CN103956713B - A kind of protection of direct current supply line configuration setting method considering electromagnetic coupled relation - Google Patents

Abstract

The invention discloses a DC transmission line protection configuration setting method considering the electromagnetic coupling relationship, including step 1: line fault analysis and judgment; step 2: protection start; step 3: pole selection logic; step 4: interference elimination; step 5: Boundary judgment. The invention objectively and accurately considers the possible occurrence of faults in high-voltage direct current transmission lines, and considers the influence of faulty poles on normal poles caused by the electromagnetic coupling relationship between pole lines, and makes up for the problem of insufficient comprehensive protection in the prior art. It is necessary to adjust the logic on the basis of replacing the hardware of the original line protection. The engineering availability is strong, which improves the anti-interference ability of HVDC transmission line protection against possible malfunctions due to electromagnetic coupling, and enhances the sensitivity to line faults. and effectiveness, and realize the unification of technology and economy, reliability and sensitivity of HVDC line protection engineering.

Description

A Setting Method for Protection Configuration of DC Transmission Lines Considering Electromagnetic Coupling

technical field

The invention belongs to the field of electric power system transmission, and in particular relates to a DC transmission line protection configuration setting method considering electromagnetic coupling relationship.

Background technique

With the development of my country's electric power industry, the application of high-voltage direct current transmission technology in long-distance power transmission projects is becoming more and more extensive. According to statistics, as of 2006, about 98 direct current transmission projects have been put into operation around the world. China's high-voltage direct current transmission technology only started in the 1980s, but it has developed rapidly. At present, there are 5 HVDC projects under construction in my country, as shown in Table 1-1. From 1987 when the Zhoushan DC transmission project was put into operation until August 2010, there are 15 DC transmission projects that have been completed and put into operation in my country. With the Yunnan-Guangdong ±800kV UHV DC project of China Southern Power Grid in June 2010 and the State Grid Xiangjiaba-Shanghai ±800kV UHV DC project in July 2010, my country has become the country with the highest voltage level in the world, transmission The country with the largest capacity and the most advanced UHV DC transmission project.

There is electromagnetic coupling between the DC lines, and the coupling relationship between the conductors of each pole will not seriously affect the steady-state operation of the DC system. It will affect other normal operating pole conductors due to electromagnetic coupling relationship and unbalanced line parameters. In the grid planning stage, the electromagnetic coupling relationship between the DC transmission lines is not fully considered. The electromagnetic coupling relationship between the lines often leads to the electromagnetic coupling malfunction between the lines, which brings great challenges to the safe and reliable operation of the DC transmission system. The four bipolar blocking accidents that have occurred in the Tianguang DC transmission project since the bipolar poles were put into operation in 2001, and the "8.19" Yunguang UHV DC bipolar blocking accidents have a certain relationship with the electromagnetic coupling between lines.

In the actual operation of DC transmission lines, the arrangement of the transmission lines will cause a variety of electromagnetic coupling relationships between the lines, as well as possible faults on the lines, such as: direct lightning strikes, lightning shielding strikes, small resistance ground faults, high resistance ground fault etc. When one side of the line fails, the line transient fluctuation will have a corresponding impact on the normal side through the electromagnetic coupling relationship between the lines and cause fluctuations on the entire DC transmission system, which has become an important part of the DC transmission operation and maintenance work. .

In the current state of the art, there are problems in the protection of high-voltage DC lines, such as poor consideration of the electromagnetic coupling relationship between pole lines, normal pole malfunctions caused by electromagnetic coupling, and poor reliability of the DC system. The currently used DC transmission system is designed with insufficient DC operation experience, insufficient consideration of the actual situation of the line, and there are problems in the protection configuration, such as simple means, low sensitivity, and poor reliability. The DC system is blocked due to electromagnetic coupling. etc., all of which have serious impacts on the DC transmission system.

Contents of the invention

In view of the defects of the above-mentioned prior art, the present invention proposes a DC transmission line protection configuration setting method considering the electromagnetic coupling relationship, which solves the problem of faulty pole pairs caused by the electromagnetic coupling relationship between the pole lines in the high-voltage DC transmission protection technology in the prior art Normal pole impact problem.

The present invention fully considers the possible situations of various line faults, and the line action area mainly includes: line interval faults, reverse faults on the inverter side, bus and line faults on the AC side, and typical faults that may be caused by various disturbances; According to the fault type, it mainly includes: lightning counterattack, lightning shielding, lightning interference, metallic grounding, high resistance grounding and other faults. Considering that different faults have different response action characteristics, it is also necessary to consider the electromagnetic coupling relationship between pole lines. In the specific configuration, the possibility of faults and the influence of electromagnetic coupling between DC transmission lines on the transmission system are effectively considered, and the faults are grasped in a targeted manner. The present invention takes the actual engineering use as the starting point, considers the influence caused by the electromagnetic coupling relationship between the polar lines, and makes the protection can effectively deal with the electromagnetic coupling relationship as the main purpose, and effectively solves the protection caused by the electromagnetic coupling relationship to the DC transmission system Malfunction problem, so that the protection system can act sensitively, quickly and effectively.

In order to achieve the above purpose, the present invention adopts the following technical solutions: a DC transmission line protection configuration setting method considering the electromagnetic coupling relationship, comprising the following steps:

Step 1: Line fault analysis and judgment, determine the type of HVDC transmission line, and identify the corresponding fault of the line by the DC system;

Step 2: start the protection logic, calculate the voltage mutation by collecting the voltage change signal at the existing protection installation of the DC transmission line, if it exceeds the start threshold, start the protection logic and enter the next step;

Its criterion is:

In the formula, i represents the positive and negative poles of the DC transmission line, i=1, 2; _R and _I represent the rectification side and the inverter side respectively; threshold.

The judgment formula of the DC transmission line protection constituted by it is

In the formula, i, j represent the positive and negative poles of the double-circuit direct current transmission line, i=1,2,3,4; j=1,2,3,4; j≠i; M represents wavelet transformation processing on the signal; R and I represent the _{rectification side} and the inverter _side respectively; k _R1 is the setting value of the ratio of the sudden change of the _bipolar voltage on the _{rectification} side of the line; ), sign(MΔi _Ii ) represent the polarity of MΔi _Ri and MΔi _Ii respectively; sign(MΔu _Ri ) represents the polarity of the wavelet transform modulus maximum value of Δu _Ri ; Δu _Ri and Δu _Rj represent the rectification side i pole and j △i _Ri and △i _Ii represent the current variation of i-pole line on the rectification side and inverter side respectively;

Step 3: Pole selection logic. After the protection logic is started, the protection starts to calculate the ratio of the voltage mutation of the two poles. If the ratio exceeds k _R1 , it means that the fault is very local. For double-circuit lines, go to step 4 to eliminate interference; for single-circuit lines The line continues to carry out the protection logic. If the ratio of the two-pole voltage mutation exceeds k _R2 , it means that lightning interference has occurred on the DC line, and the protection resets; but if the ratio of the two-pole voltage mutation does not exceed k _R2 , it means that there is a fault on the line and enter Step five is to judge the boundary;

The k _R1 mentioned in step 3 is the setting value of the ratio of the sudden change of the voltage at the two poles, and k _R2 is the setting value of the ratio of the sudden change of the voltage used by the single-circuit line protection logic to distinguish lightning strike interference and lightning strike fault;

Step 4: Interference elimination and protection Perform wavelet transformation on △u _Ri to obtain the modulus maximum value of the wavelet transformation under the fifth scale (dB5). If it is negative, it means lightning interference, and the protection resets. Explain that it is not lightning interference, enter the boundary judgment;

Step 5: Boundary judgment, the protection reads the current signals of the rectification side and the inverter side, and performs wavelet transformation on the current signals, and judges whether to start the line protection according to the polarity of the modulus maximum value of the wavelet transformation on both sides; if both sides If the polarity of the wavelet transform modulus maximum of the current is opposite, the line protection will be activated, otherwise the protection will reset.

Among them: the means and methods for the fault distinction of single-circuit and double-circuit DC transmission lines on the same tower as described in step 1 are mainly based on the difference in voltage mutation to determine faulty lightning strikes and disturbing lightning strikes, AC faults and commutation failures, and line faults Faults inside and outside the protection zone, etc.

The sudden change in voltage mentioned in step 2 exceeds the fixed value, which is the artificially set parameter values k _R and k _I in combination with specific engineering parameters and operating experience, which are the starting thresholds of the protection criteria of the line rectifier side and inverter side respectively.

The wavelet transform described in step 4 refers to the modulus maximum value obtained based on the wavelet transform under the fifth scale.

The reading of the rectifier-side and inverter-side current signals by the protection described in step 5 is obtained by collecting the current variation signal at the protection installation place.

Compared with the prior art, the present invention has the following advantages:

1. It objectively and accurately considers the possible occurrence of HVDC transmission line faults, and considers the influence of faulty poles on normal poles caused by the electromagnetic coupling relationship between pole lines, making up for the lack of comprehensive protection in the existing problems;

2. It only needs to adjust the logic of the original line protection, and only needs to modify the software logic without replacing the hardware, so the engineering availability is strong;

3. Under the premise of ensuring the reliability of the protection action, the anti-interference ability of the high-voltage direct current transmission line protection against possible misoperation due to electromagnetic coupling is improved, and the sensitivity and effectiveness of line faults are enhanced to realize high-voltage direct current transmission The unity of technology and economy, reliability and sensitivity of line protection engineering.

Description of drawings

Accompanying drawing 1 is the schematic diagram of multi-fault response of HVDC transmission system;

Accompanying drawing 2 is a diagram of a DC transmission line protection configuration method considering the electromagnetic coupling relationship between pole lines.

detailed description

The content of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example:

As shown in Figure 1, it is known from engineering operation experience that possible faults in the HVDC transmission system include: line-side faults F1 and F2; rectification-side bus or converter station fault F_R; converter-side bus or converter station Fault F_I. When considering the faults of the entire DC system, the line faults considered need to be distinguished according to the line side and the distance on the line, and the line faults are divided into F1_1, F1_2, F1_3, F1_4. According to the polarity of the line fault, it is divided into F1 and F2. After a fault occurs, traveling waves and transient overvoltages often appear on the line. The capacitive effect between the high-voltage DC lines will cause electromagnetic coupling between the lines, and the voltage waveform that changes sharply on the fault side will pass through The electromagnetic coupling relationship produces a corresponding interference waveform on the normal side. Under the existing protection system, the electromagnetic coupling of the current line is not considered sufficiently, and it cannot effectively and sensitively deal with its impact on the entire DC transmission system.

Figure 2 is a diagram of the DC transmission line protection configuration method considering the electromagnetic coupling relationship between pole lines. The DC transmission line protection configuration method considering the electromagnetic coupling relationship between the pole lines is to consider the possible misoperation effects caused by the electromagnetic coupling relationship between the pole lines on the healthy pole under a variety of possible faults, and in order to Under the premise of the most effective and sensitive response, the most effective solution proposed. In the configuration diagram shown in Figure 2, the main configuration method is divided into five parts: Step 1, Step 2, Step 3, Step 4 and Step 5, respectively showing line fault analysis and judgment, protection startup, and pole selection logic , Interference exclusion and boundary determination.

In the line fault analysis and judgment in step 1, the different electromagnetic coupling relationships caused by different arrangements of DC transmission lines are mainly considered, and the main means of fault differentiation and determination are as follows:

a. Fault determination considering the electromagnetic coupling relationship between single-circuit DC transmission lines:

1) When a fault occurs on the single-circuit DC transmission line, the voltage change of the fault pole is the largest, and the fault pole is determined accordingly;

2) The polarity of the modulus maximum value of the current after wavelet transformation is not affected by the transition resistance, and the polarity of the modulus maximum value of the current wavelet transformation on the rectifier side and the inverter side can be used to eliminate faults outside the DC line area .

3) In the case of lightning strikes on the DC transmission line, the voltage mutations of the fault poles of the faulty lightning strike and the disturbing lightning strike both exceed 2. In the case of disturbing lightning strikes, the ratio of the sudden change in voltage between the two poles is greater than 3.5. Therefore, it is possible to use the sudden change in voltage at the two poles to eliminate disturbing lightning strikes. At the same time, when the grounding fault on the AC side or the DC commutation failure caused by the fault on the AC side occurs outside the DC line, the ratio of the voltage mutation is 1, so the ratio of the voltage mutation at the two poles can be used to eliminate the AC fault and the commutation failure.

b. Fault determination considering the electromagnetic coupling relationship between double-circuit DC transmission lines:

1) When a fault occurs on one of the DC transmission lines, the voltage change of the fault pole is the largest, which can be used to determine the fault pole. Since the voltage mutation ratio of the faulty pole and other three-circuit lines is greater than 2, and when the AC side is faulty, due to the symmetrical arrangement of the equipment on the DC system transmission line, the voltage mutation ratio is 1, so the voltage mutation ratio can be used Ratio to exclude AC side faults, commutation failures.

2) The polarity of the modulus maximum value of the current after wavelet transformation is not affected by the transition resistance, and the polarity of the modulus maximum value of the current wavelet transformation on the rectifier side and the inverter side can be used to eliminate faults outside the DC line area .

3) In the case of a faulty lightning strike, the maximum value of the wavelet transform modulus of the voltage of the fault pole is positive; when a disturbing lightning strike occurs, the maximum value of the wavelet transform modulus of the voltage of the disturbance pole is negative, so the voltage can be used Wavelet transform modulus maxima to eliminate lightning interference.

According to the above fault determination method considering the electromagnetic coupling relationship between the pole lines, the influence of the electromagnetic coupling between the extremes on the entire DC transmission system is effectively considered, and the fault can be effectively distinguished and determined.

In the step 2 protection start, the protection calculates the voltage mutation by collecting the voltage change signal at the protection installation place of the DC transmission line. If it exceeds the start threshold, the protection logic is started and enters the next link. The other main criteria for protection are:

In the formula, i represents the positive and negative poles of the DC transmission line, i=1, 2; k _R and k _I are the starting thresholds of the protection criteria of the line rectification side and inverter side, respectively. Using the ratio of the amplitude of the voltage change measured on the two-pole line can identify the fault pole and eliminate the AC side fault, commutation failure and lightning interference; use the polarity of the modulus maximum value of the wavelet multi-scale analysis of the current mutation Whether it is the opposite, the faults inside and outside the DC line protection zone can be distinguished; the polarity of the modulus maximum value of the wavelet multi-scale analysis of the voltage mutation can be used to exclude lightning strike interference. According to this, the protection criterion of DC transmission line can be constituted:

In the formula, i, j represent the positive and negative poles of the double-circuit direct current transmission line, i=1,2,3,4; j=1,2,3,4; j≠i; M represents wavelet transformation processing on the signal; R and I represent the _{rectification side} and the _inverter side respectively; _{k R1} is the setting value of the ratio of the voltage mutation of the two poles on the rectification side of the line; ; sign(MΔi _Ri ), sign(MΔi _Ii ) represent MΔi _Ri , the polarity of MΔi _Ii respectively;

sign(MΔu _Ri ) indicates the polarity of the wavelet transform modulus maximum value of Δu _Ri ; Δu _Ri and Δu _Rj respectively indicate the line voltage variation of pole i and pole j on the rectification side; Δi _Ri and Δi _Ii indicate the rectification side and inverter Variation of line current on side i pole.

In the pole selection logic in step 3, after the protection logic is started, the protection starts to calculate the ratio of the sudden change of the voltage of the two poles. If the ratio exceeds k _R1 , it means that the fault is in the local pole. For double-circuit lines, go to step 4 to eliminate interference; for single-circuit lines, continue to carry out protection logic. If the ratio of the sudden change in the voltage of the two poles exceeds k _R2 , that is, lightning strike interference occurs on the DC line, and the protection resets. However, if the ratio of the sudden change in voltage between the two poles does not exceed k _R2 , it means that there is a fault on the line, and enter step 5 to determine the boundary.

In step 4 interference elimination, the protection performs wavelet transformation on Δu _Ri to obtain the modulus maximum value of the wavelet transformation at the fifth scale. If it is negative, it means that it is lightning interference, and the protection resets, but if it is positive, it means that it is not lightning Interference, enter the boundary judgment.

In step 5 boundary judgment, the protection reads the current signals of the rectifier side and the inverter side, and performs wavelet transformation on the current signals, and judges whether to start the line protection according to the polarity of the modulus maxima of the wavelet transformation on both sides. If the polarities of the wavelet transform modulus maxima of the current on both sides are opposite, the line protection will be activated, otherwise the protection will reset.

The above detailed description is a specific description of the feasible embodiment of the present invention. This embodiment is not used to limit the patent scope of the present invention. Any equivalent implementation or change that does not deviate from the present invention should be included in the patent scope of this case. middle.

Claims (2)

1. the protection of direct current supply line configuration setting method considering electromagnetic coupled relation, it is characterised in that Comprise the steps:

Step one: line fault analysis judges, determines HVDC transmission line type, straight-flow system knows The fault that this circuit is not corresponding；

Step 2: relay protective scheme starts, becomes by gathering the voltage of DC power transmission line existing protection installation place Change amount signal, calculates voltage jump amount, if exceeding enabling gate threshold value, then starting protection logic enters next step Suddenly；

Its criterion is:

$\left\{\begin{array}{c}\left|\mathrm{\Δ}{u}_{Ri}\right|>k_R\\ \left|{\mathrm{\Δu}}_{Ii}\right|>k_I\end{array}\right.$

In formula, i represents the positive and negative polarities of DC power transmission line, i=1 (+), 2 (-)；R and I represents rectification side respectively And inverter side；k_RAnd k_IIt is respectively line commutation side and the enabling gate threshold value of inverter side Protection criteria；

Its protection of direct current supply line constituted judge formula as

$\left\{\begin{array}{c}\left|\mathrm{\Δ}{u}_{Ri}\right|/\left|\mathrm{\Δ}{u}_{Rj}\right|>k_{R1}\\ q=sign\left({\mathrm{M\Δu}}_{Ri}\right)=-1\\ p=sign\left(M\mathrm{\Δ}{i}_{Ri}\right)\×sign\left(M\mathrm{\Δ}{i}_{Ii}\right)=-1\end{array}\right.,$

In formula, i, j represent the positive and negative polarities of double back DC power transmission line, i=1,2,3,4；J=1,2,3,4；j≠i；M Represent and signal is carried out Wavelet transformation process；R and I represents rectification side and inverter side respectively；k_R1Whole for circuit Stream the two poles of the earth, side voltage jump amount ratio setting valve；MΔi_Ri, M Δ i_IiRepresent Δ i respectively_Ri, Δ i_IiSmall echo become Die change maximum；sign(MΔi_Ri), sign (M Δ i_Ii) represent M Δ i respectively_Ri, M Δ i_IiPolarity； sign(MΔu_Ri) represent Δ u_RiThe polarity of wavelet modulus maxima；Δu_RiWith Δ u_RjRepresent rectification side respectively I pole and j polar curve road voltage variety；Δi_RiWith Δ i_IiRepresent that rectification side and inverter side i pole line current become respectively Change amount；

Step 3: select pole logic, after relay protective scheme starts, protection starts to calculate the two poles of the earth voltage jump amount Ratio, if ratio is more than k_R1, then explanation fault extremely this pole, for double-circuit line, enter step 4 interference Get rid of；Single back line is then proceeded to relay protective scheme, if the two poles of the earth voltage jump amount ratio is more than k_R2, There occurs thunderbolt interference on this explanation DC line, protect involution；If but the two poles of the earth voltage jump amount ratio is not More than k_R2, then break down on explanation circuit, enter step 5 and carry out edge determination；Described k_R2For single time Route protection logic is for distinguishing thunderbolt interference and the two poles of the earth voltage jump amount ratio setting valve of lightning fault；

Step 4: ELIMINATION OF ITS INTERFERENCE, protects right+u_RiCarry out wavelet transformation, obtain the wavelet transformation under the 5th yardstick Modulus maximum, if it is negative, explanation is thunder and lightning interference, protects involution, but if just, then illustrates not It is thunder and lightning interference, enters edge determination；

Step 5: edge determination, protection is read rectification side and inverter side current signal, and is entered current signal Row wavelet transformation, and judge whether to start route protection according to the polarity of the modulus maximum of both sides wavelet transformation； If the wavelet modulus maxima opposite polarity of both sides electric current, start route protection, otherwise protect involution.

2. the protection of direct current supply line configuration side of adjusting considering electromagnetic coupled relation as claimed in claim 1 Method, it is characterised in that: it is by adopting with inverter side current signal that rectification side is read in the protection described in step 5 The current change quantity signal gained of collection protection installation place.