A kind of on-line monitoring system of monitoring the distribution of AC network DC current
Technical field
The utility model relates to grid monitoring system.Especially a kind of on-line monitoring system of monitoring the distribution of AC network DC current.
Background technology
The features such as D.C. high voltage transmission is because its transmission capacity is large, the low and voltage stabilization of loss, have become the first-selection of present long distance, large capacity transmission.DC transmission system unavoidably can be moved under one pole the earth or bipolar uneven mode, now the electric current having up to several kiloamperes is injected to the earth from direct current grounding pole, cause the existence of electric field in ground, thereby flow through DC current in the transformer of neutral-point solid ground, produce DC magnetic biasing, the safe and stable operation of harm transformer and electric system.Monitor the DC current distribution situation of AC network, can judge exactly the DC magnetic biasing level of transformer, carry out in time early warning, thereby take corresponding measure to suppress magnetic bias direct current.
At present, the DC current monitoring device of AC network has just been monitored the DC current at transformer neutral point place, can not react all sidedly the DC current distribution situation of AC network.Direct current transportation earth current is except flowing to another transformer station from a transformer station by neutral-point solid ground transformer and connected circuit thereof, and the aerial earth wire that connects two transformer station's transmission lines of electricity also can be connected with the grounded screen of two transformer stations.One part of current can flow through from aerial earth wire, and this is by the potential difference (PD) changing between transformer station, thereby the DC current of Transformer Winding is flow through in impact.Therefore in the time analyzing the distribution of AC network DC current, should consider the impact of shaft tower-lightning conducter system.
It is infeasible economically that the DC current of all positions in AC network is monitored.How to pass through the monitoring to part position DC current in electrical network, the DC current distribution situation of reaction AC network, all significant to researching DC distribution of current algorithm and DC magnetic biasing braking measure.
Summary of the invention
The purpose of this utility model is just to overcome the shortcoming and defect that existing AC network DC current monitoring system exists, provide a kind of more excellent mode to monitor the DC current in AC network, it is choose reasonable Hall current sensor mounting points, monitor the DC current flowing through in transformer neutral point place and lightning conducter, in order to not only economy but also react all sidedly the DC current distribution situation of AC network simultaneously.
The on-line monitoring system that monitoring AC network DC current described in the utility model distributes comprises Hall current sensor, DC current monitor controller, for low-pass filter and the A/D converter of pre-process DC current monitor signal, it is characterized in that: described on-line monitoring system also comprises a GPS synchronizing signal module for synchronous DC current signal sampling instant, for DC current data and sampling instant being transferred to the wireless network transmission module of central server database module, Hall current sensor is arranged on lightning conducter and the transformer neutral point place of shaft tower top, the output terminal of Hall current sensor is connected with the input end of low-pass filter, the output terminal of low-pass filter is connected with the signal input part of DC current monitor controller through A/D converter, the output terminal of GPS synchronizing signal module is connected with another signal input part of DC current monitor controller, the signal output part of DC current monitor controller is connected with supervisory control of substation backstage, the signal output part of DC current monitor controller is again by wireless network transmission module and central server database module wireless communication, on the delivery outlet of central server database module, be connected with client PC and cellphone subscriber.
The beneficial effects of the utility model:
1, the selection of DC current monitor controller mounting points is more reasonable, not only economy but also monitor all sidedly the distribution situation of transformer bias direct current;
2, can monitor the DC current flowing through in transformer neutral point place and lightning conducter simultaneously, can more fully react the DC current distribution situation of AC network, can judge exactly transformer DC magnetic bias level, provide in time DC magnetic biasing warning;
3, this on-line monitoring system has the access to netwoks mode of B/S pattern, and client PC can pass through form web page remote access DC current Monitoring Data, facilitates professional and technical personnel realize the demonstration of data and preserve and analyze.
Accompanying drawing explanation
Fig. 1 is the utility model schematic block circuit diagram.In figure, 1. shaft tower, 2. transformer, 3. lightning conducter, 4. Hall current sensor, 5. supervisory control of substation backstage, 6. DC current monitor controller, 7. low-pass filter, 8.A/D converter, 9.GPS synchronizing signal module, 10. wireless network transmission module, 11. central server database module, 12. client PCs, 13. mobile phones.
Embodiment
In conjunction with Fig. 1, the on-line monitoring system that described monitoring AC network DC current distributes, comprise Hall current sensor 4, DC current monitor controller 6, for low-pass filter 7 and the A/D converter 8 of pre-process DC current monitor signal, it is characterized in that: described on-line monitoring system also comprises a GPS synchronizing signal module 9 for synchronous DC current signal sampling instant, for DC current data and sampling instant being transferred to the wireless network transmission module 10 of central server database module 11, Hall current sensor 4 is arranged on lightning conducter 3 and the transformer 2 neutral point places of shaft tower 1 top, the output terminal of Hall current sensor 4 is connected with the input end of low-pass filter 7, the output terminal of low-pass filter 7 is connected with the signal input part of DC current monitor controller 6 through A/D converter 8, the output terminal of GPS synchronizing signal module 9 is connected with another signal input part of DC current monitor controller 6, the signal output part of DC current monitor controller 6 is connected with supervisory control of substation backstage 5, the signal output part of DC current monitor controller 6 is again by wireless network transmission module 10 and central server database module 11 wireless communication, on the delivery outlet of central server database module 11, be connected with client PC 12 and cellphone subscriber 13.
The structure of the utility model AC network DC current on-line monitoring system comprises: the data message of collecting AC network, the DC current distribution situation of initial analysis AC network, build and revise Simulation Calculation, calculate the DC current distribution situation of AC network, determine Hall current sensor mounting points, transmission and processing DC current monitor signal, DC current data are stored in server database module, show DC current data to user, send DC magnetic biasing warning to keeper.
1. the selection of Hall current sensor mounting points
1) collect AC network relevant information, the ultimate principle that enters AC transmission system based on DC transmission system earth current, the DC current distribution situation of initial analysis AC network;
2) based on field road coupling model theory, build and revise Simulation Calculation, the earth current of setting current conversion station earthing pole is this DC transmission engineering rated current, calculates the DC current distribution situation of AC network;
3) if the DC current at transformer neutral point place is greater than 20A, the DC current in lightning conducter is greater than 3A, and Hall current sensor is installed.
4) result of calculation that DC current distributes is arranged from big to small, transformer neutral point place DC current accounts for front 10%, and in lightning conducter, DC current accounts for front 5%, and Hall current sensor is installed;
5), for the transformer that DC magnetic biasing problem occurred, Hall current sensor is installed at its neutral point place.
2. the installation of Hall current sensor
Consider surrounding environment and the mounting condition of Hall current sensor mounting points, at transformer neutral point and lightning conducter downlead appropriate location, Hall current sensor is installed.
3. the background process of DC current monitor signal
1) install after Hall current sensor, DC current monitor signal is processed the conversion with A/D after filtering, and by the sampling instant of the synchronous DC current signal of GPS synchronization module, is then transferred to DC current monitor controller;
2) DC current monitor controller, by wireless network transmission module, is transferred to DC current data and sampling instant in central server database module;
3) Web server takes out DC current data from central server database module, and by form web page by data display to user;
4), if the DC current superscalar data that central server receives is informed keeper with note form, send DC magnetic biasing warning.