Based on the current differential protection system of PON communication
Technical field
The present invention relates to a kind of current differential protection system based on PON communication, for extend current differential protection of ac transmission medium, to expand current differential protection range of application, belong to field of relay protection in power.
Background technology
Power distribution network configures rational relay protection device and is conducive to isolated fault rapidly and accurately, improves power supply quality.Under current distribution feeder troubleshooting pattern is generally based upon the prerequisite of power distribution network radiativity network, adopt stage overcurrent protection or with feeder automation (FA) compound mode.Along with the continuous propelling of intelligent grid, a large amount of distributed power source access power distribution network, make power distribution network become many power supplys complex network from single supply is radial, the conventional failure process originally based on radiativity network is more and more difficult to the requirement meeting intelligent distribution network self-healing.
Current differential protection is widely used in transmission line due to its superior quick-action, sensitivity and selectivity.Realize Line Current Differential Protection and need sampled analog amount (Sample Value between circuit both sides; be called for short SV) exchange fast, reliably; existing method adopts dedicated optic fiber channel or realizes based on the multiplex channel of SDH/PDH technology; but at power distribution network erection special optic fibre or SDH/PDH communication apparatus, exist costly and the defect such as communication speed is slow.
Ethernet passive optical network (EPON) has the advantages such as high bandwidth, low cost, easy care because of it and becomes one of Modern power distribution automation communication main way, and therefore multiplexing EPON communication network is the ideal chose realizing distribution feeder differential protection.
In view of this, the present inventor studies this, and develop a kind of current differential protection system based on PON communication specially, this case produces thus.
Summary of the invention
The object of this invention is to provide a kind of current differential protection system based on PON communication; overcome the slow shortcoming costly of Conventional communication mode speed; solve synchronous and PON transmission jitter problem, in conjunction with ratio differential protection philosophy, expand the range of application of differential protection.
To achieve these goals, solution of the present invention is:
Based on the current differential protection system of PON communication, comprise differential protection, PON and IEEE1588 V2 clock; Described PON comprises OLT, ONU, optical splitter, and wherein OLT is positioned at transformer station, and optical splitter, ONU are arranged on each block switch place of distribution network feeder, and OLT, optical splitter, ONU are connected by single-core fiber; Described differential protection exchanges the current transformer at plug-in unit connection segment switch place, and communication plug-in unit connects ONU; The upper united mouth of the OLN terminal of IEEE1588 V2 clock access PON.
In such scheme, described PON refers to EPON or GPON, supports IEEE1588 V2 agreement; Described OLT, ONU are set to boundary clock or transparent clock, and described differential protection is set to from clock.
The above-mentioned current differential protection system based on PON communication; differential protection is connected to the ONU unit terminal of PON; clock source device is connected to the upper united mouth of the OLT terminal of PON; the current sampling data adopting the frame format of IEC61850-9-2 agreement to be realized between differential protection by PON is exchanged; and then calculating differential current and stalling current, a situation arises for failure judgement.Differential protection is transplanted in PON; overcome the slow shortcoming costly of Conventional communication mode speed, solve synchronous and PON transmission jitter problem, in conjunction with ratio differential protection philosophy; expand the range of application of differential protection, described current differential protection system is particularly useful for power distribution network.
Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.
Accompanying drawing explanation
Fig. 1 is the current differential system schematic based on PON communication of the present embodiment;
Fig. 2 is the differential protection actual measurement action plane figure of the present embodiment.
Embodiment
A kind of current differential protection system schematic based on PON communication that Fig. 1 provides for the embodiment of the present invention, at distribution network feeder each block switch, differential protection is set, the current transformer (CT) at the interchange plug-in unit connection segment switch place of differential protection, communication plug-in unit connects ONU equipment; PON system comprises OLT, optical splitter, ONU, and wherein OLT is positioned at transformer station, and optical splitter, ONU are arranged on each block switch place of distribution network feeder, and OLT, optical splitter, ONU are connected by single-core fiber; The upper united mouth of the OLN terminal of IEEE1588 V2 clock source access PON, OLT terminal, ONU unit terminal are set to boundary clock or transparent clock, and differential protection is set to from clock;
The operation principle of the above-mentioned current differential protection system based on PON communication: IEEE1588 V2 clock source transmission sync message to all differential protections, realizes differential protection sample-synchronous through PON; Differential protection gathers the three-phase current sampled data (SV) at block switch place, and sends to adjacent differential protective device with IEC61850-9-2 protocol frame format by PON; Differential protection receives the SV of adjacent differential protective device, shaking the impact brought, arranging a sampled data buffer queue in differential protection to overcome network delay, and queue length L meets
, wherein
for maximum network delay jitter, unit ms,
get 2 ms ~ 10ms,
for protection sample rate.Differential protection sampled data buffer queue is used for storing the SV of the offside differential protection received; once set up communication link with offside differential protection after differential protection powers on; wait for that SV just opens differential protection after filling up sampled data buffer queue; interrupt taking out offside SV from sampled data buffer queue head afterwards each time participate in differential protection computing with this side SV in corresponding moment and delete queue head SV; the one or more SV newly received for this interruption insert queue tail in order, then do not insert as do not received offside SV.Formula (1) operation equation is finally adopted to judge whether generating region internal fault:
(1)
In formula,
,
,
for circuit each side electric current phasor,
for differential current value,
for braking current value,
for differential protection minimum movements threshold value,
for proportional brake coefficient.
Fig. 2 is differential protection actual measurement action plane figure, and test result shows, the differential protection based on EPON communication can precision maneuver, and everything point all can meet required precision.
Above-described embodiment and graphic and non-limiting product form of the present invention and style, any person of an ordinary skill in the technical field, to its suitable change done or modification, all should be considered as not departing from patent category of the present invention.