Level 2 specification
NR/L2/TEL/30025
Standby Power Supply Requirements for Telecommunications Equipment
Issue 5, 02 December 2017 · Housings, earthing, power & masts
How long NR telecoms equipment must keep running when the mains fails, and how a designer decides the standby arrangement (tiers, batteries, UPS, generator)
Clause map — what each clause deals with
| 1 | Purpose | What the standard is for: keeping NR-owned telecoms equipment running for a set period after the normal supply is lost, with a whole-life-cost view rather than 'biggest battery wins' |
| 2 | Scope | Applies to design and installation of new and renewed standby power systems, to assessing existing ones, and to their maintenance |
| 3 | Definitions | Terms used: battery bank, battery string, monobloc, concurrently maintainable, AIP, DNO and so on |
| 4 | Background | Why NR is moving away from long battery autonomies as the default — cost, manual handling and the availability of alternatives |
| 5.1 | Initial assessment | Options the designer has to show they considered before sizing batteries: improving the incoming power infrastructure, generators, alternative supplies |
| 5.2 | Process | The three-stage assessment — criticality of the telecoms system (Stage 1, with NR/L1/TEL/30102 as a guide), availability of the proposed power infrastructure (Stage 2, Tier 1–4 table), then whether a UPS is needed (Stage 3) |
| 6 | Approval | Standby arrangements are approved by the National Telecoms Asset & Performance Manager through the Approval in Principle (AIP) |
| 7 | Rectifier/Charger requirements | What the rectifier/charger must do: display load current, voltage and temperature, be isolatable and labelled, support the battery correctly |
| 8 | Battery Bank requirements | Designing the battery bank — smaller, lighter monoblocs to cut manual-handling risk, siting away from the equipment where possible, manufacturer's installation instructions |
| 9 | Records | Designed standby times are recorded in Ellipse by the Project Engineer once commissioned |
| 10 | Maintenance of Standby Power Supplies | Maintenance is to NR/L3/TEL/30081 |
| Appendix A | Criticality Requirements | The Tier 1–4 criticality table and flow chart — how many mains sources, redundancy and generator provision each tier implies |
| Appendix B | Suggested Tier levels and standby times for Telecoms Systems | The look-up table of minimum and typical standby durations by asset type — e.g. FTN core/access/FTNx node 4 h minimum (12 h typical), transmission/IP with generator 30 min, PETS and tunnel emergency comms 4 h, voice recorders 4 h |