General-purpose electric networks of the Russian Federation are characterized by low quality of electric energy - outages, high-frequency noise, frequency deviations, voltage dips, etc. According to the conclusion State Center metrological support in the field of electromagnetic compatibility (GTsMO EMC), the requirements of GOST 13109-87 for indicators of the quality of electrical energy (PQE) by power supply and power distribution organizations, as a rule, are not met. In addition, the power quality requirements set in GOST are often not high enough for modern telecommunications equipment.
It is obvious that the connection to real-life electric networks of high-tech equipment that is sensitive to the deterioration of the quality of electric energy (computers, active equipment of computer networks, telecommunications equipment, banking and office equipment) is associated not only with an increased risk of malfunctioning, but also of the exit of this equipment from building.
Under these conditions, the installation of static uninterruptible power supplies (UPS) operating in the "on-line" (double conversion) mode, as a means of obtaining electricity of the required quality, is a necessary prerequisite for ensuring the stable operation of computer and telecommunications equipment. In addition, modern equipment is characterized by the use of switching power supplies with a non-linear nature of consumption. The use of powerful three-phase double-conversion UPS to power this kind of equipment is optimal, since it avoids overloading the neutral cables of the input power networks and equipment of transformer substations.
Powerful "on-line" UPSs are the basis for building uninterruptible power supply systems (ESS) and ensure high-quality operation of the load connected to them both in normal mode (when there is power supply at the input) and in offline mode (when the input power supply is turned off) for account of the energy stored in batteries. As a rule, such systems are designed to work offline for a period of time from several minutes to several hours. If it is necessary to ensure the operation of the connected load for a longer time, the complex includes autonomous power generating sets built on the basis of internal combustion engines (usually diesel engines) as a backup source of energy.
The necessary result achieved in the implementation of the SES can be considered to ensure the possibility of the operation of the Customer's critical equipment in the event of a failure of the stationary input (inputs) of power supply for a period of time sufficient to switch to a backup power source or normal completion of the main work processes in computer networks.
The purpose of developing an uninterrupted power supply system (ESS) is to provide high-quality uninterrupted power supply to responsible consumers of a banking type institution (hereinafter referred to as the Customer) both under normal conditions and in cases of disruption of regular power supply due to accidents or deterioration of its quality in conditions of industrial or other interference.
General requirements for uninterruptible and guaranteed power supply systems
This section presents materials reflecting the main approaches and technical solutions for providing guaranteed and uninterrupted power supply to responsible consumers in terms of designing uninterrupted power supply systems.
The statement of the problem and the main requirements for the SHE are considered, the main provisions of modern concepts for constructing power supply systems for critical facilities are outlined, the selected schematic diagrams and models of equipment are substantiated, technical and performance characteristics the equipment used.
The main modes of operation of individual components and the complex are considered. technical means, as well as general and special requirements for other equipment, materials and premises. The implementation of the SHE in accordance with the considered principles meets the requirements of the Customer and the most modern world standards in the field of life support systems and power supply.
As an example of equipment for the SHP, the use of UPS and DGU from leading manufacturers (Powerware, Wilson) is considered, which meets the most stringent standards in these industries and allows you to build a SHP with increased reliability.
Requirements for hardware and subsystems. Formulation of the problem. Technical requirements for the guaranteed power supply system.
Customer's electrical consumers requiring connection to a secure electrical network, as a rule, are divided into the following main groups:
- local area network equipment (PC, active network equipment);
- communication systems (ATS), special communication complexes;
- technical means of a satellite data transmission network;
- system emergency lighting;
- air conditioning and ventilation systems for technological premises;
- fire and burglar alarm;
- medical equipment.
The parameters of the electrical network at the output of the power supply systems installed within the framework of the SES must comply with technical requirements for the operation of computer technology and other electronic equipment of the Customer.
The system should provide the function of alerting personnel about emerging emergencies in power supply systems. Automatic closing of the Customer's information system with guaranteed preservation of data integrity is carried out when it is impossible to ensure the autonomous operation of consumers for a long time.
In case of long interruptions in the power supply and the need to continue the operation of the equipment over the minimum period, the power supply should be provided from an autonomous diesel generator set (sets) while maintaining high quality parameters of the power grid at the output of the SGE. Turning on and off the generator set must be carried out in automatic mode with the possibility of an emergency transition to manual control.
The main provisions of the concept of building a guaranteed power supply system. Justification of design decisions.
The construction of uninterruptible power supply systems for a complex of consumers located geographically on more than one floor, and, moreover, in several buildings, can be carried out according to various schemes.
At present, the two main structures of the SGE are most widely used - centralized and distributed (localized). The centralized system contains one UPS, to which all critical consumers are connected. In a distributed system, each consumer (or group of local consumers) is powered by a separate (local) UPS.
Distributed structure of the SGE
The generalized diagram of the guaranteed energy supply system, built according to the centralized scheme, is shown in fig. one.
Rice. 1. Generalized scheme of distributed SGE.
The main advantage of such a system is the possibility of its implementation without altering the network wiring, especially when using "socket" UPS, ease of expansion or reconfiguration.
If one of the UPSs fails, only part of the system is turned off, and, with one device in the "cold" standby, the consequences of the failure can be eliminated within a few minutes. Another important advantage of this system may also be that with an appropriate choice of UPS types, no special premises will be required for their placement.
The disadvantage of a distributed system is the inefficient use of battery resources due to the impossibility of ensuring the same load for all UPSs. The battery life of the entire system is determined by the most loaded unit with the most discharged batteries during previous power outages, while the battery life cannot be increased by disconnecting the load from other UPSs. Another significant disadvantage of this system is its low resistance to overloads caused by an erroneous connection of an additional load or a short circuit. The increased sensitivity to overloads is due to the fact that the power reserve of local UPSs can be comparable to the starting power of not only an air conditioner or a vacuum cleaner (5-10 kW), but also laser printer or a photocopier (2-5 kW) and even a color monitor with a screen size of 19-21 inches with a degaussing loop (1-2 kW).
Another significant drawback of the distributed SGE takes place when using a large number single phase UPS. As noted above, a significant part of modern computer and telecommunications equipment has power supplies characterized by a non-linear nature of consumption (cos = 0.7-0.8). When several such consumers are connected to a single-phase network (with an operating voltage of 220 V), which is an integral part of a three-phase power supply network (with an operating voltage of 380 V), currents arise in the neutral conductor, the peak values \u200b\u200bof which may exceed the currents in the phase conductors. Taking into account the fact that electrical networks in our country are made with a neutral conductor of a smaller (compared to phase) section, overloads and interference in the neutral are inevitable, which lead to a decrease in the reliability of the power supply network.
Increasing the reliability of power supply is possible when laying cable networks with a large (1.5-1.7 times) cross-section of the neutral conductor compared to phase conductors. Unfortunately, such work in terms of urban power supply networks, as a rule, is extremely difficult.
Centralized structure of the SGE
The advantages of this system (Fig. 2) are determined by the concentration of power reserve and battery capacity. Such a system is less sensitive to local overloads and even withstands short circuits, the contact resistance of which exceeds a certain value determined by the UPS output power reserve. An increase in autonomy time is achieved by simply turning off less responsible consumers.
Rice. 2. Generalized scheme of the centralized SGE.
Another advantage of the centralized SES, built on the basis of a powerful three-phase UPS, is the elimination of overloads of the neutral conductor at the input of the UPS, which increases the reliability of the entire power supply network, and, which is essential, does not require relocation of cable lines through which the building is supplied with energy.
The disadvantage of a centralized system is a higher probability of a local failure compared to a distributed system, which is expressed in the de-energization of consumers due to a malfunction of an extensive output power supply network or a failure (associated with a short circuit in the power circuit) of one of the consumers.
The cost of hardware of a centralized system with equal power and identical UPS circuitry solutions is, of course, lower compared to a distributed system, however, when choosing this ESS structure, it is necessary to take into account the cost of a possible alteration of the power supply network in case of reconstruction of the existing system, as well as the need to allocate a special room and a qualified personnel.
In its pure form, each of the considered systems is used quite rarely. The use of a centralized system is advisable when there is a concentration of equipment that performs a single task and consists of components of the same reliability class and the same energy consumption characteristics. Such systems are used, as a rule, in publishing complexes, large satellite communication centers, etc. Typical for a distributed system are such administrative institutions (mayor's office, ministry), in which a large number of personal computers operate in the mode of independent workstations, often without combining them to the local area network.
Two-level SGE
To eliminate the shortcomings of each of the systems, a two-level system is used in practice, which is a combination of a centralized and a distributed system (see Fig. 3). The task of optimizing such a system in terms of power and cost of equipment is to determine the most responsible consumers and minimize the number of consumer groups by appropriately configuring the local area network.
Rice. 3. Generalized scheme of two-level SGE.
When choosing a two-level structure, in addition to installing a single high-power UPS (or a complex of parallel operating UPSs located in one place - as a rule, near the electrical input to the building), the individual most critical consumers are protected by local lower power UPSs. The purpose of this redundancy is to protect equipment such as file servers and the most critical LAN management workstations, communication equipment, communication systems from blackouts due to cable network failures inside the building caused by local damage, short circuits or overloads (including net power supply connected to the main UPS).
When choosing any of the options for building an uninterruptible power supply system based on a UPS, if necessary, provide long work in autonomous mode (i.e. when the input power supply is turned off), such a complex is supplemented by one or more diesel generator sets (DGU) to ensure long-term autonomous operation (for tens of hours or more). Such generators are equipped with an automatic start and shutdown system with load switching and can be additionally equipped with remote control and monitoring panels. The diagram of the operation of the complex in the event of an emergency shutdown and subsequent restoration of the main power supply is shown in fig. 4.
Rice. 4. Timing diagram of the operation of the UPS-DGU complex.
When determining the power and number of generating sets, it is necessary to take into account the power of the connected load, as well as the possibility of installing sufficiently large-sized equipment in the building or in its immediate vicinity (in a protected area). The generator set can be made in a noise-protective casing or an all-weather container.
When several generators are connected to a common load, a special control and synchronization unit is installed for the parallel DGU complex.
Functional diagram a typical SHE for the Customer's building is shown in Fig. 5. The diagram shows the main power supply lines, technological and household consumers are highlighted (general lighting, network electrical sockets to connect household electrical appliances), technical means and power supply lines that are part of the SGE.
Rice. 5. Functional diagram of the SGE building.
It is expedient to divide SGE energy consumers into two groups:
- The first group includes equipment that requires power supply with consistently high power quality indicators, and also does not allow (according to the conditions of the technological cycle) interruptions in power supply. This group of consumers includes all computer equipment, communication systems, active network equipment, video surveillance equipment, alarms, medical equipment. On the diagrams, this group is designated "Consumers of the SGE -" A "". The consumers of this group are connected to the output of the UPS.
- The second group contains equipment connected directly to the output of the DGU, which does not require stable high quality indicators power quality and allowing a short interruption (30-120 sec.) in the power supply. This consumer group includes emergency lighting systems, as well as room conditioning equipment to house the UPS complex. On the diagrams, this group is designated "Consumers of the SGE - "B"". This group also includes systems such as, for example, a set of security equipment, alarms and other equipment protected by local UPSs.
Allocation within the framework of the SGE of two groups of consumers connected to power supplies various types(UPS and DGU) allows to achieve the following results:
- The exclusion from group "A" of such consumers as air conditioning systems and emergency lighting allows to reduce the load on the UPS, which, in turn, increases the battery life of the UPS in emergency mode and makes it possible to use a lower power UPS.
- With this connection scheme, the UPS provides galvanic isolation between the power supply networks of computer and communication equipment and the power supply network of process equipment (in particular, air conditioning systems). This allows you to significantly reduce the level of interference in the protected power supply network when turning on and off the equipment, which is characterized by a non-linear nature and large starting current consumption values.
Ensuring the reliability of the SGE. Special requirements for the SGE equipment.
In the considered project of the SHE, an increase in reliability is achieved through the use of a cascade structure of the SHE and a parallel UPS complex at the basic level of protection. The essence and advantages of the cascade scheme were discussed above.
Powerware's parallel UPS solutions are unique in the high-power UPS sector in the world and include the following:
- it is possible to combine up to 8 devices in parallel of the model, thus, the total output power of the complex can reach 5 mVA (8 blocks of 625 kVA each);
- Structurally, the parallel system consists of 2-4 system units and a parallel cabinet that combines the UPS outputs. The system works on a unique "HotSync" peer-to-peer control algorithm patented by "POWERWARE", and not in the "Master-Slave" mode, like other UPS manufacturers.
The uniqueness of this technology lies in the absence of signal or interface connections between the UPS when the sources are connected in parallel. This significantly increases the reliability of the system, reduces the cost and simplifies its installation.
Rice. 6. Modular and centralized schemes for constructing the SGE.
Combining several UPS units into a parallel complex, as a rule, aims to solve the following tasks:
- After installing one SHE unit of a certain capacity, the number of technical systems requiring protected power increases. As a result, it is necessary to increase the power of the SGE, which is achieved by connecting another UPS unit of the same power. All UPSs in such a complex work in parallel for a common load, increasing the output power.
- According to the technical operating conditions of the equipment, it is necessary to guarantee its power supply even in the event of a failure of one of the UPS units. In this case, it is necessary to build a parallel complex according to the scheme with hot hardware redundancy (redundancy). Such a scheme also allows maintenance and repair of any UPS unit, not only without disconnecting the load, but also maintaining consistently high power quality at the output of the complex (see functional diagrams in Fig. 7).
Rice. 7 Diagrams of operation of parallel UPS complexes.
Comparison of the statistical characteristics of the reliability of parallel complexes built on a centralized and modular basis shows the following:
- the presence of a backup input (with the same reliability as the main input) significantly increases the reliability of the complex as a whole. However, it must be borne in mind that when the load is connected to the backup input, its power is supplied from an unstabilized network;
- a modular system, other things being equal, has a lower level of reliability. The positive feature of such a system is, as noted above, its lower cost and flexibility of extension.
Uninterruptible power supplies. double conversion UPS. General information.
The functional diagram of a UPS built using double conversion technology is shown in fig. 8. The main components of the UPS have the following functions:
- The input and output RF filters are designed to filter high-frequency and impulse noise.
- The input converter converts AC to DC and provides sinusoidal consumption (cosf=1).
- The output converter converts DC power from the input converter or battery (when operating offline) into an alternating voltage with consistently high SCEs.
- The battery pack stores electrical energy in batteries.
- The by-pass redundant line switch provides automatic or manual switching of the load between the converter output and the redundant line. Switching is carried out with synchronization of the output voltage, the switching time is fractions of milliseconds.
- The microprocessor control unit monitors the functioning parameters of all UPS components and manages them, as well as information exchange with external devices.
Rice. 8 Functional diagram of double conversion UPS.
Basic information about the status of the UPS is displayed on the LCD on the front panel of the UPS.
The connector on the rear panel can be used both for transmitting signal information (messages about an input network failure, switching to a backup line, low batteries), and for monitoring and controlling the UPS via the RS232 protocol.
When installing specialized software from Powerware, the user can control the following parameters:
- UPS operation mode (from the input network, from batteries, load connection via a backup line);
- current value of the input voltage (in V);
- current value of load power consumption (in VA);
- predicted UPS runtime (in minutes);
- battery temperature and voltage;
- output voltage and frequency values.
If necessary, actions such as automatic UPS test, battery test, battery calibration test (to determine the actual capacity after a certain operating time), as well as turning off and turning on the UPS at a given time can be programmed.
Estimated data
The choice of specific models of UPS and DGU for the designed SPP is made on the basis of data on the current and predicted state of the Customer's equipment, which requires connection to an uninterrupted power supply network.
When calculating the required power of the UPS, it is taken into account that during long-term operation of powerful UPSs in a distributed network of consumers connected to its output, the possibility of local overloads and the inclusion of unauthorized loads cannot be excluded. To ensure stable trouble-free operation of the equipment, its power is selected with a margin of 15-20% of the calculated load power. On the other hand, to ensure redundancy of the parallel UPS complex in the Customer's building, the condition must be met so that the calculated load power does not exceed the total output power of the UPS without redundancy.
When calculating the power of a generator set, it is necessary to take into account both the total power consumption of the load and recommendations for the minimum allowable load value of 30%. With long-term operation of a DGS with a lower load value, the engine service life is significantly reduced and special maintenance measures are required.
Since the total power consumption of the UPS parallel complex (i.e., the power at the UPS input) may further increase with the increase in the number of jobs, the calculation of the power of the genset takes into account the total power consumption for all UPSs connected to the genset output and operating in full mode. load and charge of batteries, as well as additional equipment (load group "B").
Diesel generator stations
DGU manufactured by Wilson
Wilson diesel generator sets are used as offline source electricity and can operate both in emergency (short-term) mode and in continuous mode and play the role of the main source of energy supply.
In the considered SGE, models of generator sets built on the basis of Perkins diesel engines, Leroy Somer alternators can be used.
The FGWILSON company was founded in 1966 and is the largest manufacturer of diesel generators in Europe, which are used as a main, backup or emergency source of electricity to supply various consumers with alternating single-phase (220/240V, 50/60Hz) or three-phase current (380/400V, 50/60Hz). Firm "F.G.WILSON" produces up to 20000 diesel generators per year, which are exported to 150 countries of the world. The DGU uses engines from leading manufacturers such as Perkins, Lister-Petter, Detroit-Disel Corporation, etc.
Specifications
Description of the functioning of the SGE in various modes
Under normal conditions, i.e., while maintaining the main power supply of the building through city lines, the SGE equipment operates in the following mode:
The contactor in the control and load switching unit of the DGU is in the "Mains" position, i.e. main network. The power supply of consumers of group "B" is carried out through this contactor directly from the main network. The UPS (or a parallel UPS complex) is also powered from the main network through the contactor BU KN DGU (see Fig. 0-9). Operating in double conversion mode, the UPS provides consistently high output power quality. Batteries are in the float charge mode, thereby ensuring their maximum life when the external power to the UPS is turned off.
Rice. 9. Scheme of power supply to the load in the normal mode of operation of the SGE.
In the event of an emergency (disconnection of power supply via city networks), power is lost at the input of the main UPS, which switch to battery operation. There is no interruption in the power supply to consumers of group "A", since the double conversion circuit ("on-line") guarantees uninterrupted operation of the inverter (see Fig. 10).
Rice. 10. Scheme of power supply to the load in the emergency mode of operation of the SGE.
Upon a command from the sensor for the presence of the input network, built into the control unit of the SS of the genset, the countdown begins (the duration of the interval is programmable), after which the control unit gives a command to start the genset. If the first start attempt was unsuccessful, the automation unit repeats the start command. After the genset reaches the operating mode (frequency and voltage are within tolerance), the control unit ensures that the load contactor switches to the generator output (see Fig. 11). The microprocessor control unit of the Powerware UPS is a "soft start" algorithm, with the help of which the increase in input consumption when the UPS is powered up does not occur abruptly, but gradually (the duration of this interval of increasing the load to the maximum value is at least 10 seconds). This UPS function allows not to overload the generator when a large load is connected and to keep the PQ at its output within the nominal values.
Rice. 11. Scheme of power supply to the load in the emergency mode of operation of the SGE.
In autonomous mode, the SHE can operate for a long period of time, determined by the amount of fuel in the fuel tank of the DGU and the specific fuel consumption (the value of this parameter depends on the load). If the power supply through the city networks is not restored at the end of the fuel resource in the standard fuel tank, then the DGU automation unit stops the generator without generating the minimum fuel reserve necessary for a guaranteed start of the DGU in the future. In this case, the Customer's on-duty personnel must decide whether to stop the operation of the equipment and turn off the UPS, or to continue working until the battery life is exhausted and the UPS automatically turns off. UPS battery life is a function of the current power consumption, so reducing power consumption by turning off less critical loads (workstations) can significantly extend battery life.
The cascade structure of the SGE construction provides an additional resource for autonomous operation for the most critical equipment (server complexes, active network equipment, and communication systems). Therefore, even when the central UPS (or a parallel UPS complex) is turned off, the file structures on the servers are not disturbed, since the special software for communicating with the UPS initiates the process of shutting down the servers automatically when the central UPS is turned off.
When the power supply failure of the building is eliminated before the diesel generator fuel resource is exhausted, the diesel generator control unit, on command from the input network status sensor, switches the load to the main input by a contactor (see Fig. 0-12). After that (120 seconds after the load is disconnected from the generator), the engine is automatically turned off. This period of time, during which the genset runs without load, allows the generator and engine to cool down quickly, which guarantees a more reliable start of the genset in the following accidents.
Rice. 12. Scheme of power supply to the load during the elimination of the accident.
Since the power supply of critical consumers (group "A") is carried out through the UPS, distortion and interference caused by the switching of the DGU contactor do not affect the protected power supply network.
Remote control systems
SGE monitoring tools. Interfaces with information complexes of the Customer
Software and information interfaces of the SGE The functional completeness of the SGE is ensured by the inclusion in its composition of a complex of monitoring and control tools for the SGE, which implements the following main functions:
- Use of standard (included in the respective operating systems) and specialized software installed on servers to work with UPS connected to them.
- Organization of the process of closing server file systems in automatic mode at the end of the battery life, followed by disconnecting the load and turning off the UPS to prevent battery discharge.
- Notification of users about emerging malfunctions in the electrical network, about the upcoming closure of server file systems and shutdown of uninterruptible power supply systems.
- Organization of interaction with special software installed on a dedicated workstation - local network administrator workstation (for example, Novell NMS for Windows, HP OpenView for UNIX, SUN NetManager, etc.) to perform UPS monitoring and diagnostics.
- Ensuring reception additional information from sensors connected to special UPS inputs, and its transmission over the local network. Smoke sensors, temperature rise sensors, access control systems to the room where the UPS is located and similar contact devices can be used as such devices. It is also possible to connect executive devices (for example, additional ventilation), which are controlled in automatic or manual mode using UPS monitoring programs.
All of the above functions are implemented by installing special software and hardware for integrating the UPS into the local area network. These include: software Lansafe for Novell NetWare, UNIX and Windows, and Connect UPS web/SNMP adapters from Powerware.
To protect single PCs, as well as technical means that are not related to computer equipment, UPSs are used that are connected by a standard power cable to the power supply of the protected device. If the UPS protects a single computer or a workstation connected to a LAN, but other users do not need information about the status of this UPS, then the UPS-PC data communication is not implemented. Otherwise, an additional connection is made (usually with an RS232 serial data cable - see the diagram in Figure 0-13) and the local software (without SNMP support) is installed on the workstation in question.
When several computers are connected in groups to one UPS, as well as for hierarchical networks with "client-server" logical connections, information about the state of the UPS should be sent primarily to servers (file, database, applications), as well as to workstations that are logically dependent from these servers. In such cases, information communication can be carried out in two ways: using hardware (WEB / SNMP adapter) in combination with software, as well as using a purely software method.
The use of a WEB/SNMP adapter is most appropriate for powerful UPSs located at a considerable distance from the server complex. In addition, the installation of powerful (several tens of kVA) uninterruptible power supply equipment is usually carried out in a separate room with limited access, including for personnel involved in LAN maintenance. Thus, it becomes necessary to use an auxiliary device that acts as an interface between the UPS and the LAN. WEB/SNMP adapters are used as such devices.
This adapter includes a programmable microcontroller that converts data messages from the UPS that arrive as a certain sequence of characters via a serial communication channel (usually RS232) into the SNMP message format. These messages are processed by software installed on servers and workstations. The functional diagram of the SGE fragment using the WEB/SNMP adapter is shown in Fig. thirteen.
The WEB/SNMP adapter with its internal software is referred to as the "agent", while the software on workstations and servers is referred to as the "client".
Rice. 13. UPS-LAN communication using WEB/SNMP adapter.
When connecting the UPS with an interface cable (according to the RS232 serial protocol standard) directly to a NetWare file server, or UNIX installation A WEB/SNMP adapter is not required, since the functions of an SNMP agent are performed by special software installed on the server (Fig. 0-15). This software (consisting of several software modules working together) allows the simultaneous translation of messages from the UPS in SNMP format, as well as the execution of necessary operations closing the file system, notifying users, etc.
Most often, such a connection is used to install a UPS with a capacity of up to 15-20 kVA when organizing uninterruptible power supply for server complexes and the most critical workstations (for example, a LAN administrator's management console). A fragment of the SGE of this kind is shown in Fig. 14.
Rice. 14. Data communication UPS-LAN without WEB/SNMP-adapter.
SGE software and information interfaces
The functional completeness of the SGE is ensured by the inclusion in its composition of various hardware and software tools for monitoring and controlling the SGE, which implement the following main functions:
- Organization of information communication between all UPSs (primary and secondary) and NetWare file servers, Windows NT servers, UNIX control computer systems and similar equipment.
- Use of standard (included in the respective operating systems) and specialized software installed on servers to receive, display and process information about the status of the UPSs that power these servers.
- Organization of the process of closing file systems of servers in automatic mode at the end of the battery life.
- Notification of users about emerging malfunctions in the electrical network, about the upcoming closure of servers, as well as about the shutdown of uninterruptible power supply systems.
- Organization of interaction with special software installed on dedicated workstations - local network administrator workstations (for example, Novell ManageWise for Windows, HP OpenView for UNIX, SUN NetManager, etc.) to perform UPS monitoring and diagnostics.
- Ensuring (when using additional equipment) the reception of information from sensors connected to special UPS inputs, and its display on the visualization systems of operational information of the personnel on duty.
All of the above functions are implemented by installing special software and hardware for integrating the UPS into the local area network. These include: Lansafe software for Novell NetWare, UNIX and Windows as well as WEB/SNMP adapters.
WEB/SNMP adapters. General description.
When several computers are connected in groups to one UPS, as well as for hierarchical networks with "client-server" logical connections, information about the state of the UPS should be received, first of all, on servers (file, database, applications), as well as on workstations, logically dependent on these servers. The function of notifying all users connected to any server powered by a UPS is implemented by the software installed on this server.
In such cases, information communication can be carried out in two ways: using hardware (WEB / SNMP adapter) in combination with software, as well as using a purely software method.
The use of a WEB/SNMP adapter is most appropriate for powerful UPSs located at a considerable distance from work premises (including the server complex premises). In addition, with the help of the UPS, equipment is protected that does not include a computer, for example, a complex of active network equipment installed in a LAN distribution cabinet.
Thus, it becomes necessary to use an auxiliary device that acts as an interface between the UPS and the LAN. WEB/SNMP adapters are used as such devices.
The adapter contains a programmable microcontroller that converts information packages from the UPS, received in the form of a certain sequence of characters via a serial exchange channel (usually RS232), into the message format in the WEB/SNMP standard. These messages are processed by software installed on servers and workstations. The functional diagram of the SGE fragment using the WEB/SNMP adapter is shown in fig. 14.
WEB/SNMP-adapter with its internal software forms an integral part of the information system, called "agent", and software on workstations and servers - "client".
The main tasks of the SNMP agent are to translate information messages about the status of the UPS into the format of special packages in the SNMP format - the so-called traps (interrupts), as well as the translation of special UPS management commands sent by SNMP clients into the format of control sequences of a specific UPS model • The UPS model recognition is done automatically by the SNMP client software.
The UPS is connected using special interface cables to the connectors on the rear panel of the WEB/SNMP adapter. Connectors for connecting the adapter to the LAN are made in the BNC and RJ45 standard and are designed for Ethernet networks. Powerware also produces a WEB/SNMP adapter for local networks token ring.
The adapter comes with floppy disks containing MIB files (in DOS/Windows and UNIX format) used to install the LAN management software.
Operating conditions of the equipment
The mode of operation of the main equipment of the SGE is determined by the organizational and technological features operation of information and other services of the Customer, as well as technical conditions and recommendations of manufacturers of the relevant equipment.
Uninterruptible power supplies manufactured by Powerware are designed for continuous round-the-clock operation. When operating the equipment, it is necessary to fulfill the conditions for maintaining the temperature regime in the room where the UPS is installed.
Powerware uninterruptible power supplies can be operated in weather-protected rooms in the temperature range from 0°C to +40°C at a relative humidity of no more than 90% (at 20°C). The temperature value averaged over the daily period should not exceed +35°С. The maximum duration of the period during which the UPS operates at a temperature of +40°C should not exceed 8 hours.
It is necessary to distinguish between the concepts of permissible operating and optimal temperatures. For a UPS, the most important component of which are batteries, the optimum temperature value is determined by the recommendations for their operating conditions. Optimum temperature, at which manufacturers of lead-acid batteries guarantee the maximum number of charge-discharge cycles and electrical characteristics, is +15 .. +25°C. As the temperature rises, the life of the batteries will be shortened in the first place. The empirical dependence is expressed as follows: for every 10°C increase in temperature, the service life is halved.
Thus, one of the necessary conditions for long-term trouble-free operation of the UPS is to maintain the air temperature at 20°C.
Wilson diesel generator sets are designed for long-term operation in weather-protected environments. Automatic start of the DGU without the participation of personnel (i.e., without the need to perform additional operations for the technical preparation of the DGU) is guaranteed provided that the ambient air temperature is not lower than +5°С.
Service regulations. Warranty obligations.
Maintenance. General provisions.
Maintenance provides for the performance by the Contractor's personnel of the necessary routine and preventive maintenance within 1 year from the date of putting the equipment into operation.
When performing work outside the scope warranty obligations, the Customer reimburses the Contractor for the cost of replaced parts and assemblies and the costs associated with the performance of these works. The Customer compensates the Contractor for the costs associated with the unreasonable call of the Contractor's technical staff (false call).
Parts and assemblies used during the warranty repair from the spare parts and accessories kit purchased earlier by the Customer are replenished at the expense of the Contractor.
Warranty
The warranty period for the main equipment of the SGE is 12 (twelve) months from the date of putting the equipment into operation, but not more than 15 months from the date of transfer of the equipment to the Customer, which is confirmed by the relevant documents.
The warranty period for DGU is 12 (twelve) months from the date of putting the equipment into operation, but not more than 500 hours of operation according to the engine life meter.
During warranty period the equipment supplier replaces defective components that have manufacturer's defects and failed if the Customer observes the operating conditions.
Conclusion
The proposal for a system of uninterrupted power supply of a banking type institution sets out the proposed technical solutions and provides their rationale. The implementation of the SHE in accordance with the considered principles meets the requirements of the Customer and the most modern world requirements in the field of life support systems and power supply.
The equipment offered for use meets the most stringent standards in these industries and allows you to build a high-reliability SGE.
Abbreviations:
- SGE - system of guaranteed energy supply
- PQI - power quality indicators
- ASU - introductory Switchgear
- Main switchboard - main switchboard
- РШ - switchboard
- RSH LAN - switch cabinet of local area network
- OS - operating system
- Software - software
- UPS - Uninterruptible Power Supply
- DGU - diesel generator set
- BU KN - control unit and load switching
In conditions of unstable power supply, it often makes sense to play it safe and protect yourself from unpleasant surprises that can be presented by centralized power networks.
For example, it is often possible to observe how the voltage in the network drops or jumps. This can be most clearly seen by paying attention to how an ordinary incandescent lamp glows - if it flickers or burns half-heartedly, then there is a problem in your electrical network. Insufficient voltage levels or voltage fluctuations can cause malfunction of sensitive equipment, loss of computer data and other unpleasant consequences.
Voltage surges are also possible, most often caused by short circuits or lightning strikes on wires or a substation. Despite the measures taken to protect against thunderstorms, such cases happen from time to time and, in addition to malfunctions, can lead to equipment failure.
In addition to the listed violations of the network, a complete disappearance of voltage is also possible - short-term or rather long. As a result, production is paralyzed, various systems stop working - communications, security, life support, and others.
Therefore, in some cases, it is required to take additional measures and install equipment that will minimize the negative consequences of centralized power grid failures.
There are two types of such systems - uninterruptible power supply systems and uninterruptible power supply systems. Let's take a look at how they differ below.
Differences between uninterruptible and guaranteed power supply systems
An uninterruptible power supply system most often implies the presence of uninterruptible power supplies (UPS), which, if necessary, switch the equipment powered by them to battery operation. During normal utility operation, the UPS batteries are charged. The UPS is also equipped with line filters that help cut off high-frequency interference in the mains, voltage surges, and so on.
Such a measure is effective if you experience short-term power outages or power surges in your network - UPSs cope with such troubles quite effectively. However, in order to maintain the operation of equipment or office equipment during a long shutdown, the resources of uninterruptible power supplies are not enough. All they can do in an emergency is give users a few minutes to turn off the office equipment and save the necessary data.
To withstand prolonged power outages, uninterrupted power supply systems, or ESS for short, are required. In addition to uninterruptible power supplies, such a safe system assumes the presence of a diesel generator set (abbreviated as DGU), which performs the role of an emergency power supply unit during a long outage of the central power supply, and the necessary monitoring and control equipment that allows the UPS and DGU to interact in the complex.
Design and uninterruptible power supply installation are justified if there are frequent power outages and there are consumers at your facility for whom continuity and high quality power supply.
Under such conditions, the losses from failures in the operation of the power grid can be so significant that they repeatedly exceed the cost of purchasing and installing special equipment, you should also take care to install such a connection scheme at strategic facilities or in the case when a power outage can lead to human casualties.
The purpose of the creation of the SGE and the requirements for it
So, in order to create an uninterruptible power supply system at any facility, everything is clear - such a system must guarantee a stable high-quality power supply for responsible energy consumers in case of incorrect operation of centralized power networks. The result of creating such a system at the facility is to ensure the normal operation of the equipment during emergency operation of the central power supply.
When equipping an object with uninterrupted power supply systems, the main groups of especially responsible energy consumers who need to be connected to a protected power grid are distinguished.
First of all, this includes network equipment that makes up a local computer network - servers, routers, personal computers, etc. Communication equipment (in particular, automatic telephone exchange), life support systems (ventilation and air conditioning systems), various medical equipment, on which the health and life of patients depends, also needs to be safely connected.
Security and security systems (video surveillance, security and fire alarms, emergency lighting and fire extinguishing systems, etc.) also justify connecting to a secure power supply network, since the consequences of failure of such systems can be quite serious.
As for the requirements that apply to the operation of uninterruptible power supply systems, the main ones here are stable and uninterrupted power supply to all consumers powered by the system, maximum protection against voltage surges and high accuracy output current parameters in terms of compliance with existing standards.
Also, when designing and creating an uninterruptible power supply system, it is important to take into account the convenience and efficiency of use, for which modern SHEs have a high degree of work automation.
So, a necessary condition for such a system is a prompt response to the quirks of the power grid and automatic transfer of consumers to work from a secure network. When the parameters of the central power supply are normalized, the system also automatically turns off.
In addition, the possibility of remote administration of the system, if necessary, and the availability of means for informing the administrator about the problems that have arisen, are important.
Structure and principle of operation of the SGE
Since each object has its own characteristics, the configuration of the uninterrupted power supply system in each case is developed for specific conditions.
However, despite the fact that quite often when developing the SGE one has to resort to non-standard solutions, schematically such systems usually look similar.
The main units of the system, first of all, are an autonomous power source (usually a diesel generator), one or more uninterruptible power supplies (UPS), as well as DC power plants. Also, such a safe and reliable solution involves the use of system control and management tools and special software.
During normal operation of the centralized power supply network, the diesel generator set is in standby mode, and the connected equipment is supplied with power through uninterruptible power supplies. The UPS itself in this situation also charges its batteries, acting as a surge protector.
In the event of a failure in the electrical network, the system controller starts the diesel generator, while this occurs, the operation of the connected equipment is carried out from the UPS. After the DGU has reached the set speed, the load is switched to it, while the UPS batteries are again recharged from the diesel engine.
After the problems of the centralized power network are eliminated, the controller switches the equipment from the power supply from the diesel generator set to the external network. During this process, the consumers are also powered by the UPS. Silence of the diesel engine of the unit is also performed automatically, after the equipment has switched to a regular power supply.
The battery life of consumers from the uninterruptible power supply system depends on the operating life of the DGU (the volume of fuel in the tank and its consumption) and the capacity of the UPS batteries. If the fuel resource is almost exhausted, and the centralized power supply has not been restored, the operator must decide to shut down the work of consumers or continue it until the resources of the DGU and the uninterruptible power supply are completely depleted.
In conclusion - a few tips on what should be guided when choosing a hardware manufacturer for equipment emergency power systems.
The main requirements are guaranteed power supply, its high quality and reliability of the supplied equipment, as well as its compliance with domestic standards. Guided by this parameter, it is important to choose serious companies that have weight and authority in the domestic power equipment market as a supplier.
Such firms, moreover, will be able to guarantee you qualified technical support and maintenance of the supplied equipment. Finally, when supplying equipment, such factors as promptness of delivery and acceptable, economically justified prices for products can also be important.
Continuity power supply is not an absolute value in terms of the very quality of the power supply. When designing SBGE (systems of uninterrupted and uninterrupted power supply), two points are always repelled:
– consumers of electricity are divided into groups according to responsibility, i.e. prioritized power supply for loads;
- and in each group the most demanding consumer in terms of power quality is singled out.
This logic defines the requirements for the tolerance of the parameters of the mains, under which the load works without being disconnected. As a result, " uninterruptible power supply system "creates such a network to the load, in which there is no even a short-term deviation of the power supply parameters for allowable load borders.
warranty power supply implies the possibility of a long-term power outage of a technological object only in such a way that this does not lead to an emergency state of the equipment and does not create a danger to people and environment(). V " guaranteed power supply system " Momentary power outages are acceptable, which may be due to switching between power supplies.
In simple words, it is important to understand the following: if there is such a load, a short-term power failure of which leads to the fact that the consumer’s operation algorithm is reset and it is necessary to start unfinished business from scratch, or a power failure can lead to fatal consequences, then such a consumer unequivocally requires uninterrupted power supply. The duration of the autonomous power supply should allow to complete a certain production cycle before it ends. An example of such a load could be equipment in operating rooms of clinics, or data storage equipment.
If a short-term power failure of the load does not lead to the loss of an unfinished production cycle, does not create conditions for catastrophic consequences, and work can be continued from any breakpoint, then such a consumer will require only a guaranteed power supply. An example of such a load is the lighting of rooms, or e. mechanical mill motor.
For a general understanding of the place of uninterruptible and uninterruptible power supply systems in the power supply of objects, one should refer to the requirements of regulatory documents and create your own power supply system no worse than the general requirements.
PUE 7th edition
and ensuring the reliability of power supply
1.2.17. Categories of power receivers in terms of power supply reliability are determined in the process of designing a power supply system based on normative documentation, as well as the technological part of the project.
1.2.18. V With regard to ensuring the reliability of power supply, power receivers are divided into the following three categories.
Electrical receivers I categories - electrical receivers, the interruption of power supply of which can lead to a danger to human life, a threat to the security of the state, significant material damage, disruption of a complex technological process, disruption of the functioning of especially important elements of public utilities, communications and television facilities.
From the composition of electrical receivers of the first category stands out special group electrical receivers, the uninterrupted operation of which is necessary for an accident-free shutdown of production in order to prevent a threat to human life, explosions and fires.
Electrical receivers II categories - electrical receivers, the interruption of power supply of which leads to massive undersupply of products, massive downtime of workers, mechanisms and industrial transport, disruption of the normal activities of a significant number of urban and rural residents.
Electrical receivers III categories - all other electrical receivers that do not fall under the definitions of the first and second categories.
1.2.19. Power receivers of the first category in normal modes must be provided with electricity from two independent mutually redundant power sources, and a break in their power supply in the event of a power failure from one of the power sources can only be allowed for the period of automatic power restoration.
For the power supply of a special group of power receivers of the first category, additional power must be provided from a third independent mutually redundant power source.
As a third independent power source for a special group of power consumers and as a second independent power source for other power consumers of the first category, local power plants, power plants of power systems (in particular, generator voltage buses), uninterruptible power units designed for these purposes, batteries and etc.
If it is impossible to ensure the continuity of the technological process by redundant power supply, or if redundant power supply is not economically feasible, technological redundancy should be carried out, for example, by installing mutually redundant technological units, special devices for trouble-free shutdown of the technological process, operating in the event of a power failure.
Power supply of power consumers of the first category with a particularly complex continuous technological process that requires a long time to restore the normal mode, if there are feasibility studies, it is recommended to carry out from two independent mutually redundant power sources, which are subject to additional requirements determined by the characteristics of the technological process.
1.2.20. Power receivers of the second category in normal modes must be provided with electricity from two independent mutually redundant power sources.
For power receivers of the second category, in the event of a power failure from one of the power sources, power supply interruptions are permissible for the time necessary to turn on the backup power by the actions of the duty personnel or the mobile operational team.
1.2.21. For power receivers of the third category, power supply can be carried out from one power source, provided that power supply interruptions necessary to repair or replace a damaged element of the power supply system do not exceed 1 day.
Thus, it becomes obvious that SSES systems in terms of uninterruptible power supply are aimed primarily at satisfying the needs for the quality and reliability of power supply for consumers of the 1st (first) category and a special group of the first category, and in terms of guaranteed power supply - for consumers of the 2nd (second) category .
Please contact us for more detailed advice or equipment selection.
National feature of domestic power grids - unexpected loss of tension. As a result, the fruits of labor evaporate, hands drop from the bitterness of what happened, and you have to redo all the work anew.
The situation is unpleasant even at home, but if this happens at an enterprise, if the lost data is the annual report of the accounting department, information about existing and potential customers, a database that has been accumulated for more than one year? The damage from downtime of a computer network, data loss, failure of various devices can be very high.
To minimize it, both financially and in terms of reputation, it is necessary to provide for the provision of equipment in the process of designing an information system (IS). guaranteed power supply(GE). The GE system is a subsystem of the enterprise IS.
It consists of the following main elements: input distribution device (ASU), uninterruptible power supplies (UPS), wired network, switching equipment.
Various schemes for building the system are used - distributed, centralized and combined.
You need to start designing a system by determining the needs of the enterprise. (see information system and administrator). The main parameters that need to be determined are: the battery life of the IC and the estimated power of the equipment used. If the estimated power can be calculated unambiguously, then the battery life depends on the tasks. For one enterprise, this is saving data and normal shutdown - 15 minutes is enough. For another, it is support for the main functionality of the IS until the restoration of normal power supply - several days.
For a small company with a small number of employees and equipment, the most acceptable solution would be distributed topology. That is, a local UPS is installed for each piece of protected equipment. The positive aspects of this approach are that if one source fails, all the others remain operational, the system is easily scalable (an additional UPS is purchased for new equipment). An important advantage of such a system will be its low cost - there is no need to install an additional wired network. The disadvantages of this solution include the complexity of management, timely diagnosis and replacement of batteries, user access to the equipment.
For a company with dozens of employees, an acceptable solution is to use centralized topology. In this scheme, a central powerful UPS is used, from which power is supplied to all protected equipment. The main disadvantage of this approach is the need to separate wired networks of general and guaranteed power supply. Well, then only the advantages - high reliability, high noise immunity class, remote administration, automatic information about the status of the UPS and the parameters of the power grid. Significantly increases battery life for high-priority consumers (VP): servers, network routers, office PBXs, etc.
In order to improve reliability, use combined UPS switching scheme: together with the central one, they put a UPS to protect individual groups. In this case, even if one of the elements fails, the system as a whole remains operational. With this option, consumers with high priority must be able to be powered in parallel from two sources. One input is powered from the central UPS, the second from the UPS of the group. Low priority consumers (LP) are powered from one source, depending on the specific project.
In any organization of the POE, it is necessary to provide for the possibility of a quick replacement of the UPS, as well as the organization of temporary work without any or all of the UPS of the system. The cheapness of local UPSs, with a distributed topology, allows you to always have a reserve for replacement. Having a stock of central or group UPS is not always justified, due to their high cost. Therefore, without fail, it is necessary to provide for the possibility of switching (K1, K2), to exclude the UPS from the system and supply power directly.
Another level of GE provision is the use of two external inputs (V1, V2) of power supply from different substations and an autonomous generator (GEN). Automatic switching between the inputs and the generator is carried out by the ASU. If one of the inputs fails, it switches to the other, if both fail, it switches to the generator.
| Scheme combined system GE |
The GE system maintenance process includes:
- replacement of failed UPS
- cleaning equipment from dust
- battery diagnostics and replacement
- communicating to users the rules for using the GE system and monitoring their compliance
- promptly informing those responsible about power outages
- test shutdowns of external power supply sources
- generator maintenance
One of the IS subsystems is an uninterruptible power supply system built on uninterruptible power supplies. Distributed, centralized and combined topologies are possible. The most important parameters of the GE system are the autonomous operation time of the IC and the power consumed by its equipment. These parameters are determined based on the needs of the enterprise and its financial capabilities.
Oddly enough, but the demand for devices that ensure the smooth operation of computer systems is growing not only in countries with so-called unstable economies, but also in the West. However, the reasons for this growth are somewhat different. If in highly developed countries maintaining the stability of power supply parameters comes to the fore, then, say, in our country, this is the presence of it as such. The issues of a reasonable choice and the correct construction of uninterruptible power supply systems (SGE) in the relevant documents still largely remain unresolved.
Before moving on to recommendations based on practice, we will consider in sequence the basic concepts related to the power supply of a LAN, such as power quality, reliability, an uninterrupted power supply system, power supply networks and their types.
Reliability of power supply
The concept of reliability in electrical engineering can be interpreted as the property of an object to maintain within the established limits during operation the values of all parameters that characterize the ability to perform the required functions in given modes and conditions of use, maintenance, repair, storage and transportation. According to the current rules for ensuring the reliability of power supply, power receivers are divided into three categories and a special group.
Category I power receivers include devices whose interruption in power supply can lead to a danger to human life, significant damage to the national economy, damage to expensive equipment, disruption of a complex technological process or the functioning of critical facilities. Their power supply must be carried out from two mutually redundant power sources (PS) with a permissible interruption for the time of automatic power restoration.
From category I, a special group of electrical receivers stands out, the uninterrupted operation of which is necessary for an accident-free shutdown of production. For their power supply, additional power supply from a third independent mutually redundant power supply should be provided. Its role can be performed by gasoline (BES), diesel (DES) power plants or other energy generating sources.
The electrical receivers of categories II and III include less critical installations, and their consideration is not of interest to us.
It should be noted that the automatic switching on of the reserve (ATS), which makes it possible to restore power to category I and even a special group power receivers in 3-30 seconds, only leads to the resumption of power supply, but not to the continuation of their normal functioning. Thus, the categories of reliability determined by the current guidelines do not solve the problem of providing LANs with electricity of the required quality. Therefore, it is proposed to introduce an additional group, calling it "critical group of power receivers of category I to the reliability of power supply". In this case, we will proceed from the fact that devices belonging to the critical group must withstand a power interruption of up to 20 ms.
According to the operating modes, these power receivers can be divided into two types: devices with a normal operating mode and with a special one. The former should be provided with protection against power failures during the work shift (day) or the time required to complete the corresponding technological cycle; the second - protection against power failures 24 hours a day and 365 days a year. The latter include devices that provide continuous technological process in real time, when interruption is unacceptable, or those power receivers, the failure of which leads to the loss of information that is difficult to recover or to large financial losses.
For the power supply of consumers of the critical group, it is recommended to use the SHE as part of an uninterruptible power supply unit (UPS) and an autonomous power source in the form of a DES or BES. The building should provide for electrical rooms with the installation of introductory and distribution boards (electric panel), rooms for UPS and DPP. At the same time, the supply and distribution lines of power, lighting and computer networks must be separated with the obligatory formation of an autonomous power supply network for LAN consumers.
Uninterruptible power supply system
Let us define an uninterrupted power supply system as a set of devices and circuit solutions designed to provide uninterrupted power supply of the required quality to critical group power receivers in all network operation modes (normal, emergency or preventive maintenance of nodes and blocks included in the system). Note that the SGE is the most important and integral part of common system power supply of the building and ensures the necessary reliability of the entire circuit. The SGE usually includes ATS facilities, power switching devices of an electrical panel, a distribution network made according to a special scheme, UPS, DES, an autonomous electrical network, as well as lightning protection and grounding devices.
Power supply networks and their types
Currently, there are several ways to implement power supply networks to power critical group electrical receivers.
General purpose network(conventional power supply network of the building) - a one- or three-phase distribution network in which all electrical receivers are powered from one main shield or line with a neutral (protective) conductor connected to the main ground loop of the building. In our opinion, the described network organization is unacceptable for designing a LAN, however, due to the fact that it does not contradict the current regulatory documents, such networks continue to appear in the decisions of most design institutes.
Dedicated LAN(performed without additional installation distribution network) - a scheme when LAN electrical receivers are connected to one dedicated phase of a three-phase main shield or line, and all other electrical receivers are connected to two other phases. To protect LAN electrical receivers, UPSs are usually placed between the main shield and the dedicated phase. This way of networking is only the first step in separating the power supply of the LAN to allow connection of the UPS - and no more. The described organization of a distribution network for a large LAN is not recommended.
Shared LAN(additionally mounted network during reconstruction) - a construction method in which LAN electrical receivers are powered by a single- or three-phase radial-backbone network, separated from the rest of the general-purpose network. The input feeders of the divided network are connected directly to the main distribution (input) device of the building. To protect LAN electrical receivers, UPSs are usually placed at switchboards in the nodes of a divided network. This method of organizing the power supply network for LAN electrical receivers can be fully justified, and its cost practically corresponds to the cost of an autonomous network.
Autonomous LAN power supply network(additionally mounted during reconstruction or new construction) - an installation scheme in which LAN electrical receivers are powered by a five-wire radial-main network, galvanically separated from the general-purpose network. Usually it is performed on the basis of the UPS, which has an output isolating transformer with a star-type secondary winding, the neutral of which is connected to a special process ground loop with resistance R =< 0,5 Ом.
Of the four types of networks listed above, only an autonomous LAN power supply network makes it possible to supply electrical consumers with electrical energy of the required quality by eliminating stray, pulsed and other currents in neutral conductors.
Circuit solutions SGE
At present, two main SHE schemes are being practically implemented: distributed and centrally mixed. For all newly built or reconstructed facilities, the most suitable solution is a centralized-mixed LAN protection scheme. In cases where the reconstruction of the power supply system is not performed, or with significant technical difficulties in implementing the centralized-mixed protection scheme, it is permissible to implement a distributed LAN protection scheme as a temporary solution.
Consider the scope, advantages and disadvantages of the distributed protection scheme. It can be recommended for a small-scale LAN (20-40 workplaces) within one or more floors of a building. At the same time, on-line architecture UPS with a standard set of batteries (for 20-30 minutes of maintaining power supply at 100% load) and a common autonomous backup power source with automatic start in case of loss of city power supply and an ATS device are used. Recommended scheme — shared network.
The advantages of a distributed protection scheme include:
- ease of installation and extension;
- rational planning of funds for the purchase of ABP;
- the ability to maneuver in the distribution of ABP;
- lack of requirements for special training of personnel.
- relatively high cost of protecting one workplace;
- low level of protection quality and low service capabilities;
- the need, when choosing a UPS, to lay a power reserve for the starting currents of the equipment;
- the complexity of centralized management;
- lack of flexibility in the use of energy from the batteries of all UPSs;
- equipment vulnerability due to availability of UPS.
Implementation of the centralized-mixed LAN protection scheme is possible in at least two ways. In the first one, protection of all electronic equipment is carried out using a central powerful UPS of on-line architecture with a standard set of batteries for 15–30 minutes of maintaining 100% load and an autonomous backup power supply with automatic start and an ATS device. At the same time, LAN electrical receivers of the critical group with normal operation are additionally protected by less powerful UPS located nearby. The recommended total power of the sources is 15–80 kV*A, and in some cases even more. The method of execution is an autonomous network.
This option has the following advantages:
- all LAN equipment is constantly connected to a highly stable voltage source;
- overvoltage, electromagnetic interference and voltage pulses in external networks do not affect LAN equipment;
- if necessary, autonomous operation from the DPP is carried out, the duration of which is limited only by the capacity of the fuel tank;
- ample opportunities are provided for using the energy of the central storage battery (a significant increase in the operating time from the UPS of the most critical receivers when less critical ones are turned off in an emergency).
In the second option, centralized protection of all electronic equipment is carried out using the parallel connection of several (line) on-line architecture UPS and an autonomous backup power source with automatic start in case of power failure from the city power grid and ATS. It is recommended in the presence of electrical receivers of a critical group with a special mode of operation. At the same time, such devices are additionally protected by less powerful UPS located nearby. The recommended total load power is from 80 kV * A and above, the execution method is an autonomous network.
The advantages of the second option include:
- permanent connection of LAN equipment to a highly stable voltage source;
- no impact on LAN equipment of overvoltage, electromagnetic interference, voltage pulses in external networks and internal general-purpose networks;
- increasing the reliability of the system as a whole (in the event of failure of one of the UPSs) by performing repair work without interrupting the power supply in the autonomous network;
- control system application parallel work, which makes it possible to change the total power of operating UPS by turning on / off one or more of them;
- the use of the energy of the central storage battery, which makes it possible to turn off low-responsibility electrical receivers in an emergency.
- design, supply, installation, maintenance of the SGE must be carried out comprehensively, taking into account the parameters of all the elements included in it, mutually agreed operating modes and the maximum possible unification;
- Autonomous power supply circuit for UPS LAN devices must have an output isolating transformer with a star-type secondary winding, the neutral of which is connected to a special circuit of the technological grounding device with R =< 0,5 Ом. При этом необходимо, чтобы распределительные щитки автономной сети имели защиту от поражения electric shock according to IEC 439-1-85 or GOST 22789-94;
- the scheme of centralized-mixed protection of the SGE should include a bypass cabinet (SB) and a diesel generator load control cabinet (SHUN DG) to be able to perform repair and maintenance work at the DPP and adjust its operation with the UPS without interrupting the power supply;
- ATS switching devices must have mechanical interlocks against simultaneous switching on;
- the autonomy of the LAN power supply should be ensured not only by separating power electrical networks, but also by eliminating connections between ground loops that may occur through information channels;
- information (overhead) LAN lines laid outside the building or between buildings must be protected by special surge suppression devices.
Practical experience shows that only an autonomous network can fully provide a reliable and high-quality power supply to the LAN.