CN104993455A - Traction transformer over current protection method - Google Patents

Abstract

The invention discloses a traction transformer over current protection method. The method comprises steps: 1) a state of a main circuit breaker connected with a power supply of a target traction transformer is detected and controlled in real time, and when the main circuit breaker is detected to be in a closing state, the second step is carried out; 2) primary current signals of the target traction transformer are acquired, pre-judgment is carried out on the over current state of the target traction transformer according to the value of the acquired primary current signals, and if an over current state is pre-judged, the third step is carried out; and 3) according to similarities of the primary current signals in a former half current period and a latter half current period, the type of the over current state is judged, an over current protection action is not triggered if a magnetizing inrush current generation state is judged, and if a fault over current state is judged, the main circuit breaker is broken, and over current protection is executed. Over current protection misoperation caused by magnetizing inrush current can be avoided, and the method has the advantages of simple realization method, low needed cost, and high over current protection accuracy.

Description

A kind of traction transformer over-current protection method

Technical field

The present invention relates to alternating current electric locomotive power supply protection technical field, particularly relate to a kind of traction transformer over-current protection method.

Background technology

In the locomotive of Alternating Current Power Supply; need use traction transformer high pressure is converted to trailer system can low pressure; cause damage to transformer to prevent the abnormal conditions such as power transformer interior fault or short circuit; trailer system can design corresponding defencive function usually, and traction transformer overcurrent protection is exactly a wherein the most basic function.

At present for the overcurrent protection of traction transformer normally by Operation system setting setting value, when the primary current of traction transformer is greater than set point, trigger overcurrent protection fault thus disjunction high-speed circuit breaker is protected.As shown in Figure 1, in locomotive, AC25KV/50Hz single-phase alternating current accesses the former limit winding of traction transformer through high-speed circuit breaker HSCB, the various AC load of the secondary limit winding switching (such as current transformer) of traction transformer; In order to effectively protect implementing during traction transformer faults; primary current signal is delivered to TCU (Traction Control Unit through high-voltage mutual inductor TA; motion control unit) in; namely primary current sampled value is detected in real time by motion control unit TCU; a fixing current threshold is set in TCU; when primary current is greater than setting threshold values, trigger overcurrent protection, disjunction high-speed circuit breaker HSCB.

When high-speed circuit breaker combined floodgate, traction transformer zero load drop into; the primary current of traction transformer there will be magnetizing inrush current; more than 8 times of rated current can be reached when it is maximum; no-load transformer all will inevitably produce magnetizing inrush current when dropping into; the size of just shoving is relevant to the remanent magnetism etc. of electric network voltage phase angle and traction transformer when closing a floodgate; and this magnetizing inrush current can be decayed gradually, can not cause large infringement to traction transformer, be do not need to carry out protection act.Thus traction transformer adopts above-mentioned over-current protection method; be easy to by magnetizing inrush current false triggering overcurrent protection action; causing locomotive to drop into unsuccessfully when closing a floodgate, being particularly very easy to cause heavy loading locomotive machine to break at undue phase time, therefore normally can using locomotive and affect greatly.

Summary of the invention

The technical problem to be solved in the present invention is just: the technical problem existed for prior art; the invention provides a kind of overcurrent misoperation that magnetizing inrush current can be avoided to cause, and the traction transformer over-current protection method that simple, the required cost of implementation method is low and overcurrent protection accuracy is high.

For solving the problems of the technologies described above, the technical scheme that the present invention proposes is:

A kind of traction transformer over-current protection method, step comprises:

1) state of the main circuit breaker of real-time measure and control access Target Towing transformer frequency response, and when detecting that described main circuit breaker is in "on" position, proceeding to and performing step 2);

2) gather the primary current signal of Target Towing transformer, and judge in advance according to the over-current state of value to Target Towing transformer of the described primary current signal collected, if be judged as over-current state in advance, proceed to and perform step 3);

3) according to the similitude in described primary current signal current cycle between the forward and backward half period, judge the type of described over-current state, produce magnetizing inrush current state, the not overcurrent protection action of trigger target traction transformer if be judged to be; If be judged to be fault over-current state, then disconnect described main circuit breaker, overcurrent protection is performed to Target Towing current transformer.

Concrete steps as a further improvement on the present invention: described step 2) are:

2.1), when main circuit breaker closes a floodgate, the primary current signal of a current cycle of Target Towing transformer is gathered;

2.2) judge whether the value of the described primary current signal collected is greater than default overcurrent threshold value, if so, judges that described primary current signal as over-current signal in advance, and judge that Target Towing transformer is over-current state in advance, proceed to and perform step 3).

Especially by rising edge in the feedback states waveform of detection main circuit breaker auxiliary contact transmission as a further improvement on the present invention: described step 1), detect that described main circuit breaker is in "on" position.

Judge that the concrete steps of the type of described over-current state are as a further improvement on the present invention: described step 3):

3.1) obtain the described primary current signal of the current cycle collected when described main circuit breaker closes a floodgate, and calculate the similarity in the described primary current signal got between the forward and backward half period;

3.2) judge the size of the similarity calculated, if be less than or equal to predetermined threshold value h, then judge that described primary current signal is as magnetizing inrush current, and Target Towing transformer is for producing magnetizing inrush current state; Otherwise be judged to be fault over-current signal, and Target Towing transformer is internal fault status.

As a further improvement on the present invention, described step 3.1) in specifically calculate similarity between the forward and backward half period according to the following formula;

$R=\frac{\underset{k=1}{\overset{N_s/2}{\Σ}}\[X_1\left(k\right)\·Y\left(k\right)\]}{{\{\underset{k=1}{\overset{N_s/2}{\Σ}}{\[X_1\left(k\right)\]}^2.\underset{k=1}{\overset{N_s/2}{\Σ}}{\[Y\left(k\right)\]}^2\}}^{\frac{1}{2}}}$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before described primary current signal, Y (k)=-X ₂(k), X ₂the normalized value of the k interim kth of a second half sampled value that () is described primary current signal.

As a further improvement on the present invention, the concrete obtaining step of described normalized value is:

3.11) according to the following formula described primary current signal is normalized;

$I_{pN}\left(k\right)=\frac{I_p\left(k\right)}{max\left(\right|I_{pmax}|,|I_{pmin}\left|\right)}$

Wherein, I _pa k kth sampled value that () is described primary current signal, I _pNthe normalized value of a k kth sampled value that () is described primary current signal, k=1,2 ..., N _s, | I _pmax| be maximum in the primary current signal of collection, | I _pmin| be minimum value in the primary current signal of collection, max is for getting maximum;

3.12) normalized value of described primary current signal forward and backward half period is acquired respectively by following formula;

$X_1\left(k\right)=I_{pN}\left(k\right),k=1,2,...,\frac{N_s}{2}$

$Y\left(k\right)=-I_{pN}(k+\frac{N_s}{2}),k=1,2,...,\frac{N_s}{2}$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before described primary current signal, the normalized value of the interim kth of the second half sampled value that Y (k) is described primary current signal.

Compared with prior art, the invention has the advantages that:

1) primary current signal when the present invention closes a floodgate by detecting main circuit breaker judges the over-current state of Target Towing transformer, after being judged as over-current state in advance according to the value of primary current signal, magnetizing inrush current is identified again according to the similitude in primary current signal current cycle between the forward and backward half period, thus judge the type of over-current state, effectively can realize the overcurrent protection of traction transformer, avoid the error protection action because magnetizing inrush current causes simultaneously;

2) the present invention is in conjunction with the difference of magnetizing inrush current and fault-current signal wave character, by to the similitude in primary current signal current cycle between the forward and backward half period, what judge Target Towing transformer crosses stream type, can identify over-current signal is accurately due to magnetizing inrush current or traction transformer internal fault produces, thus effectively avoids because magnetizing inrush current signal causes judging by accident and trigger protection action;

3) the present invention carries out over-current state judgement by the primary current signal in collection current cycle; the identification of magnetizing inrush current can be realized in conjunction with the characteristic that magnetizing inrush current generation time is short, the real-time that traction transformer internal fault is protected can be guaranteed simultaneously.

Accompanying drawing explanation

Fig. 1 is the principle schematic of traction transformer former limit overcurrent protection in traditional locomotive.

Fig. 2 is the realization flow schematic diagram of the present embodiment traction transformer over-current protection method.

Fig. 3 is the waveform schematic diagram of typical magnetizing inrush current.

Fig. 4 is the waveform schematic diagram of typical fault current signal.

Fig. 5 is the realization flow schematic diagram of traction transformer over-current protection method in the specific embodiment of the invention.

Embodiment

Below in conjunction with Figure of description and concrete preferred embodiment, the invention will be further described, but protection range not thereby limiting the invention.

As shown in Figure 2, the present embodiment traction transformer over-current protection method, step comprises:

1) state of the main circuit breaker of real-time measure and control access Target Towing transformer frequency response, and when detecting that main circuit breaker is in "on" position, proceeding to and performing step 2);

2) gather the primary current signal of Target Towing transformer, and judge in advance according to the over-current state of value to Target Towing transformer of the primary current signal collected, if be judged as over-current state in advance, proceed to and perform step 3);

3) according to the similitude in primary current signal current cycle between the forward and backward half period, judge the type of over-current state, produce magnetizing inrush current state, the not overcurrent protection action of trigger target traction transformer if be judged to be; If be judged to be fault over-current state, then disconnect described main circuit breaker, overcurrent protection is performed to Target Towing current transformer.

Primary current signal when the present embodiment closes a floodgate by detecting main circuit breaker judges the over-current state of Target Towing transformer; after being judged as over-current state in advance according to the value of primary current signal; the type of over-current state is judged again according to primary current signal; the overcurrent protection action of not trigger target traction transformer when being judged to be magnetizing inrush current state, thus effectively can avoid the error protection action because magnetizing inrush current causes.

Time breaking down in typical magnetizing inrush current waveform and traction transformer inside, the fault-current signal of generation is as shown in Figure 3,4, from figure, time breaking down in traction transformer inside, and the waveform similarity of fault-current signal and standard sine wave; Magnetizing inrush current is then similar with the waveform of standard sine wave in section sometime, and larger in the shape differences of interval angle part and standard sine wave.The present embodiment is based on Waveform Correlation principle; in conjunction with the difference of above-mentioned magnetizing inrush current and fault-current signal wave character; by to the similitude in primary current signal current cycle between the forward and backward half period; what judge Target Towing transformer crosses stream type; can identify over-current signal is accurately due to magnetizing inrush current or traction transformer internal fault produces, thus effectively avoids because magnetizing inrush current signal causes judging by accident and trigger protection action.

In the present embodiment, step 1) in especially by detecting rising edge in feedback states waveform that main circuit breaker auxiliary contact sends, detect that main circuit breaker is in "on" position.

In the present embodiment, step 2) concrete steps be:

2.1), when main circuit breaker closes a floodgate, Target Towing transformer moment primary current signal is at that time gathered;

2.2) judge whether the value of the primary current signal collected is greater than default overcurrent threshold value, if so, judges that primary current signal is as over-current signal in advance, and judges that Target Towing transformer is over-current state in advance, proceed to and perform step 3).

The present embodiment is when main circuit breaker closes a floodgate, and first carrying out overcurrent judgement by the primary current signal of TCU collection Target Towing transformer, is 50Hz because frequency of supply in the traction transformer of alternating current electric locomotive is constant, if the TCU sampling period is f _s, then sampling number in every each current cycle n _sfor sampling number.When detecting that main disconnected device state closes rising edge, one-period (N after the main disconnected state of collection is closed _sindividual sampled point) the data of primary current signal, primary current signal is:

I _p＝{I _p(k)},k＝1,2,…,N _s(1)

Wherein I _pa k kth sampled value that () is primary current signal.

After TCU collects primary current signal, more whether be over-current signal according to the overcurrent threshold decision pre-set, to judge in advance current traction transformer over-current state.

TCU judges that Target Towing transformer is after over-current state in advance; according to the similitude identification over-current state type of primary current signal forward and backward half period; to identify because magnetizing inrush current or traction transformer internal fault cause former limit overcurrent, thus determine whether to need to perform traction transformer overcurrent protection.

In the present embodiment, step 3) in judge that the concrete steps of the type of over-current state are:

3.1) obtain the primary current signal of the current cycle collected when main circuit breaker closes a floodgate, and calculate the similarity of primary current signal in a current cycle between the forward and backward half period;

3.2) judge the size of the similarity calculated, if be less than or equal to predetermined threshold value h, then judge that primary current signal is as magnetizing inrush current, and Target Towing transformer is for producing magnetizing inrush current state; Otherwise be judged to be fault over-current signal, and Target Towing transformer is internal fault status.

The time produced due to magnetizing inrush current is short; thus the primary current signal that the present embodiment is gathered in the rear current cycle (the present embodiment gets 20ms) of main circuit breaker combined floodgate by TCU carries out judgement identification; effective identification of magnetizing inrush current can be realized, guarantee the real-time that traction transformer internal fault is protected simultaneously.

The present embodiment utilizes magnetizing inrush current signal signal characteristic when front half period, later half cycle inconsistent, and the fault-current signal characteristic that signal characteristic is consistent when front half period, later half cycle, identify the type of over-current signal, thus identify the type of over-current state, with when being judged to be fault over-current signal, perform overcurrent protection; And when being judged to be magnetizing inrush current state, the not overcurrent protection action of trigger target traction transformer, avoids the error protection action because magnetizing inrush current causes.

In the present embodiment, step 3.1) in concrete (2) according to the following formula calculate the similarity between the forward and backward half period;

$R=\frac{\underset{k=1}{\overset{N_s/2}{\Σ}}\[X_1\left(k\right)\·Y\left(k\right)\]}{{\{\underset{k=1}{\overset{N_s/2}{\Σ}}{\[X_1\left(k\right)\]}^2.\underset{k=1}{\overset{N_s/2}{\Σ}}{\[Y\left(k\right)\]}^2\}}^{\frac{1}{2}}}---\left(2\right)$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before the signal of former limit, namely

$X_1\left(k\right)=I_{pN}\left(k\right),k=1,2,...,\frac{N_s}{2},k=1,2,...,\frac{N_s}{2},$ N _sfor sampling number, I _pNk () is the normalized value of a kth sampled value in primary current signal; Y (k)=-X ₂(k), X ₂the normalized value of the k interim kth of a second half sampled value that () is former limit signal, namely $Y\left(k\right)=-I_{pN}(k+\frac{N_s}{2}),k=1,2,...,\frac{N_s}{2}.$

In the present embodiment, the concrete obtaining step of normalized value is:

3.11) according to the following formula (3) are normalized primary current signal;

$I_{pN}\left(k\right)=\frac{I_p\left(k\right)}{max\left(\right|I_{pmax}|,|I_{pmin}\left|\right)}---\left(3\right)$

Wherein, I _pa k kth sampled value that () is described primary current signal, I _pNthe normalized value of a k kth sampled value that () is described primary current signal, k=1,2 ..., N _s, | I _pmax| be maximum in the primary current signal of collection, | I _pmin| be minimum value in the primary current signal of collection, max is for getting maximum;

3.12) normalized value of described primary current signal forward and backward half period is acquired respectively by following formula (4), (5);

$X_1\left(k\right)=I_{pN}\left(k\right),k=1,2,...,\frac{N_s}{2}---\left(4\right)$

$Y\left(k\right)=-I_{pN}(k+\frac{N_s}{2}),k=1,2,...,\frac{N_s}{2}---\left(5\right)$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before primary current signal, the normalized value of the interim kth of the second half sampled value that Y (k) is primary current signal.

The present embodiment identifies magnetizing inrush current signal by the similarity in half period and later half cycle before primary current signal, can similitude between Efficient Characterization signal, and RM is simple and accuracy of identification is high simultaneously.

In the specific embodiment of the invention, the step of above-mentioned traction transformer over-current protection method is as shown in Figure 5:

In the Initialize installation rising edge cycle, sign of flag=FALSE (is labeled as non-increasing along in the cycle by FALSE, TRUE is in the rising edge cycle), current cycle array of data Ip [Ns]=[0,0,0], N=0 and former limit overcurrent anticipation mark Ip_OIr=FALSE (be labeled as non-over-current state by FALSE, TRUE is labeled as over-current state); Former limit overcurrent mark Ip_OI=FALSE (be labeled as non-over-current state by FALSE, TRUE is labeled as over-current state);

Judge main disconnected "on" position, if during for closing a floodgate, gathering moment primary current signal Ip (k) at that time, judging whether Ip (k) is greater than overcurrent threshold value Ith, if it is put former limit overcurrent anticipation mark Ip_OIr=TRUE, be namely judged as over-current state in advance;

When being judged as over-current state in advance, whether detect main disconnected closing is in the rising edge cycle, and when putting sign of flag=TRUE in the rising edge cycle for during main disconnected closed rising edge, and when determining sign of flag=TRUE in the rising edge cycle, gather the primary current signal of Ns (one-period), the similarity R in primary current signal Ip (k) front half period and later half cycle is calculated according to formula (2), judge whether similarity R is greater than predetermined threshold value h, if it is Ip_OI=Ip_OIr is put, namely fault former limit overcurrent is finally judged to be, traction transformer is in fault over-current state, control main circuit breaker by TCU to disconnect, perform traction transformer overcurrent protection action, otherwise be non-faulting former limit overcurrent, traction transformer is for producing magnetizing inrush current state, do not perform overcurrent protection,

Sign of flag=FALSE, current cycle array of data Ip [Ns] in the replacement rising edge cycle=[0,0 ..., 0], after main disconnected closed periodicity N=0, circulation performs above-mentioned steps and carries out overcurrent protection next time.

Above-mentioned just preferred embodiment of the present invention, not does any pro forma restriction to the present invention.Although the present invention discloses as above with preferred embodiment, but and be not used to limit the present invention.Therefore, every content not departing from technical solution of the present invention, according to the technology of the present invention essence to any simple modification made for any of the above embodiments, equivalent variations and modification, all should drop in the scope of technical solution of the present invention protection.

Claims (6)

1. a traction transformer over-current protection method, is characterized in that, step comprises:

1) state of the main circuit breaker of real-time measure and control access Target Towing transformer frequency response, and when detecting that described main circuit breaker is in "on" position, proceeding to and performing step 2);

2) gather the primary current signal of Target Towing transformer, and judge in advance according to the over-current state of value to Target Towing transformer of the described primary current signal collected, if be judged as over-current state in advance, proceed to and perform step 3);

3) according to the similitude in described primary current signal current cycle between the forward and backward half period, judge the type of described over-current state, produce magnetizing inrush current state, the not overcurrent protection action of trigger target traction transformer if be judged to be; If be judged to be fault over-current state, then disconnect described main circuit breaker, overcurrent protection is performed to Target Towing current transformer.

2. traction transformer over-current protection method according to claim 1, is characterized in that: described step 2) concrete steps be:

2.1), when main circuit breaker closes a floodgate, the current time primary current signal of Target Towing transformer is gathered;

2.2) judge whether the value of the described primary current signal collected is greater than default overcurrent threshold value, if so, judges that described primary current signal as over-current signal in advance, and judge that Target Towing transformer is over-current state in advance, proceed to and perform step 3).

3. traction transformer over-current protection method according to claim 2, is characterized in that: described step 1) in especially by detecting rising edge in feedback states waveform that main circuit breaker auxiliary contact sends, detect that described main circuit breaker is in "on" position.

4. the traction transformer over-current protection method according to claim 1 or 2 or 3, is characterized in that, described step 3) in judge that the concrete steps of the type of described over-current state are:

3.1) obtain the described primary current signal of the current cycle collected when described main circuit breaker closes a floodgate, and calculate the similarity in the described primary current signal got between the forward and backward half period;

3.2) judge the size of the similarity calculated, if be less than or equal to predetermined threshold value h, then judge that described primary current signal is as magnetizing inrush current, and Target Towing transformer is for producing magnetizing inrush current state; Otherwise be judged to be fault over-current signal, and Target Towing transformer is internal fault status.

5. traction transformer over-current protection method according to claim 4, is characterized in that, described step 3.1) in specifically calculate similarity between the forward and backward half period according to the following formula;

$R=\frac{\underset{k=1}{\overset{N_s/2}{\Σ}}\[X_1\left(k\right)\·Y\left(k\right)\]}{{\{\underset{k=1}{\overset{N_s/2}{\Σ}}{\[X_1\left(k\right)\]}^2.\underset{k=1}{\overset{N_s/2}{\Σ}}{\[Y\left(k\right)\]}^2\}}^{\frac{1}{2}}}$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before described primary current signal, Y (k)=-X ₂(k), X ₂the normalized value of the k interim kth of a second half sampled value that () is described primary current signal.

6. traction transformer over-current protection method according to claim 5, is characterized in that, the concrete obtaining step of described normalized value is:

3.11) according to the following formula described primary current signal is normalized;

$I_{pN}\left(k\right)=\frac{I_p\left(k\right)}{max\left(\right|I_{pmax}|,|I_{pmin}\left|\right)}$

Wherein, I _pa k kth sampled value that () is described primary current signal, I _pNthe normalized value of a k kth sampled value that () is described primary current signal, k=1,2 ..., N _s, | I _pmax| be maximum in the primary current signal of collection, | I _pmin| be minimum value in the primary current signal of collection, max is for getting maximum;

3.12) normalized value of described primary current signal forward and backward half period is acquired respectively by following formula;

$X_1\left(k\right)=I_{pN}\left(k\right),k=1,2,...,\frac{N_s}{2}$

$Y\left(k\right)=-I_{pN}(k+\frac{N_s}{2}),k=1,2,...,\frac{N_s}{2}$

Wherein, X ₁k () is the normalized value of a kth sampled value in the half period before described primary current signal, the normalized value of the interim kth of the second half sampled value that Y (k) is described primary current signal.