1. Communication Markets Division © 3M 2007. All Rights Reserved. Telecom Visit for Noise Mitigation Improve Network Performance with 3M™ Solutions

2. 2 Communication Markets Division © 3M 2007. All Rights Reserved. Overview  While visiting a Telco in Wisconsin, I was able to support the diagnostic review of a noisy circuit. A 965AMS was used to gather the data  Two formulas are used in this presentation and both indicate shielding issues.  Suggestion - Steps should be taken to identify bonding and grounding issues.

3. 3 Communication Markets Division © 3M 2007. All Rights Reserved. 965 AMS Readings of Circuit 75 dBrnC 33 dBrnC 108 dBrnC First Test indicates a good balanced pair. The high PI indicates shield, grounding or a power problem. Second test takes a flat filter PI reading and subtracts the PI reading measured with a C message filter. 33dBmC suggests a power quality problem. 80 dBrnC 33 dBrnC 113 dBrnC 113 -108 = 5 ≥30 dBrnSuggest a Power Quality Problem ≥20 dBrn but ≤ 30 dBrnBonding, Grounding and Power Quality Problem ≤20 dBrnBonding and Grounding Problem

4. 4 Communication Markets Division © 3M 2007. All Rights Reserved. Corrective Action  Create a Map or use a paper copy of the print  Visit closures, splices, cabinets and all other accessible cable opening to:  Verify all shields are bonded together  Verify grounds are connected  Take readings at each location:  AC Voltage  PI and CN  VBSA (Follow and chart strongest harmonics)

5. 5 Communication Markets Division © 3M 2007. All Rights Reserved. Bonding and Grounding Recommendations  Inspect Bonding and Grounding.  Bond all plant “CO” side and “Field” side together.  Ground strategically to reduce noise.  Verify grounding conditions.  Use 6awg for anything greater then 5 lines. Solid is preferred when buried.  Use 10 awg for home NI grounding under 5 lines.  Stay away from 12 awg for grounding.  Use 4460-D or 4462 Shield Bond Connectors for cable sheaths.

6. 6 Communication Markets Division © 3M 2007. All Rights Reserved. Bonding and Grounding  When possible, bond telephone ground rods to power ground rods or use power ground rods. (This provides a return path for induced current)  Bond all shields (Exchange to Distribution at XB) Plant Engineers may decide to not ground based on other considerations: i.e.: Dairy Farms, long aerial drop wires fed from buried plant, etc… Plant Engineers may add more grounding based on power company distribution.

7. 7 Communication Markets Division © 3M 2007. All Rights Reserved. Open or Corroded Shields Use the Opens By Ratio Formula.

8. 8 Communication Markets Division © 3M 2007. All Rights Reserved. Voice Band Spectrum Analyzer 1 2 3 Press or to start measuring on an inactive pair. You can also dial quiet termination to get readings.

9. 9 Communication Markets Division © 3M 2007. All Rights Reserved. Voice Band Spectrum Analyzer Toggles between and. Selects to measure PI and CN. Selects for 0 to 2560 or 0 to 8 kHz.

10. 10 Communication Markets Division © 3M 2007. All Rights Reserved. Readings From Telco All readings taken had similar harmonic influence.

11. 11 Communication Markets Division © 3M 2007. All Rights Reserved. Looking at the Harmonics 180 300 420 540 Peak harmonics to keep note of. While the test formulas point to shielding issues it is good to track harmonics. These readings suggest potential problems with transformers and /or capacitor banks.

12. 12 Communication Markets Division © 3M 2007. All Rights Reserved. Harmonic SignatureTypical Diagnosis 60 HzBadly out-of-balance three-phase power lines, or single- or two-phase power lines, or poor neutral conductivity. Poor balance does NOT create 540 Hz problems but it can amplify the 9th harmonic. 180 HzLeading power factor in the power system or a saturated transformer. 300 Hz is symptom of poor balance in the power system often noted in conjunction with high 60 Hz interference 300 Hz with 420 Hz and even harmonics May be caused by 6-pulse rectifiers or an impedance irregularity in the power distribution system 300 Hz and/or 420 Hz together with 660 Hz and/or 780 Hz signals Often the result of more capacitance on some phases than others in the power distribution system. This condition may be caused by a blown fuse at a capacitor bank or capacitor banks installed on single or two phase power lines. 420 Hz and/or 300 Hz with 660 Hz and/or 780Hz are of Often the result of more capacitance on one or more phases than on the other phase conductors in the power distribution system. This may be caused by a blown fuse at a capacitor bank or capacitors installed on single- or two-phase circuits or buried power distribution lines. 540 HzThe result is power system circuit resonance. This may be made much worse by oversized shunt capacitor banks or buried power lines. A circuit is considered resonant when any one harmonic, generally 540 Hz, is 6 dB higher than the next highest harmonic (very common condition) 660 Hz with 780 Hz with even harmonics The result of 12-pulse rectifiers 660 Hz and/or 300 Hz with 420 Hz and/or 780 Hz Often the result of an impedance disparity. This can be a result of more capacitance on one or more phases than on the other phase conductors in the power distribution system. This may be caused, in turn, by a defective capacitor bank or capacitors installed on single- or two-phase circuits or buried power distribution lines. 780 Hz and/or 300 Hz with 420 Hz and/or 660 Hz Often the result of more capacitance on one or more phases than on the other phase conductors in the power distribution system. This condition may be caused by a blown fuse at a capacitor bank or capacitors installed on single- or two-phase circuits or buried power distribution lines. 900 HzCommon when the area being served has high impedance ground connections combined with numerous buried power distribution lines. This could also be caused by transformers wired in an open “Y” configuration. 1020 HzCommon if the area being served has high impedance ground connections combined with numerous buried power distribution lines.