CN112269064A - Power distribution network earth leakage resistance measurement system and method - Google Patents
Power distribution network earth leakage resistance measurement system and method Download PDFInfo
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- CN112269064A CN112269064A CN202011109985.3A CN202011109985A CN112269064A CN 112269064 A CN112269064 A CN 112269064A CN 202011109985 A CN202011109985 A CN 202011109985A CN 112269064 A CN112269064 A CN 112269064A
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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
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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
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
- H01F27/402—Association of measuring or protective means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F29/00—Variable transformers or inductances not covered by group H01F21/00
- H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
- H01F29/025—Constructional details of transformers or reactors with tapping on coil or windings
Abstract
The invention provides a system and a method for measuring earth leakage resistance of a power distribution network, wherein the method comprises the following steps: any tapping tap of any phase or multi-phase winding at the side of the regulating grounding transformer system is connected with the grounding switch; changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value; measuring zero sequence current values of all the feeder lines by using a feeder line terminal unit zero sequence current transformer; and measuring and calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value. The method is simple and easy to operate, and the measurement error caused in the measurement process of the ground leakage resistance can be effectively avoided due to the adoption of the grounding transformer, so that the accurate measurement of the ground leakage resistance is realized; in addition, the method is not influenced by a neutral point grounding mode of the power distribution network, the applicability of the measurement technology is improved, the impact and protection misoperation caused by overlarge zero-sequence voltage on the system can be avoided, the normal operation of the power distribution network is not influenced, and the measurement process is safe and reliable.
Description
Technical Field
The invention relates to the field of measurement of technical parameters of a power distribution network, in particular to a grounding transformer, a power distribution network earth leakage resistance measurement system and a method.
Background
In China, a neutral point non-effective grounding mode is widely adopted for low-voltage distribution networks. When a single-phase earth fault occurs in a medium-low voltage distribution network, if the earth current is small, the earth arc can be automatically extinguished at the zero crossing point of the fault current, and a neutral point ungrounded mode can be adopted for the distribution network; if the current to ground is large, particularly if the capacitance current is larger than 10A, the fault arc can be re-ignited after zero crossing extinguishment, intermittent arc overvoltage is easily caused, and intermittent arc extinguishment is easily deteriorated to be an interphase fault, so that when the capacitance current is larger than 10A, an arc suppression coil is required to be arranged to compensate the capacitance current and suppress fault grounding current.
The distribution network ground parameters include capacitance to ground and leakage conductance to ground. In the ground current of a power distribution network, the ratio of capacitive current is large, and the traditional arc suppression coil can only compensate the capacitive current and has no effect on leakage current, so that the current ground parameter measurement research is mainly developed aiming at a ground capacitance measurement method. However, as the cable line laying length of the power distribution network in China increases, active components in single-phase earth fault current rapidly rise, so that fault arcs are difficult to eliminate. Therefore, accurate measurement of the leakage resistance of the power distribution network to the ground becomes an important basis for improving the grounding mode of the power distribution network. The full current compensation arc suppression coil can effectively compensate reactive and active components of fault current, suppress fault overvoltage and reduce fault arc rate, and the compensation capacity and the effect mainly depend on the measurement precision of the earth capacitance and the earth leakage conductance of the power distribution network. In addition, the active arc suppression technology of the power distribution network which is emerging in recent years also needs accurate and rapid measurement technology of capacitance to ground and leakage conductance to ground as a powerful support. Since the conventional measurement method for measuring the capacitance to ground is used for more research, and the measurement of the resistance to ground leakage becomes a major and difficult point in the ground parameter measurement technology, it is difficult for the existing method to accurately measure the resistance to ground leakage.
Disclosure of Invention
In view of the above, the invention provides a grounding transformer, a power distribution network earth leakage resistance measurement system and a method thereof, which are used for overcoming the technical problem that it is difficult to accurately measure earth leakage resistance in the prior art.
A grounding transformer installed or disposed in a non-active grounding system, comprising:
the tapping taps are arranged on each phase winding on the side of the grounding transformer system; each phase winding is provided with a plurality of tapping points, and each tapping point on each phase winding can be connected with a grounding switch; when one tap is connected with the grounding switch, the winding at the position corresponding to the tap is grounded.
The grounding transformer in the embodiment of the invention is mainly installed or arranged in a non-effective grounding system, and comprises a plurality of tapping taps arranged on each phase winding at the side of the grounding transformer system, and each tapping tap on each phase winding can be connected with a grounding switch; when one tap is connected with the grounding switch, the winding at the corresponding position of the tap is grounded. The grounding transformer can be used in a power distribution network earth leakage resistance measuring system, so that the grounding transformer is used for measuring earth leakage resistance, is simple in structure and convenient to use, and can enable a measuring result to be accurate.
Further, a plurality of the tap taps are uniformly arranged on the winding of each phase.
According to the grounding transformer, the embodiment of the invention also provides a system for measuring the leakage resistance of the power distribution network to the ground.
A power distribution network earth leakage resistance measurement system comprises a non-effective grounding system and any one grounding transformer;
the head end of each phase of winding is respectively and correspondingly connected with a three-phase line of a power distribution network in a non-effective grounding system, the power distribution network in the non-effective grounding system leads out a central point through the grounding transformer, and the central point is grounded through a closed switch and impedance in sequence.
The grounding transformer is adopted in the power distribution network ground leakage resistance measuring system, so that the power distribution network ground leakage resistance measuring system is simple in structure, convenient to use and capable of enabling a measuring result to be accurate.
Further, when the tapping tap at different positions on the winding of any phase is selected to be connected with the grounding switch, the number of turns of the grounding part winding is changed.
Furthermore, the number of the grounding switches is three, and the grounding switches are arranged corresponding to the windings of each phase; when any one tap on any one phase of winding is connected with the correspondingly arranged grounding switch, each tap on the remaining two phases of windings is disconnected with the correspondingly arranged grounding switch.
Further, the grounding switch is a vacuum circuit breaker.
According to the system for measuring the earth leakage resistance of the power distribution network, the embodiment of the invention provides a method for measuring the earth leakage resistance of the power distribution network.
A method for measuring the earth leakage resistance of a power distribution network by using the system for measuring the earth leakage resistance of the power distribution network comprises the following steps:
any tapping tap of any phase or multi-phase winding at the side of the regulating grounding transformer system is connected with the grounding switch;
changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value;
measuring zero sequence current values of all the feeder lines by using a feeder line terminal unit zero sequence current transformer;
and measuring and calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value.
According to the method for measuring the earth leakage resistance of the power distribution network, any tapping tap of any phase or any tapping tap of a multi-phase winding on the side of a grounding transformer system is adjusted to be connected with a grounding switch; then changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value; measuring zero sequence current values of all the feeder lines by using a feeder line terminal unit zero sequence current transformer; and finally, measuring and calculating according to the zero sequence voltage value and the zero sequence current value to obtain the earth leakage resistance of the power distribution network. The method has simple and easy test process, and can effectively avoid measurement errors caused in the process of measuring the earth leakage resistance due to the adoption of the grounding transformer, thereby realizing the accurate measurement of the earth leakage resistance; in addition, the method is not influenced by a neutral point grounding mode of the power distribution network, the applicability of the measurement technology is improved, the impact and protection misoperation caused by overlarge zero-sequence voltage on the system can be avoided, the normal operation of the power distribution network is not influenced, and the measurement process is safe and reliable.
Further, before the step of adjusting any tap of any phase or any multi-phase winding on the side of the grounding transformer system to be grounded, the method comprises the following steps:
and carrying out gear arrangement on each tapping tap of each phase winding on the side of the grounding transformer system according to the distribution sequence.
Further, the step of adjusting any tap of any phase or multi-phase winding on the side of the grounding transformer system to be grounded comprises the following steps:
and the tap of the lowest gear in any phase or multi-phase winding on the side of the regulating grounding transformer system is connected with the tap switch.
Further, the step of measuring and calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value comprises:
calculating the earth leakage resistance of the power distribution network according to the following expression:
wherein R represents the leakage resistance of the power distribution network to the ground,
the value of the zero-sequence current is represented,
representing a zero sequence voltage value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a grounding transformer according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a system for measuring earth leakage resistance of a power distribution network according to an embodiment of the present invention;
fig. 3 is a schematic flow chart of a method for measuring earth leakage resistance of a power distribution network according to an embodiment of the present invention;
fig. 4 is an equivalent circuit diagram of a measurement of leakage resistance to ground of a power distribution network according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a system for measuring earth leakage resistance of a power distribution network according to another embodiment of the present invention;
FIG. 6 is a graph of bus voltage waveform changes provided by one embodiment of the present invention;
fig. 7 is a diagram of a zero-sequence voltage waveform variation according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to explain the invention in more detail, the grounding transformer, the distribution network earth leakage resistance measurement system and the method provided by the invention are specifically described below with reference to the attached drawings.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a grounding transformer according to an embodiment of the present invention; a grounding transformer installed or disposed in a non-active grounding system, comprising: a plurality of tap taps (1-K) arranged on the respective phase windings (A) of the system side of the grounding transformerY、BYAnd CY) The above step (1); wherein each phase winding (A)Y、BYAnd CY) A plurality of tapping taps (1-K) are arranged on the phase winding, and each tapping tap on each phase winding can be connected with a grounding switch (S2); when one of the tap joints is connected to the grounding switch (S2), the winding at the position corresponding to the tap joint is grounded.
In one embodiment, the plurality of tap taps are evenly arranged on each phase winding.
Alternatively, the number of tap taps provided in each phase winding may be the same or different.
In an alternative embodiment, the grounding transformer is a Y/Δ -wired grounding transformer.
The grounding transformer in the embodiment of the invention is mainly installed or arranged in a non-effective grounding system, and comprises a plurality of tapping taps arranged on each phase winding at the side of the grounding transformer system, and each tapping tap on each phase winding can be connected with a grounding switch; when one tap is connected with the grounding switch, the winding at the corresponding position of the tap is grounded. The grounding transformer can be used in a power distribution network earth leakage resistance measuring system, so that the grounding transformer is used for measuring earth leakage resistance, is simple in structure and convenient to use, and can enable a measuring result to be accurate.
According to the grounding transformer, the embodiment of the invention also provides a system for measuring the leakage resistance of the power distribution network to the ground.
As shown in fig. 2, a system for measuring the leakage resistance to ground of a power distribution network comprises a non-effective grounding system and any grounding transformer; each phase winding (A)Y、BYAnd CY) Respectively with three-phase lines of the distribution network in a non-active earthing system (i.e. E in the figure)A、EBAnd EC) Correspondingly connected, a power distribution network in the non-effective grounding system leads out a central point (point O in the figure) through a grounding transformer, and the central point is grounded through a closed switch (S1) and an impedance (Z) in sequence. And a plurality of tapping taps are uniformly arranged on the side winding of the grounding transformer system. Assuming that the total number of turns of the coil of each phase winding is n, the number of taps of each phase winding is K. The tap position number X of each phase is sequentially increased from the system neutral point to the feeder outlet and is respectively 1, 2, … and K, and the number of turns n of the coil from each tap to the neutral pointXIs n in sequence1、n2、…、nK。aΔ、bΔ、cΔFor grounding the low-voltage side winding of the transformer, S2Is a grounding switch.
As shown in fig. 2, the operating principle of the system for measuring the earth leakage resistance of the power distribution network is as follows: the zero sequence voltage of the power distribution network is changed by utilizing a grounding transformer externally connected with the power distribution network and grounding the tapping taps of the windings on the system side of the grounding transformer, an open-ended triangular voltage transformer is adopted to measure the zero sequence voltage, meanwhile, the zero sequence current of a feeder line is measured by the zero sequence voltage transformer, and the voltage and the current obtained by measurement are used for calculating the earth leakage resistance of the system.
In one embodiment, the number of turns of the grounding portion winding is changed when a tap at a different position on any one phase winding is selected to be connected to the grounding switch.
Specifically, since the tap taps are respectively disposed at different positions of the winding, the number of winding turns represented by the different positions of the winding is different. When the tapping tap at each position is connected with the grounding switch, the winding at the position corresponding to the tapping tap is grounded; when tap taps at different positions are selected to be connected with the grounding switch, the number of turns of the grounded winding can be changed. The ground winding is also called a short-circuit winding, so that the occupation ratio of the short-circuit winding can be changed by changing the positions of the ground switch and the tap, and the occupation ratio of the short-circuit winding is the proportion of the number of turns of the short-circuit winding to the number of turns of the whole winding.
In one embodiment, the number of the grounding switches is three, and the grounding switches are arranged corresponding to each phase of winding; when any tap on any phase winding is connected with the correspondingly arranged grounding switch, each tap on the rest two phase windings is disconnected with the correspondingly arranged grounding switch.
In one embodiment, the grounding switch is a vacuum interrupter.
As shown in fig. 2, the number of the ground switches (S2) is three, that is, one ground switch is provided for each phase winding. Wherein each tap on each phase winding can be connected with a correspondingly arranged grounding switch. The grounding switch can be a vacuum circuit breaker, wherein the coil of any one vacuum circuit breaker is connected with the closed contacts of the other two vacuum circuit breakers in series to realize locking protection, and two-point grounding of a winding of the grounding transformer system can not occur when a certain phase tapping point is adjusted to be grounded arbitrarily.
The grounding transformer is adopted in the power distribution network ground leakage resistance measuring system, so that the power distribution network ground leakage resistance measuring system is simple in structure, convenient to use and capable of enabling a measuring result to be accurate.
According to the system for measuring the earth leakage resistance of the power distribution network, the embodiment of the invention provides a method for measuring the earth leakage resistance of the power distribution network.
As shown in fig. 3, a method for measuring the earth leakage resistance of a distribution network by using the system for measuring the earth leakage resistance of the distribution network comprises the following steps:
step S102, adjusting any tapping tap of any phase or multi-phase winding at the side of the grounding transformer system to be connected with a grounding switch;
step S104, changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value;
step S106, measuring zero sequence current values of all the feeders by using a feeder terminal unit zero sequence current transformer;
and S108, measuring and calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value.
According to the method for measuring the earth leakage resistance of the power distribution network, any tapping tap of any phase or any tapping tap of a multi-phase winding on the side of a grounding transformer system is adjusted to be connected with a grounding switch; then changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value; measuring zero sequence current values of all the feeder lines by using a feeder line terminal unit zero sequence current transformer; and finally, measuring and calculating according to the zero sequence voltage value and the zero sequence current value to obtain the earth leakage resistance of the power distribution network. The method has simple and easy test process, and can effectively avoid measurement errors caused in the process of measuring the earth leakage resistance due to the adoption of the grounding transformer, thereby realizing the accurate measurement of the earth leakage resistance; in addition, the method is not influenced by a neutral point grounding mode of the power distribution network, the applicability of the measurement technology is improved, the impact and protection misoperation caused by overlarge zero-sequence voltage on the system can be avoided, the normal operation of the power distribution network is not influenced, and the measurement process is safe and reliable.
In one embodiment, the step of adjusting any tap ground of any phase or multi-phase winding on the side of the grounding transformer system comprises the following steps:
and carrying out gear arrangement on each tapping tap of each phase winding on the side of the grounding transformer system according to the distribution sequence.
In one embodiment, the step of adjusting any tap grounding of any phase or multi-phase winding on the side of the grounding transformer system comprises:
and a tap of the lowest gear in any phase or multi-phase winding on the side of the regulating grounding transformer system is connected with a tap switch.
In one embodiment, the step of calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value includes:
calculating the earth leakage resistance of the power distribution network according to the following expression:
wherein R represents the leakage resistance of the power distribution network to the ground,
the value of the zero-sequence current is represented,
and representing a zero sequence voltage value, and Re represents a real part of a numerical value.
Specifically, the principle of the measuring method of the earth leakage resistance of the power distribution network is as follows: as shown in figure 2 of the drawings, in which,
three-phase power supply potential, C, of non-effectively earthed distribution networkA、CB、CCTo a non-effective ground potential of the distribution network, rA、rB、rCFor the non-effectively grounded power distribution network to earth leakage resistance, the non-effectively grounded power distribution network leads out a neutral point O and a switch S through a Y/delta connection grounding transformer1The closed neutral point is grounded through impedance Z, Z-R represents a neutral point grounded through a small resistor, Z-R' + j omega L represents a neutral point grounded through an arc suppression coil series resistor, and the switch S1Open indicates a neutral ungrounded mode. A. theY、BY、CYThe system side winding of the grounding transformer for Y/delta connection is characterized in that the head end of the system side winding of the grounding transformer is directly connected with a three-phase line of a non-effective grounding distribution network, tapping taps are arranged at different positions of each phase winding of the system side of the grounding transformer, and the tapping taps of each phase winding can be led to a grounding switch S through lead-out wires2，S2The coil of one vacuum circuit breaker is connected with the normally closed contacts of the other two vacuum circuit breakers in series to realize locking protection, so that the coil of one vacuum circuit breaker can not be out when a tap is connected to the ground by randomly adjusting a certain phaseTwo points of the winding of the existing grounding transformer system are grounded.
The number of turns on the system side of the grounding transformer is N1The number of turns on the low voltage side is N2The winding of the grounded part via the gear is regarded as a third winding of the grounding transformer. The leakage reactance from the system side to the grounding gear point of the grounding transformer is x1σThe number of turns is (1-alpha) N1Alpha is the ratio of the number of turns of the grounding variable short circuit winding to the number of turns of the high-voltage side winding, and is defined as 0, 1](ii) a The leakage reactance of the winding of the grounding part of the grounding transformer is x2σThe number of turns is alpha N1(ii) a The leakage reactance of the low-voltage side of the grounding transformer is x3σThe number of turns is N2。
Obtaining the leakage reactance expression of each winding of the grounding transformer according to the internal grounding formula of the transformer winding as follows:
where ω is the angular frequency, λ0The core permeance is, S is the cross-sectional area of the magnetic resistance, ρ is the magnetic resistance rate of the leakage flux passing through the magnetic circuit, and L is the magnetic circuit length.
Since the ground gear of the grounding transformer is adjusted, that is, the short-circuit winding ratio α is changed, α is taken as an independent variable to derive the expression:
total zero sequence impedance Z of earth short circuit branchT0Comprises the following steps:
known by x'1σ＜0，x′2σ＞0，x′3σ< 0, so leakage reactance x increases with the ground to ground gear1σAnd x3σMonotonically decreasing while x2σMonotonically increasing. Therefore, the total zero sequence impedance Z of the grounding branchT0Will decrease and the neutral voltage will increase.
In addition, the equivalent circuit diagram of the measurement of the earth leakage resistance of the distribution network is shown in FIG. 4, wherein
The open-circuit voltage when the tapping tap is grounded is adjusted for a certain phase winding on the side of the grounding transformer system, and zero-sequence voltage is generated by adjusting the tapping tap of the side winding of the grounding transformer system to be grounded
And zero sequence current
The two are made into a quotient:
the expression of the earth leakage resistance of the non-effectively grounded power distribution network can be obtained:
re represents the real part of the numerical value.
Effect embodiment:
in order to verify the effectiveness of the method for measuring the earth leakage resistance of the power distribution network, a 10kV non-effective grounding power distribution network model shown in FIG. 5 is built in a PSCAD/EMTDC simulation environment for simulation analysis.
The simulation verification is as follows:
the simulation measurement of the ground leakage resistance is carried out for different types of distribution feeders (overhead lines, cable lines and mixed lines), and the simulation parameters of the non-effectively grounded distribution feeder are shown in table 1.
TABLE 1 feeder simulation parameters
Under the feeder simulation parameters shown in Table 1, the grounding switch S1Opening the neutral point of the analog power distribution network without grounding, setting 5 grounding gears from the neutral point side to the system side of the side winding of the grounding transformer system, and respectively corresponding to the tapping taps T1To T5. Regulating the side winding T of the C-phase system of the grounding transformer when T is 0.05s1The tap is grounded. Grounding tap T1The voltages of the three phase-to-ground and neutral points of the system measured after grounding are shown in fig. 6 and 7, respectively. Fig. 6 and 7 show the side winding tap T of the C-phase system of the grounding transformer1After grounding, the neutral point displacement voltage should not exceed the allowable range of the operation regulation of the power system, so that great damage to power equipment and potential threat to the safe and stable operation of the system are avoided.
The grounding mode of the system neutral point can adopt an over-compensated grounding mode and a non-grounding mode through arc suppression coils respectively. Grounding switch S1The neutral point of the closed simulation power distribution network is grounded through the arc suppression coil, and the detuning degrees of the arc suppression coil are respectively 5%, 8%, 10% and 100%; degree of detuning 100% represents the earthing switch S1And opening the neutral point of the analog power distribution network without grounding. Side winding T of regulating grounding transformer C phase system1The tap is grounded. Grounding tap T1After being grounded, the zero sequence voltage and the zero sequence current measured by the zero sequence current transformer are measured by the open-ended triangular voltage transformer, so that the neutral point non-effectively grounded power distribution network with different detuning degrees is obtainedThe resistance to ground leakage data of (1) is shown in table 2. As can be seen from the table 2, the measurement error of the earth leakage resistance is within 0.05%, the requirement of the distribution network on the ground parameter measurement precision is met, and the earth leakage resistance of the non-effective grounding distribution network is measured based on the adjustment of the tapping tap of the grounding transformer system winding, so that the influence of the neutral grounding mode of the distribution network is avoided.
TABLE 2 measurement results of the earth leakage resistance at the same grounding gear and different detuning degrees
In the non-grounding mode of the neutral point, the ground parameters of the distribution network are kept unchanged, different taps of the winding on the C-phase system side of the grounding transformer are adjusted to be grounded, and zero sequence voltages and ground leakage resistance data under different grounding gears are obtained and are shown in table 3. The zero sequence voltage is increased along with the increase of the grounding gear, but the zero sequence voltage does not exceed the allowable range of the operation regulation of the power system, so that the power equipment cannot be greatly damaged, and the potential threat to the safe and stable operation of the system can be brought; meanwhile, the result error of the earth leakage resistance obtained by adjusting the earth measurement of different grounding gears meets the requirement of the measurement precision of the power distribution network.
TABLE 3 measurement results of the earth leakage resistance at different grounding gears
In the non-grounding mode of the neutral point, the ground parameters of the three feeders are changed, so that the ground parameters of the whole power distribution network are changed. Side winding T of regulating grounding transformer C phase system1Grounding the tap to obtain T1The results of measurements at different leakage resistances to ground under the ground tap are shown in table 4. It can be known from table 4 that when the line parameters are changed, the result error of the measured earth leakage resistance meets the requirement of the measurement precision of the earth leakage resistance of the power distribution network.
TABLE 4T1Measurement results of different earth leakage resistances under gear
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. An earthing transformer, characterized in that it is installed or provided in a non-active earthing system, comprising: the tapping taps are arranged on each phase winding on the side of the grounding transformer system; each phase winding is provided with a plurality of tapping points, and each tapping point on each phase winding can be connected with a grounding switch; when one tap is connected with the grounding switch, the winding at the position corresponding to the tap is grounded.
2. The grounding transformer of claim 1, wherein a plurality of the tap taps are uniformly arranged on the winding of each phase.
3. A power distribution network to ground leakage resistance measurement system comprising a non-active grounding system and the grounding transformer of claim 1 or 2;
the head end of each phase of winding is respectively and correspondingly connected with a three-phase line of a power distribution network in a non-effective grounding system, the power distribution network in the non-effective grounding system leads out a central point through the grounding transformer, and the central point is grounded through a closed switch and impedance in sequence.
4. The system of claim 3, wherein the number of turns of the grounding portion winding is changed when the tap at different position on the winding of any phase is selected to be connected to the grounding switch.
5. The system for measuring the earth leakage resistance of the power distribution network according to the claim 3 or 4, wherein the number of the earthing switches is three, and the earthing switches are arranged corresponding to the windings of each phase;
when any one tap on any one phase of winding is connected with the correspondingly arranged grounding switch, each tap on the remaining two phases of windings is disconnected with the correspondingly arranged grounding switch.
6. The grounding transformer of claim 5, said grounding switch being a vacuum interrupter.
7. A method for measuring the earth leakage resistance of a power distribution network by using the system for measuring the earth leakage resistance of the power distribution network according to any one of claims 3 to 6, which is characterized by comprising the following steps:
any tapping tap of any phase or multi-phase winding at the side of the regulating grounding transformer system is connected with the grounding switch;
changing the zero sequence voltage of the power distribution network, and measuring through an open-ended triangular voltage transformer to obtain a zero sequence voltage value;
measuring zero sequence current values of all the feeder lines by using a feeder line terminal unit zero sequence current transformer;
and measuring and calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value.
8. The method for measuring the earth leakage resistance of the power distribution network according to claim 7, wherein the step of adjusting any tap of any phase or any multi-phase winding on the side of the grounding transformer system to be grounded is preceded by the steps of:
and carrying out gear arrangement on each tapping tap of each phase winding on the side of the grounding transformer system according to the distribution sequence.
9. The method for measuring the earth leakage resistance of the power distribution network according to claim 8, wherein the step of adjusting the tap ground of any one of the phase windings or any one of the multi-phase windings on the side of the grounding transformer system comprises the following steps:
and the tap of the lowest gear in any phase or multi-phase winding on the side of the regulating grounding transformer system is connected with the tap switch.
10. The method for measuring the earth leakage resistance of the power distribution network according to any one of claims 7 to 9, wherein the step of calculating the earth leakage resistance of the power distribution network according to the zero sequence voltage value and the zero sequence current value measurement comprises:
calculating the earth leakage resistance of the power distribution network according to the following expression:
wherein R represents the leakage resistance of the power distribution network to the ground,
the value of the zero-sequence current is represented,
and representing a zero sequence voltage value, and Re represents a real part of a numerical value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011109985.3A CN112269064A (en) | 2020-10-16 | 2020-10-16 | Power distribution network earth leakage resistance measurement system and method |
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