CN103513115B - A kind of factory distribution cable charging capacitor on-line measurement device and method - Google Patents

Abstract

The present invention relates to the on-line measurement device and method of a kind of cable charging capacitor, this device includes voltage signal processing circuit, current signal processes circuit, advance signal modulate circuit, data collecting card, processing unit module, voltage signal processing circuit and current signal process circuit and are connected with advance signal modulate circuit respectively, advance signal modulate circuit, data collecting card, processing unit module is sequentially connected with, it is simple that the present invention has wiring, precision is high, the features such as temporal resolution height and high reliability, and the inventive method finally measurement to factory's distribution cable charging capacitor only need to utilize capacitor capacitive reactive power computing formula and reactive power conserva-tion principle, algorithm is simple.

Description

A kind of factory distribution cable charging capacitor on-line measurement device and method

Technical field

The present invention relates to On-line Measuring Method method and the device thereof of a kind of factory distribution cable charging capacitor, belong to electric The technical field measured.

Background technology

Along with going from strength to strength of plant power supply and distribution net system scale, in network, cable run proportion increases, circuit pair Ground electric capacity is non-negligible on the impact of power distribution network.On the one hand, charging capacitor may be sent out with system impedance at certain specific subharmonic Raw series parallel resonance, causes the harmonic wave of system to become big, on the other hand, after there is singlephase earth fault, and the existence of charging capacitor Earth fault can be made to flow through capacitance current, and when earthing capacitance current is bigger and when exceeding certain value, ground arc can not be certainly Horizontal blanking, will result in arc grounding, produces overvoltage.The charging capacitor of plant power supply and distribution system is carried out on-line measurement, permissible For rationally selecting series parallel resonance solution and single phase earthing protection measure to provide underlying parameter.

When the charging capacitor size calculated according to the given specific capacitance of cable manufacturer and real system run The size of charging capacitor is different, therefore needs to test the size of plant power supply and distribution system charging capacitor, the most not See the On-line Measuring Method having wiring is simple, precision is high, reliability is high, temporal resolution is high factory's distribution cable charging capacitor With device.

Summary of the invention

For the shortcomings and deficiencies overcoming prior art to exist, the present invention proposes a kind of factory distribution cable innovatively The On-line Measuring Method method of charging capacitor and device thereof, application this method can realize actual factory distribution cable charged electrical The carrying out held is measured fast and accurately, and provides data to prop up for reasonable selective resonance solution and one-phase ground protection measure Support.

The on-line measurement device of a kind of cable charging capacitor, this device includes at voltage signal processing circuit, current signal Reason circuit, advance signal modulate circuit, data collecting card, processing unit module, at voltage signal processing circuit and current signal The output signal of reason circuit inputs advance signal modulate circuit respectively, and the output signal of advance signal modulate circuit accesses data acquisition Truck, the output signal of data collecting card accesses processing unit module.

Described advance signal modulate circuit includes the converter unit of voltage and current signal, forceful electric power and light current light-coupled isolation list Unit and anti-aliasing filter unit, the output signal input anti-aliasing filter unit of forceful electric power and light current light-coupled isolation unit, anti-aliasing The output signal of filter unit accesses voltage and current signal converter unit.

Described data collecting card is PCMCIA data collecting card, and PCMCIA is Personal Computer Memory The abbreviation of Card International Association Industry Standard Architecture, power system Frequency be 50Hz, the cycle is 0.02s, and periodic sampling 256 point, the sampling period is 78.125 microseconds, and sample frequency is just 12.8k/s, and the sample rate of capture card is higher than sample frequency, both the sample rate of capture card should be greater than 12.8k/s, this Bright it is chosen as 200k/s.

Described processing unit module is the computer running and having DAP.

The method of testing of a kind of on-line measurement device, the steps include:

1) a road cable head end total input-wire and two-way cable end piece feeder line are connected at tested cable.

2) a road cable head end total input-wire and two-way cable end piece feeder line three-phase voltage and three-phase current signal are carried out with Pacing amount, completes the conversion of analog quantity and digital quantity by advance signal modulate circuit and high-speed figure capture card；

3) voltage signal and the current signal of standard are produced by standard signal source, to measurement apparatus hardware circuit and collection The non-synchronous sampling errors that card produces carries out synchronicity correction；

4) use fast discrete Fourier mapping algorithm, complete a road cable head end total input-wire and two-way cable end piece feeder line Three-phase voltage signal and 256 point Fourier conversion of current signal, obtain road cable head end total input-wire and a two-way cable end piece Feeder line three-phase voltage signal and the fundamental voltage amplitude of current signal and phase place；

5) a road cable head end total input-wire and the calculating of two-way cable end piece feeder current signal fundamental power are completed, respectively Calculate a road cable head end total input-wire and two-way cable end piece feeder current signal active power and reactive power；

6) choose the moment that the power supply buses power consumption of required detection charging capacitor size is little, utilize above-mentioned measurement apparatus complete Become cable head end total input-wire and the active power of two feeder lines of cable end piece and the measurement of reactive power；

7) utilization records cable head end total input-wire and the reactive power of two feeder lines of cable end piece of gained, passes through formula Q_Circuit=Q_{Total input-wire}-Q_Load, the charging calculating charging capacitor in the line charging capacitance size that cable head end is equivalent can be calculated Power, wherein Q_CircuitFor the charge power of circuit, Q_{Total input-wire}The reactive power recorded for total input-wire, Q_LoadFor total input-wire institute on-load Reactive power.

8) according to the power calculation expression formula of electric capacityCalculate the first-harmonic capacitive reactance of charging capacitor, draw cable two The line charging capacitance size of end equivalence, wherein U_aFor busbar voltage, X_cFor circuit capacitive reactance.

For a road cable head end total input-wire and two-way cable end piece feeder line three-phase voltage and the digital signal of three-phase current 256 point Fourier transformation calculations formula as follows:

$\left\{\begin{array}{c}U\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)(cos\frac{2\mathrm{\π}}{N}h-jsin\frac{2\mathrm{\π}}{N}h)\\ I\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)(\cos \frac{2\mathrm{\π}}{N}h-j\sin \frac{2\mathrm{\π}}{N}h)\end{array}\right.$

Being fundametal compoment during h=1, sliding time window width chooses 256 point sampling points all the time, and the frequency of power system is 50Hz, the cycle is 0.02s, periodic sampling 256 point, and can calculate the sampling period is 78.125 microseconds, and sample frequency is just 12.8k/s, and the sample rate of capture card is higher than sample frequency, both the sample rate of capture card should be greater than 12.8k/s, this Bright it is chosen as 200k/s.

By advance signal modulate circuit, the voltage and current signal of measurement through the light-coupled isolation of strong and weak electricity and dividing potential drop, And the analogue signal (U of the voltage x current of each test point shown in Fig. 3 is formed through anti-aliasing filter_a、U_b、U_c、U_a1、U_b1、U_c1、U_a2、 U_b2、U_c3、 )。

The described conversion completing analog quantity and digital quantity through high-speed figure capture card, sample rate is PCMCIA high-speed figure Capture card completes the data sampling of each signalling channel 256, obtains the digital signal of the voltage x current of each test point shown in Fig. 3 (U_a(n)、U_b(n)、U_c(n)、U_a1(n)、U_b1(n)、U_c1(n)、U_a2(n)、U_b2(n)、U_c2(n)、 )。

The invention has the beneficial effects as follows, compared with prior art, the present invention has that wiring is simple, precision is high, time resolution The high feature with high reliability of rate: (1) only arranges 3 measuring points can complete the measurement of factory's distribution cable charging capacitor.(2) originally Inventive method have employed high speed digital sample, and 12.8k/s sample rate ensures that the employing time interval of each channel sample point is 78.125 microseconds, the asynchronous sampling that simultaneously causes hardware circuit and capture card carries out numeral correction, and strict guarantee is to work The measurement temporal resolution of factory's distribution cable charging capacitor is high.(3) the inventive method uses FFT theoretical and frequency domain power calculates reason Opinion, to cable head end total input-wire and the active power of two feeder lines of cable end piece and the measurement of reactive power, power calculation window Mouth chooses 1 cycle, is spaced apart 10 milliseconds analysis time, ensures what factory's distribution cable charging capacitor was measured from computational methods High real-time, high accuracy and high reliability.(4) the inventive method finally measurement to factory's distribution cable charging capacitor only needs profit Electricity container capacitive reactive power computing formula and reactive power conserva-tion principle, algorithm is simple.

Accompanying drawing explanation

Fig. 1 is the hardware designs schematic diagram of measurement apparatus.

Fig. 2 is the advance signal modulate circuit of measurement apparatus.

Fig. 3 is factory's distribution cable charging capacitor on-line testing wiring schematic diagram.

Fig. 4 is the calculation flow chart of factory's distribution cable charging capacitor On-line Measuring Method.

Fig. 5 (a) is 35 kV Side of Main Transformer voltage and outlet current spectrum scattergram.

Fig. 5 (b) is 317 line 35kV and inlet wire current frequency spectrum profile.

Fig. 5 (c) is 318 line 35kV and inlet wire current frequency spectrum profile.

Detailed description of the invention

Below against accompanying drawing, by the description to embodiment, each component that the detailed description of the invention of the present invention is the most involved Shape, structure, mutual alignment between each several part and annexation, the effect of each several part and operation principle, manufacturing process and Operate with method etc., be described in further detail, to help those skilled in the art to the inventive concept of the present invention, technology Scheme has more complete, accurate and deep understanding.

As depicted in figs. 1 and 2, this measurement apparatus is by voltage signal processing circuit, current signal process, circuit voltage electric current Signal advance signal modulate circuit (forceful electric power and light current light-coupled isolation, anti-aliasing filter), data collecting card, processing unit module group Become and each unit is sequentially connected with.Data collecting card is PCMCIA data collecting card, and processing unit module is Operational Data Analysis The computer of program.

As shown in Figure 4, during the on-line measurement plant running of cable charging capacitor, the step of measuring method is:

(1) this measurement apparatus completes 3 road three-phase bus voltages and the synchro measure of 3 road three-phase current signals, by front Put signal conditioning circuit, and complete the conversion of analog quantity and digital quantity through 200K/s high-speed figure capture card；

(2) by producing voltage signal and the current signal of standard independent of the standard signal source of described device, to measurement The non-synchronous sampling errors that device hardware circuit and capture card produce carries out synchronicity correction, strict guarantee 18 road voltage and current The synchronized sampling of signal.The inventive method have employed high speed digital sample, and 12.8k/s sample rate ensures each channel sample point Using time interval is 78.125 microseconds, and the asynchronous sampling simultaneously caused hardware circuit and capture card carries out numeral correction, Strict guarantee is high to the measurement temporal resolution of factory distribution cable charging capacitor.

(3) use fast discrete Fourier mapping algorithm, complete 3 phase voltage signals received and 3 road current signals Fourier transform；

(4) calculating 3 road current signal fundamental powers, the power supply buses power consumption choosing required detection charging capacitor size is little Moment, utilize above-mentioned measurement apparatus to complete cable head end total input-wire and the active power of two feeder lines of cable end piece and idle The measurement of power；

(5) utilization records cable head end total input-wire and the reactive power of two feeder lines of cable end piece of gained, calculates Go out the charge power of charging capacitor, utilize the power calculation expression formula of electric capacity to calculate the first-harmonic capacitive reactance of charging capacitor, and then calculate Power supply-distribution system cable charging capacitor.

This measurement apparatus completes 3 road three-phase bus voltages and the synchro measure of 3 road three-phase current signals, by front confidence Number modulate circuit, by the voltage and current signal measured through the light-coupled isolation of strong and weak electricity and dividing potential drop, and through anti-aliasing filter Form the analogue signal (U of the voltage x current of each test point shown in Fig. 3_a、U_b、U_c、U_a1、U_b1、U_c1、U_a2、U_b2、U_c3、 )；It is 200K/s's by sample rate again PCMCIA high-speed figure capture card completes the data sampling of each signalling channel 256, obtains the voltage of each test point shown in Fig. 3 Digital signal (the U of electric current_a(n)、U_b(n)、U_c(n)、U_a1(n)、U_b1(n)、U_c1(n)、U_a2(n)、U_b2(n)、U_c2(n)、 ).Logical Crossing standard signal source and produce voltage signal and the current signal of standard, produce measurement apparatus hardware circuit and capture card is non-same The error of step sampling carries out synchronicity correction, strict guarantee 18 road voltage and current signal Domain Synchronous.

Apparatus of the present invention test point arranges the bus three-phase voltage u seeing accompanying drawing 3, respectively cable head end total input-wire₁(t)、 Cable head end total input-wire three-phase current i₁The bus three-phase voltage u of one feeder line of (t), cable end piece₂(t), cable end piece one feedback The three-phase current i of line₂The bus three-phase voltage u of (t), another feeder line of cable end piece₃(t) and another feeder line of cable end piece Three-phase current i₃(t)。

The computational methods of measurement apparatus of the present invention.

256 point Fourier transformation calculations formula of the digital signal of (1) 3 road three-phase voltage and 3 road three-phase currents are as follows:

$\left\{\begin{array}{c}U\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)(cos\frac{2\mathrm{\π}}{N}h-jsin\frac{2\mathrm{\π}}{N}h)\\ I\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)(\cos \frac{2\mathrm{\π}}{N}h-j\sin \frac{2\mathrm{\π}}{N}h)\end{array}\right.---\left(1\right)$

Being fundametal compoment during h=1, sliding time window width chooses 256 point sampling points all the time, and the counting period is each sampling Point sampling cycle 78.125 microsecond, can obtain 3 road three-phase voltage signals and the fundamental voltage amplitude of 3 road current signals and phase place.

(2) cable head end total input-wire and the active power of two feeder lines of cable end piece and the calculating of reactive power

Taking window width is the voltage of 1 cycle, current data, carry out fast Fourier analysis, draws voltage, electric current First-harmonic and each harmonic amplitude and phase angle, then calculate cable head end total input-wire and the wattful power of two feeder lines of cable end piece Rate and reactive power, as the result of one-shot measurement, then carry out a power calculation at interval of 10ms, and computing formula is shown in formula And formula (3) (2):

Active power calculation expression formula:

Reactive power calculation expression formula:

Wherein P is the total active power of three-phase, P_a,P_b,P_cBeing respectively the active power of A, B, C three-phase, Q is that three-phase is the most idle Power, Q_a,Q_b,Q_cIt is respectively the reactive power of A, B, C three-phase, U_a,U_b,U_cIt is respectively A, B, C three-phase voltage signal amplitude, I_a, I_b,I_cIt is respectively A, B, C three-phase current signal amplitude, θ_a,θ_b,θ_cIt is respectively A, B, C three-phase voltage signal phase place, β_a,β_b,β_cPoint Wei A, B, C three-phase current signal phase place.

(4) calculating of cable charging capacitor

When the power supply buses power consumption of required detection charging capacitor size is little, the capacitive reactive power of circuit is more than sense Property reactive power, ignores the lagging reactive power of circuit, now circuit be all capacitive reactive power Q_Circuit＜ 0, and load basic For inductive load, i.e. Q_Load＞ 0, simultaneously according to power supply-distribution system reactive power conserva-tion principle Q_{Total input-wire}=Q_Load+Q_CircuitElectricity can be calculated The charging reactive power of cable is Q_Circuit=Q_{Total input-wire}-Q_Load, Q_LoadFor the load reactive power sum of two feeder lines of cable end piece, then According to electric capacity capacitive reactive powerThe line charging capacitance size in cable head end equivalence can be calculated.

Fig. 5 (a), Fig. 5 (b), Fig. 5 (c) are factory's distribution T1 measuring point, T2 measuring point and the voltage and current waveform of T3 measuring point. 35 kV Side of Main Transformer reactive power is-0.229Mvar, and 317 line 35kV inlet wire reactive powers are 0.128Mvar, 318 line 35kV inlet wires Reactive power is 0.022Mvar, and the charge power of electric capacity is-0.229-0.128-0.022=-0.379Mvar, then charging capacitor First-harmonic capacitor value be

$X_c=\frac{{\left(\frac{(21.081+21.118+21.227)*\sqrt{3}}{3}\right)}^2}{|-0.379|}=3538.13\mathrm{\Ω}.$

Above in conjunction with accompanying drawing, the present invention is exemplarily described, it is clear that the present invention implements not by aforesaid way Restriction, as long as have employed the method design of the present invention and the improvement of various unsubstantialities that technical scheme is carried out, or without changing Enter and design and the technical scheme of the present invention are directly applied to other occasion, all within protection scope of the present invention.

Claims (2)

1. an On-line Measuring Method for factory's distribution cable charging capacitor, measurement apparatus includes voltage signal processing circuit, electricity Stream signal processing circuit, advance signal modulate circuit, data collecting card, processing unit module, voltage signal processing circuit and electricity The output signal of stream signal processing circuit inputs advance signal modulate circuit respectively, and the output signal of advance signal modulate circuit connects Entering data collecting card, the output signal of data collecting card accesses processing unit module；Described advance signal modulate circuit includes Forceful electric power and light current light-coupled isolation unit, anti-aliasing filter unit and voltage and current signal converter unit, forceful electric power and light current optocoupler every Output signal from unit inputs anti-aliasing filter unit, and the output signal of anti-aliasing filter unit accesses voltage and current signal and becomes Change unit；Described processing unit module is the computer running and having DAP, and its measuring process is:

Step 1, connect a road cable head end total input-wire and two-way cable end piece feeder line at tested cable；

Step 2, a road cable head end total input-wire and two-way cable end piece feeder line three-phase voltage and three-phase current signal are carried out with Pacing amount, completes the conversion of analog quantity and digital quantity by advance signal modulate circuit and high-speed figure capture card；

Step 3, produce the voltage signal of standard and current signal by standard signal source, to measurement apparatus hardware circuit and collection The non-synchronous sampling errors that card produces carries out synchronicity correction；

Step 4, utilization fast discrete Fourier mapping algorithm, complete a road cable head end total input-wire and two-way cable end piece feeder line Three-phase voltage signal and 256 point Fourier conversion of current signal, obtain road cable head end total input-wire and a two-way cable end piece Feeder line three-phase voltage signal and the fundamental voltage amplitude of current signal and phase place；

Step 5, complete a road cable head end total input-wire and the calculating of two-way cable end piece feeder current signal fundamental power, respectively Calculate a road cable head end total input-wire and two-way cable end piece feeder current signal active power and reactive power；

Step 6, choose the moment that the power supply buses power consumption of required detection charging capacitor size is little, utilize above-mentioned measurement apparatus complete Become cable head end total input-wire and the active power of two feeder lines of cable end piece and the measurement of reactive power；

Step 7, utilization record cable head end total input-wire and the reactive power of two feeder lines of cable end piece of gained, pass through formula Q_Circuit=Q_{Total input-wire}-Q_Load, the charging calculating charging capacitor in the line charging capacitance size that cable head end is equivalent can be calculated Power.

Step 8, power calculation expression formula according to electric capacity calculate the first-harmonic capacitive reactance of charging capacitorDraw the line charging capacitance size of cable two ends equivalence.

2. the measuring method of on-line measurement device as claimed in claim 1, it is characterised in that: cable head end total input-wire and electricity 256 point Fourier transformation calculations formula of the digital signal of two feeder line three-phase voltages of cable end and three-phase current are as follows:

$\left\{\begin{array}{c}U\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}u\left(n\right)(cos\frac{2\mathrm{\π}}{N}h-jsin\frac{2\mathrm{\π}}{N}h)\\ I\left(h\right)=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)e^{-j\frac{2\mathrm{\π}h}{N}}=\underset{n=0}{\overset{N-1}{\Σ}}i\left(n\right)(\cos \frac{2\mathrm{\π}}{N}h-j\sin \frac{2\mathrm{\π}}{N}h)\end{array}\right.$

Being fundametal compoment during h=1, sliding time window width chooses 256 point sampling points all the time, and the counting period is that each sampled point is adopted Sample cycle 78.125 microsecond.