Abstract: This paper introduces the application of S7-200PLC in AC switchboard used in substation. The composition, function and characteristics of the system are emphatically expounded; since the system has been running, all functions have been normal, and the equipment has been running stably, fully meeting the design requirements.
Keywords: S7-200PLC, substation, switchboard
The 110kV Guanshui Substation of Guiyang Nanming Power Supply Bureau is the main power supply station in Nanming District, Guiyang City. The stability and reliability of the operation of the switchboard in the substation directly affects the power supply to most of the production and life in the entire district. The original switchboard system has simple functions and automatic The level is not high and the control method is backward, which brings many changes to the power supply bureau to realize unattended substation and distribution network automation, and cannot always guarantee the power quality of urban power grid power supply. Therefore, in May 2005, the switchboard was renovated. Siemens’ S7-200PLC was used as the control center, and the TP270 was used as the monitoring operation center. Other distribution equipment and monitoring equipment were made by well-known foreign manufacturers.
The new switchboard monitors the power supply of the transformers in No. 1 and No. 2 substations through the voltage monitoring module, and the ATS switch (Automatic Transfer Switch) is controlled by the PLC to perform automatic switching and mutual switching operations. A variety of power parameters are monitored to ensure the stable operation of each auxiliary system of the substation. The operation, operation and power parameters of all devices are reflected and recorded on the TP270 through PLC, and various signals are transmitted to the power supply through RS-485 or LAN. Dispatching center and centralized control center for timely power supply dispatching and equipment maintenance.
The 224XP-CPU, TP270 man-machine interface, EM221 digital input module, EM222 digital output module and CP243-1 Ethernet communication module of Siemens were used in the equipment transformation.

Figure 1 Corporate photo

Figure 2 System structure diagram

Table 1 System configuration table

Figure 3 Screen in the application

The power distribution board (intelligent power distribution panel) used in substation stations after the application of S7-200PLC upgrade has changed the previous problems such as troublesome power data collection, single operation mode, and manual operation on site. Now in addition to retaining the necessary manual operation mode, according to the operation mode PLC can control the ATS switch to switch arbitrarily to run on power supply I or II. When the power supply line loses voltage, the other power supply line can be reliably switched on or restored, and remote operation can be performed at the same time, which solves the problem of current ATS product control switching. Inaccurate, single operation mode and remote control problems. There are various electric energy meters on the power distribution board before the transformation. Now only one multi-function instrument can complete the monitoring, acquisition and data analysis of various electric energy parameters such as voltage, current, frequency, active power, reactive power, etc., as well as harmonics. Analysis, analog and alarm output functions. The station power distribution panel can also monitor the current and working status of each feeder circuit. Any action, operation and fault alarm of the entire power distribution panel are displayed in time and stored on the TP270. These data can be transmitted to the nearby through the MODBUS bus. The control center can also transmit data to the dispatch center several kilometers away through the Ethernet for better operation, maintenance and management.
The biggest problem in the design process is how to read the data of the smart instrument to the TP270 through S7-200PLC. The smart instrument in this system uses the MODBUS_RUT protocol, which can only be used as a slave station, that is to say, S7-200PLC must be used as the master station to read the data of the instrument. In the current data, only S7-200PLC is used as a MODBUS slave station. If you want S7-200PLC to be the master station, you can only write the program that uses the free port as the MODBUS master station. Because the instrument provides a lot of data and the data addresses are scattered, and it is required to be refreshed every second, it is necessary to do the data. CRC check, it is difficult to write such a communication program. If the program is written one by one, the program will be too long, which will affect the total cycle time. Not only can it not be refreshed every second, it may also cause the port Send, receive conflict and CRC check error, after repeated research and experiment, and finally adopt the method of polling the address with the counter in the program, thus reducing the program amount and the total cycle time. Part of the program is as follows: (The main function of OB1 is to initialize the port as a free port, initialize the data format of sending and receiving, set the polling time, polling and disconnect the connection; SBR5 and SBR6 do the CRC check of the sent and received data, CRC check Mainly through byte XOR cycle, shift cycle and formula XOR to do the CRC check of the transmitted data; interrupt 1 is the received data; interrupt 2 verifies the received CRC check result)
OB1
LD SM0.1 initialization port
MOVB 16#09, SMB30
MOVB 16#9C, SMB87
MOVW +150, SMW92
MOVW +0, SMW90
MOVB 50, SMB94
LD SM0.1 Initialize send data
MOVB 16#08, VB2100
MOVB 16#05, VB2101
MOVB 16#03, VB2102
MOVB 16#03, VB2103
MOVB 16#0, VB2104
MOVB 16#0, VB2105
MOVB 16#02, VB2106
LD SM0.1 Initialize receive data
MOVB 16#09, VB1200
MOVB 16#05, VB1201
MOVB 16#03, VB1202
MOVB 16#04, VB1203
LD SM0.0 Set the polling time
AN T96
TON T32, +150
LD SM0.0
A T32
TON T96, +150
LD T32
EU
LD C1
CTU C1, 16#10
LD SM0.0
AW= 16#0, C1
EU
MOVW 16#0300, VW2103 Send polling data
CALL CRC: SBR5
XMT VB2100, 0
LD SM0.0
AW= 16#1, C1
EU
MOVW 16#0302, VW2103
CALL CRC: SBR5
XMT VB2100, 0
LD SM0.0
AW= 16#02, C1
EU
MOVW 16#0304, VW2103
CALL CRC: SBR5
XMT VB2100, 0
…………
LD SM0.7 Disconnect
ATCH INT_0:INT0, 9
ATCH INT_1:INT1, 23
ENI

SRB6 (SBR5 is the same as SBR6)
LD Always_On:SM0.0 Read data length, initialize CRC word
MOVB VB1200, VB1301
MOVW VW1300, VW1302
-I 16#02, VW1302
MOVW 16#FFFF, VW1306
MOVD &VB1200, VD1400
FOR VW1304, 16#1, VW1302
LD Always_On:SM0.0 byte XOR cycle
+D 16#1, VD1400
MOVB *VD1400, VB1410
XORB VB1410, VB1307
FOR VW1310, 16#1, 16#08
LD Always_On:SM0.0 Shift Cycle
MOVW VW1306, VW1420
SRW VW1306, 1
LD SM1.1 Formula XOR
XORW 16#A001, VW1306
NEXT
NEXT
LD Always_On:SM0.0 CRC16 word transfer
MOVB VB1307, VB1100
MOVB VB1306, VB1101

INT1
LD Always_On:SM0.0
RCV VB2200, 0

INT2
LD SM86.7
O SM86.6
O SM86.0
CRETI
LD Always_On:SM0.0
MOVD VD2204, VD1204
LD Always_On:SM0.0
CALL CRC16:SBR6
LDW<> VW1100, VW2208
CRETI
LDW= 16#0, C1
MOVD VD2204, VD2500
LDW= 16#1, C1
MOVD VD2204, VD2504
…………
Since the renovated equipment was put into operation in July 2005, the system has been stable, powerful and easy to operate, and has won unanimous praise from users, providing a favorable guarantee for the unattended operation of the substation and the safe operation of the substation.