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TECHNICAL SPECIFICATION
Environmental Engineering (EE);
Impact on ICT equipment architecture of multiple AC,
-48 VDC or up to 400 VDC power inputs
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2 ETSI TS 103 531 V1.1.1 (2018-09)
Reference
DTS/EE-0267
Keywords
architecture, electric, interface, power supply
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3 ETSI TS 103 531 V1.1.1 (2018-09)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions, symbols and abbreviations . 6
3.1 Definitions . 6
3.2 Symbols . 6
3.3 Abbreviations . 6
4 Definition and requirement of the multiple power interface configuration at the input power feeds
of ICT equipment . 7
4.1 Individual power interface used for multiple power interface configuration . 7
4.2 Multiple power interface configurations and requirements . 7
4.2.1 Identification of multiple interface inputs options . 7
4.2.2 Configuration AC/AC . 8
4.2.3 Configuration AC/400 VDC . 8
4.2.4 Configuration 400 VDC/400 VDC . 9
4.2.5 Configuration AC/-48 VDC . 9
4.2.6 Configuration -48 VDC/-48 VDC . 10
4.2.7 Configuration 400 VDC/-48 VDC . 10
5 Combination dependence of A, A3 and A3ac interface for multiple power feeds . 11
6 Back feeding protection. 14
Annex A (informative): Switch Selector installation options . 16
Annex B (informative): Switch Selector - General functionality and requirements Switch . 19
Annex C (informative): Back-feeding Protection . 20
Annex D (informative): Example of upstream conversion for dual -48 VDC power feed
configuration at input of ICT equipment . 22
History . 23
ETSI
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4 ETSI TS 103 531 V1.1.1 (2018-09)
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 Technical Specification (TS) has been produced by ETSI Technical Committee Environmental Engineering (EE).
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.
Introduction
With the advantages of the emerging up to 400 VDC power distribution along with the continued use of the legacy AC
and -48 VVD power distribution for telecom and Information and Communication Technology (ICT) power feeding, a
new ICT power interface is defined as being a combination of the standardized AC and DC power interfaces
(AC, -48 V, up to 400 VDC). In general case, the power configuration combination will be made of up to two of these
three power interfaces and is identified as dual power inputs interface of an ICT system.
The present document also provides details showing the ICT equipment front end power architectures that includes the
on board converter and the interconnection options between the converter and the ICT interface. These include interface
switch selector and diode combiner solutions for multiple power input feeds.
With the increase in the variation of potential power feeds to ICT equipment especially with the emergence of up to
400 VDC power networks, a clear indication of how a multiple input power feed is to be referenced and how these
multiple power feeds can be best managed, is crucial in ensuring that common and recognized approaches are adopted
in the installation and configuration of future ICT equipment.
Annex B presents options for the installation of a switch selector within ICT equipment and its operational attributes
targeted for its reliable operation.
The present document was developed jointly by ETSI TC EE and ITU-T Study Group 5 and published respectively by
ETSI and ITU-T as ETSI Standard ETSI TS 103 531 and as Recommendation ITU-T L.1206, which are technically
equivalent.
ETSI
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5 ETSI TS 103 531 V1.1.1 (2018-09)
1 Scope
The present document is applicable to the case of multiple power feeding configurations at the input of ICT equipment
in ICT system.
The present document describes the combination of three power interfaces as A (-48 V), P or A3 (up to 400 VDC) and
A3ac (AC) that could potentially be used for each input.
The present document also provides details of the power structure within the ICT equipment, between the ICT
equipment interfaces and ICT equipment system loads that is inclusive of system power converters.
The input power configurations are categorized to allow for better understanding and identification of the each new
multiple power feeding interface, providing details of the impacts and benefits of adopting them. Information is also
provided on the impact on battery test function when used with the different dual power inputs combinations.
Lastly requirements are given for avoiding the potential risk of voltage back feeding from one input to the other and for
general isolation requirements in all multiple power feeding configurations.
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] Recommendation ITU-T L.1200: "Direct current power feeding interface up to 400 V at the input
to telecommunication and ICT equipment".
[2] ETSI EN 300 132-2: "Environmental Engineering (EE); Power supply interface at the input to
telecommunications and datacom (ICT) equipment; Part 2: Operated by -48 V direct current (dc)".
[3] ETSI EN 300 132-3-1: "Environmental Engineering (EE); Power supply interface at the input to
telecommunications and datacom (ICT) equipment; Part 3: Operated by rectified current source,
alternating current source or direct current source up to 400 V; Sub-part 1: Direct current source
up to 400 V".
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] ETSI EN 300 132-1: "Environmental Engineering (EE); Power supply interface at the input to
Information and Communication Technology (ICT) equipment; Part 1: Operated by Alternating
Current (AC) source".
ETSI
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6 ETSI TS 103 531 V1.1.1 (2018-09)
[i.2] IEC 60445: "Basic and safety principles for man-machine interface, marking and identification -
Identification of equipment terminals, conductor terminations and conductors".
[i.3] ISO/IEC 2382-14: "Information technology - Vocabulary - Part 14: Reliability, maintainability and
availability".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
combined power feeding: function by which two power inputs feeds to ICT equipment is managed such that one input
is always available to power a single power module within the ICT equipment e.g. by using the reverse bias
characteristic of a two diodes common cathode module or a dual MOSFET
combiner: device achieving the combined power feeding function
dependant power feed: power feed associated with a single interface on the ICT equipment but jointly associated to
another power feed with a single power module within the ICT equipment via a managed power interface (switched or
combined power feed)
hot standby state: standby state providing for immediate operation upon demand
NOTE 1: This is the hot standby mode of an equipment or a system as defined in ISO/IEC 2382-14 [i.3].
NOTE 2: A hot standby state may apply to redundant or stand-alone items.
NOTE 3: In some applications, an item in a hot standby state is considered to be operating.
independent power feed: power feed associated with a single interface on the ICT equipment and a single power
module within the same ICT equipment used in a multiple power feeding interface
interface "A": ICT equipment -48 VDC power interface as defined in ETSI EN 300 132-2 [2]
interface "A3": ICT equipment up to 400 VDC power interface as defined in ETSI EN 300 132-3-1 [3]
interface "A3ac": ICT equipment AC power interface as defined in ETSI EN 300 132-1 [i.1]
interface "P": ICT equipment up to 400 VDC power interface as defined in Recommendation ITU-T L.1200 [1]
switched power feeding: method by which two power inputs feeds to ICT equipment is managed such that one input is
always available to power a single power module within the ICT equipment with the use of a switch
switch selector: device achieving the switched dependant power feed selection by a power switch
3.2 Symbols
For the purposes of the present document, the following symbols apply:
A+ Pole plus of input A
A- Pole minus of input A
B+ Pole plus of input B
B- Pole minus of input B
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
ETSI
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7 ETSI TS 103 531 V1.1.1 (2018-09)
CONV CONVerter
D Diode
DC Direct Current
EMC ElectroMagnetic Compatibility
ICT Information and Communication Technology
MOSFET Metal Oxide Semiconductor Field Effect Transistor
swSelect switch Selector
TC Technical Committee
VAC Volt AC
VDC Volt DC
4 Definition and requirement of the multiple power
interface configuration at the input power feeds of
ICT equipment
4.1 Individual power interface used for multiple power interface
configuration
The power supply interfaces presented in Figures 1 to 6, are the physical inter-connection points to which all the
requirements are related. These points are situated between the power supply system(s) and ICT equipment.
Definitions of configurations in which "A","P(A3)" and "A3ac" interfaces presented as individual interface references
can be found in the following documents:
• ETSI EN 300 132-1 [i.1], annex C (AC supply) - A3ac interface
• ETSI EN 300 132-2 [2], annex E (-48 VDC supply) - A interface
• Recommendation ITU-T L.1200 [1], P interface (up to 400 VDC supply) - equivalent to ETSI
EN 300 132-3-1 [3], annex B - A3 interface
NOTE: Subject to the installation preconditions, this point may be located at any other point between the power
supply system and ICT equipment by mutual agreement of the relevant parties.
4.2 Multiple power interface configurations and requirements
4.2.1 Identification of multiple interface inputs options
For the case of multiple inputs configurations occurring on ICT equipment, (e.g. power supply unit with dual feeds)
each power interface shall comply with at least one of the applicable interface detailed in clause 6.
The multiple power interfaces shall be identified by using each of the individual interface definitions in sequence, for
example, an ICT interface comprising of one AC supply (A3ac) and one AC supply (A3ac) shall be named A3ac/A3ac.
In respect of the contents presented within the present document, interface "A3ac/A3ac", "A3ac/A3",
"A3/A3","A3ac/A", "A/A", and "A/A3" are located at the power terminals of the ICT equipment or system as defined
by the manufacturer in accordance with IEC 60445 [i.2].
Table 1 presents all the interface options for multiple power feeds to ICT equipment. This table makes the initial
assumption that a maximum of only two power feeds are used at the interface. Power interfaces will be configured for
any ICT equipment installation and the individual interface shall be in accordance with the input power feed selected.
ETSI
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8 ETSI TS 103 531 V1.1.1 (2018-09)
Table 1: Interface configuration options for multiple power feed of ICT equipment
AC 400 VDC 48 VDC
A3ac/A3ac A3ac/A3 A3ac/A
AC
(Figure 1) (Figure 2) (Figure 4)
A3ac/A3 A3/A3 A3/A
400 VDC
(Figure 2) (Figure 3) (Figure 6)
A3ac/A A3/A A/A
-48 VDC
(Figure 4) (Figure 6) (Figure 5)
4.2.2 Configuration AC/AC
Figure 1 presents the interface A3ac/A3ac for a multiple power feed consisting of two AC power feeds.
Figure 1: General identification of the A3ac/A3ac interface
for multiple power feeds for dual AC inputs
The interface and the operational voltage characteristics for an AC power feed are detailed within document [i.1].
4.2.3 Configuration AC/400 VDC
Figure 2 presents the interface "A3ac/A3" for a multiple power feed consisting of one AC power feed and one up to
400 VDC power feed. The AC interface and the interface for up to 400 VDC power feeds have the interface references
of "A3ac" and "A3" respectively and as such the combination of these two reference interfaces when used together on
ICT equipment is presented as "A3ac/A3".
ETSI
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9 ETSI TS 103 531 V1.1.1 (2018-09)
Figure 2: General identification of the A3ac/A3 interface
for multiple power feeds for AC and up to 400 VDC inputs
The interface and the operational voltage characteristics for an AC power feed are detailed within ETSI
EN 300 132-1 [i.1] and the interface and the operational voltage characteristics for up to 400 VDC power feed shall be
as detailed within ETSI EN 300 132-3-1 [3].
4.2.4 Configuration 400 VDC/400 VDC
Figure 3 presents the interface "A3" for a multiple power feed consisting of two up to 400 VDC power feeds.
Figure 3: General identification of the A3 interface
for multiple power feeds for dual of up to 400 VDC inputs
The interface and the operational voltage characteristics for up to 400 VDC power feed shall be as detailed within ETSI
EN 300 132-3-1 [3].
4.2.5 Configuration AC/-48 VDC
Figure 4 presents the interface "A3ac/A" for a multiple power feed consisting of one AC power feed and one -48 VDC
power feed. In this instance the AC and -48 VDC interfaces have interfaces structures which are termed as "A3ac and
A" respectively.
ETSI
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10 ETSI TS 103 531 V1.1.1 (2018-09)
Figure 4: General identification of the A interface
for multiple power feeds for AC and -48 VDC inputs
The interface and the operational voltage characteristics for an AC power feed are detailed within document [i.1] and
the interface and the operational voltage characteristics for the -48 VDC power feed shall be as detailed within ETSI
EN 300 132-2 [2].
4.2.6 Configuration -48 VDC/-48 VDC
Figure 5 presents the interface "A" for a multiple power feed consisting of two -48 VDC power feeds.
NOTE: It is possible that some energy conversion parts be upstream from the interface A, please refer to annex D
for detailed information.
Figure 5: General identification of the A interface
for multiple power feeds for dual -48 VDC inputs
The interface and the operational voltage characteristics for a -48 VDC power feed shall be as detailed within ETSI
EN 300 132-2 [2].
4.2.7 Configuration 400 VDC/-48 VDC
Figure 6 presents the interface "A/A3" for a multiple power feed consisting of one up to 400 VDC power feed and
one -48 VDC power feed. The -48 VDC interface and the interface for up to 400 VDC power feeds have the interface
references of A and A3 respectively and as such the combination of these two reference interfaces when used together
on ICT equipment is presented as "A/A3".
ETSI
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11 ETSI TS 103 531 V1.1.1 (2018-09)
Figure 6: General identification of the A/A3 interface
for multiple power feed for up to 400 VDC and -48 VDC inputs
The interface and the operational voltage characteristics for a -48 VDC power feed shall be as detailed within ETSI
EN 300 132-2 [2] and the interface and the operational voltage characteristics for up to 400 VDC power feed shall be as
detailed within ETSI EN 300 132-3-1 [3].
5 Combination dependence of A, A3 and A3ac
interface for multiple power feeds
Table 2 presents the alternative power architecture structures between the interfaces detailed in clause 6 and the load
interface of the ICT equipment. The power structures presented include the ICT equipment's on board power converters
and any power management solutions that allow for the controlled supervision of the input powers presented at the ICT
equipment interface to ensure continued operation of the ICT equipment in the advent of any one preferred input power
feed failing.
Table 2 shows that when there is a dependent power feed, a managed redundancy function is required for its proper
operation. This can be clearly seen with the switched and combined input configurations presented (architectures 7 to
11).
ETSI
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12 ETSI TS 103 531 V1.1.1 (2018-09)
Table 2: Alternate power structures within ICT equipment between ICT power input interface and ICT
equipment load inclusive of power converter
System Supply Interface Battery test Power structure Architecture
Config Configuration
(note 2)
1 AC/AC A3ac/A3ac Ok Two separate AC power
Direct power feed (Figure 1) feed to the ICT equipment
Independent here detailed as A1 and
power feeds B1. Direct power feed
(1) connection from the ICT
interface to a converter.
Each converter and
interface used in the ICT
equipment is effectively
doubled A1/An and B1/Bn.
2 AC/400 VDC A3ac/A3 Ok One AC and one up to
Direct power feed (Figure 2) 400 VDC power feed to
Independent the ICT equipment.
power feeds (as for System
(1) Configuration 1).
3 400 VDC/400 VDC A3/A3 Ok Two separate up to 400
Direct power feed (Figure 3) VDC power feeds to the
Independent ICT equipment.
power feeds (as for System
(1) Configuration 1).
4 AC/-48 VDC A3ac/A Ok One AC and one -48 VDC
Direct power feed (Figure 4) power feed to the ICT
Independent equipment
power feeds (as for System
(1) Configuration 1).
ETSI
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13 ETSI TS 103 531 V1.1.1 (2018-09)
System Supply Interface Battery test Power structure Architecture
Config Configuration
(note 2)
5 400 VDC/-48 VDC A3/A Ok One up to 400 VDC and
Direct power feed (Figure 6) one -48 VDC power feed
Independent to the ICT equipment
power feeds (as for System
(1) Configuration 1).
6 -48 VDC/-48 VDC A/A Ok Two separate -48 VDC
Direct power feed (Figure 5) power feed to the ICT
Independent equipment.
power feeds (as for System
(1) Configuration 1).
7 AC/AC switch A3ac/A3ac Ok Two separate AC power
selection (Figure 1) feeds to the ICT
Dependant equipment here detailed
power feeds as A and B . An input
1 1
(2), (3) selection by a selector
switch is placed between
the ICT equipment power
interface and one internal
converter. Power feed
from either ICT
equipment interface is
selected to power the
converter.
8 AC/400 VDC switch A3ac/A3 Ok One AC and one up to
selection (Figure 2) 400 VDC power feeds to
Dependant the ICT equipment.
power feeds (as for System
(2), (3) configuration 7).
9 400 VDC/400 VDC A3/A3 Ok Two separate up to 400
switch selection (Figure 3) VDC power feeds to the
Dependant ICT equipment.
power feeds (as for System
(2), (3) configuration 7).
ETSI
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14 ETSI TS 103 531 V1.1.1 (2018-09)
System Supply Interface Battery test Power structure Architecture
Config Configuration
(note 2)
10 -48 VDC/-48 VDC A/A No (note 1) Two separate 48 VDC
diode combiner (Figure 5) power feeds to the ICT
Dependant equipment here detailed
power feeds as A1 and B1. A diode
(2), (4) combiner is placed
between the ICT
equipment interface and
one converter. The input
power feed connected to
the diode with the higher
DC voltage potential is
automatically selected as
the main powering supply
of the ICT equipment by
reverse biasing the diode
connected to the lower
DC voltage potential.
11 400 VDC/to 400 A3/A3 No (note 1) Two separate up to
VDC diode (Figure 3) 400 VDC power feeds to
combiner the ICT equipment.
Dependant (as per System Config
power feeds 10).
(2), (4)
NOTE 1: The diode combiner configuration cannot be used in a single battery test scenario as this configuration offers no
isolation of the battery line under test. In order to achieve battery testing a switch needs to be added in series with
the diodes such that each of the DC feeds can be isolated separately.
NOTE 2: The definitions of independent power feeding, dependant power feeding, switched power feeding, combined
power feeding reported in Table 2 as power feeds 1 to 4 are described as follows:
(1) Independent power feeding: Multiple power input interface feeding a set of power supply coupled in parallel
on their outputs to a single load within the ICT equipment.
(2) Dependent power feeding: Multiple power input interface associated with a single load interface in the ICT
equipment. The inputs are switched or combined in managed power interface defined in (3) and (4) in order
to power the single power supply within the ICT equipment.
(3) Switched power feeding: Method by which two power inputs are managed such that one input is always
available to power a single power module within the ICT equipment with the use of a inputs power switch
selector.
(4) Combined power feeding: Method by which two power inputs are managed such that one input is always
available to power a single power module within the ICT equipment by using the reverse bias characteristic of
a two diode common cathode module.
The mixed system configurations with dependant power feeds (switched or combined) that present either -48 VDC and
up to 400 VDC or a -48 VDC and an AC supply are not considered as viable solutions and as such are not presented in
Table 2. The main reason is that the voltage differential between the -48 VDC and the stated high voltage input supply
in both these system configurations is too large to develop a practical ICT on-board converter.
6 Back feeding protection
When the ICT equipment has more than one supply connection, there is the risk of back-feedi
...