Mine low-voltage electricity grid sequential discriminating leakage selecting method and protector
One, technical field:
The invention belongs to electric network fault detection and relay protection, electrical safety field.Relate in particular to the detection method and the protector of the single-phase electric leakage of mine low-voltage electricity grid outgoing (ground connection) fault of isolated neutral.
Two, technical background:
The China's coal-mine underground low-tension network is generally the cable system that isolated neutral adds the zero-sequence reactor compensation, and the earth leakage protection of underground low-tension network almost adopted the low pressure leak detection relay of non-selectivity entirely before 20 years." down-hole is the low-voltage leakage protection device selectively " lists country's " the Seventh Five-Year Plan " tackling of key scientific and technical problems task in the important component part as " research of down-hole leakage protection system and device " problem in 1986; Because this problem difficulty is bigger, classified coal system " eight or five " plan of science and technology in 1991 again as and appropriate special money and continue tackling key problem.The tackling of key scientific and technical problems in continuous ten years has obtained significant results, makes the low pressure choosing of several models such as the domestic KXL of appearance, BJJ leak protective device, is bringing into play vital role aspect the mine safety production.But these low pressure are selected neglected loading to put all to be basically and are adopted zero sequence power direction principle or zero-sequence current phase sensitivity comparison principle to constitute at present.Owing to all contain zero-sequence reactor LK in total leak detection relay (as the JY82 type) of generally installing of underground low-tension network, the zero-sequence reactor LK of this manual adjustments unavoidably because of the variation of power system operating mode or for some reason cut-out supply line the over-compensation state appears; And under the over-compensation state, select neglected loading just to put based on the low pressure of above-mentioned principle of work and enter " dead band ", lose choosing and leak defencive function.Therefore, the choosing of above-mentioned low pressure is leaked protective device in actual applications, or has " dead band ", or the zero-sequence reactor LK (replacing with resistance) always in the leak detection relay, removes compensate function, and the latter to be the 4.2.4 bar that does not meet JB6314-92 stipulate.
The applicant has applied for patent of invention " small current grounding system single-phase grounding selecting method and apparatus " (publication number CN1453916A) according to " the zero-sequence current sequential is differentiated selection method " of oneself invention on April 23rd, 2002, applied for utility model patent " small current grounding system single-phase grounding selecting device " (patent No. ZL02237567.8) on June 10th, 2002, the technical scheme of this device is, comprise with the sequential Discr. being the single-phase grounding selecting module and the sound light alarming circuit of core, peripheral circuits such as faulty line numbering display circuit, the single-phase grounding selecting module is by the sequential Discr., the residual voltage signal circuit, zero sequence current signal circuit and route selection output signal circuit are formed.Differentiate that selection method both can be used for the medium voltage network of 6~35KV though in foregoing invention patent and utility model patent, all mention this sequential, also can use down-hole 380~1140V low pressure isolated neutral system, but in the open scheme of foregoing invention patent and utility model patent, the residual voltage U that selection method is used
0Signal is to take out from the secondary open delta winding of medium voltage network threephase potential transformer PT, this extraction U
0Scheme can not practical application in underground low-tension network because the neutral point of the threephase potential transformer PT of underground low-tension network be do not allow directly grounded.
Three, Fa Ming content
1, application purpose; be on the basis of foregoing invention patent of having declared and utility model patent; the specific condition and the requirement of protection leaked in single-phase electric leakage choosing at the mine low-voltage electricity grid of isolated neutral, invents a kind of " mine low-voltage electricity grid sequential discriminating leakage selecting method and protector ".
2, technical scheme of the present invention is still to keep in the low pressure three phase network under the situation of zero-sequence reactor LK in total leak detection relay, feeds out to connect the circuit from low pressure and goes up the sequential discriminating leakage selecting protector.This choosing is leaked protector and is selected stripping pattern piece and peripheral circuit and residual voltage U by single-phase electric leakage
0, zero-sequence current I
0The formation circuit constitutes.Wherein select the U in the stripping pattern piece
0And I
0Signal processing circuit, sequential Discr., driver are identical with the principle of 6~10KV electrical network single-phase grounding selecting module in the ZL02237567.8 patent.This choosing is leaked protector and is characterised in that:
(1), residual voltage U
0Signal is that the neutral point from three-phase reactor SK takes out the capacitance-resistance bleeder circuit over the ground, enters and selects the stripping pattern piece.The structure of capacitance-resistance bleeder circuit is successively through resistance R 1, capacitor C, resistance R 2 ground connection, to take out residual voltage U from three-phase reactor SK neutral point again from the R2 two ends
0The stripping pattern piece is selected in access.
(2), select the sequential Discr. in the stripping pattern piece to constitute by a slice application-specific integrated circuit ASIC, only single-phase electric leakage (ground connection) fault of 1 tunnel (or 2~4 tunnel) low-voltage cable is guarded, realize protection selectively.Guard 1 tunnel protector and be applicable in the low-voltage explosion-proof feeding switch, the protector of monitoring 2~4 tunnel is applicable in the low-voltage distribution panel (cabinet).
3, good effect
At first, adopt sequential discriminating principle to select leakage, having solved underground low-tension network choosing leakage protection does not have the problem that " dead band " need not remove zero-sequence reactor LK again.And time sequence logical discrimination has the phase shift range (active region) of 0~170 degree, thereby guaranteed the sequential discriminating leakage selecting protector at uncompensated, the under-compensation of underground low-tension network, entirely under compensation and the over-compensation various running statuses, can both operate as normal, and reliably protecting.
Secondly; the sequential discriminating leakage selecting protector adopts ultra-large special IC (ASIC) to leak the CPU of protector as choosing; this leaks the rugged surroundings that protection adapts to down-hole, exploiting field more than the choosing of adopting middle small scale integrated circuit or single-chip microcomputer to constitute, helps being used in the flame-proof type switchgear.
4, description of drawings: Fig. 1 is the circuit diagram of protector of the present invention, and the embodiment among the figure is to be example to protect one tunnel low pressure outgoing, and it is applicable in the downhole anti-explosion type low-voltage feeder switch.
Four, specific embodiments
As shown in Figure 1, it comprises that single-phase electric leakage selects stripping pattern piece and peripheral circuit, and selecting in the stripping pattern piece has U
0Circuit and I
0Circuit, sequential Discr. and output driving circuit.Select the U in the stripping pattern piece
0Signal processing circuit and I
0Signal processing circuit, the relevant circuit in the same utility model patent (ZL02237567.8) is identical, and sequential differentiates that principle is also identical.Leak protector because of the choosing that is used for feeding switch and only need guard one road outgoing, so the sequential Discr. is only used a slice ASIC.The sequential Discr. has three tunnel outputs, connects peripheral circuit through driver respectively, and peripheral circuit has audible alarm circuit, the LED indicating circuit of leak current fault circuit and the trip circuit of leak current fault circuit.
Zero sequence current signal takes out from the Secondary Winding of zero sequence current mutual inductor, after resistance R i carries out the I/U conversion, with this I
0Signal is sent into single-phase electric leakage and is selected the stripping pattern piece; The residual voltage signal successively through resistance R 1, capacitor C and resistance R 2 ground connection, takes out required U by the R2 two ends by the neutral point of three-phase reactor SK
0Signal is directly sent into single-phase electric leakage and is selected the stripping pattern piece.