CN100424953C - A method for reclosing a power transmission line - Google Patents

Abstract

A reclosing method for transmission lines, for the relay protection of double-circuit lines paralleled on the same pole: each circuit of double-circuit lines paralleled on the same pole shall be individually protected, and the main protection of double-circuit lines paralleled on the same pole shall be phase-separated For current differential protection or longitudinal protection with phase-splitting commands, for various forms of single-circuit line faults and cross-line faults in the area, the fault phase should be selected to jump to realize adaptive reclosing: when the transmission line fails An adaptive recloser applied to high-voltage and ultra-high-voltage transmission lines. On the basis of accurately selecting and tripping the fault phase, the line protection performs phase sequence reclosure in combination with the criterion of no serious permanent fault; Open phase; after the failure of the parallel double circuit line on the same pole, at least two phases with different names in the double circuit line are allowed to overlap. On the basis of the impact, the chance of system coincidence and the probability of successful coincidence are maximized.

Description

A method for reclosing a power transmission line

technical field

The invention relates to a reclosing method of a power transmission line, in particular to a relay protection method for double-circuit lines paralleled on the same pole and a novel reclosing protection method.

Background technique

With the development of the electricity market and the construction of the power grid, the ability of the line to transmit electricity is required to be fully utilized; compared with two single-circuit lines, the double-circuit line paralleled on the same pole has lower project cost, smaller outlet corridor width, shorter construction period, and obvious economic benefits. Therefore, in the case of high land acquisition costs and tight exit corridors, double-circuit lines on the same pole are often used.

Overseas ultra-high voltage transmission lines have successful operation experience in this respect. For example, in the power grids of Japan and European countries, most of the high-voltage and ultra-high voltage lines use double-circuit (or even multiple-circuit) lines on the same pole. The economic benefits are very obvious. In my country, with the construction of the Three Gorges supporting transmission and transformation project and the development of the national ultra-high voltage inter-regional interconnection grid, the transmission corridor is becoming increasingly tense, and the number of 500KV parallel double-circuit lines on the same pole will continue to increase, which will definitely highlight its potential. Huge technical and economic benefits, at the same time, also bring some special technical problems to the grid operation.

From the point of view of the relay protection profession, compared with ordinary single-circuit lines, the main feature of the faults of double-circuit lines paralleled on the same pole is that there are cross-line faults. There are 11 kinds of simple faults of single circuit lines, while there are as many as 120 types of faults of double circuit lines paralleled on the same pole. Among the 120 types of double-circuit faults paralleled on the same pole, 63 are ground faults, 57 are non-ground faults; 22 are single-circuit faults, and 98 are cross-line faults. my country's original statistical data show that there are very few cross-line faults, accounting for only 2% to 3% of the total faults of double-circuit lines paralleled on the same pole. The statistics abroad are much larger. According to the statistics of the Tokyo Electric Power Company in Japan, during the 27 years from 1973 to 1999, the 500KV voltage level parallel double-circuit lines on the same pole occurred 25 times, accounting for 8.9% of all faults during the statistical period. %; and also in Japan, according to Chubu Electric Power Company's statistics on 275KV and above power grids in the past five years, the ratio of cross-line faults to all faults is as high as 20%. With the increase of parallel transmission lines on the same pole in our country, the probability of cross-line failure will definitely increase. During the fault period, how to maintain the electrical connection of the system to the greatest extent, reduce the possibility of losing double-circuit lines at the same time, and maintain the stable operation of the power grid is the starting point of our work and the key to the problem. Therefore, research on the special technical issues of relay protection and reclosing of double-circuit lines paralleled on the same pole and determine the technical requirements for relay protection and reclosing of double-circuit lines paralleled on the same pole have both important theoretical value and The urgent needs of production.

Special requirements for relay protection of double-circuit transmission lines paralleled on the same pole

1. Phase selection problem

The phase selection method that only reflects the electrical quantity on one side of the line cannot distinguish the single-circuit fault, cross-line fault and external fault of the double-circuit line at the end of the double-circuit line on the same pole. At present, the current sudden change phase selection principle popular in China has lost the ability of correct phase selection on the double-circuit line paralleled on the same pole, and is not suitable for the double-circuit line paralleled on the same pole. Impedance and other phase selection methods, although most of them can correctly select the phase, but when a double-circuit line on the same pole and a double-circuit line with a different name phase cross-line fault occurs near the two terminals of the line, the phase selection element far away from the fault side will be misjudged as a phase-to-phase fault , so that the double circuit is misjudged as a multi-phase fault, causing all the double circuit to trip, which seriously threatens the safe and stable operation of the system.

2. Zero-sequence mutual inductance problem

The zero-sequence mutual inductance coefficient of double-circuit lines paralleled on the same pole is relatively large, so that the residual voltage of the busbar is not only determined by the current of the main line when the ground fault occurs, but also affected by the zero-sequence current of the adjacent line, which affects the action range of the grounding distance protection on both sides; At the same time, when the faulty line is close to the fault point and the switch trips first, due to the influence of zero-sequence mutual inductance, the zero-sequence current protection range of the adjacent line of the faulty line will also change, which may cause protection malfunction or refusal to operate.

3. Reclosing problem

Even if the existing reclosing device can correctly select the phase, it cannot maintain the electrical connection of the system to the maximum extent when the three-phase cross-line fault occurs, thus affecting the stable operation of the system. For example: A phase ground fault of L1 line, BC phase fault of L2 line, single-phase reclosing of L1 line, three-phase jump of L2 line without reclosing, the connection between the two stations is reduced from 6 lines to 2 lines during reclosing; When the phase-to-ground fault of the AB phase of the L1 line and the BC phase fault of the L2 line occur, the three-phase trips of L1 and L2 do not overlap. Great impact on system stability.

In addition, modern large generators do not allow immediate automatic reclosing in the event of a multi-phase fault to prevent damage to the generator in the event of a permanent fault. When a two-phase, two-conductor permanent fault occurs on a parallel double-circuit line on the same pole, it is a single-phase fault for each circuit, but the generator has already experienced the impact of a multi-phase fault, so two circuits Measures should be taken for the line reclosing to prevent the generator from being impacted by multi-phase faults.

Research status at home and abroad

The problem of protection of double-circuit lines paralleled on the same pole was put forward relatively early. For a long time, domestic and foreign relay protection experts have conducted certain theoretical research on related topics and achieved some phased results. Most of the 500KV lines in Japan are double-circuit lines paralleled on the same pole, and they have rich experience in operation. With the increase of parallel double-circuit lines on the same pole and the gradual emphasis on related issues, some domestic network provincial bureaus and scientific research institutions are also conducting research, and have obtained some practical experience in operation and theoretical research results.

(1) Realization scheme of relay protection for double-circuit lines paralleled on the same pole

At present, there are mainly the following protection schemes at home and abroad:

1. Rely on the continuous action to realize the correct phase selection for cross-line faults. Under multi-phase fault, wait for the circuit breaker on the opposite side to trip, and achieve the purpose of correct phase selection and tripping on this side. High-frequency protection action, when the phase selection element is judged to be a multi-phase fault, it may be a double-circuit line on the same pole and a double-circuit line crossing the line with a different phase fault. This delay should be greater than the correct phase selection and tripping time of the other circuit protection on the opposite side (near the fault point). Only in this way can the problem of misselection of phases due to cross-line failure of parallel double-circuit lines on the same pole be solved. This scheme has the following disadvantages:

a. If the protection or circuit breaker on the primary line refuses to operate, the remote fault end of the line will be considered as a multi-phase fault, and the three-phase trip of the line will be tripped after a certain delay. The other circuit also accidentally tripped three phases due to the protection of the adjacent line near the fault end or the refusal of the circuit breaker to move, thus causing a power outage for all double circuit lines.

b. When a multi-phase fault occurs on this line, the protection on both sides will trip with a delay, which is not good for system stability.

c. If a phase-crossing fault with different names occurs on double-circuit lines paralleled on the same pole, the protection on the side far from the fault point will trip with a delay. It is detrimental to the stable operation of the system.

2. High-frequency distance protection for split-phase signal transmission

In the event of cross-line faults of different names in double-circuit lines paralleled on the same pole, the impedance phase selection element near the fault point can always select the correct phase. The high-frequency distance protection of phase-separated signal transmission is adopted, and the protection on both sides of the line exchanges the phase selection results after a fault, and then the faulty phase is correctly selected to realize a fast and correct phase selection tripping function. The protection does not need to set the waiting time for multi-phase faults, and can quickly remove the switches on both sides of the multi-phase faults, which plays a key role in improving the safety and stability of the power system. However, this solution has higher requirements on channels, and multiple channels must be used to realize the transmission of phase-separated and phase-selected signals. The multi-channel FSK multi-command signal system can meet the requirements, but when there is a short circuit of the line processing phase or a three-phase short circuit at the line exit, the high frequency protection will refuse to operate or delay action. At present, multiplexed carrier channels are used the most in China, fiber channels are gradually increasing, and microwave channels are rarely used. The United States and Japan mainly use optical fiber and digital microwave channels. The main protection of this type and its channel number requirements are shown in Table 1 below:

Table 1

model Manufacturing plant Number of channels LFP-902C Nari Company Duplex three-channel or four-channel RCS-902C Nari Company Duplex three-channel or four-channel REL531 ABB Duplex three-channel or four-channel ALPS GE Duplex two-channel or four-channel

However, this scheme cuts off one more phase when the three-phase three-conductor cross-line fault occurs at the end of the line, and cuts off two circuit lines when the three-phase four-conductor cross-line fault occurs at the end and two healthy phases belong to two circuit lines, which is not conducive to the stable operation of the system. .

3. Split-phase current differential protection

The principle of split-phase current differential protection is simple and reliable. It has a natural phase selection ability for conventional faults and cross-line faults. It can correctly and quickly phase-select and trip for double-circuit line cross-line faults with different names on the same pole. The main protection of Japan's EHV lines is all phase-separated current differential protection. But it has high requirements on the channel, requiring six independent signal channels, and the investment cost of the channel is high. At the same time, the protection has high requirements on channel bit error rate and transmission delay. In China, dedicated optical fiber channels are mainly used, and OPGW is being used more; in the United States and Japan, the 64kbit/s multiplex communication link (PCM) method is the main method.

(2) Reclosing mode

The reclosing function compatible with the relay protection of parallel double-circuit lines on the same pole is also necessary for the safe and stable operation of the power grid. Some manufacturers have carried out further research and application on the basis of conventional single-phase/three-phase/comprehensive reclosers. For example: the 2.0 version of REL500 series produced by ABB company, its reclosing mode is single-phase/two-phase/three-phase reclosing. That is, when single-phase fault occurs, single-phase reclosing is performed; when two-phase grounding or two-phase fault occurs, two faulty phases are tripped, and then two-phase reclosing is performed. When the three-phase fault occurs, the three-phase or non-reclosing can be performed according to the conditions. In addition, multiple reclosing can be realized. As mentioned above, when a phase A fault occurs on the L1 line and a phase B and C phase fault occurs on the L2 line, after the REL500 series recloser is used, the L1 line jumps off the A phase, and the L2 line jumps off the B and C phases. At this time, the two stations The connection between the three conductors with ABC complete three-phase is maintained, which improves the stability of the power system, but may cause the system to be impacted again by phase-to-phase faults during reclosing.

In foreign countries, the tripping and closing methods of the relay protection devices for double-circuit lines on the same pole are also different.

1. In the French Electricity Company (EDF), the relay protection of the double-circuit line on the same pole is generally configured with two sets of split-phase longitudinal differential protection with the same principle. When a single-phase fault occurs, the single-phase trips, and then the single-phase overlaps. If it is unsuccessful, it will jump three phases; if there is a phase-to-phase fault, it will jump three phases directly without coincidence. There is no exchange of protection information between the two loops on the same pole. This side also does not collect switch position information on the opposite side of this line and adjacent lines. It is basically the same as the tripping and closing method adopted in our country at present.

2. In Japan, the country that uses the most double-circuit lines on the same pole, the relay protection of the double-circuit lines on the same pole is generally configured with two sets of phase-separated longitudinal differential protection with the same principle, and the protection information and switch positions on both sides are transmitted by optical fiber or microwave information. Protection information should be exchanged between double-circuit lines adjacent to the same pole. After the double circuit line on the same pole fails, only the faulty phase will be jumped. For the multi-phase reclosing mode, each power company has different considerations. Such as Tokyo Electric Power Company, the use of reclosers is closely related to the voltage level and the structure of the transmission line. For 275kV and 500kV backbone networks, since the transmission lines are double-circuit lines paralleled on the same pole, multi-phase reclosing is generally used in order to avoid serious accidents of losing two lines at the same time; for 154kV lines, double-circuit lines paralleled on the same pole Multi-phase reclosing is used on the line, single-phase reclosing is used on single-circuit lines, and three-phase reclosing is used directly in some places; for 66kV, 22kV, and 6.6kV, three-phase reclosing is uniformly used. The specific method and reclosing time are shown in Table 2.

Table 2. Comparison table of reclosing mode and circuit breaker action time of lines of various voltage levels in Tokyo Electric Power Company

Central Japan Electric Power Company: For various types of faults, only phase-separated tripping is performed for the faulty phase. When judging tripping and reclosing, the following considerations are taken into account:

A. For 275KV and above double-circuit lines on the same pole, no matter what type of fault occurs, only the faulty phase will be tripped after the protection action. At this time, if a three-phase fault occurs in one circuit and the other circuit is intact, after confirming the information of the opposite side and the adjacent line through PCM communication, the medium-speed reclosing method (about 10 seconds) is used for reclosing. First, the system side overlaps. When the system side overlaps successfully, the power supply side collects information on the opposite side of the own line, adjacent lines, and the opposite side through PCM communication, and performs overlap after about 3 seconds.

B. For a fault like IBIIC that occurs on the double circuit line on the same pole, after the protection action, only the IBIIC of the faulty phase is jumped, and then high-speed single-phase reclosing is performed on the II line (the reclosing time is 0.35-0.835 seconds), and on the I line Use medium speed reclosing (reclosing time is about 10 seconds). In order to avoid the impact on the generator caused by the coincidence of the two circuit lines at the same time and the permanent fault. Since only one circuit adopts high-speed overlap at this time, both sides of the line overlap at the same time.

C. For the IBCIIC fault that occurs on the double circuit line on the same pole, after the protection action, only the IBCIIC of the faulty phase will be tripped. After the trip, the IAIIAB will still run. Because there are two phases of A and B on the II line at this time, firstly carry out high-speed single-phase reclosing on the II line. The overlap time is 0.35-0.835 seconds. If the IIC recloses successfully, after the I line detects that the II line has fully recovered, it jumps off the sound phase A of the I line, and then recloses the I line at a medium speed (the time is about 10 seconds).

The reclosing mode and reclosing time allowed by the Central Japan Electric Power Company for 500KV and 275KV power grids when various faults occur are shown in Table 3

Table 3 Reclosing schedule for each voltage level

Note: H-REC(S) means high-speed split-phase reclosing; H-REC means high-speed three-phase reclosing;

M-REC means medium-speed three-phase reclosing; L-REC means low-speed three-phase reclosing.

At present, the relay protection technology has made considerable progress, and the microcomputer line protection with superior performance has also been widely used. When cross-line faults occur on double-circuit lines paralleled on the same pole, if only the fault line can be cut off to realize multi-phase reclosing, it will undoubtedly be beneficial to maintain system stability. In other words, while maintaining the same system stability level, the transmission power of the transmission line can be increased to bring economic benefits. Although the probability of cross-line failure is small, its possibility cannot be ruled out. Just as there is a three-phase fault on a single circuit line and the possibility of three-phase short circuit at the same time is extremely small, but it still happens, so in this case, the protection should also act quickly and selectively. Therefore, it is of universal importance to develop a computer-based line protection and reclosing device with phase selection capability suitable for parallel double-circuit lines on the same pole, and it is also completely achievable.

Contents of the invention

The purpose of the present invention is to provide a new type of protection method for power transmission circuits, especially the relay protection method for double-circuit lines paralleled on the same pole, to improve the coincidence rate of double-circuit lines paralleled on the same pole, and to reduce the simultaneous cutting of two Possibility of return lines; reduce the impact of reclosing and permanent faults on the system; provide technical basis for the development and application of relay protection and reclosing devices suitable for parallel double circuit lines on the same pole. And the relay protection of double circuit lines on the same pole shall meet the following requirements:

a) When a cross-line fault occurs, the protection should only jump off the fault phase of the line, that is, strict requirements for the correct selection of the fault phase and fault line are put forward for the relay protection.

b) In the mode where only one circuit runs on the double circuit line on the same pole, the relay protection of the double circuit line on the same pole should work correctly.

c) After the double-circuit line on the same pole has a fault protection trip, the relay protection should work correctly in the non-full-phase operation mode.

The purpose of the present invention is achieved in this way: a reclosing method for power transmission lines, relay protection for double-circuit lines paralleled on the same pole: each circuit of double-circuit lines paralleled on the same pole should be separately configured for protection, and double-circuit lines paralleled on the same pole The main protection of the circuit adopts phase-separated current differential protection or longitudinal protection with phase-separated commands. For various forms of single-circuit faults and cross-line faults in the area, the fault phase should be selected to realize self-adaptive coincidence Gate: An adaptive recloser applied to high-voltage and ultra-high-voltage transmission lines when a fault occurs in the transmission line. The line protection is based on the accurate selection of the fault phase and combined with the criterion of no serious permanent fault to perform phase sequence reclosure; that is In order, the phases are separated and reconnected successively to jump open phases; after the double-circuit line on the same pole is faulty, the overlap is allowed only when at least two phases with different names in the double-circuit line are healthy, otherwise, the two circuit lines must all be jumped; to protect Accurate selection of the fault phase is the basis; when the transmission line is single-phase fault, two-phase fault and three-phase fault, only the fault phase is selected, instead of two-phase fault three trips; the protection device integrates the operation information of the two-circuit line according to The following rules coincide in order: the coincidence sequence is coincident according to the phase separation order, and the phases with the same name are preferentially coincident and coincident at the same time; the leading phase of the two-phase fault line is preferentially coincident; Permanent ground fault: U _φ > Uzd U _φ is the tripping phase voltage, Uzd is the setting value, meeting this voltage criterion means that no nearby permanent ground fault occurs. On the basis of minimizing the impact of coincidence and permanent faults on the system, the chance of system coincidence and the probability of successful coincidence are maximized, and the ability of transmission lines to restore power supply after a fault is improved. The method of phase-separate sequence coincidence solves the problem of possible coincidence with multi-phase permanent faults, and at the same time solves the problem that the terminal voltage criterion cannot distinguish between phase-to-phase permanent faults and three-phase symmetrical permanent faults.

For phase-to-phase ungrounded permanent faults, based on phase-separation sequence coincidence, the following voltage criterion is used to determine whether a permanent ungrounded fault has occurred:

$<span\; class="notranslate">\; |</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; ></span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="k"\; filenames="C20041006496000222.png,C20041006496000232.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; |</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; -</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; |</span>$

k ₁ can be 4-6;

When any phase is closed, if the system meets the above conditions, it will be judged as a permanent ungrounded fault between phases, and no phase-splitting reclosing orders will be issued.

If the line is completely transposed, the capacitive coupling voltage and mutual inductance voltage of the healthy symmetrical three-phase tripping phase will be very small, which cannot meet the voltage criterion, and both sides are considered to have serious permanent faults and do not overlap. Insufficient voltage criterion, using lines to protect internal information. If any of the following conditions is met, it is considered that there is no nearby serious fault, and the coincidence can be given:

a) The phase voltage and the phase-to-phase voltage are relatively large at the time of failure;

b) Fast protections such as channel-independent impedance section I and power frequency variable impedance do not operate;

c) The ranging result is larger.

When the fault point has not yet extinguished the arc in the case of a transient fault, the reclosing time is automatically extended until the fault point is extinguished, so as to increase the probability of successful reclosing. For lines without shunt reactors, arc extinguishing criteria at fault points based on voltage amplitude combined with voltage high-order harmonic content are introduced during adaptive reclosing. The arc extinction criterion is:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="k"\; filenames="C20041006496000221.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="u\; fd"\; filenames="C20041006496000222.png,C20041006496000232.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; id="1"\; label="u\; fd"\; filenames="C20041006496000222.png,C20041006496000232.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}\end{array}\right.$

k ₂ can be 0.1-0.2, such as 0.1; k ₃ can be 0.2-0.4, such as 0.2;

U _fd1 , U _fd3 , and U _fd5 are the amplitudes of the fundamental, third and fifth harmonics of the jump-off phase voltage, respectively.

For lines with shunt reactors, _the free oscillation _voltage appears after the fault point is extinguished, so the amplitude of the _disconnected phase voltage will fluctuate _greatly . -0.4, such as 0.2; U _{fd1_ave} is the average value of the fundamental voltage; U _P and U _Y are three-phase voltage vectors, and U _N is the neutral point voltage.

The reclosing gate of the present invention should be configured according to the line to maintain the relative independence and integrity of the double circuit protection and the reclosing gate. When the adaptive reclosing operation condition is not satisfied, it will automatically switch to the conventional reclosing gate. At this time, the tripping mode of the protection should be automatically changed. It is a conventional method, that is, two-phase fault and three jumps.

The invention needs to synthesize the operation information of the two circuit lines according to the phase order reclosing, so as to judge whether the condition of two phases with different names is satisfied; the line protection contains the operation status of the line. The information exchange is carried out through the optical fiber connection between the circuit protection. The protection channel uses optical fiber, microwave and other digital channels to transmit protection information.

The arc extinguishing criterion and the non-severe permanent fault criterion of the present invention are also applicable to single-circuit lines.

In the present invention, each circuit of the double-circuit line paralleled on the same pole should be independently configured for protection, allowing the exchange of information between the two circuits. The main protection of pole-parallel double-circuit lines adopts phase-separated current protection or longitudinal protection with phase-separated commands, and the protection channel adopts optical fiber or microwave channel, or multiple fast-command carrier channels to transmit protection information;

When the setting value is set, for the over-range distance element of the double-circuit line on the same pole, the short-circuit at the end of the double-circuit line has sufficient sensitivity when the double-circuit line runs at the same time; for the under-range distance element, ensure that the end Short circuit is not exceeded.

The reclosing switch should be able to adapt to a variety of different reclosing methods according to the requirements of the primary system, namely single-phase reclosing, three-phase reclosing, comprehensive reclosing, and phase sequence reclosing;

Features of double circuit line protection on the same pole

The main feature of double-circuit line faults on the same pole is that there are cross-line faults. There are 11 types of simple faults on single-circuit lines, and as many as 120 types of faults on double-circuit lines on the same pole. Among the 120 types of double-circuit faults on the same pole, 63 are ground faults, 57 are non-ground faults; 22 are single-circuit faults, and 98 are cross-line faults. Usually, cross-line faults are divided into phase-crossing faults with non-identical names and phase-crossing faults with the same name.

Although cross-line faults occupy an overwhelming advantage in fault classification, the proportion of single-circuit line faults is still over 80%. Statistics in my country show that cross-line faults are rare, accounting for only 2% to 3% of the total faults of double-circuit lines on the same pole , which is far less than the data of foreign statistics, which requires us to fully consider the protection problem when the fault occurs, that is, not only the protection problem when the cross-line fault occurs, but also the protection problem when the single-circuit fault occurs.

Another feature of double circuit lines on the same pole is the need to consider the mutual inductance between the double circuit lines. The most influential is the grounding protection of the double circuit lines, that is, zero-sequence current protection and grounding distance protection.

Basic principles of protection configuration for double circuit lines on the same pole

At present, the single-command longitudinal direction and longitudinal distance protection can correctly select phases for single-circuit faults, and single-phase faults can be single-hoped and reclosed. Three jumps for multi-phase faults are not serious. When a cross-line fault occurs on the same pole, generally speaking, there is always one side of the protection that thinks it is a multi-phase fault and trips three times, resulting in three jumps on both double-circuit lines. As we all know, most of the actual faults are transient faults.

Therefore, in order to improve the reliability of power transmission, it is required that the relay protection can select the phase to trip when the cross-line fault occurs. If an IAIIBG fault occurs, the phase A will be jumped on both sides of the I circuit, and the B phase will be jumped on both sides of the II circuit. After the trip, there will be The four phases can still transmit relatively large power during operation, and then the reclosing action is generally successful for instantaneous fault reclosing, returning to normal double-circuit operation. Even if only one loop is successfully overlapped, one loop can be kept running.

Split-phase current differential protection should be used as the first choice for double-circuit lines on the same pole. Split-phase current differential protection has a series of advantages, such as absolute selectivity to external faults, no response to load, not affected by system oscillation, natural phase selection ability, and good performance in non-full-phase operation. It is suitable for both long and short lines, and is not affected by series compensation capacitors. Even on single-circuit lines, it is a good protection worth adopting. It is more common in Japan for split-phase current differential applications. It is naturally applied on the parallel double-circuit line on the same pole, and there is no special need for modification. The split-phase current differential protection is configured according to the line. A set of protection is set for each line on the double-circuit line on the same pole, independent of each other. Each protection only collects the three-phase current of the line and sends a trip command to the circuit breaker of the line. Even if there is a misoperation, it will not accidentally cut the two loops at the same time. This fully complies with the requirements of the 1991 Wuxi Conference. The use of split-phase current differential protection can satisfactorily solve the problem of protection of double-circuit lines paralleled on the same pole.

Therefore, it is advisable to configure two sets of phase-separated current differential protection for each line of double-circuit lines paralleled on the same pole. Protection constitutes a dual primary protection is an option. The main problem of the longitudinal distance protection is to correctly select the fault phase of the line when the fault occurs across the line. The phase selection method that only reflects the electrical quantity on one side of the line cannot distinguish the single-circuit fault, the cross-line fault and the double-circuit fault at the end of the line. Return line external fault. Because it must be seen from the beginning of the line that the same type of fault has occurred on the two circuit lines. For example, when a cross-line fault close to the side of the line occurs, such as a cross-line grounding fault (denoted as IAIIBG) in which phase A of the I loop line and phase B of the II loop line occur, only the protection near the fault side can select the fault phase of the line , and the protection of each return line on the other side of the line will see a two-phase fault (like a four-phase fault). The correct phase selection of the far-fault side cannot rely on the phase-by-phase blocking or permitting signals sent from the near-fault side, which means that each return line should occupy 3 command channels in order to send out blocking or permitting signals according to the phase. The solution of simulating 3 blocking or enabling command signals with 1 or 2 command channels should not be adopted, as it has been proven that speed and safety are reduced.

In short, the protection of each circuit should be independently configured to prevent the double circuit from being cut off due to the malfunction of a set of devices. In addition, the operation and maintenance of a single circuit will not affect the normal operation of the other circuit. For the longitudinal distance protection, there should be 3 independent channels to transmit phase splitting commands. In addition to the main protection, each set of protection should be equipped with quick-break protection that does not depend on the channel to quickly remove serious faults nearby (such as power frequency variable impedance relay, impedance I section), distance protection with time limit and zero-sequence current protection.

The zero-sequence mutual inductance of double-circuit lines paralleled on the same pole has a great influence on the protection range of the grounding distance, which should be considered in setting. The setting of the longitudinal distance and the impedance section II should ensure that the terminal fault is sensitive when the double-circuit line is in operation, and the setting value of the impedance section I should ensure that the terminal fault does not exceed when the ground wire is hung on both sides of the adjacent line for inspection and maintenance. It is inappropriate to use the zero-sequence current of the adjacent line to compensate the grounding distance of the main line. The main reasons are: a) the introduction of the electrical quantity of the adjacent line is not good for operation and maintenance; b) when the switch of the adjacent line on this side is turned on, the The zero-sequence current compensation of the line may cause protection overriding independent of the channel; c) When a single-phase ground fault near the adjacent line is introduced, the phase-to-ground distance relay with the same name on this line is prone to override and misoperation due to the introduction of zero-sequence current compensation on the adjacent line .

When a fault occurs during non-full-phase operation or when reclosing, it is often a permanent fault or other phase faults of this line occur near the original fault point. Impedance II section and zero-sequence current protection, these protections are not dependent on the channel and are sensitive to the whole line. Although it seems that there is a possibility of losing selectivity, it has been proved to be completely successful in practice. However, for the double-circuit line on the same pole, when cross-line faults are considered, it should be considered that when the main line is not in full phase, the adjacent line does not malfunction, or when the two circuit lines are not in full phase, one circuit coincides with the fault and the other circuit does not Malfunctioning measures. Reclosing can be used to accelerate only the tripping phase of this line, and non-full-phase operation can be used to accelerate the impedance II section with a short delay such as 120ms to ensure selectivity.

The present invention is characterized in that it solves the problem of correct phase selection and rapid tripping of any fault under any working condition of parallel double-circuit lines of 500kV and below. Moreover, the interface with existing protection and security control equipment, as well as the safety and convenience of construction are fully considered, so it has both the advancement of technology and the feasibility of practical application.

1. The proposed adaptive reclosing scheme fully absorbs the existing scientific research achievements and further innovates. There is a solid theoretical basis, and a large number of simulation calculations, dynamic model tests and RTDS digital real-time simulation verification have been carried out. Compared with other overlapping schemes at home and abroad, this scheme has the following characteristics:

1) The reclosing function is reasonably distributed between the line protection and the circuit breaker protection, and the information of the line protection is fully utilized to realize the non-serious fault judgment and phase-separation sequence reclosing strategy, which is realized by the circuit breaker protection according to its own state and the coordination relationship of adjacent switches coincident exit;

2) The method of jumping only the faulty phase is adopted, that is, when two phases of the line fail, only two phases are jumped instead of three, so that the connection between the two ends of the system can be kept to the greatest extent during the fault period, and there are the most opportunities to start reclosing and restore Possibility of normal operation of double circuit lines;

3) The reclosing of the two circuit lines is regarded as a whole, and the phase-separated sequential closing is adopted, and only one phase of the two circuits recloses at the same time, which avoids the impact on the system caused by reclosing and permanent multi-phase faults;

4) No serious permanent fault criterion is adopted for the first time in the reclosing scheme, which further reduces the impact of reclosing and permanent faults on the system, and the reclosing side will no longer reclose after the reclosing fault on the opposite side.

Therefore, this scheme maintains the connection between systems to the greatest extent during the failure period, and greatly increases the chance of coincidence and the probability of success of coincidence on the premise of avoiding serious impact on the system. It has advantages that other schemes at home and abroad cannot match. .

2. Based on the importance of the double circuit line, in order to ensure the safe operation of the system and reduce the operation risk, the existing protection device is retained, and it can still be completely and reliably put into operation at any time according to the need. The new protection fully considers the interface with the existing protection and avoids the impact on the existing protection devices.

3. When the new protection is put into operation, it is basically consistent with the original protection in terms of setting value and operation and use, making it easy for the dispatch management department and the operation and maintenance department to maintain and manage.

The CT secondary load measurement, operation box and circuit breaker control circuit transformation were completed on site, which created conditions for the new protection to be put into operation; the circuit breaker protection transformation made it suitable for parallel lines and Normal operation of conventional single-circuit lines.

Description of drawings

Figure 1 is the logic diagram of phase sequence reclosing protection

Figure 2 is the logic diagram of phase priority reclosing protection with the same name

Figure 3 is the logic diagram of leading phase priority reclosing protection

Figure 4 is the logic diagram of the leading phase priority reclosing protection of the two-phase fault line

Figure 5 is a comparison of phase voltage waveforms for single-phase grounding instantaneous and permanent faults

Fig. 6 is the instantaneous fault fault phase terminal voltage diagram of the present invention (without shunt reactor)

Fig. 7 is the instantaneous fault fault phase terminal voltage diagram of the present invention (with shunt reactor)

Fig. 8 is a fault phase voltage and current waveform diagram of the artificial single-phase grounding test of the present invention (with shunt reactor)

Detailed ways

Selection of Protection Tripping Modes for Double Circuit Lines on the Same Roof

The conventional tripping method is a single trip for single-phase faults and three trips for multi-phase faults. The disadvantage of this scheme is that it fails to maintain the connection between the two ends of the system to the greatest extent when three or more conductors fail. For example, when the IAIIBCG three-phase three-wire fault occurs, only the IBC two-phase is running during the reclosing period, and the IIA phase fails to participate in the quasi-three-phase operation. Another example is that when the IABIIBCG three-phase four-wire cross-line fault occurs, the double-circuit line is cut off, and the ICIIA two-phase operation cannot be retained and the switch is reclosed.

Therefore, when the systems on both sides mainly rely on double-circuit connections, the ideal tripping method is to only cut off the faulty phase when a fault occurs. The difference from the conventional one is that two-phase faults jump two phases instead of three phases, that is, keep the non-faulty phases and continue to run. , and reclose. As mentioned earlier, this type of tripping maximizes the connection between the two ends of the system during the reclosing cycle and has more chances of starting reclosing.

The conventional way to coincide with a fault is three jumps, regardless of whether it is coincident with a single-phase or multi-phase fault. The ideal way is to overlap the fault and still only jump the fault phase, and then check whether the remaining healthy phases of the two circuit lines can constitute quasi-three-phase operation. For example, if only the faulty phase is cut off when IAIIBCG occurs, the power can also be transmitted through healthy three-phase (IBCIIA). If it is a permanent fault, it will run like this (called "quasi-three-phase" operation). If it is a permanent IAIIBG fault, there are four IBCIIAC phases that are sound phases. In order to maintain the three-phase symmetry, one phase must be cut from the C phase of the two circuit lines to achieve quasi-three-phase operation. Obviously, this method can still keep a loop line (for the system at both ends) running for most of the permanent cross-line faults.

At present, the "quasi-three-phase" operation method has not been adopted at home and abroad, because quasi-three-phase operation will bring many problems: a) If there is a shunt reactor on the line, the small reactance at the neutral point will pass current for a long time; b) Dispatching How will the personnel recover from the quasi-three-phase operation mode to the normal operation mode; c) If the protection is configured separately for each circuit, the performance of the protection will be greatly deteriorated in the quasi-three-phase operation mode, such as zero-sequence backup protection is lost; d) the switch Long-term three-phase inconsistent operation, etc., unless the signals of the double-circuit line are introduced, that is, it is necessary to configure a set of protection for the two-circuit line as a whole.

In short, the tripping method can be single-phase fault single-jump multi-phase fault three-jump method, and for important double-circuit lines on the same pole, only the faulty phase should be used, that is, two-phase faults and two phases should be used to improve the reliability of power transmission as much as possible. sex. However, overlapping faults always result in three trips, and should not be integrated into "quasi-three-phase" operation.

Selection of reclosing mode for double circuit lines on the same pole

In my country, single-phase reclosing is often used on transmission lines with a voltage level above 220kv, that is, single-phase tripping allows reclosing and three-phase tripping does not allow reclosing. The main reason is that there are still two phases running after the single phase is tripped, and the systems on both sides are closely connected, so it is possible to unconditionally overlap without verifying the same period. In addition, coincidence and faults are only coincidence dry single-phase permanent faults, which avoids coincidence and multi-phase The serious impact of failure on the system. However, when the double-circuit line on the same pole is used, considering the situation of cross-line faults, even if the single-weight method is used, it is still unavoidable to avoid overlapping and two-phase permanent faults. If a permanent IAIIB fault occurs, the two circuit lines are single-hop and single-weight, and if they overlap at the same time, it is coincident with the AB two-phase fault for the system. Of course, this method avoids coincidence with three-phase faults.

On the double-circuit line of the same pole, if the two-circuit line is regarded as a single-circuit line to realize the single-weight mode, only two conductors with different names among the six conductors are required to be sound, and overlap is allowed. This reclosing method is the so-called multi-phase reclosing method, which is widely used in Japan. This method cooperates with the tripping method of only tripping the fault phase (jumping two phases for two-phase faults), and there are more chances of coincidence, but it may coincide with two-phase or even three-phase permanent faults.

On the basis of the multi-phase reclosing method, in order to avoid reclosing from multi-phase faults, a scheme of reclosing according to phase sequence is proposed. The basic idea is to regard the reclosing of the two circuit lines as a whole, and only one phase of the two circuit lines is reclosing at the same time, and the other phase is reclosed after the reclosing is successful. If the coincidence is not successful, then jump the line three times, and then check the other circuit if it meets the single condition, then continue to overlap, otherwise jump three times.

Both multi-phase reclosing and phase sequence reclosing are based on the protection of only tripping the faulty phase, so they can maintain the connection between the two ends of the system to the greatest extent during the fault period, have the most opportunities to start reclosing, and restore double-circuit lines Likelihood of normal operation, see Table 4 for comparison. The use of phase sequence reclosing completely avoids reclosing and multi-phase permanent faults, which is more advantageous. For the three-phase fault of a circuit line, it should not overlap again after three jumps. The main reason is that the probability of three-phase faults is very small and most of them are permanent faults caused by human beings.

Table 4 Comparison of reclosing opportunities between single-phase reclosing and multi-phase reclosing

Note: The shadow is the fault phase, "φ": reclose, "-": no reclose, "*" is the situation that can start reclose, which is increased compared with the conventional single weight. The multi-phase reclosing or reclosing according to the phase sequence in the table is to consider that there are two phases with different names in the two circuit lines, which are healthy and allow coincidence (quasi-single weight), but if the three phases in one circuit are all tripped, the line will not overlap.

Reclosing should be configured according to the line. For multi-phase reclosing and reclosing according to phase sequence, it is necessary to integrate the operation information of the two circuits to determine whether the conditions for the soundness of the two phases with different names are met. The line protection contains the running status of the line. In order to obtain the information of the other line, it can be realized by increasing the digital communication between the two line protections. Cross, easy to operate and maintain. When the information of the adjacent line cannot be obtained for some reason, it should be able to automatically switch to the conventional single-phase reclosing switch. At this time, the tripping mode of the protection should be automatically changed to the conventional mode, that is, three trips for two-phase faults. At the same time, it should be avoided to coincide with two-phase permanent faults at the same time.

Another advantage of configuring the recloser according to the line is that when the line TV is used, the information of the line protection can be fully utilized to achieve reclose without fault or reclose first on the side without serious fault, and avoid permanent fault of reclose on fault or reclose on exit.

The double circuit lines on the same pole overlap according to the order of combination without serious faults

1 Strategies for coincidence in phase order

In order to avoid coincidence and multi-phase permanent fault, it is required that only one phase of the two circuits coincides at the same time. Therefore, the protection device should integrate the operation information of the two circuits and overlap them in a certain order. The coincidence order is determined as follows:

1) Phases with the same name are preferentially overlapped and can be overlapped at the same time. The reasons are:

a) Even if it coincides with a permanent fault, it is a single-phase fault for the system;

b) Resume the operation of the missing phase as soon as possible;

c) The overall reclosing time can be reduced.

2) The leading phase of the two-phase fault line overlaps preferentially. The purpose is that one circuit line overlaps with the fault three times and the other circuit line still meets the single condition to continue to overlap. If the IABIIC is faulty, reclose IA first, even if it coincides with the faulty I circuit with three jumps, but the AB of the second circuit is still healthy, and you can reclose the IIC; and if you close the IIC first, if it coincides with the fault II circuit with three jumps, then two times There is only IC left in the line, and the I round can no longer overlap, and the chance of overlapping has been lost.

3) Priority reconnection of leading phases, the purpose is to make the probability of priority reconnection of each phase the same (assuming that the probability of failure of each phase is the same). Regardless of whether it is a circuit fault or a cross-line fault, it will overlap in the order of the leading phase priority.

For example: IABIIBC fault, phase B of the two circuit lines overlaps first, then IIC, and finally IA;

For IABIIC failure, first close the leading phase IA of the two-phase fault, then close IB, and finally close IIC;

IAIIC failure, first turn on IIC, then turn on IA;

If IAB fails, close IA first, then close IB.

Table 5 shows the reclosing sequence according to this strategy under various fault conditions

Table 5 Reclosing sequence of phase sequence reclosing

Note: The shadow is the faulty phase, "φ": coincidence, "-": no coincidence or no start of coincidence. The reclosing according to the phase sequence in the table is to consider that there are two phases with different names in the two circuit lines, which are healthy and allow coincidence (quasi-single weight), but if the three phases in one circuit line are all tripped, the line will not overlap.

It can be seen from the table that, compared with the multi-phase reclosing scheme, the reclosing scheme according to the phase sequence can avoid reclosing and multi-phase permanent faults in most cases by increasing the reclosing interval (about 200ms). In complex fault conditions, two reclosing intervals need to be added. The non-full-phase time will not increase too much, and the action time of the three-phase inconsistency of the circuit breaker should be much longer than this value.

Judgment of no serious failure

Reconnection in phase order avoids overlapping with multi-phase permanent faults. For large-scale power transmission through long-term power transmission, when overlapping with single-phase faults at large power outlets, it will also have a great impact on the system. When using line TV, use the jump-off phase. The voltage characteristics and the action information of the protection can determine whether a permanent fault near the exit has occurred. If it is possible, the remote fault side will be reclosed first, and the reclosed on the opposite side of the fault. After successful overlapping, the main side is overlapped immediately.

After the faulty phase is disconnected, there are capacitive coupling voltage and mutual inductance voltage between the relatively disconnected healthy phases. On the line with shunt reactor compensation, when the submerged arc is extinguished, the electromagnetic energy stored in each energy storage element decays in the way of free oscillation according to the natural frequency of the network (30-40Hz) (the decay time constant is about 1 second ). This free component is therefore still present in the voltage across the disconnected phase.

When a permanent ground fault occurs, the capacitive coupling voltage will be small, and the transient free component will quickly decay. The closer to the fault point, the smaller the mutual inductance voltage. When the load current is large, the remote end will induce a certain voltage. It is therefore possible to determine whether a nearby permanent earth fault has occurred by the following voltage criterion:

U _φ >Uzd

Satisfaction of this voltage criterion means that no nearby permanent earth fault has occurred.

When a two-phase non-ground fault occurs, the terminal voltage criterion will be satisfied, and it cannot be distinguished whether it is a transient or a permanent fault. But even if it is a permanent fault, when one phase is closed, there is no fault for the system. At this time, the voltage of the other tripped phase will be basically the same as the voltage of the closed phase, and the instantaneous fault does not characteristics, so it is easy to distinguish them by the method of phase separation sequence coincidence. If there is a permanent fault of non-grounding across the IAIIB line, close IA first, and then successfully restore the three-phase operation of the I circuit. At this time, the B-phase voltage (line voltage) of the II circuit will be basically the same as the A-phase voltage. At this time, the IIB will be It should not be overlapped again, but should be jumped three times, and the I loop line that has been successfully overlapped is kept running.

When a transient fault such as IAIIBCG occurs, the IBCIIA quasi-three-phase operation is retained after the trip. If the line is completely transposed, the capacitive coupling voltage and mutual inductance voltage of the healthy symmetrical three-phase tripped phase will be very small, which cannot meet the voltage criterion , both sides are considered to have serious permanent faults and do not coincide. In order to make up for the lack of terminal voltage criteria, the information of line protection should be fully utilized. If any of the following conditions is met, it is considered that there is no nearby serious fault, and the coincidence can be given:

a) The phase voltage and the phase-to-phase voltage are relatively large at the time of failure;

b) The fast protection that does not depend on the channel has no action (such as impedance I segment, power frequency variation impedance);

c) The ranging result is larger.

To sum up, the non-severe fault reclosing scheme can maximize the connection between the two ends of the system during the fault period, improve the chance of reclosing, and avoid reclosing from serious permanent faults.

As shown in Figure 1: Phase sequence reclosing features:

Coincident in phase order

Non-serious fault overlap;

Three-phase fault (three jumps) is not serious;

When the sequence coincides, the two sides exchange information to avoid double coincidence and permanent failure;

i) Coincident in phase order

Requirements: Only one phase of the two circuits overlaps at the same time;

The protection device should integrate the operation information of the two circuits and overlap according to certain rules (strategies);

Specific strategies:

Coincidence strategy 1: As shown in Figure 2, phases with the same name are preferentially overlapped and can overlap at the same time

In the system shown in Figure 2, if a phase failure occurs on the line I circuit AB and II circuit line A, phase A should be closed first, so that the normal transmission of system power can be restored as quickly as possible.

Reclosing strategy 2: As shown in Figure 3, the leading phase overlaps first; the sequence of overlapping phases: A←B←C←A In the system shown in Figure 3, if the line has faults on phase I and C of loop II and phase A of loop II, according to the overlapping phase Regardless of the order, C is ahead of A, so I will return to line C first.

Reclosing strategy 3: As shown in Figure 4, the leading phase of the two-phase fault line overlaps preferentially:

In the system shown in Figure 4, the line has phase I circuit BC and II circuit A phase faults. According to the sequence of overlapping phases, for I circuit fault phase B and C, B is ahead of C, so I circuit B phase Priority, compared with the B phase of the I circuit priority and the II circuit A, the A phase is prioritized, so the final coincidence result is to close the A of the II circuit first, then close the B of the I circuit, and finally close the C of the I circuit .

ii) non-critical permanent fault overlap

Purpose: To improve the success rate of reclosing; to avoid the impact of reclosing on the system due to severe permanent faults. The instantaneous permanent fault criterion is introduced in the adaptive reclosing logic:

Theoretical basis for non-serious fault coincidence discrimination: when a line with distributed parameters trips on a single phase or two phases, there are mutual inductance voltages and capacitive coupling voltages between non-fault relatively disconnected phases. For faults of different nature (transient or permanent), mutual inductance voltage and capacitive coupling voltage have different manifestations.

Figure 5 is a comparison of phase voltage waveforms for single-phase grounding instantaneous and permanent faults

The critical non-serious fault criterion is introduced in the adaptive reclosing logic: if any of the following conditions is met, it is considered that there is no serious fault and can be reclosed:

1) The phase voltage and phase-to-phase voltage are both greater than 50% of the rated voltage at the time of failure;

2) Impedance section I and power frequency variation impedance have no action;

3) The distance measurement result is greater than 40% of the total length of the line.

The combination of the instantaneous permanent fault criterion and the severe fault criterion can reliably determine whether the nature of the fault is a serious permanent fault, and has determined the overlap sequence of the protection on both sides of the line.

In the case of instantaneous faults, the electrical characteristics of the line induced voltage are related to whether the line is equipped with a shunt reactor, and the adaptive coincidence introduces the fault point arc extinguishing criterion based on the voltage amplitude combined with the voltage high-order harmonic content;

The theoretical basis of the arc extinguishing criterion is: for a line without shunt reactor, when an asymmetric instantaneous ground fault occurs on the line, after the two ends of the line fault phase are tripped, due to the sound capacitive and inductive coupling effect of the phase that is tripped by the fault, The continuous extinguishing and burning of the arc is caused, the waveform of the latent supply current is in the nature of repeated breakdown of the arc, and the waveform of the recovery voltage is greatly distorted.

As shown in Figure 6, it is the instantaneous fault fault phase terminal voltage (without shunt reactor). The post-recovery voltage has a sinusoidal waveform. For instantaneous faults, it must be judged that the arc is completely extinguished and the dielectric strength of the air medium around the arc track has recovered to a certain extent before reclosing.

For the secondary arc, in each power frequency cycle, when the amplitude of the recovery voltage rises to a certain level, the arc breaks down, which must contain high-order harmonics. The harmonic content is about 30% of the fundamental wave content, and the fifth harmonic content is about 20% of the fundamental wave content. Therefore, this scheme proposes the fault point arc extinguishing criterion for lines without shunt reactors:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="k"\; filenames="C20041006496000221.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; fd</span>}\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="u\; fd"\; filenames="C20041006496000222.png,C20041006496000232.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; id="1"\; label="u\; fd"\; filenames="C20041006496000222.png,C20041006496000232.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}\end{array}\right.$

k ₂ can take 0.1; k ₃ can take 0.2;

U _fd1 , U _fd3 , and U _fd5 are the amplitudes of the fundamental, third and fifth harmonics of the jump-off phase voltage, respectively.

For lines with shunt reactors, the recovery voltage rises quickly after the fault disappears. Since the frequency of the free oscillation voltage is different from the power frequency, the recovery voltage has a beat frequency phenomenon. Figure 5 shows the A-phase voltage and current waveforms during the first A-phase single-phase instantaneous artificial grounding short-circuit test of the Sichuan-Chongqing 500KV power grid with shunt reactor. The arc has been extinguished within two cycles after the fault phase tripped.

Figure 7 and Figure 8 show: Instantaneous fault fault phase terminal voltage (with shunt reactor) and artificial single-phase grounding test fault phase voltage and current waveform diagram (with shunt reactor):

For permanent ground faults, the fault phase terminal voltage does not contain free oscillation voltage, only the inductively coupled voltage of the non-fault phase to the fault phase, so for near permanent ground faults, the amplitude of disconnected phase voltage is very small; If there is a permanent ground fault, the magnitude of disconnected phase voltage may be large.

For lines with shunt reactors, due to the small reactor at the neutral point, the arc at the grounding point will be extinguished soon after the fault phase trips, so it is not necessary to judge the arc extinguishing time by calculating the harmonic content, that is, only keep formula 3; Due to the influence of free oscillation voltage, the fault phase terminal voltage contains low frequency components, and the voltage amplitude obtained by Fourier algorithm according to formula 3 will have large fluctuations. This problem can be solved by selecting the average value of certain data window data.

Therefore, for lines with shunt reactors, free oscillation voltage appears after the fault point is extinguished, so the amplitude of disconnected phase voltage will fluctuate greatly. The arc extinction criterion suitable for lines with shunt reactors proposed in this scheme for:

U _{fd1_ave} ≥k ₄ *U _N

k ₄ can take 0.2; U _{fd1_ave} is the average value of the fundamental wave voltage.

The scheme of the present invention should be the optimal scheme suitable for my country's national conditions to the important double-circuit line on the same pole. This scheme has been applied in the Honglong 500KV same-rod parallel double-circuit line of the sending system of Ertan Hydropower Station.

The present invention is provided with back-up protection:

1) It should be equipped with quick-break protection that does not depend on the channel to quickly remove serious faults nearby (such as power frequency variable impedance relay, impedance I section);

2) Staged distance protection;

3) Zero-sequence current protection.

In general, the recloser should be able to adapt to a variety of different recloser methods according to the requirements of the primary system, namely single-phase recloser, three-phase recloser, comprehensive recloser, and phase sequence recloser;

When the stability of the primary system is required, phase sequence reclosing should be used for reclosing. At this time, the protection only trips the faulty phase; when it coincides with the fault, the three-phase trips; for the 220KV and above systems, the relay protection of the double-circuit line on the same pole parallel frame has a phase-selection tripping function for cross-line faults, and only accelerates when it is not in full-phase operation. Jump off the phase; the recloser of the parallel double circuit line on the same pole is configured according to the line, and it is not recommended to share the recloser device for the double circuit line parallel on the same pole.

In order to prevent coincidence due to multi-phase permanent faults, phase sequence coincidence is adopted, that is, phase separation and coincidence jump open phases successively in sequence;

After the failure of double circuit lines paralleled on the same pole, overlap is allowed only when at least two phases with different names in the double circuit lines are healthy, otherwise, the two circuit lines must be completely disconnected; the same name of the two circuit lines should be separated and the priority should be overlapped; When a cross-line fault occurs on a parallel double-circuit line, when one circuit line is successfully reclosed, the recloser of the other circuit line is equipped with measures to prevent the reclosed line from failing again. The relay protection and reclosing of double-circuit lines paralleled on the same pole do not consider or exclude the "quasi-three-phase" operation mode of the system.

Claims (5)

1. the reclosing method of a transmission line, method to the relaying protection of double-circuit lines on the same pole road is: the independent configuration protection in every loop line road of double-circuit lines on the same pole, the main protection on double-circuit lines on the same pole road is adopted the differential current protection or is had the pilot protection of branch phase command, for various forms of single line downs and cross line fault in the district, all should select the jumping fault to realize adaptive reclose mutually: a kind of adaptive reclose that when transmission line breaks down, is applied to high pressure and extra high voltage network, route protection is accurately selecting on the basis of jumping the fault phase, carry out reclosing according to phase order in conjunction with no permanent fault criterion: promptly in order, successively divide the tripping phase that coincides; After double-circuit lines on the same pole breaks down, just allow when having at least two different names to perfect mutually in the double loop to overlap, otherwise, all trippings of two loop lines; Jump fault mutually to protect accurate choosing; During the transmission line single-phase fault, when phase to phase fault and three-phase fault, all only the fault phase is jumped in choosing, rather than phase to phase fault three is jumped; The operation information that it is characterized in that comprehensive two loop lines of protective device overlaps by following rule ordering: coincidence by dividing phase sequence to overlap, overlaps and overlaps simultaneously with the famous prime minister is preferential in proper order; The leading phase of phase to phase fault circuit preferentially overlaps; Leading phase preferentially overlaps; Determined whether to take place fault point permanent earth fault nearby: U by tripping phase voltage criterion _φ＞Uzd, U _φBe the tripping phase voltage, Uzd is a setting value, satisfies this voltage criterion and thinks nearby the permanent earth fault of not breaking down a little.

2. by the reclosing method of the described transmission line of claim 1, it is characterized in that, overlap, determine whether to have taken place permanent earth-free fault by following voltage criterion based on minute phase sequence for alternate earth-free permanent fault:

$|{\stackrel{\&CenterDot;}{U}}_P+{\stackrel{\&CenterDot;}{U}}_Y|>k_1*|{\stackrel{\&CenterDot;}{U}}_P-{\stackrel{\&CenterDot;}{U}}_Y|$

k ₁Get 4-6;

Be respectively the three-phase voltage vector, behind arbitrary combined floodgate mutually,, then be judged to alternate earth-free permanent fault, no longer continue to send out the order of phase-splitting reclosing if system satisfies the following formula condition, It is respectively the three-phase voltage vector.

3. by the reclosing method of claim 1 or 2 described transmission lines, it is characterized in that under the transient fault situation fault point reclosure time that do not automatically prolong during blow-out as yet, until the fault point blow-out, to improve the successful reclosing probability; For no shunt reactor circuit, during overlapping, self adaptation introduces based on the fault point blow-out criterion of voltage magnitude in conjunction with the voltage higher harmonic content; The blow-out criterion is:

$\left\{\begin{array}{c}{U}_{\mathrm{fd}1}\&GreaterEqual;k_2*U_N\\ (U_{\mathrm{fd}3}+U_{\mathrm{fd}5})<k_3*U_{\mathrm{fd}1}\end{array}\right.$

k ₂Get 0.1-0.2; k ₃Get 0.2-0.4;

U _Fd1, U _Fd3, U _Fd5Be respectively the amplitude of first-harmonic, three times and the quintuple harmonics of tripping phase voltage; For having the shunt reactor circuit, free oscillation voltage has appearred after the blow-out of fault point, and therefore disconnect the phase voltage amplitude and have than great fluctuation process, the blow-out criterion is:

U _{fd1_ave}≥k ₄*U _N

k ₄Get 0.2-0.4; U _{Fd1_ave}Be the mean value of fundamental voltage, U _NIt is neutral point voltage.

4. by the reclosing method of claim 1 or 2 described transmission lines; it is characterized in that reclosing is by line configuring; the relative independentability and the integrality that keep double loop protection and reclosing; automatically transfer conventional reclosing when service conditions does not satisfy to when self adaptation overlaps, it is phase to phase fault three jumpings that the tripping operation mode of protection this moment should change to usual manner automatically.

5. by the reclosing method of claim 1 or 2 described transmission lines, it is characterized in that the operation information of comprehensive two loop lines of reclosing according to phase order lock needs, whether satisfy the sound mutually condition of two different names to differentiate; The operation conditions that contains this line in the route protection for obtaining the information of another loop line, is carried out information interaction by the optical fiber connection between the protection of homonymy double loop, and the protection passage adopts optical fiber or Digital Microwave channel transfer protection information.

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