CN111371076B - Differential protection method and system suitable for direct-current power distribution network line - Google Patents
Differential protection method and system suitable for direct-current power distribution network line Download PDFInfo
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- CN111371076B CN111371076B CN202010169634.5A CN202010169634A CN111371076B CN 111371076 B CN111371076 B CN 111371076B CN 202010169634 A CN202010169634 A CN 202010169634A CN 111371076 B CN111371076 B CN 111371076B
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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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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention discloses a differential protection method and a differential protection system suitable for a direct-current power distribution network line, wherein the method comprises the following steps: acquiring instantaneous current values of a differential protection device at the same side and a differential protection device at the opposite side of a direct current distribution network line, and calculating current variation of differential protection at the same side of the direct current distribution network line; determining current variation differential current according to the current variation of the differential protection at two sides; and matching the adaptive differential protection action characteristic according to the current variation differential current so as to output and control the differential protection action signal. The differential protection action control is carried out through the current variation, so that the reliable and rapid action can be carried out on the unipolar ground fault which has inconspicuous fault current variation on the direct current distribution network line, and the sensitivity of the differential protection of the direct current distribution network line is greatly improved; the method can also achieve sensitive judgment and reliable and quick action for bipolar short-circuit faults with violent electric quantity change on the direct current distribution network line.
Description
Technical Field
The invention relates to a differential protection method and a differential protection system suitable for a direct-current power distribution network line, and belongs to the technical field of direct-current power distribution networks.
Background
The existing direct current distribution network line differential protection mainly adopts real-time sampling values on two sides of a line to calculate differential current and can act only after the ratio braking equation is required to be met.
However, the load current of the pseudo bipolar direct current power distribution network can still keep the original characteristic to operate temporarily when the unipolar earth fault occurs, the current value of the line unipolar earth fault is only about dozens of amperes, and compared with the load current, the load current is small, the braking current adopting a real-time sampling value is large, so that the ratio of the differential current to the braking current is small, the fault characteristic is not obvious, and the problem of insufficient sensitivity is caused when the unipolar earth fault occurs by adopting the differential protection method adopting the real-time sampling value. If the sensitivity of differential protection with single-pole fault is improved by pertinently adopting a lower action value and a lower rate brake coefficient, the problem of misoperation caused by electric quantity disturbance may occur; and the action delay is additionally increased to avoid misoperation caused by disturbance, so that the action speed is lower when the real fault occurs.
When a bipolar short-circuit fault occurs in a direct-current power distribution network line, the current on two sides of the line is sharply increased, and the problem of insufficient sensitivity can be solved by adopting a differential protection method of real-time sampling values. However, for the dc system, it is necessary to remove the fault as fast as possible to protect the power electronic device, and the differential protection method using the real-time sampling value needs an extra delay to avoid the malfunction caused by abnormal conditions such as sampling error. Therefore, for bipolar short-circuit faults, the existing differential protection method adopting real-time sampling values has the problem that reliability and rapidity cannot be considered at the same time.
Therefore, a differential protection method with sensitivity, reliability and speed is urgently sought.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a novel differential protection method and system suitable for a direct-current power distribution network line.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the present invention provides a differential protection method for a dc power distribution network line, the method comprising the steps of:
acquiring instantaneous current values of a differential protection device at the same side and a differential protection device at the opposite side of a direct current distribution network line, and calculating current variation of differential protection at the same side of the direct current distribution network line;
determining current variation differential current according to the current variation of the differential protection at two sides;
and matching the adaptive differential protection action characteristic according to the current variation differential current so as to output and control the differential protection action signal.
With reference to the first aspect, further, the current variation is calculated by using the following equation:
ΔI (t) ＝I (t) -I (t-T)
in the formula: delta I (t) The current variation quantity of differential protection at the same side of a direct current distribution network line at the T moment relative to the T-T moment is represented; I.C. A (t) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the moment t of the direct-current distribution network line is represented; i is (t-T) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the T-T moment of the direct-current distribution network line is represented; t represents a preset time interval.
With reference to the first aspect, further, the differential protection operation characteristic includes a high operation value characteristic and a low operation value characteristic.
With reference to the first aspect, further, the high action value characteristic means that if n consecutive sampling points in the sampling sequence satisfy a corresponding current variation differential protection action equation, a delay T is passed H And outputting an action signal of the current variation differential protection, wherein n is larger than 4.
With reference to the first aspect, further, the low action value characteristic means that when m consecutive sampling points in the sampling sequence satisfy a corresponding current variation differential protection action equation, a delay T is passed L Outputting an action signal of current variation differential protection, wherein: t is L ＞T H (ii) a m is greater than 5 and m is greater than n.
With reference to the first aspect, further, the current variation differential protection action equation is as follows:
wherein: delta I dΦ Representing the differential current, Δ I, of the amount of current change dΦ ＝|ΔI MΦ +ΔI NΦ |；ΔI rΦ Representing the amount of current change the braking current, Δ I rΦ ＝|ΔI MΦ -ΔI NΦ |；ΔI MΦ The current variation of the differential protection device at the current side of the direct-current distribution network line is represented; delta I NΦ The current variation of the differential protection device on the opposite side of the direct-current distribution network line is represented; k represents a rate brake coefficient corresponding to the action value characteristic; i is set An operation value corresponding to the operation value characteristic is indicated.
With reference to the first aspect, further, the high action value characteristic is applicable to a bipolar short-circuit fault, and the low action value characteristic is applicable to a unipolar ground fault.
In a second aspect, the present invention provides a differential protection system for a dc power distribution network, the system comprising:
a sampling module: the device is used for acquiring instantaneous current values of a local side differential protection device and an opposite side differential protection device of a direct-current distribution network circuit;
a calculation module: the current variable quantity is used for calculating the current variable quantity of differential protection on the same side of the direct current distribution network circuit;
a determination module: the current variation differential current is determined according to the current variation of the differential protection at two sides;
a matching control module: the differential protection circuit is used for matching adaptive differential protection action characteristics according to the current variation differential current so as to output and control differential protection action signals.
In a third aspect, the present invention further provides a differential protection system suitable for a dc power distribution network, including a processor and a storage medium;
the storage medium is to store instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of any of the preceding methods.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method of any of the preceding claims.
Compared with the prior art, the differential protection method and the differential protection system applicable to the direct-current power distribution network line provided by the invention at least have the following beneficial effects:
differential protection action control is carried out by utilizing the characteristic that differential current of current variation is generated only when a line has a fault, the sampling error of a real-time sampling value is not required to be considered, and the reliability of differential protection action when the line of the direct-current power distribution network has a fault, particularly when a bipolar short-circuit fault occurs, can be obviously improved;
according to the current variation and the differential current matching with the corresponding differential protection action characteristics, the corresponding action time delay can be set for the unipolar grounding fault and the bipolar short-circuit fault respectively, and the sensitivity of the unipolar grounding fault and the rapidity of the bipolar short-circuit fault removal are improved.
Drawings
Fig. 1 is a flowchart of a differential protection method applied to a dc distribution network line according to an embodiment of the present invention;
fig. 2 is a current waveform diagram of differential protection on two sides of a line when a positive ground fault occurs in a dc power distribution network line according to an embodiment of the present invention;
FIG. 3 is a graph of the positive current variation differential current waveform at the time of the positive ground fault, obtained from FIG. 2;
FIG. 4 is a graph of the braking current waveform at the positive current variation at the time of the positive ground fault, as determined in FIG. 2;
fig. 5 is a current waveform diagram of differential protection at two sides of a line when a bipolar short-circuit fault occurs in a dc power distribution network line according to an embodiment of the present invention;
FIG. 6 is a graph of the variation of the positive current differential current at the time of the bipolar short-circuit fault, as determined in FIG. 5;
fig. 7 is a waveform diagram of the braking current according to the amount of change in the positive electrode current at the time of the bipolar short-circuit fault, which is obtained from fig. 5.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Differential protection in a direct current distribution network line is a pair of the current side and the opposite side of the direct current distribution network line, and instantaneous current sampling is realized through current acquisition modules arranged at switches on two sides of the direct current distribution network line. And the differential protection at the two sides of the direct current distribution network line carries out data interaction information through the optical fiber channel.
The differential protection method applicable to the direct-current power distribution network line provided by the embodiment of the invention is realized based on the direct-current power distribution network line structure, and as shown in fig. 1, the method comprises the following steps:
acquiring instantaneous current values of a differential protection device at the same side and a differential protection device at the opposite side of a direct current distribution network line, and calculating current variation of differential protection at the same side of the direct current distribution network line;
calculating current variation differential current according to the current variation of the differential protection at two sides;
and carrying out differential protection action signal output control according to the differential protection action characteristic matched with the current variation differential current.
The differential protection method provided by the embodiment of the invention utilizes the characteristic that the differential current of the current variation quantity is generated only when the line has a fault to carry out differential protection action control, does not need to consider the sampling error of a real-time sampling value, and can obviously improve the reliability of the differential protection action when the line of the direct-current power distribution network has a fault, especially when the double-pole short-circuit fault occurs; according to the current variation differential current matching corresponding differential protection action characteristics, adaptive action time delay can be set for the single-pole grounding fault and the double-pole short-circuit fault respectively, and the sensitivity of the single-pole grounding fault and the rapidity of the double-pole short-circuit fault removal are improved.
The instantaneous current value may be a positive electrode instantaneous current value or a negative electrode instantaneous current value of the differential protection. However, it should be noted that sampling time of the instantaneous current values of the differential protection on both sides should be kept synchronous, so as to ensure that current variation of the differential protection on both sides is calculated at the same time. Taking the time t as an example, the current variation in the embodiment of the present invention is calculated and obtained by using the following equation:
ΔI (t) ＝I (t) -I (t-T) (1)
in the formula: delta I (t) The current variation quantity of differential protection at the same side of a direct current distribution network line at the T moment relative to the T-T moment is represented; i is (t) The instantaneous current value of the positive pole or the negative pole of the differential protection at the moment t of the direct-current power distribution network line is represented; i is (t-T) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the T-T moment of the direct-current distribution network line is represented; t represents a preset time interval, and considering that T should be greater than the duration of current distortion when the dc distribution network fails, in the embodiment of the present invention, T may be 5 milliseconds.
In order to realize differential protection not only for a single-pole ground fault but also for a double-pole short-circuit fault, the embodiment of the invention sets a high action value characteristic for the double-pole short-circuit fault and sets a low action value characteristic for the single-pole ground fault. The high action value characteristic means that continuous n sampling points in a sampling sequence meet the corresponding current variable differential protection action equation and then pass through a time delay T H Outputting an action signal of current variation differential protection, wherein: n is greater than 4. The low action value characteristic means that m continuous sampling points in a sampling sequence meet the corresponding current variable differential protection action equation and then pass through a time delay T L Outputting an action signal of current variation differential protection, wherein: m is greater than 5 and m is greater than n. Operation delay T when satisfying high operation value characteristic H Operation delay T smaller than that satisfying the low operation value characteristic L In the present embodiment T H A value of 1ms, T L The value is 5 ms.
The following current variation differential protection action equation is adopted for both the high action value characteristic and the low action value characteristic:
wherein: delta I dΦ Indicating the differential current, Δ I, of the amount of current change dΦ ＝|ΔI MΦ +ΔI NΦ |；ΔI rΦ Representing the amount of current change, braking current, Δ I rΦ ＝|ΔI MΦ -ΔI NΦ |；ΔI MΦ The current variation of the differential protection device at the current side of the direct-current distribution network line is represented; delta I NΦ The current variation of the differential protection device on the opposite side of the direct-current distribution network line is represented; k represents a rate brake coefficient corresponding to the behavior value characteristic, and k is H A rate of braking coefficient, k, representing a high action value characteristic L The braking coefficient of rate representing the characteristic of low action value, k in the embodiment of the invention H The value may be 0.3, k L The value of (b) is 0.1; i is set Represents an action value corresponding to the action value characteristic as I setH Indicating an action value corresponding to a high action value characteristic, I setL Indicating an action value corresponding to a low action value characteristic, I setH The value may be 1.2 times I N ，I setL May take a value of 0.12 times I N ，I N The rated current is a primary value of the DC distribution network. I is setH And k H The value of (1) is used for sensitively reflecting the bipolar short circuit fault on the direct current distribution network line. I is setL And k L The value of (A) is used for sensitively reflecting the single-pole grounding fault with unobvious electric quantity change on the direct-current distribution network line.
The effectiveness of the differential protection method provided by the embodiment of the present invention is described below by using a positive ground fault and a bipolar short fault, respectively:
as shown in fig. 2, after a positive ground fault occurs on a dc power distribution network line, both differential protection devices can reflect fault characteristics through positive current, and the positive current of the differential protection device on the current side and the positive current of the differential protection device on the opposite side both have a variation amount with an increased value of about 60A. Based on the well-known circuit superposition principle, the variation of the positive current of the side differential protection device and the positive current of the opposite side differential protection device can be inferred to be the fault current generated by the positive earth fault. Calculating the differential current and the braking current of the current variation of the positive electrodes of the differential protection at two sides by using a formula (1), and substituting the differential current and the braking current into a formula (2)The obtained positive electrode current change amount differential current and braking current are shown in fig. 3 and 4, respectively. It can be found that the positive electrode current variation amount differential current rapidly increases after the occurrence of a failure, and the value thereof is continuously larger than the set low operation value I setL 60A (the horizontal broken line in fig. 3 represents the low action value 60A), and since the value of the braking current is small due to the amount of change in the positive electrode current, the braking coefficient of the ratio thereof after the differential current is larger than the low action value also satisfies the equation, which satisfies the condition that m consecutive sampling points in the sampling sequence satisfy the equation. Thus, via T L After the delay time of 5ms, a current variation differential protection action signal is output, and the differential protection action signal can be a switching value signal used for controlling the corresponding circuit breaker to execute a tripping action.
The analysis of the occurrence of a double-pole short-circuit fault on a direct-current power distribution network line is similar to that of a positive-pole ground fault. Both sides differential protection reflect the fault characteristics in the positive current sampling, as shown in fig. 5. The current of the positive electrode at the side and the current of the positive electrode at the opposite side are both obviously increased. And (3) calculating by using a formula (1), obtaining the differential current and the braking current of the positive current change quantity on two sides, and substituting the differential current and the braking current into a differential protection equation of a formula (2). The obtained positive electrode current variation differential current and braking current are shown in fig. 6 and 7, respectively. It can be seen that the positive variation differential current rapidly increases after a fault and its value is continuously greater than the set high action value I setH＝ 600A (the horizontal dotted line in fig. 6 represents a high action value 600A), and since the positive electrode current variation amount braking current has a small value, the ratio braking coefficient also satisfies the equation after the differential current is greater than the high action value, which conforms to the condition that N consecutive sampling points satisfy the equation among N consecutive sampling sequences. Warp beam T H＝ After the 1ms delay, a current variation differential protection action signal is output, and similarly, the differential protection action signal may also be a switching value signal for controlling the corresponding circuit breaker to execute a trip action.
The embodiment of the invention also provides a differential protection system suitable for the direct-current power distribution network, which comprises:
a sampling module: the device is used for acquiring instantaneous current values of a local side differential protection device and an opposite side differential protection device of a direct-current power distribution network circuit;
a calculation module: the current variable quantity is used for calculating the current variable quantity of differential protection on the same side of the direct current distribution network circuit;
a determination module: the current variation differential current is determined according to the current variation of the differential protection at two sides;
a matching control module: the differential protection circuit is used for matching adaptive differential protection action characteristics according to the current variation differential current so as to output and control differential protection action signals.
The differential protection system provided by the embodiment of the present invention can be used to implement the differential protection method, for example, the calculation module may be configured to calculate the current variation by using the following equation:
ΔI (t) ＝I (t) -I (t-T)
in the formula: delta I (t) The current variation quantity of differential protection at the same side of a direct current distribution network line at the T moment relative to the T-T moment is represented; i is (t) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the moment t of the direct-current distribution network line is represented; i is (t-T) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the T-T moment of the direct-current distribution network line is represented; t represents a preset time interval.
The embodiment of the invention also provides a differential protection system suitable for the direct-current power distribution network, which can also be used for the differential protection method, and comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of any of the preceding methods.
Embodiments of the present invention also provide a computer-readable storage medium, on which a computer program is stored, which when executed by a processor implements the steps of any of the methods described above.
In summary, the differential protection system and the computer readable storage medium provided in the embodiments of the present invention can perform differential protection action control through the current variation amount when executing the differential protection method, and can perform reliable and fast actions on a single-pole ground fault on a dc power distribution network line, where the fault current amount variation is not obvious, so as to greatly improve the sensitivity of the dc power distribution network line differential protection; the method can also achieve sensitive judgment and reliable and quick action for bipolar short-circuit faults with violent electric quantity change on the direct current distribution network line.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a system for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction system which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A differential protection method suitable for a direct current distribution network line is characterized by comprising the following steps:
acquiring instantaneous current values of a differential protection device at the same side and a differential protection device at the opposite side of a direct current distribution network line, and calculating current variation of differential protection at the same side of the direct current distribution network line;
determining current variation differential current according to the current variation of the differential protection at two sides;
according to the current variation differential current matching adaptive differential protection action characteristic, the differential protection action signal output control is carried out;
the differential protection action characteristic comprises a high action value characteristic and a low action value characteristic; the high action value characteristic is applicable to a bipolar short circuit fault and the low action value characteristic is applicable to a unipolar ground fault.
2. The differential protection method for the direct-current distribution network line according to claim 1, wherein the current variation is obtained by calculating according to the following equation:
ΔI (t) ＝I (t) -I (t-T)
in the formula: delta I (t) The current variation quantity of the differential protection T moment on the same side of the direct current distribution network line relative to the T-T moment is represented; I.C. A (t) Representing the t-time differential of a direct-current distribution network lineProtecting the instantaneous current value of the anode or the cathode; i is (t-T) The instantaneous current value of the positive electrode or the negative electrode of the differential protection at the T-T moment of the direct-current distribution network line is represented; t represents a preset time interval.
3. The differential protection method suitable for the direct-current power distribution network line according to claim 1, wherein the high action value characteristic means that if n continuous sampling points in a sampling sequence satisfy a corresponding current variation differential protection action equation, a delay T is passed H Outputting an action signal of current variation differential protection, wherein: n is greater than 4.
4. The differential protection method suitable for the direct current distribution network line according to claim 3, wherein the characteristic of the low action value means that if m continuous sampling points in a sampling sequence satisfy corresponding current variation differential protection action equations, a delay T is passed L Outputting an action signal of current variation differential protection, wherein: t is L ＞T H M is greater than 5 and m is greater than n.
5. The differential protection method suitable for the direct current distribution network line according to claim 3 or 4, wherein the current variation differential protection action equation is as follows:
wherein: delta I dΦ Indicating the differential current, Δ I, of the amount of current change dΦ ＝|ΔI MΦ +ΔI NΦ |；ΔI rΦ Representing the amount of current change, braking current, Δ I rΦ ＝|ΔI MΦ -ΔI NΦ |；ΔI MΦ The current variation of the differential protection device at the current side of the direct-current distribution network line is represented; delta I NΦ The current variation of the differential protection device on the opposite side of the direct-current distribution network line is represented; k represents a rate brake coefficient corresponding to the action value characteristic; i is set Indicating correspondence with the characteristic of the action valueAn action value.
6. A differential protection system for a dc power distribution network, the system comprising:
a sampling module: the device is used for acquiring instantaneous current values of a local side differential protection device and an opposite side differential protection device of a direct-current power distribution network circuit;
a calculation module: the current variable quantity is used for calculating the current variable quantity of differential protection on the same side of the direct current distribution network circuit;
the determining module: the current variation differential current is determined according to the current variation of the differential protection at two sides;
a matching control module: the differential protection circuit is used for matching adaptive differential protection action characteristics according to the current variable differential current so as to output and control differential protection action signals;
the differential protection operating characteristics include a high operating value characteristic and a low operating value characteristic; the high action value characteristic is applicable to a double short circuit fault and the low action value characteristic is applicable to a single pole ground fault.
7. A differential protection system suitable for a direct current distribution network is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 5.
8. Computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, is adapted to carry out the steps of the method of any one of claims 1 to 5.
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| CN106877298A (en) * | 2017-03-27 | 2017-06-20 | 上海交通大学 | MMC HVDC system dc line protection methods |
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