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BN-SP-ES07 Inspection Procedure for Metal-Enclosed Low Voltage Draw-OutSwitchgearTable of Contents
Summary1.
General2.
Incoming Feeder and Tie Breakers3.
Bus Bar from Main Switch to Horizontal Bus Bars4.
Horizontal Copper5.
Bus Bar System Vertical Sections6.
Outgoing Units7.
Earthing8.
High Potential Test9.
Insulation Measuring10.
Meters and Protective Relays11.
1. Summary
Before the low voltage switchgear is ready for shipment the vendor shall make suitable tests to establish to the satisfaction of
owners representative that all equipment, devices, protection relays and wiring have been correctly installed and are in
satisfactory working condition and operable as requested.
All tests shall be made in accordance with the nationally recognized standards stated in the requisition.
The entire installation shall be constructed so as to provide maximum safety. Even if more provisions than required by law will
be necessary, it will be vendors responsibility to include these provisions.
Prior to testing, switchgear shall be dust-free and thoroughly cleaned of all waste material.
The switchgear vendor shall take care that all necessary test equipment will be available in the factory or at field.
2. General
The switchgear shall comply with the following requirements:
Is the switchgear of the draw-out or the
nondraw-out type:
draw-out/nondraw-out
Is the incoming feeder a cable connection or a
busduct connection
cable/busduct connection
Is the switchgear for indoor or outdoor use: indoor/outdoor use
Short-circuit current of the installation: KA rms
KA peak
Time short-circuit current of the installation: s.
Maximum nominal current:
1. copper connection incoming feeder A
2. main breaker(s) A
3. horizontal busbar system A
4. tie breaker A
Nominal voltage: V
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Frequency: Hz
Language to be used on the name-plates for
operating instructions and outgoing circuits:
Language to be used for maintenance
instructions:
What is the color of the outer side of the
switchboard:
Dimensions of the installation: length mm width mm height mm
What are Companys numbers of the drawings
according to which the switchgear will beinspected:
1.
2.
3.
4.
5.
Who will take care of the erection at site:
Is the busduct connection between the
transformer and the switchgear finished
and by whom will this connection be installed:
1. busduct connection is not included in the supply.
2. busduct connection
3. installation of the busduct connection by supplier/Company.
4. no busduct connection
The frame which shall be cast-in or connected
to the concrete floor of the substation and will
be supplied by:
1. supplier of switchgear
2. Company
In case the frame will be supplied by the
vendor, have the frames already been shipped:
yes/no
The required height and width of the substation
door(s) are (inclusive of 4 rolls):
height mm
width mm
Take care that everything will be new andunused.
Is a crane necessary for hoisting the
switchgear into the substation:
If yes, contact the Field Engineer for provisions
to hoist the switchgear into the substation.
yes/no
The use of plastic partitions for screening is not
permitted.
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Screening shall be by Pertinax sheets or
equivalent material.
Equivalent material may only be used after
approval by purchaser.
Pay attention to the wiring, relays, terminals
etc.; they must be coded in accordance with
the drawings.
The wiring shall be coded so that after
disconnecting it can be reinstalled without
checking at the right terminals.
What are the colors of the wiring: 1.
What are the colors of the wiring: 2.
3. Incoming Feeder(s) and Tie Breaker
There must be sufficient space for connectionof incoming feeders (check one line for
number).
Check whether the neutral is mounted on the
right side, viewed from the front.
Check the diameters of the holes for the
connection bolts of the busbar with regard to
the width of the busbar. Holes must be too big
(DIN 43673).
flat copper bar, width mm
fastening holes, diameter mm
It must be impossible to touch the incoming
copper when the door is open (pay attention to
the Pertinax sheets).
Check whether the nominal current of the
breaker is sufficient with regard to the
transformer or switchgear rating.
current of breaker A
current of power transformer A
KVA
Incoming feeder and tie breaker shall be
suitable for the dynamic short - circuit
KA peak
current of the transformer and thermal short
current of
KA rms
s.
Check whether the outgoing or incoming
copper is directly mounted above the arcingchutes.
(This is not permitted. The ionized air must be
able to rise freely and may not introduce a
short circuit).
Make sure that there are no obstacles which
can hamper the gas flow on the upper and front
side.
A
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When protective relays are installed on the
breaker, check the current and time settings.
s.
When an inverse current/time relay is used, ask
for relay curve.
inverse
current
setting
time
definite
current
setting
time
Type, number and brand of relay(s):
It shall be possible to operate the main breaker
with the compartment door closed (manually
and electrically)
yes/no
Check whether arcing chutes are undamaged
and uncracked. Try to remove the arcing
chutes from the breakers.
This must be possible without touching any
obstacles.
Wires going from the main busbars to fuses (forexample for closing the main breaker) may not
touch other wiring or steel constructions and
must be short as possible.
Check especially the bolt connections of the
copper bars to the main breaker, even if
something shall be removed. Check the
number of bolts and the bolt diameters with
regard to the mounting busbar. Check also the
tensile strength of bolts.
Check the distance of the busbars with regard
to each other and with regard to earth (neutral).
The distance shall be at least 2 cm.
Check whether there is a link in the neutral of
the incoming feeders.
The presence of a link shall be clearly indicated
with a nameplate.
Check especially that the air circulation along
the breaker is not obstructed. This is for cooling
of the breaker. (Wrong positioning of the
Pertinax plates.)
How is the incoming breaker controlled: automatically/manually
Is the transfer from one feeder to another
automatic or manual:
1. manual
2. automatic
3. no automatic
4. one feeder
Are both feeders in parallel while transferring: 1. manual transfer yes/no
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2. automatic transfer: yes/no
What is the position of the tie breaker in normal
operation:
1. open
2. closed
3. no tie breaker
Are feeder breakers and tie breaker of the draw
-out type:
Check especially the draw-out contacts when
the breakers are of the draw-out type.
yes/no
Are feeder breakers and tie breaker
interchangeable:
yes/no
Can one feeder handle the total load: % continuous
% h
Are protective relays installed on the tie
breaker:
yes/no
Is the coupler a breaker, link or a load switch: breaker/link/load switch
When a link is installed, an ampere meter shall
be installed:
Ampere meter: yes/no
Close the feeder breaker and try to withdraw
the switch in the closed position.
Also try in the opposite sequence.
Take the feeder breaker out of the switchgear,
close the breaker and try to insert the breaker.
Before the main contacts touch each other the
breaker will be switched off.
Even when it is not possible to insert thebreaker in the closed position, this will be an
acceptable construction.
When the feeder breaker is inserted, but is in
the off-position with charged springs for fast
closing, the breaker must be able to unload
automatically, or further movement of breaker
must be prevented.
4. Busbars from Main Switch to Horizontal Busbars
Vertical busbars from main switch to horizontal
busbars must have the same cross-section as
the copper of the incoming feeders. Is this so?
yes/no
It shall be impossible to touch this copper, even
with an open door (screening with Pertinax
plates).
If there are lids instead of doors, screening of
the busbar is not necessary. The lids must be
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fastened with captive screws. Fastening the
lids with toggles is not permitted.
Check the voltage distances with regard to
each other and with regard to earth. Take into
account where these distance are found.
Take care of the bolt connections in the busbar.
Check the bolt connections with a torquewrench.
This is applicable to the entire busbar system.
Check whether all bolts are easily accessible.
If current transformers are applied, take care of
the current direction (current goes always from
K to L).
Check the following characteristics of the
current transformers:
1. ratio:
2. class:
3. output: VA
4. excess current: N =
5. suitably for short-circuit current or during a
time of:
KA peak
KA rms
1 s.
The wiring connected to the secondary side of
the current transformer inclusive of earthing
shall be at least 4 mm2.
The busbar shall be marked with painted dots
in the color specified in the requisition. This
shall be done at different places in the
switchgear.
Check whether there is a partition plate
between the vertical copper and the horizontal
copper. If there is no partition plate, check
whether the horizontal copper has partition
plates on both sides of the incoming feeder
panel.
If parallel buses are used, check whether there
are copper pieces and check how they are
fastened; bolts screwed in the copper of the
busbar are not acceptable.
Spring washers shall be placed under the nuts
of the fastening bolts of the buses.
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5. Horizontal Copper
The horizontal copper must have the same
cross-section through the entire switchboard.
What is the cross-section of the horizontal
copper with regard to the incoming feeder
panel?
Check also the cross-section of the neutral.
Is the horizontal busbar compartment
separated from the vertical compartments?
(Partition plates between horizontal copper and
outgoing vertical copper)
Check especially the distance of the busbars
with regard to earth where the angle iron of the
vertical sections have been mounted.
Insulation tape or Pertinax to improve the
situation at certain spots is not acceptable. Thisis applicable to the entire switchgear.
Check especially the bolt connections. The bolt
has to come just through the nuts. This applies
to the entire busbar system. Check whether all
bolts are easily accessible.
Check whether the supporting of the busbars is
sufficient. A strip of insulation material mounted
on the top of the insulators to improve the
maximum allowed force in acceptable.
The busbars at the ends of the switchgear shall
be finished in such a way that an extension ofthe switchgear is possible without any further
mechanical handling.
Check the bolt connections of the horizontal
copper with the downgoing vertical copper.
Take care of possible torques. This occurs on
those places where an angle is in the copper
and no support is placed in the angle, because
torques reduce the short-circuit capacity. This
applies to the entire busbar system.
All high-tensile strength steel bolts, nuts andrings shall be corrosion-proof.
Check the interconnections of the horizontal
busbars. With how may bolts are they
connected? What are the sizes of the bolts?
What are the dimensions of the copper
overlapping?
Threading in the main rail system is not
acceptable.
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Top of insulators may not be used for
interconnections of the busbar system.
The insulators on the supporting iron shall be
installed so that also the outer rim of the
insulator bottom is supported and the insulator
is supported completely on its bottom surface.
When insulators are fastened with a bolt, it isnot permitted that the insulator is turned to be
fastened, but the bolt shall be screwed into the
insulator. Pay attention to welded tap ends;
these are places where such things happen.
The insulators shall be free of paint, dust and
damage.
When partitions are used to support the
busbar, check whether the copper is firmly
enclosed by the supports and check whether
the partitions are fabricated of nonhygroscopic
material.
Check whether the bolts of the steel top cover
do not come too close to the busbars.
6. Busbar System Vertical Sections
Check the dimensions of the vertical copper
and the supporting of the vertical copper:
dimensions copper
x mm
distance between two insulators in the length and width
It shall be impossible to touch the vertical
copper (even not from an adjacent panel orwhen the units are drawn-out).
Check especially the lower part of the copper.
This must be protected so that ionized air
cannot flow into adjacent panels.
Check the connections between the vertical
copper and the various units.
Check especially the distances, supports and
bolt connections.
If there is a copper connections between
vertical copper and a unit, it must be screened
with an insulating material, which is fireproof
(no tape or similar).
When working in an outgoing panel, it must be
absolutely impossible to touch any live parts,
even not the live parts of an adjacent unit.
It shall always be possible to insert the
outgoing cables without touching the busbar
system.
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Installation of the cables will be done energized
busbar system.
The maximum fuse rating of the back-up fuse
may not be more than 200 A.
It is allowed to provide the units behind that
back-up fuse with fuse holders and fuses of the
screw type.
Check whether the vertical sections are totally
enclosed:
Check also the bottom.
totally enclosed: yes/no
Check whether soft packing rims are used
between the vertical sections to avoid
openings.
7. Outgoing Units
A short circuit in a unit may never cause acomplete busbar short circuit. This shall be
checked carefully. The most dangerous place
is the connection between unit and busbar
system.
Before the main and auxiliary contacts touch
each other, there must be a good earth
connection between unit and enclosure, so that
there can never be a voltage difference
between unit and earth, not even under the
most unfavorable circumstances. Earthing of
the unit must be checked carefully.
Check especially the draw-out contacts andconnections to the circuit part. Wrong insertion
may never cause a short circuit or a damage to
the contacts and/or pins.
If electrical components are mounted on the
doors, a flexible connection between door and
fixed part shall be installed.
All units of the same type shall be
interchangeable. Some units shall be drawn out
to check the wiring at the units.
Unit compartment shall be totally enclosed and
preferably be made of metal.
The connection of the primary side of the fuses
and the contacts at the back of the draw-out
unit shall be at least 25 mm and shall run free
of other wiring and steelwork.
Partitions of insulating material shall be placed
between the fuses, sticking out above the
fuses. This is also applicable to the draw-out
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units to prevent a short circuit at the primary
side of the fuses. Partitions must continue at
the upper side.
The air distances between the live parts at the
primary side of the fuses shall be made as long
as possible. A short circuit at the primary side
of the fuses means a short circuit at the main
busbar system (full-circuit capacity).
Check the fuse holder rating with the fuse
concerned. This shall be an internationally
standardized fuse holder and fuse of the knife-
type.
Check type of fuse (gL preferred):
am/gL
In connection with the short-circuit capacity of
the transformer pay attention to the highest
permissible short circuit of the fuse.
Screw-type fuses may only be used behind
back-up fuses of maximum 200 A.
For screw fuses only the E27 type is
acceptable.
The location of the components in the unit shall
be so that ionized air around a contactor or a
short circuit within the unit can never cause a
short circuit at the primary side of the fuse. The
fuse must always interrupt the short circuit of
flash-over.
This is very important!
Try to make a short circuit with the fuse
remover.
Check the relation between the fuse rating and
the thermal relay rating. This is to prevent
damage of the thermal relays in case of short
circuiting. This should only be done
according to leaflets of thermal relay
manufacturer and not according to any
Company or vendors drawing!
Check the adjusting devices of the thermal
relays.
Check whether the rating of the smallestcontactor is 20 A. It is not allowed to use relays
or auxiliary relay in the primary wiring of the
motor circuit.
The connections in the unit shall be made with
flexible wires. Cable lugs shall be of the crimpit
type. Soldering connections are not acceptable.
Wiring for protection and transfer circuits shall
be numbered at both sides. Wiring, mounted in
the units, must be numbered at the terminal
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blocks so that it is not required to measure the
wiring before reconnecting the wires to the
terminals.
Control fuses may be of the E27 type, if placed
behind main fuses. If MCBs are used, check
characteristic (L).
It shall always be possible to check the current
of the unit with a hook-on ampere meter in
order to adjust the thermal relay. The wiring
must allow space for that.
A number of units of different types shall be
checked on their proper electrical working. If
any defects are found all units shall be
checked.
It shall be possible to reset the thermal relay
from the outside of the unit.
The lamp holder shall be made of copper to
prevent sticking of the lamp at high
temperature.
The terminals shall be of a good quality and
preferably be made of thermosetting material
and not of porcelain.
Check the quality of the short-circuit connection
at the terminals. This in connection with short-
circuiting of the current transformers.
The outgoing cables of the various units shall
be supported. The supporting saddles shall be
supplied by the manufacturer of the switchgear.
Check whether fuse ratings, contactor rating,
thermal relays, etc. comply with the drawings.
Dont forget the spare units. These shall be
installed completely as marked on the
drawings. Check also the space units.
It shall not be necessary to switch off the
switchgear while equipping the space unit.
Terminals carrying different voltages shall be
separated by means of partitions, which totally
stick out of the terminal.
Take a draw-out unit of the fuse-switch type
from the switchgear and try to draw-in the unit
in the switchgear again with the switch in the
on position.
Also try in the other way around. The unit is
installed in the switchgear. Switch on and try
to take it out of the switchgear.
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8. Earthing
There shall be an earth bar over the entire
length of the switchgear. It shall have a
dimension of at least 25 x 5 mm.
The copper shall be as long as possible to
minimize the number of connections.
The earth bar shall be mounted directly to the
steel structure and so that each vertical part
has at least one connection with the main earth
bar.
At the end of the horizontal earth bar two holes
shall be drilled for connection to the external
earth system ( 13 mm).
If there are terminals below the outgoing
groups, the main earth bar shall have earth
screws: for each cable at least one.
The connection shall be so that it is possible toearth the lead sheath as well as the earth
conductor of the cable.
When the cables are connected directly to the
units, there will also be an earth bar mounted
along the units.
It is not acceptable that the cables are stripped
all over the height of the installation for earthing
the cable at the bottom at the main earth bar.
The main breakers shall have a direct copper
connection with the main earth bar.
When the switchgear has a bus duct, there will
also be an earth bar inside the bus duct.
All parts of the bus duct will be connected to
the earth bar. There will also be an earth bar
between switchgear and bus duct.
The secondary side of the current transformers
shall also be earthed. Looping of an earth wire
is not acceptable. The connection will be at
least 4 mm.
9. High Potential Test
Check whether the installation is ready to be
put into operation; so all units, fuses, switches,
etc. shall be present and the switches shall be
in the off position.
High potential tests shall be 2500 V for 1
minute and applied between:
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phase to phase1.
phase to neutral2.
phase and neutral to earth3.
If certain components such as coils of
contactors, motors of breakers, current
transformers, voltage transformers, etc. lookstrange the components shall be tested in the
following way:
coils
small motors of breakers
current transformers
small transformers
The control fuses of the meters and relays shall
be removed.
The high voltage test set shall have a minimum
capacity of 3 KVA.
1000 V 1 minute
1000 V 1 minute
3000 V 1 minute
1500 V 1 minute
10. Insulation Measuring
Insulation resistance will be measured after the
high potential test. The resistance will be
measured:
phase to phase1.
phase to neutral2.
phase and neutral to earth3.
If possible, test the meter with a calibration
resistance.
The resistance shall be at least 10 M if the
installation is in dry condition.
If the humidity is very high the switchgear must
be dried before measuring.
Make a connection between one phase and
earth and check whether the megger is
indicating zero.
This is to be sure that the entire switchgear is
tested.
The insulation shall be measured with a 500 V
megger (or higher).
11. Meters and Protective Relays
The working of directional relays shall be
checked very carefully.
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The final test shall be performed in the field.
Check whether the wiring complies with
vendors data: directional relays testing yes/no
The same is applicable to the Kwh KWh meters tested: yes/no
meters and the power factor meters: power factor meters tested: yes/no
These are directional instruments and the
correct working depends upon the
KWA meters tested: yes/no
right polarity of the connections. KW meters tested: yes/no
Check whether the voltage on the meters and
relays is correct. The same is applicable to the
current. It may be possible that the current coils
need be switched in parallel or in series.
This is indicated on the relays.
Are the relays of the draw-out or nondraw-out
type.
draw-out/non draw-out
In how many phases are the directional relays
placed:
phases
How are the Kwh meters connected: phases
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