Nortel DMS-100 Series Maintenance Manual
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Nortel DMS-100 Series Maintenance Manual

Digital switching systems power and grounding routine
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297-1001–350
DMS-100 Family
Digital Switching Systems
Power and Grounding Routine Maintenance
Manual
Applies to all BCS and PCL levels
Standard 02.02
August 1997

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  • Page 1 297-1001–350 DMS-100 Family Digital Switching Systems Power and Grounding Routine Maintenance Manual Applies to all BCS and PCL levels Standard 02.02 August 1997...
  • Page 3 Digital Switching Systems DMS-100 Family Power and Grounding Routine Maintenance Manual Publication number: 297-1001-350 Product release: Applies to all BCS/PCL levels Document release: Standard 02.02 Date: August 1997 1988, 1989, 19941997 Northern Telecom All rights reserved. Printed in Canada and printed in the United States of America. NORTHERN TELECOM CONFIDENTIAL: The information contained in this document is the property of Northern Telecom.
  • Page 5 Publication history August 1997 Standard 02.02 was issued to incorporate editiorial markup and customer feedback. June 1994 Standard 02.01 was issued for the following reasons: to compose NTP 297-1001-350 in a new typographical style (restructured format). to comply with the generic design intent, terminology, and definitions of applicable Northern Telecom Corporate Standards and NTP 297-1001-156, DMS-100 Family Power Distribution and Grounding Guide...

  • Page 7: Table Of Contents

    Contents About this document Application of this document ix References ix Prerequisite references x Informative references x 1 Introduction 1–1 1.1 Definitions 1–1 battery return (BR): 1–1 battery return reference (BRR): 1–1 bonding: 1–1 bonding network (BN): 1–1 building principal ground (BPG): 1–1 common bonding network (CBN): 1–1 DMS-100 Family: 1–2 DMS single point ground (DMS SPG): 1–2...
  • Page 8 vi Contents 3.1.1 Maintenance records 3–1 3.1.2 Maintenance action record 3–17 3.1.3 Tools 3–17 3.2 Power plant critical limits 3–18 3.3 Power plant maintenance schedule 3–19 3.4 Power plant checks 3–20 3.5 Power plant safety checks 3–21 3.6 Power plant fuse checks 3–22 3.7 Charging equipment checks 3–22 3.8 Battery equipment checks 3–24 3.8.1 Maintenance intervals 3–24...
  • Page 9 Contents vii Figure 3–2 Sample battery electrical and specific gravity measurements record 3–4 Figure 3–3 Sample charging plant capacity and reserves data record 3–5 Figure 3–4 Sample telephone number record 3–6 Figure 3–5 Standby engines—office loads and battery reserves record 3–7 Figure 3–6 Sample power plant alarm check record 3–8 Figure 3–7...

  • Page 11: About This Document

    About this document This document contains maintenance procedures for checking the power and grounding installation for DMS-100 Family (DMS-100F) switch equipment. The power-related maintenance procedures include various checks of the DMS battery plant and rectifiers, an operational exercise of the standby power system, and a method for removing and restoring power in an emergency situation.

  • Page 12: Prerequisite References

    x About this document Prerequisite references NTP 297-1001-156: DMS-100 Family Power Distribution and Grounding Guide TR-NWT-000295: Bell Communications Research Technical Reference, Isolated Ground Planes; Definition and Application to Telephone Central Offices Rural Electrification Administration (REA) Telecommunications Engineering and Construction Manual, Section 810: Electrical Protection of Electronic Analog and Digital Central Office Equipment ANSI/NFPA No.

  • Page 13: Introduction

    1–1 1 Introduction The following definitions conform as closely as possible to those of the National Electrical Code (NEC) and the Canadian Electrical Code (CEC). 1.1 Definitions battery return (BR): A conductor that carries the –48 V return current. Although BR conductors are not grounding conductors, they are referenced to ground by the battery return reference (BRR) conductor of the serving dc power plant.

  • Page 14: Dms-100 Family

    1–2 Introduction reinforcing rods, metallic plumbing, ac power conduit, ac equipment grounding conductors, bonding conductors, and cable racks. The CBN is a mesh topology and is connected to the building grounding electrode system. DMS-100 Family: Designates the family of digital multiplexed switching systems which include the DMS-100, DMS-100/200, DMS-100 switching cluster, DMS-100 switching network, DMS-200, DMS-250, and DMS-300.

  • Page 15: Ground

    Introduction 1–3 the frame lineups. It is recommended that no other conductors are connected to the framework ground bus. ground: A metallic connection, whether intentional or accidental, between an electric circuit or equipment and the earth, or some conducting body that serves in place of the earth.

  • Page 16: Single Point Ground (Spg)

    1–4 Introduction single point ground (SPG): A single connection used to reference equipment or a system to ground. In an ideal IBN arrangement, no dc current flows through the single point connection unless a fault condition exists. vertical ground riser (VGR): A continuous conductor extending ground potential throughout the height of a multifloor building.
  • Page 17 Introduction 1–5 floor ground bar FGB: isolated bonding network IBN: isolated ground plane IGP: isolated ground zone IGZ: isolated system ground ISG: logic return logic return bar LRB: logic return equalizer LRE: low voltage disconnect LVD: main ground bus (BCC terminology MGB: master ground bar (REA terminology MGB:...

  • Page 18: Cross Reference Of Terms

    1–6 Introduction 1.3 Cross reference of terms Table 1–1 is a quick cross-reference of terms used by Northern Telecom, the BOCs, REA, and others. Table 1–1 Cross reference of terms OTHERS battery return (BR) –48 V return – battery ground –...

  • Page 19: Overview

    2–1 2 Overview The power distribution system supplies controlled and protected power to DMS switch equipment. The grounding system provides hazard protection for personnel and DMS equipment, and, within accepted standards, immunity from operational and transient phenomena. 2.1 DC power Power from a –48 V power plant is fed through dual primary battery feeders (A feeders and B feeders) to the Power Distribution Centers (PDCs) of the DMS equipment.
  • Page 20 2–2 Overview can be a shelf, frame, or a group of frames. Communication links between functional blocks and to the outside world generally use ac coupling techniques to ensure connectivity. 297-1001-350 Standard 02.02 August 1997...

  • Page 21: Power System Maintenance

    3–1 3 Power system maintenance Operating companies should establish a formal routine maintenance plan for their DMS switch power systems. A maintenance plan is crucial in detecting and clearing potential power system faults before they affect service. The maintenance plan should include the following: routine battery maintenance visual checks and tests of the charging plant exercise of the standby power system operation...
  • Page 22 3–2 Power system maintenance Charging plant capacity and reserves data record: used to list the normal and reserve capacity of the power plant rectifiers. See Figure 3–3. Telephone number record: used to list the telephone numbers of various support and emergency organizations related to the power plant. See Figure 3–4.
  • Page 23 Power system maintenance 3–3 Figure 3–1 Sample pilot cell voltage and specific gravity test record PILOT CELL VOLTAGE AND SPECIFIC GRAVITY TEST RECORD OFFICE: DIVISION: CITY: AREA: DISTRICT: COMPANY: PILOT CELL BATTERY PILOT CELL FLOAT FLOAT SPECIFIC BATTERY ELECTROLYTE DATE VOLTAGE VOLTAGE GRAVITY*...
  • Page 24 3–4 Power system maintenance Figure 3–2 Sample battery electrical and specific gravity measurements record BATTERY ELECTRICAL AND SPECIFIC GRAVITY MEASUREMENTS RECORD CORRECTED SPECIFIC SPECIFIC CELL No. VOLTAGE GRAVITY* REMARKS GRAVITY Individual cell voltage should be: 2.17 0.05 / – 0.04 V/cell. For VRLA batteries, Are there any cells lower than 2.13V? YES____ NO____ use values specified...
  • Page 25 Power system maintenance 3–5 Figure 3–3 Sample charging plant capacity and reserves data record CHARGING PLANT CAPACITY AND RESERVES DATA RECORD OFFICE: DIVISION: CITY: AREA: DISTRICT: COMPANY: NUMBER OF RECTIFIER TOTAL LOAD RECTIFIERS TYPE OF PLANT CAPACITY IN AMPS AVAILABLE DMS-100 Family Power and Grounding Routine Maintenance Manual Applies to all BCS/PCL levels...
  • Page 26 3–6 Power system maintenance Figure 3–4 Sample telephone number record TELEPHONE NUMBER RECORD NAME OFFICE HOME Level II Supervisor Level I Supervisor Power Technician Alternative Power Technician Emergency Engine Coordinator Fire Police Commercial Supply Co. Commercial Supply Telephone No. Other Doctor Diesel Fuel Supplier Address...
  • Page 27 Power system maintenance 3–7 Figure 3–5 Standby engines—office loads and battery reserves record STANDBY ENGINES—OFFICE LOADS AND BATTERY RESERVES RECORD OFFICE DIVISION CITY AREA DISTRICT DATE #1: COMMERCIAL SUPPLY DATA TOTAL ESSENTIAL LOAD IN KW COMMERCIAL SUPPLY CO. TEL. NO. VOLTAGE No.
  • Page 28 3–8 Power system maintenance Figure 3–6 Sample power plant alarm check record POWER PLANT ALARM CHECK RECORD OFFICE: DIVISION: CITY: AREA: DISTRICT: COMPANY: TYPE ALARM (See Note) HIGH RECTIFIER FUSE ALARM DATE INITIALS REMARKS VOLTAGE VOLTAGE FAILURE Note: If used, audible and visual alarms, alarm cutoffs, high float alarms, and low float alarms are to be included in this alarm check.
  • Page 29 Power system maintenance 3–9 Figure 3–7 Sample log sheet for stationary alternator routine engine runs LOG SHEET FOR STATIONARY ALTERNATOR ROUTINE ENGINE RUNS OFFICE: MANUFACTURER MODEL ENGINE ALTERNATOR GENERATOR: KW RATING: FROM: DATE KW LOAD CURRENT VOLTAGE AMBIENT TEMP LUBE OIL ENG.
  • Page 30 3–10 Power system maintenance Figure 3–8 Sample log sheet for mobile alternator routine engine runs LOG SHEET FOR MOBILE ALTERNATOR ROUTINE ENGINE RUNS OFFICE: FROM: TIME SIZE TIME TIME KW LOAD CURRENT VOLTAGE TEMP DATE ENGINE ENGINE ENGINE ENGINE ENGINE PRESS DSPCH DSPCH...
  • Page 31 Power system maintenance 3–11 Figure 3–9 Sample standby power system exercise evaluation report STANDBY POWER SYSTEM EXERCISE EVALUATION REPORT LOCATION:_______________________________________ DATE:_____________ LEVEL 1 SUPERVISOR:____________________________ +12V* –24V* –48V +130V* –130V* FLOAT VOLTAGE IN VOLTS LOAD IN AMPS LOAD ON COMMERCIAL AC NORMAL_________ PEAK_________ IN KILOWATTS...
  • Page 32 3–12 Power system maintenance Figure 3–10 Standby power system exercise control log STANDBY POWER SYSTEM EXERCISE CONTROL LOG OFFICE: LOAD TIME SIZE OF NORMAL OFFICE TRANSFERRED TO BATTERY RESERVE COMMERCIAL STANDBY LOAD (AMPS) STANDBY ENGINE POWER ENGINE LOCATION (AMPS) USED (KW) ESSENTIAL BUILDING ESSENTIAL BUILDING...
  • Page 33 Power system maintenance 3–13 Figure 3–11 Standby power system exercise—stationary engine-alternator log STANDBY POWER SYSTEM EXERCISE—STATIONARY ENGINE-ALTERNATOR LOG OFFICE: MANUFACTURER MODEL ENGINE ALTERNATOR GENERATOR: KW RATING: FROM: DATE KW LOAD CURRENT VOLTAGE AMBIENT TEMP LUBE OIL HOURS TEMP ENGINE PRESS TIME Use the headings that apply.
  • Page 34 3–14 Power system maintenance Figure 3–12 Standby power system exercise—mobile engine-alternator log STANDBY POWER SYSTEM EXERCISE—MOBILE ENGINE-ALTERNATOR LOG OFFICE: FROM: TIME SIZE TIME TIME KW LOAD CURRENT VOLTAGE TEMP DATE ENGINE ENGINE ENGINE ENGINE ENGINE PRESS DSPCH DSPCH CONND DSCTD Reproduce locally.
  • Page 35 Power system maintenance 3–15 Figure 3–13 Battery load test record BATTERY LOAD TEST RECORD LOCATION:_____________________________ DURATION OF TEST:___________ DATE:___________ TERMINAL VOLTAGE TERMINAL VOLTAGE STRING # CELL # AT START OF TEST AT END OF TEST DMS-100 Family Power and Grounding Routine Maintenance Manual Applies to all BCS/PCL levels...
  • Page 36 3–16 Power system maintenance Figure 3–14 Power plant maintenance action required POWER PLANT MAINTENANCE ACTION REQUIRED OFFICE:______________________________ DATE:__________________ REQUESTED BY:________________________ PHONE No.:______________ GROUP OR PROBLEM ACTION ITEM SUBSYSTEM PERSON (DESCRIBE) RECOMMENDED RESPONSIBLE PAGE:_________ OF:_________ 297-1001-350 Standard 02.02 August 1997...

  • Page 37: Maintenance Action Record

    Power system maintenance 3–17 3.1.2 Maintenance action record The performance of power plant maintenance may reveal problems requiring maintenance action. These problems are recorded on the form for power plant maintenance action required (Figure 3–14). This form will be referred to frequently throughout this document.

  • Page 38: Power Plant Critical Limits

    3–18 Power system maintenance 3.2 Power plant critical limits To ensure proper operation of the DMS switch, the power plant must conform to certain limits regarding electrical noise and voltage drops throughout the power distribution system. The following limits on the power system should be verified.

  • Page 39: Power Plant Maintenance Schedule

    Power system maintenance 3–19 3.3 Power plant maintenance schedule Recommended intervals for performing power system maintenance are shown in Table 3–1. These are recommended maximum intervals. If your local practices require smaller intervals, follow your local practices. Table 3–1 Power plant maintenance schedule INTERVAL SUBSYSTEM MAINTENANCE...

  • Page 40: Power Plant Checks

    3–20 Power system maintenance 3.4 Power plant checks Power plant checks consists of the following: power plant safety checks power plant fuses charging equipment checks battery equipment checks standby power system checks standby engine-alternator checks standby power system exercise miscellaneous checks The power plant checks can be performed in any order and on a selective basis.

  • Page 41: Power Plant Safety Checks

    Power system maintenance 3–21 3.5 Power plant safety checks Maintenance routines in power rooms present potentially hazardous situations due to the voltages and corrosive chemicals present. Adhere to strict safety practices to avoid personnel injuries such as battery acid damage to the eyes and acid or electrical burns to the body.

  • Page 42: Power Plant Fuse Checks

    3–22 Power system maintenance 3.6 Power plant fuse checks Perform the following checks on the power plant fuses. Record any problems found in the maintenance action record. Check each fuse for the proper rating and type. Check the spare fuse racks to verify that spare fuses are available. Check the tool area to verify that cartridge-type fuse pullers are available.
  • Page 43 Power system maintenance 3–23 Table 3–2 Power plant data, monitored conditions RECOMMENDED MONITORED CONDITION ALARM CLASSIFICATION MAJOR MINOR High Voltage. The plant output voltage has exceeded its permitted upper limit. Battery-on-discharge. The plant output voltage is below the open circuit voltage of the battery.

  • Page 44: Battery Equipment Checks

    3–24 Power system maintenance 3.8 Battery equipment checks The battery equipment requires periodic maintenance to ensure optimum safety and performance. Battery maintenance consists of routine measurements, cleaning, and the assessment of individual cell conditions. 3.8.1 Maintenance intervals The maintenance and routine frequency of VRLA batteries should be conducted in accordance with the manufacturer’s guidelines for these batteries.
  • Page 45 Power system maintenance 3–25 Table 3–3 Schedule of battery readings and work intervals MAXIMUM DESCRIPTION LOW-GRAVITY HIGH-GRAVITY REFERENCE INTERVAL OF OPERATION CELLS LIMITS CELLS LIMITS Weekly or Pilot cell and Lead-calcium: Figure 3–1 2.17 0.05 / – 0.04 V/cell each visit emergency cell 2.30 /–...

  • Page 46: Trouble Conditions

    3–26 Power system maintenance 3.8.2 Trouble conditions Routinely evaluate the condition of each battery in the battery plant to determine if any maintenance action is required. The following paragraphs describe the trouble conditions of lead-calcium and lead-antimony cells and batteries. The most common troubles with lead-calcium and lead-antimony cells are loose battery post connections, positive plate growth, battery post corrosion, and problems related to low electrolyte levels and high ambient temperatures.

  • Page 47: Post Corrosion

    Power system maintenance 3–27 plate edges do not project beyond the separator. As growth progresses, the plate edges will slowly grow out past the separators and finally touch the inner wall of the container. Positive plate growth will also occur in the vertical plane.
  • Page 48 3–28 Power system maintenance heating, apply a light coating of NO–OX–ID “A” or equivalent compound to the connection. If there are signs of excessive heating, disassemble, clean, and reassemble the connection using local procedures. Apply a light coating of NO–OX–ID “A” or equivalent compound to the connection. Green or blue post corrosion Green or blue corrosion is copper sulfate, which results from corrosion of the copper inner core of the intercell connector.
  • Page 49 Power system maintenance 3–29 Figure 3–15 Typical internal parts of a battery Negative Positive plate plate strap strap Positive plate Plastic separator Negative plate Plate separators Plastic jar ridge for negative plate Plastic jar support bottom DMS-100 Family Power and Grounding Routine Maintenance Manual Applies to all BCS/PCL levels...
  • Page 50 3–30 Power system maintenance Figure 3–16 Positive plate growth Negative plate (black) Separator (gray) Positive plate (white) Lateral growth Normal width Vertical growth Crack in cell jar Normal height (same as negative plate) Cell jar Vertical growth Cracks in cell jar 297-1001-350 Standard 02.02 August 1997...
  • Page 51 Power system maintenance 3–31 Figure 3–17 Battery post and intercell connector corrosion : POST CORROSION: Appears as brown lead-dioxide or white lead-sulfate. Cleaning and a light application of NO-OX-ID“A” or equivalent compound to the connections is all that is required. : INTERCELL CONNECTOR CORROSION: Appears as blue or green copper sulfate.

  • Page 52: Electrolyte Level And Temperature

    3–32 Power system maintenance 3.8.6 Electrolyte level and temperature Electrolyte level and temperature play an important role in the expected life of the battery. At all times after initial charge, the level of electrolyte in any cell must be maintained as recommended by the battery manufacturer. Low electrolyte levels cause excessive gassing and twisting of plates.

  • Page 53: Avoiding Battery Trouble

    Power system maintenance 3–33 Table 3–4 Maximum allowable impurities in battery water TYPE OF IMPURITY PPM (mg/L) PERCENT Total solids 0.0500 Fixed solids 0.0350 Organic and volatile matter 0.0050 Chloride 0.0025 Iron 0.0004 Nitrates and nitrites 10/10 0.0010 Ammonia 0.0005 Manganese (NS 5553) 0.007 0.0000007...

  • Page 54: Standby Power System Checks

    3–34 Power system maintenance 3.9 Standby power system checks Maintenance of the DMS standby power system is crucial to the prevention of switch downtime resulting from commercial power interruptions. Keep detailed records to ensure that proper maintenance of the standby power system is being performed.

  • Page 55: Standby Engine-Alternator Checks

    Power system maintenance 3–35 3.10 Standby engine-alternator checks Perform the following checks on the standby engine-alternator. Record any problems found in the maintenance action record (Figure 3–14). Check the location of the operating instructions to verify that they are within view of the controls. Check the operating instructions to verify that they provide simple, step-by-step instructions for operating the engine.

  • Page 56: Standby Power System Exercise

    3–36 Power system maintenance 3.11 Standby power system exercise The standby power system exercise is a simulated failure of commercial ac power source to verify that all standby power equipment functions normally and continuity of service is maintained. The exercise is under control of local supervision and provides an opportunity for network maintenance and building personnel to: increase their familiarity with power plant capabilities and operation...

  • Page 57: Preparations

    Power system maintenance 3–37 3.11.2 Preparations Before starting this exercise, perform the following preparatory steps: 1 Perform the following precautionary checks. If any items are found to be unsatisfactory, do not proceed with this exercise until unsatisfactory items are corrected. a.

  • Page 58: Procedure

    3–38 Power system maintenance — Date — String # — Battery # 3 Verify the accuracy of dc voltmeters to be used in this procedure by comparison with a secondary standard meter. 4 Standby power system exercise evaluation report (Figure 3–9): —...
  • Page 59 Power system maintenance 3–39 8 If using a stationary standby engine-alternator, have someone at the engine prepared to measure the engine cranking time and start the engine if is is a manual start engine. Note: There should be no prior warm-up of the standby engines for this test. 9 Simulate an ac power failure by opening the commercial ac power circuit breaker.
  • Page 60 3–40 Power system maintenance 14 Determine the appropriate duration of the battery load test. Note: Depending on the discharge load on a power plant, the duration of a battery load test for the purpose of this exercise must not normally exceed normal time limits prescribed in Table 3–5 or the power plant low voltage limits.

  • Page 61: Miscellaneous Power Plant Checks

    Power system maintenance 3–41 23 At the standby engine, record the following in the appropriate engine-alternator log (Figure 3–11 or 3–12): — engine temperature — oil pressure — RPM 24 Return to commercial ac operation as follows: — For automatic start engine-alternators: –...

  • Page 62: Submitting The Maintenance Report

    3–42 Power system maintenance Check with operating company management to verify that power-trained craftspersons are available. Check the battery room to verify that battery room safety equipment is available. Refer to Section 3.5 Power plant safety for a list of battery room safety equipment..

  • Page 63: Grounding System Maintenance

    4–1 4 Grounding system maintenance Accurate diagrams and appropriate tools are essential to the maintenance of the grounding system. 4.1 Grounding system diagrams There should be an accurate schematic diagram of the grounding system, as well as floor plan diagrams showing the location of grounding system components at the DMS site.

  • Page 64: Building Principal Ground (Bpg) Checks

    4–2 Grounding system maintenance 4.3 Building principal ground (BPG) checks The BPG is the main point within a building at which the ground reference potential is established. The BPG is directly referenced to earth by such means as water pipes and/or electrodes driven into the earth. See Table 1–1 for terms used by various operating companies to designate the BPG and other grounding bars.

  • Page 65: Ground Resistance Test

    Grounding system maintenance 4–3 5 Use the non-metallic brush to remove any accumulation of dust from the BPG, the connections, and bar-mounting insulators (if used). Dust and dirt attract moisture, which can promote corrosion and can affect the insulating properties of the insulators. 6 Inspect each connection for signs of corrosion.

  • Page 66: Power Plant Grounding Checks

    4–4 Grounding system maintenance 5 Using a non-metallic brush, brush off any accumulations of dirt or dust from the bar and any mounting insulators, if used. Excessive accumulations of dirt and dust can promote corrosion and can affect the insulating properties of insulators. If any connections to the FGB are not on the grounding schematic, make a note that the grounding schematic must be updated.

  • Page 67: Other Dms Switch Versions

    Grounding system maintenance 4–5 If for any reason external ac power distribution circuits are brought into the switch IBN, they shall be referenced to the DMS SPG in accordance with the applicable requirements of NTP 297–1001–156. 4.7.2 Other DMS switch versions For DMS switch installations that do not feed all of their loads from internal inverters, external ac power suitable to the loads is required (and shall be supplied by the customer).

  • Page 68: Framework Bonding Equalizer (Fbe) Checks

    4–6 Grounding system maintenance Check your grounding schematic to determine the configuration of the DMS SPG in your building. If the DMS SPG is a bar separate from the FGB or BPG, perform the following checks: 1 Check the floor plan of the floor where the DMS SPG is located. Verify that the location of the SPG is correct on the floor plan.

  • Page 69: Framework Ground Bus Checks

    Grounding system maintenance 4–7 b. DMS lineup without a DPCC or PDC: the FBB of the cabinet or frame closest to the FGE in that lineup must be bonded to the FBE. c. Spare circuit card storage cabinet: IF the storage cabinet is more than 2 m (7 ft) away from any metallic object that is not referenced to the DMS SPG and the storage cabinet has no connections to a non-DMS cabinet, the storage cabinet must be referenced to the FBE.

  • Page 70: Logic Return Equalizer (Lre) Checks

    4–8 Grounding system maintenance If any other cable was bonded to the framework ground bus, write “ILLEGAL CONNECTION” on a blank label and attach it to the cable. Make a note that an illegal connection must be removed from the framework ground bus.

  • Page 71: Logic Return Bar (Lrb) Checks

    Grounding system maintenance 4–9 4.12 Logic return bar (LRB) checks In an ISG office, LRBs are used to bond the logic return of DMS cabinets and frames to the LRE. If this is an ISG office, make the following checks on the LRBs: 1 Verify that the location of an LRB is correct on the floor plan diagram.

  • Page 72: Main Distribution Frame/Protector Frame Checks

    4–10 Grounding system maintenance 3 Using the non-metallic brush, brush off any accumulations of dust on the bar and connectors. 4 Inspect each CEGB connection for signs of corrosion. If any connections are corroded, make a note that the corroded connections must be cleaned.

  • Page 73: Cleaning Corroded Grounding Connections

    Grounding system maintenance 4–11 4.16 Cleaning corroded grounding connections DANGER Risk of electrocution / risk of service outage Removing a grounding conductor from a ground bar can cause electrocution and a service power outage. If a cable connection must be removed, install an appropriately-sized jumper before the end of the cable to the ground bar BEFORE the connection is broken.

  • Page 74: Grounding Audit

    4–12 Grounding system maintenance 4.17 Grounding audit The grounding audit is a series of checks performed on the DMS grounding system for the purpose of detecting and correcting violations of DMS switch grounding practices. The grounding audit is performed on new installations and on existing installations when new equipment is added or when frequent grounding-related problems are experienced.
  • Page 76 DMS-100 Family Digital Switching Systems Power and Grounding Routine Maintenance Manual Product Documentation—Dept 3423 Northern Telecom P.O. Box 13010 RTP, NC 27709–3010 1–800–684–2273 (1–800–NTI–CARE) 1988, 1989, 1994, 1997 Northern Telecom All rights reserved NORTHERN TELECOM CONFIDENTIAL: information contained in this document is the property of Northern Telecom.

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