TIP Application Manual Part 2 Draft Planning
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(2) Contents 1. Planning with Totally Integrated Power. 1.1. Introduction. 1/2. 1.2. Draft Planning (System and Integration Planning). 1/3. 6.3. Requirements of the Switchgear in the Three Circuit Types. 6/11. 6.4. Container Solutions. 6/14. 7. Busbar Trunking Systems, Cables and Wires. 2. Power System. 2.1. Overview. 2/2. 2.2. Dimensioning of Power Distribution Systems. 2/10. 2.3. System Protection and Safety Coordination. 2/14. 7.1. Busbar Trunking Systems. 7/2. 2.4. Protection Equipment for Low-Voltage Power Systems. 2/20. 7.2. Cables and Wires. 7/10. 2.5. Selectivity in Low-Voltage Systems. 2/41. 2.6. Protection of Capacitors. 2/52. 2.7. Protection of Distribution Transformers. 2/53. 8. Subdistribution Systems. 8.1. General. 8/2. 8.2. Configuration. 8/2. 8.3. Selectivity and Back-up Protection. 8/3. 8.4. Small Distribution Boards and. 2.8. Protection of Technical Building Installations – Lightning Current and Overvoltage Protection. 2/62. 3. Medium Voltage. 3.1. Introduction. 3/2. 3.2. Basics of Switchgear. 3/3. 3.3. Requirements on Medium-Voltage Switchgear. 3/7. 3.4. Siemens Medium-Voltage Switchgear. 3/9. 3.5. From Medium-Voltage Switchgear to Turnkey Solutions. 3.6. 3/25. Protection of Power Distribution Systems and Switchgear. Wall- or Floor-Mounted Distribution Boards. 8/6. 8.5. Circuit Protection Devices. 8/9. 9. Power Consumers. 9.1. Starting, Switching and Protecting Motors. 9/2. 9.2. Lighting. 9/8. 9.3. Elevator Systems. 9/19. 3/28. 10 Ease of Operation, Safety and Control Engineering. 4. Transformers. 4.1. Distribution Transformers. 4/2. 10.1 Power Management with SIMATIC powercontrol. 10/2. 4.2. Control and Isolating Transformers. 4/6. 10.2 Building Management System. 10/7. 5. Power Generation. 5.1. Grid-Connected Photovoltaic (PV) Systems. 5/2. 5.2. Basis for the Use of UPS. 5/5. 6. Low Voltage. 6.1. Low-Voltage Switchgear. 10.3 Energy Automation for the Industry. 10/14. 10.4 Safety Lighting Systems. 10/20. 10.5 Robust Remote Terminal Unit for Extreme Environmental Conditions (SIPLUS RIC). 11 Appendix. 6.2. 6/2. Protective and Switching Devices in the Low-Voltage Power Distribution. 6/9. 10/27.
(3) Conversion Factors and Tables. Volume Non-metric SI unit unit. Pressure. Volume flow rate. Non-metric SI unit unit. Non-metric SI unit unit. Non-metric SI unit unit. 3 1 1 in cm3. 3 3= 16.387 0.061 incm 0.034 fl oz. 3 1 1 ft dm3. 3 3 28.317 61.024dm in3 == 0.028 m. 1 1 l/s gallon/s l/h 1 gallon/min. 0.264 3.785 gallons/s l/s 3/h = 227 l/h 0.0044 0.227 mgallons/min. 3 1 = yd 1l. 0.765 0.035 m ft3 = 1.057 quarts =. /h 1m ft33/s. 1 fl oz. 3 0.264 gallons 2.114 pint 29.574 cm=. 4.405 gallons/min = 101.941 m3/h 0.589 ft33/min = 0.0098 ft3/s 1.699 m /h. 1 quart m3. 3 = 0.946 l 0.946 0.629 dm barrels. 1 ft3/min Non-metric unit SI unit 1 gallon/s 1 l/s 1 gallon/min 1 l/h 1 ft3/s 1 m3/h 1 ft3/min. 1 pint Non-metric unit 1 gallon. 0.473. dm3. 3.785. dm3. = 0.473 l SI unit = 3.785 l. 33 dm. m3. 1 ft3. 158,987 16.387 cm = 1.589 = 159 l 28.317 dm3 = 0.028 m3. 1 yd3 SI unit 1 fl oz. 0.765 m3 Non-metric unit 29.574 cm3. cm3 1 quart. 0.061 dm in33==0.034 0.946 0.946 fll oz. 1 barrel 1 in3. dm3. 1 pint. 61.024dm in33 = = 0.473 l 0.473. Force. = gallon 1l 1 1 barrel. 0.035 dm ft3 3==1.057 = 3.785 3.785quarts l 2. 1 14 pint = 0.264 gallons 3 3 158,987 dm = 1.589 m. Non-metric SI unit unit. 1 m3. = 159 lbarrels 0.629. 1 tonf Non-metric unit SI unit 1 lbf 1 1N kgf. Velocity Non-metric SI unit unit m/s 1 ft/s km/h 1 mile/h SI unit Non-metric unit 1 ft/s m/s 1 1 mile/h km/h 1. lbf 1N 1 kN kgf 1. Non-metric SI unit unit 3.281 m/s ft/s ==2.237 0.305 1,098 miles/h km/h 0.911 ft/s 0.447 m/s==0.621 1,609 miles/h km/h Non-metric SI unit unit 3.281 m/s ft/s ==2.237 0.305 1,098 miles/h km/h 0.911 ft/s = 0.621 0.447 m/s = 1,609 miles/h km/h. 1 1 kN tonf. Non-metric SI unit unit 1 lbf Nmin 1 lbf ft. 1 lbf ft. 28.35 0.035 g oz. 1 lb kg. 0.454 kg==35.27 453.6oz g 2.205 lb. 1 sh t ton. 0.907 t =ton 907=.22,205 kg lb 1.102 sh. SI unit Non-metric unit 1g 1 oz 1 kg 1 lb 1t 1 sh ton. SI unit Non-metric unit 4.448 N 0.225 9.807 lbf N = 0.102 kgf. 0.100 9.964 tonf kN. Non-metric unit SI unit 0.035 oz 28.35 g 2.205 lb = 35.27 oz 0.454 kg = 453.6 g 1.102 sh ton = 2,205 lb 0.907 t = 907.2 kg. 154.443 bar = 2 unit 157.488 kgf/cmSI. 1 in HG SI unit 1 psi bar 2 11 lbf/ft = 105 pa = 102 kpa 1 lbf/in2. Non-metric 0.034 bar unit 0.069 bar 29.53 xin10 Hg = = -4 bar 4.788 14.504x psi 4.882 10-4=kgf/cm2 2088.54 lbf/ft2 = 0.069 = 0.070 kgf/cm2 2= 14.504bar lbf/in 2 1.072 = 1.093 = kgf/cm2 0.932 bar tonf/ft -3 tonf/in2 6.457 x 10 154.443 bar = 2 (= 1.02 157 .488kgf/cm kgf/cm2). 1 tonf/in2. Energy, y work Non-metric SI unit unit. Non-metric SI unit unit 0.113 = 0.012 kgflbf m ft 8.851Nm lbf in = 0.738 (= 0.102 m) kgf m 1.356 Nmkgf = 0.138 Non-metric SI unit unit 8.851Nm lbf in = 0.738 0.113 = 0.012 kgflbf m ft (= 0.102 kgf m) 1.356 Nm = 0.138 kgf m. Moment of inertia J. Non-metric SI unit unit lbf m ft22 1 kg. Non-metric SI unit unit 2 1 1 kg lbf m ft2. 6J 0.746 kWh = 2.655 2.684 kgf x 10m 1.341 hp h= = 2.737 x 510J5 kgf m 3.6 x 10. -7 hp h = 0.138 3.725 kgf x 10m 0.738 ft lbf = 1.055 kJ = 1055.06 J 1 Btu -4 Btu 9.478 x 10 (= 0.252 kcal) (= 2.388 x 10-4 kcal) Non-metric 1 kgf m 3.653 x 10-6 hp h = SI unit unit 7.233 ft lbf 1.341 hp h = 2.655 kgf m 1 kWh Non-metric = 3.6 x 105 J SI unit unit 1J 3.725 x 10-7 hp h = 0.746 kWh = 2.684 x 106 J 1 hp h 0.738 ft lbf =5 kgf m = 2.737 x 10 9.478 x 10-4 Btu 0.138 kgfxm10-4 kcal) 1 ft lbf (= 2.388. kgf m 1 Btu. Numerical value equation:. Non-metric SI unit unit. 1 Jft lbf. Non-metric SI unit unit. 1 oz g. 1 tonf/in2 Non-metric unit. 9.807 tonf N 0.100 9.964 kN. Torque, moment of force. Nmin 1 lbf. Non-metric SI unit unit. 1 tonf/ft2. 1 lbf/in2. 1 tonf/ft2. Non-metric SI unit unit 4.448 lbf N = 0.102 kgf 0.225. Non-metric SI unit unit 0.034 29.53 bar in Hg = 14.504bar psi = 0.069 2088.54 lbf/ft2 = 4.788 x 10-4 bar = 14.504 lbf/in2 = 2 4.882 x 10-4 kgf/cm 2 0.932 tonf/ft = -3 2 0.069 tonf/inkgf/cm2 6.457 bar x 10= 0.070 2) (= 1.02 kgf/cm 1.072 bar = 1.093 kgf/cm2. 1 in barHG 105 pa 1= psi = 102 kpa 1 lbf/ft2. 1 hp h kWh. Non-metric SI unit unit. Mass, weight. SI unit Non-metric unit 3.785 l/s 0.264 gallons/s 0.227 m3/h = 227 l/h 0.0044 gallons/min 101.941 m3/h 4.405 gallons/min = 3/h 1.699 m 0.589 ft3/min = 0.0098 ft3/s. Non-metric SI unit unit. J=. GD2 = Wr 2 4. Non-metric SI unit unit 0.04214 kg2 m2 23.73 lb ft Non-metric SI unit unit 2 23.73 lb ft 0.04214 kg m2. 1.055 kJ = 61055.06 3.653 x 10hp h = J (= 0.252 kcal) 7 .233 ft lbf.
(4) Conversion Factors and Tables. Conductor cross section. Equivalent metric CSA. [mm2]. [mm2]. 50.00. 10.550. 7. 13.300. 6. 16.770. 5. 21.150. 4. 26.670 33.630. 3 2. 42.410. 1. 53.480. 1/0. 70.00. 67.430. 2/0. 95.00. 85.030. 3/0. 120.00 150.00 185.00. 107.200 126.640 152.000. 4/0 250 MCM 300. 202.710. 400. 240.00. 253.350. 500. 300.00. 304.000 354.710 405.350 506.710. 600 700 800 1000. 400.00 500.00 625.00. 6m. 11 m. 9 8. 9m. 6.630 8.370. 7m. 11 10. 5m. 4.170 5.260. 13 m. 7m 12. 5m. 13. 3.310. 4m. 2.620. 2m. 15 14. 3m. 35.00. 1.650 2.080. 1m. 25.00. 16. M 1 : 100. 16.00. 17. 1.310. 3m. 10.00. 1.040. 2m. 6.00. 18. 1m. 4.00. 19 AWG. 0.832. 1m. 2.50. 0.653. M 1 : 50. 1.50. AWG or MCM. M 1 : 20. 0.75. 15 m. American Wire Gauge (AWG). 3m. Metric cross sections acc. to IEC. 8m. Conductor cross sections in the Metric and US System.
(5) Conversion Factors and Tables. Specific steam consumption Non-metric unit 1 lb/hp h SI unit 1 kg/kWh. SI unit 0.608 kg/kWh Non-metric unit 1.644 lb/hp h.
(6) Planning with Totally Integrated Power. chapter 1 1.1 Introduction 1.2 Draft Planning (System and Integration Planning).
(7) 1 Planning with Totally Integrated Power 1.1 Introduction Today, the focus is on cost of investment, when power supply systems for commercial, institutional and industrial building projects are planned. Operating and energy costs, on the other hand, may not be neglected, as they can have a lasting effect on the total cost balance across the building’s life cycle. Investigations of the Scientific Council of the German Federal Government on Global Environmental Change found in 2003 that world consumption of primary energy is going to double by 2050 (assumption: world population growth to 9 to 10 billion people). Among other consequences, this would mean that energy would become noticeably more expensive. If sustainable building management and. optimal utilization of resources is considered in the planning stage already, an important step will have been made toward the minimization of a building’s operating costs, and thus toward its longterm value increase. So electrical engineering consultants are entrusted with the responsible task of designing power supply systems under the aspects of operational safety and energy efficiency. Services rendered must be in accordance with the generally accepted rules of good practice. This means that implementing orders, administrative regulations, relevant IEC, European (EN) and national DIN standards as well as the general building inspection certificates and general building permits must also be observed across building contract sections in the planning.*. * Also see Chapter 11, A1, Standards, Regulations and Guidelines. Concepts like Totally Integrated Power (TIP) now provide support for increasingly complex engineering tasks. They facilitate planning with integrated solutions for power distribution and efficient engineering tools. Totally Integrated Power with its wellmatched components and optimized interfaces offers everything that can be expected from a future-oriented power distribution system. Very good engineering support is also rendered by the TÜV-approved and certified dimensioning tool SIMARIS design. Using SIMARIS design for dimensioning electrical power distribution systems in commercial, institutional and industrial buildings produces easy, fast and safe results. Further information on Totally Integrated Power SIMARIS design can be obtained on the Internet at www.siemens.com/tip. Fig. 1.1/1: Safety, environmental compatibility and profitability of power supply and distribution are demanding challenges to the planning of modern building and infrastructure projects. 1/2. Totally Integrated Power by Siemens.
(8) Planning with Totally Integrated Power. 1.2 Draft Planning (System and Integration Planning) Building upon the concept drafted in the “Preliminary Planning” phase 2, power distribution must be planned in detail in the “Draft Planning” phase 3. The Application Manual “Totally Integrated Power – Draft Planning” provides technical assistance and information on components for technical installations in buildings with a focus on “electrical power supply.” Services in detail, which are an integral part of “Draft Planning”, are defined in the Regulation of Architects' and Engineers' Fees (HOAI) in Germany. Based upon preliminary planning results, Draft Planning represents the definite planning concept including all components specified. In projects requiring a permit, the Draft Planning is the basis for the subsequent Approval Planning phase.. Basic services Elaboration of the planning concept (step by step preparation of drawings) that takes into account requirements concerning aspects of urban development and design, functions, technology, building physics, profitability, energy management (e.g. regarding efficient power utilization and the use of renewable energies) and landscape ecology, and integrates contributions of other parties involved in the planning, until a complete draft is presented Integration of services rendered by other experts involved in the planning Description of the building project including an explanation of compensation and substitution measures as stipulated by the impact regulation under nature protection law Graphic presentation of the overall draft, e.g. elaborated, complete preliminary outline and/or outline drawings (scale. depending on the size of the building project; for outdoor facilities at scales of 1:500 to 1:100, detailing in particular the improvements for biotope functions, preventive, protective, care and development activities as well as on differentiated planting; for space enclosing developments: in scales of 1:50 to 1:20, in particular with details of wall design as well as color, light and material design; if necessary including detailed plans of repetitive groups of enclosed space; negotiations with public authorities and other experts involved in planning as to whether an official approval can be obtained Cost calculations in compliance with DIN 276 or according to statutory provisions for cost calculations of residential dwellings Summary of all draft documents Cost controlling by a comparison of the cost calculation with the cost estimate. Special services. Table 1.2/1:. Overview of the planner’s major tasks in the first two project stages according to the HOAI (Regulation of Architects' and Engineers' Fees) (excerpt). Analysis of alternatives/variants and their assessment including an investigation into costs involved (optimization) Profitability calculation Cost calculation by setting up quantity structures or a catalog of components Elaboration of special measures for the optimization of the building or building sections, which exceed the normal range of. engineering services, on the reduction of energy consumption as well as pollutant and CO2 emissions, and for the use of renewable energies in coordination with other experts involved in planning. The normal measure for energy saving activities means the fulfillment of requirements set by statutory provisions and generally accepted rules of good practice.. 1/3. 1.
(9) 1/4. Totally Integrated Power by Siemens.
(10) Power System. chapter 2 2.1 Overview. 2.5 Selectivity in Low-Voltage Systems. 2.2 Dimensioning of Power Distribution Systems. 2.6 Protection of Capacitors. 2.3 System Protection and Safety Coordination. 2.7 Protection of Distribution Transformers. 2.4 Protection Equipment for Low-Voltage Power Systems. 2.8 Protection of Technical Building Installations – Lightning Current and Overvoltage Protection.
(11) 2 Power System 2.1 Overview 2.1.1 System Configurations Table 2.1/1 illustrates the technical aspects and influencing factors that should be taken into account when electrical power distribution systems are planned and network components are dimensioned. Simple radial system (spur line topology) All consumers are centrally supplied from one power source. Each connecting line has an unambiguous direction of energy flow. Radial system with changeover connection as power reserve – partial load: All consumers are centrally supplied from two to n power sources. They are rated as such that each of it is capable. of supplying all consumers directly connected to the main power distribution system (stand-alone operation with open couplings). If one power source fails, the remaining sources of supply can also supply some consumers connected to the other power source. In this case, any other consumer must be disconnected (load shedding).. power sources or more, other supply principles, e.g. the (n-2) principle would also be possible. In this case, these power sources will be rated as such that two out of three transformers can fail without the continuous supply of all consumers connected being affected. Radial system in an interconnected grid Individual radial networks in which the consumers connected are centrally supplied by one power source are additionally coupled electrically with other radial networks by means of coupling connections. All couplings are normally closed.. Radial system with changeover connection as power reserve – full load: All consumers are centrally supplied from two to n power sources (standalone operation with open couplings). They are rated as such that, if one power source fails, the remaining power sources are capable of additionally supplying all those consumers normally supplied by this power source. No consumer must be disconnected. In this case, we speak of rating the power sources according to the (n-1) principle. With three parallel. Depending on the rating of the power sources in relation to the total load connected, the application of the (n-1) principle, (n-2) principle etc. can ensure continuous and faultless power supply of all consumers by means of additional connecting lines.. LV- side system configurations. 1 Low cost of investment. Radial system with changeover connection as power reserve. Simple radial system. Quality criterion. 2. 3. 4. Partial load 5. •. 1. 2. 3. 4. Full load 5. 1. 2. • •. High reliability of supply. •. •. Great voltage stability. •. •. •. 5. 1. 2. 3. •. Easy and clear system protection High adaptability. •. •. •. 5. 1. 2. •. •. •. 5. •. •. • • •. •. 4. •. •. •. 3. •. • •. •. 4. Radial system with power distribution via busbars. •. •. •. •. 4. •. Easy operation. •. 3. •. Low power losses. Low fire load. Radial system in an inter- connected grid. •. •. • •. •. Rating: very good (1) to poor (5) fulfillment of a quality criterion Table 2.1/1:. 2/2. Exemplary quality rating dependent on the power system configuration. Totally Integrated Power by Siemens.
(12) Power System. The direction of energy flow through the coupling connections may vary depending on the line of supply, which must be taken into account for subsequent rating of switching/protective devices, and above all for making protection settings. Radial system with power distribution via busbars In this special case of radial systems that can be operated in an interconnected grid, busbar trunking systems are used instead of cables. In the coupling circuits, these busbar trunking systems are either used for power transmission (from radial system A to radial system B etc.) or power distribution to the respective consumers.. 2.1.2 Power Supply Systems according to the Type of Connection to Ground TN-C, TN-C/S, TN-S, IT and TT systems The implementation of IT systems may be required by national or international standards. For parts of installations which have to meet particularly high requirements regarding operational and human safety (e.g. in medical rooms, such as the OT, intensive care or post-anaesthesia care unit) For installations erected and operated outdoors (e.g. in mining, at cranes, garbage transfer stations and in the chemical industry). Depending on the power system and nominal system voltage there may be different requirements regarding the disconnection times to be met (protection of persons against indirect contact with live parts by means of automatic disconnection).. TN-C. Characteristics. 1. TN-C/S 2. 3. 1. 2. Low cost of investment. •. •. Little expense for system extensions. •. •. Any switchgear/protective technology can be used. •. • •. Ground fault detection can be implemented. •. TN-S 3. 1. 2. IT system TT system 3. 1. 2. •. 3. 1. 2. 3. • •. •. •. •. •. •. •. • • •. Fault currents and impedance conditions in the system can be calculated. •. •. •. •. •. Stability of the grounding system. •. •. •. •. •. •. •. •. •. •. •. High degree of operational safety. •. •. High degree of protection. •. •. High degree of shock hazard protection. •. •. •. •. •. High degree of fire safety. •. •. •. •. •. Automatic disconnection for protection purposes can be implemented. •. • •. EMC-friendly. •. •. •. •. •. •. •. Equipment functions maintained in case of 1st ground or enclosure fault. •. •. • •. •. Fault localization during system operation. •. •. • •. •. • •. •. Reduction of system downtimes by controlled disconnection. • 1 = true. •. 2 = conditionally true. 3 = not true. Table 2.1/2: Exemplary quality rating dependent on the power supply system according to its type of connection to ground. Power systems in which electromagnetic interference plays an important part should preferably be configured as TN-S systems immediately downstream of the point of supply. Later, it will mean a comparatively high expense to turn existing TN-C or TN-C/S systems into an EMC-compatible system. The state of the art for TN systems is an EMC-compatible design as TN-S system.. Further information Power system engineering: Siemens AG (Ed.): TIP Application Manual Establishment of Basic Data and Preliminary Planning, 2006, Chapters 4.1 and 7 EMC: Siemens AG (Ed.): TIP Application Manual Establishment of Basic Data and Preliminary Planning, 2006, Chapter 7 Design of the low-voltage main distribution system Siemens AG (Ed.): TIP Application Manual Establishment of Basic Data and Preliminary Planning, 2006, Section 5.8 Motors see Chapter 9 in this manual. 2/3. 2.
(13) Checklist Important electrical parameters of the higher-level medium-voltage systems Local supply network operator. ......................................................................... Point of supply: Under responsibility of local supply network operator / customer Neutral-point connection of power system. Maximum short-circuit current Ik" max Alternatively, maximum system short-circuit rating Sk" max Minimum short-circuit current Ik" min Alternatively, minimum system short-circuit rating Sk" min. ........................................................................ . low resistance grounded. . compensated. . isolated. ........................ kA ........................ MVA ........................ kA ........................ MVA. Data of higher-level medium-voltage protection Current transformer Iprim. ........................ A. Isec. ........................ A. Type of protection relay applied: Thermal overload protection available? Type of characteristic curve:. yes. no. inverse-time-delayed. definite-time-delayed. Setting zone Ith. ........................ A / time constant ........................ min. Setting zone I >. ........................ A / t > ........................ s. Setting zone I >>. ........................ A / t >> ........................ s. Note: For preparing a comprehensive, end-to-end protection concept, the precise data of the higher-level medium-voltage protection applied are required, so that the lower-level low-voltage protection system can be adapted in accordance with the MV protection settings. Further information on medium-voltage switchgear: Siemens AG (Ed.), TIP Application Manual - Establishment of Basic Data and Preliminary Planning, 2006, Section 5.1. 2/4. Totally Integrated Power by Siemens.
(14) Power System. Checklist Important electrical parameters of transformers Uprim / Usec Rating Rated short-circuit voltage ukr. ........................ kV ........................ kVA ........................ %. Winding losses Pk. ........................ kW. No-load losses P0. ........................ kW. Overload capability (vented/unvented transformers). ........................ %. Power reserve. ........................ %. Note: The rated short-circuit voltage ukr is a measure for the amount of voltage to be applied at the primary side in order to reach the rated current level, when the secondary-side winding is shorted. ukr is a measure for the transformer’s short-circuit power. As a rule, the higher ukr, the lower the short-circuit power. High-quality transformers (e.g. GEAFOL) are characterized by reduced winding and no-load losses, which should be taken into account for a profitability evaluation. if transformers with cross-flow fans are used, their overloadability must be considered for rating the feeding lines, switching devices and their protection settings. Short-circuit current determination: The level of short-circuit current which a transformer can supply is independent of its design with or without cross-flow ventilation. The magnitude of the short-circuit current is solely determined by the rated short-circuit voltage ukr . Technical considerations for the connection of motor loads: to determine regenerative feedback from motors in the event of a short circuit, the sum total of installed motor loads is required. Further information on distribution transformers: Siemens AG (Ed.), TIP Application Manual - Establishment of Basic Data and Preliminary Planning, 2006, Section 5.2. 2/5. 2.
(15) Checklist Important electrical parameters of generators Main use: No-break standby generating set*. . yes. . no. Quick-starting standby generating set*. . yes. . no. Safety power supply*. . yes. . no. Nominal voltage Rating Subtransient reactance xd" Initial symmetrical short-circuit current Ik". ........................ V ........................ kVA ........................ % ........................ kA. 1-phase sustained short-circuit current Ik1D. ........................ A. Available for period t. ........................ s. 3-phase sustained short-circuit current Ik1D. ........................ A. Available for period t. ........................ s. R/X ratio. ......................... * Safety power supply in compliance with IEC 60364-7-710, DIN VDE 0100-710 and -718; designed as no-break standby generating set according to customer specifications. Note: Normally, generators can only supply the initial symmetrical short-circuit AC current Ik" for a period of few milliseconds. Therefore, the sustained short-circuit currents which the generator can carry over a longer period of time are relevant for the protective settings of devices using time-delayed short-circuit releases. Above data must be obtained from the equipment manufacturer. Rating of switching/protective devices for generator operation: selective response of these switching/protective devices can be expected if the rating of the largest consumer connected is less than 1/3 of the generator output. What is important for emergency lighting is the full compliance with standards from the point of supply to the consumers (also see Section 10.4 “Safety Lighting Systems”). Further information on generators: Siemens AG (Ed.): TIP Application Manual - Establishment of Basic Data and Preliminary Planning, 2006, Section 5.7. 2/6. Totally Integrated Power by Siemens.
(16) Power System. Checklist Important electrical parameters of a combined heat and power plant Main use: Safety power supply*. . yes. . no. Redundant power supply. . yes. . no. Nominal voltage Rating Subtransient reactance xd" Initial symmetrical short-circuit current Ik". ........................ V ........................ kVA ........................ % ........................ kA. 1-phase sustained short-circuit current Ik 1D. ........................ A. Available for period t. ........................ s. 3-phase sustained short-circuit current Ik 1D. ........................ A. Available for period t. ........................ s. R/X ratio. ......................... * Safety power supply in compliance with IEC 60364-7-710, DIN VDE 0100-710 and -718; designed as no-break standby generating set according to customer specifications. Note: Normally, combined heat and power plants are modularly designed and supply electricity and heat. They are based on the principle of combined heat and power generation. The output of a combined heat and power plant is usually designed as such that only a part of the maximum heating energy demand of the connected consumers is covered when the plant is operated under full load. These co-generating plants are operated on a heat-demand basis. What is important for emergency lighting is the full compliance with standards from the point of supply to the consumers (also see Section 10.4 “Safety Lighting Systems”).. 2/7. 2.
(17) Checklist Important electrical parameters of uninterruptible power supplies (UPS) Nominal voltage Rating. ........................ V ........................ kVA. Load power factor. ......................... UPS factor. ......................... Static or dynamic system. ......................... Time curve of short-circuit currents (1-phase, 2-phase, 3-phase). ......................... Interconnection of primary circuits. ......................... Availability of internal protection equipment in the primary circuits. ......................... Switching/protective response of internal protection equipment. ......................... Internal operational response in the event of a short circuit. ......................... Note: Uninterruptible power supplies for power supply systems are available in ratings of about 5 kW up to several 100 kW. Their rating basically depends on the load carrying capability of the power converters. Another important feature of a UPS is the maximum power outage bridging time which depends on the capacity of the storage batteries. Depending on requirements, it may be just a few seconds or several hours. If high power and long bridging times are required, power generating sets, so-called dynamic systems, are also used. Above data must be obtained from the equipment manufacturer. Further information on UPS! Siemens AG (Ed.): TIP Application Manual - Establishment of Basic Data and Preliminary Planning, 2006, Section 5.6, and Section 5.2 in this manual.. 2/8. Totally Integrated Power by Siemens.
(18) Power System. Checklist Compilation of the intended system operating modes in the supply section Which system operating mode is intended for this plant? System operating mode 1:. .................................................................................................................................... System operating mode 2:. .................................................................................................................................... System operating mode 3:. .................................................................................................................................... Other:. .................................................................................................................................... Examples: System operating mode 1: Normal power supply 3 out of 3 transformers connected Generator down Coupling 1 closed Coupling 2 closed System operating mode 2: Transformer T1 in maintenance 2 out of 3 transformers connected (transformer 1 down) Generator down Coupling 1 closed Coupling 2 closed System operating mode 3: Emergency power supply Transformers down Generator connected into supply Coupling 1 open Coupling 2 open. Note: Alternative system operating modes from different sources of supply are important for determining minimum and maximum short-circuit currents as well as subsequent device protection settings even if merely an extension of the existing plant is considered.. 2/9. 2.
(19) 2.2 Dimensioning of Power Distribution Systems When the basic supply concept for the electricity supply system has been established, it is necessary to dimension the electrical power system. Dimensioning means the sizing/rating of all equipment and components to be used in this power system. The dimensioning target is to obtain a technically permissible combination of. switching/protective devices and connecting line for each circuit in the power system.. On principle, circuit dimensioning shall be performed in compliance with the technical rules / standards listed in Fig. 2.2/1. Details are explained below under Section 2.2.1 Circuit Types.. ically efficient overall system can be designed. This cross-circuit matching of network components may bear any degree of complexity, as subsequent modifications to certain components, e.g. a switch or protective device, may have effects on the neighboring, higher-level, or all lower-level network sections (high testing expense, high planning risk).. Cross-circuit dimensioning. Dimensioning principles. When selected network components and systems are matched, an econom-. For each circuit, the dimensioning process comprises the selection of. Basic rules. Protection against overload. IEC 60364-4-43. DIN VDE 0100 Part 430. Protection against short circuit. IEC 60364-4-43 / IEC 60364-5-54. DIN VDE 0100 Part 430 / Part 540. Protection against electric shock. IEC 60364-4-41. DIN VDE 0100 Part 410. Dynamic/static voltage drop. IEC 60364-5-520 IEC 60038. DIN VDE 0100 Part 520 DIN VDE 0175. Dynamic/static selectivity. IEC 60364-7-710 IEC 60947-2 IEC 60898-1. DIN VDE 0100 Part 710 and 718 VDE 0660-101 VDE 0641 Part 11. Fig. 2.2/1: Relevant standards for circuit dimensioning. 2/10. Totally Integrated Power by Siemens.
(20) Power System. Supply. Connecting line between distribution boards. overload (e.g. using vented transformers).. Load feeders in final circuits. Start node Transmission medium Load. Target node. Fig. 2.2/2: Schematic representation of the different circuit types. one, or more than one switching/protective device to be used at the beginning or end of a connecting line, as well as the selection of the connecting line itself (cable/line or busbar connection) under consideration of the technical features of the corresponding switching/protective devices. For supply circuits in particular, dimensioning also includes rating the power sources.. Supply circuits. The objectives of dimensioning may vary depending on the circuit type. The dimensioning target of overload and short-circuit protection can be attained in correlation to the mounting location of the protective equipment. Devices applied at the end of a connecting line can ensure overload protection for this line at best, not, however, short-circuit protection!. Load conditions in the entire power system are established by taking the energy balance (in an “energy report”). Reserve power and operational safety in the vicinity of the supply system are usually established by building up appropriate redundancies, for example by. 2.2.1 Circuit types The basic dimensioning rules and standards listed in Fig. 2.2/1 principally apply to all circuit types. In addition, there are specific requirements for these circuit types which will be explained in detail below.. Particularly high requirements apply to the dimensioning of supply circuits. This starts with the rating of the power sources. Power sources are rated according to the maximum load current to be expected for the power system, the desired amount of reserve power, and the degree of supply reliability required in case of a fault (overload / short circuit).. providing additional power sources (transformer, generator, UPS); rating the power sources according to the failure principle, n- or (n–1) principle: applying the (n–1) principle means that two out of three supply units are principally capable of continually supplying the total load for the power system without any trouble if the smallest power source fails; rating those power sources that can temporarily be operated under. Independent of the load currents established, dimensioning of any further component in a supply circuit is oriented to the ratings of the power sources, the system operating modes configured and all the related switching states in the vicinity of the supply system. As a rule, switching/protective devices must be selected in such a way that the planned performance maximum can be transferred. In addition, the different minimum/maximum shortcircuit current conditions in the vicinity of the supply system, which are dependent on the switching status, must be determined. When connecting lines are rated (cable or busbar), appropriate reduction factors must be taken into account, which depend on the number of systems laid in parallel and the installation type. When devices are rated, special attention should be paid on their rated short-circuit breaking capacity. You should also opt for a high-quality tripping unit with variable settings, as this component is an important basis for attaining the best possible selectivity towards all upstream and downstream devices. Distribution circuit Dimensioning of cable routes and devices follows the maximum load currents to be expected at this distribution level. As a rule Ib max = ∑ installed capacity x simultaneity factor Switching/protective device and connecting line are to be matched with regard to overload and shortcircuit protection.. 2/11. 2.
(21) In order to ensure overload protection, you must also observe the standardized conventional (non-)tripping currents referring to the devices in application. A verification based merely on the rated device current or the setting value Ir would be insufficient. Basic rules for ensuring overload protection: Rated current rule Non-adjustable protective equipment Ib ≤ In ≤ Iz The rated current In of the selected device must be between the calculated maximum load current Ib and the maximum permissible load current Iz of the selected transmission medium (cable or busbar). Adjustable protective equipment Ib ≤ Ir ≤ Iz The rated current Ir of overload release must be between the calculated maximum load current Ib and the maximum permissible load current Iz of the selected transmission medium (cable or busbar). Tripping current rule I2 ≤ 1.45 x Iz The maximum permissible load current Iz of the selected transmission medium (cable or busbar) must be above the conventional tripping current I2 /1.45 of the selected device. The test value I2 is standardized and varies according to type and characteristics of the protective equipment applied. Basic rules for ensuring shortcircuit protection: Short-circuit energy K 2S 2 ≥ I 2t. 2/12. (K = material coefficient; S = cross section) The amount of energy that is set free from the moment, when a short circuit occurs, until it is cleared automatically, must at any time be less than the energy which the transmission medium can carry as a maximum before irreparable damage is caused. As standard, this basic rule applies in the time range up to max. 5 s. Below 100 ms of short-circuit breaking time, the let-through energy of the protective device (acc. to equipment manufacturer’s specification) must be taken into account. When devices with a tripping unit are used, observance of this rule across the entire characteristic device curve must be verified. A mere verification in the range of the maximum short-circuit current applied (Ik max) is not always sufficient, in particular, when time-delayed releases are used.. Short-circuit time ta (Ik min) ≤ 5 s The resulting current breaking time of the selected protective equipment must ensure that the calculated minimum short-circuit current Ik min at the end of the transmission line or protected line is automatically cleared within 5 s at the latest. Overload and short-circuit protection needn’t necessarily be provided by one and the same device. If required, these two protection targets may be realized by a device combination. The use of separate switching/protective devices could also be considered, i.e. at the start and end of a cable route. As a rule, devices applied at the end. Totally Integrated Power by Siemens. of a cable route can ensure overload protection for this line only. Final circuits The method for coordinating overload and short-circuit protection is practically identical for distribution and final circuits. Besides overload and shortcircuit protection, the protection of human life is also important for all circuits.. Protection against electric shock ta (Ik1 min) ≤ ta perm If a 1-phase fault to ground (Ik1 min) occurs, the resulting current breaking time ta for the selected protective equipment must be shorter than the maximum permissible breaking time ta perm which is required for this circuit according to IEC 60364-4-41 / DIN VDE 0100-410 to ensure the protection of persons. As the required maximum current breaking time varies according to the nominal system voltage and the type of load connected (stationary and non-stationary loads), protection requirements regarding minimum breaking times ta perm may be transferred from one load circuit to other circuits. Alternatively, this protection target may also be achieved by observing a maximum touch voltage. As final circuits are often characterized by long supply lines, their dimensioning is often affected by the maximum permissible voltage drop. As far as the choice of switching/protective devices is concerned, it is important to bear in mind that long connecting lines are characterized by high impedances and thus strong attenuation of the calculated shortcircuit currents..
(22) Power System. Depending on the system operating mode (coupling open, coupling closed) and the medium of supply (transformer or generator), the protective equipment and its settings must be configured for the worst case concerning short-circuit currents.. For reasons of risk minimization and time efficiency, a number of engineering companies generally use advanced calculation software, such as SIMARIS design, to perform dimensioning and verification processes in electrical power systems.. In contrast to supply or distribution circuits, where the choice of a highquality tripping unit is considered very important, there are no special requirements on the protective equipment of final circuits regarding the degree of selectivity to be achieved. The use of a tripping unit with LI characteristics is normally sufficient.. 2.2.3 Summary Basically, the dimensioning process itself is easy to understand and can be performed using simple means. Its complexity lies in the procurement of the technical data on products and systems required, which can be found in various technical standards and regulations on the one hand and numerous product catalogs on the other. An important aspect in this context is the cross-circuit manipulation of dimensioned components owing to their technical data, for example, the above mentioned inheritance of minimum current breaking times of the non-stationary load circuit to other stationary load or distribution circuits. Another aspect is the mutual impact of dimensioning <—> network calculation (short circuit), e.g. for the use of short-circuit current limiting devices. In addition, the complexity of the matter rises, when different national standards or installation practices are to be taken into account for dimensioning.. 2/13. 2.
(23) 2.3 System Protection and Safety Coordination This chapter basically comprises the installation of electrical equipment in LV systems. Therefore, the emphasis lies on the low-voltage side also when dealing with network protection. Specific network protection requirements for medium voltage are dealt with in Section 3.6 ”Protection of Medium-Voltage Switchgear.” System configurations While in building and industrial power systems ring-system configurations are normally used for medium voltage, radial system configurations are normally preferred for the low-voltage side (radial systems, double spur systems). A number of switchgear substations and distribution boards are required for distributing power from the point of supply to the consumers. The protective devices for these items of equipment are connected in series. Objectives of system protection The objective of system protection is to detect faults and to selectively isolate faulted parts of the system. It must also permit short clearance times to limit the fault power and the effect of arcing faults. High power density, high individual power outputs, and the relatively short distances in industrial and building power systems mean that low-voltage and medium-voltage systems are closely linked. Activities in the LV system (short circuits, starting currents) also have an effect on the MV system, and vice versa, the control state of the MV system affects the. 2/14. selectivity criteria in the secondary power system. It is, therefore, necessary to adjust the power system and its protection throughout the entire distribution system and to coordinate the protective functions.. 2.3.1 Definitions Electrical installations in a power system are protected either by protection equipment allocated to the installation components or by combinations of these protective elements. Standby protection When a protective device fails, the higher-level device must take over this protective function. Back-up protection If a short circuit, which is higher than the rated switching capacity of the protective device used, occurs at a particular point in the system, back-up protection must provide protection for the downstream installation component and for the protection device by means of an upstream protective device. Rated short-circuit breaking capacity The rated short-circuit breaking capacity is the maximum value of the short circuit that the protective device is able to clear according to specifications. The protection device may be used in power systems for rated switching capacities up to this value. Selectivity Selectivity, in particular, has become a topic for discussion in the previous years. Partly, it has become a general requirement in tender specifications. Due to the complexity of this issue, information about proper selection and application is often insufficient. These requirements as well as the effects of full or partial selectivity in power distribution systems within the. Totally Integrated Power by Siemens. context of the relevant standard, industry, country, system configuration or structure should be clarified in advance with the network planners, installation companies and system operators involved. The system interconnection together with the five rules of circuit dimensioning must also be taken into account. Some terms and definitions shall be described in this chapter for a better understanding of the issue. If you wish to obtain more detailed information regarding further applications, please contact your Siemens representative. Note: Proof of selectivity is required in IEC 60364-7-710 and DIN VDE 100-710 and -718. Full selectivity To maintain the supply reliability of power distribution systems, full selectivity is increasingly demanded. A power system is considered fully selective, if only the protective device upstream of the fault location disconnects from supply, as seen in the direction of energy flow (from the point of supply to the consumer). Note: Full selectivity always refers to the maximum, fault current Ik at the mounting location. Partial selectivity The corresponding device combination (upstream and downstream) is not selective up to a dead, 3-phase, i.e. maximum, fault current Ik max. In certain situations, partial selectivity (up to a particular short-circuit current) is sufficient. The probability of faults occurring and the effects of these on the load must then be considered for unfavorable scenarios..
(24) Power System. Definite-time-delayed. t. definite-time-delayed. inversetimedelayed. t. 2. t = constant. 4. t = constant Inverse-timedelayed. Short-circuit tripping. 2. t = constant. not delayed HV HRC fuse. Medium-voltage circuit-breaker with overcurrent-time protection. LV HRC fuse. Adjustable characteristic curves or setting ranges. Adjustable characteristic curves or setting ranges. Fig. 2.3/1: Protective characteristic of LV HRC fuse and LV circuit-breaker with releases. 2.3.2 Protective Equipment Medium-voltage protection equipment HV HRC fuses High-voltage high-breaking-capacity (HV HRC) fuses can only be used for short-circuit protection. They do not provide overload protection. A minimum short-circuit current is, therefore, required for correct operation. HV HRC fuses restrict the peak shortcircuit current. The protective characteristic is determined by the selected rated current (Fig. 2.3/1). Medium-voltage circuit-breakers (IEC 62271-100/VDE 0671-100) Circuit-breakers can provide timeovercurrent protection (definite-time or inverse-time-delay), time-overcurrent protection with additional directional function, or differential protection. Distance protection is rarely used in the distribution systems described here.. Low-voltage circuit-breaker with releases. Fig. 2.3/2: Protective characteristic of HV HRC fuse and MV time-overcurrent protection. Protective characteristics Secondary relays, whose characteristic curves are also determined by the actual current transformation ratio, are normally used as protective devices in medium-voltage systems. Static digital protection devices are also being used to an increasing extent. Low-voltage protective devices* Low-voltage high-rupturingcapacity fuses Low-voltage high-rupturing-capacity (LV HRC) fuses have a high breaking capacity. They fuse quickly to restrict the short-circuit current to the utmost degree. The protective characteristic is determined by the selected utilization category of the LV HRC fuse (e. g. full-range fuse for overload and shortcircuit protection, or back-up fuse for short-circuit protection only) and the rated current (Fig. 2.3/2).. Low-voltage circuit-breakers (IEC 60947-2 / VDE 660-101) Basically, circuit-breakers for power distribution systems are distinguished according to their type design (open or compact design), mounting type (fixed mounting, plug-in, withdrawable), rated current (maximum design current of the switch), method of operation: currentlimiting (MCCB – molded-case circuit-breaker), or non-currentlimiting (ACB – air circuit-breaker) protective functions (see releases), communication capability (capability to transmit data to and from the switch), utilization category (A or B, see IEC 60947-2).. * For descriptions and modes of operation of lowvoltage protection devices, controlgear and switchgear, please also refer to the 4th edition of the Siemens AG handbook “Switching, Protection and Distribution in Low-Voltage Networks”, published by Publicis, Erlangen, 1997.. 2/15. 2.
(25) Releases / protective functions The protective function of the circuitbreaker in the power distribution system is determined by the selection of the appropriate release. Releases can be divided into thermo-magnetic releases (previously also called electromechanical releases) and electronic tripping units (ETU). Overload protection Designation: “L” or earlier “a” (“L” for long-time delay). Depending on the type of release, inverse-time-delay overload releases are also available with optional characteristic curves. Protection of neutral conductor Designation: N (neutral) Inverse-time-delay overload releases for neutral conductors are available in a 50% or 100% ratio of the overload release. Short-circuit protection, instantaneous Designation: I (instantaneous), previously also called “n” release. Example: solenoid release. Depending on the application, I-releases are also offered with a fixed, adjustable or OFF function. Short-circuit protection, with delay Designation: “S” (short-time delay), previously also “z” release. For a temporal adjustment of protective functions in series connections. Besides the standard curves and settings, there are also optional functions for special applications. – Definite-time-delay overcurrent releases: For this “standard S-function,” the desired delay time (tsd) is set to a definite value when a set current value (limit-value Isd) is exceeded (definite time; similar to the DMT function in medium voltage). 2/16. – Inverse-time-delay overcurrent release: For this optional S-function applies I2t constant. This function is generally used to ensure a higher degree of selectivity (inverse time; similar to the inverse-time-delay function in medium voltage) Ground fault protection Designation: “G” (ground fault), previously also called “g” release. Besides the standard function (definite-time), there is also an optional function (I2t inverse-time delay). Fault current protection Designation: RCD (= residual current device), previously also called “DI.” To detect differential fault currents up to 3 A, similar to the RCCB function for the protection of persons (up to 500 mA). Electronic releases also permit new tripping criteria which are not possible with electromechanical releases. Protective characteristics The protective characteristic curve is determined by the rated circuit-breaker current as well as the setting and the operating values of the releases. Low-voltage miniature circuitbreakers (MCB) IEC 608981/VDE 0641-11 Miniature circuit-breakers are distinguished according to their method of operation, showing a high current-limiting, or low current-limiting capacity. Their protective functions are determined by electromechanical releases: Overload protection by means of inverse-time-delayed overload releases, e.g. bimetallic releases. Totally Integrated Power by Siemens. Short-circuit protection by means of instantaneous overload releases, e.g. solenoid releases. 2.3.3 Low-Voltage Protective Switchgear Assemblies With series-connected distribution boards, it is possible to arrange the following protective devices in series (relative to the direction of power flow): Fuse with downstream fuse Circuit-breaker with downstream miniature circuit-breaker Circuit-breaker with downstream fuse Fuse with downstream circuitbreaker Fuse with downstream miniature circuit-breaker Several parallel feeding systems with or without coupler units with downstream circuit-breaker or downstream fuse Current selectivity must be verified in the case of meshed LV systems. The high- and low-voltage protection for the transformers feeding power to the LV system must be harmonized and matched to ensure protection of the secondary power system. Appropriate checks must be carried out to determine the effects on the primary MV system. In MV systems, HV HRC fuses are normally installed upstream of the transformers in the LV feeding system only. With the upstream circuitbreakers, only time-overcurrent protection devices with different characteristics are usually connected in series. Differential protection does not affect, or only slightly influences the grading of the other protective devices..
(26) Power System. 2.3.4 Selectivity Criteria In addition to factors such as rated current and rated switching capacity, another criterion to be considered is selectivity. Selectivity is important because it ensures optimum supply reliability. The following criteria can be applied for selective operation of series-connected protection devices: Time difference for clearance (time grading) Current difference for operating values (current grading) Combination of time and current grading (inverse-time grading) Power direction (directional protection), impedance (distance protection) and current difference (differential protection) are also used. Requirements for selective behavior of protective devices Protective devices can only act selectively if both the highest and the lowest short-circuit currents for the relevant system points are known at the project planning stage. As a result: The highest short-circuit current determines the required rated short-circuit switching capacity Icu/Ics of the circuit-breaker. Criterion: Icu or Ics > Ik max The lowest short-circuit current is important for setting the shortcircuit release; the operating value of this release must be less than the lowest short-circuit current at the end of the line to be protected, since only this setting of Isd or Ii guarantees that the overcurrent release can fulfill its operator and system protection functions. Attention When using these settings, permissible setting tolerances of ± 20%, or the. tolerance specifications given by the manufacturer must be observed!. fies narrower tolerances, this factor is reduced accordingly.. Criterion: Isd or Ii ≤ Ik min – 20% The requirement that defined tripping conditions be observed determines the maximum conductor lengths or their cross sections. Selective current grading is only possible if the short-circuit currents are known. In addition to current grading, partial selectivity can be achieved using combinations of carefully matched protective devices. In addition to current grading, partial selectivity can be achieved using combinations of carefully matched protective devices. With feeding into LV power systems, the single-phase fault current will be greater than the three-phase fault current if transformers with the Dy connection are used. The single-phase short-circuit current will be the lowest fault current if the damping zero phase-sequence impedance of the LV cable is active.. Plotting the tripping characteristics of the graded protective devices in a grading diagram will help to verify and visualize selectivity.. With large installations, it is advisable to determine all short-circuit currents using a special computer program. Here, our SIMARIS design® planning and calculation software comes as the optimum solution. Grading the operating currents with time grading Grading of the operating currents is also taken into consideration with time grading, i.e. the operating value of the overcurrent release of the upstream circuit-breaker must be at least 1.5 times the operating value of the downstream circuit-breaker. Tolerances of operating currents in definite-time-delay overcurrent Sreleases (±20%) are thus compensated. When the manufacturer speci-. 2.3.5 Preparing CurrentTime Diagrams (Grading Diagrams) When characteristic tripping curves are entered on log-log graph paper, the following must be observed: To ensure positive selectivity, the tripping curves must neither cross nor touch. With electronic inverse-time-delay (long-time delay) overcurrent releases, there is only one tripping curve, as it is not affected by preloading. The selected characteristic curve must, therefore, be suitable for the motor or transformer at operating temperature. With mechanical (thermal) inversetime-delay overload releases (L), the characteristic curves shown in the manufacturer catalog apply to cold releases. The opening times to are reduced by up to 25% at normal operating temperatures. Tolerance range of tripping curves The tripping curves of circuit-breakers given in the manufacturer catalogs are usually only average values and must be extended to include tolerance ranges (explicitly shown in Fig. 3/4, 3/20 and 3/24 only). With overcurrent releases – instantaneous (I) and definite-time delayed releases (S) – the tolerance may be ±20% of the current setting (according to IEC 60947-2 / VDE 0660 Part 101).. 2/17. 2.
(27) Significant tripping times For the sake of clarity, only the delay time (td) is plotted for circuitbreakers with definite-time-delay overcurrent releases (S), and only the opening time (to) for circuit-breakers with instantaneous overcurrent releases (I). Grading principle Delay times and operating currents are graded in the opposite direction to the flow of power, starting with the final circuit: without fuses, for the load breaker with the highest current setting of the overcurrent release, with fuses, for the fused outgoing circuit from the busbars with the highest rated fuse-link current. Circuit-breakers are preferred to fuses in cases where fuse links with high rated currents do not provide selectivity vis-à-vis the definite-time-delay overcurrent release (S) of the transformer feeder circuit-breaker, or only with very long delay times tsd (400 to 500 ms). Furthermore, circuit-breakers are used where high system availability is required, as they help to clear faults faster and the circuitbreakers’ releases are not subject to aging – especially with consumers with very long feeding distances. Procedure with two or more voltage levels In the case of selectivity involving two or more voltage levels (Fig. 2.7/2ff.), all currents and tripping curves on the high-voltage side are converted and referred to the low-voltage side on the basis of the transformer’s transformation ratio. Tools for preparing grading diagrams Standard forms with paired current values for commonly used voltages,. 2/18. Q1. 120 100 40 t 20 min 10. Q2. k1. L (cold). 4 2 1. s. k2. 20 10 4 2 1 400 200 100. ms. S t st. 40 20 10 2 101. 150 ms. t sd 180 ms t i < 30 ms. 2. 3 4 6. 102. 2. 3 4 6 103. 2. 3 4 6 10 4 2 3 4 6 105 Current (r.m.s. value). Fig. 2.3/3: Grading diagram with tripping curves of the circuit-breakers Q1 and Q2. e. g. 20/0.4 kV, 10/0.4 kV, 13.8/ 0.4 kV, etc. Templates for plotting the tripping characteristics Fig. 2.3/3 shows a hand-drawn grading diagram with tripping curves for two series-connected circuit-breakers, not taking into account tolerances. When the SIMARIS design planning software is used, a manual preparation of grading diagrams is no longer necessary. Medium-voltage time grading Tripping command and grading time The following must be observed when determining the grading time tgt on the medium-voltage side: Once the protective device has been energized (Fig. 2.3/4), the set time must elapse, before the device issues the tripping command to the shunt or. Totally Integrated Power by Siemens. undervoltage release of the circuitbreaker (command time tk). The release causes the circuit-breaker to open. The short-circuit current is interrupted when the arc has been extinguished. Only then does the protection system revert to the normal (rest) position (release time). The grading time tst between successive protective devices must be greater than the sum of the total disconnection time tg of the breaker and the release time of the protection system. Since response time tolerances, which depend on a number of factors, have to be expected for the protective devices (including circuit-breakers), a safety margin is incorporated in the grading time. Whereas grading times tst of less than 400 to 300 ms are not possible with.
(28) Power System. protective devices with mechanical releases, electronic releases have grading times of 300 ms, and digital releases used with modern vacuum circuit-breakers even provide grading times of only 250 or 200 ms. Low-voltage time grading Grading and delay times Only the grading time tst and delay time tsd are relevant for time grading between several series-connected circuit-breakers or in conjunction with LV HRC fuses. Proven grading times tst Series-connected circuit-breakers: Those so-called “proven grading times” are guiding values or rules of thumb. Precise information must be obtained from the equipment manufacturers. Grading between two circuit-breakers with electronic overcurrent releases should be about 70-80 ms Grading between two circuit-breakers with different release types (ETU and TM) should be about 100 ms For circuit-breakers with ZSI (zoneselective interlocking, i.e. shorttime grading control) the grading distance of the unblocked release has been defined as 50 ms.. Current I Shortcircuit current Operating current Load current. Time setting of overlaid protection Time setting of Grading time t st protective device Command time t k Scatter band of protective tripping. Disconnection time of circuitbreaker. Scatter band Scatter band of circuitof protective breaker tripping. t Release time. Safety time. Total disconnection time t g of circuit-breaker Fig. 2.3/4: Time grading in medium-voltage switchgear. to prevent any damage being caused by short-circuit currents. The DIN VDE and IEC standards also permit a switching device to be protected by one of the upstream protective devices with an adequate rated short-circuit switching capacity if both the branch circuit and the downstream protective device are also protected.. If the release is blocked, the switch trips within the set time tsd. Irrespective of the type of S-release (mechanical or electronic), a grading time of 70 ms to 100 ms is necessary between a circuit-breaker and a downstream LV HRC fuse. Back-up protection According to the Technical Supply Conditions of the supply network operators (see ”Electrical Installations Handbook”), miniature circuit-breakers must be fitted with back-up fuses with a rated current of 100 A (max.). Further information on low-voltage switchgear and protective devices Siemens AG (Ed.), Switching, Protection and Distribution in Low-Voltage Networks, 4th ed., published by Publicis , Erlangen, 1997 Seip, Günther (Ed.), Electrical Installations Handbook, published by Publicis, Erlangen, 2000.. 2/19. 2.
(29) 2.4 Protective Equipment for LowVoltage Power Systems Overcurrent protection devices must be used to protect lines and cables against overheating which may result from operational overloads or dead short circuits.* The protective switching devices and safety systems dealt with in this chapter are further described in Chapter 5. Tables 2.4/1 and 2.4/2 provide an overview of the protection equipment for LV systems. The protection equipment in the MV system of transformer branches has also been listed in Table 2.4/2.. * cf. Seip, Günther G. (Ed.): Electrical Installations Handbook, 4th edition, Publicis, Erlangen, 2000, Section 1.7. Miniature circuit-breakers for cable and line protection acc. to EN 60898/ IEC 60898 / DIN VDE 0641-11. 2.4.1 Circuit-Breakers with Protective Functions Protective functions of LV circuitbreakers. Zero-current interrupters / current limiters. Circuit-breakers are used, first and foremost, for overload and shortcircuit protection. In order to increase their protective functions, they can also be equipped with additional releases, e.g. for disconnection on undervoltage, or with supplementary modules for detecting fault/residual currents (also see Chapter 6).. Depending on their method of operation, circuit-breakers are available as: Zero-current interrupters Current limiters (fuse-type current limiting). Circuit-breakers are distinguished according to their protective function: Circuit-breakers for system protection acc. to IEC 60947-2 / DIN VDE 0660-101 Circuit-breakers for motor protection acc. to IEC 60947-2 / DIN VDE 0660-101 Circuit-breakers used in motor starters acc. to IEC 60947-4-2 / DIN VDE 0660-102. When configuring selective distribution boards, zero-current interrupters are more suitable as upstream protection devices and current limiters as downstream protection devices. Overload and overcurrent protection Table 2.4/3 provides an overview of releases and relays in LV circuitbreakers.. Overcurrent protection devices. Standard. Overload protection. Short-circuit protection. Line-protection fuses, gL. IEC 60269/DIN VDE 0636. ×. ×. Miniature circuit-breakers. IEC 60898/DIN VDE 0641-11. ×. ×. Circuit-breakers w. overload and overcurrent releases. IEC 60947-2/DIN VDE 0660-101. ×. ×. Switchgear fuses, aM. IEC 60269/DIN VDE 0636. –. ×. Switchgear assembly consisting of line-side fuse in utilization category gL or aM and contactor w. overload relay. IEC 60269/DIN VDE 0636. –. ×. IEC 60947-4-1/DIN VDE 0660-102. ×. –. or starter circuit-breaker and contactor w. overload relay. IEC 60947-2/DIN VDE 0660-101 IEC 60947-4-1/DIN VDE 0660-102. – ×. × –. × Protection ensured – protection not ensured Table 2.4/1: Overview of overcurrent protection devices for lines and cables together with their protection range. 2/20. Totally Integrated Power by Siemens.
(30) Power System MV protection devices applied. Switch-disconnectors, HV HRC fuses. LV. Expense. Circuit-breaker, current transformer, overcurrenttime protection. Circuit-breakers or LV HRC fuses. Tie breakers. Circuit-breaker. low. adequate. high. Medium-voltage side. Transformers with temp. detectors or thermal protection Low-voltage side with series connections of various protective devices in radial networks, and parallel connections of LV HRC fuses in interconnected grids. II >> II >>>>. HV HRC MV. MV. LV Typically single and parallel operation. LV Typically single and parallel operation. optionally ≤ 630 A. NH. ≤ 50 A, ≤ 100 A. Circuit-breaker. HV HRC fuse or LV HRC fuse > >>. Independent two-zone definite-time overcurrent-time protection, > and >>, to current transformer. Withdrawable circuit-breaker (with isolating point). Reactive-power control unit. Switch-disconnector. Contactor. Overload relay. Table 2.4/2: Overview of protection grading schemes for transformer branch and LV branch circuits. Overcurrent releases Instantaneous electromagnetic overcurrent releases have either fixed or adjustable settings, whereas the electronic overcurrent releases used in Siemens circuit-breakers all have adjustable settings. Modules The overcurrent releases can be integrated in the circuit-breaker or supplied as separate modules for. retrofitting or replacement. For possible exceptions, please refer to the manufacturers' specifications. Overload releases Mechanical (thermal) inverse-timedelay overload releases (L-releases) are not always suitable for networks with a high harmonic content. Circuitbreakers with electronic overload releases must be used in such cases.. Short-circuit protection with S-releases If circuit-breakers with definite (short) time-delay overcurrent releases (S) are used for time-graded short-circuit protection, it should be noted that the circuit-breakers are designed for a specific maximum permissible thermal and dynamic load. If the time delay causes this load limit to be exceeded in the event of a short circuit, an I-release must also be used to ensure. 2/21. 2.
(31) that the circuit-breaker is opened instantaneously in case of very high short-circuit currents. The information supplied by the manufacturer should be consulted when selecting an appropriate release. Reclosing lockout after short-circuit tripping Some circuit-breakers can be fitted with a mechanical and/or electrical reclosing lockout which prevents reclosing to the short circuit after tripping on this fault. The circuitbreaker can only be closed again after the fault has been eliminated and the lockout has been reset manually. Fault-current/residual-current protection Fault-current protection devices have acquired a position of vital importance in safety engineering all over the world, due to the high level of protection they provide (protection of human life and property) and their extended scope of protection features (alternating and pulsating current sensitivity). Apart from residual-current-operated circuit-breakers, miniature circuitbreaker assemblies, e. g. miniature circuit-breakers with fault-current tripping, are being used to an increasing extent for commercial and industrial applications. Miniature circuit-breakers (MCB) with fault-current tripping These circuit-breaker assemblies are available as compact factory-built devices or may be assembled from a miniature circuit-breaker as the basic device and an add-on module. Miniature circuit-breakers with fault-current/residual-current tripping The assembly comprising a circuitbreaker and add-on module has established itself for circuit-breakers. 2/22. Protective function. Code. Delay type of the release. Symbols acc. to EN 60617 / DIN 40713 Schematic symbol or. Overload protection. L. Stromabhängig verzögert. Selective shortS1) circuit protection (with delay). definite-timedelayed by timer Zeitglied or with I2-dependent delay. Fault-current/ G1) residual-current/ ground-fault protection (RCD). definite-timedelayed or with I2-dependent delay. Short-circuit protection (instantaneous). instantaneous. I. Graphic symbol. II>>. I. >> I>. 1). For SENTRON 3WL and SENTRON 3VL circuit-breakers also with “zone-selective interlocking” (ZSI) Combinations of releases will only be referred to by their codes as L-, S- and I-releases etc.. Table 2.4/3: Symbols for releases according to protective function. with rated currents In of up to 400 A and fault-current/residual-current tripping. Technical features The add-on module for residualcurrent tripping used in system protection applications includes such the technical features as: Rated residual current I∆n adjustable in steps, e.g. 30 mA/ 100 mA/ 300 mA/ 1,000 mA/ 3,000 mA Tripping time ta adjustable in steps, e.g. instantaneous 60 ms/ 100 ms/ 250 ms/ 500 ms/ 1,000 ms. Totally Integrated Power by Siemens. Operation depends on the system voltage Sensitivity: tripping with alternating and pulsating DC fault currents ( ) Reset button ”R” for resetting after residual-current tripping Test button ”T” for testing the circuit-breaker assembly Status display for the present leakage/residual current I∆ in the downstream circuit, e. g. by means of colored LEDs: – green:. I∆ ≤ 0,25 I∆n. – yellow: 0,25 I∆n < I∆ ≤ 0,5 I∆n.
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