CN103123389A - Method for verifying polarity of zero-sequence current transformer - Google Patents

Abstract

The invention discloses a method for verifying a polarity of a zero-sequence current transformer. A hardware part comprises a signal acquisition system; a software part comprises a waveform analysis system; and the method comprises the following steps of: capturing an instant single-phase earth fault signal which mainly includes a bus zero-sequence voltage and a zero-sequence current of each line through the signal acquisition system by utilizing the characteristic of frequent instant single-phase earth fault of a distribution network system; and identifying whether a polarity connecting wire of the zero-sequence current transformer of each line is correct through the waveform analysis system based on the maximum zero-sequence amplitude value of a fault line and the characteristic that the phase position is opposite to that of the zero-sequence current of a non-fault line. The method for verifying the polarity of the zero-sequence current transformer solves the polarity verification difficulty of the zero-sequence current transformer in a small-current grounding line selection system efficiently without adding any device or tool, is very time-saving, convenient and fast, and solves a big difficulty in the practical application of small-current products.

Description

A kind of method of verification zero sequence current mutual inductor polarity

Technical field

The present invention relates to the equipment manufacturing technology field of electric system low-voltage network, relate in particular to a kind of method of verification zero sequence current mutual inductor polarity.

Background technology

China 35kV and following low-voltage network mostly adopt the neutral non-effective grounding mode, this class electric network single-phase earth fault incidence is very high, account for more than 70% of electric system total failare rate, occur to select as early as possible faulty line and get rid of after singlephase earth fault, to guarantee operation power and device security.

The Small Electric Current Earthing And Routing Device that is used for single-phase earth fault line selection of China's research and development at present is a lot, but overall route selection accuracy is less than 70%, be difficult to meet consumers' demand, one of them major reason is that zero sequence current mutual inductor (being called for short zero sequence CT) the secondary circuit polarity wiring error of access line selection apparatus causes.

In Practical Project, line selection apparatus installs, and before putting into operation, must check zero sequence CT polarity, and this is the prerequisite of the correct route selection of assurance device.The verification of zero sequence CT polarity belongs to a difficult problem in industry at present, and method commonly used is under transformer station's power down mode, utilizes current lifting device or relay-protection tester output current to pass each zero sequence CT, and the phase place that shows according to device judges polarity.Due in Practical Project, zero sequence CT reaches tens even dozens ofs, and between mutual inductor, does not wait to tens meters at several meters, interval, at every turn can only verification one or several, therefore this method efficient is very low, expends plenty of time and manpower and materials, and some transformer station does not allow to have a power failure, can't carry out the polarity verification, in charged situation, all personnel need to maintain a certain distance with charging equipment because the safe operation of power system rules are defined at all.

Therefore, the verification of zero sequence CT polarity is very urgent need to solve the problem of present industry.

Summary of the invention

A kind of method that the purpose of this invention is to provide verification zero sequence current mutual inductor polarity, it can efficiently solve a zero sequence current mutual inductor polarity verification difficult problem in Little Current Ground Connection System with software mode, and do not need to increase any equipment or instrument, save time very much convenient and swift, for little current product practical application has solved a great problem.

Theoretical research shows: during system generation singlephase earth fault, faulty line transient zero-sequence current amplitude is maximum, and anti-phase with the non-fault line zero-sequence current; And a large amount of on-the-spot service data statistics show, in singlephase earth fault, transient fault accounts for more than 90%.According to this 2 point, a kind of method that verification zero sequence current mutual inductor polarity is provided of the present invention, it is according to the electrical network transient single-phase earth fault process that captures, utilize wave form analysis software waveform is checked and analyzed, maximum according to faulty line zero-sequence current amplitude, and with the anti-phase characteristics of non-fault line zero-sequence current, judge zero sequence current mutual inductor polarity, solve simply and effectively zero sequence current mutual inductor polarity and detect difficult problem.

The present invention is achieved through the following technical solutions above-mentioned purpose: a kind of method of verification zero sequence current mutual inductor polarity is provided, and hardware components comprises signal acquiring system, and software section comprises waveform parsing system; Described signal acquiring system is used for catching residual voltage and the zero sequence current signal of electrical network transient single-phase earth fault, comprises voltage current transducer, filter circuit, AD converter and CPU processor; Waveform parsing system is installed on computing machine, can read recorder data from signal acquiring system, and check and analyze the fault-signal that captures, maximum according to faulty line zero sequence amplitude, and the characteristics that phase place and non-fault line zero-sequence current are anti-phase, whether the polarity wiring of identifying each circuit zero sequence current mutual inductor is correct.

Utilize the present invention can develop separately a kind of special zero sequence CT polarity calibration equipment, also can be integrated in existing common Small Electric Current Earthing And Routing Device.

After reading by reference to the accompanying drawings the detailed description of embodiment of the present invention, the features and advantages of the invention will be more readily apparent from.

Description of drawings

Fig. 1 is signal acquiring system processing flow chart of the present invention;

Fig. 2 is waveform parsing system fault oscillograph of the present invention.

Embodiment

Below in conjunction with accompanying drawing and example, technical scheme of the present invention is described further.

Signal acquiring system processing flow chart shown in Figure 1 comprises the following steps:

In step 101, read bus residual voltage and each circuit zero sequence current sampling data from modulus converter A/D, and be placed in the buffer memory RAM of appointment;

In step 102, according to the residual voltage last samples value calculating voltage Sudden Changing Rate that collects, computing method are as follows:

ΔU＝U(k)-2U(k-N)+U(k-2N) (1)

In formula (1), Δ U represents the value that suddenlys change, U (k) expression residual voltage last samples value, and the sampled value of U (k-N) expression one all wavefront, the sampled value of U (k-2N) expression two all wavefront, N represents every cycle sampled point sample.Can more clearly find out referring to Fig. 2, when electrical network generation singlephase earth fault, because residual voltage can become suddenly large, therefore the up-to-date sampled point U (k) that collects can become suddenly large, and sampled value U (k-N) and U (k-2N) before fault are basic identical, and Δ U can represent the fault situation of change;

In step 103, judge whether Sudden Changing Rate satisfies condition, and the Sudden Changing Rate threshold is set to 2V;

In step 104～106, the number of times that satisfies the Sudden Changing Rate condition is counted, only have when surpassing 3 times continuously and just think reliably to have started;

In step 107, carry out the 20ms time-delay, guarantee that the fault data window satisfies a cycle, for starting, amplitude prepares;

In step 108, calculate and judge whether the residual voltage amplitude satisfies the amplitude entry condition, generally, after electrical network generation singlephase earth fault, residual voltage all can surpass 30V, therefore starts threshold with 30V as amplitude;

In step 109, start and the amplitude entry condition owing to satisfying Sudden Changing Rate, therefore singlephase earth fault has occured in judgement, and the fault initiating element is effective.

In step 110, start the failure wave-recording program, the record trouble process;

After completing said process, utilize waveform parsing system to open recorder data, carry out waveform and check and analyze.

Waveform parsing system shown in Figure 2 following feature arranged::

U0 represents bus residual voltage waveform, and 1#～5# represents the zero-sequence current of 5 circuits;

Can find out from U0, when electrical network generation singlephase earth fault, residual voltage U0 can become suddenly large, and obvious sudden change relation is arranged before and after fault;

Contrast 1#～5# circuit zero-sequence current can be found out: the zero-sequence current waveform of 1# circuit and 5# circuit fault zero hour all up, phase relation is identical; 2# circuit, 3# circuit are identical with the zero-sequence current phase relation of 4# circuit; 2# circuit, 3# circuit are opposite with the zero-sequence current waveform of this three-line of 4# circuit and 1# circuit and this two other circuit of 5# circuit, single spin-echo.In the single-phase earthing situation, only have a circuit opposite with other circuit zero sequence current phase, there is zero-sequence current polarity wrong phenomenon in 5 circuits of this explanation;

Comparative analysis can be found out, 5# line zero-sequence current amplitude maximum, and peak value reaches 1.81A, can be judged as ground path; According to the zero-sequence current phase place of non-fault line and the principle of faulty line zero-sequence current single spin-echo, can judge: the reverse polarity connection of 1# passage.

Concrete implementation step is as follows:

Step 1 is opened the recorded wave file of record, and watches each passage waveform;

Step 2, amplitude relatively finds the passage of amplitude maximum, determines that it is faulty line institute respective channel;

Step 3 finds the passage identical with the channel phases of amplitude maximum, is zero-sequence current reverse polarity connection circuit.

Although more than described the specific embodiment of the present invention, should be appreciated that in actual applications and can make numerous variations and modification to these embodiments in the art those of skill in the art, and do not deviate from principle of the present invention and essence.

Claims (3)

1. the method for a verification zero sequence current mutual inductor polarity, it is characterized in that: hardware components comprises signal acquiring system, software section comprises waveform parsing system, and described signal acquiring system is used for catching residual voltage and the zero sequence current signal of electrical network transient single-phase earth fault; Waveform parsing system is used for checking and analyzing the fault-signal that captures, and is maximum according to faulty line zero sequence amplitude, and phase place and the anti-phase characteristics of non-fault line zero-sequence current, and whether the polarity wiring of identifying each circuit zero sequence current mutual inductor is correct.

2. the method for verification zero sequence current mutual inductor polarity according to claim 1 is characterized in that signal acquiring system has following implementation step:

Step 101 reads bus residual voltage and each circuit zero sequence current sampling data, and is placed in the buffer memory RAM of appointment from modulus converter A/D;

Step 102, according to the residual voltage last samples value calculating voltage Sudden Changing Rate that collects, computing method are as follows:

ΔU＝U(k)-2U(k-N)+U(k-2N) (1)

In formula (1), Δ U represents the value that suddenlys change, U (k) expression residual voltage last samples value, the sampled value of U (k-N) expression one all wavefront, the sampled value of U (k-2N) expression two all wavefront, N represents every cycle sampled point sample, when electrical network generation singlephase earth fault, because residual voltage can become suddenly large, therefore the up-to-date sampled point U (k) that collects can become suddenly large, and sampled value U (k-N) and U (k-2N) before fault are basic identical, and Δ U can represent the fault situation of change;

Step 103 judges whether Sudden Changing Rate satisfies condition, and the Sudden Changing Rate threshold is set to 2V;

Count the number of times that satisfies the Sudden Changing Rate condition step 104～106, only has when surpassing 3 times continuously and just think reliably to have started;

Step 107 is carried out the 20ms time-delay, guarantees that the fault data window satisfies a cycle, prepares for amplitude starts;

Step 108 is calculated and judges whether the residual voltage amplitude satisfies the amplitude entry condition, and generally, after electrical network generation singlephase earth fault, residual voltage all can surpass 30V, therefore starts threshold with 30V as amplitude;

Step 109 starts and the amplitude entry condition owing to satisfying Sudden Changing Rate, and therefore singlephase earth fault has occured in judgement, and the fault initiating element is effective.

Step 110 starts the failure wave-recording program, the record trouble process, and data acquisition finishes.

3. the method for verification zero sequence current mutual inductor polarity according to claim 1 is characterized in that waveform parsing system has following implementation step:

Step 1 is opened the recorded wave file of record, and watches each passage waveform;

Step 2, amplitude relatively finds the passage of amplitude maximum, determines that it is faulty line institute respective channel;

Step 3 finds the passage identical with the channel phases of amplitude maximum, is the reverse polarity connection circuit.

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