CN107492871A - A kind of flexible direct current line direction longitudinal protection method based on total current amount - Google Patents
A kind of flexible direct current line direction longitudinal protection method based on total current amount Download PDFInfo
- Publication number
- CN107492871A CN107492871A CN201710556622.6A CN201710556622A CN107492871A CN 107492871 A CN107492871 A CN 107492871A CN 201710556622 A CN201710556622 A CN 201710556622A CN 107492871 A CN107492871 A CN 107492871A
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- Prior art keywords
- current
- protection
- flexible direct
- direct current
- sense
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Classifications
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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
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0061—Details of emergency protective circuit arrangements concerning transmission of signals
- H02H1/0069—Details of emergency protective circuit arrangements concerning transmission of signals by means of light or heat rays
-
- 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
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/263—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 involving signal transmission between at least two stations involving transmissions of measured values
Abstract
The invention discloses a kind of flexible direct current line direction longitudinal protection method based on total current amount, the guard method comprises the following steps：Step 1：A current sensor is respectively installed at by the breaker at protection DC line both ends；Step 2：Measured respectively by current sensor by the instantaneous value of protection DC line both ends electric current, and be utilized respectively total current amount and differentiate sense of current；Step 3：Protection device is set at two current sensors respectively, and by fiber optic communication between protection device, protection device transmits the sense of current to opposite end and differentiates result, while the sense of current for receiving opposite end differentiates result；Step 4：When being simultaneously timing by the sense of current at protection DC line both ends, it is determined as troubles inside the sample space, by the delay of protection exit, protection exit tripping operation；Step 5：According to troubles inside the sample space criterion formula, this circuit troubles inside the sample space is determine whether, when criterion this circuit troubles inside the sample space meets, protection exit tripping operation.
Description
Technical field
The present invention relates to Relay Protection Technology in Power System field, more particularly to the flexible direct current line based on total current amount
Road direction pilot protection method.
Background technology
With in the development of voltage source converter (voltage sourced converter, VSC) and power supply and load
The increase of DC link in current transformation, flexible direct current system due to its have control flexibly, be easy to receive distributed power source with
The advantages that DC load, power supply capacity are big, the quality of power supply is good has aroused extensive attention at home and abroad.But lack ripe AC line
Road protection technique is one of significant challenge that flexible direct current system faces.The difficult point of flexible direct current system route protection is should
Quickly identification DC Line Fault to prevent device damage, accurately selects faulty line to reduce power failure range again in a short time.
Flexible direct current Line Current Differential Protection method includes at present：
1. Non-unit protection is difficult to clearly protect border, it is impossible to preferably meets that flexible direct current route protection is quick
Property and option demand.
2. current differential protection is easily influenceed by factors such as line distribution capacitance, transformer saturation and measurement errors.
3. directional pilot protection have the advantages that the traffic it is small, without communication synchronization, but currently on DC line direction
The research of pilot protection is based primarily upon jump-value of current, and the control response speed of flexible direct current system is exceedingly fast, and VSC can after failure
Basic change occurs for the quick lock in 1ms, system topological, and principle of stacking will be no longer applicable, it can be seen that being based on electric current
The directional pilot protection of Sudden Changing Rate is not suitable for flexible direct current system from principle.
It is desirable to there is a kind of flexible direct current line direction longitudinal protection method based on total current amount to overcome or extremely
Mitigate the problems of the prior art less.
The content of the invention
It is an object of the invention to provide a kind of flexible direct current line direction longitudinal protection method pair based on total current amount
The failure process of whole flexible direct current circuit shields, and is not influenceed by line distribution capacitance, without communication synchronization.
The present invention provides a kind of flexible direct current line direction longitudinal protection method based on total current amount, including following step
Suddenly：
Step 1：A current sensor is respectively installed at by the breaker at protection flexible direct current circuit both ends；
Step 2：Measured respectively by current sensor by the instantaneous value of protection flexible direct current circuit both ends electric current, and point
Li Yong not total current amount differentiation sense of current；
Step 3：Protection device is set at two current sensors respectively, passes through fiber optic communication, guarantor between protection device
Protection unit transmits the sense of current to opposite end and differentiates result, while the sense of current for receiving opposite end differentiates result；
Step 4：When being simultaneously timing by the sense of current at protection flexible direct current circuit both ends, it is determined as troubles inside the sample space, passes through
The delay of overprotection outlet, protection exit tripping operation；
Step 5：According to troubles inside the sample space criterion formula, this circuit troubles inside the sample space is determine whether, when in this line areas of criterion
When failure meets, protection exit tripping operation.
Preferably, the current sensor in the step 1 realizes wide frequency domain linear transform, and installation polarity is electric current from mother
Line point to it is described by protection flexible direct current circuit for just.
Preferably, the protection device in the step 3 is relay protector.
Preferably, the utilization total current amount in the step 2 differentiates sense of current, and its criterion is：
I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；IsetIt is a positive number for default threshold,
If criterion meets, then it is assumed that sense of current is just.
Preferably, under bipolar short-circuit conditions, there is direction character in the total current amount of fault current：Positive electrode current is from the change of current
Device flows to trouble point, and cathodal current flows to transverter from trouble point, and the step 4 utilizes the direction character of total current amount, judges
Troubles inside the sample space.
Preferably, the protection exit delay is delayed more than the maximum communication of the protection device.
The invention discloses a kind of flexible direct current line direction longitudinal protection method based on total current amount, pass through the present invention
The flexible direct current line direction longitudinal protection method based on total current amount need to only gather circuit both ends current information, without voltage
Sampling, topology is not changed and influenceed this method after by converter blocking, and whole failure process can be shielded, not by
The influence of line distribution capacitance, without communication synchronization.
Brief description of the drawings
Sense of current schematic diagram when Fig. 1 is two level VSC bipolar short troubles；
Fig. 2 is the workflow diagram of the flexible direct current line direction longitudinal protection method based on total current amount；
Fig. 3 is the protection point schematic diagram of the flexible direct current line direction pilot protection system based on total current amount；
Circuit both ends current waveform figure when Fig. 4 is troubles inside the sample space；
Circuit both ends current waveform figure when Fig. 5 is external area error；
Circuit both ends current waveform figure when Fig. 6 is load fluctuation.
Embodiment
To make the purpose, technical scheme and advantage that the present invention is implemented clearer, below in conjunction with the embodiment of the present invention
Accompanying drawing, the technical scheme in the embodiment of the present invention is further described in more detail.In the accompanying drawings, identical from beginning to end or class
As label represent same or similar element or the element with same or like function.Described embodiment is the present invention
Part of the embodiment, rather than whole embodiments.The embodiments described below with reference to the accompanying drawings are exemplary, it is intended to uses
It is of the invention in explaining, and be not considered as limiting the invention.Based on the embodiment in the present invention, ordinary skill people
The every other embodiment that member is obtained under the premise of creative work is not made, belongs to the scope of protection of the invention.Under
Embodiments of the invention are described in detail with reference to accompanying drawing for face.
As shown in figure 1, bipolar fault progression process can be divided into three phases：Electric capacity discharge regime, diode freely turn on
Stage and AC feed-in stage.
Electric capacity discharge regime, fault current mainly include the discharge current of shunt capacitor, its equivalent circuit such as Fig. 1 (a)
It is shown.The expression formula of this stage fault current is：
In formula, ifFor positive electrode fault electric current, vCFor shunt capacitor both end voltage；V0For failure initial time voltage, ω is
The vibration angular frequency of electric current, ω0For the resonance angular frequency of capacitor discharging circuit, β is the vibration phase angle difference of voltage and current；R and L
Respectively line resistance and inductance.
It was found from above formula, when ω t are in [0, π], fault current ifFor just；When ω t are more than π-β, capacitance voltage vCWill be by
Just it is being changed into negative.Significantly, since the presence of anti-parallel diodes, shunt capacitor will not be reversed charging, its electricity
Pressure is not in negative value.I.e. when ω t are equal to π-β, electric capacity discharge regime will terminate, fault current can by diode continuousing flow,
Failure enters the free conducting phase of diode.Therefore, it is in electric capacity discharge regime, the direction of fault current：Positive pole circuit flows to
Trouble point, negative pole circuit outgoing failure point.
The free conducting phase of diode, shown in equivalent circuit such as Fig. 1 (b), the expression formula of fault current is：
if=I '0e-(R/L)t (2)
I in formula0ˊ be electric capacity discharge regime at the end of fault current, i.e. (π-β)/ω moment fault current, therefore I0ˊ
For more than 0 on the occasion of.Therefore, it is still in the free conducting phase of diode, the direction of fault current：Positive pole circuit flows to failure
Point, negative pole circuit outgoing failure point.
AC feed-in stage, AC power are former to trouble point feed-in by diode rectifier bridge (transverter after locking)
Hinder the process of electric current, shown in its equivalent circuit such as Fig. 1 (c).Dominated by AC feed-in electric current in fault current direction.Due to two poles
The conducting of pipe has directionality, therefore is still in AC feed-in stage, fault current direction：Positive pole circuit flows to trouble point,
Negative pole circuit outgoing failure point.
In summary, bipolar short trouble occurs for flexible direct current system, the electric current of three failure phases after converter blocking
Directional characteristic has consistent conclusion, i.e., in its whole failure process, the direction of fault current is positive pole circuit flow direction all the time
Trouble point, negative pole circuit outgoing failure point.
For MMC, its failure process only includes electric capacity discharge regime and exchanges feed-in stage, the side of its fault current
It is consistent with above-mentioned analysis to feature.
Therefore either two level VSC or MMC, under bipolar short-circuit conditions, there is certain direction character in its electric current,
Using this direction character, the present invention proposes the direction pilot line protection method based on total current amount.
As shown in Figures 2 and 3, the workflow of guard method comprises the following steps：
Step 11：Current sensor is installed at flexible direct current circuit both ends, measures the current instantaneous value of DC line；
Step 12：By current instantaneous value compared with default threshold value, the direction of Cutoff current.Its criterion is：
I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；InFor the load current value of institute's protection circuit,
It is a positive number.If criterion meets, then it is assumed that sense of current is just；
Step 13：As shown in figure 3, by fiber optic communication, protection device transmits the sense of current to opposite end and differentiates result, simultaneously
The sense of current for receiving opposite end differentiates result；
Step 14：When the sense of current at both ends be simultaneously timing, can determine that as troubles inside the sample space, by certain outlet delay,
Protection exit trips.For the circuit within 20km, the settable 0.3ms of outlet delay.
The test result for ± 10kV the flexible direct current systems that the present invention is built on PSCAD/EMTDC is given below.
As shown in figure 4, during troubles inside the sample space, the positive electrode current rapid mutation of M sides and N sides is fast to more than 0.2In, cathodal current
Below -0.2In is arrived in speed mutation, and protection can be exported quickly.
As shown in figure 5, during external area error, the positive electrode current of N sides is all the time in below 0.2In, and the cathodal current of N sides is all the time
More than -0.2In, therefore the positive direction criterion of N sides is unsatisfactory for, and directional pilot protection is all without malfunction.
As shown in fig. 6, when load fluctuation occurs, the positive electrode current of N sides is all the time in below 0.2In, the cathodal current of N sides
All the time more than -0.2In, therefore the positive direction criterion of N sides is unsatisfactory for, and directional pilot protection is all without malfunction.
It can be seen that present invention protection has good reliability, rapidity and selectivity.
It is last it is to be noted that：The above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations.To the greatest extent
The present invention is described in detail with reference to the foregoing embodiments for pipe, it will be understood by those within the art that：It is still
Technical scheme described in foregoing embodiments can be modified, or which part technical characteristic is equally replaced
Change；And these modifications or replacement, the essence of appropriate technical solution is departed from the essence of various embodiments of the present invention technical scheme
God and scope.
Claims (6)
1. a kind of flexible direct current line direction longitudinal protection method based on total current amount, it is characterised in that comprise the following steps：
Step 1：A current sensor is respectively installed at by the breaker at protection flexible direct current circuit both ends；
Step 2：Measured respectively by current sensor by the instantaneous value of protection flexible direct current circuit both ends electric current, and profit respectively
Differentiate sense of current with total current amount；
Step 3：Protection device is set at two current sensors respectively, passes through fiber optic communication, protection dress between protection device
Put to opposite end and transmit sense of current differentiation result, while the sense of current for receiving opposite end differentiates result；
Step 4：When being simultaneously timing by the sense of current at protection flexible direct current circuit both ends, it is determined as troubles inside the sample space, by protecting
Protect the delay of outlet, protection exit tripping operation；
Step 5：According to troubles inside the sample space criterion formula, this circuit troubles inside the sample space is determine whether, when criterion this circuit troubles inside the sample space
When meeting, protection exit tripping operation.
2. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 1, it is characterised in that：
Current sensor in the step 1 realizes wide frequency domain linear transform, and installation polarity is that electric current points to described protected from bus
Flexible direct current circuit is just.
3. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 1, it is characterised in that：
Protection device in the step 3 is relay protector.
4. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 1, it is characterised in that：
Utilization total current amount in the step 2 differentiates sense of current, and its criterion is：
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I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；IsetIt is a positive number for default threshold, if
Criterion meets, then it is assumed that sense of current is just.
5. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 4, it is characterised in that：
Under bipolar short-circuit conditions, there is direction character in the total current amount of fault current：Positive electrode current flows to trouble point from transverter, bears
Electrode current flows to transverter from trouble point, and the step 4 utilizes the direction character of total current amount, judges troubles inside the sample space.
6. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 5, it is characterised in that：
The protection exit delay is delayed more than the maximum communication of the protection device.
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| CN201710556622.6A CN107492871B (en) | 2017-07-10 | 2017-07-10 | A kind of flexible direct current line direction longitudinal protection method based on total current amount |
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| CN107492871B CN107492871B (en) | 2019-01-15 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109546677A (en) * | 2018-11-07 | 2019-03-29 | 国网浙江省电力有限公司经济技术研究院 | A kind of scale offshore wind farm flexibility transmitting system safety control strategy method for solving |
| CN109839575A (en) * | 2019-04-04 | 2019-06-04 | 国家电网有限公司 | A kind of electric power system fault processing method, device and terminal device |
| CN110350500A (en) * | 2019-08-13 | 2019-10-18 | 南京南瑞继保电气有限公司 | Pseudo- bipolar DC distribution protection method, apparatus, system, equipment and medium |
| CN111614067A (en) * | 2020-06-08 | 2020-09-01 | 广州市扬新技术研究有限责任公司 | Direct current traction pilot protection system and method based on optical fiber communication |
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| WO1993016517A1 (en) * | 1992-02-12 | 1993-08-19 | Asea Brown Boveri Ab | Method and device for preventing overstabilization of longitudinal differential protection in case of internal fault |
| CN102510050A (en) * | 2011-11-08 | 2012-06-20 | 西安交通大学 | Pilot protection method for direct current line current abrupt change of multi-terminal direct current transmission system |
| CN106058828A (en) * | 2016-07-18 | 2016-10-26 | 天津大学 | Multi-terminal flexible DC power grid line direction pilot protection method |
| CN106711971A (en) * | 2017-02-09 | 2017-05-24 | 东南大学 | Method for protecting double-end direct current distribution network |
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2017
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Patent Citations (4)
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| WO1993016517A1 (en) * | 1992-02-12 | 1993-08-19 | Asea Brown Boveri Ab | Method and device for preventing overstabilization of longitudinal differential protection in case of internal fault |
| CN102510050A (en) * | 2011-11-08 | 2012-06-20 | 西安交通大学 | Pilot protection method for direct current line current abrupt change of multi-terminal direct current transmission system |
| CN106058828A (en) * | 2016-07-18 | 2016-10-26 | 天津大学 | Multi-terminal flexible DC power grid line direction pilot protection method |
| CN106711971A (en) * | 2017-02-09 | 2017-05-24 | 东南大学 | Method for protecting double-end direct current distribution network |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109546677A (en) * | 2018-11-07 | 2019-03-29 | 国网浙江省电力有限公司经济技术研究院 | A kind of scale offshore wind farm flexibility transmitting system safety control strategy method for solving |
| CN109839575A (en) * | 2019-04-04 | 2019-06-04 | 国家电网有限公司 | A kind of electric power system fault processing method, device and terminal device |
| CN110350500A (en) * | 2019-08-13 | 2019-10-18 | 南京南瑞继保电气有限公司 | Pseudo- bipolar DC distribution protection method, apparatus, system, equipment and medium |
| CN110350500B (en) * | 2019-08-13 | 2021-08-27 | 南京南瑞继保电气有限公司 | Method, device, system, equipment and medium for protecting pseudo bipolar direct current distribution network |
| CN111614067A (en) * | 2020-06-08 | 2020-09-01 | 广州市扬新技术研究有限责任公司 | Direct current traction pilot protection system and method based on optical fiber communication |
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| CN107492871B (en) | 2019-01-15 |
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