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EUROPEAN STANDARD
Environmental Engineering (EE);
Power supply interface at the input of
Information and Communication Technology (ICT) equipment;
Part 2: -48 V Direct Current (DC)
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2 ETSI EN 300 132-2 V2.6.1 (2019-04)
Reference
REN/EE-0270
Keywords
interface, power supply
ETSI
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3 ETSI EN 300 132-2 V2.6.1 (2019-04)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Requirements . 9
4.0 Power interface "A" . 9
4.1 Nominal voltage . 10
4.2 Normal service voltage range at interface "A" . 10
4.3 Abnormal service voltage range at interface "A" . 11
4.3.1 Abnormal service voltage range under steady state conditions . 11
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions . 11
4.3.3 Voltage transients . 12
4.3.3.1 Voltage transient due to short-circuit and protective device clearance . 12
4.3.3.2 Short voltage transient due to switching and lightning . 12
4.3.4 Recovery from voltage transients . 13
4.4 Voltage changes due to the regulation of the power supply . 14
4.5 Power supply protection at interface "A" . 14
4.6 Maximum current drain . 14
4.7 Inrush Current on connection of interface "A" . 15
4.7.1 Limits . 15
4.7.2 Measurements . 16
4.8 Conducted immunity requirements of the ICT equipment at interface "A": narrowband noise . 17
4.9 Conducted emissions requirements of the ICT equipment at interface "A" . 19
5 Earthing and bonding . 20
Annex A (informative): Identification of interface "A" . 21
Annex B (informative): -60 VDC systems . 22
Annex C (informative): Guide for measuring inrush current and for transferring the
recorded pulses onto the limit chart . 23
C.1 Measurement . 23
C.2 Pulse waveform transfor mation . 23
C.3 Measurement of inrush current with filter capacitor current pulses . 26
Annex D (informative): Test arrangements for the injection of electrical noise at interface
"A" . 29
Annex E (informative): Wideband noise . 30
E.0 Wideband noise . 30
E.1 Emission of wideband noise . 30
E.1.0 General . 30
E.1.1 Assessment of wideband noise . 30
ETSI
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4 ETSI EN 300 132-2 V2.6.1 (2019-04)
E.2 How to calculate wideband emission . 30
Annex F (informative): Protection dimensioning . 34
Annex G (informative): Effects of protective device operation transients in the power
distribution . 35
Annex H (informative): Bibliography . 36
History . 37
ETSI
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5 ETSI EN 300 132-2 V2.6.1 (2019-04)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE).
The present document concerns the requirements for the interface between ICT equipment and its power supply, and
includes requirements relating to its stability and measurement. Various other references and detailed measurement and
test arrangements are contained in informative annexes.
The present document is part 2 of a multi-part deliverable covering Environmental Engineering (EE); Power supply
interface at the input to Information and Communication Technology (ICT) equipment, as identified below:
Part 1: "Alternating Current (AC)";
Part 2: "-48 V Direct Current (DC)";
Part 3: "Up to 400 V Direct Current (DC)".
National transposition dates
Date of adoption of this EN: 9 April 2019
Date of latest announcement of this EN (doa): 31 July 2019
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 January 2020
Date of withdrawal of any conflicting National Standard (dow): 31 January 2020
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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6 ETSI EN 300 132-2 V2.6.1 (2019-04)
1 Scope
The present document contains requirements and measurements methods for the physical interface "A" that is situated
between the power supply system(s) and the power consuming ICT equipment.
The nominal voltage at power interface "A" of ICT equipment defined in the present document is DC voltage -48 V.
The DC power can be supplied by a DC output power system (e.g. based on AC rectifiers on grid or DC/DC converters on
solar system, fuel cell, DC engine or fuel cell generator) and also directly supplied by a battery backup in this DC power
system. The purpose of the present document is to use a power supply system with the same characteristics for all ICT
equipment defined in the area of application:
- to facilitate inter working of different types of load units;
- to facilitate the standardization of ICT equipment;
- to facilitate the installation, operation and maintenance in the same network of ICT equipment and systems
from different origins.
The present document aims at providing electrical compatibility between the power supply equipment and the power
consuming ICT equipment, between different system blocks and loads connected to the same power supply feeding the
interface "A" (e.g. control/monitoring, cooling system, etc.).
The requirements are defined for:
- the power supply input of any type of ICT equipment installed at telecommunication centres that are connected
to interface "A" powered by DC;
- any type of ICT equipment, installed in access networks and customers' premises, the DC interface "A" of
which is also used by equipment requiring a DC supply source;
- any type of ICT equipment powered by DC, used in the fixed and mobile networks installed in different
locations such as buildings, shelters, street cabinets.
Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered
within the present document.
The present document does not cover safety requirements, they are covered by relevant safety standards.
The present document does not cover EMC requirements, they are covered by relevant EMC standards.
NOTE: Annex B gives guidance on -60 VDC supply systems.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Void.
[2] Void.
ETSI
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7 ETSI EN 300 132-2 V2.6.1 (2019-04)
[3] Void.
[4] Void.
[5] CENELEC EN 61000-4-5: "Electromagnetic compatibility (EMC) - Part 4-5: Testing and
measurement techniques - Surge immunity test".
[6] Void.
[7] CENELEC EN 61000-4-29: "Electromagnetic compatibility (EMC) - Part 4-29: Testing and
measurement techniques -Voltage dips, short interruptions and voltage variations on d.c. input
power port immunity tests".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T Q.551: "Transmission characteristics of digital exchanges".
[i.2] Recommendation ITU-T Q.552: "Transmission characteristics at 2-wire analogue interfaces of
digital exchanges".
[i.3] Recommendation ITU-T Q.553: "Transmission characteristics at 4-wire analogue interfaces of
digital exchanges".
[i.4] Recommendation ITU-T Q.554: "Transmission characteristics at digital interfaces of digital
exchanges".
[i.5] ETSI TR 100 283: "Environmental Engineering (EE); Transient voltages at Interface "A" on
telecommunications direct current (dc) power distributions".
[i.6] US Department of Defence MIL-STD-461E: "Requirements for the control of electromagnetic
interference characteristics of subsystems and equipment".
[i.7] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of ICT equipment
powered by -48 VDC in telecom and data centres".
[i.8] Recommendation ITU-T O.41: "Psophometer for use on telephone-type circuits".
[i.9] IEC 60050-601: "International Electrotechnical Vocabulary. Chapter 601: Generation,
transmission and distribution of electricity - General" (Area 826 "Electrical installations",
section 826-11 "Voltages and currents").
[i.10] CENELEC EN 60269-1: "Low-voltage fuses - Part 1: General requirements".
[i.11] CENELEC EN 60934: "Circuit-breakers for equipment (CBE)".
ETSI
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8 ETSI EN 300 132-2 V2.6.1 (2019-04)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady-state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
customer premises: location which is the sole responsibility of the customer
DC power return conductor: 0 V power supply conductor
NOTE: Also called "battery return".
fully equipped equipment: configuration that corresponds to the maximum power consumption measured at -48 VDC
with the equipment in operating conditions (e.g. not in standby mode)
NOTE: When there are several fully equipped configurations because of different combinations of possible
boards, the configuration with the boards that gives the highest power consumption should be considered.
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
interface "A": terminals at which the power supply is connected to the system block
NOTE 1: See also figure 1 and annex A.
NOTE 2: This is a functional definition and not an exact depiction of the physical location.
malfunction: termination of the normal service
maximum steady state input current (I ): maximum steady state input current, stated by the manufacturer, for a fully
m
equipped equipment under test connected to interface "A" at nominal voltage
nominal voltage: value of the voltage by which the electrical installation or part of the electrical installation is
designated and identified [i.9]
normal service: service mode where ICT equipment operates within its specification which includes a defined restart
time after malfunction or full interruption
normal service voltage range: range of steady-state voltages over which the equipment will maintain normal service
power supply: power source to which ICT equipment is intended to be connected
service voltage: value of the voltage under normal conditions, at a given instant and a given point of the system [i.9]
system block: functional group of equipment depending for its operation and performance on its connection to the same
power supply
NOTE: A system block may consist of equipment or a functional group of equipment. Different examples of
configurations at interface "A" are given in annex A.
telecommunication centre: location where ICT equipment is installed and which is the sole responsibility of the
operator
ETSI
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9 ETSI EN 300 132-2 V2.6.1 (2019-04)
3.2 Symbols
For the purposes of the present document, the following symbols apply:
I instantaneous inrush current
t
I maximum steady state input current
m
L inductance of inductive element of LISN
R resistance of resistive element of LISN
t time
U
pso,eff effective psophometric voltage
U
rms RMS voltage
Z capacitive impedance of immunity measurement circuit
c
Z resistive impedance of immunity measurement circuit
m
μs microsecond
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
DC Direct Current
NOTE: Also when used as a suffix to units of measurement.
EMC ElectroMagnetic Compatibility
ESR Equivalent Series Resistance
EUT Equipment Under Test
HOD High-Ohmic Distributions
ICT Information and Communication Technology
LISN Line Impedance Stabilization Network
LOD Low-Ohmic Distributions
RF Radio Frequency
rms root mean square
TR Technical Report
VDC Voltage Direct Current
NOTE: Also when used as a suffix to units of measurement.
4 Requirements
4.0 Power interface "A"
The power supply interface, interface "A" of figure 1, is a physical point to which all the requirements are related.
This point is situated between the power supply system(s) and the power consuming ICT equipment.
An example of a configuration in which interface "A" is identified is given in annex A.
ETSI
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10 ETSI EN 300 132-2 V2.6.1 (2019-04)
ICT equipment
Figure 1: Identification of interface "A"
4.1 Nominal voltage
The interface and equipment shall be designated and identified by a nominal voltage.
The nominal voltage at interface "A" shall be -48 VDC with positive conductor connected to earth as defined in ETSI
EN 300 253 [i.7].
NOTE 1: The positive conductor, also called DC return, can be (see ETSI EN 300 253 [i.7]:
Isolated DC return: this is a DC power system in which the DC power return conductor has a single
point connection to the bonding network. Equipment intended for this power distribution has a
floating DC power at the power input terminal.
Common DC return: this is a DC power system in which the return conductor is connected to the
bonding network at many points. Equipment intended for this power distribution can have the DC
return earthed at the power input terminal.
NOTE 2: In most cases the nominal voltage of interface "A" is based on a 24 cells lead-acid battery. Use of other
technologies, such as Lithium-ion batteries, are increasing.
4.2 Normal service voltage range at interface "A"
The normal service voltage range for the -48 VDC nominal supply at interface "A" shall be from -40,5 VDC
to -57,0 VDC.
There shall be no degradation of service performance when ICT equipment is operating at voltages within the normal
service voltage range including voltage variation inside the normal voltage range.
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 1. The testing and measurement techniques are described in CENELEC EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply "A" interface inputs.
ETSI
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11 ETSI EN 300 132-2 V2.6.1 (2019-04)
Table 1
Test level of Normal Voltage Basic standard Rise and fall time of Performance criteria
service voltage step step for testing voltage step
variation Duration
From -40,5 V to -57,0 VDC 0,1 s CENELEC No degradation in the
Between 1 μs and 50 μs on
From -57,0 V to -40,5 VDC 0,1 s EN 61000-4-29 [7] 100 Ω resistive load service performance
during and after the
(see basic standard for test
test
generator)
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 1 on the
powered input.
NOTE 1: The minimum voltage is based on the voltage drop in the distribution network and a battery cell end of
discharge voltage.
NOTE 2: The voltages specified are measured at interface "A". It should be noted that if interface "A" is at any
point other than the ICT equipment interface as presented in annex A, there will be a voltage drop
between interface "A" and the equipment terminals.
4.3 Abnormal service voltage range at interface "A"
4.3.1 Abnormal service voltage range under steady state conditions
ICT equipment designed to work at 48 VDC nominal voltage at the interface "A" shall not suffer any damage when
subjected to the following voltage ranges defined in table 2.
Table 2
0,0 V to -40,5 VDC and
-57,0 VDC to -60,0 VDC
Following the restoration of the supply to the normal voltage range, the power conversion and management systems on
the load side of interface "A" shall automatically restore normal service. The ICT equipment shall then resume
operation according to its specifications. The abnormal service voltage shall not lead to the disconnection of the power
supply e.g. by causing circuit breakers, fuses or other such devices to operate.
NOTE: It is acceptable that the system may restart when the voltage is -40,5 VDC or anywhere within the
nominal service voltage range and/or after a time delay.
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions
ICT equipment shall comply with the requirements defined in this clause when subject to the abnormal voltage range
defined in table 3 that can be present at the interface "A".
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 3. The testing and measurement techniques are described in CENELEC EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply inputs.
ETSI
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12 ETSI EN 300 132-2 V2.6.1 (2019-04)
Table 3
Test level of abnormal Voltage step Basic standard Rise and fall time of Performance criteria
voltage step variation Duration for testing voltage step
From -40,5 VDC to -60,0 VDC 0,1 s CENELEC Self restart to a normal
Between 1 μs and 50 μs
and from -60 VDC to -40,5 VDC EN 61000-4-29 [7] service of the equipment
on 100 Ω resistive load
From -57,0 VDC to 0,0 V and 0,1 s (see basic standard) without operator
intervention after the test
from 0,0 V to -57,0 VDC
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on one input (either Input 1 or 2).
In this case the performance criteria shall be "No degradation in the service performance during and after the
test";
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 3 on the
powered input.
4.3.3 Voltage transients
4.3.3.1 Voltage transient due to short-circuit and protective device clearance
Voltage transients may occur at interface "A" when faults (e.g. short circuits) occur in the power distribution system.
These transients are characterized by a voltage drop in the range: 0 V to -40,5 VDC, followed by an overvoltage often
in excess of the maximum steady state abnormal service voltage range defined in table 3 and dependent upon the power
distribution up to interface "A" and the equipment connected to interface "A".
NOTE 1: ETSI TR 100 283 [i.5] provides guidance for the protection of ICT equipment from the transients.
NOTE 2: A protective device operation transient results from a low impedance fault to ground on the equipment
side of a protective device (fuse or circuit breaker) connected to a power distribution bus. In the power
bus, then voltage is reduced (undervoltage) due to high current flowing to ground through the protective
device and the short ground. When the protective device opens, the release energy stored in the
inductance of the bus causes an initial high voltage overshoot of short duration, followed by a longer
interval voltage overshoot that decays toward the steady state bus voltage. The undervoltage portion of
the protective device operation transient, may cause a voltage drop at the input terminals of the other
equip
...