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In the process of collecting telecontrol information (including remote signaling and microcomputer protection messages), the substation RTU device has the phenomenon of abnormal transmission, missed transmission and micro-computer protection message abnormality and loss. The article has detailed the reasons for its occurrence. The analysis of the ground and the corresponding improvement measures are put forward. According to the maintenance practice, these measures have effectively improved the accuracy of the contact amount remote signal and the microcomputer protection message, which is effective.
With the extensive use of microcomputer protection and automatic devices, in the power grid dispatching automation system, the microcomputer protection message and the contact amount are the same as the remote signal, which has become an important part of the telecontrol event information.
The remote signal reflects the actual operating state of the substation equipment, and the dispatcher uses this as a basis to remotely operate the switch. The microcomputer protection message reflects the protection action and self-diagnosis information of the microcomputer device, and both of them are indispensable and complement each other.
Therefore, the telecontrol system accurately reflects the operating status of the substation and correctly analyzes the accident. It is necessary to reduce the occurrence of error event information as much as possible, including: reducing false alarms, leaking, reducing computer error, missing, and improving equipment resistance. Interference ability, etc.
I. Analysis and improvement of the reasons for mis-transfer
In the telecontrol system, the contact amount remote signal is connected to the RTU device by the passive empty contact of the device, and generally includes the switch quantity of the circuit breaker, the exit signal of the electromagnetic relay protection device, the abnormal alarm signal and the non-electrical quantity remote signal. After analysis, it is believed that there are several reasons for the wrong amount of contacts.
1. The low voltage of the remote signal leads to the error
In the initial stage of the telecontrol system, the acquisition voltage of the remote signal loop is 24V DC. After a period of operation, the following deficiencies are manifested:
(1) Poor anti-interference ability of remote signal
Since a large number of secondary telecom cables used in the reconstruction of old stations do not have a shielding layer, when the equipment is in a strong electric or magnetic field operating environment, a strong interference signal (amplitude greater than 24V) is induced on the signal loop, which causes a misunderstanding. letter. In a substation accident environment, the probability of loop sensing causing interference is greater.
(2) The working voltage of the relay contact (220V) does not match the working voltage of the remote signal. When the contact is oxidized or the contact is poor, the contact resistance of the contact increases. If the DC 24V voltage does not break through the oxide layer, the remote signal displacement cannot be reflected.
Therefore, in the subsequent automation transformation and engineering began to use the shielded control cable, and the remote signal voltage from DC 24V to DC 220V, for the running RTU equipment, can use a DC 220V signal conversion terminal board, will The DC 220V is stepped down to 24V DC and is optically isolated. This can reduce the error of the remote contact due to the increase in contact resistance of the contacts, while reducing the interference of strong electromagnetic fields.
2. The second system itself caused the mis-transmission. Because some unattended substations were rebuilt on the basis of the original manned substation, some of the original secondary system and the unstable operation of the equipment caused a certain amount of misunderstanding. letter.
(1) Loss of remote contact caused by relay momentary contact When the remote control of the old station is changed, the DX-4A/4XX series signal relay 2 is connected to the “returning unreturned†signal loop and the central signal light word respectively. brand. The remote contact can only use the momentary contact as a remote source.
In actual operation, we found that the momentary contact is not suitable as the remote signal output. The main reasons are as follows: (1) The remote signal uses both the constant motion and the momentary contact, which is not conducive to the dispatcher to correctly grasp the operating state of the system, and it is easy to make a wrong judgment. , the instantaneous contact remote signal error is regarded as the remote signal jitter; (2) because the RTU device's remote signal debounce delay can not be separately set and the instantaneous contact oxidation and other factors interfere, access to the instantaneous contact The loss of remote signal is more serious.
(2) Circuit breaker equipment auxiliary contact work abnormal circuit breaker switch remote signal, generally taken from the auxiliary contact of the operating mechanism, when the circuit breaker operates a certain number of times, the mechanical transmission part of the auxiliary contact may have a gap; The vibration may cause poor contact or misalignment of the auxiliary contacts; oxidation of the surface of the auxiliary contacts may also cause poor contact, which may cause it to break when it is in contact. All three of the above reasons may cause mis-movement, refusal or frequent jitter of the remote signal.
In addition, the misoperation of the auxiliary gas density relay of some models of 110kV SF6 switch is serious, resulting in "low SF6 pressure", frequent mis-transmission of mis-transmission, and the frequency of mis-delivery can reach 28 times/h in the most serious case.
(3) Remote resetting leads to remote signal jitter When the unmanned substation central signal is dropped, the dispatcher sometimes needs to remotely reset the central signal. When the dispatcher confirms that the signal from the substation is reset to the central signal loop of the station, all the signal relay return coils in the station are energized. The DX-4A/4XX series signal relay belongs to the electromagnetic decoupling type mechanical structure. When the return coil is normal, it is not charged. When it is energized, it will return to the relay. The coil action may cause the contact to malfunction and misinterpret. In response to the above phenomenon, we have strengthened communication with the maintenance department and assisted in the corresponding improvement of the secondary system.
Gradually replace the DX-4A/4XX series signal relays with the same series of relays with 3 pairs of normally moving contacts, and cancel the momentary contact as a remote source.
The auxiliary gas density relay with frequent misoperation and the signal relay that is malfunctioning when the central signal is reset by the remote control are found in time and replaced.
Clear responsibility for signal contact maintenance, strengthen maintenance of relay contacts and circuit breaker auxiliary contacts, and ensure reliable displacement of remote signals.
Second, the analysis of the micro-computer protection error message and the improvement of the micro-computer protection and RTU serial communication, is a new technology, therefore, there must be some shortcomings, which need constant improvement and innovation.
(1) Microcomputer protection design has defects
There is a serious design flaw in the communication manager protected by a certain model. When accessing the event printer, communication with the RTU is very easy to crash, requiring frequent restarts by the operating personnel.
Some microcomputer protections have a "control loop disconnection" signal when the switch is opened and closed. The reason is that when the switch is displaced, the time difference of the auxiliary contact switching causes the closing position relay (KCC) and the trip position relay (KCT) to instantaneously lose power, resulting in a false transmission of the "control circuit disconnection" signal.
The protection device does not provide a soft switch for sending each message, so that maintenance personnel can set it according to the actual operation and filter out the useless messages. A secondary message such as "fan start" can be filtered completely, avoiding a large number of secondary messages flowing into the dispatching system, affecting the normal operation of the SCA2DA system operation and dispatcher.
(2) RTU lacks effective monitoring of protection communication. Microcomputer protection sends correct messages to the dispatching SCADA system. It must ensure the normal operation of the communication link. It contains: (1) between the communication manager and the screen microcomputer protection. And downlink communication; (2) uplink and downlink communication between the RTU and the communication manager of each screen.
When the upstream channel is faulty, the protection packet cannot be sent to the dispatcher. When the downlink channel is unreachable, because the microcomputer protection device cannot accept the RTU timing, the protection action time parameter in the packet is incorrect, and the remote signal displacement time of the corresponding switch cannot be corresponding.
Therefore, the RTU device should be able to fully monitor the operational status of the communication link and send corresponding information to the dispatch SCADA system.
A group of early microcomputer-operated microcomputer protection devices in Shandong Lijin Bureau, because the communication manager can not count the communication status of the microcomputer protection in this screen and upload the RTU, the telecontrol system cannot monitor the entire communication link, especially the microcomputer protection device. Surveillance. On September 25, 2000, the F11 microcomputer protection of Lijin Station failed, but the dispatching system did not receive the signal. Fortunately, the personnel of the running class inspection station found it in time to avoid the protection of the leapfrog accident.
(3) Improvement measures For the above deficiencies and shortcomings, it is necessary to carry out the following measures:
1 pay attention to the scientific selection of equipment and after-sales service
In the selection, pay attention to the operational reliability of the microcomputer protection equipment, and the communication and data interface stability and perfection of the telecontrol equipment (the station end RTU and the substation automation system), especially the implementation of the communication port status of the station end equipment. Surveillance. At present, the manufacturers of microcomputer protection devices are fiercely competitive, the products are updated quickly, and the flow of personnel is frequent. Therefore, it is also important to require manufacturers to provide long-term technical support and spare parts replacement.
2 Improvement and improvement of equipment in operation For the equipment in operation, the manufacturer should be urged to improve in time. For example, under the active improvement of the manufacturer, ISA-1H protection has solved the defect of false transmission of "control loop disconnection" and provided a soft switch for "control loop disconnection" message transmission. If some defects cannot be solved in a short period of time, other measures must be taken to ensure that the automation system cannot monitor the operation of the protection device. We specifically access a pair of contacts that reflect the protection operation status to the RTU. Protect the monitoring of operational status.
In addition to the above factors, the design of the RTU device is also important for stable operation. Through the continuous development of computer technology in recent years and the continuous suggestions from users, the RTU performance of new models installed and put into operation has made great progress, mainly in:
The system is powerful, with dual master control automatic switching, CANBUS communication between each module, compared with single host, the early products using serial bus, the reliability has been significantly improved;
Each remote signal point can be personalized with delay and debounce settings, and has strong adaptability to each type of contact switch;
The communication support with the microcomputer protection is perfect, the serial port is more, and the function is powerful.
4. Enhancing the function of SCADA system to process protection messages With the rapid development of microcomputer protection, the SCADA system needs to further strengthen and improve the intelligent processing capability of PC protection packets, such as increasing the classification processing of protection packets and shielding specific devices. The means of the message to shield a large number of secondary messages like "fan start".
3. Conclusion In summary, the accurate collection of telecontrol event information depends on the information source (electromagnetic protection device and microcomputer protection and automatic device), the reliable operation of the RTU device, the good matching of the remote device and the secondary device, and the function. Continuous improvement and expansion.
Through the above-mentioned improvement and improvement of the telecontrol system, the accuracy of the remote signal and microcomputer protection operation of the telecontrol system of the North District Power Supply Bureau has been greatly improved, greatly reducing the work intensity of the substation and dispatching operators.
At present, with more and more new technologies put into use, substation construction has been designed and constructed in accordance with comprehensive automation standards, thus putting forward higher requirements for the accurate collection of information, and at the same time, the majority of telecontrol and relay protection The staff raised higher requirements. Therefore, we constantly improve the level of professional technology to ensure the real and reliable realization of power system automation.
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