Download TR41-00-08-051A-UL-Attchmt-OutlineForInvestigation

TR-41 00-08-051
SUBJECT XXXX
OUTLINE OF INVESTIGATION
FOR
EQUIPMENT WITH REMOTE FEEDING TELECOMMUNICATION CIRCUITS
INTENDED FOR RETRO-FIT IN LEGACY TELECOMMUNICATION EQUIPMENT
Issue Number 1
August 17, 2000
COPYRIGHT  2000 UNDERWRITERS LABORATORIES INC.
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CONTENTS
FOREWORD
INTRODUCTION
1
2
3
Scope
General
Definitions
CONSTRUCTION
4
5
Accessibility
Clearance, Creepage Distances and Solid Insulation
PERFORMANCE
6
7
8
Electric Shock
Electric Strength Test
Force Test
MARKINGS
9
Markings
3
EQUIPMENT WITH RFT CIRCUITS – SUBJECT XXXX
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FOREWORD
A. This Outline of Investigation contains basic requirements for products covered by Underwriters
Laboratories Inc. (UL) under its Follow-Up Services for this category within the limitations given below
and in the Scope section of this Outline of Investigation. They are subject to revision as further
experience and investigation may show is necessary or desirable.
B. The observance of these requirements by a manufacturer is one of the conditions of the continued
coverage of the manufacturer’s product.
C. A product which complies with the text of this Outline of Investigation will not necessarily be judged to
comply with the Outline of Investigation if, when examined and tested, it is found to have other
features which impair the level of safety contemplated by these requirements.
D. A product employing materials or having forms of construction differing from those detailed in the
requirements of this Outline of Investigation may be examined and tested according to the intent of
the requirements and, if found to be substantially equivalent, may be judged to comply with the Outline
of Investigation.
E. UL, in performing its functions in accordance with its objectives, does not assume or undertake to
discharge any responsibility of the manufacturer or any other party. The opinions and findings of UL
represent its professional judgment given with due consideration to the necessary limitations of
practical operation and state of the art at the time the Outline of Investigation is processed. UL shall
not be responsible to anyone for the use of or reliance upon this Outline of Investigation by anyone.
UL shall not incur any obligation or liability for damages, including consequential damages, arising out
of or in connection with the use, interpretation of, or reliance upon this Outline of Investigation.
F. Many tests required by the Outline of Investigations of UL are inherently hazardous and adequate
safeguards for personnel and property shall be employed in conducting such tests.
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INTRODUCTION
1
Scope
1.1
This Outline of Investigation covers supplementary requirements for communication circuit packs
and shelves with remote feeding telecommunication circuits intended for retro-fit (backwards
compatible) with frames, shelves and backplanes.
1.2
The equipment covered is limited to that which forms part of a TELECOMMUNICATION
NETWORK up to and including the demarcation point. The circuitry associated with this type of
equipment is intended to be installed and located in SERVICE ACCESS AREAS only, which may
or may not be provided by the equipment housing. This equipment is generally considered
Central Office Equipment, though it may be deployed elsewhere in similarly controlled
environments.
1.3
This Outline supplements UL 60950, Third Edition because of the need for backwards
compatibility of new equipment with equipment already installed in the existing
telecommunications infrastructure. In particular, spacings associated with connectors and similar
interfaces that are part of the installed base are incompatible with UL 60950 based on the existing
working voltages. Certain types of equipment have provided voltage biased circuitry for many
years which are directed within the TELECOMMUNICATION NETWORK. These high-voltages
are utilized to power signal repeaters and remote terminal equipment where AC power cannot be
relied upon for operation due to the tremendous downtime present with AC utility functionality. The
circuits are not used in customer accessible areas where accidental contact would present a
potential hazard. Network service personnel are considered to be aware of the apparent hazards
associated with this type of circuitry.
1.3.1
Examples of equipment requiring backwards compatibility are:
 Circuit packs or cards with existing or new technologies designed to be installed into shelf
assemblies that form part of a service provider’s existing infrastructure.
 Shelf assemblies intended as replacements for existing shelf assemblies mounted in frame
line-ups that form part of a service provider’s existing infrastructure.
 Shelf assemblies or enclosures intended as replacements for existing service provider
infrastructure equipment that are required to be compatible with cards or circuit packs already
in service.
1.4
A product that contains features, characteristics, components, materials, or systems new or
different from those covered by the requirements in this Outline of Investigation, and that involves
a risk of fire or of electric shock or injury to persons shall be evaluated using appropriate
additional component and end-product requirements to maintain the level of safety as originally
anticipated by the intent of this Outline of Investigation. A product whose features, characteristics,
components, materials, or systems conflict with specific requirements or provisions of this Outline
of Investigation does not comply with this Outline. Requirements shall be revised and adopted in
accordance with the methods employed for development and implementation of this Outline of
Investigation.
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2.
General
2.1
This Outline is to be used in conjunction with in the Standard for Safety of Information Technology
Equipment Including Electrical Business Equipment, UL 60950 Third Edition. With the exception
to the requirements stated within this Outline, and as permitted in 2.2., equipment with Remote
Feeding Telecommunication Circuits shall comply with all applicable requirements in UL 60950,
Third Edition.
2.2
These requirements may also be used for investigations of equipment with remote feeding
telecommunication circuits to UL 1950, Third Edition provided that the appropriate parallel
requirements referenced in this Outline are applied.
3.
Definitions
3.1
For the purpose of this Outline of Investigation, the following definitions apply that are not already
defined in UL 60950, Third Edition. Terms in SMALL CAPS that are not defined in this Outline are
defined in Sub-clause 1.2 of UL 60950.
3.2
RFT CIRCUIT (Remote Feeding Telecommunication Circuit) – a SECONDARY CIRCUIT within
the equipment, intended to supply or receive d.c. power via a TELECOMMUNICATION
NETWORK at voltages exceeding the limits for TNV CIRCUITS, and on which overvoltages from
TELECOMMUNICATION NETWORKS are possible.
3.3
RFT-V Circuit - an RFT CIRCUIT which is so designed and protected so that under normal
operating conditions and single fault conditions the voltages are limited and the accessible area of
contact is limited (see 4.1).
CONSTRUCTION
4.
Accessiblity
4.1
In a SERVICE ACCESS AREA, bare parts of RFT CIRCUITS shall be located or guarded so that
accidental shorting to SELV CIRCUITS or to TNV CIRCUITS, for example by TOOLS or test
probes used by SERVICE PERSONNEL, is unlikely. RFT CIRCUITS are not required to be
guarded from unintentional contact with bare parts during service operations involving other parts
of the equipment.
4.2
In a RESTRICTED ACCESS AREA, the requirements for OPERATOR ACCESS AREAS apply,
except contact with bare parts of an RFT circuit is permitted by the test finger, figure 2A.
5.
Clearances, Creepage Disances and Solid Insulation
5.1
Clearances, Creepage Distances and Solid Insulation requirements associated with REMOTE
FEEDING TELECOMMUNICATION CIRCUITS are determined based on the working voltage of
the circuit in accordance with either:
a.
b.
Sub-clauses 2.10 and 5.2 of UL 60950, Third Edition; or
Clause 7 of this Outline.
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PERFORMANCE
6.
Electric Shock
6.1
An RFT circuit is so designed and protected that under normal operating conditions the voltage,
current, power and the accessible area of contact are limited.
6.1.1
The steady state open circuit voltage from each conductor to earth that is supplied to a
TELECOMMUNICATION NETWORK shall not exceed:
a)
140 V d.c.; or
b)
200 V d.c., provided that a monitoring device is used that limits the current to the
following:
1). In the event of a single fault, with and without the RFT-V CIRCUIT conductor being
earthed, the output voltage during the first 200 ms for each RFT-V CIRCUIT conductor with
respect to earth, shall not exceed the limits of figure 2D of UL 60950, Third Edition as
measured across a 5 k   2% resistor with all other loads disconnected. After 200 ms,
the above limits apply.
2). With one conductor of the RPF CIRCUIT earthed, the open circuit voltage of the other
conductor shall not exceed the maximum RPF CIRCUIT supply voltage after 200 ms. For
RPF CIRCUIT whose voltage exceeds 140 V d.c. under normal operating conditions, the
current between the other conductor and earth measured through 2 k   2%, under any
external load condition, shall not exceed the relevant line-to-earth limit given in figure 1
below. After 10 s, the current shall not exceed 10 mA d.c.
1000
I d.c. (mA)
100
line to line
line to earth
10
1
0.01
0.1
1
10
time (s)
Figure 1 - Maximum current after a single fault
6.1.2
The maximum power that can be supplied to any load connected to the TELECOMMUNICATION
NETWORK shall be limited to 100 W after 1 second.
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7.
Electric Strength Test
7.1
Clearance, Creepage Distances and Distance through Insulation between the Remote Power
Feeding Circuit and TNV, SELV or Accessible Parts shall withstand the application of an electric
strength test in accordance with sub-clause 5.2 of UL 60950 at a test potential of 1000 V ac rms
(1414 V dc/peak) for a period of 1 minute without insulation breakdown.
8.
Force Test
8.1
When provided with a guard or cover that prevents unintentional contact during normal operation,
the 10 N Steady Force Test is not applied to wire-wrap pins utilized on telecommunication
equipment covered by this Outline of Investigation.
MARKINGS
9.
Markings
9.1
NETWORK TELECOMMUNICATION EQUIPMENT utilizing voltages higher than those covered
by TNV-1 or TNV-3 limits shall be provided with a marking, readily visible to service personnel,
including the following or equivalent text:
CAUTION
Risk of Electric Shock.
Voltages up to XXX may be present on telecommunication circuits.