transformers and substation collective insulation measurement of low-voltage direct ground distribution system and ungrounded distribution system, joint insulation measurement of transformers and branch distribution lines of high-voltage ungrounded distribution system, and identification of exploration of insulation drop accident point The establishment of the method has rationalized insulation maintenance and can be widely applied to hot-line maintenance of power usage facilities.

It is an example of the configuration of the present invention and a low voltage AC electric circuit ground line measurement single line diagram. It is an example of the configuration of the present invention and a low voltage AC electric circuit interrupt measurement return line diagram. It is an example of the configuration of the present invention and a high voltage non-grounded AC electric circuit ground line measurement single line diagram. It is a block diagram of the interruption insulation measuring device including a related incidental technique by the structure of this invention. It is a block diagram of a direct current type insulation resistance monitoring device in the prior art. It is a block diagram of the basic Igr system insulation state monitoring apparatus in the prior art. It is explanatory drawing of parallel conversion of a series loss resistance.

Explanation of symbols

1, 2, Measuring terminal 3, DC type insulation resistance measuring means
4. Capacitor C that replaces the desired measuring point conductor of the AC electrical equipment to be measured
41, 42 Capacitor connection means 5, Low frequency AC power supply means 6, Capacitor current detection current transformer CT
61, connection means of current transformer for detecting capacitor current 7, capacitor current measuring means 8, Igr method insulation state detecting means 81, 82, 83 Igr insulation measurement voltage input terminal 84, Igr insulation measurement voltage connected to ungrounded distribution system Input terminal 85 Zero-phase current transformer ZCT1
9, Switch / capacitor circuit connection 10, Switch / low frequency AC power 11, Switch / DC type insulation resistance measurement 12, Magnetic contactor / Emergency short circuit 13, Overvoltage detection means 14, Semiconductor relay 15, Switch / DC earth voltage measurement 16, DC earth voltage / insulation degradation measuring device 17, Switch / DC earth voltage / insulation degradation measuring device 18, Resistor R3 / DC earth voltage / insulation degradation measuring device 19, Switch / input short circuit 20 , Non-grounded distribution circuit connection terminal 21, Overcurrent detection means 22, Current transformer / overcurrent detection 100, Transformer 101, Class B grounding wire 102, 104 Measurement relay terminal 103, Short-circuit piece 105, Class B grounding work Grounding poles 106, 107, 108 Branch circuit 109 of low-voltage circuit, Class D grounding work, etc. 110, Ground resistance R2 between Class B grounding and Class D grounding
111, D class grounding lead terminal 201, insulation resistance R1 of low voltage circuit
202, Ground capacitance C1 of the low-voltage circuit
203, capacitance Cs to ground of low-voltage circuit
204, Cs series loss resistance Rs
250, Ground capacitance Cx of high-voltage circuit
251 Ground insulation resistance Rx of high voltage circuit
301, 303, Circuits and equipment to be measured 304, 306, Branch switch 307, Branch circuit switch 308, 309 Insulation measuring device switch 310, 311 Phase line n, w of branch circuit
310a, 311a branch circuit switch load side phase line 600, extra high / high voltage transformer 601, branch circuit load switch 602, to 604 branch circuit breaker 605, instrument grounding transformer EVT
606, EVT neutral point grounding wire 607, 609 Measurement relay terminal 608, shorting piece 610, grounding pole for class A grounding work, etc. 611, cable head for high voltage cable 612, ground wire for high voltage cable shield 613, 615 shield grounding Measurement relay terminal 614, short-circuit piece 616, cable head of high-voltage cable 617, high-voltage / low-voltage transformer 618, load switch

Claims (6)

  The conductor connecting the two electrical equipments that sandwich the insulation part to be measured is replaced with a capacitor by alternating current with a capacitor, and an alternating voltage with a frequency lower than the commercial frequency is applied between the two electrical devices. The voltage superimposition method of the Igr insulation state detection apparatus to apply.   The conductor connecting the two electrical equipments that sandwich the insulation part to be insulated is replaced with a capacitor by alternating current, and the insulation resistance is measured by applying direct current between the two electrical devices. DC insulation resistance measurement method.   In a DC insulation resistance measuring device that measures insulation resistance by applying a direct current between both electrical equipments that sandwich an insulation part to be subject to insulation measurement, an Igr insulation measurement voltage having a frequency lower than the commercial frequency is applied between the electrical equipments. An insulation monitoring device comprising low-frequency AC power supply means that can be applied.   Capacitor for disconnecting in a direct current instead of an alternating current for the conductors connecting the two electrical facilities sandwiching the insulation part to be measured for insulation, or a connecting means for the capacitor, and a direct current between the two electrical facilities DC-type insulation resistance measuring means capable of measuring insulation resistance, low-frequency AC power supply means for providing an Igr insulation measurement voltage having a frequency lower than the commercial frequency between the two electrical facilities, and a current flowing through the capacitor by the measurement voltage An insulation measuring device comprising: a capacitor current measuring means for measuring.   Capacitor for disconnecting in a direct current instead of an alternating current for the conductors connecting the two electrical facilities sandwiching the insulation part to be measured for insulation, or a connecting means for the capacitor, and a direct current between the two electrical facilities DC-type insulation resistance measuring means capable of measuring insulation resistance, low-frequency AC power supply means capable of applying an Igr insulation measurement voltage having a frequency lower than the commercial frequency between the two electric facilities, and Igr detachably attached An insulation measurement apparatus comprising: a system insulation state detection means; and a capacitor current measurement means for measuring a current flowing through the capacitor by the measurement voltage. 6. The apparatus according to claim 3, 4 or 5, further comprising a DC ground voltage / insulation drop measuring means.