Principle and implementation of software redundancy in Siemens PLC - Database & Sql Blog Articles

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Soft redundancy, also known as software redundancy, is a solution for Siemens to implement redundancy functions, and can be applied to control systems that require less switching time between active and standby systems. Soft redundancy can be realized: mainframe power supply, backplane bus and other redundancy; plc processor redundancy; PROFIBUS network redundancy (including communication interface, bus connector, bus cable and other redundancy); interface module IM153-2 redundancy. When working in a software redundant system, the primary and secondary control systems (processor, communication, I/O) operate independently, and the PLC of the primary system masters the I/O control rights in the redundant ET200M slaves. The standby system synchronizes data through a dedicated software redundancy program. The PLC program consists of a non-duplicated user program segment and a redundantbackup user program segment. The main system PLC executes all user programs. The standby system PLC skips the redundancy program by judging the redundancy state and only executes Non-redundant user program. When a component in the primary system fails, the standby system automatically switches to the primary system, performs redundant procedures, and the control task does not interrupt.

Principle of soft redundancy and system configuration requirements

The CPU that can implement the software redundancy function has specific requirements. In the S7-300, the CPU of the 315-2DP type (including the 313C-2DP, 314C-2DP) can be supported. All the S7-400 CPUs support the software redundancy. The CPU models of the main and standby systems can be different, such as one system using the S7-400 series and the other system using the S7-300 series. Data synchronization can be through three different network modes: MPI, PROFIBUS and Ethernet. The I/O signals that need to be controlled by two systems need to be collected by the ET200M slave. Since two CPUs are to be connected, the ET200M should use the redundant IM153-2 interface module and adopt the active bus module. The software needs to install the software redundancy package, and the redundant function library will appear only when the software redundancy package STEP7 is installed.

Programming, debugging and troubleshooting of software redundant systems

The redundant software package in STEP7 contains several function blocks. Each function block has specific functions and calling methods, and the function blocks in different libraries are used differently, and need to be distinguished when used. Since redundancy is achieved through software programs, some features of the software redundancy system should be noted during programming and debugging. If the program block FC100 is initialized in OB100, the parameters for defining the system operation should be correct, and the address of the redundant output image area should be continuous. After modifying the system parameters, reset the CPU and re-download all the items to the PLC.

Soft redundant system connected to other systems

In the practical application, the software redundancy system also involves how to establish data communication with other systems and how to establish redundant links when connecting the upper monitoring software WinCC.

Surge Protection Device SPD

Product Description


SPD Surge Protective Device,Lightning Surge Protector
Surge Protection Device (SPD)


It is a device used to limiting instant surge voltage and discharge surge current, it at least including a non-linear component.

Surge protective Device Model Selection

With the impact of international information flow, the rapid development of microelectronic science and technology, communication, computer and automatic control technology, make the building start to go for high quality, high functional area, formed a new building style-intelligent building. As inside the intelligent building there are lot of information system, <<Building lightning protection design norm>> GB50057-94(2002 vision)(hereafter brief as <<lightning protection norm>>) put forward the relative requirement to install the surge protective device, to ensure the information system safely and stable running.
SPD essentially is a equipotential connection material, its model selection is according to the different lightning protection area, different lightning electromagnetic pulse critical and different equipotential connection position, decide which kind of SPD used in the area, to achieve the equipotential connection with the common earth electrode. Our statement will based on SPD's maximum discharge current Imax, continuous operating voltage Uc, protection voltage Up, alarm mode etc.
As per << Lightning Protection Norm>> item 6.4.4 stipulation "SPD must can withstand the expected lightning current flow and should confirm to the additional two requirements: the maximum clamp voltage during surge across, capable to extinguish the power frequency follow-on current after lightning current across." That is the value of SPD's max. clamp voltage add its induction voltage of two ends should be same with the system's basic insulation level and the equipment allowed max. surge voltage.

SPD for Power Supply System Series Selection Guide

The installation of SPD at each lightning protection zone, according to the standard of low voltage electrical appearance, make classification of electrical equipment in accordance with the over voltage category, its insulation withstand impulse voltage level can determine the selection of SPD. According to the standard of low voltage electrical appearance, make classification of electrical equipment in accordance with the over voltage category as signal level, loading level, distribution and control level, power supply level. Its insulation withstand impulse voltage level are:1500V,2500V,4000V,6000V. As per to the protected equipment installation position different and the different lightning current of different lightning protection zone, to determine the installation position of SPD for power supply and the break-over capacity.
The installation distance between each level SPD should not more than 10m, the distance between SPD and protected equipment should as short as possible, not more than 10m. If due to limitation of installation position, can't guarantee the installation distance, then need to install decoupling component between each level SPD, make the after class SPD can be protected by the prior class SPD. In the low voltage power supply system, connecting an inductor can achieve the decoupling purpose.
SPD for power supply system specification selection principle
Max. continuous operating voltage: bigger than protected equipment, the system's max. continuous operating voltage.
TT System: Uc≥1.55Uo (Uo is low voltage system to null line voltage)
TN System: Uc≥1.15Uo
IT System: Uc≥1.15Uo(Uo is low voltage system to line voltage)
Voltage Protection Level: less than the insulation withstand impulse voltage of protected equipment
Rated discharge current: determined as per to the lightning situation of the position installed and lightning protection zone.
SP1 Series

Normal Working Conditions
-Altitude not exceed 2000m
-Ambient air temperature:
Normal range: -5ºC~+40ºC
Extend range: -40ºC~+80ºC
-Relative Humidity: 30% - 90% under indoor temperature condition
- At the place without obviously shaking and shock vibration
- Non-explosion danger medium, non-corrosion gas and dust ( including conductive dust)

Classification

-As per Nominal Discharge Current:
5,10,20,30,40,60KA(8/20µs)
- As per Maximum continuous operating voltage:
275V,320V,385V,420V,440V,460V
- As per to poles
1P,1P+N,2P,3P,3P+N,4P
- As per auxiliary functions:
a. With remote signal output ( remote alarm function)
b. Without remote signal output

Selection Principle

- The continuous applied voltage on the two terminals of SPD should not more than the maximum continuous operating voltage Uc value;
- The voltage protection level Up of SPD should less than the maximum impulse withstand voltage of the protected equipment;
- As per to the different earthing system and protection mode to select the specification accordingly;

Product Features

1, built-in over-current overheating, temperature control circuit technology.

2, the module design, easy installation, online replacement.

3, low leakage current, fast response time, low residual voltage.

4, alarm indication device, green (normal) v red (fault).

Model/Technical Parameters WR-B60 WR-B80 WR-B100 WR-B120 WR-B150
Rated Operating Voltage Un (V ~) 220V 380V 220V 380V 220V 380V 220V 380V 220V 380V
Maximum Continuous Operating Voltage Uc (V ~) kV 385V 420V 385V 420V 385V 420V 385V 420V 385V 420V
Voltage Protection Level Up (V ~) kV ≤1.8≤2.2 ≤2.4≤2.5 ≤2.5≤3.2 ≤3.4≤3.7 ≤4.0≤4.5

Maximum Discharge

Current Imax(8/μ20μs)kA

60 80 100 120 150

Nominal Discharge

Current In(8/μ20μs)kA

30 40 60 80 100
Response Time <25 <100
L/N(mm²)The Cross Section Of L/N Line 16,25 16,25 16,25 16,25 25,35
PE (mm²)The Cross Section Of PE Line 16,25 25,35 25,35 25,35 35
Fuse or Switch (A) 63A 63A 63A,100A 63A,100A 63A,125A
The Line Section of Communication and Alarm (mm²) ≥ 1.5

Operating

Environment-C

(-40ºC~-+85ºC)
Relative humidity 25 ºC ≤95%
installation Standard Rail35mm
Material of Outer Covering Fiber Glass Reinforced Plastic

Surge Protector SPD,Surge Protection Device SPD,SPD

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