CN201965190U - Insulation detecting device for direct current system - Google Patents

Abstract

The utility model discloses an insulation detecting device for a direct current system, which comprises a bus unbalancedness detecting unit and a branch circuit insulation detecting unit. The bus unbalancedness detecting unit is provided with a detecting circuit for detecting a positive earthing resistance and a negative earthing resistance of a bus of the direct current system. The detecting circuit is provided with divider resistances to earth, which have the same resistance value and are respectively connected in parallel with a testing resistance. The divider resistances to earth are grounded through electronic switches according to a certain on-off sequence. When the positive earthing resistance and/or the negative earthing resistance which are detected by the detecting circuit reach a preset alarm value, the branch circuit insulation detecting unit for detecting a branch circuit insulation reduction value is started. The branch circuit insulation reduction value is provided with a current transformer for detecting the size of a branch circuit leakage current. By an output voltage of the current transformer, the size of the branch circuit leakage current and the branch circuit insulation reduction resistance value are obtained. By the device provided by the utility model, the problems of detection dead zone and unsafety in the prior art can be effectively solved.

Description

A kind of insulation tester for DC system

Technical field

The utility model relates to the electric circuit inspection field, more particularly relates to a kind of insulation tester for DC system.

Background technology

Straight-flow system in the generating plant, the utilization of transformer station and other places is very extensive and branching networks are huge, it is used for supplying with dc loads such as relay protection, control, signal, computer monitoring, emergency lighting, ac uninterrupted power supply.In order to guarantee the normal operation of these branching networks, prevent to cause the accident because of environment aging circuit and other reasons descend its insulation, detect very important to the insulation of straight-flow system.

In the prior art, detect the bus that is divided into straight-flow system for the insulation of straight-flow system and detect and the branch road detection.Wherein, the method for detection straight-flow system bus mainly contains principle of balance bridge and unbalanced bridge principle.The insulation detection device of realizing according to principle of balance bridge is low owing to cost, computing simply is widely used.But it can not detect the situation the when insulation of straight-flow system positive and negative electrode is equal to descend.And can detect the equal situation about descending of straight-flow system positive and negative electrode insulation according to the insulation detection device that the unbalanced bridge principle realizes, but there is latency issue in the detection of stake resistance, sensitivity is lower.The main method that detects for branch road has the frequency conversion detection principle, and the stake resistance that utilizes it to detect is subjected to the straight-flow system restriction of distributed capacitance over the ground, and the ripple coefficient of voltage of the low-frequency ac signal that injects increase straight-flow system, influences the safe operation of system.

As seen, in the prior art, to the detection existence detection dead band and the unsafe problems of straight-flow system insulation.

The utility model content

In view of this, the utility model provides a kind of insulation tester for DC system, to solve in the prior art, to the detection existence detection dead band and the unsafe problems of straight-flow system insulation.

For achieving the above object, the utility model provides following technical scheme:

A kind of insulation tester for DC system comprises:

Uneven detecting unit of bus and branch road insulation detecting unit;

The uneven detecting unit of described bus is provided with the testing circuit that is used to detect positive stake resistance of straight-flow system bus and negative stake resistance, described testing circuit is provided with the divider resistance over the ground that resistance equates and be parallel with respectively test resistance, and described divider resistance over the ground by electronic switch according to certain folding order ground connection;

Described branch road insulation detecting unit is used for when the detected positive stake resistance of described testing circuit and/or negative stake resistance reach default alarming value start detection branch road insulation reduction resistance value program; Described branch road insulation detecting unit is provided with the current transformer that is used for the detection branch leakage current, by the output voltage of described current transformer, obtains the size of branch road leakage current, and obtains branch road insulation reduction resistance value.

Wherein, also comprise: branch road status information element and main monitoring unit;

The on off state information that described branch road status information element is used for each branch road that will obtain transfers to described main monitoring unit by communication line;

Described main monitoring unit is used to inquire about branch road information.

Wherein, also comprise: branch road warning information unit;

The warning information that described branch road warning information unit is used for each branch road that will obtain transfers to described main monitoring unit by communication line.

Wherein, also comprise: the background monitoring unit;

Described background monitoring unit is used for the information transmission of the straight-flow system that will obtain by main monitoring unit to remote supervisory and control(ling) equipment.

Via above-mentioned technical scheme as can be known, compared with prior art, the uneven detecting unit of bus detects the testing circuit that is provided with on the basis of principle at unbalanced bridge, the current detecting mode is become the voltage detecting mode, so not only can detect the situation when the positive and negative electrode insulation is equal to descend, and do not have time delay, increase detection sensitivity to stake resistance; And branch road insulation detecting unit adopts the leakage current of current transformer detection branch, and then judges the reduction degree of branch road insulation, efficiently solves the safety problem of being brought when adopting frequency conversion detection principle detection branch.By utilizing insulation tester for DC system provided by the utility model can effectively solve detection dead band and the unsafe problems that exists in the prior art.

Description of drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, accompanying drawing in describing below only is embodiment more of the present utility model, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 detects principle schematic for unbalanced bridge;

Fig. 2 is the structural representation of the utility model embodiment insulation tester for DC system;

Fig. 3 is the synoptic diagram of the testing circuit of the uneven detecting unit of the utility model embodiment bus;

The operating circuit synoptic diagram of branch road insulation detecting unit when Fig. 4 reduces for the utility model embodiment is just insulating;

Branch road insulation detecting unit operating circuit synoptic diagram when Fig. 5 reduces for the negative insulation of the utility model embodiment.

Embodiment

In order to quote and clear, now unbalanced bridge detected principle to be described below:

It is that 2 R1 of divider resistance over the ground, R2 that resistance is identical are set in pick-up unit inside that unbalanced bridge detects, and over the ground divider resistance R1 and R2 by electronic switch K1, K2 according to certain folding order ground connection.

Unbalanced bridge detects principle as shown in Figure 1, and in a sense cycle, the closed K2 of K1 disconnects, and records V1, V2, obtains equation (1):

$\frac{V1}{R1//\mathrm{Rx}}=\frac{V2}{\mathrm{Ry}}---\left(1\right)$

K1 disconnects then, and the K2 closure is measured V1, V2 once more through after the certain time-delay, obtains equation (4):

$\frac{V1}{\mathrm{Rx}}=\frac{V2}{R2//\mathrm{Ry}}---\left(2\right)$

De-connect a cube journey (1), (2) and just can directly try to achieve positive and negative busbar stake resistance Rx, Ry.

Because in measuring process, need positive and negative busbar to throw resistance (that is: divider resistance) over the ground respectively over the ground, so busbar voltage change.In order to obtain measurement result accurately, drop into needs time-delay behind the resistance at every turn, treat that the bus voltage-to-ground is stable after, measure again, therefore detecting needs certain time delay, detection speed is slow.

At the problem that insulation tester for DC system of the prior art exists, the utility model provides a kind of insulation tester for DC system, can effectively solve the detection dead band and the unsafe problems that exist in the prior art.This device comprises:

Uneven detecting unit of bus and branch road insulation detecting unit;

The uneven detecting unit of described bus is provided with the testing circuit that is used to detect positive stake resistance of straight-flow system bus and negative stake resistance, described testing circuit is provided with the divider resistance over the ground that resistance equates and be parallel with respectively test resistance, and described divider resistance over the ground by electronic switch according to certain folding order ground connection;

Described branch road insulation detecting unit is used for when the detected positive stake resistance of described testing circuit and/or negative stake resistance reach default alarming value start detection branch road insulation reduction resistance value program; Described branch road insulation detecting unit is provided with the current transformer that is used for the detection branch leakage current, by the output voltage of described current transformer, obtains the size of branch road leakage current, and obtains branch road insulation reduction resistance value.

In the utility model, the uneven detecting unit of bus detects the testing circuit that is provided with on the basis of principle at unbalanced bridge, the current detecting mode is become the voltage detecting mode, so not only can detect the situation when the positive and negative electrode insulation is equal to descend, and do not have time delay, increase detection sensitivity to stake resistance; And branch road insulation detecting unit adopts the leakage current of current transformer detection branch, and then judges the reduction degree of branch road insulation, efficiently solves the safety problem of being brought when adopting frequency conversion detection principle detection branch.By utilizing insulation tester for DC system provided by the utility model can effectively solve detection dead band and the unsafe problems that exists in the prior art.

In order to monitor the status information of each branch road of straight-flow system in real time, make things convenient for the monitoring of field operator to whole straight-flow system, in another embodiment, insulation tester for DC system provided by the utility model also comprises: branch road status information element, branch road warning information unit, main monitoring unit;

Main monitoring unit is used for the branch road information of receiving branch status information element and the transmission of branch road warning information unit, and information is shown to the operations staff with certain form by display device;

The branch road status information element is used to obtain the state of the switch of each branch road, and the on off state information that obtains is transferred to main monitoring unit by communication line;

Branch road warning information unit is used to obtain the switch abnormality alarming of each branch road, and the warning information that obtains is transferred to main monitoring unit by communication line.

Further, the user is to the real-time remote monitoring of straight-flow system for convenience, and in another embodiment, insulation tester for DC system provided by the utility model also comprises: the background monitoring unit; This unit will can transfer to remote supervisory and control(ling) equipment by communication line from the branch road information that main monitoring unit obtains, for inquiry and the monitoring of long-distance user to straight-flow system information.

Below in conjunction with the accompanying drawing among the utility model embodiment, the technical scheme among the utility model embodiment is clearly and completely described, obviously, described embodiment only is the utility model part embodiment, rather than whole embodiment.Based on the embodiment in the utility model, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the utility model protection.

As shown in Figure 2, the insulation tester for DC system that present embodiment provided comprises: the uneven detecting unit 210 of bus, branch road insulation detecting unit 220, branch road status information element 230, branch road warning information unit 240, background monitoring unit 250, main monitoring unit 260.

Wherein, the uneven detecting unit 210 of bus is used to detect the insulation situation of straight-flow system bus.This unit is provided with testing circuit, is used to detect the positive stake resistance on the bus and the value of negative stake resistance, judges the insulation situation of bus with this.Testing circuit is to design on the basis of unbalanced bridge principle, as shown in Figure 3.This testing circuit is provided with the Rg of divider resistance over the ground that 2 resistances equate and be parallel with respectively test resistance R, and over the ground divider resistance Rg by the first electronic switch JK1 and the second electronic switch JK2 according to certain folding order ground connection.The concrete course of work is:

1) the first electronic switch JK1, the second electronic switch JK2 disconnect, and the A/D mouth by single-chip microcomputer records voltage U m;

2) the first electronic switch JK1 disconnect, the second electronic switch JK2 closure, the A/D mouth by single-chip microcomputer records voltage U j; And with this moment the voltage that records be designated as Uj1;

3) the first electronic switch JK1 closure, the second electronic switch JK2 disconnect, and the A/D mouth by single-chip microcomputer records another voltage U j, and voltage that will this moment is designated as Uj2.

After recording the first electronic switch JK1 and the second electronic switch JK2 being in all voltages of different states, finished the step of test voltage.Can find out that by this testing circuit Uj1 and positive stake resistance R+, negative stake resistance R-have relation, Uj1 also has relation with R+, R-, thereby can obtain following formula (3) and formula (4):

$\frac{\mathrm{Um}-\mathrm{Uj}1}{\mathrm{Uj}2}=\frac{\mathrm{Rg}//R//R+}{R//R-}---\left(3\right)$

$\frac{\mathrm{Um}-\mathrm{Uj}2}{\mathrm{Uj}2}=\frac{R//R+}{\mathrm{Rg}//R//R-}---\left(4\right)$

Simultaneous formula (3) and (4) can obtain the value of R+ and R-:

$R+=\frac{(\mathrm{Uj}2-\mathrm{Uj}1)\×\mathrm{Rg}\×R}{\mathrm{Uj}1(R+\mathrm{Rg})-\mathrm{Uj}2\×\mathrm{Rg}}$

$R-=\frac{(\mathrm{Uj}2-\mathrm{Uj}1)\×\mathrm{Rg}\×R}{R\×\mathrm{Um}-(\mathrm{Uj}1+\mathrm{Uj}2)\×(R+\mathrm{Rg})}$

After positive stake resistance R+ on the straight-flow system bus, negative stake resistance R-draw, can judge insulation situation on the bus according to R+, R-.

When the value of positive stake resistance R+ or negative stake resistance R-has reached default alarming value, illustrate that the insulativity of current straight-flow system is very poor, at this moment start branch road insulation detecting unit 220, carry out the test of branch road insulativity by it.Branch road insulation detecting unit 220 adopts current transformer to detect the size of the leakage current on each branch road.In the present embodiment, selected the current transformer of DC10EA type, specified input current is 10mA, output voltage be 0-+/-2.5V.As shown in Figure 4, when reducing when occurring just insulating, the electric current difference on positive bus-bar and the negative busbar is I2 (unit is mA), then the output U=(I2/10) * 2.5 (V) of Ci Shi current transformer.As shown in Figure 5, reduce when negative insulation occurring, at this moment the output U=-(I2/10) * 2.5 (V) of current transformer.By gathering the output voltage of current transformer, can calculate the size of leakage current I2, thereby obtain the degree that the insulation on the branch road reduces.

Need to prove, because when the positive and negative insulation of appearance all reduced, the degree that insulation reduces was not directly proportional with leakage current, so the concrete size of the insulation resistance value of the testing circuit acquisition major loop (positive and negative busbar) of the uneven detecting unit 210 of employing bus.When having reached default alarming value, just obtain the degree that each branch road insulation reduces by branch road insulation detecting unit 220.Wherein, single-chip microcomputer sends to each unit that needs voltage by the output voltage collection of multi-way switch with the current transformer of different branch.

The switch of each branch road all has the secondary status contact, on off state can be represented in this contact, branch road status information element 230 can get access to the on off state information of all branch roads, and send to main monitoring unit 260 by communication line, make main monitoring unit 260 can inquire the current on off state of branch road at any time.

Further, the minor alarm contact is arranged all on each branch switch, the switch abnormality alarming can be represented in this contact.Branch road warning information unit 240 can get access to the switch warning information of all branch roads, and is sent to main monitoring unit 260 by communication line, and main monitoring unit 260 can be inquired about current alarm state and history alarm information at any time.

Background monitoring unit 250 then can obtain each branch road information of straight-flow system of main monitoring unit 260 storages, and can be sent to remote control equipment, makes that the user can be by the state of each branch road of remote control equipment remote monitoring straight-flow system.

The insulation tester for DC system that the utility model embodiment is provided, the insulation situation by the uneven detecting unit 210 detection buses of bus is applicable to situation about all descending when the positive and negative electrode stake resistance, has solved latency issue, sensitivity is higher; Detect the size of leakage current by branch road insulation detecting unit 220 by current transformer, thereby the insulation that obtains each branch road reduces situation, the safety problem that the ripple coefficient of voltage that does not exist use frequency conversion detection principle to be caused increases.Solved effectively in the prior art by embodiment of the invention institute generator, insulation detects and has dead band and unsafe problem to straight-flow system.

To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the utility model.Multiple modification to these embodiment will be conspicuous concerning those skilled in the art, and defined herein General Principle can realize under the situation that does not break away from spirit or scope of the present utility model in other embodiments.Therefore, the utility model will can not be restricted to these embodiment shown in this article, but will meet and principle disclosed herein and features of novelty the wideest corresponding to scope.

Claims (4)

1. an insulation tester for DC system is characterized in that, comprising: uneven detecting unit of bus and branch road insulation detecting unit;

The uneven detecting unit of described bus is provided with the testing circuit that is used to detect positive stake resistance of straight-flow system bus and negative stake resistance, described testing circuit is provided with the divider resistance over the ground that resistance equates and be parallel with respectively test resistance, and described divider resistance over the ground by electronic switch according to certain folding order ground connection;

Described branch road insulation detecting unit is used for when the detected positive stake resistance of described testing circuit and/or negative stake resistance reach default alarming value start detection branch road insulation reduction resistance value program; Described branch road insulation detecting unit is provided with the current transformer that is used for the detection branch leakage current, by the output voltage of described current transformer, obtains the size of branch road leakage current, and obtains branch road insulation reduction resistance value.

2. pick-up unit according to claim 1 is characterized in that, also comprises: branch road status information element and main monitoring unit;

The on off state information that described branch road status information element is used for each branch road that will obtain transfers to described main monitoring unit by communication line;

Described main monitoring unit is used to inquire about branch road information.

3. pick-up unit according to claim 2 is characterized in that, also comprises: branch road warning information unit;

The warning information that described branch road warning information unit is used for each branch road that will obtain transfers to described main monitoring unit by communication line.

4. pick-up unit according to claim 2 is characterized in that, also comprises: the background monitoring unit;

Described background monitoring unit is used for the information transmission of the straight-flow system that will obtain by main monitoring unit to remote supervisory and control(ling) equipment.