Upload
lybao
View
236
Download
7
Embed Size (px)
Citation preview
9/10/2014
Telecommunications Grounding and Bonding Generic
ChandrashekarTechnical Manager (India & SW Asia)
Purpose and scope of TIA-607-B TIA-607-B grounding is normative and applies to entire building, not
just data center
TIA-607-B, “Generic Telecommunications
Bonding and Grounding (Earthing)
for Customer Premises”, is now
approved!
Scope now includes
grounding of ITE
What is TIA-607-B?Scope: Specifies requirements for a generic telecommunications bonding and grounding infrastructure, and its interconnection to other systems, for locations where telecommunications equipment will be or are installed
Major revision of J‐STD‐607‐A:• Includes G&B of telecommunications spaces (distributors and computer rooms)
• Continued harmonization efforts (as practicable) on terminology and practices with international standards
Scope of TIA‐607‐B
TBB
DistributorsDistributorsComputer Rooms
Computer Rooms
TGB TMGBTGB TMGB
Equipment in Cabinets and Racks
“Rather than relying on the ac power cord ground wire, it is desirable that equipment be
grounded in a verifiable manner as described in
this Standard.”
Figure 7—Example of three methods to bond equipment and racks to ground
TIA-607-B:
Telecommunications Bonding Backbone (TBB)
• Purpose of TBB is to reduce potential differences between interconnected telecommunications systems on different floors
• Originates at TMGB and extends throughout building using telecom pathways
• Connects TGBs that exist in each distributor
6
TIA-607-B TBB sizing
Conductor sizing isn’t only about electrical issues…
Size matters!
Standards call for a minimum #6 AWG for mechanical strength
Source: Picture from Internet
Supplemental bonding grid construction per TIA-607-B
• #6 AWG round wire or 2” wide copper strips bonded at intersections
• Minimum grid density is 3 m (10 ft) centers
• Minimum 1/0 bond to TGB/TMGB
Example supplemental bonding grid
Example SBG construction
Make aisle grounds convenient to racks and cabinets
Cross aisle grounds every 10 feet
•Use #6 AWG wire•Use pedestal grounding clamps at conductor intersections• Bond to AC power ground through a local TGB
TEBC to rack connector – TIA-607-BOnly 2-hole mechanical is allowed for this application. Concerns:(1) Vibration test was done at one amplitude and
frequency, which is different from what data installations experience
(2) No consideration for temperature fluctuation(3) No consideration for stress relaxation
Mesh-BN: a collection of components (As per CENELEC documents, includes TIA-942’s Data Center Grounding Infrastructure as the “Supplemental Bonding Network” and IEEE Std 1100 calls the MCBN), per TIA-607-B
Information technology
equipment (ITE)
Racks and cabinets
Cabling pathways
(not shown)
Building steel
Supplemental bonding grid
(SBG)
Conduits
Rack bonding conductor (RBC)
Preventing loose busbar connections
12
Two-hole compression lugs required
on TGB & TMGB
(Type LCC-W)
BICSI-607 stainless steel TGB hardware stack-up (requires locking washer, and
stainless or SiBr hardware)
(Parts HDW1/4-KT, HDW3/8-KT)
13
BICSI Telecommunications Distributions Methods Manual (12th) on the TGB and TMGB
…The same considerations as are
found in TIA-607-B
14
ANSI/NECA/BICSI-607-2011 busbars
Panduit recommendation on busbar hole patterns: pick a pattern and stick
with it. It’s confusing to have
multiple hole patterns later.
Recommend using the BICSI/TIA hole pattern, as it is well defined and known
in industry.
What else needs to be bonded?
• IEEE studies have indicated that the point of diminishing financial returns with respect to lightning strikes is 2 meters (6 feet)
• Bond anything that could become charged that a person could bump while working on a rack/cabinet for safety
• Therefore, bond any conductive path within six feet of your racks/cabinets
Bond cable tray and ladder rack sections
Split bolts – use tin plated if outdoors (SBC & SBCT,
respectively)
#6 AWG conductor, green w/yellow jacket
– OR –
Wyr-Grid and GRIDRUNNERhardware automatically bonds sections, eliminating the need for jumper wires
Specify systems that automatically bond to
reduce chances of error
Remote zone enclosures and TIA-607-B
TIA‐607‐B“Distributors” need TGB/TMGBReferences TIA‐568‐C.0 for definitionTIA‐568‐C.0, 4.4 Distributors“Distributors provide a location for administration, reconfiguration, connection of equipment, and for testing. Distributors can be configured as interconnections or cross‐connections…”Figure 3 of the same document shows distributors starting at “Active equipment”
My conclusion… If it has active equipment, then it needs grounding
Sizing the conductor•A TBB, per TIA‐607‐B, originates at the TMGB. It bonds TGBs to the TMGB (5.2.4)•A TEBC connects racks to the TMGB/TGB (7.1)•TGB is located “as close as practicable to the panelboard”•“The TEBC shall be a continuous copper conductor that is sized not less than a No. 6 AWG or as the largest size equipment grounding conductor in he ac branch power circuit(s) serving the racks/cabinet lineup.
17
Panduit grounding research
• Panduit research over the last two years has found the presence of phase imbalance on the telecommunications grounding system in the steady‐state
• Frequencies are powerline and the first couple of harmonics
Observations:• High building steel currents•UPSs are at end of line-up creating power imbalance in the ground conductor•No noticed network degradation on the part of network operators
19Episodic/transient research
• 7 MHz transient measured on ACEG at CRAH, but not detectable at closest rack• Conclusion so far: mesh bonding and separate circuits from the AC panel are effective means of mitigating issues with transients
• Flat braids have not been shown to offer a tangible benefit for this application
Tektronix TPS 2024
CRAC PanelCRAC Panel
AH Systems BCP‐512 Probe AH Systems BCP‐512 Probe (high bandwidth)
Rack bonding conductor
Grounding rules of thumb for optimum surge suppression
“Optimum performance of surge protectors is achieved at five Ohms or below. Several manufacturers of electronic equipment also require five to ten Ohms as a maximum resistance for their gear to work correctly.”
‐ Ditek “Technical White Paper: Grounding 101”
20
Two categories of facility:1. Minimum requirements: maintain 25Ω throughout year, recommends at least two electrodes
2. Enhanced requirements for critical facilities: designed to have 10Ω or less (and “preferably 5Ω or less”)
– Public safety facilities– Military installations– Data centers– Web hosting facilities– Central offices
“Where telecommunications equipment is distributed throughout a structure and may be interconnected by metallic links, the minimally required grounding system may not be adequate. Facilities with advanced requirements or distributed equipment will benefit from the addition of a building perimeter ground loop.”
21
TIA-607-B-1 - External Grounding* TR 42.16 voted to adopt as normative on June 6, 2012
Design specifications, per TIA-607-B-1
• Commission a soil resistivity study– The most common method of measuring average soil resistivity is the four‐point method– Require a series of readings in different locations to get a better idea of the soil conditions
• Require measurements of the ground system resistance as verification of the design– 3‐pole fall‐of‐potential method (if room is available, and the ground is not connected to the
power system)– Clamp‐on meter
22
TIA-607-B-1 potential equalization design highlights
23
Summary