CN110518554B - Protection configuration and detection method for direct current area of direct current system - Google Patents
Protection configuration and detection method for direct current area of direct current system Download PDFInfo
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- CN110518554B CN110518554B CN201910693102.9A CN201910693102A CN110518554B CN 110518554 B CN110518554 B CN 110518554B CN 201910693102 A CN201910693102 A CN 201910693102A CN 110518554 B CN110518554 B CN 110518554B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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Abstract
The invention discloses a protection configuration and detection method for a direct current area of a direct current system, which comprises the steps of firstly configuring a lightning arrester in a symmetrical unipolar direct current system, when a unipolar ground fault occurs in the direct current area, selecting a fault electrode by using voltage thresholds of the fault electrode and a non-fault electrode by a protection device in the area, and simultaneously exiting or delaying to exit current differential or longitudinal direction criterion of the direct current positive electrode area by combining the voltage of the non-fault electrode. The method can solve the problems of protection maloperation and wrong selection of fault areas in the direct current power transmission and distribution system with the symmetrical monopole topology, thereby ensuring the reliable and stable operation of the system.
Description
Technical Field
The invention belongs to the field of direct current power transmission and distribution of an electric power system, and particularly relates to a protection configuration and detection method for a direct current area of a direct current system.
Background
The flexible direct current power transmission and distribution system adopts a voltage source type current converter, and active power and reactive power of the system can be independently and rapidly controlled, so that the stability of the system is improved, the fluctuation of system frequency and voltage is inhibited, and the steady-state performance of an alternating current system is improved.
With the development of the flexible direct current transmission technology, multi-terminal flexible direct current transmission, a flexible direct current power grid, a flexible direct current distribution network and the like are gradually popularized and applied. In flexible direct current transmission/distribution, the adopted topologies are mainly divided into two types, namely bipolar topology and symmetrical monopole topology. For the flexible direct current power transmission and distribution system adopting the symmetrical monopole, when the direct current side monopole ground fault occurs, the non-fault voltage of the flexible direct current power transmission and distribution system is raised to be 2 times of the original voltage, and serious adverse effects are brought to the system insulation, so that the lightning arrester is required to be configured to limit the voltage rise. For a non-fault electrode configured with the lightning arrester, when the voltage is too high and the lightning arrester acts to generate leakage current, the protection adopting a differential current criterion or a current direction criterion is mistakenly acted, so that the fault range is expanded, and the safety and stability margin of a system is reduced. Meanwhile, the leakage current after the action of the lightning arrester and the grounding point of the fault electrode form a current path, so that protection misoperation adopting the criteria of undervoltage, overcurrent and the like is caused.
Therefore, there is a need to find a reliable dc area protection configuration and detection method, which is applied to a dc power transmission and distribution system with symmetric monopole topology to achieve reliable protection and accurate judgment of a fault area.
Disclosure of Invention
The invention aims to provide a protection configuration and detection method for a direct current region of a direct current system, which can solve the problems of protection maloperation and fault region selection error in a direct current power transmission and distribution system with a symmetrical monopole topology, thereby ensuring the reliable and stable operation of the system.
In order to achieve the above purpose, the solution of the invention is:
a protection configuration and detection method for DC region of DC system includes configuring lightning arrester in symmetric monopole DC system, and determining if positive voltage is | Udp|＞k1UDNAnd negative electrode voltage | Udn|＜k2UDNThen the negative pole is considered as the fault pole, the positive pole is the non-fault pole, and when | Udp|＞k3Usa_refWhen the current difference criterion or the pilot direction criterion of the direct current positive pole area is exited or delayed to exit; when negative pole voltage | Udn|＞k1UDNAnd positive electrode voltage | Udp|＜k2UDNThen the anode is considered as the fault pole, the cathode is considered as the non-fault pole, and when | U |, Udn|＞0.95Usa_refWhen the current difference criterion or the pilot direction criterion of the direct current cathode area is exited or delayed to exit; wherein, UDNFor a symmetrical monopole DC system, the voltage difference between the rated positive and negative electrodes, Usa_refIs a reference voltage, k, of the lightning arrester1Coefficient of non-fault pole determination, k2For the fault pole, the coefficient, k3Is the reference voltage coefficient of the lightning arrester, k is more than 0.51＜1，0＜k2＜0.4，0.95＜k3＜1.2。
After the scheme is adopted, the necessary lightning arrester is firstly configured in the symmetrical single-pole direct-current system, when single-pole ground fault occurs in a direct-current region, the protection device in the region selects a fault pole by using voltage thresholds of the fault pole and a non-fault pole, and simultaneously, the current differential criterion or the longitudinal direction criterion of the direct-current positive pole region is quitted or delayed to be exported or not enabled to be under-voltage and over-current protection by combining the voltage of the non-fault pole, so that the maloperation of protection is avoided, and the safe and stable operation of the system is ensured.
The invention has the beneficial effects that:
(1) the invention solves the problem that the non-fault pole voltage is too high to damage equipment due to single pole grounding in a flexible direct current power transmission and distribution system adopting a symmetrical single pole topology, and simultaneously, the non-fault pole and the fault pole are accurately selected;
(2) the invention solves the problem of misoperation of actions of lightning arrester caused by adopting protection such as a differential current criterion, a current direction criterion and the like, and solves the problem of misoperation of under-voltage and over-current protection.
Drawings
Fig. 1 is a schematic diagram of a converter station with multiple dc lines and dc zones;
fig. 2 is a schematic diagram of a converter station with a single dc line and dc area;
fig. 3 is a schematic diagram of the positive and negative current paths caused by the lightning arrester after being actuated.
Detailed Description
The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.
The invention provides a protection configuration and detection method of a direct current area of a direct current system, firstly, an arrester, such as the arrester 2 arranged in the area 1 in figures 1 and 2, is configured in a symmetrical unipolar direct current system, when a negative pole earth fault occurs in a direct current area 4 shown in figure 2, a protection device in the area selects a fault pole by using voltage thresholds of the fault pole and a non-fault pole, and when a positive pole voltage | Udp|＞k1UDNAnd | Udn|＜k2UDNThe negative electrode is considered as the fault electrode, the positive electrode is considered as the non-fault electrode, and when | U |, the voltage is measureddp|＞k3Usa_refWhen the current difference criterion or the pilot direction criterion of the direct current positive pole area is exited or delayed to exit; wherein, UDNFor a symmetrical monopole DC system, the voltage difference between the rated positive and negative electrodes, Usa_refIs a reference voltage, k, of the lightning arrester1Coefficient of non-fault pole determination, k2For the fault pole, the coefficient, k3Is the reference voltage coefficient of the lightning arrester, k is more than 0.51＜1，0＜k2＜0.4，0.95＜k3＜1.2。
In the method, the scheme of the lightning arrester configured in the symmetrical unipolar direct current system is as follows: the lightning arrester is arranged at the outlet of the direct current system converter or in the direct current bus area, and when the direct current system converter only comprises one direct current line outlet, the lightning arrester can also be arranged at the direct current line end. The protection level parameters of the lightning arrester are designed as follows:
Ue＝k×Udwherein, UeFor protecting the lightning arrester from voltage, UdThe voltage is a direct current rated voltage, k is a voltage protection coefficient of the lightning arrester, and k is more than 0.5 and less than 1.0.
Usa_ref＜UeWherein, Usa_refThe reference voltage of the lightning arrester corresponds to the voltage when the lightning arrester starts to generate leakage current (the typical value of the leakage current is 1-20 mA).
In the method, the scheme of protection configuration is that protection is configured in a direct current protection device of a direct current system, a centralized protection device is configured at a direct current bus, and protection devices are respectively configured at two ends of a line.
In the method, when the current differential criterion or the pilot direction criterion of the direct current area at the delay outlet is judged, from the fault moment, the delay time is longer than the action time of the main protection with the single-pole grounding, so that the voltage differential or pilot direction criterion protection misoperation is avoided.
Fig. 1 is a schematic view of a converter station with a plurality of dc lines and a dc area, fig. 2 is a schematic view of a converter station with a single dc line and a dc area, and an arrester 2 is disposed in the area 1 in fig. 1, and an arrester 2 is disposed in the area 1 in fig. 2, or arresters are disposed in the areas 3 and 4.
In fig. 3, when a single-pole ground fault occurs at the positive electrode K, the negative electrode voltage rises by 2 times as much as the original voltage, and the lightning arrester disposed in the negative electrode bus region operates to form a current loop indicated by an arrow. When the voltage of the negative electrode is more than 0.95Usa_refAnd when the undervoltage and overcurrent protection function is not enabled, the protection judgment logic does not enable the undervoltage and overcurrent protection function, so that misoperation of undervoltage and overcurrent protection is avoided.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (7)
1. A protection configuration and detection method for a direct current area of a direct current system is characterized in that: firstly, a lightning arrester is arranged in a symmetrical unipolar direct current system, if the positive voltage is | Udp|＞k1UDNAnd negative electrode voltage | Udn|＜k2UDNThen the negative pole is considered as the fault pole, the positive pole is the non-fault pole, and when | Udp|＞k3Usa_refWhen the current difference criterion or the pilot direction criterion of the direct current positive electrode area is exited, or the current difference criterion or the pilot direction criterion of the direct current positive electrode area is delayed to exit; when negative pole voltage | Udn|＞k1UDNAnd positive electrode voltage | Udp|＜k2UDNThen the anode is considered as the fault pole, the cathode is considered as the non-fault pole, and when | U |, Udn|＞k3Usa_refWhen the current difference criterion or the pilot direction criterion of the direct current cathode area is exited, or the current difference criterion or the pilot direction criterion of the direct current cathode area is delayed to exit; wherein, UDNFor a symmetrical monopole DC system, the voltage difference between the rated positive and negative electrodes, Usa_refIs a reference voltage, k, of the lightning arrester1Coefficient of non-fault pole determination, k2For the fault pole, the coefficient, k3Is the reference voltage coefficient of the lightning arrester, k is more than 0.51＜1，0＜k2＜0.4，0.95＜k3＜1.2。
2. The method according to claim 1, wherein the method comprises the following steps: the current differential criterion of the direct current anode or cathode area is the difference or the sum of two direct currents of the direct current pole and the line of the station, when the positive directions of the direct current pole and the line are consistent, the difference is obtained, and when the positive directions of the direct current pole and the line are opposite, the sum is obtained; or the difference or the sum of the current of the direct current pole and the line and the current of the direct current pole and the line of the opposite station, when the current of the direct current pole and the line is consistent with the positive direction of the current of the direct current pole and the line of the opposite station, the difference is taken, and when the current of the direct current pole and the line is opposite to the positive direction of the current of the direct current pole and the line of the opposite station, the sum is taken.
3. The method according to claim 1, wherein the method comprises the following steps: the longitudinal direction criterion of the direct current area is the current change rate and change direction of the direct current pole and the line of the station or the current change rate and change direction of the direct current pole and the line of the station.
4. The method according to claim 1, wherein the method comprises the following steps: the positions of the lightning arrester arranged in the symmetrical monopole direct current system are as follows: configuring a lightning arrester at an outlet of a direct current system converter or in a direct current bus area; when the direct current system converter only comprises one direct current line outlet, the lightning arrester is configured at the direct current system converter outlet, in the direct current bus area or at the direct current line end.
5. The method according to claim 1, wherein the method comprises the following steps: the protection level parameters of the lightning arrester are designed as follows:
Ue＝k×Udwherein, UeFor protecting the lightning arrester from voltage, UdThe voltage is a direct current rated voltage, k is a voltage protection coefficient of the lightning arrester, and k is more than 0.5 and less than 1.0;
Usa_ref＜Uewherein, Usa_refThe reference voltage for the arrester corresponds to the voltage at which the arrester starts to exhibit leakage currents.
6. The method according to claim 1, wherein the method comprises the following steps: when the delay outlet current differential criterion or the pilot direction criterion is carried out, from the fault moment, the delay time is longer than the action time of the single-pole grounded main protection.
7. The method according to claim 1, wherein the method comprises the following steps: when the non-fault voltage is greater than 0.95Usa_refThe protection decision logic does not enable the under-voltage and over-current protection function.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107317311A (en) * | 2017-06-06 | 2017-11-03 | 国网浙江省电力公司电力科学研究院 | Dc circuit breaker operating criterion in a kind of symmetrical monopolar flexible direct current power transmission system |
| CN108092236A (en) * | 2017-11-29 | 2018-05-29 | 中国能源建设集团江苏省电力设计院有限公司 | A kind of overvoltage protection configuration system of THE UPFC |
| EP3416256A1 (en) * | 2017-06-13 | 2018-12-19 | General Electric Technology GmbH | High voltage direct current converter harmonic filtering and protection system |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107317311A (en) * | 2017-06-06 | 2017-11-03 | 国网浙江省电力公司电力科学研究院 | Dc circuit breaker operating criterion in a kind of symmetrical monopolar flexible direct current power transmission system |
| EP3416256A1 (en) * | 2017-06-13 | 2018-12-19 | General Electric Technology GmbH | High voltage direct current converter harmonic filtering and protection system |
| CN108092236A (en) * | 2017-11-29 | 2018-05-29 | 中国能源建设集团江苏省电力设计院有限公司 | A kind of overvoltage protection configuration system of THE UPFC |
Non-Patent Citations (1)
| Title |
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| 采用直流断路器的对称单极多端柔性直流故障清除策略;汪楠楠等;《电力系统自动化》;20190325;第122-128页 * |
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