CN103354355A - Method and device for networked protection of microgrid - Google Patents

Abstract

The invention discloses a method and a device for networked protection of a microgrid. Voltage and current information of a line is collected through intelligent electronic devices (IEDs) dispersedly installed on a main transformer, a bus and two sides of a power grid line; a main power grid is judged to break down or not according to a set fault detection method; operating states of the main power grid and the microgrid are monitored continuously when the main power grid is judged to operate normally, a networked monitoring system is put into operation when the main power grid is judged to break down, the intelligent electronic devices (IEDs) first judge a line on which a fault occurs according to fault direction information, and then send fault judgment information to a protection control host. According to the invention, real-time monitoring is carried out on the microgrid by adopting a networked protection system, thereby enabling the microgrid protection to become an organic unity, coordinating with each other, realizing protection for the selectivity, the rapidity, the sensitivity and the reliability of the microgrid, ensuring safe and stable operation of the microgrid system, and improving the utilization rate and the reliability of distributed generation (DG).

Description

A kind of little electrical network networking guard method and device

Technical field

The present invention relates to a kind of little electrical network networking guard method and device.The protection field that belongs to little electrical network.

Background technology

Little electrical network is the very important part of intelligent grid, it is made of distributed power source DG, load and electrical power trans mission/distribution system, can independent operating or be incorporated into the power networks with large electrical network, have the miniature electric power system to internal electric source and Coordinated optimal control function.

Little electrical network is owing to having the little electrical network of a plurality of sons, distributed power source DG and load; and the ability of the short circuit current that dissimilar distributed power source DG provides is relevant with its control strategy; distributed power source DG contributes the difference of short circuit current so that protect the calculating of adjusting more complicated; trend is for two-way circulating, and operates in that short circuit current varies in size under networking pattern and the island mode.It is greatly different that the exclusive characteristics of the both-end of micro power network or multi-terminal network have determined that its resist technology and traditional distribution protection have; guarantee selectivity, rapidity, sensitivity and the reliability of the protection system of little electrical network; being the key of micro power network protection, also is the difficult point of micro power network protection.

The general traditional a certain dot information of collection circuit of micro-grid system after the at present distributed power source DG access, and by with pre-set protection definite value come relatively to determine whether fault occurs.In the situation that distributed power source DG permeability is larger, this protected mode that only reflects a certain dot information of circuit can't satisfy distributed power source DG access to the requirement of electric network protection system aspect the protection control.Usually adopt syllogic current protection and pilot protection.

Adopt the syllogic current protection, have the following disadvantages:

1) easily causes non-fault element protection or route protection malfunction, thereby make protection lose selectivity, enlarge the accident impact scope.

2) cause element protection or route protection sensitivity, protection tripping when serious.

The weak point of pilot protection: main transformer, bus, circuit both sides all need to configure differential protection independent of each other, and protective device lacks coordination and interaction mechanism, and increase equipment investment.

Summary of the invention

One of purpose of the present invention; in order to overcome in the prior art that the protection equipment investment is high, protective capability is poor and easily to enlarge the weak point such as accident impact scope; a kind of little electrical network networking guard method is provided; the small investment of the method; can improve the reliability of protection system, make protective value more stable.Two of purpose of the present invention is for a kind of little electrical network networking protective device is provided, and this protective device simple in structure can improve utilance and the reliability of power supply DG.

One of purpose of the present invention is achieved through the following technical solutions:

A kind of little electrical network networking guard method; it is characterized in that: by set up communication system in electrical network, the collection of realization multipoint data information and mutual forms network monitoring system; carry out Real-Time Monitoring and control with the running status to little electrical network, specifically comprise the steps:

1) gathers the voltage and current information of circuit by the smart electronics unit IED that disperses to be installed in main transformer device, bus, power network line both sides;

2) according to the fault detection method of setting, judge whether main electrical network breaks down, when judging that main network system is normally moved, continue to monitor the running status of main electrical network and little electrical network, when judging main electrical network and break down, this moment, smart electronics unit IED at first judged the circuit that fault occurs according to fault direction information, then fault judgement information was sent to the protection main control system;

3) the protection main control system is received after the fault detect information of smart electronics unit IED transmission, according to fault detect Information Selection protection control strategy, at first can failure judgement downstream distribution formula power supply DG islet operation for the protection main control system, if can islet operation, then the circuit breaker to the faulty line two ends sends trip signal, with the faulty line excision, allow distributed power source DG continue to power to downstream load; If downstream distribution formula power supply DG can not islet operation; then protect main control system to send trip signal to the anti-island protect device of distributed power source DG first; allow distributed power source DG out of service, with the protection micro-grid system; then the circuit breaker to the faulty line two ends sends trip signal; with the faulty line excision, realize little electrical network networking protection.

Further scheme of the present invention: every circuit at main electrical network and little electrical network is provided with smart electronics unit IED with each correspondence of each circuit breaker.

Further scheme of the present invention: smart electronics unit IED bear information gathering, fault detect and execution, and the protection main control system between exchange message, the work of sending trip signal to circuit breaker, specifically comprise:

1) as information collecting device, the operation of power networks information that the collection secondary device provides and the action status information of each circuit breaker;

2) as fault detect and performance element, by with system in other smart electronics unit IED information relatively, determine the section of fault generation by carrying out fault detection algorithm;

3) bear the backup protection function of adjacent smart electronics unit IED, when adjacent smart electronics unit IED or circuit breaker break down, by information exchange, for adjacent lines provides backup protection;

4) communicate with the protection main control system, fault message is reached the protection main control system, receive simultaneously the protection actuating signal that the protection main control system sends;

5) circuit breaker to correspondence sends trip signal.

Further scheme of the present invention: the 2nd), described fault detect is the core of networked protection scheme, and the fault detection method of employing is based on Longitudinal comparison principle, the substance of this fault detection method have following some:

1) all be equipped with in the both sides of circuit can failure judgement the smart electronics unit IED of direction, the corresponding circuit breaker of each smart electronics unit IED or current transformer;

2) divide in advance well main protection zone and the backup protection zone of each smart electronics unit IED, can improve like this protection efficient, also can reduce the pressure of communication system;

3) for the smart electronics unit IED that is connected with distributed power source DG, need to cooperate with the anti-island protect of distributed power source DG distributed power source DG excision that can not islet operation when detecting busbar fault;

4) there is the relation table of the protected equipment such as all circuits, bus, distributed power source DG in this smart electronics unit IED and its maximum protection zone each IED inside, smart electronics unit;

5) each smart electronics unit IED carries out conformity calculation with the fault direction information that other smart electronics unit IED transmits, and compares with the threshold values that sets in advance, determines fault generation circuit.

Further scheme of the present invention: when failure judgement direction smart electronics unit IED carries out fault detect step 2), mainly based on following two coefficients:

1) direction coefficient f

Expression formula is as follows:

F represents the fault direction estimate of situation of direction component among each smart electronics unit IED,

2) incidence coefficient g

Expression formula is as follows:

In the formula, n ₁＞n ₂, calculate for simplifying, get n ₂=1, n ₁With

Value then relevant with network configuration; G represents the correlation degree of the relatively studied smart electronics of other smart electronics unit IED unit IED, it has characterized the Output rusults of diverse location smart electronics unit IED to the influence degree of fault judgement, overcome the impact that the IED tripping of smart electronics unit brings fault detect by incidence coefficient g

Take protected element as elementary cell; with the output as smart electronics unit IED self of the product of f and g; adopt the Output rusults addition of the following formula smart electronics unit IED that protected location is corresponding, obtain the failure criterion result of protected object i, represent with following expression:

$F_{\mathrm{outi}}=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{f}_n\×g_n$

In the formula: F _OutiBe the fault judged result to protected object i; N is the quantity of smart electronics unit IED corresponding to protected element;

As F corresponding to circuit i _OutiFor on the occasion of and satisfy expression formula (1), then represent circuit i fault,

$F_{\mathrm{outi}}\left\{\begin{array}{c}\≥F_{\mathrm{thi}}\\ >F_{\mathrm{outj}}\end{array}\right.---\left(1\right)$

In the formula, F _ThiBe the threshold value of circuit i fault judged result, its value principle is: when any one tripping among smart electronics unit IED corresponding to circuit i, f=0, according to the result that expression formula (1) calculates, F _OutjFault judged result corresponding to other circuit during for circuit i fault;

For busbar fault, if F corresponding to bus m _OutmValue then represents bus m fault for negative value and when satisfying condition shown in the following formula,

$F_{\mathrm{outm}}\left\{\begin{array}{c}\&le;F_{\mathrm{thm}}^{\&prime;}\\ <F_{\mathrm{outn}}\end{array}\right.$

In the formula, F _OutmValue principle is identical with the value principle of the fault judged result of circuit protected object i,

Be the threshold value of bus m fault judged result, value principle is identical with the value principle of circuit fault threshold values, F _OutnFault judged result corresponding to other bus during for bus m fault.

Two of purpose of the present invention is achieved through the following technical solutions:

A kind of little electrical network networking protective device is characterized in that: comprise monitoring and protection layer, wall and process layer; The monitoring and protection layer is made of the protection main control system; Wall comprises some smart electronicses unit IED, and described smart electronics unit IED has information gathering, fault detect and execution, sends the trip signal electrical structure with protection main control system exchange message with to circuit breaker; Process layer comprises interval switch, circuit breaker, mutual induction of voltage EVT summation current transformer ECT; The distribute input/output end port place of the interval switch that is arranged on process layer, circuit breaker, mutual induction of voltage EVT summation current transformer ECT of the smart electronics unit IED of wall, the information exchange network of forming process layer and wall; The protection main control system adopts each smart electronics unit IED of Ethernet or optical networking access wall, forms the Real Time Monitoring network to distributed power source DG.

Further scheme of the present invention: described smart electronics unit IED is made of switching input module, analog input module, defencive function module, output module and communication module.

Beneficial effect of the present invention:

1, Adoption Network protection system of the present invention is carried out Real Time Monitoring to little electrical network; so that little electric network protection becomes the Organic unity body; cooperation each other; selectivity, rapidity, sensitivity and frequency converter to micro-grid system have been realized; can guarantee fully the safe and stable operation of micro-grid system, greatly improve the reliability of micro-grid system.

2, little electrical network networking protective device is simple in structure; has healthy and strong reliably communication system; realized that the collection of multipoint data information is with mutual; make the rapid action message of protection; satisfy simultaneously the demand of main protection and backup protection; can also cooperate with the anti-island protect of distributed power source DG, when fault, allow can not islet operation distributed power source DG in time out of service, improve utilance and the reliability of distributed power source DG.

3, having remedied traditional relay protection can't satisfy and contain the defective that distributed power source DG accesses the protection demand of little electrical network.

Description of drawings

Fig. 1 is the rear networking protection of distributed power source DG access structured flowchart in the specific embodiment 1.

Fig. 2 is communication network architecture block diagram in the specific embodiment 1.

Fig. 3 is the functional block diagram of smart electronics unit IED in the specific embodiment 1.

Fig. 4 is distributed power source DG access 10kv micro-grid system simulation model figure in the specific embodiment 1.

Fig. 5 is the smart electronics unit IED criterion table as a result when circuit L4 breaks down among Fig. 4.

Fig. 6 is as a result table of the smart electronics unit IED criterion of Fig. 4 median generatrix B3 when breaking down.

Embodiment

The present invention is further illustrated below in conjunction with accompanying drawing.

Such as Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 and a kind of little electrical network networking protective device shown in Figure 6, comprise monitoring and protection layer 1, wall 2 and process layer 3; Monitoring and protection layer 1 is made of the protection main control system; Wall 2 comprises some smart electronicses unit IED, and described smart electronics unit IED has information gathering, fault detect and execution, sends the trip signal electrical structure with protection main control system exchange message with to circuit breaker; Process layer 3 comprises interval switch, circuit breaker, mutual induction of voltage EVT summation current transformer ECT; The distribute input/output end port place of the interval switch that is arranged on process layer 3, circuit breaker, mutual induction of voltage EVT summation current transformer ECT of the smart electronics unit IED of wall 2, the information exchange network of forming process layer 3 and wall 2; The protection main control system adopts each smart electronics unit IED of Ethernet or optical networking access wall 2, forms the Real Time Monitoring network to distributed power source DG.Be connected with distributed power source DG1, distributed power source DG2, distributed power source DG3, distributed power source DG4 and distributed power source DG5 on the bus, the feeder line of distributed power source DG1, distributed power source DG2, distributed power source DG3, distributed power source DG4 and distributed power source DG5 is provided with some smart electronicses unit IED and points of common connection PCC.Some smart electronicses unit IED to network-bus, is transferred to protection main control system by network-bus by each IED Internet Transmission again.

As shown in Figure 2: the input of protection main control system links to each other with the output of man-machine interface; the input/output end port of protection system main control system links to each other with the input/output end port of each smart electronics unit IED respectively; control the information of each smart electronics unit IED collected current instrument transformer ECT; obtain sampled value; and control the trip signal that each smart electronics unit IED starts interval switch, circuit breaker, mutual induction of voltage EVT is carried out sampled value control.

Described smart electronics unit IED is made of switching input module, analog input module, defencive function module, output module and communication module.

As shown in Figure 3: bus links to each other with smart electronics unit IED; be connected with circuit breaker and TA on the circuit; circuit breaker links to each other with the switching input module of smart electronics unit IED; TA links to each other with the analog input module of smart electronics unit IED, and the defencive function module by smart electronics unit IED links to each other with the distributed protection communication network with communication module.

A kind of little electrical network networking guard method, by set up communication system in electrical network, the collection of realization multipoint data information and mutual forms network monitoring system, carries out Real-Time Monitoring and control with the running status to little electrical network, specifically comprises the steps:

1) gathers the voltage and current information of circuit by the smart electronics unit IED that disperses to be installed in main transformer device, bus, power network line both sides;

2) according to the fault detection method of setting, judge whether main electrical network breaks down, when judging that main network system is normally moved, continue to monitor the running status of main electrical network and little electrical network, when judging main electrical network and break down, this moment, smart electronics unit IED at first judged the circuit that fault occurs according to fault direction information, then fault judgement information was sent to the protection main control system; Described fault direction information is as the comparison information of fault detection algorithm; the amount of information that transmits is few, simple and reliable, after fault occurs; each smart electronics unit IED is by comparing the fault direction information of all smart electronics unit IED in the maximum protection zone, failure judgement generation circuit.

3) the protection main control system is received after the fault detect information of smart electronics unit IED transmission, according to fault detect Information Selection protection control strategy, at first can failure judgement downstream distribution formula power supply DG islet operation for the protection main control system, if can islet operation, then the circuit breaker to the faulty line two ends sends trip signal, with the faulty line excision, allow distributed power source DG continue to power to downstream load; If downstream distribution formula power supply DG can not islet operation; then protect main control system to send trip signal to the anti-island protect device of distributed power source DG first; allow distributed power source DG out of service, with the protection micro-grid system; then the circuit breaker to the faulty line two ends sends trip signal; with the faulty line excision, realize little electrical network networking protection.

Every circuit at main electrical network and little electrical network is provided with smart electronics unit IED with each correspondence of each circuit breaker.

Smart electronics unit IED bear information gathering, fault detect and execution, and the protection main control system between exchange message, the work of sending trip signal to circuit breaker, specifically comprise:

1) as information collecting device, the operation of power networks information that the collection secondary device provides and the action status information of each circuit breaker;

2) as fault detect and performance element, by with system in other smart electronics unit IED information relatively, determine the section of fault generation by carrying out fault detection algorithm;

Described fault detect is the core of networked protection scheme, and the fault detection method of employing is based on Longitudinal comparison principle, the substance of this fault detection method have following some:

1. the smart electronics unit IED of energy failure judgement direction all is housed, the corresponding circuit breaker of each smart electronics unit IED or current transformer in the both sides of circuit;

2. divide in advance main protection zone and the backup protection zone of good each smart electronics unit IED, can improve like this protection efficient, also can reduce the pressure of communication system;

3. for the smart electronics unit IED that is connected with distributed power source DG, need to cooperate with the anti-island protect of distributed power source DG distributed power source DG excision that can not islet operation when detecting busbar fault;

4. there is the relation table of the protected equipment such as all circuits, bus, distributed power source DG in this smart electronics unit IED and its maximum protection zone each IED inside, smart electronics unit;

5. each smart electronics unit IED carries out conformity calculation with the fault direction information that other smart electronics unit IED transmits, and compares with the threshold values that sets in advance, determines fault generation circuit.

3) bear the backup protection function of adjacent smart electronics unit IED, when adjacent smart electronics unit IED or circuit breaker break down, by information exchange, for adjacent lines provides backup protection;

4) communicate with the protection main control system, fault message is reached the protection main control system, receive simultaneously the protection actuating signal that the protection main control system sends;

5) circuit breaker to correspondence sends trip signal.

When failure judgement direction smart electronics unit IED carries out fault detect in the described step 2, mainly based on following two coefficients:

1) direction coefficient f

Expression formula is as follows:

F represents the fault direction estimate of situation of direction component among each smart electronics unit IED,

2) incidence coefficient g

Expression formula is as follows:

In the formula, n ₁＞n ₂, calculate for simplifying, get n ₂=1, n ₁With

Value then relevant with network configuration; G represents the correlation degree of the relatively studied smart electronics of other smart electronics unit IED unit IED, it has characterized the Output rusults of diverse location smart electronics unit IED to the influence degree of fault judgement, overcome the impact that the IED tripping of smart electronics unit brings fault detect by incidence coefficient g

Take protected element as elementary cell; with the output as smart electronics unit IED self of the product of f and g; adopt the Output rusults addition of the following formula smart electronics unit IED that protected location is corresponding, obtain the failure criterion result of protected object i, represent with following expression:

$F_{\mathrm{outi}}=\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{f}_n\&times;g_n$

In the formula: F _OutiBe the fault judged result to protected object i; N is the quantity of smart electronics unit IED corresponding to protected element;

As F corresponding to circuit i _OutiFor on the occasion of and satisfy expression formula (1), then represent circuit i fault,

$F_{\mathrm{outi}}\left\{\begin{array}{c}\&GreaterEqual;F_{\mathrm{thi}}\\ >F_{\mathrm{outj}}\end{array}\right.---\left(1\right)$

In the formula, F _ThiBe the threshold value of circuit i fault judged result, its value principle is: when any one tripping among smart electronics unit IED corresponding to circuit i, f=0, according to the result that expression formula (1) calculates, F _OutjFault judged result corresponding to other circuit during for circuit i fault;

For busbar fault, if F corresponding to bus m _OutmValue then represents bus m fault for negative value and when satisfying condition shown in the following formula,

$F_{\mathrm{outm}}\left\{\begin{array}{c}\&le;F_{\mathrm{thm}}^{\&prime;}\\ <F_{\mathrm{outn}}\end{array}\right.$

In the formula, F _OutmValue principle is identical with the value principle of the fault judged result of circuit protected object i,

Be the threshold value of bus m fault judged result, value principle is identical with the value principle of circuit fault threshold values, F _OutnFault judged result corresponding to other bus during for bus m fault.

The judgement that a key character of networking protection system is exactly fault and the action of protection rely on network communicating system; the enforcement of every step all depends on this; therefore communication structure and the communication protocol that can satisfy the protection needs must be arranged; and the support of strong bottom communication network is arranged, the network configuration of described networked protection system has:

1) data transmission bauds is fast

Because protection system is had relatively high expectations to the synchronism of information, require each dot information real-time exchange also can upload to synchronously the protection main control system.

2) communication network is reliably healthy and strong

3) data message standard definition

Because equipment is more in the protection system, the device of dissimilar, difference in functionality and different manufacturers is arranged.Satisfy the interoperability of these devices, the transmission of data message must have the assurance of standardization agreement

4) communication strategy of finishing emergency function is arranged

The networking protection scheme will satisfy the function of main protection and backup protection simultaneously, when fault occurs, finishes the function of backup protection by communication strategy.

Operation principle of the present invention: the circuit at distributed power source DG arranges some smart electronicses unit IED; in the network system normal course of operation; information by the continual collection network each point of each smart electronics unit IED; the collection of realization multipoint data information and mutual; monitor the running status of network system; determine faulty line by fault detection algorithm; then each smart electronics unit IED reaches the protection main control system with the information of each point; the protection main control system judges according to the fault detect information of receiving again; select the protection strategy and send instruction; in case the system of judging breaks down; then protection system is devoted oneself to work immediately; faulty line is excised in the circuit breaker action of faulty line two ends.

As shown in Figure 4, the 10kv micro-grid system of the present embodiment after the distributed power source DG access be as example, when the below discusses respectively line fault and busbar fault, and the action situation of fault detection system.Comprise distributed power source DG1, distributed power source DG2, distributed power source DG3, distributed power source DG4, smart electronics unit IED1,,,, smart electronics unit IED14, bus B1, bus B2,,, bus B6, circuit L1, circuit L2,,, circuit L5.

Distributed power source DG1 is by bus B2, bus B3 links to each other with bus B1 with bus 4, bus B1 links to each other with electrical network, bus B2 provides load 1, bus B3 provides load 2, bus B4 provides load 3, be provided with smart electronics unit IED0 between bus B1 and the electrical network, the circuit L1 of bus B1 and bus B2 is provided with smart electronics unit IED1, smart electronics unit IED2, the circuit L2 of bus B2 and bus B3 is provided with smart electronics unit IED3, smart electronics unit IED4, the circuit L3 of bus B3 and bus B3 is provided with smart electronics unit IED5, smart electronics unit IED6 is provided with smart electronics unit IED11 between bus 4 and the distributed power source DG1.

Distributed power source DG2 links to each other with bus B1 with bus B3 by bus B2, is provided with smart electronics unit IED12 between bus B3 and the distributed power source DG2.

Distributed power source DG3 links to each other with bus B1 by bus B5, bus B5 provides load 4, the circuit L4 of bus B1 and bus B5 is provided with smart electronics unit IED7, smart electronics unit IED8, is provided with smart electronics unit IED13 between bus B5 and the distributed power source DG3.

Distributed power source DG4 links to each other with bus B1 by bus B6, bus 6 provides load 5, the circuit L5 of bus B1 and bus B6 is provided with smart electronics unit IED9, smart electronics unit IED10, is provided with smart electronics unit IED14 between bus B6 and the distributed power source DG4.

1) line fault

Take smart electronics unit IED7 as research object, the criterion result when discussion circuit L4 breaks down.The Minimal Protective zone of smart electronics unit IED7 is circuit L4 and bus B1, and the maximum protection zone also has circuit L1, L5 and bus B5 except L4 and B1.When circuit L4 breaks down, the result of failure criterion as shown in Figure 5, Fig. 5 is smart electronics unit IED7 maximum protection locality protection device relationships.

As shown in Figure 5, only have the failure criterion result of L4 to satisfy formula

$F_{\mathrm{outi}}\left\{\begin{array}{c}\&GreaterEqual;F_{\mathrm{thi}}\\ >F_{\mathrm{outj}}\end{array}\right.$ And formula $F_{\mathrm{outm}}\left\{\begin{array}{c}\&le;F_{\mathrm{thm}}^{\&prime;}\\ <F_{\mathrm{outn}}\end{array}\right..$

Can judge thus, fault occurs on the circuit L4.Simultaneously; smart electronics unit IED7 and smart electronics unit IED8 can send to information the protection main control system; if protected host judges that DG3 can islet operation; then smart electronics unit IED7 and smart electronics unit IED8 can send trip signal to circuit breaker 7 and the circuit breaker 8 of correspondence; with the faulty line excision, DG3 continues to power to downstream load.If DG3 can not islet operation, then protected host sends trip signal to the anti-island protect of DG3 configuration, the anti-island protect action of DG3, and with the DG3 excision, faulty line is excised in then smart electronics unit IED7 and smart electronics unit IED8 action.

Each IED inside, smart electronics unit have one as above the table shown in the fault detect computational chart, after fault occurs, each smart electronics unit IED presses the fault direction judged result of other smart electronics unit of listed collection IED in the table as direction coefficient f, and the value of incidence coefficient g determines in advance, and the product of f and g is as the Output rusults of smart electronics unit IED self.

2) busbar fault

For the bus that distributed power source DG access is arranged, the smart electronics unit IED of distributed power source DG place branch road need to cooperate with the anti-island protect of distributed power source DG configuration.In micro-grid system shown in Figure 4; take smart electronics unit IED4 as research object, the Minimal Protective zone of smart electronics unit IED4 comprises circuit L2 and bus B3, and the maximum protection zone is except L2 and B3; also comprise bus B2, circuit L3 and distributed power source DG2.When bus B3 broke down, the result of failure criterion was shown in Figure 6, and Fig. 6 is smart electronics unit IED4 maximum protection locality protection device relationships.

As seen from Figure 6, only have the judged result of bus B3 to satisfy formula

$F_{\mathrm{outi}}\left\{\begin{array}{c}\&GreaterEqual;F_{\mathrm{thi}}\\ >F_{\mathrm{outj}}\end{array}\right.$ And formula $F_{\mathrm{outm}}\left\{\begin{array}{c}\&le;F_{\mathrm{thm}}^{\&prime;}\\ <F_{\mathrm{outn}}\end{array}\right.,$

Can judge thus is bus B3 fault.When the bus of judging distributed power source DG access as smart electronics unit IED breaks down, can send trip signal to smart electronics unit IED corresponding to distributed power source DG, make distributed power source DG out of service.

Described specific embodiment only is to the explanation for example of the present invention's spirit herein; its protection range is not limited to the described content of the present embodiment; anyly be familiar with those skilled in the art in the scope that the present invention discloses; be equal to replacement or change according to technical scheme of the present invention and inventive concept thereof, all belonged to protection scope of the present invention.

Claims (7)

1. little electrical network networking guard method; it is characterized in that: by set up communication system in electrical network, the collection of realization multipoint data information and mutual forms network monitoring system; carry out Real-Time Monitoring and control with the running status to little electrical network, specifically comprise the steps:

1) gathers the voltage and current information of circuit by the smart electronics unit IED that disperses to be installed in main transformer device, bus, power network line both sides;

2) according to the fault detection method of setting, judge whether main electrical network breaks down, when judging that main network system is normally moved, continue to monitor the running status of main electrical network and little electrical network, when judging main electrical network and break down, this moment, smart electronics unit IED at first judged the circuit that fault occurs according to fault direction information, then fault judgement information was sent to the protection main control system;

3) the protection main control system is received after the fault detect information of smart electronics unit IED transmission, according to fault detect Information Selection protection control strategy, at first can failure judgement downstream distribution formula power supply DG islet operation for the protection main control system, if can islet operation, then the circuit breaker to the faulty line two ends sends trip signal, with the faulty line excision, allow distributed power source DG continue to power to downstream load; If downstream distribution formula power supply DG can not islet operation; then protect main control system to send trip signal to the anti-island protect device of distributed power source DG first; allow distributed power source DG out of service, with the protection micro-grid system; then the circuit breaker to the faulty line two ends sends trip signal; with the faulty line excision, realize little electrical network networking protection.

2. a kind of little electrical network networking guard method according to claim 1, it is characterized in that: every circuit at main electrical network and little electrical network is provided with smart electronics unit IED with each correspondence of each circuit breaker.

3. a kind of little electrical network networking guard method according to claim 1 and 2; it is characterized in that: smart electronics unit IED bear information gathering, fault detect and execution, and the protection main control system between exchange message, the work of sending trip signal to circuit breaker, specifically comprise:

1) as information collecting device, the operation of power networks information that the collection secondary device provides and the action status information of each circuit breaker;

2) as fault detect and performance element, by with system in other smart electronics unit IED information relatively, determine the section of fault generation by carrying out fault detection algorithm;

3) bear the backup protection function of adjacent smart electronics unit IED, when adjacent smart electronics unit IED or circuit breaker break down, by information exchange, for adjacent lines provides backup protection;

4) communicate with the protection main control system, fault message is reached the protection main control system, receive simultaneously the protection actuating signal that the protection main control system sends;

5) circuit breaker to correspondence sends trip signal.

4. a kind of little electrical network networking guard method according to claim 3; it is characterized in that: the 2nd); described fault detect is the core of networked protection scheme, and the fault detection method of employing is based on Longitudinal comparison principle, the substance of this fault detection method have following some:

1) all be equipped with in the both sides of circuit can failure judgement the intelligent electronic device IED of direction, the corresponding circuit breaker of each smart electronics unit IED or current transformer;

2) divide in advance well main protection zone and the backup protection zone of each smart electronics unit IED, can improve like this protection efficient, also can reduce the pressure of communication system;

3) for the smart electronics unit IED that is connected with distributed power source DG, need to cooperate with the anti-island protect of distributed power source DG distributed power source DG excision that can not islet operation when detecting busbar fault;

4) there is the relation table of the protected equipment such as all circuits, bus, distributed power source DG in this smart electronics unit IED and its maximum protection zone each IED inside, smart electronics unit;

5) each smart electronics unit IED carries out conformity calculation with the fault direction information that other smart electronics unit IED transmits, and compares with the threshold values that sets in advance, determines fault generation circuit.

5. a kind of little electrical network networking guard method according to claim 1 is characterized in that: step 2) when middle failure judgement direction smart electronics unit IED carries out fault detect, mainly based on following two coefficients:

1) direction coefficient f

Expression formula is as follows:

F represents the fault direction estimate of situation of direction component among each smart electronics unit IED,

2) incidence coefficient g

Expression formula is as follows:

In the formula, n ₁＞n ₂, calculate for simplifying, get n ₂=1, n ₁With Value then relevant with network configuration; G represents the correlation degree of the relatively studied smart electronics of other smart electronics unit IED unit IED, it has characterized the Output rusults of diverse location smart electronics unit IED to the influence degree of fault judgement, overcome the impact that the IED tripping of smart electronics unit brings fault detect by incidence coefficient g

Take protected element as elementary cell; with the output as smart electronics unit IED self of the product of f and g; adopt the Output rusults addition of the following formula smart electronics unit IED that protected location is corresponding, obtain the failure criterion result of protected object i, represent with following expression:

$F_{\mathrm{outi}}=\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{f}_n\&times;g_n$

In the formula: F _OutiBe the fault judged result to protected object i; N is the quantity of smart electronics unit IED corresponding to protected element;

As F corresponding to circuit i _OutiFor on the occasion of and satisfy expression formula (1), then represent circuit i fault,

$F_{\mathrm{outi}}\left\{\begin{array}{c}\&GreaterEqual;F_{\mathrm{thi}}\\ >F_{\mathrm{outj}}\end{array}\right.---\left(1\right)$

In the formula, F _ThiBe the threshold value of circuit i fault judged result, its value principle is: when any one tripping among smart electronics unit IED corresponding to circuit i, f=0, according to the result that expression formula (1) calculates, F _OutjFault judged result corresponding to other circuit during for circuit i fault;

For busbar fault, if F corresponding to bus m _OutmValue then represents bus m fault for negative value and when satisfying condition shown in the following formula,

$F_{\mathrm{outm}}\left\{\begin{array}{c}\&le;F_{\mathrm{thm}}^{\&prime;}\\ <F_{\mathrm{outn}}\end{array}\right.$

In the formula, F _OutmValue principle is identical with the value principle of the fault judged result of circuit protected object i, Be the threshold value of bus m fault judged result, value principle is identical with the value principle of circuit fault threshold values, F _OutnFault judged result corresponding to other bus during for bus m fault.

6. a kind of little electrical network networking protective device according to claim 1 is characterized in that: comprise monitoring and protection layer (1), wall (2) and process layer (3); Monitoring and protection layer (1) is made of the protection main control system; Wall (2) comprises some smart electronicses unit IED, and described smart electronics unit IED has information gathering, fault detect and execution, sends the trip signal electrical structure with protection main control system exchange message with to circuit breaker; Process layer (3) comprises interval switch, circuit breaker, mutual induction of voltage EVT summation current transformer ECT; The distribute input/output end port place of the interval switch that is arranged on process layer (3), circuit breaker, mutual induction of voltage EVT summation current transformer ECT of the smart electronics unit IED of wall (2), the information exchange network of forming process layer (3) and wall (2); The protection main control system adopts each smart electronics unit IED of Ethernet or optical networking access wall (2), forms the Real Time Monitoring network to distributed power source DG.

7. a kind of little electrical network networking protective device according to claim 6, it is characterized in that: described smart electronics unit IED is made of switching input module, analog input module, defencive function module, output module and communication module.

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