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PROCESS MANUALGIPL-OEM

Project and Operation & Maintenance

PROCEDURE

P1-GIPL-003

PROCEDURE FOR MAINTENANCE OF SWITCHED

MODE POWER SUPPLIES

PROCEDURE NO.: P1-GIPL-003

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1. Purpose

This document provides instructions for carrying out Periodic Maintenance of

Switched Mode Power Supply and its parts like Rectifiers, Alarm Control Module,

AC distribution unit & DC distribution unit and metal clad enclosure housing these

components. The AC & DC distribution unit mainly consists of components like

contactors, moulded Case Circuit Breakers (MCCB), Miniature Circuit Breakers

(MCB) & HRC fuses.

2. Scope

This procedure will outline the maintenance routines and responsibilities for the

Switched Mode Power Supplies (SMPS) in BTS sites. This procedure provides

general guidelines as applicable for different types of SMPS. The users of this

procedure are advised to refer the corresponding OEM (O&M) manual for

carrying out specific O&M activities.

3. Responsibilities

3.1 National Head

Based at Corporate office New Delhi is responsible for the technical integrity of

this procedure. The National Head or his nominated Deputy shall be authorised

for any changes with this procedure.

3.2 Circle Manager

The Circle Manager or In-charge is responsible for ensuring that all activities

related to this procedure are complied with and recorded as described in this

document.

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4.4 Maintenance Process

4.1 Background

The rectifiers in SMPS are in modular fashion. The rating of the rack depends on

the total number of rectifier modules. All the rectifier modules provide active load

current sharing.

The AC distribution unit consists of MCBs for protection, contactors for mains

supply to the power rack terminal and surge protection device to prevent damage

to rectifier modules due to surges & spikes present in AC mains.

The DC distribution unit consists of a number of miniature circuit breakers,

battery fuse, terminal blocks for loads & battery distribution and protection like

BLVD, LLVD. It also has the functions of detecting the signal of DC and AC power

distribution units, fault alarm, and communicating with host and monitoring

module.The alarm control module receives the operation information of AC & DC

distribution units and rectifiers and performs the corresponding controls.

When the battery voltage drops to the terminating voltage 42.5V, in order to

prevent battery over-discharge, the system activates the BLVD contactor to

disconnect and thoroughly protect the battery.

In normal conditions, the system operates in parallel float charge state, i.e. the

rectifiers and batteries operate in parallel. The rectifiers supply power to the

telecom equipments & security systems and float charge current to the battery.When an AC main fails, the rectifiers stop working, the battery to maintain normal

operation powers the equipment. When the AC main is recovered, the rectifiers

resume powering the equipment and charging the battery to compensate for the

consumed energy.

4.4.2 Maintenance Frequency and Records

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Format No. Frequency Location Period to be maintained

OEM/002 Yearly BTS 3 Years

OEM/0013 Fortnightly BTS 3 Months

Contact the vendor for any manufacturing defects or discrepancies found during

the maintenance.

4.4.3 Safety Precautions

The following safety precautions need to be followed for carrying out any work on

the SMPS:

4.4.3.1 Inspections SMPS in energised condition

Inform the concerned authority and start

The SMPS and the components therein are LIVE and in energised state. Do

NOT touch any components with bare hands as this may lead to

electrocution.

Maintain a safe distance while working near LIVE terminals.

When the rectifier is working, the temperature of the heat sink is very high.

When the working rectifier is extracted out, never directly touch the

radiator of the rectifier to avoid any scald.

Wear safety shoes while working.

Stand on dry and insulated objects like Rubber Matt during working.

Do not touch any live conductors/cables without verifying that they are

dead. Use only insulated tools while working on DC circuits.

4.4.3.2 Maintenance SMPS in de-energised condition

Ensure that all supplies to the panel are switched OFF and the respective

switch locked and red tags placed on them.

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In case the maintenance is to be done on part of the SMPS and where the

other part is LIVE then appropriate care should be taken to mark its LIVEportion.

Temporary stickers have to be placed to discourage working personnel

from operating at the LIVE parts.

To protect the system against the rise in potential of metal structures, keep

the earth connections continuously on the bus-bars.

Discharge the circuits using proper discharge wire. Care should be taken tofirst connect the discharge wire to ground bus and then connect it to the

circuit.

Use personal protective equipment like safety shoes and hand gloves while

working on SMPS.

Access to working space and escape passages shall be kept clear and

unobstructed.

Warning signs, if required shall be placed at appropriate places.

Follow all precautions while using hand held tools like blowers, drill

machines etc. Use hand held tools with ELCB boards only. Use only insulated tools while working on DC circuits.

4.4.4 Tools Required

Calibrated Digital Multimeter

Spanner set

Cloth, Cotton rags

Nylon Brush

Normal hand gloves

Megger 500 V

Discharge wire

First aid kit

Vacuum cleaner

4.4.5 Fortnightly Maintenance Tasks

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Ref the data sheet OEM/0013

4.4.6.1 Purpose of Inspection

The purpose of the fortnightly inspection is to assess the general condition of the

SMPS including the condition monitoring check of its various parameters. This

fortnightly inspection is intended to be a general quick check for the moreconspicuous problems that can be encountered. Proper maintenance of SMPS

ensures continuous power availability to loads. The following types of problems

can be detected during the fortnightly inspection:

Overheating of components like MCB, MCCB, Contactors, Relays.

Oxidation of connections at terminals.

Non-working or missing indicating lamps and meters.

Overheating or chaffing of cables inside the panel.

High amount of dust and dirt inside the SMPS. Unbalance or overloading of the circuits.

Improper voltages from the supply side.

Possible source of entry for vermin entry

4.4.6.2 Inspection Procedure

Refer the manufacturers manual for the maintenance guidelines and record the

observations. Intention of this inspection as described above is to find out thevisible abnormalities, which could lead to failures. Extreme care should be

exercised while opening the door and working near or close to LIVE parts.

NOTE: Whenever performing maintenance inspections ensure that the

manufacturers instruction manual for the SMPS is available for review.

The general steps for inspection are as outlined below:

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Follow all safety precautions as mentioned in section.4.4.3

Check whether all indicating lamps/alarm control module are in working

condition and are as per logic designed. Check normal display parameters

as per OEM.

Check all the three-phase or single-phase voltage(s) from the Monitoring

Module. In case of doubt check the voltage using a multimeter on the

incomer switch/MCB/MCCB. Do not try to rectify the switch or meter inLIVE state as this may lead to short circuit.

Check the three phase or single-phase current(s) from the Monitoring

Module. Do not disconnect the secondary connections of the CT as this may

lead to high voltage on the secondary side and damage the CT and as well

as create a hazard for the working personnel.

Check the load current and compare the same with the ratings of the

breaker, MCB, MCCB etc.

Check that the frequency of supply is within the range i.e. 50Hz 5%

Check that the output voltage and current of rectifier is normal. Thedifference between the system voltage displayed by the monitoring module

and that displayed by the rectifier should not exceed 0.2V. Check the

output current of each rectifier.

Check the normal condition of the surge protection device (SPD) and its

breaker. Check that the SPD is not discoloured, deformed or torn up.

Check the earthing bonding between surge arrestor ground and main

earthing bus.

Check the battery float voltage with the batteries in fully charged condition

(for VRLA battery, it should be 2.25 + 0.02 x 24 =54.2 to 54.4 V).

Check that the output current imbalance between rectifiers is less than 5%.

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Check the individual general parameters of the SMPS available from the

panel display. Use of Laptop to check all parameter is not necessary.

Check that there is no blockage in equipment radiation passage.

Check that the rectifiers fan and airway, dust net and cabinet ventilation

are not obstructed by objects and no dust is accumulated. If dust is

observed then clear the same using a vacuum cleaner or a blower or brush.

Observe for any leaks over the top of SMPS. If water leaks are observedthen cover the panel with plastic sheet as a temporary measure.

Subsequently attend the water leak.

Observe for any unwanted cable openings. This can be source for

rodent/reptile entry. Plug such opening with proper material. Temporary

measure can be adopted to cover the openings till permanent arrangement

is made.

Feel the SMPS with bare hands. As a general rule, during operation, any

temperature that the palm of the hand cannot stand for about 3 secondsmay indicate trouble. If found abnormally hot then switch off the

concerned circuit and observe for any abnormalities. In case the circuit

cannot be de-energised because of operational criticality then arrange for a

planned event at the earliest.

Wherever feasible observe the cable terminations and connections.

Observe for insulation chaffing, frayed sheath, improper glanding, wrong

sizes of glands and terminals. Take corrective actions if possible or else

arrange for planned event.

Check that the sockets are connected firmly. Check that the cables are

routed in order and firmly and that no cables are distorted due to the

pressure imposed by metallic parts.

Check the neutral conductor condition for any visible signs of over-heat.

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Check the individual component like MCB, MCCB, contactors, relays and

fuses for any abnormality like overheating, broken condition, discoloration,

unusual noises etc. Replace if it is possible without affecting the operations

else arrange a planed event for replacement.

Check the grounding connections for the SMPS. Check the continuity of

earthing point up-to earth pit physically. Repair if found loose, corroded or

broken.

4.4.7 Yearly Maintenance & Inspection

4.4.7.1 Purpose of Inspection

The purpose of yearly inspection is to assess the overall condition of the SMPS.

This is normally performed with the SMPS in OFF and DEAD condition. However,

the maintenance of SMPS in fully de-energised state would lead to outage of DC

power and thus outage of network. In order to avoid such a scenario, it is

proposed to carry this maintenance procedure with only AC input & rectifiers in

OFF condition. The load (telecom) will continue to be fed through the battery

bank and the respective load MCBs.

The normal course of maintenance of the SMPS shall be in PARTIALLY DE-

ENERGISED CONDITION only. In case of any critical/pending jobs that warrants

shutdown of the complete SMPS, then this job has to be done under PE window.

Generally it is recommended to conduct annual inspection during the first three

years of operation. Inspection and maintenance frequency can then be increased

or decreased depending upon the observations and experience.

The inspection followed by subsequent maintenance during the annual shutdown

(Partially & fully de-energised) is quite detailed. The following repair

work/maintenance jobs are taken up during the annual maintenance plan:

Replacement of all missing meters and indication lamps.

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Rectification of faults observed during the normal energised state

inspection

Cleaning of SMPS interiors

Meggering of bus ducts and bus-bars

Checking of trips and alarms.

4.4.7.2 Inspection/Maintenance Procedure

Refer Format No.: OEM/0002 for annual maintenance of SMPS in partially de-

energised and fully de-energised condition. The general parameters of the SMPS

shall be recorded in Format OEM/0003. The maintenance procedure for SMPS in

partially de-energised condition includes shifting the DC load onto the batteries.

Prolonged outage of SMPS panel may lead to site failure due to battery discharge

Hence the shutdown work should be completed in stipulated hours of battery

backup.

NOTE: Whenever performing maintenance inspections ensure that the

manufacturers instruction manual for the SMPS is available for review.

MAINTENANCE OF SMPS IN PARTIALLY DE-ENERGISED CONDITION

The following activities shall be carried out during the annual maintenance in

partially de-energised condition:

Identify the section that will be shut down for maintenance.

Identify the switches, MCCB, breakers that need to be isolated for de-

energizing the section of SMPS. Inform the NNOC about the work.

Follow all safety precautions as mentioned in section 4.4.3

Switch OFF the input MCB on the AC side. This will shift the load on to the

batteries. In case of two sources of power shut OFF both the power

sources. Ensure that the upstream MCB/SFU in the LT panel is also switched

OFF. Place a red tag on the LT panel to indicate that the circuit is de-

energised.

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Isolate the section planned for maintenance.

Ensure that the load is transferred to the battery backup.

Switch OFF individual rectifiers by switching OFF the corresponding MCBs.

Ensure that proper red tags are placed at appropriate places.

Open the SMPS door and check the enclosure door gasket for proper

placement & replace if damaged.

Check for AC loose connections. Loose connections or bad terminations will

cause heat buildup. If any signs of heat are noticed at any termination

point, that connection should be disconnected, inspected & replaced, if

necessary, before resuming operation.

Check that all the nuts & bolts are tightened properly, being careful not to

overstress the bolts.

Clean the air filter to provide filtered air. Do not install a wet filter in the

unit.

Observe the AC cable terminations and connections. Observe for cracked

insulation, frayed sheath, improper glanding, wrong sizes of glands and

terminals and take corrective actions if required.

Check the cables for evidence of overheating.

Check the SMPS earthing continuity.

Check the normal operation of the surge protection device. Check that it is

not damaged and replace if necessary. Check that there is no fault

indication displayed on surge protector.

Check the wiring between SMPS and the remote alarm management

system (either at DDF or SCADA system).

All the switches and breakers (AC input MCCB and rectifiers circuit breaker)should be in OFF position and the lightning protection circuit breaker is

closed before switching on the AC power.

Switch on the MCCB corresponding to the SMPS at the ACDB

Switch ON the AC input MCCB of the SMPS. At this time, the AC contactor

closes. Check that the AC operation indicator turns ON.

Switch on the rectifiers circuit breakers in front of the AC distribution

Module one by one.

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Measure the mains voltage.

Check the output voltage displayed on the monitoring module.

Using a digital voltmeter verify that the output voltage is in accordance

with the systems voltage.

Verify that all the rectifier modules are ON and without any fault alarms. If

any alarm is observed then it should be checked & rectified.

Ensure that the load is transferred to the normal power supply.

Note down the load currents. Check the parameters of the alarm simulation and check the alarms

accordingly.

Follow the OEM manual for the procedure of checking of alarms.

MAINTENANCE OF SMPS IN FULLLY DE-ENERGISED CONDITION

In addition to the above-mentioned procedures for SMPS maintenance in partially

de-energised condition, the following activities shall be carried out during fully-

de-energised maintenance: Switch OFF the input MCB on the AC side. In case of two sources of power

shut OFF both the power sources. Ensure that the upstream MCB/SFU in

the LT panel is also switched OFF. Place a red tag on the LT panel to indicate

that the circuit is de-energised.

Remove the HRC battery fuse ensuring the battery is not connected to the

system. Use an insulated fuse puller.

Ensure that the power has been properly locked out i.e. verify that no parts

of the power or control circuitry are energized by back feed from alternate

power or control sources and proper red tags are placed at appropriateplaces.

Check for AC & DC loose connections.

Inspect inside the enclosures for damage & corrosion of metallic objects.

Repair & paint as required.

Completely clean the SMPS interiors if dust is observed using vacuum

cleaner or blower. Be careful to use insulated tools.

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Check that the fuses of appropriate ratings are completely inserted in the

clips. Check clips for adequate spring pressure.

Test the conductivity of DC cables by using micro-ohm meter or determine

voltage drop under test load conditions.

Perform insulation resistance test on each phase-to-phase and phase-to-

ground using a Megger on buses, breakers and cables. Insulation resistance

would be low if there is any dust or moisture in the interiors of the panel.

Before connecting the battery, confirm with a multimeter that the polarityof the battery cables, DC bus and battery terminals match. When

connecting the battery, careful attention is required to prevent short circuit

of the positive and negative poles of the battery. If two batteries are

connected at the same time, attention should be paid to prevent battery

mutual charging due to unequal end voltages of the two batteries.

Insert the HRC battery fuse thus connecting the battery to the system.

All the switches and breakers (AC input MCCB and rectifiers circuit breaker)

should be in OFF position and the lightning protection circuit breaker is

closed before switching on the AC power. Switch on the MCCB corresponding to the SMPS at the ACDB

Switch ON the AC input MCCB of the SMPS. At this time, the AC contactor

closes. Check that the AC operation indicator turns ON.

Switch on the rectifiers circuit breakers in front of the AC distribution

Module one by one.

Measure the mains voltage

Check the output voltage displayed on the monitoring module.

Using a digital voltmeter verify that the output voltage is in accordance

with the systems voltage.

Check and record the battery charging current.

Verify that all the rectifier modules are ON and without any fault alarms.

Check that all the rectifiers communicate properly with the alarm module

by observing the LED indications. If any alarm is observed then it should be

checked & rectified.

Check that the rectifier cooling fans are working properly.

Turn ON the load MCBs to put the load on the system

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Ensure that the load is transferred to the normal power supply.

Note down the load currents.

4.4.8 Alarm Simulation

The alarm module in the SMPS facilitates Potential Free Contacts (PFC) for remote

monitoring of alarms. All alarms are potential free and may be connected to

external displays/equipment as closed or open circuit when alarm is reported.Simulation can be done by shorting these terminals at the output relays or by

actual operation of relays through keypads. The output alarms of SMPS in case of

Avansys make are grouped and these can also be checked either through keypad

or shorting the terminals. Various alarms are configured to functional relays in

such a way that a single relay operates when one or more alarms configured to it

appear. These alarms are then extended to the OMCR.

The entire SMPS related alarms and electrical parameters need to be verified

after conjunction with OMCR. General alarms available in the SMPS are:

1. Battery On Line (BOL)

2. Fuse failure

3. Rectifier failure

4. Battery Low Voltage Disconnect (BLVD)

5. High and Low DC voltage

6. AC mains failure

For details of various alarms available for each model, please refer the OEM

manual.

7.Simulation of Alarms

1. By switching OFF the AC mains check that the BOL alarm (or/and AC mains

failure alarm) appears. Switch ON the AC mains and check that the alarm is

cleared.

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1. Either by shorting the terminals on DDF or SCADA or by operating the relay

through keypads check that the Fuse Failure alarm appears and the same is

cleared when resetted.

2. Pull out the redundant rectifier module and check that the Rectifier Failure

alarm appears. Refit the rectifier module back in its place and check that

the alarm clears.

3. Check the BLVD alarm only by shorting the terminals of the relay and NOT

through actuation.While carrying out the above alarm simulation, check that the alarms are

extended to the OMCR when they appear and the same are cleared when the

relays are resetted.

4.5 Formats, Records & Frequency

Format No. Frequency Location

Period to be

maintainedOEM/002 Yearly BTS 3 Years

OEM/0013 Fortnightly BTS 3 Months

Documents

P1-GIPL-003