CN101441240A - Intelligent state monitoring method of medium-pressure switch apparatus - Google Patents

Abstract

The invention relates to a method for monitoring the intelligent state of a medium-voltage switching device, which comprises the steps of collecting voltage and current signals of medium-voltage electric power network, carrying out isolation transform processing, carrying out alternating current sampling, calculating voltage and current effective values, calculating triphrase active power, triphrase total apparent power, reactive power, power factor, active electric energy and reactive electric energy, and carrying out corresponding follow-up monitoring processing operation. The method for monitoring the intelligent state of a medium-voltage switching device has protective function to time overcurrent, current quick-break and single-phrase earthing and has the functions of faults recording and online monitoring and diagnosis. The method can analyze and process the monitored data, judge the remaining service life of the switching device and calculate the maintenance time limit. Furthermore, by connecting and communicating with the monitoring host of a substation comprehensive automatic system, the method is provided with the communication function and simple monitoring function to the state of the switching device. The method has the advantages of simple realization process, lower running cost, stable and reliable working performance and wider application scope.

Description

The medium voltage switchgear equipment intelligent state monitoring method

Technical field

The present invention relates to medium voltage network power transformation field, particularly medium voltage network switchgear technical field specifically is meant a kind of medium voltage switchgear equipment intelligent state monitoring method.

Background technology

In the modern society, along with the development and the application of comprehensive automation system of transformer substation and electrical power distribution automatization system, the intellectuality of switchgear becomes inexorable trend.The equal lack of wisdom monitoring function of switchgear of the prior art; can't realize microcomputer measurement, Microcomputer Protection, with functions such as supervisory system main-machine communication and switching devices running status on-line monitoring, thereby brought very big obstacle and influence for the safe and reliable operation of medium voltage network.

Summary of the invention

The objective of the invention is to have overcome above-mentioned shortcoming of the prior art, provide a kind of and can carry out effectively that the intelligent monitoring of medium voltage network running status, implementation procedure are simple, stable and reliable working performance, scope of application medium voltage switchgear equipment intelligent state monitoring method comparatively widely.

In order to realize above-mentioned purpose, medium voltage switchgear equipment intelligent state monitoring method of the present invention is as follows:

This medium voltage switchgear equipment intelligent state monitoring method, its principal feature are that described method may further comprise the steps:

(1) the voltage and current signal of collection medium voltage network;

(2) the voltage and current signal that collects being carried out isolated variable handles;

(3) the voltage and current signal behind the isolated variable is carried out AC sampling;

(4) information that obtains according to AC sampling is carried out the computing of voltage and current effective value;

(5) three phases active power and the total applied power of three-phase of calculating medium voltage network;

(6) reactive power and the power factor of calculating medium voltage network;

(7) active energy and the reactive energy of calculating medium voltage network;

(8) carry out corresponding subsequent monitoring processing operation according to resulting active energy and reactive energy.

The voltage and current signal of the collection medium voltage network in this medium voltage switchgear equipment intelligent state monitoring method is specially:

Utilize that current transformer and voltage transformer (VT) carry out AC sampling to two line voltages and biphase current in the medium voltage network.

The isolated variable that carries out in this medium voltage switchgear equipment intelligent state monitoring method is handled, and is specially:

The isolated variable that utilizes integrated operational amplifier to carry out the voltage and current signal is handled.

In the AC sampling in this medium voltage switchgear equipment intelligent state monitoring method weekly the sampling number of ripple be 12,16,20 or 24, sampling interval is between 0.8～1.8 millisecond.

The computing of carrying out the voltage and current effective value in this medium voltage switchgear equipment intelligent state monitoring method is specially:

According to following formula calculating voltage effective value U and current effective value I:

$U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_k^2},$ $U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{i}_k^2};$

Wherein, N is ripple sampling number weekly, and value is 12,16,20,24, u _k, i _kThe k time discrete sampling value for voltage, electric current.

The three phases active power of the calculating medium voltage network in this medium voltage switchgear equipment intelligent state monitoring method and the total applied power of three-phase may further comprise the steps:

(11) calculate the three phases active power P of medium voltage network according to following formula:

$P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{abk}}\·i_{\mathrm{ak}}+\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{cbk}}\·i_{\mathrm{ck}}=$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ak}}-u_{\mathrm{bk}})\·i_{\mathrm{ak}}+$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ck}}-u_{\mathrm{bk}})\·i_{\mathrm{ck}}=P_1+P_2;$

(12) calculate the total applied power S of three-phase of medium voltage network according to following formula:

S＝U _ab·I _a+U _cb·I _c。

The reactive power and the power factor of the calculating medium voltage network in this medium voltage switchgear equipment intelligent state monitoring method may further comprise the steps:

(21) calculate the reactive power Q of medium voltage network according to following formula:

$Q=\sqrt{S^2-P^2};$

(22) calculate the powerfactorcos of medium voltage network according to following formula:

cosφ＝P/S。

The active energy and the reactive energy of the calculating medium voltage network in this medium voltage switchgear equipment intelligent state monitoring method may further comprise the steps:

(31) calculate the active energy W of medium voltage network according to following formula _P:

W _P＝∑P _kΔt；

(32) calculate the reactive energy W of medium voltage network according to following formula _Q:

W _Q＝∑Q _kΔt。

It has adopted the medium voltage switchgear equipment intelligent state monitoring method of this invention, owing to can be measured to parameters of electric power such as electrical network three-phase voltage, three-phase current, active power, reactive power, power factor and electric energy; Have band time overcurrent, current quick-breaking and one-phase ground protection function, and the failure wave-recording function is arranged, the current waveform in 10 cycles before and after the record electric network fault; Have on-line monitoring and diagnostic function, can analyze and handle, judge the remaining life of switchgear and calculate service interval the data that monitor; Can also be connected with the monitoring host computer of comprehensive automation system of transformer substation and communicate by letter simultaneously, thereby have communication function and simple switchgear status monitoring function, and implementation procedure is simple, operating cost is lower, stable and reliable working performance, the scope of application are comparatively extensive.

Description of drawings

Fig. 1 is the workflow diagram of medium voltage switchgear equipment intelligent state monitoring method of the present invention.

Embodiment

In order more to be expressly understood technology contents of the present invention, describe in detail especially exemplified by following examples.

See also shown in Figure 1, this medium voltage switchgear equipment intelligent state monitoring method, comprising following steps:

(1) the voltage and current signal of collection medium voltage network is specially:

Utilize that current transformer and voltage transformer (VT) carry out AC sampling to two line voltages and biphase current in the medium voltage network;

(2) the voltage and current signal that collects is carried out isolated variable and handles, be specially:

The isolated variable that utilizes integrated operational amplifier to carry out the voltage and current signal is handled;

(3) the voltage and current signal behind the isolated variable is carried out AC sampling, corresponding sampling number is 12,16,20 or 24, and sampling interval is between 0.8～1.8 millisecond;

(4) information that obtains according to AC sampling is carried out the computing of voltage and current effective value, is specially:

According to following formula calculating voltage effective value U and current effective value I:

$U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_k^2},$ $I=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{i}_k^2};$

Wherein, N is ripple sampling number weekly, and value is 12,16,20,24, and uk, ik are the k time discrete sampling value of voltage, electric current;

(5) three phases active power and the total applied power of three-phase of calculating medium voltage network may further comprise the steps:

(a) calculate the three phases active power P of medium voltage network according to following formula:

$P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{abk}}\·i_{\mathrm{ak}}+\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{cbk}}\·i_{\mathrm{ck}}=$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ak}}-u_{\mathrm{bk}})\·i_{\mathrm{ak}}+$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ck}}-u_{\mathrm{bk}})\·i_{\mathrm{ck}}=P_1+P_2;$

(b) calculate the total applied power S of three-phase of medium voltage network according to following formula:

S＝U _ab·I _a+U _eb·I _e；

(6) reactive power and the power factor of calculating medium voltage network may further comprise the steps:

(a) calculate the reactive power Q of medium voltage network according to following formula:

$Q=\sqrt{S^2-P^2};$

(b) calculate the powerfactorcos of medium voltage network according to following formula:

cosφ＝P/S；

(7) active energy and the reactive energy of calculating medium voltage network may further comprise the steps:

(a) calculate the active energy W of medium voltage network according to following formula _P:

W _P＝∑P _kΔt；

(b) calculate the reactive energy W of medium voltage network according to following formula _Q:

W _Q＝∑Q _kΔt；

(8) carry out corresponding subsequent monitoring processing operation according to resulting active energy and reactive energy.

In the middle of reality is used, described intelligent cell is a core with the Intel87C196KC single-chip microcomputer, partly is made up of single-chip microcomputer ultimate system, analog acquisition circuit, switching value input/output circuitry, RS-485 serial communication interface, keyboard and LCD display circuit, power supply etc.Each element circuit adopts modular dongle configuration, and all plug-in units are encapsulated in the metal shell, is installed on the switchgear (switch cubicle original instrument relay chamber or case for circuit breaker closely-spaced in) by the shockproof cushioning device.

The single-chip microcomputer ultimate system is as follows:

The single-chip microcomputer ultimate system is made up of the storer of CPU and expansion.CPU selects high performance Intel 87C196KC chip for use.87C196KC is 16 single-chip microcomputers, its fast operation (dominant frequency can run to 20MHz); 512B data-carrier store RAM and 16kB program storage are arranged in the sheet, and the latter can be used for the cure applications program; Have 4 high speed input channels (HSI) and 4 high speed output channels (HSO), can be used for the input and the output of switching value, and HSO can produce and export width and all adjustable PWM (width modulation) signal of cycle; 8 analog input channels (P0:ACH0～ACH7) and traffic pilot, sampling holder and 1 10 A/D converter are arranged in the sheet.

System extends out 1 6264A (8kB) RAM at CPU, is used for record trouble front and back current waveform data take place.Although the program storage of 16kB is arranged in the 87C196KC sheet, because application program is bigger, capacity does not apply and uses, so extend out 1 2764A (8kB) EPROM program storage.Expand 1 Serial E 2PROM storer X25043 chip in addition, its inner integrated E2PROM of Watchdog timer, electrification reset controller and 512B capacity.E2PROM is used for operational factors such as memory protection setting valve, can write again.

The analog acquisition circuit is as follows:

The realization of measurement and defencive function will be gathered the voltage and current signal of electrical network.Analog quantity adopts the AC sampling mode, and signal is from the current transformer (CT) and the voltage transformer (VT) (PT) of electrical network.At medium voltage network, measuring and protecting generally only needs to gather two line voltages and biphase current, and every phase current is divided into measuring-signal and guard signal again.Be to realize the one-phase ground protection of low current neutral grounding electric network, need to obtain zero-sequence current or obtain the residual voltage signal from the openings delta two ends of the voltage transformer (VT) of Y0/Y0/ openings delta wiring from zero sequence current mutual inductor.

From the input range requirement that electric current and the voltage signal of standard CT and PT can not adapt to Chip Microcomputer A/D converter, need carry out conversion.Simultaneously, intelligent cell also will be isolated with strong power system.Adopt commercially available micro mutual inductor to finish the isolated variable and the voltage formation work of simulating signal in the specific embodiments of the present invention.

This micro mutual inductor small volume and less weight can directly be welded on the printed circuit board (PCB), and is resin-sealed entirely, the isolation height.Input termination standard CT or PT secondary side.Secondary side adds one-level operational amplifier (OP07 type) magnitude of current is transformed into voltage, by regulating the feedback resistance R1 of operational amplifier, obtains desired voltage output at output terminal.

The sampling maintenance of simulated measurement input circuit, multi-way switch and analog to digital conversion link adopt the MAX197 chip of a Maxim company, it is 12 signal acquiring systems of single supply, multirange, the inner sampling/maintenance of 8 road input tapes and multi-way switch, clock, reference voltage, and be 6.0 μ s switching time.

For the switching value input/output circuitry:

The switching value of input comprises two classes: a class is the auxiliary contact of equipment such as isolating switch, disconnector and the contact of relevant relay, with the duty (open or close) that detects these equipment; Another kind of is some contacts of intelligent cell device, for example the change-over switch on the relay tip of switching value output loop and the device panel.The switching value of output comprises circuit breaker trip pulse and signal.

The high speed input channel (HSI) and the high speed output channel (HSO) of 87C196KC single-chip microcomputer are passed through in the I/O of switching value, but must utilize photoelectrical coupler that light current and forceful electric power are isolated.The tripping operation pulse signal should have certain width, and this can be easily formed by the pwm signal of 87C196KC single-chip microcomputer.Trip signal makes corresponding auxiliary reclay action by CPU output latch control Driver Circuit.

Communication interface circuit is as follows:

Communicating by letter between the intelligent cell of switchgear and the main frame of comprehensive automation system of transformer substation adopted the RS-485 serial communication mode.RS-485 is half-duplex operation, and maximum communication distance is 1200m, and the message transmission rate of this moment is 100kb/s; If communication distance is 120m, then message transmission rate can reach 1Mb/s.In order to simplify communication mechanism, adopt the minimal form that has only 2 signal line to connect.Wherein, the TTL logic level signal of single-chip microcomputer TXD (serial output) port output is isolated (6N137) by photoelectricity, is converted to the RS-485 level signal by the MAX485 chip, sends to the supervisory system main frame.Vice versa.Physical circuit and principle can be with reference to the following pertinent literatures of prior art:

Huang Shaoping, Qin Zuze. intelligent electrical apparatus RS-485 communication design [J]. low-voltage electrical apparatus, 2003, (3): 24-26.

Algorithmic procedure is as follows:

Intelligent cell adopts the AC sampling mode, and the sampling number of ripple is optional 12,16,20 or 24 weekly, and promptly sampling interval is between 0.8～1.8ms.

Measurement Algorithm is as follows:

Voltage, current effective value are:

$U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_k^2}\·\·\·\·\·\·\left(1\right)$

$U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{i}_k^2}\·\·\·\·\·\·\left(2\right)$

In the formula: N is ripple sampling number weekly, and value is 12,16,20,24, u _k, i _kThe k time discrete sampling value for voltage, electric current.

Medium voltage network is a small current neutral grounding system, and power can calculate with two watts of meter methods.Calculating formula after the total active power discretize of three-phase is:

$P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{abk}}\·i_{\mathrm{ak}}+\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{cbk}}\·i_{\mathrm{ck}}=$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ak}}-u_{\mathrm{bk}})\·i_{\mathrm{ak}}+$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ck}}-u_{\mathrm{bk}})\·i_{\mathrm{ck}}=P_1+P_2\·\·\·\·\·\·\left(3\right)$

The total applied power of three-phase is as follows:

S＝U _ab·I _a+U _cb·I _c ......(4)

Can calculate reactive power and power factor in view of the above:

$Q=\sqrt{S^2-P^2}\·\·\·\·\·\·\left(5\right)$

cosφ＝P/S ......(6)

Active energy and reactive energy are calculated as follows:

W _P＝∑P _kΔt ......(7)

W _Q＝∑Q _kΔt ......(8)

Must point out, the electric flux that above method is calculated, precision may not satisfy the requirement of electric energy metrical, only is suitable for internal examination and uses.Measuring error mainly comprises two aspects: truncation error in the measurement and the asynchronous error of sampling.Because the measured value of voltage, electric current, power all adopts discretize to handle, thereby truncation error is arranged.The asynchronous error of sampling is because mains frequency fluctuation, and sample frequency can not strictly keep producing synchronously with mains frequency.If take hardware to measure mains frequency,, can improve measuring accuracy with the time interval of this frequency decision sampling.

For the status monitoring of switchgear, need the project of monitoring more, as mechanical property, current temperature, condensation, electrical insulation properties etc.These monitoring economic costs are big, realize also difficulty, and whether it is necessary or not is worth discussion.But, the status monitoring of medium voltage switchgear equipment still can be considered following several:

1. whether breaker operator number of times statistics-monitoring breaker reaches specify mechanical life-span number of times or reaches and need carry out maintenance times;

2. its residual electricity life-span is predicted in the electrical wear of dropout current weighted value-indirect monitoring contact of breaker;

3. bus junction temperature.Just can accomplish that the bus temperature monitoring adopts digital temperature sensor to be not difficult to realize for preceding two according to current sampling data and software processes.

The software of intelligent cell is made of debugged program and working procedure.Carry out which program by working mode selection switch on the panel or the decision of the menu on the LCD display.The main task of debugged program is to each plug-in unit debugging of intelligent cell and the protection working value is set, realizes by keyboard commands.Working procedure comprises following functional module:

1. to the each several part initialization of intelligent cell;

2. to alternating voltage and electric current timing sampling and data processing;

3. protect logic determines and tripping operation to handle;

4. switch amount is gathered, and the trip signal implementation status is fed back;

5. serial communication interrupt service routine;

6. keyboard interrupt service routine;

7. the self check concurrent alerting signal that circulates;

8. show.

It has adopted above-mentioned medium voltage switchgear equipment intelligent state monitoring method, owing to can be measured to parameters of electric power such as electrical network three-phase voltage, three-phase current, active power, reactive power, power factor and electric energy; Have band time overcurrent, current quick-breaking and one-phase ground protection function, and the failure wave-recording function is arranged, the current waveform in 10 cycles before and after the record electric network fault; Have on-line monitoring and diagnostic function, can analyze and handle, judge the remaining life of switchgear and calculate service interval the data that monitor; Can also be connected with the monitoring host computer of comprehensive automation system of transformer substation and communicate by letter simultaneously, thereby have communication function and simple switchgear status monitoring function, and implementation procedure is simple, operating cost is lower, stable and reliable working performance, the scope of application are comparatively extensive.

In this instructions, the present invention is described with reference to its certain embodiments.But, still can make various modifications and conversion obviously and not deviate from the spirit and scope of the present invention.Therefore, instructions and accompanying drawing are regarded in an illustrative, rather than a restrictive.

Claims (8)

1, a kind of medium voltage switchgear equipment intelligent state monitoring method is characterized in that, described method may further comprise the steps:

(1) the voltage and current signal of collection medium voltage network;

(2) the voltage and current signal that collects being carried out isolated variable handles;

(3) the voltage and current signal behind the isolated variable is carried out AC sampling;

(4) information that obtains according to AC sampling is carried out the computing of voltage and current effective value;

(5) three phases active power and the total applied power of three-phase of calculating medium voltage network;

(6) reactive power and the power factor of calculating medium voltage network;

(7) active energy and the reactive energy of calculating medium voltage network;

(8) carry out corresponding subsequent monitoring processing operation according to resulting active energy and reactive energy.

2, medium voltage switchgear equipment intelligent state monitoring method according to claim 1 is characterized in that, the voltage and current signal of described collection medium voltage network is specially:

Utilize that current transformer and voltage transformer (VT) carry out AC sampling to two line voltages and biphase current in the medium voltage network.

3, medium voltage switchgear equipment intelligent state monitoring method according to claim 1 is characterized in that, the described isolated variable that carries out is handled, and is specially:

The isolated variable that utilizes integrated operational amplifier to carry out the voltage and current signal is handled.

4, medium voltage switchgear equipment intelligent state monitoring method according to claim 1 is characterized in that, in the described AC sampling weekly the sampling number of ripple be 12,16,20 or 24, sampling interval is between 0.8～1.8 millisecond.

5, medium voltage switchgear equipment intelligent state monitoring method according to claim 1 is characterized in that, the described computing of carrying out the voltage and current effective value is specially:

According to following formula calculating voltage effective value U and current effective value I:

$U=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{u}_k^2},$ ? $I=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{i}_k^2};$

Wherein, N is ripple sampling number weekly, and value is 12,16,20,24, u _k, i _kThe k time discrete sampling value for voltage, electric current.

6, medium voltage switchgear equipment intelligent state monitoring method according to claim 5 is characterized in that, the total applied power of the three phases active power of described calculating medium voltage network and three-phase may further comprise the steps:

(11) calculate the three phases active power P of medium voltage network according to following formula:

$P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{abk}}\·i_{\mathrm{ak}}+\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_{\mathrm{cbk}}\·i_{\mathrm{ck}}=$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ak}}-u_{\mathrm{bk}})\·i_{\mathrm{ak}}+$

$\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(u_{\mathrm{ck}}-u_{\mathrm{bk}})\·i_{\mathrm{ck}}=P_1+P_2;$

(12) calculate the total applied power S of three-phase of medium voltage network according to following formula:

S＝U _ab·I _a+U _cb·I _c。

7, medium voltage switchgear equipment intelligent state monitoring method according to claim 6 is characterized in that, the reactive power of described calculating medium voltage network and power factor may further comprise the steps:

(21) calculate the reactive power Q of medium voltage network according to following formula:

$Q=\sqrt{S^2-P^2};$

(22) calculate the powerfactorcos of medium voltage network according to following formula:

cosφ＝P/S。

8, medium voltage switchgear equipment intelligent state monitoring method according to claim 7 is characterized in that, the active energy of described calculating medium voltage network and reactive energy may further comprise the steps:

(31) calculate the active energy W of medium voltage network according to following formula _P:

W _P＝ΣP _kΔt；

(32) calculate the reactive energy W of medium voltage network according to following formula _Q:

W _Q＝ΣQ _kΔt。

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