Grounding Practice at Data and Communications Centers. David Brender, P.E., CPQ National Program Manager Copper Development Association Inc.

Transcription

1 Grounding Practice at Data and Communications Centers David Brender, P.E., CPQ National Program Manager Copper Development Association Inc.

2 Overview of This Presentation Elements of building wiring and grounding that can alleviate or cure power quality problems before they affect operations

3 Basic Tenet Grounding and bonding are the foundations of a facility. Without a solid foundation, a building will collapse.

4 It s starting point National Electrical Code But not sufficient for power quality

5 Plan For Today: Power quality fundamentals Case study on surge suppressors Case study of data center Case studies of communications facilities Recommended practice

6 What Constitutes a Good Data Center? 1. Above-code grounding 2. Above-code wiring 3. Attention to detail

7 Larger Data Center Involta. Cedar Rapids, Iowa - 18,000 sq. ft. Akron, OH 26,400 sq. ft.

8 Substation is Next Door

9 Dual Electric Circuits Dual utility feeds, kva transformers, kva generators, A&B circuitry

10 Exterior Grounding 500 kcmil ground ring surrounds entire building Vertical electrode (rod) approx. every 100 feet Inspection wells

11 A and B Circuits Dual circuitry throughout building

12 A and B circuits

13 Dual Feed to Cabinets

14 Cabinets to Overhead Collector 3/0 copper grounding conductor over each rack Each rack is bonded with #6 AWG

15 Collectors go to SGB 3/0 AWG grounds from each row collect at bus in each room

16 Where required - Tinning Tinned copper bus Stainless steel hardware

17 From SGB to MGB 3/0 from each SGB bus collect at MGB, then 500 Kcmil to outdoor ground ring

18 Standards 5 Ohm maximum grounding standard Annual inspection Copper conductors only for reliability

19 Very Large Center Markley Group, 800,000 Sq. Ft. in Boston

20 2 Utility Vaults, 5 MVA each

21 Each Rack to Overhead Bus

22 Each Room has Ground Bus then to MGB

23 Separate Runs to Master Ground Bus

24 Master Ground Bus (MGB) in Basement Note that all conduits are labelled. MGB located at lowest point in building.

25 Imagine a Joint Every 10 Feet Never Rely on Conduit as Ground Path Always use a full-sized separate ground conductor

26 A Well Grounded Communications Center

27 Note tower in rear

28 Gas piping is bonded

29 Labeled so no one removes

30 Conductor welded to base, not tower leg

31 Coax braid bonded on vertical run

32 Then to strap at bulkhead

33 Inside radio room

34 Halo ground with all cabinets bonded

35 One Mistake

36 Recommended Practices

37 Leads as short as possible Surge Suppressors

38 Surge Suppressors - at the service - at the panel board - at the load

39 Surge Suppressors at the service level Category C devices 150 ka per mode minimum

40 at the feeder level Category B devices 75 ka per mode Surge Suppressors

41 Surge Suppressors at the device level Category A devices 25 ka per mode

42 Importance of Surge Suppressors and Robust Low Resistance Grounding Florida Data Center

43 Runs ATM network Florida Data Center

44 Direct lightning hit Meter was blown off wall

45 Everything was bonded together No ring ground but low resistance

46 Surge Suppressors All-mode protection: φ-φ, φ-g, φ-n, N-G Listed to UL 1449, Version 3 High Joule rating Have filtering, fuses, indication Must be well-grounded

47 Separate Circuits Sensitive loads should be separated: Separate branch circuits Separate ground conductors Separate panelboards Separate feeders Separate transformers BUT everything must be bonded together

48 Voltage Drop Limit receptacles to 3-6 per circuit Limit voltage drop to <3% or less wire gage circuit length Check for ground loops Check for N-G bonds

49 Breakers and Plugs Bolt-in circuit breakers Twist-lock plugs/receptacles

50 Double Nuts and Lockwashers Help control vibration

51 Do Not Daisy Chain Grounding Earth must never be used as a conductor

52 Grounding in Star Pattern

53 Shielded Isolation Transformer Electrostatic shield between primary and secondary Delta primary but Wye secondary traps harmonics

54 Safely Handling Harmonics Use double size neutral or one neutral per phase conductor

55 have double-sized neutrals Harmonic rated panels

56 Shielded isolation transformer or K-rated transformer (K-13 or higher) Transformers

57 Bentonite is the recommended backfill Backfill Materials Be wary of anything containing graphite

58 Check resistance of grounding electrode system annually (or more often as conditions dictate) Our ground-resistance requirement was four ohms, but we like to maintain a maximum of two ohms at this point, and that s checked once a year to make sure it hasn t risen. CoSentry Data Center

59 Human Failures People make changes to the electrical system all the time They seldom document the changes Have a Written Plan Insist contractors follow it!

60 Compare Orange County Large diameter sweeping turns

61 Start With Low R Grounding

62 Lightning Protection

63 Connect All Metal Conduits Together To the Ground Ring: multiple ground rods tie-in building steel connect all metallic underground pipes lightning protection system

64 Surge Suppression

65 Building Steel is an Antenna Don t use building steel as the down conductor or bonding point Like asking for trouble

66 Equipment Grounding Conductor Use a full-sized EGC and 200% neutral, or separate neutrals Don t rely on conduit

67 Ground Resistance is Important Lightning protection and surge devices MUST have a low impedance ground to discharge the energy Lightning system without good grounding system may make matters worse than none

68 Interior: Conduit is Poor Ground Path Always use a full size copper neutral and equipment grounding conductor Conduit has joints every 10 feet

69 Interior: Voltage Drop Limit receptacles to 3-6 per circuit Limit voltage drop to <3% or less wire gage circuit length Check for ground loops Check for N-G bonds

70 Power quality isn t taught in school A man s got to know his limitations. - Clint Eastwood as Dirty Harry Call in a professional when there is doubt.

71 True-isms 1. Exceed the Code, but don t violate the Code! (Code minimum is one step above illegal) 2. You don t get what you expect, you only get what you inspect. 3. Have a written plan and procedures. Insist contractors follow it. 4. Get the grounding and bonding right before anything else. Most lightning and transient problems can be cured at minimal cost.

72 Free Educational Materials/Seminars Case Histories Recommendations Bibliography DVDs Seminars with PDH s

73 Thanks for your attention David Brender Office: Cell: