CN104852366A - Short circuit fault protection method for DC power distribution system with resistance type superconducting current limiter - Google Patents

Abstract

The invention provides a protection method for a DC power distribution system with a resistance type superconducting current limiter. DC voltage and DC current information acquired from the installing part of head end protection of all feed-out lines is utilized, the voltage sudden variable principle is applied to act as fault starting elements of DC buses and DC lines, the transient peak over-current protection principle is applied to act as I-phase protection of the DC lines, and transient over-current started time-limited undervoltage protection is applied to act as II-phase protection of the DC lines based on DC circuit breakers so that the overall length of the lines is protected. Influence on protection of the DC power distribution system caused by accessing of the current limiter can be effectively avoided, and fault lines can be rapidly cut.

Description

Containing the direct-flow distribution system short trouble guard method of resistive superconducting flow restricter

Art

The present invention relates to field of relay protection in power, be specifically related to the guard method for the direct-flow distribution system short trouble containing resistive superconducting flow restricter.

Background technology

Intelligent grid is the new advancement that world today's power system development is changed, and is great scientific and technical innovation and the development trend of 21 century electric power system.Intelligent grid future thrust mainly concentrates on power distribution network, is actively developing field of distribution network perspective study in the world.

The final electricity consumption form of increasing household electrical appliance and office electrical equipment is direct current at present, as mobile phone, liquid crystal display, computer, electric automobile etc.; Increasing household loads and industrial load are for raising the efficiency employing converter technique, and these loads can be considered indirect d. c load.The electric power simultaneously partly produced based on the distributed power generation of regenerative resource is direct current, as photovoltaic generation, fuel cell power generation.Thus a kind of natural solution of raising the efficiency and reducing energy consumption is just created---use direct-flow distribution system.Direct-flow distribution system has that the quality of power supply is high, reliability is high, good economy performance, transmission capacity are large, electric energy loss is low, topological structure is simple and adapts to the advantages such as distributed power source (Distributed Generator, DG) access.But because direct-flow distribution system needs a large amount of electric capacity to carry out voltage stabilizing and filtering; when being short-circuited fault; electric capacity sparks; produce very large transient short circuit current; huge infringement is caused to system and equipment; IGBT locking due to autoprotection simultaneously, this makes voltage-source type rectifier become uncontrollable rectifier, and DC voltage electric current is more uncontrollable.Therefore, the cooperation of the development need flow restricter of direct-flow distribution system, and resistive superconducting flow restricter (SFCL) responds fast, that loss is little current-limiting apparatus as a kind of, can meet the requirement of direct-flow distribution system to flow restricter.

The typical direct-flow distribution system topology diagram containing resistive superconducting flow restricter as shown in Figure 1, use 10kV AC system as main power supply, distribution current conversion station through 10/3.8kV transformer and rectifier composition is rectified into 10kV direct current, is directly connected on 10kV DC bus; System feeds out circuit and is divided into three sections, and load is connected to DC bus by direct current cables.

Summary of the invention

The present invention proposes a kind of guard method for the direct-flow distribution system containing resistive superconducting flow restricter.Technical scheme of the present invention is as follows:

A kind of direct-flow distribution system short trouble guard method containing resistive superconducting flow restricter; utilize the direct voltage, the direct current information that respectively feed out circuit head end protection installation place and collect; based on DC circuit breaker; use voltage jump amount principle as the fault initiating element of DC bus and DC line; transient peaks overcurrent protection principle is as the I segment protect of DC line; the time undervoltage protection that transient state overcurrent starts is as the II segment protect of DC line; protection circuit total length, is specially:

If 1. direct voltage Sudden Changing Rate Δ u exceedes setting value Δ u _{_ set}, start route protection;

2. after route protection starts, if line current peak value and electric current are to the ratio of peaking be greater than transient peaks overcurrent protection setting value illustrate that fault occurs in circuit 80% length range, then should disconnect the DC circuit breaker on this faulty line immediately;

If 3. line current peak value and electric current are to the ratio of peaking be greater than transient current protection seting value and pass through after the time delay of time, now DC voltage is less than the setting value of under-voltage protection illustrate that fault occurs in beyond circuit 80% length, if now the I segment protect of downstream line is not operating, then should disconnect the DC circuit breaker on this faulty line immediately.

4. for the circuit of direct-flow distribution system least significant end, then configure two-part overcurrent protection, as long as line current is greater than setting value, then should disconnect the DC circuit breaker on this circuit immediately, overcurrent protection is as the backup protection of this circuit in limited time.

Preferably, step 2. in transient peaks overcurrent protection setting value wherein I _kpeakend1for peak value of short during line end metallicity intereelectrode short-circuit fault; Δ t _kpeakend1for the time to current peak from fault; for safety factor, get 1.2-1.3.

Step transient current protection seting value 3. ${\left(\frac{I_{\mathrm{peak}}}{\mathrm{\Δt}}\right)}_{\mathrm{set}\·1}^{\mathrm{II}}=K_{\mathrm{rel}}^{\mathrm{II}}\×{\left(\frac{I_{\mathrm{peak}}}{\mathrm{\Δt}}\right)}_{\mathrm{set}\·2}^I=K_{\mathrm{rel}}^{\mathrm{II}}\×K_{\mathrm{rel}}^I\×\left(\frac{I_{k\·\mathrm{peak}\·\mathrm{end}\·2}}{{\mathrm{\Δt}}_{k\·\mathrm{peak}\·\mathrm{end}\·2}}\right),$ $t_{\mathrm{set}\·1}^{\mathrm{II}}=t_2^I+\mathrm{\Δt},U_{\mathrm{set}\·1}^{\mathrm{II}}=K_{u\·\mathrm{rel}}^{\mathrm{II}}\×U_N,$ Wherein for the transient current protection seting value of downstream line; for safety factor, get 1.1-1.2; U _nfor system cloud gray model rated voltage; for safety factor, get 0.5-0.6; for circuit breaker intrinsic operate time; Δ t is breaker actuation time delay, gets 0.1-0.3s.

Compared with prior art, beneficial effect of the present invention is:

1. this method is applicable to the situation of the direct-flow distribution system generation DC side metallicity intereelectrode short-circuit containing resistive superconducting flow restricter.Effectively can evade flow restricter access to the impact of direct-flow distribution system protection, excise faulty line fast.

2., during DC line 80% internal fault, protection system reliably can send trip command at about 3ms; Beyond DC line 80% during fault, protection system can send trip command by about the 3ms after given time delay reliably, ensure that the reliability of protection system, quick-action, selectivity and sensitivity.

2. accompanying drawing explanation

Fig. 1 is direct-flow distribution system test model topology diagram;

Fig. 2 is current peak and the ratio of electric current to peaking and the relation curve of abort situation;

Fig. 3 is the guard method flow chart of the direct-flow distribution system containing resistive superconducting flow restricter.

Embodiment

In order to overcome the deficiencies in the prior art; the invention provides a kind of guard method for the direct-flow distribution system containing resistive superconducting flow restricter; the protection philosophy that this protection scheme uses is simple; during line fault, rapidity is good, reliability is high, for the safe and reliable operation of direct-flow distribution system provides technical support.

In order to realize foregoing invention object, the present invention takes following technical scheme:

The invention provides the line protection method for the direct-flow distribution system short trouble containing resistive superconducting flow restricter, described scheme comprises the following steps:

Step 1: judge whether voltage jump amount exceedes threshold value, determines starting component whether action: according to the protection installation place direct voltage u information gathered, calculate direct voltage Sudden Changing Rate Δ u in real time.If the Δ u calculated is the double direct voltage Sudden Changing Rate setting value Δ u exceeding protection and start _set, then startup separator discriminating program, enters step 2; Otherwise protection fault distinguishing program does not start.

Step 2: judge whether current peak is greater than the threshold value of protection with the ratio to the time of peaking; This step is that DC line fault differentiates.If in this method, current peak is greater than with the ratio to the time of peaking the setting value protecting I section, namely the then DC circuit breaker of this circuit of tripping immediately.The computing formula of transient current protection seting value is wherein I _kpeakend1for peak value of short during line end metallicity intereelectrode short-circuit fault; Δ t _kpeakend1for the time to current peak from fault; for safety factor, be generally 1.2-1.3.

Step 3: determine DC line short trouble, and disconnect DC circuit breaker.

This step is that DC line end fault differentiates.If in this method, current peak is greater than with the ratio to the time of peaking the setting value protecting II section, and after certain time delay, now direct voltage is lower than protection seting value, namely $(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}>{\left(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}\right)}_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}})\&cap;(t=t_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}})\&cap;(U_{\mathrm{dc}}<U_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}})$ Then should disconnect the DC circuit breaker on this side line road immediately, be specially:

If line current peak value and electric current are to the ratio of peaking be greater than transient current protection seting value and pass through after the time delay of time, now DC voltage is less than the setting value of under-voltage protection illustrate that fault occurs in beyond circuit 80% length, if now the I segment protect of downstream line is not operating, then should disconnect the DC circuit breaker on this faulty line immediately; The II segment protect of lines upstream is coordinated by the I segment protect of time delay and downstream line, ensures the selectivity of system.Being chosen for of the time undervoltage protection setting value that transient state overcurrent starts ${\left(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}\right)}_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=K_{\mathrm{rel}}^{\mathrm{II}}\&times;{\left(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}\right)}_{\mathrm{set}\&CenterDot;2}^I=K_{\mathrm{rel}}^{\mathrm{II}}\&times;K_{\mathrm{rel}}^I\&times;\left(\frac{I_{k\&CenterDot;\mathrm{peak}\&CenterDot;\mathrm{end}\&CenterDot;2}}{{\mathrm{\&Delta;t}}_{k\&CenterDot;\mathrm{peak}\&CenterDot;\mathrm{end}\&CenterDot;2}}\right),t_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=t_2^I+\mathrm{\&Delta;t},U_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=K_{u\&CenterDot;\mathrm{rel}}^{\mathrm{II}}\&times;U_N,$ Wherein for the transient current protection seting value of downstream line; for safety factor, be generally 1.1-1.2; U _nfor system cloud gray model rated voltage; for safety factor, generally can be taken as 0.5-0.6; for circuit breaker intrinsic operate time; Δ t is breaker actuation time delay, is generally taken as 0.1-0.3s.

Below in conjunction with drawings and Examples, the present invention is described in further detail.

The guard method of the direct-flow distribution system line short fault containing resistive superconducting flow restricter provided by the invention is applied in as shown in Figure 1 on direct-flow distribution system test model, carries out case verification.

The present invention uses electromagnetic transient simulation software PSCAD to build this instance model, and during steady operation, each electric parameters of system is as shown in table 1.

Table 1 direct-flow distribution system electric parameters

Based on current peak during short trouble as shown in Figure 2 and the ratio of time and the relation curve of abort situation that reach peak value, the present invention has formulated the line protection method flow chart containing the direct-flow distribution system of resistive superconducting flow restricter as shown in Figure 3.Join protection four property requires and protection scheme parameter tuning principle, and the present invention is as shown in table 2 arranges each parameter tuning value in protection act criterion.

Table 2 direct-flow distribution system parameter tuning value

In PSCAD model, arrange the short trouble of circuit nine diverse locations, be 30% of each circuit, 80% and 100% place's fault respectively.The data of direct voltage, direct current before and after fault are input to by the failure criterion of MATLAB programming realization, draw to draw a conclusion:

(1) in protection scheme, fault initiating element is very sensitive, and when DC line breaks down, starting component can start bus and route protection in 1ms.

(2), when DC line 80% length is with internal fault, protection system reliably can send trip command at about 3ms; And during fault, in order to ensure the selectivity protected, needing through time delay, the operate time of sacrificing protection, but after time delay, still can send trip signal in the time of about 3ms beyond circuit 80% scope.

By PSCAD and MATLAB simulating, verifying, demonstrate guard method and can meet protection reliability, quick-action, selectivity and sensitivity requirements, confirm the feasibility of the direct-flow distribution system guard method containing resistive superconducting flow restricter.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.

Claims (3)

1. the direct-flow distribution system short trouble guard method containing resistive superconducting flow restricter; utilize the direct voltage, the direct current information that respectively feed out circuit head end protection installation place and collect; based on DC circuit breaker; use voltage jump amount principle as the fault initiating element of DC bus and DC line; transient peaks overcurrent protection principle is as the I segment protect of DC line; the time undervoltage protection that transient state overcurrent starts is as the II segment protect of DC line; protection circuit total length, is specially:

If 1. direct voltage Sudden Changing Rate Δ u exceedes setting value Δ u _{_ set}, start route protection;

2. after route protection starts, if line current peak value and electric current are to the ratio of peaking be greater than transient peaks overcurrent protection setting value illustrate that fault occurs in circuit 80% length range, then should disconnect the DC circuit breaker on this faulty line immediately;

If 3. line current peak value and electric current are to the ratio of peaking be greater than transient current protection seting value and pass through after the time delay of time, now DC voltage is less than the setting value of under-voltage protection illustrate that fault occurs in beyond circuit 80% length, if now the I segment protect of downstream line is not operating, then should disconnect the DC circuit breaker on this faulty line immediately;

4. for the circuit of direct-flow distribution system least significant end, then configure two-part overcurrent protection, as long as line current is greater than setting value, then should disconnect the DC circuit breaker on this circuit immediately, overcurrent protection is as the backup protection of this circuit in limited time.

2. guard method according to claim 1, is characterized in that, step 2. in transient peaks overcurrent protection setting value wherein I _kpeakend1for peak value of short during line end metallicity intereelectrode short-circuit fault; Δ t _kpeakend1for the time to current peak from fault; for safety factor, generally get 1.2-1.3.

3. guard method according to claim 1, is characterized in that, step transient current protection seting value 3. ${\left(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}\right)}_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=K_{\mathrm{rel}}^{\mathrm{II}}\&times;{\left(\frac{I_{\mathrm{peak}}}{\mathrm{\&Delta;t}}\right)}_{\mathrm{set}\&CenterDot;2}^I=K_{\mathrm{rel}}^{\mathrm{II}}\&times;K_{\mathrm{rel}}^I\&times;\left(\frac{I_{k\&CenterDot;\mathrm{peak}\&CenterDot;\mathrm{end}\&CenterDot;2}}{{\mathrm{\&Delta;t}}_{k\&CenterDot;\mathrm{peak}\&CenterDot;\mathrm{end}\&CenterDot;2}}\right),$ $t_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=t_2^I+\mathrm{\&Delta;t},$ $U_{\mathrm{set}\&CenterDot;1}^{\mathrm{II}}=K_{u\&CenterDot;\mathrm{rel}}^{\mathrm{II}}\&times;U_N,$ Wherein for the transient current protection seting value of downstream line; for safety factor, get 1.1-1.2; U _nfor system cloud gray model rated voltage; for safety factor, get 0.5-0.6; for circuit breaker intrinsic operate time; Δ t is breaker actuation time delay, gets 0.1-0.3s.