CN116256543B - System for shielding and measuring insulation resistance of 10kV cable - Google Patents
System for shielding and measuring insulation resistance of 10kV cable Download PDFInfo
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- CN116256543B CN116256543B CN202310539025.8A CN202310539025A CN116256543B CN 116256543 B CN116256543 B CN 116256543B CN 202310539025 A CN202310539025 A CN 202310539025A CN 116256543 B CN116256543 B CN 116256543B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/04—Housings; Supporting members; Arrangements of terminals
- G01R1/0408—Test fixtures or contact fields; Connectors or connecting adaptors; Test clips; Test sockets
- G01R1/0416—Connectors, terminals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/08—Measuring resistance by measuring both voltage and current
Abstract
The invention discloses a system for shielding and measuring insulation resistance of a 10kV cable, which relates to the technical field of cable insulation resistance measurement, and aims to realize simultaneous shielding of insulation resistance of two ends of a cable to ground by means of leading the end of the measured phase cable to the shielding end G end of a megohmmeter after a first metal wire is tightly clung to the outer surface of a second umbrella skirt at the measured end and leading the end of the measured phase cable to the shielding end G end of the megohmmeter after a second metal wire is clung to the outer surface of the second umbrella skirt at a first non-measured end.
Description
Technical Field
The invention relates to the technical field of cable insulation resistance measurement, in particular to a system for shielding and measuring 10kV cable insulation resistance.
Background
Insulating mediums are arranged between the high-voltage end of high-voltage equipment (such as a transformer, a circuit breaker, a transformer, a lightning arrester, a cable and the like) of the power system and the ground so as to ensure that enough insulating strength exists between the high-voltage end and the ground when the high-voltage equipment runs in an electrified mode, and an equivalent circuit of the insulating resistance inside the high-voltage equipment is shown in figure 6. As can be seen from fig. 6, when the operation voltage is applied between the device and the ground for a long period of time, the high voltage device effectively consumes powerPThe method comprises the following steps:when the internal insulation equivalent resistance R is large, the active power consumed inside the devicePThe heat generated in the device is small, and when the temperature of the device is raised to a low value, the device reaches heat balance, so that the device can safely and stably run for a long time. But when the device is damaged by moisture or insulation,Rwill reduce the active power consumed in operationPThe temperature of the equipment gradually rises along with the lengthening of the running time, and finally the equipment is burnt due to thermal collapse. The measurement of insulation resistance isThe measurement of the insulation resistance can check whether the insulation medium of the equipment body is damped or damaged, and the accurate measurement of the insulation resistance of the equipment has important significance for judging the health condition of the equipment.
The insulation resistance can be measured by using a megohmmeter, the measurement principle is shown in fig. 7, a direct current voltage U is output between an L end and an E end of the megohmmeter, the direct current voltage U is applied to two ends of tested equipment, the ammeter has an I current passing through the ammeter, and the insulation resistance can be calculated according to the voltage of the two ends of the tested equipment and the current flowing through the ammeter. In practice, however, the high voltage device has a bulk insulation resistance of the internal insulation mediumThe outer porcelain sleeve of the device also has a certain insulation resistance +.>Each umbrella skirt of the outer porcelain sleeve can be equivalent to a resistor r, and the insulation resistance of the outer porcelain sleeve is +>Can be equivalently composed of a plurality of resistors r connected in series, as shown in fig. 8, the measured insulation resistance is actually the body insulation resistance +.>Measured by insulation resistance of the outer porcelain sleeve>As shown in fig. 9, since the current flowing through the ammeter is the sum of the current flowing through the body insulation resistance and the current flowing through the outer porcelain bushing insulation resistance, the calculated insulation resistance is: />It can be seen that the ++is when the air is dry and there is no contamination on the outer porcelain sleeve surface>Is very large in valueBig, approach infinity, so +.>. However, when the air is moist or the surface of the outer porcelain sleeve is polluted, the air is added with the air>Lower value of +.>The measured result can not truly reflect the insulation condition of the body inside the equipment. In order to measure the internal insulation resistance of high-voltage equipment by using a megohmmeter when overtime or pollution exists on the surface of the outer porcelain sleeve>The megameter is provided with a shielding end G besides a high voltage end L and a grounding end E, the test principle is as shown in figure 10, the surface of an umbrella skirt 2 from the high voltage end is wound with a metal wire for one circle, and then the metal wire is led to the shielding end G of the megameter, which is equivalent to that the point A in a test circuit is connected with the shielding end G, and the megameter is started>The current of the circuit (A) returns to the negative electrode of the power supply after flowing through the point A and the point G of the shielding end, and does not flow through the ammeter, but only flows through +.>The insulation resistance measured by the megohmmeter is:. Thus, only the insulation resistance measured by the shielded megohmmeter is the insulation resistance of the interior of the body of the tested device real to the ground.
For high-voltage equipment such as transformers, circuit breakers, mutual inductors, lightning arresters and the like, the whole equipment is arranged at the same place, and the real insulation resistance of the body can be measured by shielding the resistance of the outer porcelain sleeve by adopting the shielding method, but the equipment connected with different places like a high-voltage cable is provided, and two ends of the cable are positioned at two different places, and the distance between the two ends of the cable is tens of meters to thousands of meters differentAs shown in fig. 11. The insulation resistance R of the cable per relative ground is equivalent to the insulation resistance of the cable conductive core to the cable outer sheath bodyAnd insulation resistance of two terminals of the cable to the cable outer sheath +.>And->As shown in FIG. 12, i.e. If the insulation resistance of the high-voltage cable is measured by the method for measuring the insulation resistance of the high-voltage equipment, the megohmmeter can only shield the insulation resistance of the A terminal when measuring the A terminal of the cable, and can not shield the insulation resistance of the B terminal because the A terminal and the B terminal are far apart, and the measured insulation resistance is->. The insulation resistance measurement for the B terminal is the same. Therefore, the existing measuring method for measuring the insulation resistance of the high-voltage equipment by the megameter cannot be directly applied to the insulation resistance measurement of the high-voltage cable, and cannot accurately measure the insulation resistance of the high-voltage cable body to the ground. Therefore, it is needed to provide a technical solution capable of accurately measuring the insulation resistance of the high-voltage cable body to the ground.
Disclosure of Invention
The invention provides a system for shielding and measuring insulation resistance of a 10kV cable, which is used for solving the technical problems that the existing measuring method for measuring insulation resistance of high-voltage equipment by a megameter cannot be directly applied to insulation resistance measurement of the high-voltage cable and cannot accurately measure insulation resistance of a high-voltage cable body to the ground.
In view of this, the present invention provides a system for shielding measurement of insulation resistance of a 10kV cable, comprising: megameter, cable under test, first metal wire and second metal wire;
the measured end of the measured cable is connected with the L end of the megohmmeter, one end of the first metal wire is tightly clung to the outer surface of the second umbrella skirt of the measured phase terminal and fixed round, the other end of the first metal wire is connected to the G end of the megohmmeter through the first non-measured end of the measured cable, and the second non-measured end of the measured cable is connected to the E end of the megohmmeter;
one end of the second metal wire is tightly fixed around the outer surface of the second umbrella skirt of the non-tested end tested phase terminal of the tested cable, and the other end of the second metal wire is connected with the first tested end of the non-tested end of the tested cable.
Optionally, the device further comprises a first 220V alternating current contactor, a second 220V alternating current contactor, a third 220V alternating current contactor, a first normally open contact button, a second normally open contact button, a third normally open contact button and a normally closed contact button;
the first 220V alternating current contactor, the second 220V alternating current contactor and the third 220V alternating current contactor are provided with seven groups of contacts, wherein the first, the second and the third groups of contacts are main normally open contacts, the fourth and the seventh groups of contacts are auxiliary normally open contacts, and the fifth and the sixth groups of contacts are auxiliary normally closed contacts;
one end of the normally closed contact button is connected with a 220V power supply, and the other end of the normally closed contact button is respectively connected with one ends of the first normally open contact button, the second normally open contact button and the third normally open contact button;
the other end of the first normally open contact button is sequentially connected with a fifth group of contacts of a second 220V alternating current contactor, a fifth group of contacts of a third 220V alternating current contactor and a first 220V alternating current contactor, the first 220V alternating current contactor is connected with a 220V power supply, and a fourth group of contacts of the first 220V alternating current contactor are connected with the first normally open contact button in parallel;
the other end of the second normally open contact button is sequentially connected with a fifth group of contacts of the first 220V alternating-current contactor, a sixth group of contacts of the third 220V alternating-current contactor and the second 220V alternating-current contactor, the second 220V alternating-current contactor is connected with a 220V power supply, and a fourth group of contacts of the second 220V alternating-current contactor are connected with the second normally open contact button in parallel;
the other end of the third normally open contact button is sequentially connected with a sixth group of contacts of the first 220V alternating current contactor, a sixth group of contacts of the second 220V alternating current contactor and a third 220V alternating current contactor, the third 220V alternating current contactor is connected with a 220V power supply, and a fourth group of contacts of the third 220V alternating current contactor are connected with the third normally open contact button in parallel;
the measured end measured phase terminal of the measured cable is connected to the L end of the megohmmeter through a first group of contacts of the first 220V alternating current contactor, a first group of contacts of the second 220V alternating current contactor and a first group of contacts of the third 220V alternating current contactor respectively, the measured end first non-measured phase of the measured cable is connected to the G end of the megohmmeter through a second group of contacts of the first 220V alternating current contactor, a second group of contacts of the second 220V alternating current contactor and a second group of contacts of the third 220V alternating current contactor respectively, and the measured end second non-measured phase of the measured cable is connected to the E end of the megohmmeter through a third group of contacts of the first 220V alternating current contactor, a third group of contacts of the second 220V alternating current contactor and a third group of contacts of the third 220V alternating current contactor respectively.
Optionally, the method further comprises: the first indicator light module, the second indicator light module and the third indicator light module;
the first indicator light module is connected in series with a seventh group of the first 220V alternating current contactor;
the second indicator light module is connected in series with a seventh group of the second 220V alternating current contactor;
the third indicator light module is connected in series with a seventh set of contacts of the third 220V ac contactor.
Optionally, the first indicator light module includes a first indicator light and a first voltage dividing resistor connected in series, the second indicator light module includes a second indicator light and a second voltage dividing resistor connected in series, and the third indicator light module includes a third indicator light and a third voltage dividing resistor connected in series.
From the technical scheme, the system for shielding and measuring the insulation resistance of the 10kV cable has the following advantages:
according to the system for shielding and measuring the insulation resistance of the 10kV cable, when the measured end of the measured cable is used for measuring the insulation resistance of each phase cable, the terminal end of the measured phase cable can be clung to the shielding end G end of the megohmmeter by the first metal wire after being clung to the outer surface of the second umbrella skirt for one circle, the terminal end of the measured phase cable can be clung to the shielding end G end of the megohmmeter by the second metal wire after being clung to the outer surface of the second umbrella skirt for one circle, the insulation resistance of the two ends of the cable to the ground is shielded, the measured data are real data of the insulation resistance of each phase conductive core to the ground, and the technical problems that the existing method for measuring the insulation resistance of the high-voltage equipment for measuring the megohmmeter cannot be directly suitable for insulation resistance measurement of the high-voltage cable and cannot accurately measure the insulation resistance of the high-voltage cable body to the ground are solved.
Drawings
For a clearer description of embodiments of the invention or of solutions according to the prior art, the figures which are used in the description of the embodiments or of the prior art will be briefly described, it being obvious that the figures in the description below are only some embodiments of the invention, from which, without the aid of inventive efforts, other relevant figures can be obtained for a person skilled in the art.
FIG. 1 is a schematic diagram of simultaneous shielding measurement of two cable side terminals of a system for shielding measurement of insulation resistance of a 10kV cable provided by the invention;
FIG. 2 is a schematic diagram of the wiring provided in the present invention for measuring the insulation resistance of the A phase of a 10kV cable by means of a B phase shielding terminal;
FIG. 3 is a schematic diagram of a control circuit of a system for shielding and measuring insulation resistance of a 10kV cable provided in the invention;
FIG. 4 is a schematic diagram of wiring for measuring the insulation resistance of the phase A of the 10kV cable by the system for shielding and measuring the insulation resistance of the 10kV cable provided by the invention;
FIG. 5 is a schematic diagram of a display circuit of a system for shielding a 10kV cable insulation resistance measurement provided in the present invention;
FIG. 6 is a schematic diagram of an equivalent circuit of the internal insulation resistance of the high voltage device;
FIG. 7 is a schematic diagram of an equivalent circuit for measuring insulation resistance of high voltage equipment;
FIG. 8 is a schematic diagram of an actual equivalent circuit of the insulation resistance of the high voltage device;
FIG. 9 is a schematic diagram of the actual measurement principle of the insulation resistance of the high-voltage equipment;
FIG. 10 is a schematic diagram of the measurement of insulation resistance using a shield end high voltage device;
FIG. 11 is a schematic diagram of two end structures of a cable;
fig. 12 is a schematic diagram of the equivalent insulation resistance of each phase cable to ground.
Detailed Description
In order to make the present invention better understood by those skilled in the art, the following description will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
For ease of understanding, referring to fig. 1-2, an embodiment of a system for shielding a 10kV cable insulation resistance measurement is provided in the present invention, comprising: megameter, cable under test, first metal wire and second metal wire;
the measured end of the measured cable is connected with the L end of the megohmmeter, one end of the first metal wire is tightly clung to the outer surface of the second umbrella skirt of the measured phase terminal and fixed round, the other end of the first metal wire is connected to the G end of the megohmmeter through the first non-measured end of the measured cable, and the second non-measured end of the measured cable is connected to the E end of the megohmmeter;
one end of the second metal wire is tightly fixed around the outer surface of the second umbrella skirt of the non-tested end tested phase terminal of the tested cable, and the other end of the second metal wire is connected with the first tested end of the non-tested end of the tested cable.
It should be noted that, in order to accurately measure the insulation resistance of the cable conductive core to the cable outer sheath body, the terminal ends on both sides of the cable must be shielded at the same time, and the measurement principle is shown in fig. 1. Because each 10kV cable consists of conductive cores of A phase, B phase and C phase, insulating mediums are filled between the phases and an outer sheath, when insulation resistance of each phase cable is measured at the measured end of the measured cable, namely the A end, the terminal end of the measured phase cable can be led to the shielding end G end of the megohmmeter after being tightly clung to the outer surface of the second umbrella group by a first metal wire at the measured end, the terminal end of the measured phase cable can be led to the shielding end G end of the megohmmeter by means of the non-measured phase after being tightly clung to the outer surface of the second umbrella skirt by a second metal wire at the non-measured end B end, and thus, simultaneous shielding of the insulation resistance of the two ends of the terminal end to the ground is realized, and measured data are real data of the insulation resistance of each phase conductive core to the ground. As shown in fig. 2, taking the tested end of the tested cable as an end a, the tested phase as an example of phase a, the phase B as a first non-tested phase, and the phase C as a second non-tested phase, the terminal end of the phase a cable can be led to the shielding end G of the megohmmeter after being tightly wound around the outer surface of the second umbrella skirt by a first metal wire at the measurement end, and the terminal end of the phase a cable can be led to the shielding end G of the megohmmeter after being tightly wound around the outer surface of the second umbrella skirt by a second metal wire at the non-measurement end. Similarly, when the measured phase is B phase, the B phase terminal of the non-measuring end can be shielded by the C phase cable, i.e., when the B phase is measured phase, the first non-measured phase is C phase, and the second non-measured phase is a phase. When the insulation resistance of the C phase is measured, the insulation resistance of the C phase terminal end of the non-measuring end can be shielded by the aid of the A phase cable, namely when the C phase is the measured phase, the first non-measured phase is the A phase, and the second non-measured phase is the B phase.
According to the system for shielding and measuring the insulation resistance of the 10kV cable, when the measured end of the measured cable is used for measuring the insulation resistance of each phase cable, the terminal end of the measured phase cable can be clung to the shielding end G end of the megohmmeter by the first metal wire after being clung to the outer surface of the second umbrella skirt for one circle, the terminal end of the measured phase cable can be clung to the shielding end G end of the megohmmeter by the second metal wire after being clung to the outer surface of the second umbrella skirt for one circle, the insulation resistance of the two ends of the cable to the ground is shielded, the measured data are real data of the insulation resistance of each phase conductive core to the ground, and the technical problems that the existing method for measuring the insulation resistance of the high-voltage equipment for measuring the megohmmeter cannot be directly suitable for insulation resistance measurement of the high-voltage cable and cannot accurately measure the insulation resistance of the high-voltage cable body to the ground are solved.
Example 2
For ease of understanding, referring to fig. 3 to 4, another embodiment of a system for shielding and measuring insulation resistance of a 10kV cable is provided in the present invention, the system includes the system for shielding and measuring insulation resistance of a 10kV cable in embodiment 1, and further includes a first 220V ac contactor KA, a second 220V ac contactor KB, a third 220V ac contactor KC, a first normally open contact button SA, a second normally open contact button SB, a third normally open contact button SC, and a normally closed contact button ST;
the first 220V alternating-current contactor KA, the second 220V alternating-current contactor KB and the third 220V alternating-current contactor KC are provided with seven groups of contacts, wherein the first, second and third groups of contacts are main normally open contacts, the fourth and seventh groups of contacts are auxiliary normally open contacts, and the fifth and sixth groups of contacts are auxiliary normally closed contacts. That is, there are seven sets of contacts for the first 220V ac contactor KA, respectively: the first set of contacts KA1, the second set of contacts KA2, the third set of contacts KA3, the fourth set of contacts KA4, the fifth set of contacts KA5, the sixth set of contacts KA6 and the seventh set of contacts KA7, the first set of contacts KA1, the second set of contacts KA2 and the third set of contacts KA3 are main normally open contacts, the fourth set of contacts KA4 and the seventh set of contacts KA7 are auxiliary normally closed contacts, and the fifth set of contacts KA5 and the sixth set of contacts KA6 are auxiliary normally closed contacts. For the second 220V ac contactor KB, there are seven sets of contacts, respectively: the first set of contacts KB1, the second set of contacts KB2, the third set of contacts KB3, the fourth set of contacts KB4, the fifth set of contacts KB5, the sixth set of contacts KB6 and the seventh set of contacts KB7, the first set of contacts KB1, the second set of contacts KB2 and the third set of contacts KB3 are main normally open contacts, the fourth set of contacts KB4 and the seventh set of contacts KB7 are auxiliary normally open contacts, and the fifth set of contacts KB5 and the sixth set of contacts KB6 are auxiliary normally closed contacts. For the third 220V ac contactor KC, there are seven sets of contacts, respectively: the first set of contacts KC1, the second set of contacts KC2, the third set of contacts KC3, the fourth set of contacts KC4, the fifth set of contacts KC5, the sixth set of contacts KC6 and the seventh set of contacts KC7, the first set of contacts KC1, the second set of contacts KC2 and the third set of contacts KC3 are main normally open contacts, the fourth set of contacts KC4 and the seventh set of contacts KC7 are auxiliary normally open contacts, and the fifth set of contacts KC5 and the sixth set of contacts KC6 are auxiliary normally closed contacts.
The function of the normally open contact of the contactor is that the contact is opened when the contactor is not electrified and is not operated, the contact is closed after the contactor is electrified and is opposite to the normally open contact, namely, the contact is closed when the contactor is not electrified and is not operated, and the contact is opened after the contactor is electrified and is operated. The normally open contact button is such that the contact is open before it is not depressed, and is closed after the button is depressed. The function of the normally closed contact button is that the contacts are closed before the button is not pressed, and the contacts are opened after the button is pressed.
One end of the normally closed contact button ST is connected with a 220V power supply, and the other end of the normally closed contact button ST is respectively connected with one ends of the first normally open contact button SA, the second normally open contact button SB and the third normally open contact button SC;
the other end of the first normally open contact button SA is sequentially connected with a fifth group of contacts KB5 of the second 220V alternating-current contactor KB, a fifth group of contacts KC5 of the third 220V alternating-current contactor KC and the first 220V alternating-current contactor KA, the first 220V alternating-current contactor KA is connected with a 220V power supply, and a fourth group of contacts KA4 of the first 220V alternating-current contactor KA is connected with the first normally open contact button SA in parallel.
The other end of the second normally open contact button SB is sequentially connected with a fifth group of contacts KA5 of the first 220V alternating current contactor KA, a sixth group of contacts KC6 of the third 220V alternating current contactor KC and the second 220V alternating current contactor KB, the second 220V alternating current contactor KB is connected with a 220V power supply, and a fourth group of contacts KB4 of the second 220V alternating current contactor KB is connected with the second normally open contact button SB in parallel.
The other end of the third normally open contact SC button is sequentially connected with a sixth group of contacts KA6 of the first 220V alternating current contactor KA, a sixth group of contacts KB6 of the second 220V alternating current contactor KB and a third 220V alternating current contactor KC, the third 220V alternating current contactor KC is connected with a 220V power supply, and a fourth group of contacts KC4 of the third 220V alternating current contactor KC is connected with the third normally open contact button SC in parallel.
The measured end of the measured cable is connected to the L end of the megohmmeter through a first set of contacts KA1 of a first 220V alternating current contactor KA, a first set of contacts KB1 of a second 220V alternating current contactor KB and a first set of contacts KC1 of a third 220V alternating current contactor KC respectively, and the measured end first non-measured phase of the measured cable is connected to the G end of the megohmmeter through a second set of contacts KA2 of the first 220V alternating current contactor KA, a second set of contacts KB2 of the second 220V alternating current contactor KB and a second set of contacts KC2 of the third 220V alternating current contactor KC respectively, and the measured end second non-measured phase of the measured cable is connected to the E end of the megohmmeter through a third set of contacts KA3 of the first 220V alternating current contactor KA, a third set of contacts KB3 of the second 220V alternating current contactor KB and a third set of contacts KC3 of the third 220V alternating current contactor KC respectively.
Taking the measurement of the insulation resistance of the 10kV cable a phase as an example, in the control circuit of fig. 3, the circuit is energized, and the first 220V ac contactor KA, the second 220V ac contactor KB, and the third 220V ac contactor KC are all in the open state, and the first 220V ac contactor KA, the second 220V ac contactor KB, and the third 220V ac contactor KC are not applied with 220V ac voltages at both ends thereof, so that they do not operate. After the first normally open contact button SA is pressed, the 220V alternating current contactor KA is connected with 220V alternating current voltage through a branch of the first 220V alternating current contactor KA to enable the first 220V alternating current contactor KA to operate, a fourth group of contacts KA4 connected with the first normally open contact button SA in parallel are closed, after the first normally open contact button SA is loosened, a self-retaining circuit is formed through the fourth group of contacts KA4, and the 220V alternating current is ensured to be continuously applied to two ends of the first 220V alternating current contactor KA to keep operating. At this time, in the measurement circuit of fig. 4, the first set of contacts KA1, the second set of contacts KA2, and the third set of contacts KA3 are connected, so that the a-phase cable is connected to the high voltage output terminal of the megohmmeter, i.e., the L-terminal, the B-phase cable connected to the shielding wires of the two terminal ends of the a-phase cable is connected to the shielding terminal of the megohmmeter, i.e., the G-terminal, through the second set of contacts KA2, and the C-phase cable is connected to the ground terminal of the megohmmeter, i.e., the E-terminal, through the third set of contacts KA 3. The measured data is the body insulation resistance of the insulation resistance outside the terminal heads at two sides of the A-phase cable conductive core shielding the ground, and after the measurement is finished, the A-phase cable is subjected to ground discharge. Pressing the normally closed contact button ST causes the first 220V ac contactor KA to lose voltage and the first 220V ac contactor KA to reset. The insulation resistance measurement of the B-phase cable and the insulation resistance measurement of the C-phase cable are similarly available, and are not described in detail herein.
According to the system for shielding and measuring the insulation resistance of the 10kV cable, provided by the invention, the wiring of the megameter is not required to be changed, the electrical loop is switched through the button switch, the high-voltage end, the shielding end and the grounding end of the megameter are connected to the cables of the test phase, the shielding phase and the grounding phase through the corresponding contacts, the measurement of the insulation resistance of the A, B, C three-phase cable to the ground can be respectively completed, and the test efficiency is improved.
Meanwhile, in the system for shielding and measuring the insulation resistance of the 10kV cable, each of three branches of a control loop is respectively connected with auxiliary normally-closed contacts of other two-branch alternating-current contactors in series, namely, a first 220V alternating-current contactor KA branch is connected with auxiliary normally-closed contacts KB5 and KC5 of a second 220V alternating-current contactor KB and a third 220V alternating-current contactor KC in series, the second 220V alternating-current contactor KB branch is connected with auxiliary normally-closed contacts KA5 and KC6 of the first 220V alternating-current contactor KA and the third 220V alternating-current contactor KC branch in series, and the third 220V alternating-current contactor KC branch is connected with auxiliary normally-closed contacts KA6 and KC6 of the second 220V alternating-current contactor KB in series.
In one embodiment, as shown in fig. 5, the system for shielding and measuring insulation resistance of a 10kV cable provided by the present invention may further include a first indicator light module, a second indicator light module, and a third indicator light module, where the first indicator light module is connected in series with a seventh set of contacts KA7 of the first 220V ac contactor KA, the second indicator light module is connected in series with a seventh set of contacts KB7 of the second 220V ac contactor KB, and the third indicator light module is connected in series with a seventh set of contacts KC7 of the third 220V ac contactor KC. The first indicator lamp module comprises a first indicator lamp LA and a first voltage dividing resistor RA which are connected in series, the second indicator lamp module comprises a second indicator lamp LB and a second voltage dividing resistor RB which are connected in series, and the third indicator lamp module comprises a third indicator lamp LC and a third voltage dividing resistor RC which are connected in series. When the insulation resistance of the A-phase cable is measured, the seventh group of contacts KA7 of the first 220V alternating current contactor KA are connected, so that the first indicator lamp LA is lightened, and the effect of indicating that the insulation resistance of the A-phase cable is measured currently is achieved. Similarly, when the insulation resistance of the B-phase cable is measured, the seventh set of contacts KB7 of the second 220V ac contactor KB are turned on, so that the second indicator lamp LB is turned on, and the effect of indicating that the insulation resistance of the B-phase cable is measured currently is achieved. When the insulation resistance of the C-phase cable is measured, the seventh group of contacts KC7 of the third 220V alternating current contactor KC is connected, so that the first indicator light LC is on, and the effect of indicating that the insulation resistance of the C-phase cable is measured currently is achieved.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (3)
1. A system for shielding measurement of insulation resistance of a 10kV cable, comprising: megameter, cable under test, first metal wire and second metal wire;
the measured end of the measured cable is connected with the L end of the megohmmeter, one end of the first metal wire is tightly clung to the outer surface of the second umbrella skirt of the measured phase terminal and fixed round, the other end of the first metal wire is connected to the G end of the megohmmeter through the first non-measured end of the measured cable, and the second non-measured end of the measured cable is connected to the E end of the megohmmeter;
one end of the second metal wire is tightly attached to the outer surface of a second umbrella skirt of the non-tested end tested phase terminal of the tested cable, and the other end of the second metal wire is connected with a first non-tested end of the tested cable, so that the other end of the second metal wire is connected to the G end of the megameter through the first non-tested end of the tested cable;
the device further comprises a first 220V alternating current contactor, a second 220V alternating current contactor, a third 220V alternating current contactor, a first normally open contact button, a second normally open contact button, a third normally open contact button and a normally closed contact button;
the first 220V alternating current contactor, the second 220V alternating current contactor and the third 220V alternating current contactor are provided with seven groups of contacts, wherein the first, the second and the third groups of contacts are main normally open contacts, the fourth and the seventh groups of contacts are auxiliary normally open contacts, and the fifth and the sixth groups of contacts are auxiliary normally closed contacts;
one end of the normally closed contact button is connected with a 220V power supply, and the other end of the normally closed contact button is respectively connected with one ends of the first normally open contact button, the second normally open contact button and the third normally open contact button;
the other end of the first normally open contact button is sequentially connected with a fifth group of contacts of a second 220V alternating current contactor, a fifth group of contacts of a third 220V alternating current contactor and a first 220V alternating current contactor, the first 220V alternating current contactor is connected with a 220V power supply, and a fourth group of contacts of the first 220V alternating current contactor are connected with the first normally open contact button in parallel;
the other end of the second normally open contact button is sequentially connected with a fifth group of contacts of the first 220V alternating-current contactor, a sixth group of contacts of the third 220V alternating-current contactor and the second 220V alternating-current contactor, the second 220V alternating-current contactor is connected with a 220V power supply, and a fourth group of contacts of the second 220V alternating-current contactor are connected with the second normally open contact button in parallel;
the other end of the third normally open contact button is sequentially connected with a sixth group of contacts of the first 220V alternating current contactor, a sixth group of contacts of the second 220V alternating current contactor and a third 220V alternating current contactor, the third 220V alternating current contactor is connected with a 220V power supply, and a fourth group of contacts of the third 220V alternating current contactor are connected with the third normally open contact button in parallel;
the measured end measured phase terminal of the measured cable is connected to the L end of the megohmmeter through a first group of contacts of the first 220V alternating current contactor, a first group of contacts of the second 220V alternating current contactor and a first group of contacts of the third 220V alternating current contactor respectively, the measured end first non-measured phase of the measured cable is connected to the G end of the megohmmeter through a second group of contacts of the first 220V alternating current contactor, a second group of contacts of the second 220V alternating current contactor and a second group of contacts of the third 220V alternating current contactor respectively, and the measured end second non-measured phase of the measured cable is connected to the E end of the megohmmeter through a third group of contacts of the first 220V alternating current contactor, a third group of contacts of the second 220V alternating current contactor and a third group of contacts of the third 220V alternating current contactor respectively.
2. The system for shielding measurement of insulation resistance of a 10kV cable of claim 1, further comprising: the first indicator light module, the second indicator light module and the third indicator light module;
the first indicator light module is connected in series with a seventh group of the first 220V alternating current contactor;
the second indicator light module is connected in series with a seventh group of the second 220V alternating current contactor;
the third indicator light module is connected in series with a seventh set of contacts of the third 220V ac contactor.
3. The system for shielding and measuring insulation resistance of a 10kV cable according to claim 2, wherein the first indicator light module comprises a first indicator light and a first voltage dividing resistor connected in series, the second indicator light module comprises a second indicator light and a second voltage dividing resistor connected in series, and the third indicator light module comprises a third indicator light and a third voltage dividing resistor connected in series.
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| JPH07198775A (en) * | 1993-12-28 | 1995-08-01 | Sumitomo Electric Ind Ltd | Method for measuring dc leakage current from power cable |
| JPH07260870A (en) * | 1994-03-16 | 1995-10-13 | Sumitomo Electric Ind Ltd | Method for measuring dc leak current of power cable |
| CN102680859B (en) * | 2012-05-31 | 2014-11-19 | 北京空间飞行器总体设计部 | Conduction and insulation testing method for cable network |
| CN109444542A (en) * | 2018-10-30 | 2019-03-08 | 国网山西省电力公司晋城供电公司 | A kind of fully automatic secondary insulating resistance of cable auxiliary test unit and its test method |
| CN109490633A (en) * | 2018-12-03 | 2019-03-19 | 河北大唐国际唐山热电有限责任公司 | High pressure outside line porcelain insulator resistance measurement bar and its application method |
| CN217007556U (en) * | 2021-12-03 | 2022-07-19 | 国网山西省电力公司电力科学研究院 | Testing arrangement of filthy degree grade of high voltage external insulation equipment |
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