Common Systems Connection Standards AT&T Services, Inc
Date: August 31, 2007 ATT-TP-76450, Issue 9
Copyright ©2004 – 2006, AT&T Knowledge Ventures
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Page 9
2.5 Fusing of Capacitors
Equipment incorporating the use of power distribution apparatus which uses capacitors shall be
fused to protect the power distribution bus from a shorted capacitor. Fuse and protection
information must be provided in the supplier's response documentation to be in compliance with
this item. The equipment manufacturer shall provide a label indicating equipment capacitors
must be pre-charged prior to power up the equipment.
2.6 POWER DISTRIBUTION DELIVERY
All power distribution products must meet the requirements listed in Section 1 of this document.
AT&T approved Power Distribution Units (PDU) shall be used to power transport and data
equipment. Power is distributed to the NE from Battery Distribution Fuse Bays (BDFB) or an
arrangement utilizing a Secondary Power Distribution Unit (SPDU). The SPDU is smaller than
a BDFB in physical size and capacity. Direct feeds to the NE from the BDFB will be considered
on a case by case basis when required. NE will not be directly fed from Power Board
Distribution. Contact the AT&T Common Systems Power Technical Staff when requesting direct
BDFB feed.
PDUs that are independent of the network element but included as part of the total package
must meet the requirements listed in this section; must be approved for use, and should be
identified by an associated AT&T PID (Product ID) number assigned by the AT&T Power
Technical Staff
All approved PDUs shall be equipped with at least one of these forms of overprotection
devices, (1) GMT Fuses, (2) Telpower® Fuses, (3) Telecom TLS Fuses, (4) DC Rated Circuit
Breakers. (note: circuit breakers in PDUs shall only be fed by circuit breakers).The
recommended form of DC power distribution is GMT fuses, Telpower® fuses, Telecom TLS
Fuses, or Circuit Breakers, in that order. The size of the DC requirement will serve as the
primary qualifier, but fuses are the preferred method of over-current protection.
• GMT Fuses – Generally sized to accommodate 0.18 – 20 amp requirements. List 2X
demand should not exceed 80% rated fuse size.
Telpower® Fuses – Exclusively produced by Cooper-Bussmann, these fuses are available in
sizes from 3 amps to 600 amps, packaged in Blue to signify DC only. Telpower® fuses are also
available in various styles for different needs. Some of the approved styles commonly seen are
TPA, TPL, TPS and TPN. All Telpower® fuses should be sized at 125% of List 2X load (List 2X
load not greater than 80% of their fuse faceplate rating).
• Telecom TLS Series Power Fuses – Exclusively manufactured by Littelfuse shall be
used in the 80-125A sizes with the Canadian Shunt TFD101-011-01 fuse
disconnect/fuse holder. Littelfuse TLS fuses should be sized at 125% of List 2X load
(List 2X load not greater than 80% of their fuse faceplate rating).
