CN109932567B - Passive measurement method for parameters of overhead transmission line - Google Patents
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Abstract
The invention relates to a passive measurement method for parameters of an overhead transmission line, and belongs to the technical field of passive measurement. The invention comprises the following steps: the method comprises the following steps: obtaining the relative relation of the three-phase induced voltage of the tested line; step two: the induced current is utilized to complete the passive measurement of the line, and the parameters of the resistance of the grounding loop, the resistance of the line, the self-inductance and the mutual inductance of the line can be calculated by only measuring the induced voltage and the induced current of the tested line under different conditions by adopting a passive measurement method. The invention utilizes strong electromagnetic environment around the tested line, and perfectly solves the problem that the normal measurement is difficult to carry out due to overlarge induced current or overhigh induced voltage of the tested line when the traditional method for carrying out the parameter measurement of the overhead line by adopting a pilot frequency power supply.
Description
Technical Field
The invention relates to a passive measurement method for parameters of an overhead transmission line, and belongs to the technical field of passive measurement.
Background
Three-phase current with the frequency approximate to the working frequency (50Hz) of the three-phase overhead transmission line to be tested (such as 40Hz and 60Hz) is injected into the three-phase overhead transmission line to be tested, and the resistance, the self-inductance and the mutual inductance between the phases of the line to be tested can be obtained through certain calculation by utilizing the voltage drop generated in the line to be tested. The reason why the test current slightly differs from the working frequency (50Hz) is the influence of induced voltage and induced current generated in the tested line by space electromagnetic field generated by avoiding other surrounding electrified lines or operating electric equipment on the test result. In practical use, however, the pilot frequency power supply needs to be able to safely accommodate the power frequency induced current with a large amplitude encountered in the field test, in addition to providing the pilot frequency current to the outside. If the induced current in the tested circuit exceeds the safe receiving capacity of the audio power supply, the pilot frequency power supply cannot be used or internal electric components are burnt.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a passive measurement method for overhead transmission line parameters.
The passive measurement method for the parameters of the overhead transmission line is characterized by comprising the following steps of:
the method comprises the following steps: obtaining the relative relation of the three-phase induced voltages of the tested line, comprising the following steps:
the first step is as follows: under the condition that one end of a tested three-phase overhead transmission line is grounded and the other end of the tested three-phase overhead transmission line is open, the open-circuit voltage of a three-phase line is measured simultaneously;
with phase A as reference, its voltage vector is denoted as UAThe angle is 0 degrees, and the B phase voltage vector can be recorded as UBThe vector of the phase C voltage is recorded as UC∠β°；
Because the relative position of the current source of the excitation electromagnetic field is not changed, a three-phase line U can be obtainedA、UBAnd UCThe relative ratio of (A) and (B) is kept unchanged;
by UA、UBAnd UCThe ratio K of the three can be calculatedAB、KBC、KCA：
KAB＝UA/UB (1)
KBC＝UB/UC (2)
KCA＝UC/UA (3)
The second step is that: after the open-circuit voltages of the three-phase lines are obtained, one of the three-phase lines is sequentially short-circuited to the ground, and the other two open-circuit measurement voltage states are kept;
the third step: the phase C is short-circuited to ground, the phases A and B are kept open, and the phase C current is measured to obtain the phase C current icAnd A, B phase voltage uAAnd uB；
(RG+RSC+jXLA)*ic＝uc (4)
uC＝KCA(uA-icXMCA) (5)
uC＝(uB-icXMCB)/KBC (6)
Wherein RG is the loop ground resistance, RSA、RSBAnd RSCRespectively the self-resistance, X, of each phase lineLA、XLBAnd XLCAre the self-inductance, X, of each phaseMAB、XMBCAnd XMCARespectively are mutual inductance among all phase circuits; according to the characteristics of the circuit structure, RSA、RSBAnd RSCHaving a numerically equal relationship, R will be used laterSDirect substitution;
from the above formula, R can be obtainedG+RSSum of (A) and XLC+KCAXMCAThe sum of (1);
by the same token, X can be obtainedLC+XMCB/KBCThe sum of (1);
the fourth step: respectively and independently short-circuiting the phases B and A to the ground in sequence to obtain XLB+KCBXMBC、XLB+XMAB/KABAnd XLA+KABXMAB、XLA+XMCA/KCAThe sum of the six inductive reactance results, corresponding to the six inductive reactance XLA、XLB、XLCAnd XMAB、XMBC、XMCAAn unknown number;
the fifth step: solving six equations to obtain the values of the six inductive reactance, thereby obtaining the coupling inductive reactance among the self inductive reactance of the tested line;
step two: the method utilizes the induction current to complete the passive measurement of the line, and comprises the following small steps:
the first step is as follows: keeping the phase A open circuit, measuring the phase A voltage, and insulating and short-circuiting the phase B and the phase C relative to the ground to form a loop for obtaining the self resistance of the line and the ground loop resistance;
the second step is that: measuring loop current i'BCAnd voltage u'AThey have the following relationships:
[2RS+j(XLB-XLC)]*i′BC＝u'BC (7)
wherein u'BCAs intermediate variables, it is alternatively possible to determine RSThe value of (d); in combination with R determined aboveG+RSThe sum of the ground resistance and the ground resistance of the ground loop can be obtained;
the third step: r can be obtained twice by sequentially insulating A, B relatively and A, C relativelySThe values of (a) and (b) are mutually verified;
the fourth step: at this moment, a passive measurement method is adopted, and parameters of the ground loop resistance, the self-inductance and the mutual inductance of the line can be calculated by only measuring the induced voltage and the induced current of the tested line under different conditions.
Preferably, in the fifth step of the first step, the longer the distance between the tested line and the live power transmission line is, the larger the induced current is; the larger the current transmitted by other live transmission lines is, the larger the induced current is; the closer the other transmission lines are spatially distant from the line under test, the larger the induced current is.
Preferably, in the fifth step, the open-circuit induced voltages generated in the three-phase line of the tested line have the characteristics of same phase and fixed ratio.
Preferably, in the fifth step, the tested line has a large induced current to the ground, because other live operating electrical equipment, especially other live power transmission lines, exist around the tested line.
Preferably, in the second step, the passive measurement is based on a power frequency induced voltage and an induced current generated in the tested line by other nearby live-line operation equipment due to electromagnetic induction.
Preferably, in the second and fourth steps, because other live-line-operated electrical devices, especially transmission lines parallel to the tower, which cause the tested line to generate induced voltage and current, have relatively fixed positions on the tested line, the degree of influence of electromagnetic fields excited by the electrical devices on the three-phase line of the tested line is relatively constant.
The invention has the beneficial effects that: the passive measurement method for the parameters of the overhead transmission line does not need an external pilot frequency power supply or other test power supplies, and fully utilizes induced voltage and induced current generated in the line by other running lines or electrical equipment existing around the tested line to obtain corresponding line parameters. The method fully utilizes the strong electromagnetic environment around the tested line, and perfectly solves the problem that the normal measurement is difficult to carry out due to the fact that the induced current of the tested line is too large or the induced voltage is too high when the traditional method adopts a pilot frequency power supply to carry out the parameter measurement work of the overhead line.
Drawings
FIG. 1 is a diagram of the induced voltage measurement of the tested line according to the present invention.
Fig. 2 is a schematic view of current measurement under single-phase grounding according to the present invention.
Fig. 3 is a diagram of the measurement of the current of two relatively insulated short-circuit loops according to the present invention.
Detailed Description
In order to make the object and technical solution of the present invention more apparent, the present invention will be further described in detail with reference to the following examples.
The passive measurement method for the parameters of the overhead transmission line provided by the invention is specially used for the situation that the induced current of the tested line is large and is difficult to be normally developed by adopting a pilot frequency power supply. Different from the traditional method of injecting pilot frequency test current into the tested line by adopting a pilot frequency power supply, the method provided by the invention fully utilizes the induced current of the tested line to complete the measurement of the resistance, self-inductance and mutual inductance of the line. The tested line has larger induction current to the ground because other live operation electrical equipment exists around the tested line, particularly other live transmission lines. Generally speaking, the longer the distance between other live transmission lines and the tested line is, the larger the induced current is; the larger the current transmitted by other live transmission lines is, the larger the induced current is; the closer the other transmission lines are spatially distant from the line under test, the larger the induced current is.
The passive measurement method for the parameters of the overhead power transmission circuit is used for obtaining the resistance, the self-inductance and the mutual inductance of a line. The basic working principle is based on power frequency induction voltage and induction current generated in a tested line by other nearby live operation equipment due to electromagnetic induction. Because other live-line operating electrical equipment which causes the tested line to generate induced voltage and current, particularly the transmission lines parallel to the tower, have relatively fixed positions on the tested line, the influence degree of the electromagnetic field excited by the equipment on the three-phase line of the tested line is relatively unchanged. Meanwhile, the space distances between the two parts are only a few meters and more than ten meters, and compared with the wavelength of the industrial frequency electromagnetic field of about 6000 kilometers, the difference of induced voltage phase angles in the tested line caused by the difference of the space positions is completely negligible. Based on the theoretical analysis, the open-circuit induction voltage generated in the three-phase line of the tested line has the characteristics of same phase and fixed ratio. And acquiring overhead line parameters.
The passive measurement method for the parameters of the overhead transmission line is characterized by comprising the following steps of:
the method comprises the following steps: obtaining the relative relation of the three-phase induced voltages of the tested line, comprising the following steps:
the first step is as follows: under the condition that one end of a tested three-phase overhead transmission line is grounded and the other end of the tested three-phase overhead transmission line is open, the open-circuit voltage of a three-phase line is measured simultaneously;
as shown in fig. 1. With phase A as reference, its voltage vector is denoted as UAThe angle is 0 degrees, and the B phase voltage vector can be recorded as UBThe vector of the phase C voltage is recorded as UC∠β°；
Because the relative position of the current source of the excitation electromagnetic field is not changed, a three-phase line U can be obtainedA、UBAnd UCThe relative ratio of (A) and (B) is kept unchanged;
by UA、UBAnd UCThe ratio K of the three can be calculatedAB、KBC、KCA：
KAB＝UA/UB (1)
KBC＝UB/UC (2)
KCA＝UC/UA (3)
The second step is that: after the open-circuit voltages of the three-phase lines are obtained, one of the three-phase lines is sequentially short-circuited to the ground, and the other two open-circuit measurement voltage states are kept;
the third step: phase C was shorted to ground, phase a and phase B were left open, and phase C current was measured, as shown in fig. 2. Can obtain C phase current icAnd A, B phase voltage uAAnd uB；
(RG+RSC+jXLA)*ic＝uc (4)
uC＝KCA(uA-icXMCA) (5)
uC＝(uB-icXMCB)/KBC (6)
Wherein RG is the loop ground resistance, RSA、RSBAnd RSCRespectively the self-resistance, X, of each phase lineLA、XLBAnd XLCAre the self-inductance, X, of each phaseMAB、XMBCAnd XMCARespectively are mutual inductance among all phase circuits; according to the characteristics of the circuit structure, RSA、RSBAnd RSCHaving a numerically equal relationship, R will be used laterSDirect substitution;
from the above formula, R can be obtainedG+RSSum of (A) and XLC+KCAXMCAThe sum of (1);
by the same token, X can be obtainedLC+XMCB/KBCThe sum of (1);
the fourth step: respectively and independently short-circuiting the phases B and A to the ground in sequence to obtain XLB+KCBXMBC、XLB+XMAB/KABAnd XLA+KABXMAB、XLA+XMCA/KCAThe sum of the six inductive reactance results, corresponding to the six inductive reactance XLA、XLB、XLCAnd XMAB、XMBC、XMCAAn unknown number;
the fifth step: solving six equations to obtain the values of the six inductive reactance, thereby obtaining the coupling inductive reactance among the self inductive reactance of the tested line;
step two: the method utilizes the induction current to complete the passive measurement of the line, and comprises the following small steps:
the first step is as follows: keeping the phase A open circuit, measuring the phase A voltage, and insulating and short-circuiting the phase B and the phase C relative to the ground to form a loop, as shown in FIG. 3, for obtaining the self resistance of the line and the ground loop resistance;
the second step is that: measuring loop current i'BCAnd voltage u'AThey have the following relationships:
[2RS+j(XLB-XLC)]*i′BC＝u'BC (7)
wherein u'BCAs intermediate variables, it is alternatively possible to determine RSThe value of (d); in combination with R determined aboveG+RSThe sum of the ground resistance and the ground resistance of the ground loop can be obtained;
the third step: r can be obtained twice by sequentially insulating A, B relatively and A, C relativelySThe values of (a) and (b) are mutually verified;
the fourth step: at this moment, a passive measurement method is adopted, and parameters of the ground loop resistance, the self-inductance and the mutual inductance of the line can be calculated by only measuring the induced voltage and the induced current of the tested line under different conditions.
Preferably, in the fifth step of the first step, the longer the distance between the tested line and the live power transmission line is, the larger the induced current is; the larger the current transmitted by other live transmission lines is, the larger the induced current is; the closer the other transmission lines are spatially distant from the line under test, the larger the induced current is.
Preferably, in the fifth step, the open-circuit induced voltages generated in the three-phase line of the tested line have the characteristics of same phase and fixed ratio.
Preferably, in the fifth step, the tested line has a large induced current to the ground, because other live operating electrical equipment, especially other live power transmission lines, exist around the tested line.
Preferably, in the second step, the passive measurement is based on a power frequency induced voltage and an induced current generated in the tested line by other nearby live-line operation equipment due to electromagnetic induction.
Preferably, in the second and fourth steps, because other live-line-operated electrical devices, especially transmission lines parallel to the tower, which cause the tested line to generate induced voltage and current, have relatively fixed positions on the tested line, the degree of influence of electromagnetic fields excited by the electrical devices on the three-phase line of the tested line is relatively constant.
The invention has the beneficial effects that: the passive measurement method for the parameters of the overhead transmission line does not need an external pilot frequency power supply or other test power supplies, and fully utilizes induced voltage and induced current generated in the line by other running lines or electrical equipment existing around the tested line to obtain corresponding line parameters. The method fully utilizes the strong electromagnetic environment around the tested line, and perfectly solves the problem that the normal measurement is difficult to carry out due to the fact that the induced current of the tested line is too large or the induced voltage is too high when the traditional method adopts a pilot frequency power supply to carry out the parameter measurement work of the overhead line.
The invention can be widely applied to passive measurement occasions.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, but rather the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A passive measurement method for overhead transmission line parameters is characterized by comprising the following steps:
the method comprises the following steps: obtaining the relative relation of the three-phase induced voltages of the tested line, comprising the following steps:
the first step is as follows: under the condition that one end of a tested three-phase overhead transmission line is grounded and the other end of the tested three-phase overhead transmission line is open, the open-circuit voltage of a three-phase line is measured simultaneously;
with phase A as reference, its open circuit voltage vector is marked as UAThe angle is 0 degrees, and the B-phase open-circuit voltage vector is recorded as UBThe open-circuit voltage vector of the C phase is recorded as UC∠β°；
The relative position of the current source of the excitation electromagnetic field is not changed, so that a three-phase circuit U is obtainedA、UBAnd UCThe relative ratio of (A) and (B) is kept unchanged;
by UA、UBAnd UCCalculating to obtain the ratio K of the threeAB、KBC、KCA：
KAB＝UA/UB (1)
KBC＝UB/UC (2)
KCA＝UC/UA (3)
The second step is that: after obtaining the open-circuit voltages of the three-phase lines, sequentially short-circuiting one of the three-phase lines to the ground, keeping the other two open circuits, and measuring the state of the induced voltage;
the third step: short-circuiting the phase C to the ground, keeping the phases A and B open, measuring the induced current of the phase C, and obtaining the induced current i of the phase CcAnd A, B phase induction voltage uAAnd uB；
(RG+RSC+jXLC)*ic＝uc (4)
uC＝KCA(uA-icXMCA) (5)
uC＝(uB-icXMCB)/KBC (6)
Wherein R isGIs the earth return resistance, RSA、RSBAnd RSCRespectively the self-resistance, X, of each phase lineLA、XLBAnd XLCAre the self-inductance, X, of each phaseMAB、XMBCAnd XMCARespectively are mutual inductance among all phase circuits; by the characteristics of the circuit structureKnown as RSA、RSBAnd RSCHaving a numerically equal relationship, R will be used laterSDirect substitution;
from the above formula, R is obtainedG+RSSum of (A) and XLC+KCAXMCAThe sum of (1);
in the same way, X is obtainedLC+XMCB/KBCThe sum of (1);
the fourth step: respectively and independently short-circuiting the phases B and A to the ground in sequence to obtain XLB+KCBXMBC、XLB+XMAB/KABAnd XLA+KABXMAB、XLA+XMCA/KCAThe sum of the six inductive reactance results, corresponding to the six inductive reactance XLA、XLB、XLCAnd XMAB、XMBC、XMCAAn unknown number;
the fifth step: solving six equations to obtain the values of the six inductive reactance, thereby obtaining the mutual inductance between each phase of the self inductive reactance of the tested line;
step two: the method utilizes the induction current to complete the passive measurement of the line, and comprises the following small steps:
the first step is as follows: keeping the phase A open circuit, and insulating and short-circuiting the phase B and the phase C relative to the ground to form a loop for obtaining the self resistance of the line and the ground loop resistance;
the second step is that: measuring loop induced current i'BCAnd an induced voltage u'AThey have the following relationships:
[2RS+j(XLB-XLC)]*i′BC＝u'BC (7)
wherein u'BCFor intermediate variables, alternatively, R is determinedSThe value of (d); in combination with R determined aboveG+RSThe sum of the ground loop resistance value and the ground loop resistance value is obtained;
the third step:successively, A, B and A, C are insulated and shorted to obtain RSThe values of (a) and (b) are mutually verified;
the fourth step: at this moment, a passive measurement method is adopted, and the ground loop resistance, the self inductance and the mutual inductance parameter of the line can be calculated by only measuring the induced voltage and the induced current of the tested line under different conditions.
2. The passive measurement method for the parameters of the overhead transmission line according to claim 1, characterized in that the longer the distance of the tested line parallel to the live transmission line, the larger the induced current; the larger the current transmitted by other live transmission lines is, the larger the induced current is; the closer the other transmission lines are spatially distant from the line under test, the larger the induced current is.
3. The passive measurement method for the parameters of the overhead transmission line according to claim 2, characterized in that the induced voltages generated in the three-phase line of the tested line have the characteristics of same phase and fixed ratio.
4. The passive measurement method for the parameters of the overhead transmission line according to claim 3, characterized in that the tested line has a large induced current in itself due to the presence of other live-running electrical equipment around it.
5. The passive measurement method for the parameters of the overhead transmission line according to claim 1, characterized in that the passive measurement is based on power frequency induced voltage and induced current generated in the tested line by other nearby live-line running equipment due to electromagnetic induction.
6. The passive measurement method for the parameters of the overhead transmission line according to claim 1, wherein other live-running electrical devices which cause the tested line to generate induced voltage and current have relatively fixed positions on the tested line by the transmission lines which are parallel to the tower, and the influence degree of the electromagnetic field excited by the transmission lines on the three-phase line of the tested line is relatively constant.
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