What are the shortcomings and main problems of conventional secondary systems in conventional substations?

The characteristic of the secondary system of the conventional substation is that the substation adopts the layout form of unit interval, which mainly includes four parts; relay protection, fault recorder, local monitoring and remote control. The devices are relatively independent, lacking overall coordination and functional optimization. , The input information cannot be shared, the wiring is complicated, and the system expansion is complicated. There are five shortcomings:

(1) The safety and reliability are not high: the structure is complicated, and it has no diagnostic ability. It mainly depends on overhaul and refusal to move or malfunction to find the problem.

(2) The protection and control panel covers a large area (increased investment in land acquisition), and the secondary equipment is bulky and heavy.

(3) The power quality is not reliable, and the harmonic incoming line cannot be effectively considered and monitored.

(4) The real-time calculation speed is slow, the controllability is not high, and the running data cannot be provided to the dispatch center in time, and the telemetry and remote signaling information cannot be sent to the dispatch center in real time.

(5) The maintenance workload is large, and the conventional devices are easily affected by the ambient temperature. The setting value of the relay protection must be checked after a power failure.

There are mainly the following specific problems:
(1) Information is not shared. It is roughly divided into system operation information, equipment operation status information, equipment abnormality information, and accident information. Since information is collected from different transformers, the application and processing of information such as measurement and control, protection, fault recorder, etc., as the main link in the application of the secondary system of the substation, belong to different professional management departments, such as relay protection, fault recorder, and local monitoring. And the hardware devices of the remote control part are basically configured according to their functions and run independently.

(2) The hardware equipment of the secondary system has many models and types, which are difficult to achieve standardization and have poor functional flexibility.

(3) The use of a large number of wires, cables and terminal blocks not only increases the investment, but also spends a lot of manpower on the design, wiring, installation, debugging, modification or supplementation of the connections between many devices. The data shows that there are 20-40 outgoing lines in each high-voltage/medium-voltage substation interval.

(4) The conventional secondary system is a passive system. Most of the relay protection, automatic devices, remote control devices, etc. use electromagnetic or small-scale integrated circuits, and the action speed is slow, generally not exceeding 0.02s; it lacks self-check and self-diagnosis capabilities , It cannot normally indicate its own internal failures, so it is necessary to test and verify the equipment functions regularly. This not only increases the maintenance workload, but more importantly, it is impossible to understand the modification status of the system in time and even affect the monitoring and control of the primary system. , And the sensitivity is poor, prone to malfunction and refusal to move.

(5) The remote control function is not perfect, the information provided to the dispatching center is small, the accuracy is poor, and the automatic control and adjustment methods in the substation are incomplete, and the coordination and cooperation force are lacking, so it is difficult to meet the requirements of real-time monitoring and control of the power station.

(6) In the conventional monitoring system, the information is mainly processed by humans, with limited ability. Humans are the core of the entire monitoring system, and the accuracy and reliability of information processing are not high.

(7) Most of them use analog indicator meters. Due to the error between the pointer position and the measured position and the person’s observation position, the accuracy of information processing is not high.

(8) Signal devices mostly use sound and light to indicate the occurrence of events. The specific information is often judged by human experience, which is not conducive to the correct handling of accidents, and it is impossible to conduct a comprehensive assessment of the operation of relay protection and automatic devices.

(9) The used meters, light signs, and position indicators not only consume a lot of power during operation, but also have a larger volume, which makes the area of ​​the control room also large.

(10) The maintenance workload is large. Conventional devices are mostly electromagnetic or transistor types, which are easily affected by temperature. Their fixed values ​​must be checked regularly after power outages. Not only the workload is large, but also remote or rapid modification cannot be achieved.