CN110212489B - High-voltage direct-current line distance protection method based on criterion extreme value estimation - Google Patents
High-voltage direct-current line distance protection method based on criterion extreme value estimation Download PDFInfo
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- CN110212489B CN110212489B CN201910416794.2A CN201910416794A CN110212489B CN 110212489 B CN110212489 B CN 110212489B CN 201910416794 A CN201910416794 A CN 201910416794A CN 110212489 B CN110212489 B CN 110212489B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/34—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system
- H02H3/353—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system involving comparison of phase voltages
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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Abstract
The invention discloses a high-voltage direct current line distance protection method based on criterion extreme value estimation, which comprises the following steps: when a line has a fault, respectively acquiring the measured current and the measured voltage of the pn pole, the p pole and the n pole which are subjected to low-pass filtering; searching line parameters within a line parameter error range according to the p pole, the n pole and the pn pole measuring current; respectively calculating the maximum value and the minimum value of voltage drop between the p pole, the n pole and the pn pole; respectively calculating the maximum value of the voltage ratio of the p-pole line, the n-pole line and the pn-pole line; judging whether the p-pole line, the n-pole line and the pn-pole line have short-circuit faults or not according to the positive and negative of the maximum voltage ratio of the p-pole line, the n-pole line and the pn-pole line; the invention can solve the problem that the distance protection of the high-voltage direct-current line generates misoperation when the line parameters have errors.
Description
Technical Field
The invention belongs to the technical field of relay protection of power systems, and particularly relates to a high-voltage direct-current line distance protection method based on criterion extreme value estimation.
Background
The high voltage direct current transmission system (HVDC) has large transmission capacity, low line loss, obvious technical advantages and environmental protection performance. When the high-voltage direct-current line has transient fault and protection action, the fault restarting device is used for clearing the fault and recovering power transmission without isolating the whole system. Therefore, the protection of the direct current line is important for guaranteeing the safe and stable operation of the system.
The high-voltage direct-current transmission line mainly takes traveling wave protection and differential undervoltage protection as main protection at present and longitudinal current differential protection as backup protection. However, these protections all have various disadvantages, such as higher sampling rate requirement of traveling wave protection, difficulty in measuring wave head, low sensitivity of differential undervoltage protection, and poor selectivity, and the setting of the threshold value of the protection all depend on the exhaustive simulation. The longitudinal current differential protection needs a longitudinal communication channel to exchange double-end electric quantity, and has lower reliability and slower action speed. The distance protection based on the differential equation algorithm is an ideal protection scheme for the direct-current line, only needs the measurement information of the local side, can respond to various fault types, has a stable protection range, and is not influenced by the operation mode of the system.
However, the existing direct current line distance protection methods do not consider the influence of line parameter errors on protection selectivity. The length of a direct current line reaches thousands of kilometers, and line parameters inevitably deviate from the true values under the influence of environment and measurement errors, so that the distance protection criterion calculated on the basis has large errors, and the protection is prone to misoperation when the protection is in an out-of-range fault.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-voltage direct-current line distance protection method based on criterion extreme value estimation, and aims to solve the problem of maloperation caused by the fact that line parameter errors are not considered in the conventional high-voltage direct-current line protection.
In order to achieve the above object, the present invention provides a distance protection method for a high voltage direct current line based on criterion extremum estimation, comprising:
(1) when a line has a fault, respectively acquiring the measured current and the measured voltage of the pn pole, the p pole and the n pole which are subjected to low-pass filtering;
(2) according to the measured currents of the p pole, the n pole and the pn pole, searching line parameters which enable the voltage drop of the p pole, the n pole and the pn pole to be a maximum value and a minimum value within a line parameter error range;
(3) respectively calculating the maximum value and the minimum value of voltage drop among the p pole, the n pole and the pn pole according to the line parameters and the measured currents among the p pole, the n pole and the pn pole;
(4) respectively calculating the maximum value and the minimum value of the voltage drop of the compensation voltage among the p pole, the n pole and the pn pole, and respectively calculating the maximum value of the voltage ratio among the p pole line, the n pole line and the pn pole line;
(5) judging whether the p-pole line, the n-pole line and the pn-pole line have short-circuit faults or not according to the positive and negative of the maximum voltage ratio of the p-pole line, the n-pole line and the pn-pole line;
and the voltage drops among the p pole, the n pole and the pn pole are voltage drops among the p pole, the n pole and the pn pole measuring point and the corresponding set point respectively.
Preferably, the measuring point of the p-pole measuring current and the measuring point of the p-pole measuring voltage is the installation position of the first relay protection device of the p-pole line;
and the measuring point of the measuring current and the measuring voltage of the n pole is the installation position of the first relay protection device of the n pole line.
Preferably, the line parameters include: resistance parameters of the line unit length corresponding to the voltage drop maximum value and the minimum value, and inductance parameters of the line unit length corresponding to the voltage drop maximum value and the minimum value;
the method for searching the line parameters in the step (2) comprises the following steps:
if the measured current of the line is greater than 0 and the measured current change rate of the line is greater than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ 1+ a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1+ a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1-a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1-a%) l;
if the measured current of the line is greater than 0 and the measured current change rate of the line is less than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ 1+ a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1-a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1-a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1+ a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is greater than 0, the line unit length resistance corresponding to the voltage drop maximum is: r' ═ (1-a%) r; the inductance of the line unit length corresponding to the maximum value of the voltage drop is as follows: l ═ (1+ a%) l; the line unit length resistance corresponding to the voltage drop minimum value is: r ″ (1+ a%) r; the line unit length inductance corresponding to the voltage drop minimum is: l ═ (1-a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is less than 0, the line unit length resistance corresponding to the voltage drop maximum is: r' ═ (1-a%) r; the inductance of the line unit length corresponding to the maximum value of the voltage drop is as follows: l ═ (1-a%) l; the line unit length resistance corresponding to the voltage drop minimum value is: r ″ (1+ a%) r; the line unit length inductance corresponding to the voltage drop minimum is: l ═ (1+ a%) l;
wherein r and l are respectively given values of the resistance and inductance parameters of the unit length of the direct current line; a% is the relative error of the parameter; the lines include a p-pole line, an n-pole line and a pn-pole line.
The maximum value and the minimum value of the voltage drop of the p pole are respectively as follows:
the maximum value and the minimum value of the voltage drop of the n pole are respectively as follows:
the maximum value and the minimum value of the voltage drop between pn electrodes are respectively:
wherein, Δ up_max(t)、Δup_min(t) represents the maximum and minimum values of the voltage drop of the p-line; Δ un_max(t)、Δun_min(t) represents the maximum and minimum values of the voltage drop of the n-line; Δ u1_max(t)、Δu1_min(t) represents the maximum and minimum values of the interpolar voltage drop, ip(t)、in(t)、i1(t) measuring currents for the p pole, the n pole and the interelectrode respectively; lsetSetting distance; r's、rs"line unit length self-resistance corresponding to voltage drop maximum and minimum respectively; ls′、ls"self inductance of line unit length corresponding to maximum and minimum of voltage drop, respectively; lm′、lm"mutual inductance of line unit length corresponding to maximum and minimum values of voltage drop, rm′、rm"line cell length mutual resistance corresponding to voltage drop maximum and minimum values, respectively.
Preferably, the maximum value of the voltage ratio of the p-pole line is:
the maximum value of the voltage ratio of the n-pole line is as follows:
the maximum value of the voltage ratio of the pn pole circuit is as follows:
wherein R isp_max(t) represents the maximum value of the voltage ratio of the p-pole line, upM(t) represents the filtered measurement voltage of the p-line; rn_max(t) represents the maximum value of the voltage ratio of the n-pole line, unM(t) represents the filtered measurement voltage of the n-line; r1_max(t) represents the maximum value of the voltage ratio between pn-pole lines, u1M(t) represents the filtered interelectrode measurement voltage; Δ up_max(t)、Δup_min(t) a maximum value and a minimum value of the voltage drop of the p-pole are respectively represented; Δ un_max(t)、Δun_min(t) a maximum value and a minimum value of the voltage drop of the n-pole are respectively represented; Δ u1_max(t)、Δu1_min(t) represents the maximum value and the minimum value of the voltage drop between pn electrodes, respectively.
Preferably, the method of determining whether or not a short-circuit fault occurs in the p-electrode line, the n-electrode line, and the pn-electrode line includes:
if the maximum value of the voltage ratio of the p-pole line is positive and negative, judging that the p-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the n-pole line is positive and negative, judging that the n-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the pn-pole circuit is positive or negative, it is determined that a short-circuit fault has occurred in the pn-pole circuit.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
according to the measured current at the protection installation position of the high-voltage direct-current line and the instantaneous polarity of the current change rate, line parameters which enable the voltage drop between the measuring point between the p pole, the n pole and the pn pole of the direct-current line and the voltage drop between the whole points to be extreme values are searched in the error range of the line parameters, and the respective voltage drop extreme values are calculated based on the line parameters and the measured voltage and current after low-pass filtering. On the basis, the maximum value of the ratio of the compensation voltage to the measured voltage between the p pole, the n pole and the pn pole of the direct current line, namely the maximum value of the voltage ratio, is further calculated respectively, and the faults inside and outside the high-voltage direct current line area are judged by utilizing the positive and negative of the maximum value of the voltage ratio. The high-voltage direct-current line distance protection method based on criterion extreme value estimation can well solve the problem that the existing high-voltage direct-current line distance protection is prone to misoperation when line parameters have errors.
Drawings
Fig. 1 is a schematic flow chart of a distance protection method for a high-voltage direct-current line based on criterion extreme value estimation according to the present invention;
fig. 2 is a schematic structural diagram of a high voltage direct current transmission system provided by the present invention;
FIG. 3 is a schematic structural diagram of a +/-800 kv high-voltage direct-current transmission system provided by the invention;
FIG. 4 is a curve of the maximum value of the p-line voltage ratio when the p-line has a short circuit fault according to the present invention;
FIG. 5 is a curve of the maximum voltage ratio of the n-line when the n-line is short-circuited;
FIG. 6 is a variation curve of the maximum p-line voltage ratio, the maximum n-line voltage ratio, and the maximum pn-pole voltage ratio when a three-phase short circuit fault occurs according to the present invention;
description of the drawings:
1-rectifying side system; 2-p polar line first bus; 3-n polar line first bus; a 4-p polar line first relay protection device; 5-n polar line first relay protection device; a 6-p pole line; a 7-n pole line; 8-p polar line second relay protection device; 9-n polar line second relay protection device; a 10-p polar line second bus; 11-n polar line second bus; 12-inversion side system.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a distance protection method based on criterion extreme value estimation, which is suitable for a high-voltage direct-current line and aims to solve the problems that the distance protection of the existing high-voltage direct-current line lacks a misoperation prevention method for scientifically and effectively coping with line parameter errors and the like. The method can solve the problems that the distance protection of the existing high-voltage direct-current line lacks a method for preventing misoperation for scientifically and effectively coping with line parameter errors and the like by utilizing the positive and negative judgment of the voltage ratio of the two-pole direct-current line to determine the faults inside and outside the line area.
In the embodiment of the invention, instantaneous values obtained after low-pass filtering is carried out on single-ended measurement quantities of the high-voltage direct-current line are utilized, line parameters enabling voltage drops between the p-pole measuring point, the n-pole measuring point and the inter-pole measuring point and the whole point to be extreme values are searched in a line parameter error range, the extreme values of the voltage drops are calculated, the maximum value of the pressure ratio among the p-pole measuring point, the n-pole measuring point and the inter-pole measuring point is further calculated, and faults inside and outside the high-voltage direct-current line area are judged by utilizing the positive and. If the p-pole line voltage ratio maximum value changes from positive to negative after the fault, the p-pole line is judged to have a short circuit fault; if the voltage ratio maximum value of the n-pole line is changed from positive to negative after the fault, the n-pole line is judged to have a short-circuit fault; when the "maximum pn interelectrode voltage ratio" changes from positive to negative after the fault, it is determined that an interelectrode short-circuit fault has occurred in the dc line. The method has the advantages of low requirement on the sampling rate, simple criterion, high action speed, high reliability, independence of simulation on setting basis, capability of preventing the maloperation of the distance protection of the direct current line when the line parameters have errors, capability of solving the problem that the distance protection of the existing high-voltage direct current line lacks a maloperation preventing method for scientifically and effectively coping with the line parameter errors and the like, and universality.
As shown in fig. 1, the present invention provides an extreme value estimation-based distance protection method for a high voltage direct current line, including:
(1) when a line has a fault, respectively acquiring the measured current and the measured voltage of the pn pole, the p pole and the n pole which are subjected to low-pass filtering;
specifically, when a line fails, starting the fault starting element through a p-pole line first relay protection device and an n-pole line first relay protection device, acquiring voltage and current information of the installation position of the p-pole line first relay protection device in a direct-current power transmission system, sending the voltage and current information to a signal processing unit for p-pole line protection for data processing, acquiring voltage and current information of the installation position of the n-pole line first relay protection device in the direct-current power transmission system, and sending the voltage and current information to the signal processing unit for n-pole line protection for data processing;
to p poleThe signal processing cutoff frequency of the line protection signal processing unit is fcLow-pass filtering of (1), the filtered measurement voltage and measurement current being respectively denoted as upM(t) and ip(t) the signal processing cutoff frequency of the n-line protection signal processing unit is fcLow-pass filtering of (1), the filtered measurement voltage and measurement current being respectively denoted as unM(t) and in(t)；
(2) According to the measured currents of the p pole, the n pole and the pn pole, searching line parameters which enable the voltage drop of the p pole, the n pole and the pn pole to be a maximum value and a minimum value within a line parameter error range;
specifically, the line parameters include: the resistance value of the line unit length corresponding to the maximum value and the minimum value of the voltage drop, and the inductance value of the line unit length corresponding to the maximum value and the minimum value of the voltage drop.
The specific method for searching the line parameters comprises the following steps: if the measured current of the line is greater than 0 and the measured current change rate of the line is greater than 0, the resistance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: r' ═ 1+ a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: l ═ (1+ a%) l; the resistance parameter values of the line unit length corresponding to the voltage drop minimum value are as follows: r ″ (1-a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop minimum value is as follows: l ═ (1-a%) l;
if the measured current of the line is greater than 0 and the measured current change rate of the line is less than 0, the resistance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: r' ═ 1+ a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: l ═ (1-a%) l; the resistance parameter values of the line unit length corresponding to the voltage drop minimum value are as follows: r ″ (1-a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop minimum value is as follows: l ═ (1+ a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is greater than 0, the resistance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: r' ═ (1-a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: l ═ (1+ a%) l; the resistance parameter values of the line unit length corresponding to the voltage drop minimum value are as follows: r ″ (1+ a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop minimum value is as follows: l ═ (1-a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is less than 0, the resistance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: r' ═ (1-a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop maximum is as follows: l ═ (1-a%) l; the resistance parameter values of the line unit length corresponding to the voltage drop minimum value are as follows: r ″ (1+ a%) r; the inductance parameter value of the line unit length corresponding to the voltage drop minimum value is as follows: l ═ (1+ a%) l;
the circuit comprises a p-pole circuit, an n-pole circuit and a pn interelectrode circuit;
wherein r and l are respectively given values of the resistance and inductance parameters of the unit length of the direct current line; a% is the relative error of the parameter.
(3) Respectively calculating the maximum value and the minimum value of voltage drop among the p pole, the n pole and the pn pole according to the line parameters and the measured currents among the p pole, the n pole and the pn pole;
and the voltage drops among the p pole, the n pole and the pn pole are voltage drops among the p pole, the n pole and the pn pole measuring point and the corresponding set point respectively.
Specifically, the maximum value and the minimum value of the voltage drop of the p pole are respectively:
the maximum value and the minimum value of the voltage drop of the n pole are respectively as follows:
the maximum value and the minimum value of the voltage drop between the pn electrodes are respectively as follows:
wherein, Δ up_max(t)、Δup_min(t) represents the maximum and minimum values of the voltage drop of the p-line; Δ un_max(t)、Δun_min(t) represents the maximum and minimum values of the voltage drop of the n-line; Δ u1_max(t)、Δu1_min(t) represents the maximum and minimum values of the interpolar voltage drop, ip(t)、in(t)、i1(t) measuring currents for the p pole, the n pole and the interelectrode respectively; lsetSetting distance; r's、rs"line unit length self-resistance corresponding to voltage drop maximum and minimum respectively; ls′、ls"self inductance of line unit length corresponding to maximum and minimum of voltage drop, respectively; lm′、lm"mutual inductance of line unit length corresponding to maximum and minimum values of voltage drop, rm′、rm"line cell length mutual resistance corresponding to voltage drop maximum and minimum values, respectively.
(4) Respectively calculating the maximum value and the minimum value of the voltage drop among the p pole, the n pole and the pn pole according to the maximum value and the minimum value of the voltage drop among the p pole, the n pole and the pn pole;
specifically, the maximum value of the voltage ratio of the p-pole line is:
the maximum value of the voltage ratio of the n-pole line is as follows:
the maximum value of the voltage ratio of the pn pole circuit is as follows:
wherein R isp_max(t) represents the maximum value of the voltage ratio of the p-pole line, upM(t) represents the filtered measurement voltage of the p-line; rn_max(t) represents the maximum value of the voltage ratio of the n-pole line, unM(t) represents the filtered measurement voltage of the n-line; r1_max(t) represents the maximum value of the voltage ratio between pn-pole lines, u1M(t) represents the filtered interelectrode measurement voltage; Δ up_max(t)、Δup_min(t) a maximum value and a minimum value of the voltage drop of the p-pole are respectively represented; Δ un_max(t)、Δun_min(t) a maximum value and a minimum value of the voltage drop of the n-pole are respectively represented; Δ u1_max(t)、Δu1_min(t) a maximum value and a minimum value of a voltage drop between pn poles are represented, respectively;
(5) judging whether the p-pole line, the n-pole line and the pn-pole line have short-circuit faults or not according to the positive and negative of the maximum voltage ratio of the p-pole line, the n-pole line and the pn-pole line;
specifically, the method for determining whether a short-circuit fault occurs in the p-electrode line, the n-electrode line, and the pn-electrode line includes:
if the maximum value of the voltage ratio of the p-pole line is positive and negative, judging that the p-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the n-pole line is positive and negative, judging that the n-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the pn-pole circuit is positive or negative, it is determined that a short-circuit fault has occurred in the pn-pole circuit.
For further explanation of the novel distance protection method for the high-voltage direct-current line based on criterion extreme value estimation provided by the embodiment of the present invention, the following is detailed with reference to the accompanying drawings and specific examples:
as shown in fig. 2, a ± 800kv hvdc transmission system comprises: a rectification side system 1, a p polar line first bus 2, an n polar line first bus 3, a p polar line first relay protection device 4, an n polar line first relay protection device 5, a p polar line 6, an n polar line 7, a p polar line second relay protection device 8, an n polar line second relay protection device 9, a p polar line second bus 10, an n polar line second bus 11, an inversion side system 12, wherein the rectification side system 1 is connected with the p polar line first bus 2 and the n polar line first bus 3, the p polar line first bus 2 is connected with the p polar line second bus 10 through the p polar line 6, the n polar line first bus 5 is connected with the n polar line second bus 11 through the n polar line 7, the p polar line second bus 10 and the n polar line second bus 11 are connected with the inversion side system 12, the p polar line first relay protection device 4 is arranged at the outlet of the p polar line first bus 2, the n-pole line first relay protection device 5 is installed at the outlet of the n-pole line first bus 3, the p-pole line second relay protection device 8 is installed at the outlet of the p-pole line second bus 10, and the n-pole line second relay protection device 9 is installed at the outlet of the n-pole line second bus 11.
By using the provided extreme value estimation-based high-voltage direct-current line distance protection method, the measurement point of the p-pole measurement current and the measurement point of the p-pole measurement voltage are the installation positions of the p-pole line first relay protection devices 4; the measuring point of the measuring current and the measuring voltage of the n pole is the installation position of the first relay protection device 5 of the n pole line; setting distance l of distance protectionset1300km, and the sampling interval delta t of the measuring current and the measuring voltage of the line is 0.1 ms;
as shown in fig. 3, the first relay protection device 4 provided with the p-pole line has a short-circuit to ground fault at the near-positive end (f in fig. 3)1Point), the maximum value of the voltage ratio of the p-pole line is shown in FIG. 4, formula Rp_max(i)<If 0 is established, it is determined that a p-line internal short-circuit fault has occurred.
As shown in FIG. 3, the far end of the n-line is set to have a ground short fault (f in FIG. 3)2Point), n-line voltage ratio maximum as shown in FIG. 5, formula Rn_max(i)<If 0 is established, it is determined as an n-line internal short-circuit fault.
As shown in FIG. 3, the inverter-side system is set to generate a three-phase symmetrical ground short circuit fault (f in FIG. 3)3Point), maximum value of p-line voltage ratio, maximum value of n-line voltage ratioAnd maximum value of interelectrode voltage ratio as shown in FIG. 6, Rp_max(i)>0，Rn_max(i)>0，R1_max(i)>And 0, judging that the line has an external fault.
Referring to fig. 4, 5 and 6, fig. 4 shows that the positive near end of the first relay protection device 4 of the p-line of the ± 800kv high-voltage direct-current transmission system of the invention has a short-circuit fault (f)1) The "p extreme pressure ratio maximum value" change curve; FIG. 5 shows a + -800 kv HVDC transmission system according to the invention with a ground short-circuit fault (f) at the far end of the n-line2) The variation curve of the 'n extreme pressure ratio maximum value'; FIG. 6 shows that the + -800 kv HVDC transmission system of the present invention has three-phase symmetrical grounding short circuit fault (f) on the inversion side system3) The variation curve of the maximum value of the p-polar line pressure ratio, the maximum value of the n-polar line pressure ratio and the maximum value of the interelectrode pressure ratio is obtained; as can be seen from fig. 4 to fig. 6, the novel distance protection method for the high-voltage direct-current line based on criterion extreme value estimation provided by the embodiment of the invention can effectively judge the internal and external faults of the line.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A high-voltage direct-current line distance protection method based on criterion extreme value estimation is characterized by comprising the following steps:
(1) when a line has a fault, respectively acquiring the measured current and the measured voltage of the pn pole, the p pole and the n pole which are subjected to low-pass filtering;
(2) according to the measured currents of the p pole, the n pole and the pn pole, searching line parameters which enable the voltage drop of the p pole, the n pole and the pn pole to be maximum and minimum values within the error range of the line parameters;
(3) respectively calculating the maximum value and the minimum value of voltage drop between the p pole, the n pole and the pn pole according to the line parameters and the measured currents between the p pole, the n pole and the pn pole;
(4) calculating the maximum value and the minimum value of the voltage drop among the p pole, the n pole and the pn pole, and the maximum value of the voltage ratio among the p pole line, the n pole line and the pn pole line according to the measured voltages of the pn pole, the p pole and the n pole after low-pass filtering;
(5) judging whether the p-pole line, the n-pole line and the pn-pole line have short-circuit faults or not according to the positive and negative of the maximum voltage ratio of the p-pole line, the n-pole line and the pn-pole line;
and the voltage drops among the p pole, the n pole and the pn pole are voltage drops among the p pole, the n pole and the pn pole measuring point and the corresponding set point respectively.
2. The high-voltage direct-current line distance protection method of claim 1, wherein a measurement point of the p-pole measurement current and the p-pole measurement voltage is a first relay protection device installation position of the p-pole line; and the measuring point of the measuring current and the measuring voltage of the n pole is the installation position of the first relay protection device of the n pole line.
3. The high voltage direct current line distance protection method of claim 1 or 2, characterized in that the line parameters comprise: the resistance value of the line unit length corresponding to the maximum value and the minimum value of the voltage drop, and the inductance value of the line unit length corresponding to the maximum value and the minimum value of the voltage drop.
4. The high-voltage direct current line distance protection method of claim 3, wherein the method for searching line parameters in step (2) is as follows:
if the measured current of the line is greater than 0 and the measured current change rate of the line is greater than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ 1+ a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1+ a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1-a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1-a%) l;
if the measured current of the line is greater than 0 and the measured current change rate of the line is less than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ 1+ a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1-a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1-a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1+ a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is greater than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ (1-a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1+ a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1+ a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1-a%) l;
if the measured current of the line is less than 0 and the measured current change rate of the line is less than 0, the resistance value of the line unit length corresponding to the voltage drop maximum is: r' ═ (1-a%) r; the inductance value of the line unit length corresponding to the voltage drop maximum is: l ═ (1-a%) l; the resistance value of the length of the circuit unit corresponding to the minimum value of the voltage drop is as follows: r ″ (1+ a%) r; the inductance value of the line unit length corresponding to the minimum voltage drop value is as follows: l ═ (1+ a%) l;
the circuit comprises a p-pole circuit, an n-pole circuit and a pn interelectrode circuit;
wherein r and l are respectively given values of the resistance and inductance parameters of the unit length of the direct current line; a% is the relative error of the parameter.
5. The HVDC line distance protection method of claim 4, wherein the maximum and minimum values of the voltage drop of the p pole are respectively:
the maximum value and the minimum value of the voltage drop of the n pole are respectively as follows:
the maximum value and the minimum value of the voltage drop between the pn electrodes are respectively as follows:
wherein, Δ up_max(t)、Δup_min(t) represents the maximum and minimum values of the voltage drop of the p-line; Δ un_max(t)、Δun_min(t) represents the maximum and minimum values of the voltage drop of the n-line; Δ u1_max(t)、Δu1_min(t) represents the maximum and minimum values of the interpolar voltage drop, ip(t)、in(t)、i1(t) measuring currents for the p pole, the n pole and the interelectrode respectively; lsetSetting distance; r iss′、rs"is the self-resistance of the line unit length corresponding to the maximum value and the minimum value of the voltage drop respectively; ls′、ls"self inductance of line unit length corresponding to maximum and minimum of voltage drop respectively; lm′、lm"mutual inductance of line unit length corresponding to maximum and minimum values of voltage drop, rm′、rm"is the mutual resistance of the line unit length corresponding to the maximum value and the minimum value of the voltage drop respectively.
6. The high-voltage direct-current line distance protection method according to claim 4 or 5, characterized in that the maximum value of the voltage ratio of the p-pole line is:
the maximum value of the voltage ratio of the n-pole line is as follows:
the maximum value of the voltage ratio of the pn interelectrode line is as follows:
wherein R isp_max(t) represents the maximum value of the voltage ratio of the p-pole line, upM(t) represents the filtered measurement voltage of the p-line; rn_max(t) represents the maximum value of the voltage ratio of the n-pole line, unM(t) represents the filtered measurement voltage of the n-line; r1_max(t) represents the maximum value of the voltage ratio of the pn interelectrode wiring, u1M(t) represents the filtered interelectrode measurement voltage; Δ up_max(t)、Δup_min(t) a maximum value and a minimum value of the voltage drop of the p-pole are respectively represented; Δ un_max(t)、Δun_min(t) a maximum value and a minimum value of the voltage drop of the n-pole are respectively represented; Δ u1_max(t)、Δu1_min(t) represents the maximum value and the minimum value of the voltage drop between pn electrodes, respectively.
7. The high-voltage direct-current line distance protection method of claim 6, wherein the method for judging whether short-circuit faults occur in the p-pole line, the n-pole line and the pn-pole line is as follows:
if the maximum value of the voltage ratio of the p-pole line is positive and negative, judging that the p-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the n-pole line is positive and negative, judging that the n-pole line has a short-circuit fault; if the maximum value of the voltage ratio of the pn interelectrode line is positive or negative, it is determined that a short-circuit fault has occurred in the pn interelectrode line.
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