Automatic Grid Scheduling System

Automatic Grid Scheduling System

Backbone Network Architecture

Power Communication features
With the continuous development of modern power, new features and requirements of power communication have emerged:

1. As the scheduling automation of the power grid system, four remote signals, and the increase of unattended substations require stable operation of communication equipment, and the system can transmit information between them in a highly reliable manner.

2. As the power business grows and the power management needs to modernize, the system's networking capacity needs to be large, the resizing needs to be convenient, and the information of devices on various sites needs to be convenient.

3. Due to the complex signal in power communication, the transmission equipment must have multiple interfaces to ensure smooth delivery of control information and feedback information.

4. In the power system, the communication and maintenance power is relatively weak. Therefore, high equipment reliability, stable operation, and easy maintenance are required.

5. Power Communication will develop towards integrated digital network (ISDN) and require the entire network to be connected to other large networks. This requires that the equipment be technically advanced and adaptable.

Channel Scheme Design
Based on the above features, the Power Grid Scheduling Automation System is designed to take into account other systems for power communication channels.

Channel requirements of existing systems
. Automatic Grid Scheduling System: consists of the Main Station System and RTU system. Data is transmitted in RS232 mode. The data exchange rate between an RTU and the main station is generally much lower than 32 Kbps, the data exchange between the master station and the RTU adopts the primary backup mode to improve the system reliability;

. The data of the electricity bill management system is generally transmitted over Ethernet or switched over a dial-up line. The data is stored in the central database, and the existing database query system frequently exchanges data on the route, therefore, the data traffic requirements are high;

. The data exchange volume of financial, personnel, and material systems is relatively limited. Generally, the data exchange volume is based on Ethernet.

Systems to be considered
. Image Monitoring System: the quality of the system is directly related to the transmission channel. Generally, data transmission is based on TCP/IP protocol. for different data traffic requirements on image quality, you can select a data channel of 64-2 MB;

. MIS System: data transmission is based on TCP/IP protocol. The data transmission volume is large and the system is complex. Generally, the data exchange volume is in MB;

. Internet/Intranet systems: data transmission is based on the TCP/IP protocol. The data transmission volume is large. Generally, the internal data exchange volume ranges from megabytes to dozens of megabytes, and the inter-network data exchange volume ranges from megabytes.

Channel technical status
The widely used and mature channel technologies in domestic power systems are as follows:

Optical Fiber Technology: it will be widely used in the future. Its main features include: high speed, providing bandwidth of more than mbps-1gbps; reliable communication, good security; long transmission distance, high overall cost effectiveness. Various interfaces required by users are provided through various optical terminals. Common interfaces include the traffic port, RS232 port, rs422/485 port, E1 port, and even standard image interface and Ethernet port. The widely used optical end machines in China include UMC series optical end machines, OTN series optical end machines, and omux series optical end machines.

Audio Technology: it is a traditional communication method. Compared with the optical fiber technology, it has the following main features: Low Cost of end devices, good maintainability and easy to understand. However, there are some disadvantages: long-distance communication requires relay, and the communication capacity is small, poor lightning protection performance.

Carrier Technology: power carrier communication is a unique communication method for power systems. It uses power lines as the carrier, substations as the terminal, and the carrier is mounted at both ends of the power line. It has the advantages of long communication distance, close equipment to the user, high reliability, and simple engineering construction. Compared with digital communication, digital communication usually requires a wide band and a high signal-to-noise ratio. Typical carrier devices in China include zdd series power line load generators, SNC series power line load generators, and CZ series Programmable power load generators.

Spread Spectrum Technology: it is a highly reliable and confidential military radio communication technology generated during World War II. It can be used in civil commerce since 1985. It features strong anti-interference performance, low-power operation, code division multiple access, and precise location and timing. Spread-Spectrum communication is used to transmit data, voice, and image from point to point and point to multiple points. The transmission distance can reach 50 km without relay. The combination of Spread Spectrum Communication and wireless access networks can form a new spread spectrum Wireless User loop, greatly expanding its application scope. Widely used Spread Spectrum Systems in China include DTS series spread spectrum microwave systems and utilicom wireless Spread Spectrum Systems.

Digital Data Network (DDN): digital data network. A digital circuit consists of optical fiber cables. It is a digital data circuit management and distribution network composed of digital circuit management and distribution devices (DDN devices. Compared with traditional telecom networks, DDN provides users with a large data communication platform with full digital, high-speed, and flexible switching and reuse functions. Its Notable features include large scale, wide coverage, large port capacity, high communication rate, support for many communication procedures, strong processing functions, and low network latency. Generally, DDN provides users with standard interfaces V.24 or V.35 based on their needs. The DDN Telecommunications Department provides DDN Services to users through the digital circuit Leasing Service, typical channel bandwidth: 9.6 K/19.2 K/64 K/128 K/256 k/384 K/521 K/768 K/1 m/2 m.

Integrated Service Digital Network (ISDN): Full name: Integrated Services Digital Network. It is a communication network developed based on a comprehensive digital telephone network that provides point-to-point digital connections to support various services including voice and non-voice. The following features: the integration of communication services enables a single user line to provide telephone, fax, visual text and text, data communication, and other services, while reducing communication costs and improving the communication quality; easy to use. The commonly used channel bandwidth is 64 K/128 K. So far, the Post and Telecommunications ISDN service is increasing its coverage.

Frame Relay: A broadband data business standard evolved from the X.25 group exchange technology. Frame Relay consists of frame relay access devices (frad), Frame Relay switching devices, and public Frame Relay services. Its features are as follows: simplifying network functions, improving network performance, and reducing network interconnection costs; not only low network latency, low communication costs, but also the use of international standards, so that products of multiple manufacturers are compatible with each other. A common method is to use frame relay for LAN interconnection.

Communication Method Selection
According to the above analysis, the optical fiber technology has obvious advantages over audio cable, carrier technology and Spread Spectrum Technology: large communication capacity, high communication quality, and good lightning protection performance.

The capacity of optical fiber communication networks can easily be expanded to more than MB, while communication networks composed of audio cables, carrier technology and spread spectrum technology are difficult to achieve high communication capacity, generally, it can be at most MB. Therefore, it is difficult to make full use of the performance of the electric management system, and it is even less likely to meet the communication capacity requirements of the MIS system, substation Image Monitoring System, and enterprise intranet. Therefore, we believe that optical fiber communication technology should be given priority when geographical factors and economic conditions permit.

In the scheduling automation channel planning of the ** Power Supply Bureau, we mainly adopt the optical fiber communication technology.

Optical terminal equipment and quotation
According to the actual situation of the Ruian Bureau, fiber optic channels consider optical fiber networks based on SDH systems. The devices use umc2000 halo devices. The features of this equipment are: a high-reliability large-scale transmission system can be established to form a self-healing Ring Network, it has the network management function and is easy to maintain.

The channel construction of the scheduling automation system is divided into two steps: the first step is to establish the channel based on the four remote functions; the second step is to plan and build the channel based on the fifth remote function of the substation (image monitoring.

The main site software system is required to have the following functions:
Software System
User-friendly and easy-to-use: user-friendly and easy-to-use interfaces are the basic requirements of a mature software system. This guarantees the full use of system functions.
System openness: subsystems are open and the foundation for establishing a management network with superior performance.
A certain degree of scalability and strong secondary development capabilities: With scalability and powerful secondary development tools, users can customize system functions according to their own requirements, is the guarantee of system life.
Data collection
Collect all the measurement quantities and semaphores transmitted by the RTU of each substation.

Data Processing
Total active and reactive power over the network plus Σ p and Σ Q.
The measurement of active and reactive power in the power grid is based on Σ kWh and Σ kvarh.
Use the integral method to calculate the soft current of the entire network and the specified point.
Power billing function.
CRT screen display and operation functions
Displays the real-time network diagram of the power system.
Displays the Real-Time Main Wiring Diagram of each substation.
Displays the real-time operation parameters of each substation.
Displays the total power and power consumption.
Displays the total power addition and voltage variation curves, including the planned value and actual value.
Displays out-of-limits and accident alarms for running parameters.
Displays the voltage bar chart.
Displays historical data.
Send remote control and remote control commands.
Edit a graphical report online.
Modify historical data online.
Data storage and Event Recording
Timed storage operation parameters (optional for a storage period of 5 minutes or one hour ).
Event Sequence record.
The time limit and the time limit are recorded.
Operation Records.
RePort Printing
Print the daily and monthly scheduling operation reports of the entire grid system.
Print the sequence of events (SOE), displacement records, limits and Operation Records.
Print the curve of total power addition and voltage variation.
Screen.
Analog Screen Display
Displays the actual location of the circuit breaker and isolating switch.
In case of an accident, the circuit breaker's displacement signal is displayed first, and no corresponding signal is sent, and an audible alarm is reported.
Major telemetry and trend.
Total network power addition and system frequency.
Date, clock, and security day.
Data Transmission
The main site can be 1 ~ 64 RTUs for duplex data transmission.
The main site schedules and forwards the required data to the region and receives the power usage instructions issued by the Regional scheduling.
The communication protocol uses a ministerial protocol (CDT or polling ).
The main site provides statistics and display of the channel error rate.
Remote Control
Remote control circuit breaker.
Remotely adjusts the shunt of the load regulator transformer.
Remote motion information
The substation sends the following telemetry to the dispatch center:
The active power, current, and active power of the 110kv transmission line.
The active power, current, and active power of 35 kV transmission lines.
The active power, current, and active power of 10 kV transmission lines.
Active Power and current of the main variable.
Bus bypass, bus connection, segmentation, branch circuit breaker current.
10 ~ Voltage of the 110kv system voltage monitoring point.
The reactive power and current of the capacitor group.
DC bus voltage.
The substation sends the following remote signals to the scheduling center:
Total substation Accident signal.
The circuit breaker position signal of the substation.
Reflects the isolated switch position signal of the running mode.
Total Circuit Breaker Trip Signal.
Low-cycle Load Reduction signal.
10 ~ Ground signal of 35kv system.
DC system grounding signal.
Overall fault signal of relay protection, voltage regulator, and fault recorder.
Control methods include signals from remote control to local control.
Total disconnection signal of the Circuit Breaker Control Circuit.
Total fault signal of circuit breaker operating mechanism.
Main variable and heavy gas, differential protection, and Compound Voltage and Current locking operation signal.
Transformer Temperature too high alarm signal.
Light Gas action signal.
The main protection (distance, zero-sequence protection, etc.) of the 110kv line and the Action signal of the line coincidence gate.
35 kV lines are mainly protected (fast-breaking, over-current, distance protection, etc.) and overlapping brake action signals.
The main 10 kV line protection (such as high-speed disconnection and over-current protection) and the switching signal.
Main protection signals of bus bypass, bus connection, segmentation, and branch circuit breaker.
Line distance protection locking signal.
Signal of remote control power loss of the remote control terminal.
The downlink channel fault signal of the remote terminal.
The gate opens.
Fire alarm signal.
The dispatch center sends the following remote control and remote control commands to the substation:
Circuit Breaker combination.
Adjust the tap position of the On-Load Voltage Regulator transformer.
Returns the predicted signal.
Distance Protection locks recovery.
Return of the signal relay.
　

Remote device
The remote terminal must meet the following conditions:

It meets the requirements of remote information collection and transmission, and features good performance and reliable operation.
A site uses a remote terminal.
Easy to install and easy to maintain.
Meet a variety of communication protocols (CDT, polling, csc8890, sc1801, MB-88 and other communication protocols ).
It can measure three-phase voltage, current, active and reactive power, apparent and active power, reactive power, power factor, and frequency.
Convenient extension of remote communication, telemetry, and remote control.
The ambient temperature of the device can meet the requirements of the substation, and there are measures to prevent lightning strikes and overvoltage.
The device has the ability to resist electromagnetic interference. The signal input has a reliable electrical distance and the insulation level complies with relevant standards.
The main technical indicators should meet the following standards:
Telemetry precision: 0.5.
The resolution of Event Sequence records is no greater than 10 ms.
Remote control output: passive contact mode. The contact capacity is DC 220 V, 5a, 110 V, 5A or 24 V, 1a (microcomputer protection, etc ).
The main power supply of the device is AC 220 V, and the standby power supply is DC 110 V or v.