CN105093060A - Low-voltage DC power transmission and distribution on-line insulation monitoring method, and adaptive end grounding line selection device - Google Patents
Low-voltage DC power transmission and distribution on-line insulation monitoring method, and adaptive end grounding line selection device Download PDFInfo
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Abstract
The invention provides a low-voltage DC power transmission and distribution on-line insulation monitoring method, and an adaptive end grounding line selection device. The adaptive end grounding line selection device comprises a master control module and a leakage current measuring module. The master control module is provided with an external communication interface, an internal communication interface and an adaptive detection circuit, wherein the adaptive detection circuit detects in real time voltage to earth values of positive and negative busbars and determines whether to switch a self-balancing resistor to the positive and negative busbars; the leakage current measuring module is provided with a zero sequence mutual inductor, a signal processing unit and a communication circuit, wherein the zero sequence mutual inductor detects branch electric leakage signals, and connects with the internal communication interface of the master control module through the communication circuit. The method can and device can monitor in real time the insulation status of a plurality of power generation branches, and automatically withdraw the self-balancing resistor when other grounding balancing resistors exist in a system, or automatically switch the self-balancing resistor; meanwhile numbers of branches with reduced branch insulation states are uploaded through a centralized monitor, thereby facilitating monitoring and maintenance.
Description
Technical field
The present invention relates to low-voltage direct power transmission and distribution on-line insulation monitoring technical field, be particularly useful for the self-adaptation end line-selected earthing device of the photovoltaic power generation plate in photovoltaic generating system and the on-line insulation monitoring method between Intelligent photovoltaic combiner box and use.
Background technology
The world today, the fossil energy such as coal, oil signals for help repeatedly, and problem of environmental pollution is increasingly serious.And sun power is as the regenerative resource of most potentiality, because of the economy of the unlimitedness of its reserves, the ubiquity of existence, the spatter property of utilization and practicality, more and more favor by people.Greatly develop photovoltaic industry, active development sun power, obtain unprecedented attention in the world, become the important component part of various countries' strategy of sustainable development.Photovoltaic industry also claims solar cell industry, namely utilizes sun power and semi-conductor electronic device to absorb solar radiation energy, and makes it the industry being converted to electric energy.In large-sized photovoltaic grid-connected system, in order to reduce the wiring quantity between photovoltaic module and inverter, being convenient to safeguard, improving reliability, reduce costs simultaneously, generally need between photovoltaic module and inverter, increase direct current collector-shoe gear.By using photovoltaic array conflux box, user can according to the DC voltage range of inverter input, the photovoltaic module of the same size of some is connected into a photovoltaic module tandem, again by several tandems access photovoltaic array conflux box, by exporting after lightning protection device and isolating switch, thus facilitate the access of rear class inverter.
Photovoltaic combiner box is applied to a kind of smart machine for protecting photoelectric cell tandem and peripheral auxiliary element and monitor in Intelligent photovoltaic electricity generation system, is the novel product produced along with the large-scale application of photovoltaic generation.Along with the fast development of photovoltaic industry, for the security of photovoltaic combiner box, miniaturization, intelligent and low-power consumption proposes more and more higher requirement, the Intelligent photovoltaic combiner box of current routine can only realize branch current and measure, SPD and on off state monitoring, the functions such as communication, on-line monitoring cannot be carried out in real time to wire insulation situation, and due to branch road in photovoltaic generating system more, occur that at branch road the situations such as insulation damages cause insulating and the normal operation of generating set when declining, can be affected, field maintenance person is difficult to detect in time, investigate out insulation decline branch road, while bringing hidden danger to the personal safety of field maintenance person, too increase the workload of on-the-spot operation maintenance personnel.
" a kind of on-line insulation monitoring system being applicable to grid-connected photovoltaic system " shown in Fig. 1, utility application numbers 201220708530.8.Wherein grid-connected photovoltaic system comprises one group of many groups photovoltaic electrification component connected, DC cabinet and inverter, often organize the header box that described photovoltaic electrification component comprises solar panels and connects solar panels and DC cabinet, DC cabinet is connected with described inverter via positive and negative busbar, inverter is connected with external power grid, it is characterized in that, on-line insulation monitoring system for grid-connected photovoltaic system comprises insulation Intelligent electric leakage sensor, insulation balance resistance, insulation voltage transmitter, insulating monitor and host computer, wherein, insulation Intelligent electric leakage flow sensor is as between header box and DC cabinet, and communicated with insulating monitor by RS485 communication interface, insulation balance resistance one end ground connection, the other end is connected with positive and negative busbar, insulation balance resistance is connected with insulating monitor via insulation voltage transmitter with positive and negative busbar, insulating monitor comprises data reception module, data processing module, IO port and communication module, wherein data reception module is in order to receive the data of leakage current sensor and insulating transformer transmission, data processing module is used for the data of data reception module to carry out statistics and aggregation process, alarm module is connected with data processing module, when the data of data processing module exceed corresponding setting value, described alarm module is opened and is reported to the police, be connected with external alarming execution device between IO port, when each equipment in the on-line insulation monitoring system of grid-connected photovoltaic system or circuit break down, IO port driver alarming execution device is reported to the police, described data processing module is communicated with host computer by RS485 or tcp/ip communication interface by communication module.
Subject matter and the shortcoming of prior art are as follows:
The fault branch of concrete photovoltaic string can not be located, investigate workload when photovoltaic string is more comparatively large, if each header box needs to increase a set of insulation monitoring and warning device, purchase with later maintenance cost higher;
Usual insulation monitoring and warning device measures both positive and negative polarity voltage-to-ground value by balance resistance and switching unbalanced resistance, utilizes the magnitude of voltage of the both positive and negative polarity measured to calculate insulating resistance value, as shown in Figure 2.If there is other insulation monitoring and warning device in system, will certainly cause in system and there is multiple balance resistance to earth, balance resistance resistance diminished, causes measured deviation, the alerting signal of output error.
Summary of the invention
The object of the invention is to realize on-line real time monitoring branch insulation situation, the abort situation for photovoltaic string can accurately be located; Main control module can detect positive and negative busbar voltage-to-ground value in real time, judges whether that switching Equilibrium resistance is to positive and negative busbar, realizes the online Insulation monitoring of self-adaptation.
The technical solution used in the present invention is:
A kind of adaptive end line-selected earthing device, described adaptive end line-selected earthing device comprises main control module and leakage current measurement module, wherein,
Described main control module is arranged an external communication interface, an internal communications interface and a self-adapting detecting circuit, described self-adapting detecting circuit detects positive and negative busbar voltage-to-ground value in real time, judges whether that switching Equilibrium resistance is to positive and negative busbar; Described internal communications interface is connected to the communication interface of electric leakage measurement module, and external communication interface is connected to centralized monitor;
Described leakage current measurement module is arranged at least one road zero-sequence transformer, a signal processing unit and telecommunication circuit, described zero-sequence transformer detection branch electric leakage signal, electric leakage signal is converted to leakage current value by described signal processing unit, and is undertaken alternately by the internal communications interface of telecommunication circuit and main control module.
Described self-adapting detecting circuit comprises 2 balance resistances and 2 relay change-over switch K1 and K2, and described relay change-over switch K1 one end is connected to bus positive pole, and the other end is connected to a described balance resistance, and this balance resistance is connected to ground; Described change-over switch K2 one end is connected to bus negative pole, and the other end is connected to another balance resistance, and this balance resistance is connected to ground.
Described adaptive end line-selected earthing device also comprises centralized monitor, and described centralized monitor is connected with the external communication interface of main control module, and described main control module is communicated with centralized monitor by external communication interface.
The present invention also proposes a kind of low-voltage direct power transmission and distribution on-line insulation monitoring method using adaptive end line-selected earthing device, comprises step:
1) main control module timing disconnects relay K 1/K2, self-adapting detecting circuit measuring busbar voltage U, positive and negative busbar voltage-to-ground value U+/U-;
2) when positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-is 0V, and this state continue 5 minutes, can judge that, without other balance resistances in system, main control module is closing relay K1, K2 then, drop into the balance resistance of self to bus;
3) when positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-be all greater than 0V time, and this state continued after 5 minutes, then judge have other equipment to drop into balance resistance in system, main control module keeps Equilibrium resistance off-state;
4), in device normal course of operation, main control module is implemented to measure positive pole voltage-to-ground U+, negative pole voltage-to-ground value U-, when | when U+-U-|> sets threshold value, and the duration was more than 5 minutes, then confirm that this situation is stable fault case;
5) in main control module, internal communications interface is connected with detection of electrical leakage module communication interface, detection of electrical leakage module uploads branch road sequence number and corresponding electrical leakage to main control module by communication interface, then detection of electrical leakage module uploads the leakage current of each branch road sequence number and corresponding branch road, master control is sorted to branch road sequence number according to branch road leakage current order from big to small, by fault branch numbered transmission to main control module external communication interface, be grounded route selection.
The detection action threshold value of described positive and negative busbar pressure reduction is over the ground non-definite value, and can carry out adjustment setting according to system state, general D.C. isolation monitoring device technical conditions require that pressure reduction threshold value is not more than 10% of rated voltage.
The invention provides a kind of online insulation measuring apparatus used in photovoltaic combiner box, this device can Real-Time Monitoring multiple generating branch insulation situation, there is the balance resistance automatically exiting self during other earth balance resistance in systems in which, otherwise the balance resistance of automatic switching self, data are passed to main control module by bus mode by equipment, main control module implementing monitoring positive and negative busbar voltage-to-ground, if positive and negative busbar voltage-to-ground difference exceedes setting value, then main control module is communicated with centralized monitor by communication interface, the branch road number that branch insulation state declines is uploaded by centralized monitor, facilitate monitoring and safeguard.
Accompanying drawing explanation
Fig. 1 is the on-line insulation monitoring system schematic of existing grid-connected photovoltaic system;
Fig. 2 is that the multiple balance resistance of existing insulation monitoring and warning device is to earth circuit diagram;
Fig. 3 is measurement module structural representation;
Fig. 4 is the present invention's adaptive end line-selected earthing device structural representation.
Embodiment
For making the object, technical solutions and advantages of the present invention clearly understand, below in conjunction with the drawings and specific embodiments, the present invention is described in more detail.
A kind of adaptive end line-selected earthing device, comprises measurement module and main control module.
Measurement module is arranged at least one road zero-sequence transformer, signal processing unit, telecommunication circuit and a power circuit, as shown in Figure 3.Zero-sequence transformer detection branch electric leakage signal, is converted to leakage current value by signal processing unit, and is undertaken alternately by the internal communications interface of telecommunication circuit and main control module; The wire of same branch road is through zero-sequence transformer coil, in the iron core of alternation symmetrical voltage or Impetus of Current Source, if there is direct current constant magnetic field simultaneously, the symmetry of the alternating flux in iron core will be destroyed, the positive and negative half-wave phase of flux waveforms will change, correspondingly, will there is relative displacement in the positive and negative half-wave detected in winding output voltage.The direction of positive and negative half-wave variable quantity and size can reflect direction and the size of DC bias current, by the dutycycle of the input capture port analysis square wave of MCU, can calculate the numerical value of branch road leakage current.
Main control module comprises an external communication interface, an internal communications interface and a self-adapting detecting circuit, as shown in Figure 4.Main control module timing disconnects relay K 1/K2, self-adapting detecting circuit measuring busbar voltage U, positive and negative busbar voltage-to-ground value U+/U-, when positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-is 0V, and this state continued after 5 minutes, can judge in system without other balance resistances, main control module is closing relay K1, K2 then, drops into the balance resistance of self to bus; When positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-be all greater than 0V time, and this state continues then to judge have other equipment to drop into balance resistance in system after 5 minutes, and main control module keeps Equilibrium resistance off-state.Other insulation detection devices may be there are cut bridge route selection operation in deterministic process, positive and negative busbar magnitude of voltage is caused to change, according to field operation experiences, insulation detection device fault location time can not more than 3 minutes, the delay time that main control module detects change in voltage is designed to 5 minutes, effectively can hide other devices switching electric bridge in system and bring voltage fluctuation countermeasure set to judge.
In main control module, internal communications interface is connected with detection of electrical leakage module communication interface, detection of electrical leakage module uploads branch road electrical leakage to main control module by communication interface, the positive and negative busbar voltage-to-ground difference that main control module is measured is greater than detection action threshold value, and the duration was more than 5 minutes, then detection of electrical leakage module uploads the leakage current of each branch road sequence number and corresponding branch road, master control is sorted to branch road sequence number according to branch road leakage current order from big to small, by fault branch numbered transmission to main control module external communication interface, be grounded route selection.
Above-described specific embodiment; further detailed description has been carried out to object of the present invention, technical scheme and beneficial effect; be understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (5)
1. an adaptive end line-selected earthing device, is characterized in that: described adaptive end line-selected earthing device comprises main control module and leakage current measurement module, wherein,
Described main control module is arranged an external communication interface, an internal communications interface and a self-adapting detecting circuit, described self-adapting detecting circuit detects positive and negative busbar voltage-to-ground value in real time, judges whether that switching Equilibrium resistance is to positive and negative busbar; Described internal communications interface is connected to the communication interface of electric leakage measurement module, and external communication interface is connected to centralized monitor;
Described leakage current measurement module is arranged at least one road zero-sequence transformer, a signal processing unit and telecommunication circuit, described zero-sequence transformer detection branch electric leakage signal, electric leakage signal is converted to leakage current value by described signal processing unit, and is undertaken alternately by the internal communications interface of telecommunication circuit and main control module.
2. adaptive end line-selected earthing device according to claim 1, it is characterized in that: described self-adapting detecting circuit comprises 2 balance resistances and 2 relay change-over switch K1 and K2, described relay change-over switch K1 one end is connected to bus positive pole, the other end is connected to a described balance resistance, and this balance resistance is connected to ground; Described change-over switch K2 one end is connected to bus negative pole, and the other end is connected to another balance resistance, and this balance resistance is connected to ground.
3. adaptive end line-selected earthing device according to claim 2, it is characterized in that: described adaptive end line-selected earthing device also comprises centralized monitor, described centralized monitor is connected with the external communication interface of main control module, and described main control module is communicated with centralized monitor by external communication interface.
4. use the low-voltage direct power transmission and distribution on-line insulation monitoring method of claim 1-3 device described in one of them, it is characterized in that comprising step:
1) main control module timing disconnects relay K 1/K2, self-adapting detecting circuit measuring busbar voltage U, positive and negative busbar voltage-to-ground value U+/U-;
2) when positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-is 0V, and this state continue 5 minutes, can judge that, without other balance resistances in system, main control module is closing relay K1, K2 then, drop into the balance resistance of self to bus;
3) when positive and negative busbar voltage U be greater than 0V, positive and negative busbar voltage-to-ground value U+/U-be all greater than 0V time, and this state continued after 5 minutes, then judge have other equipment to drop into balance resistance in system, main control module keeps Equilibrium resistance off-state;
4), in device normal course of operation, main control module is implemented to measure positive pole voltage-to-ground U+, negative pole voltage-to-ground value U-, when | when U+-U-|> sets threshold value, and the duration is more than 5Min, then confirm that this situation is stable fault case;
5) in main control module, internal communications interface is connected with detection of electrical leakage module communication interface, detection of electrical leakage module uploads branch road electrical leakage to main control module by communication interface, the each branch road leakage current value uploaded detection of electrical leakage module is according to sorting from big to small, by fault branch numbered transmission to main control module external communication interface, send centralized monitor to by external communication interface, be grounded route selection.
5. monitoring method according to claim 4, is characterized in that: the detection action threshold value of described positive and negative busbar pressure reduction is over the ground non-definite value, carries out adjustment setting, require that pressure reduction threshold value is not more than 10% of rated voltage according to system state.
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Application publication date: 20151125 |