CN1465986A

CN1465986A - A testing method for single-phase ground current in distribution network

Info

Publication number: CN1465986A
Application number: CNA021342946A
Authority: CN
Inventors: 姜新宇; 赵正军; 师冬霞; 陈锐; 黄灿辉; 张瑞红
Original assignee: Guangzhou Zhiguang Electric Co Ltd
Current assignee: Guangzhou Zhiguang Electric Co Ltd
Priority date: 2002-07-03
Filing date: 2002-07-03
Publication date: 2004-01-07
Anticipated expiration: 2022-07-03
Also published as: CN1216294C

Abstract

The invention relates to a single-phase ground current testing method of a distribution network, which is characterized in that at least two voltage signals of different frequencies are injected into the tested power grid system through a special test device, and the test voltages of the electric signals of different frequencies are measured respectively. The current and voltage values at the connection point between the signal output terminal of the device and the tested grid, according to the frequency of the injected electrical signal and the measured current and voltage values, use a specific relationship to calculate the ground capacitance and the ground capacitance of the tested grid capacitive current value. The feature of the present invention is that by injecting two or more than two voltage signals of different frequencies into the tested grid system, it can avoid the impact of the substation bus PT short-circuit impedance on the test results, thereby obtaining the ground capacitance or capacitive current of the tested grid , High precision, fast test speed, wide application, safe and reliable.

Description

A kind of method for testing single phase grounding current of electric power network

Affiliated technical field

The present invention relates to a kind of method for testing single phase grounding current of electric power network, be used to measure electric pressure network system electric capacity or system capacitive currents over the ground such as 1kV, 3kV, 6kV, 10kV, 35kV, 66kV, belong to AC network testing apparatus technical field.

Background technology

Domestic other capacitance current tester is to be undertaken by the signal that injects single test frequency to electrical network at present, mainly contain two kinds of methods: the first is passed through the signal that substation bus bar PT injects certain frequency, converts directly according to no-load voltage ratio then by the equiva lent impedance at measuring-signal decanting point place and calculates; It two is to utilize the frequency variation signal source, adds certain inductance in tester, calculates system's ground capacitance by seeking resonance frequency.The shortcoming of these methods is the influences that reckon without the short-circuit impedance of bus PT, measuring accuracy is reduced greatly, in fact because substation bus bar PT short-circuit impedance is bigger, therefore under most applicable cases, may not obtain correct test result according to the method described above, time error be arranged even be several times of actual value.

Technology contents

The technical issues that need to address of the present invention are to overcome that existing method of testing is subjected to the influence of bus PT short-circuit impedance big, the shortcoming of low precision, provide a kind of and can avoid the substation bus bar PT short-circuit impedance a kind of method for testing single phase grounding current of electric power network higher to influence, the precision of test result.

Technical matters of the present invention can solve by taking following measure: a kind of method for testing single phase grounding current of electric power network, be characterized in: the voltage signal that injects at least two different frequencies by the special test device to tested network system, measure the electric current and the magnitude of voltage of described proving installation signal output part and tested electrical network tie point when the different frequency electric signal respectively, according to the electric signal frequency of injecting and the described electric current of measuring, magnitude of voltage, calculate the ground capacitance and the capacitive earth current value of tested electrical network.

Technical matters of the present invention also can solve by taking following measure:

The special test device is formed by connecting by rectification circuit, inverter circuit, cpu logic control circuit, display circuit and working power as previously mentioned, output terminal, output terminal that the input end of inverter circuit connects rectification circuit connect substation bus bar PT, the input end of rectification circuit connects electric main, and the control signal output ends of cpu logic control circuit connects the control end of inverter circuit, the input end that signal output part connects display circuit, the output terminal that power end connects working power; Rectification circuit will become DC voltage through the interchange 50Hz voltage commutation after isolating, it is 1MBH60 that inverter circuit adopts electronic power switch IGBT device, its model, DC input voitage is reverse into the alternating voltage of changeable frequency, and the cpu logic control circuit produces control wave, finishes the calculating of capacitance current and send display circuit to show the result.

Rectification circuit adopts common full bridge rectifier, will become direct current through the interchange 50Hz voltage commutation after isolating, for inverter circuit provides direct supply; It is 1MBH60 that inverter circuit adopts electronic power switch IGBT device, its model, DC input voitage is reverse into the alternating voltage of changeable frequency, and the signal voltage/electric current that will produce changeable frequency injects electrical network, the gating pulse employing Sine Modulated pulse SPWM of IGBT electronic power switch; The cpu logic control circuit is made of 51 series monolithic 89C58 and peripheral logical circuit commonly used, finish and produce control signal voltage, finish the calculating of capacitance current and show liquor charging is brilliant as a result, the SPWM pulse that CPU regularly produces removes to drive driving element EXB841 or the EXB842 of IGBT by its I/O mouth, the IGBT switch is opened triangle L, N end at substation bus bar PT and is formed sinusoidal signal according to conducting of SPWM form and shutoff; CPU forms man-machine interface by the LCDs of its I/O mouth driving display circuit; Display circuit then intuitively shows test result.

Described proving installation can be to the voltage signal of 2 to 10 kinds of different frequencies of tested electrical network output, and the scope of frequency is 0.01Hz～20Hz.

The present invention has following beneficial effect:

1, because the present invention is voltage (electric current) signal that injects two or more different frequency by substation bus bar PT or other final equipment relevant with system busbar to tested network system, avoid of the influence of substation bus bar PT short-circuit impedance by certain calculating to test result, thereby draw the ground capacitance or the capacitance current of tested electrical network, therefore have the outstanding effect that measuring accuracy is higher, test speed is fast, widely applicable.

2, test in the substation bus bar low-pressure side owing to the present invention, therefore simple to operate, safe and reliable.

The drawing explanation

Fig. 1 is the structured flowchart of isolated plant of the present invention.

Fig. 2 is the inverter circuit figure of the invention process Fig. 1.

Fig. 3 is a user mode reference diagram of the present invention.

Preferred embodiment

Fig. 1, Fig. 2 constitute embodiments of the invention 1.As can be seen from Figure 1, special test device of the present invention is formed by connecting by rectification circuit 1, inverter circuit 2, cpu logic control circuit 3, display circuit 4 and working power 5, output terminal, output terminal that the input end of inverter circuit 2 connects rectification circuit 1 connect substation bus bar PT, the input end of rectification circuit 1 connects electric main, and the control signal output ends of cpu logic control circuit 3 connects the control end of inverter circuit 2, the input end that signal output part connects display circuit 4, the output terminal that power end connects working power 5; Rectification circuit 1 will become DC voltage through the interchange 50Hz voltage commutation after isolating, it is 1MBH60 that inverter circuit 2 adopts electronic power switch IGBT device, its model, DC input voitage is reverse into the alternating voltage of changeable frequency, and cpu logic control circuit 3 produces control waves, finishes the calculating of capacitance current and send display circuit 4 to show the result.

As can be seen from Figure 2, inverter circuit 2 adopts electronic power switch IGBT device, and DC input voitage is reverse into the alternating voltage of changeable frequency, and will produce signal voltage/electric current injection electrical network of changeable frequency.

In the present embodiment: rectification circuit 1 adopts common full bridge rectifier, will become direct current through the interchange 50Hz voltage commutation after isolating, for inverter circuit 2 provides direct supply; It is 1MBH60 that inverter circuit 2 adopts electronic power switch IGBT device, its model, DC input voitage is reverse into the alternating voltage of changeable frequency, and the signal voltage/electric current that will produce changeable frequency injects electrical network, the gating pulse employing Sine Modulated pulse SPWM of IGBT electronic power switch; Cpu logic control circuit 3 is made of 51 series monolithic 89C58 and peripheral logical circuit commonly used, finish and produce control signal voltage, finish the calculating of capacitance current and show liquor charging is brilliant as a result, the SPWM pulse that CPU regularly produces removes to drive driving element EXB841 or the EXB842 of IGBT by its I/O mouth, the IGBT switch is opened triangle L, N end at substation bus bar PT and is formed sinusoidal signal according to conducting of SPWM form and shutoff; CPU forms man-machine interface by the LCDs of its I/O mouth driving display circuit 4; 4 of display circuits intuitively show test result.Described proving installation can be to the voltage signal of 2 to 10 kinds of different frequencies of tested electrical network output, and the scope of frequency is 0.01Hz～20Hz.

Below in conjunction with accompanying drawing test philosophy of the present invention is described:

As shown in Figure 2, IGBT1, IGBT2 are the electronic power switch that is adopted, ZL is load, the SPWM pulse signal that is regularly produced by CPU is through driving the gate pole of sending into IGBT1 and IBGT2 after amplifying, in the time will on load ZL, obtaining sinusoidal wave positive half-wave, the SPWM signal can be sent into IGBT1, make IGBT1 according to Sine Modulated pulse conducting with end, this moment IGBT2 end; In the time will on load ZL, obtaining sinusoidal wave negative half-wave, the SPWM signal can be sent into IGBT2, make IGBT2 according to Sine Modulated pulse conducting with end, this moment, IGBT1 ended.Change the drive signal cycle of sending into IGBT1 and IGBT2 gate pole simultaneously, just can change load ZL and go up output signal frequency.

As shown in Figure 3, when implementing to measure, only need measuring instrument signal voltage lead-out terminal S1, S2 are connected to substation bus bar PT open delta L, N end with two subsidiary at random connecting lines, according to the good relevant parameter of display screen Instruction Selection, press the size that start key can obtain the system under test (SUT) capacitance current rapidly then.Tester need be exported voltage (electric current) signal of 2～10 kinds of different frequencies in the one-shot measurement process, and signal output waveform can be sinusoidal wave, also can be other form waveform signals such as square wave.Output signal voltage (electric current) frequency is between between the 0.01Hz to 20Hz.The change of output frequency is finished automatically by tester in the measuring process, and guarantees that output frequency is between the 0.01Hz to 20Hz all the time.When output signal frequency was f1, CPU can detect the marking current of outflow S1 terminal and the size of the signal voltage between S1, the S2 in the tester, is designated as I1 and U1 respectively, makes Z1=K ²U1/I1 (K is a bus PT transformation ratio, down together); When changing output frequency, can detect the marking current of outflow S1 terminal and the size of the signal voltage between S1, the S2 equally, be designated as I2 and U2 respectively, make Z2=K to f2 ²U2/I2.Then can get the system under test (SUT) ground capacitance is:

C = \frac{1}{2 π f_{1} f_{2}} \times \sqrt{\frac{{f_{1}}^{2} - {f_{2}}^{2}}{{Z_{2}}^{2} - {Z_{1}}^{2}}}

Therefore capacitive earth current is:

I_{C} = ω_{50} C U_{ph} = \frac{f_{50}}{f_{1} f_{2}} \times \sqrt{\frac{{f_{1}}^{2} - {f_{2}}^{2}}{{Z_{2}}^{2} - {Z_{1}}^{2}}} \times U_{ph}

In the following formula: f ₅₀Corresponding work frequency 50Hz, U _PhBe the specified phase voltage of system.

Claims

1. A method for testing single-phase ground current of a distribution network, characterized in that: inject at least two voltage signals of different frequencies into the grid system under test through a special test device, and measure the voltage signals of the test device when different frequency electrical signals are detected respectively. The current and voltage values at the connection point between the signal output terminal and the measured grid are calculated according to the frequency of the injected electrical signal and the measured current and voltage values to calculate the ground capacitance and the ground capacitance current value of the measured grid.

2. A test method for single-phase ground current of a distribution network according to claim 1, characterized in that: the special test device consists of a rectifier circuit (1), an inverter circuit (2), a CPU logic control circuit (3 ), the display circuit (4) and the working power supply (5), the input end of the inverter circuit (2) is connected to the output end of the rectification circuit (1), the output end is connected to the substation bus PT, and the input end of the rectification circuit (1) The terminal is connected to the AC mains, the control signal output terminal of the CPU logic control circuit (3) is connected to the control terminal of the inverter circuit (2), the signal output terminal is connected to the input terminal of the display circuit (4), and the power supply terminal is connected to the working power supply (5) output terminal; the rectification circuit (1) rectifies the isolated AC 50Hz voltage into a DC voltage, and the inverter circuit (2) adopts a power electronic switching IGBT device, whose model is 1MBH60, to invert the DC input voltage into a variable frequency AC voltage, the CPU logic control circuit (3) generates a control pulse signal, completes the calculation of the capacitor current and sends the result to the display circuit (4) for display.

3. A method for testing single-phase ground current in a distribution network according to claim 2, characterized in that: the rectifier circuit (1) adopts a common full-bridge rectifier circuit to rectify the isolated AC 50Hz voltage into DC, Provide DC power for the inverter circuit (2); the inverter circuit (2) adopts a power electronic switch IGBT device, the model of which is 1MBH60, to invert the DC input voltage into an AC voltage with variable frequency, and generate variable frequency AC voltage The signal voltage/current is injected into the power grid, and the control pulse of the IGBT power electronic switch adopts the sinusoidal modulation pulse SPWM; the CPU logic control circuit (3) is composed of 51 series single-chip microcomputer 89C58 and peripheral logic circuits commonly used to complete the generation of control signal voltage and the completion of capacitive current. Calculate and send the result to the LCD display. The SPWM pulse generated by the CPU regularly drives the IGBT drive device EXB841 or EXB842 through its I/O port. The terminal forms a sinusoidal signal; the CPU drives the liquid crystal display of the display circuit (4) through its I/O port to form a man-machine interface; the display circuit (4) visually displays the test results.

4. A method for testing single-phase ground current in a distribution network according to claim 1, characterized in that: said testing device can output voltage signals of 2 to 10 different frequencies to the tested network, and the frequency range is 0.01 Hz ~ 20Hz.