Guidance note
NR/GN/TEL/31109
Telecoms Back Up Power Selection Guidance
Issue 1, 26 August 2008 · Housings, earthing, power & masts
A plain explanation of the telecoms power plant types (UPS, -48 V DC plant, inverters) up to 10 kVA, how to specify one from approved modules, and worked sizing examples for batteries and rectifiers
Clause map — what each clause deals with
| 1 | Purpose | What the guide is for: explaining the different telecoms power plant systems at a generic level and helping compile a system from approved modules |
| 2 | Scope | 230 V AC, -48 V DC and -24 V DC telecoms power systems up to 10 kVA; larger systems belong to E&P |
| 3 | Recommended Process for Defining a New Power System | The step-by-step way to specify a power system: user determines load, autonomy and environment; then rectifier/UPS and battery selection |
| 4 | Definitions | Definitions of AC/DC converter, static switch, inverter, bypass and the other building blocks |
| 5 | Introduction | The three conversion types telecoms use — AC-AC (UPS), AC-DC (DC plant), DC-AC (inverter) — and how each gives battery back-up |
| 6 | AC to AC: UPS | UPS types per BS EN 62010-3 (VFI/on-line, VI, VFD) and the parts of a typical VFI UPS |
| 7 | AC-DC: DC Power Plant | How a -48 V DC power plant is built up — rectifier modules, controller, battery, distribution |
| 8 | DC to AC: Inverter | Inverter operating modes — continuous and back-up — and their effect on supply interruption |
| 9 | Approved Equipment | Equipment with product approval at the time (Riello and Powerware UPS; Eltek Flatpack and Harmer & Simmons DC plant), with a Flatpack selection table and example — check current approval status before use |
| Appendix A | Battery Terminology | Battery, string, bloc and cell explained |
| Appendix B | Designing an AC to AC UPS | Worked example of sizing a UPS rectifier and battery |
| Appendix C | Calculation for a DC Power Plant | Worked example of sizing a DC power plant |
| Appendix D | Rectifier Sizing For a DC Power Plant - A Rough Calculation | Rule-of-thumb rectifier sizing: load power plus recharge power |
| Appendix E | Technical Requirements for Assessing Power Systems | The EMC, safety and environmental standards used in product acceptance of power systems |