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Dual Bus (N+1) Solution Description:
The internet data center (IDC) and media data center (MDC) are the regulation and control centers of high-speed internet. They can make the remote processing, storage and transfer of "timeliness"for the information resources (data, voice and image information) which the requirements are ultra-high. Even if it is just a few seconds of the "stop" will bring the immeasurable losses for the safe operation of entire Internet and production operation of users. When it is serious that can cause the serious damage for the social and economic activities. Therefore, the IDC must provide the 365×24h continuous high-speed, safe and reliable information resource value added services. For this purpose, the whole supply system of IDC has to adopt the high "fault-tolerance" function of redundant power supplying solution from the design principle to ensure that whatever the main power electrical network or inverter of "double conversion online UPS " is on the failure and it is on the daily maintenance operation or the fuse is blown/the breaker is off the inverter of online type UPS will supply the power to the internet devices, it shouldn't supply the power though the AC bypass of UPS that connected with the main power emergency standby UPS generator unit, because that is only the inverter of online UPS can supply the same voltage regulation, non- frequency "saltation", non-interference, minimum waveform distortion, high quality and sine power for the loads of users. For the off-line UPS and online interactive UPS, they mainly adjust the voltage of input supply and do not"substantively" improve the frequency jitter of input voltage, all kinds of supply interference and voltage distortion, that means there is no "bottleneck" fault risk in the whole power supplying system, so it must configure with the high "fault-tolerance" function of UPS redundant power supplying system, in other words when some "components"occasionally occur the fault in the operation of UPS power supplying system the whole UPS power supplying system must still be able to run. 
According to the technological development level of present UPS industry, it is advisable to choose the "dual bus input"and "dual bus output" power supplying function of UPS redundant power supplying system. It is composed of the following several parts of power supply system:
1)Dual bus input power supplying system
The basic configurations of dual bus input power supplying are main power input supply + "auto-switching"control cabinet + input distribution cabinet. The auto-switching control system always monitors the real time operation status of all kinds of input supply that can ensure to send the one route of most reliable supply to the input of UPS. For some important IDC computer rooms, theirs "emergency generator"supply is actually a set of "multi-diesel generator + generator combining control cabinet" consisted of the redundant type of generator power supplying system. The users must highly pay attention to the "technology compatibility"and "switching parameter"correct settings between the all kinds of devices which we mention above those in the redundant power supplying system which can ensure the "N+1" type UPS redundant power supplying system is able to operate absolutely safe and reliable. 
2)Dual bus output power distribution system
For eliminating the "single point bottleneck" fault risk between the input of UPS parallel operation system and the user sides, it is necessary to configure with the dual bus output distribution system, its basic configurations consist of the "N+1" type UPS redundant power supplying system (preferred, "1 +1" or "2 +1"-type parallel operation power supplying solution) + output distribution cabinet + load auto-switch (LTS) consisted of the UPS output distribution system. For some high requirement of places, it should configure with the load isochronous controller (LBS) + two sets of "N+1"type UPS redundant power supplying system consisted of the extreme high "fault-tolerance" function of power supplying system. According to the 30~50% of used servers and disk array machines and other productions in the IDC computer rooms which adopt the "dual-supply power supplying" system of productions, for these devices, we can directly connect the separate supply from the two sets of"N+1"parallel operation system with the two input ends of "dual-supply input device". For the key loads which have the "single supply input power supplying" mode, we will separately connect the supply heads of two sets of "N+1" type parallel operation system with the input ends of "load auto-switch" (commonly they are STS type of static switch and SS type of quick switch) and then to connect the key loads of users with the output ends of "load auto-switch".
Analysis of high reliability of dual bus N+1 system
If let the internet data center has the 365×24h "all day non-stop"operation characteristic that is the extreme strict requirement for the reliability of UPS, because the reliability of UPS is 99.999% that it will cause the "stop-time"of internet for 316 seconds in a year, the reliability of UPS is even improved to 99.999999% that it will still cause 320 milliseconds "stop-time" for the internet in a year. If the 320 milliseconds "stop-time" fault was really happened that would have brought the great losses. This is because the allowable instantaneous power interrupting time of the most computers is 10~18ms, otherwise the network control operation system or operating software of users will be damaged. So if let IDC computer rooms really have the 365×24h uninterrupted operation characteristic we only can provide the low fault rate UPS productions for this service so far according to the present UPS technology, we cannot manufacture the "zero fault" UPS productions. Adopting the "N+1" type of UPS redundant parallel operation power supplying system which can eliminate the single point "bottleneck" fault that is the best solution which can ensure the inverter input voltage of each single UPS under the same extent, frequency and phase position (the appeared "circumfluence"between the each single UPS is equal to zero) let the "N+1"sets of UPS with the same output frequency to place in the power supplying system of parallel operation output status. 
It makes the UPS parallel operation power supplying system to have the essential "fault-tolerant" function, the maximum load quantity should not be over the total input power of N sets of UPS single set. When the UPS parallel operation system operates normally the "N+1"sets of UPS averagely share the current of loads. When any one UPS is failure the broken-down UPS executes the "selective tripping"operations to automatically be out the operation, at the moment the rest of UPS continue to provide the high quality of inverter supply.  
With the quantity of UPS single set increasing in the UPS redundancy system, it not only can gradually decrease the reliability of whole set of UPS redundant parallel operation power supplying system but also it can gradually reduce the "rest capacity of output power"of whole set of UPS redundant parallel operation system (that means the anti-output overload ability of UPS parallel operation system also reduces gradually), so from the view of applied technology the users should try to choose the most reliable "1 + 1" or "2 + 1" type UPS redundant power supplying system.
Chosen good “compatibility” UPS redundant power supplying system for IDC Centralized Monitoring System
It is satisfied with the requirements of nobody or less people attended management and remote centralized monitoring for the IDC and MDC computer rooms to improve the "manageability"of UPS power supplying system. For the internet data center, except that it configures with the real-time monitoring network management system for its IT devices it also should build up a set of "non-IT devices" centralized monitoring system to monitor and analyze the cooling equipments, power distribution cabinet, battery units, electric generating set, leakage alarm, security system and fire-fighting system and so on operation situations, for this point the chosen UPS redundant power supplying system should configure with the following communication interfaces: 
1) Configured with the RS232/RS485 interfaces on the UPS, Modem or SNMP adapter;  
2) It is used to display the UPS's operation status and alarm information of "relay dry contact" type of output communication interface; 
3) "User-defined" input signal (door access, smoking, temperature, humidity etc. alarm signals) of "relay dry contact"type of input communication interface;   
4) Configured with the essential data collector for all kinds of "non-IT devices";  
5) Configured with the relative centralized monitoring and management software package or communication protocols.      
Using the above input/output communication interfaces and relative power supply management software package or users' network centralized monitoring system to assemble the intelligentized IDC and MDC centralized monitoring system. In this network management system, we can achieve the main regulation and control functions have:      
1) Please read the UPS real-time operation parameters (such as: input/output voltage, current, frequency, active power/ apparent output, power factor, charge/discharge voltage, current of battery units etc. parameters) on the LED/LCD of UPS;
2) All kinds of :"operation events" of computer room environmental regulation and control devices in the "internet data center" (the occurred faults/alarm/executed operation information of users in time orders since the all kinds of devices start up ) 
3) In case that the fault occurred, the system will execute the network broadcast alarm (pop-up the alarm windows), telephone/mobile phone auto-dialing/auto-papering or sending E-mail operations etc. It is handy to inform the staffs on duty to arrive the locations on time to exclude the problem and maintain;     
4)  Making the"self testing"operation for the battery capacity of standby battery units of UPS. If the system finds the "fact capacity" is lower the system will automatically send the early-warning signal of "need to change the batteries";      
5) The "user-defined" alarm signals (door access, fire-fighting, temperature, humidity etc. alarm signals) will be integrated into the uniform centralized monitoring system of IDC computer rooms or intelligent buildings through the input communication interfaces.     
The operator will be designated by the IDC and MDC, according to the different authority levels, they are classified by the "readjustment"settings which are the operation parameters of relative devices or remote fault analysis and diagnosis operations.
Dual Bus (N+1) Solution Diagrams:
Power Supplying Principle Diagram: