EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
SUBSTATION COMMISSIONING
COURSE
MODULE FIVE
COMMISSIONING
SWITCHES
Written by:
Raymond Lee, Technical trainer
Copyright ©2011
Electrical Industry Training Centre of Alberta
4234 – 93 Street
Edmonton, Alberta, Canada
Phone: (780) 462-5729
Fax: (780) 437-0248
Page 1 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
TABLE OF CONTENT
Headings
Page
Page 2 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Introduction
This module will introduce the NETA acceptance testing procedures for switches
comprising of mechanical and visual inspections, electrical tests and test data
analysis.
An understanding on the theory of operations, functions, types, industry ratings
and typical applications will be useful when performing acceptance testing. The
discussion will focus on the medium voltage, three-phase indoor and outdoor air
break switches, rated at 60 Hz found in substations. Oil, vacuum, SF6 and
distribution class switches and switches provisioned with series interrupters will be
developed as a sub set to this module in the future.
By the end of this module the participants should be able to differentiate the
difference between isolating, load breaking and load making switches of the fused
or un-fused types. General testing procedures for the blade type air break switches
will be presented. Where more detailed instructions are required, the reader should
consult the manufacturer’s manuals.
By the end of this module the participants will have the basic skills to perform
acceptance testing on blade type air break switches, conduct visual and mechanical
inspections, insulation resistance tests, dielectric withstand test, contact resistance
test and completing the inspection / test forms and conduct an assessment of the
test data.
Page 3 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
1. North American HV Switch Standards
The principle North American AC high voltage switch standards in use today are
the US standards comprising of the ANSI/IEEE, and NEMA standards.
There are no existing Canadian CSA standards for HV switches dealing with rating
or application guidelines / specifications. The applicable CSA standards are safety
practices dealing with HV equipment installation covered by the Canadian
Electrical Code.
The principle ANSI/IEEE standards are:
• IEEE C37.30
Standard Requirements for High Voltage Switches
• ANSI C37.32
High Voltage Switches, Bus Support and Accessories
• IEEE C37.34
Standard Test Code for High Voltage Air Switches
• NEMA SG 6
Power Switching Equipment
The basis for preferred ratings for indoor and outdoor air switches is covered in
IEEE C37.30-1997; Standard Requirements for High Voltage Switches.
Refer to Table 1:
Page 4 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 1: North American High Voltage Switch Standards
SPONSOR
TITLE
STANDARD
REV
C37.30
1997
C37.32
2002
ANSI /
IEEE
ANSI
C37.34
1994
IEEE
C37.58
2003
ANSI
SG-6
2009
NEMA
WORKING
GROUP
IEEE
Standard Requirements for High Voltage Switches
Standard for High Voltage Switches, Bus Support, and
Accessories
Standard Test Code for High Voltage Air Switches
IEEE /
NEMA
IEEE
Conformance Test Procedure for Indoor AC Medium-Voltage
Switches for Use in Metal-Enclosed Switchgear
NEMA
Power Switching Equipment
NEMA
Page 5 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
1.1 Rated Characteristics
Switch ratings are the designated limits of rated operating characteristics of the
device for operating at the rated power frequency.
Common designated ratings:
• Maximum voltage
• Dielectric withstand
• Power frequency
• Continuous current
• Peak-withstand and short time withstand current
• Making current
• Closing time
• Ice breaking ability
• Mechanical operations
• Mechanical terminal load
• Load-interrupting current
• Unloaded transformer interrupting current
• Expected switching endurance
Maximum Voltage
The rated maximum voltage is the highest rms line-to-line voltage at which the
switch is designed to operate.
Refer to table 2, 3 and 4.
Switches are selected on the basis of the rated maximum voltage and the lightning
impulse withstand voltage. The open gap withstand voltage value is at least 110%
of the phase-to-ground voltage value to ensure that overvoltage condition will
flashover to ground instead of flashing across an open switch gap distance.
Switches constructed with insulators having a rated phase to ground voltage
insulation level higher than the open gap withstand voltage level should be fitted
with surge arresters adjacent to the equipment to prevent open gap flashovers.
Dielectric Withstand Voltage
The rated dielectric withstand voltage is the voltage that the switch shall withstand
when the voltage is applied under the following specified conditions:
•
Rated Lightning-impulse withstand voltage 1.2 x 50 μs positive and
Page 6 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
negative withstand voltage
•
Rated power frequency dry withstand voltage
•
Rated power frequency wet withstand voltage
•
Rated Power frequency dew withstand voltage (enclosed switches
only)
The selection of the insulation level is a function of the device surge protection.
Table 2: Preferred Voltage Rating for Station Class Outdoor Air
Switches
Rated Maximum
Lightning
Rated withstand voltage
voltage
impulse
Dry
Wet
kV rms
kV peak
1 minute
10 second
8.3
95
38
30
15.5
110
50
45
27
150
70
60
38
200
95
80
48.3
250
120
100
Table 3: Preferred Voltage Rating for Distribution Class Outdoor Air
Switches
Rated Maximum
Lightning
Rated withstand voltage
voltage
impulse
Dry
Wet
kV rms
kV peak
1 minute
10 second
8.3
75
28
24
15.5
95
38
30
27
125
60
50
38
150
70
60
Page 7 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 4: Preferred Voltage Rating for Indoor Air Switches
Rated Maximum
Lightning
Rated withstand voltage
voltage
impulse
Dry
Dew
kV rms
kV peak
1 minute
10 second
4.8
60
19
15
8.3
75
28
24
15.5
95
38
26
15.5
110
50
30
27
125
50
40
38
150
80
As per manufac.
Power Frequency
The rated power frequency is the fundamental steady-state supply frequency of the
circuit for which it will be used.
Continuous Current
The rated continuous current is the maximum rms current in amperes at rated
frequency that can be carried continuously without exceeding the temperature rise
limits for any parts at a rated ambient temperature.
Refer to table 6, 7 and 8.
Note: Grounding air switches have no continuous current ratings but have
withstand current ratings which may be equal to or less than the disconnect
switch rating. Grounding air switches possesses a voltage rating and a
required minimum gap distance. Refer to table 5
Note: Gap distances information for other types of switches have been excluded
from this module.
Page 8 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 5: Grounding Switch Electrical
Clearances and Voltage Ratings
Rated Maximum
Minimum Gap – ground
Voltage
switch to live parts
kV rms
mm
inches
Indoor
4.8
51
2
8.3
51
2
15.5
51
2
27
75
3
38
102
4
Station Class Outdoor
8.3
51
2
15.5
51
2
27
102
4
38
152
6
48.3
241
9.5
Peak-Withstand Current
The rated peak-withstand current rating is the maximum instantaneous current at
the first major peak with a duration not less than 167 milliseconds that the switch
shall be required to carry while closed. The dc component of this current shall
have a decay time constant not greater that 45ms for a system X/R ratio of 17.
Note: Refer to module 4 for an explanation of %DC rating of circuit breakers
which shows the decay curve for power system with X/R ratio of 17.
The rated peak-withstand current rating is the ability of the switch to withstand the
magnetic forces generated by the short-time current without being forced open
while in the closed position.
Short-time Withstand Current
The rated short-time withstand current rating is the maximum rms current in
symmetrical amperes that the switch shall be required to carry for the rated shorttime duration while closed.
The rated short-time withstand current rating is the ability of the switch to
Page 9 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
withstand the heat generated by the short-time current.
The ratio of peak-withstand current to the short-time current is 2.6 at 60 Hz.
Short-time Withstand Current Duration
The rated short-time withstand current duration is the time in seconds that switch
shall be required to carry the short-time current while closed. Refer to table 6.
Table 6: Preferred Continuous and Withstand Currents for Station
Class Outdoor Air Switches
Continuous Current
Short-time current
Peak current 1
Amperes
kA
kA
600
25
63
1200
38
95
1600
44
110
2000
44
110
2000
63
158
3000
63
158
3000
75
188
4000
75
188
1. Peak withstand current (kA) 2.625 times the rms asymmetrical momentary current (kA).
Table 7: Preferred Continuous and Withstand Currents for Distribution
Class Outdoor Air Switches
Continuous Current
Short-time current
Peak current
Amperes
kA
kA
200 or 600
12.5
32.5
600 or 1200
25
65
1200
38
99
Page 10 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 8: Preferred Continuous and Indoor Air Switches
Continuous Current
Short-time current
Peak current
Amperes
kA
kA
200 or 400
12.5
32.5
600
25
65
1200
38
99
2000
50
130
3000
63
164
4000
75
195
Load making Current
The rated load making current is the highest rms current that the switch shall be
required to make and carry at the maximum rated voltage.
Load interrupting Current
The rated load interrupting current of a load-break switch is the highest rms
current, in amperes, between unity and .7 power factor that a device shall be
required to interrupt without requiring maintenance at its rated maximum voltage
for a number of operations equal to its expected switching endurance for this duty.
Note: High voltage disconnecting switches, grounding switches and horn-gap
switches are given no interrupting rating. Low levels of current may be
interrupted as per standard guidelines (IEEE C37.36b). Interrupter switches
fitted with interrupting chambers (e.g. Vacuum, Oil, SF6) may have various
types of interrupting ratings dependent upon application duty.
Fault making Current
The rated fault making current is the maximum symmetrical rms current that the
switch shall be required to make and carry.
Closing Time
The rated closing time is the specified interval between the energization of the
close coil and the making of the current-making switch contacts with an operating
condition at the lower limit of the rated control voltage range.
Page 11 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Ice-Breaking Ability
The rated ice breaking ability is the maximum thickness of ice deposited that will
not interfere with its opening and closing function.
Mechanical Operations
The rated mechanical operations is the minimum number of operating cycles that
can be perform without requiring readjustment or parts replacement. The specified
number of operating cycles is relative to the terminal loading.
Page 12 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
2. Nameplate Data
The general nameplate data show the minimum requirement for equipment
information.
Air switches nameplate data shall include the following where applicable:
• Manufacturer’s name and address
• Manufacturer’s type, designation number and serial number
• Month and year of manufacture
• Rated power frequency
• Rated maximum voltage
• Rated continuous current
• Rated short time (symmetrical) withstand current magnitudes and duration
• Rated peak-withstand current
• Rated lightning impulse withstand voltage (BIL)
• Allowable continuous current
• Rated making current
• Rated closing time
• Rated no load mechanical operations
Information specific to the device functionality such as interrupter switches or fault
initiating switches will include rated switching values:
• Rated capacitance-switching overvoltage ratio
• Rated maximum differential-capacitance voltage
• Rated load-interrupting current and expected switching endurance
• Rated unloaded transformer interrupting current and expected switching
endurance
• Rated parallel-connected capacitance-switching current and expected
switching endurance
• Expected switching endurance at rated making current
Rated load-interrupting current
Rated unloaded transformer interrupting
Rated parallel-connected capacitance-switching current
Rated single capacitance interrupting current
Page 13 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
3. Switch
A switch is a mechanical device that makes and breaks the flow of electrical power
and is used to change connections in a circuit or isolate a circuit from its power
source.
A switch consists of one or more contacts per phase mounted on an insulating
structure and arranged so that they can be moved into and out of contact with each
other by a suitable insulated operating mechanism.
General purpose switches are used to perform the following functions:
• Carry normal current continuously
• Switching of mainly active loads
• Switching of distributive line in a closed loop circuit
• Switching of no-load transformers
• Switching of charging current for unloaded cables or overhead lines
• Carrying short circuit currents for a specified duration
• Making short circuit currents
Special purpose (interrupter) switches can have designed applications for:
• Switching single capacitor banks
• Switching back-to-back capacitor banks
• Switching closed loop circuit having large power transformers in parallel
• Switching motors under steady state and stalled conditions
• Switching into a fault condition
Closing into a fault
Switches are not designed to interrupt fault current. This is a major functional /
design difference between a switch and a circuit breaker.
Switches can be operated to close following a breaking operation but cannot be
operated to open following a closing operation since the rated breaking current of
the switch may be exceeded.
Page 14 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
3.1 Switch Types
Switches can be broadly classified into:
•
Disconnect switch
•
Load break switch
•
Interrupter switch
•
Ground switch
•
Fault initiating switch
3.1.1 Disconnect Switch
Disconnect switches are designed for no load switching and opening of circuits
where negligible currents are interrupted. Disconnect switches are slow-speed
operating devices and not designed for arc interruption. Interlocking hardware /
controls are commonly installed to prevent opening under loaded conditions.
Disconnect switches can be fitted with arc whips to increase its load breaking
capability for transformer magnetizing currents and line charging current
Figure 1: Southern States Outdoor Disconnect Fitted With Arc Whip
Disconnect switches are designed to carry rated load currents and can momentarily
carry short circuit currents until the associated protective devices have operated
and trips the associated circuit breaker(s).
An open disconnect switch provides a visible confirmation that the circuit have
been opened and serves as an approved isolation point. When all the sources of
Page 15 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
primary energy have been remove and all required switches have been opened and
equipment de-energized and isolated, working safety grounds can be applied to the
de-energized equipment.
Motor Operator
Motor operated disconnect switches are fitted with a geared motorized operator
which can be decoupled by a selector handle so that a manual operator can be
engaged to operate the switch. Selector handle positions are Manual-Off-Motor.
Figure 2: General Switchgear Type MSO motor operator
Motor operator are commonly associated with outdoor switches but can be fitted
into metal enclosed switch units. Their design and configuration are more compact
since it must be fitted within the confines of the enclosure space. Indoor motor
operator drive the same operating shaft though a clutch coupled shaft where the
motor exert the force requires to operate the operating shaft.
Page 16 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Figure 3: General Electric Motor Operator for Masterbreak Switch
3.1.2 Load Break Switch
Load break switches are designed for breaking normal load currents. Load current
interruption is accomplished with the inclusion of arc interrupting hardware and a
quick make / quick break operating mechanism.
E.g. Spring assisted quick-break arcing contact and arc chute.
The quick-make operation provides the rated fault closing ability and the quickbreak provides the rated load interrupting ability. The breaking rating is usually the
same as the continuous current rating, never greater but sometimes lesser.
Arc interruption hardware can comprise of:
• Air puffer by compressed pistons
• Arc chutes and spring assisted arcing contacts
• Other arc interrupting technology
The operating mechanism consists of powerful opening / closing spring
and an off-center mechanism. The switch operating shaft is either direct driven by
a side mounted operating handle or driven by front mounted operating handle via
chain drive and sprocket. When the handle is rotated, it rotates the operating shaft
and charges the spring. Continued rotation of the shaft will drive the spring offPage 17 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
center and releases its energy rotating the shaft in a single snap action. Once the
springs are moved off-center, the operator has no control of the opening or closing
operation.
Other mechanisms can be fitted to most load break disconnect to accommodate:
Motor operated tripping and closing
Shunt tripping and closing
Mechanical fuse tripping
Figure 4: General Electric Load Break Switch
3.1.3 Interrupter Switch
Interrupter switches are switches which have been provisioned with interrupter
units having a load interrupting rating. Current interruptions are performed by the
interrupters without external arc after the main current carrying contacts have
separated.
During the opening cycle, as the blades begins to open, current is transferred to the
interrupter unit before the main contacts part. Continued opening of the blades will
toggle the interrupter’s mechanism resulting in contact opening in the interrupters.
During the closing cycle the blades and interrupters are sequenced to ensure that
current is picked up by the fault closing main contacts and not by the interrupter
Page 18 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
units. Once the main contacts are closed, switching mechanism will reset and close
the interrupter contacts and readies it for the next opening cycle.
3.1.4 Grounding Switch
Grounding switches are used for grounding purposes and may be used in single
pole of group operated arrangement. Ground switch has no continuous current
rating but has a fault current endurance rating and are manually operated.
3.1.5 Fault initiating Switch
Fault initiating switch is a high speed grounding switch with a rated fault making
current rating.
The switch closing can be performed by:
• High speed, high torque motor
• Unlatching a spring charged mechanism
The switch opening can be performed by:
• High speed, high torque motor
• Manually
Fault initiating switches are used for on transformer protection scheme which lacks
an incoming breaker. During a transformer fault, the transformer protection
initiates closing of the switch simulating a phase-to ground fault on the line so that
remote line protection schemes will operate and trip its breaker(s).
Fault initiating switch can be fitted with a disconnect switch for testing and
maintenance.
Page 19 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
3.2 Construction Design:
Disconnect switch can be designed for vertical or horizontal operation and operates
as a three pole device.
Basic design features are:
• Vertical break
• Double break
• Side Break
• Center-break
Figure 5: Joslyn Outdoor Vertical and Side Break Disconnect Switches
Page 20 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Figure 6: Joslyn Outdoor Center and Double End Break Disconnect
Switches
Page 21 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
4. Glossary of Terms
4.1 Switch Types
Air Switch
A switch in which the air is used as the dielectric medium between the open
contacts (e.g.air break switch).
Center Break Switch
A switch with two rotating insulators, located at each end of the base. The rotation
of the insulators causes the blade and contact to make / break at a point
approximately in the center between the insulators.
Disconnect Switch
A disconnecting switch is an air switch used for changing connections in a circuit
or system, or used for isolating purposes. It is intended to be operated under noload condition as it has no interrupting rating.
Double Break Switch
A switch with a center rotating insulator column supporting a conducting rod
equipped with moving contacts at both ends. The center insulator column rotates to
make / break with the fixed contacts mounted on two insulator columns to engage
the moving contacts.
Load Interrupter Switch
A switch having a rated current interrupting rating equal to the continuous current
rating of the switch at rated maximum voltage. Arc interruption technology is
incorporated into the switch design (e.g. arc chutes / auxiliary blade or air blast).
Fused Disconnect switch
A switch and fuse unit in which a fuse or fuses is connected in series with the
switch on each phase. The fuse in connected on the load side of the switch for
which the downstream side becomes the load terminal.
Grounding Switch
A switch which has the load side connected to earth for the purpose of grounding
the circuit where the line side is connected to. A ground switch has no current
rating.
Page 22 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Fault Initiating Switch
A switch design to operate at high speed using spring charged mechanism for the
purpose of initiating a phase-to-ground fault condition. The stored energy system
(e.g. spring charged) provides the required energy for high speed closing. The
switch has a fault making rating.
Fault initiating switch is also called a high speed grounding switch.
Horn Gap Switch
A switch which has been provisioned with arcing horns to minimize the contact of
the stationary contacts and the moving contacts. The arcing horns are designed to
carry the arc with the moving contact assembly which has been fitted with an
arcing tip. The arcing horns are fitted to the stationary contact assembly.
Interrupter Switch
A switch and interrupter unit with an interrupter is connected in series with the
switch on each phase. The interrupters are capable of interrupting short circuit
currents.
Isolating Switch
A switch used for isolating an electric circuit from its source of power. It has no
interrupting rating and is intended to be operated after the circuit has been opened
by other devices.
Oil Switch
A switch designed to operate completely immersed in oil. The oil serve as the
primary insulating medium for the internal live parts to the grounded tank or frame
and also serve as the arc quenching medium during arc interruption.
Rotating Insulator Switch
A rotating insulator switch is a switch in which the opening and closing travel of
the blade is accomplished by the rotation of one or more of the insulators
supporting the moving parts of the switch.
Page 23 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Sectionalizing switch
A switch used for the function of sectionalizing part of a circuit (e.g. bus or
feeder). Bus sectionalizers are three-pole devices and normally operated in the
closed position. Feeder sectionalizers can be single phase or three phase devices
(e.g. oils switch).
Side Break Switch
A switch possessing moving parts which operates in a plane parallel to the base of
the switch.
Single Break Switch
A switch which opens at one point only is a single break switch.
Tilting Insulator Switch
A switch in which the opening and closing travel of the blade is accomplished by a
tilting movement of one or more of the insulators supporting the conducting part of
the switch.
Vertical Break Switch
A switch possessing moving parts which operates in a plane perpendicular to the
base of the switch.
4.2 Operation
Direct Operation
Direct operation of a mechanically operated switch is the operation by means of a
mechanism connected directly to the main operating shaft, or an extension of it.
Group Operation
Group operation of a multi-pole switch is the operation of all poles by means of
one operating mechanism.
Hook Operation
Hook operation of a switch is the operation manually by means of a switch hook.
Page 24 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Indirect Operation
Indirect operation of a switch is the operation by means of an operating mechanism
connected to the main operating shaft, or an extension of it, through offset linkage
and bearing.
Manual Operation
Manual operation of a switch is the operation by hand without using any other
source of power.
Mechanical Operation
Mechanical operation of a switch is the operation by means of an operating
mechanism connected to the switch by mechanical linkage. The operating
mechanism may either be hydraulic, pneumatic, or a combination of both. The
mechanical operation of a switch may be actuated either manually, or electrically,
or by other suitable means.
Operating Mechanism
The operating mechanism of a switch is a power operated or manual mechanism by
which the contacts of all poles are actuated.
Operation
The operation of an air switch is the method provided to perform its normal
function, that of opening or closing.
Power Operation
Power operation of a switch is the operation by power, such as motor operator,
spring operator, pneumatic operator, or hydraulic operator.
Remote Controlled Operation
Remote controlled operation of a switch is the operation by means of an operating
mechanism controlled from a distant point either manually and/or electrically or by
other means.
Page 25 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
4.3 Construction & Parts
Arcing Contacts (Arcing Horns) (Parking Horns)
Arcing contacts are the contacts on which the arc is drawn after the main contacts
of a switch have parted.
Base
A base of a switch is the main member to which the conducting parts or insulator
unit are attached. It may also have parts of the operating or control mechanism
attached.
Bell Crank or Outboard Bearing
A bell crank is a lever with two or more arms placed at an angle diverging from a
given pivot point, by means of which the direction of motion of a mechanism is
changed.
Bell Crank Hanger
A bell crank hanger is a support for a bell crank.
Blade
A switch blade is the moving contact member which moves to engage or disengage
the conductors.
Blade Guide
A blade guide of a switch is an attachment to secure proper alignment of blade and
contact when closing the switch.
Blade Latch
A blade latch is a latch used on a switch to hold the switch blade in the closed
position.
Clevis
A clevis is a fitting having a U-shaped end and arranged for attaching to the end of
a pipe or rod.
Contact
The contact is a conducting part designed to be united by pressure to another
conducting part for the purpose of carrying current.
Page 26 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Contact Surfaces
Contact surfaces are the surfaces of contacts which meet and through which the
current is transferred when the contacts are closed.
Current Carrying Parts
Current carrying part is a conducting part intended to be connected in an electric
circuit to a source of voltage.
Extended Outrigger Clamp
An extended outrigger clamp is an attachment fastened to the terminal pad of a
switch to which the conductor is clamped to relieve mechanical strain on the
terminal.
Inter-phase Connecting Rods
Inter-phase connecting rods are the rods connecting the several poles of a switch
together, and to the operating rods.
Live Parts
Live parts are those parts which are electrically connected to points of potential
different from that of the ground.
Moving Contact Member
A moving contact member of a switch is a conducting part which bears a contact
surface that moves to and from the stationary contact.
Operating Rods
Operating rods are connected to the moving contact which deliver the rated force
and speed required for proper operation of the switch.
Outrigger
An outrigger is an attachment which is fastened to or adjacent to the terminal pad
of a switch and to which the conductor is clamped to relieve mechanical strain on
the terminal and/or to maintain electrical clearance between the conductor and the
grounded parts.
Pipe End (Rod End)
A pipe end is a fitting arranged to connect the end of a pipe or rod to a lever, bell
crank, or other part.
Page 27 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Pole
A pole of a switch consists of the parts necessary to control one conductor of a
circuit. A switch may be single pole or multi-pole, depending upon the number of
single poles that are operated simultaneously.
Sleet Hood
A sleet hood of a switch is a cover for the contacts to prevent the accumulation of
sleet from interfering with the successful operations of the switch.
Stationary Contact Member
A stationary contact member of a switch is a conducting part which bears a contact
surface that remains stationary.
Switch Mechanism
A switch mechanism is an assembly of levers and other parts which actuate the
moving contacts of the switch.
Terminal Pad
A terminal pad of a switch is the extension provided on the switch to which the
terminal connection is fastened.
Wire Guide
A wire guide is an attachment to maintain a conductor in a definite position with
relation to the switch.
Page 28 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
4.4 Miscellaneous Terminology
Clearance
Clearance is the minimum distance between two conductors, between conductors
and supports or other objects, or between conductors and ground.
Corona
Corona is a luminous discharge due to ionization of the air surrounding a
conductor around which a voltage gradient exists exceeding a certain critical value.
Drip-proof
Drip-proof means go constructed or protected that its successful operation is not
interfered with when subjected to falling moisture or dirt.
Drip-tight
Drip-tight means so constructed or protected as to exclude falling moisture or dirt.
Ground
A ground is a conducting connection, between an electric circuit or equipment and
earth, or to some conducting body which serves in place of' the earth.
Grounded
Grounded means connected to earth or to some conducting body which serves in
place of the earth.
Grounded Parts
Grounded parts are those parts which are so connected that, when the installation is
complete, they are substantially of the same potential as the earth.
Insulator Unit (Insulator Stack)
The insulator unit of an air switch is the insulating part or assemblies that isolates
the current carrying parts from ground.
Interlock
An interlock is a device actuated by the operation of some other device with which
it is directly associated, to govern succeeding operation of the same or allied
devices.
Page 29 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Minimum Clearance Between Poles
The minimum clearance between poles is the shortest distance between any live
parts of adjacent poles.
Minimum Clearance to Ground
The minimum clearance to ground is the shortest distance between any live part
and adjacent grounded parts.
Phase Spacing
The phase spacing of air switches is the distance between centers of the live parts
or conductors of one pole and the current carrying parts of an adjacent pole.
Quick Break
A switch is quick break when it has a high contact opening speed independent of
the operator.
Quick make
A switch is quick make when it has a high contact closing speed independent of the
operator.
Spark Gap
A spark gap is an arrangement of two electrodes between which a disruptive
discharge or electricity may take place, and such that the insulation is self restoring
after the passage of a discharge.
Switch Hook
A switch hook is a hook provided with an insulating handle for opening and
closing hook operated switches.
Voltage to Ground
The voltage to ground is the voltage between any live conductor or a circuit and
the earth.
Watertight
Watertight means provided with an enclosing case which will exclude water
applied in the form of a hose stream for a specific time.
Page 30 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Weatherproof - (Outdoor)
Weatherproof means so constructed or protected that exposure to the weather will
not interfere with its successful operation.
Page 31 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5 Switch Testing
Note: The testing procedures described in this module are for air switches having
blade contacts of the station class, indoor and outdoor type or of the metal
enclosed type. The procedures are general in nature and it does not
differentiate the nuances in the various type of switch design. Task steps
which are not applicable to the respective switches should be treated as not
applicable.
The test procedures can also be applied for distribution class, switch hook
operated air switches.
Note: Always wipe and clean any apparatus before performing any high voltage
insulation / resistance test, with a lint free rag.
Note: Mechanical and electrical testing go hand in hand in the testing of switches.
High contact resistance value requires mechanical adjustments. Mechanical
adjustments requires electrical testing to confirm if the adjustments are
performed correctly
5.1 Safety Considerations
5.1.1 High Voltage Safety
Many of the tests involve the use of high voltage test equipment; testing should be
performed by qualified personnel familiar with the test set operations and the
hazards associated with the tests.
Refer to Module 2 for Safety Working Practices and Guidelines.
Refer to IEEE Standard 510 – 1983, Recommended Practice for Safety in High
Voltage & High Power Testing.
Page 32 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.1.2 Electrostatic Charge
After any high potential voltage is removed, an electrical charge may be retained
by the insulating bushing. Failure to discharge the residual electrostatic charge
could result in an electrical shock. Always ground the last test point before moving
the test set high voltage lead.
5.1.3 Stored Energy
Fault Initiating Switch
Fault initiating switches can rely on the release of stored energy devices for its
closing functions. Stored energy devices typically consists of a spring charged
mechanisms with a release latch, which could be electrically unlatched. Care
should be taken to isolate the secondary controls to prevent inadvertent unlatching
when working on the equipment.
Load break Switch
Load break switch uses charged spring energy to produce the required quickmake / quick-break operations. Foreign material such as test leads and tools should
be removed from the enclosure prior to performing any closing or opening
operations.
5.1.2 Working at Heights
Outdoor and indoor open-type station class switches are typically mounted with a
high ground clearance as required for station design and to be in-line with the bus
structure. Access to the switches will require working at elevated levels. Anyone
working at elevated level should be trained for working at heights and use the
required fall arrest / restraint gear, erect warning signs and obtained the required
permit if applicable.
Page 33 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.2 Mechanical Testing:
The mechanical testing of switches is detailed in its scope and if performed
properly will contribute to the reliability and long operating life of the switches.
Mechanical testing consists of:
• Mechanical inspection
• Manual operations
5.2.1 Mechanical Inspection
The purpose of the mechanical inspection is to:
•
Verify the ratings matches the design specifications
•
Verify the installation
•
Determine any damages resulting from installation / transport
Items for inspection checks are:
• Examine insulators for cracks or defective parts
• Check and lubricate contacts as recommended by the manufacturer
• Examine locks for security, function and ease of operation
• Check the operating mechanisms
• Check for lost motion or binding of the operator
• Check adjustment of horns on horn-gap switches
• Check break distances, clearances between live parts and travel of all
switches.
• Check phase-to-phase and phase-to-ground clearances between live parts or
between the switching equipment and adjacent structures
Page 34 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Mechanical Inspection Procedure
1. Confirm the nameplate rating with the contract specification, bill of material list
or applicable drawings / one line diagrams / three line diagrams.
3. Confirm that the cubicles or frame are properly grounded.
4. Confirm that the cubicles / structures are installed level and plumb.
5. Inspect the switch for signs of damage during shipping or installation.
6. Check the support bushing or column insulators for any signs of chipping or
cracking.
7. Ensure that the correct switch is in the correct location / position.
8. Check the required clearance and cable drop distance requirements as per
manufacturer’s manual.
9. Verify tightness of accessible bolted electrical connections by calibrated torquewrench method in accordance with manufacturer’s published data or Table 2 of
module 2.
10. Confirm fuse size, type and rating as per bill of material list or applicable
drawings / one line diagrams / three line diagrams.
11. Record as found / as left counter readings
5.2.2 Manual Operations Test
The purpose of the operations test is use to check:
• The manual operator is working properly
• The switch is adjustments correctly
The manual operations tests consist of:
• Manual operator test
•
Main Blade and Auxiliary Contact Alignment Check
•
Contact Pressure Checks
•
Mechanical Safety Interlock Test
•
Motor Operator Auxiliary / Limit Switch Test
Page 35 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Types of outdoor manual operators:
• Rotating hand wheel (outdoor)
• Rotating crank / lead screw or worm gear drive (outdoor)
• Torsional direct drive hand operator (outdoor)
Types of indoor manual operator:
• Side mounted operating handle
• Front panel mounted operating handle (indoor)
For outdoor motor operated disconnect switches, the motor operator must be
disengaged /decoupled when performing a manual operations test. Motor operated
switches are provided with a Manual-Off-Motor selector handle. The selector
handle must be moved to the Manual position.
Placing the selector handle to the Manual position performs two functions:
•
Disengages the motor from the gear train by disconnecting an
intermediate gear clear off its mesh with the mating gear
•
Opens a cut-out switch in the motor power circuit
For outdoors / indoor metal enclosed switches, the locking pin must be pulled to
permit rotation of the operating handle. The pin must be pulled, turned and set on a
raised shoulder. Placing the locking pin on the shoulder will unlock the operating
handle. Putting the locking pin back into the housing will block the operating
handle.
Manual Operations Test Procedure
Note: Perform a three-phase slow close operation by removing the spring tube
assembly containing the main spring and drive plunger.
The spring tube assembly is removed by removing the outside cotter pin
securing the spring tube assembly to its pivot pin. The main spring is
discharged when the switch is in the Open or Close positions.
Refer to figure 8, Powercon P.I.F. Mechanism Explode View Diagram
1. Remove / isolate all control power to the:
Page 36 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Shunt trip device
• Local / remote motor control circuit
• Local / remote indication circuit
•
2. Perform a slow Close operation until the blades enter or touch the stationary
jaw contacts.
Verify the following:
• The moving contacts to fixed contacts alignment
• The auxiliary contact to arc chute alignment
• Arcing contacts make before main contacts
• Moving contacts are synchronized
Note: Refer to procedure 5.2.4.1, Manual Operator Test Procedure which details
the requirement for performing contact resistance test as a critical part of the
mechanical testing.
3 Close the switch until the moving contacts are fully inserted into fixed contact
or until mechanical stops are encountered
Verify as per manufacturer’s manual.
• Penetration depth for knife blade switches
• Penetration depth for auxiliary contacts
4. Verify limit switches / auxiliary contacts in the fully Close position
• Motor Close stop limit switch / contact
• Motor Open stop limit switch / contact
• Close indication limit switch / contact
• Open indication limit switch / contact
5. From a Close position, perform a slow Open operation until the main contacts
disengage from the stationary contacts.
Verify the following:
• Auxiliary /arcing contacts are connected.
• Moving contacts are synchronized
6. Verify limit switches / auxiliary contacts in the Just-Open position
• Motor Close stop limit switch / contact
• Motor Open stop limit switch / contact
Page 37 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
•
•
Close indication limit switch / contact
Open indication limit switch / contact
7. Verify the moving to stationary contact distance when the auxiliary contact /
arcing contact exits the arc chute as per manufacturer’s manual.
8. Verify the switch final Open position as per manufacturer’s manual.
9. Verify limit switches / auxiliary contacts in the fully Close position
• Motor closing stop limit switch / contact
• Motor opening stop limit switch / contact
• Close position limit switch / contact
• Open position limit switch / contact
10.From an Open position, perform a slow Close operation until the moving
contacts just leave the fully Open position.
11.Verify limit switches / auxiliary contacts in the Off-Open position
• Motor closing stop limit switch / contact
• Motor opening stop limit switch / contact
• Close position limit switch / contact
• Open position limit switch / contact
Page 38 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.2.4.1 Manual Operator Test Procedure:
1. Operate the switch several times checking for main blade and arcing blade
alignment. Open and close the switch 2-5 times in succession.
2. Ensure that the switch moves freely and that there is no evidence of stickiness or
binding.
3. Measure the main contact resistance at the stationary jaw / moving contacts
points and at the hinge contact location.
Note: An overall resistance tests can be substituted by measuring the resistance
between the load and line side spade terminals with the main contacts close
on a per pole basis. Measuring the individual resistance value at the
stationary jaw / moving contacts points and at the hinge contact location is a
more detail tests.
4. Ensure that resistance values are within the manufacturer’s specified range.
5.2.4.2 Main Blade and Auxiliary Contact Alignment Check
Main blades and auxiliary contacts alignment check can be performed on an
individual basis. The insulating operating rods (or pushrods) can be disconnected
from the main crank by removing the cotter pins and the clevis pins.
The main blades can now be operated by hand to check:
• Blade alignment / penetration
• Auxiliary (or arcing contact) alignment / penetration
Main Blade and Auxiliary Contact Alignment Adjustment Procedure
Note: The contact alignments are required to be performed by some manufacturer
only if the contact resistance values are not within the specified range. This
writer recommends that contact alignment test procedure be performed even
if the resistance values falls within specified range.
1. Disconnect the pushrods by removing the cotter pins and the clevis pins that
connects the insulating push rods to the main operating crank arms of each pole.
Page 39 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
2. Disengaged the moving switch blades by pulling outward on the main switch
blade until the main blades are separated from the fixed jaw casting.
3. Continue to pull outward until the auxiliary (arcing) contact blade disengages
from the arc chute.
Warning: The auxiliary contact blades are under spring pressure and will snap
open when it clears the stationary arcing contacts in the arc chutes.
Keep clear of the auxiliary contact blades when performing an Open
operation.
4. Verify that the main blades align with the jaws of the fixed contact
a. If necessary to adjust, loosen the hinge casting mounting bolts and move
the pole assembly until the moving and fixed contacts are aligned, then
re-tighten the bolts.
5. Verify that the jaw casting contact surfaces align with the main blades.
a. If necessary to adjust, loosen the jaw casting mounting bolts, tap on the
spade terminal to align Re-tighten the bolts.
6. Verify proper alignment of the arcing contact with the opening in the arc chute
by slowly moving the main blades in and out
a. If necessary to adjust, loosen the jaw casting mounting bolts and lightly
tapping on the arc chute mounting bracket.. Re-tighten the bolts.
c. If correction in the arcing blade position is required after all previous
adjustments are completed, loosen the locknut on the arcing blade
adjustment screw and turn the screw in the direction required to
reposition the arcing blade. Re-tighten the locknut.
Page 40 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 9: Figures for Switch Alignment Test Procedures
Step 1
Step 2,3 and 4
Removing Cotter pin and clevis pin
Main blade and jaw casting alignment
Step 4a
Step 5 and 5a
Hinge casting bold adjustment
Jaw casting & spade terminal bolt
adjustment
Step 6 and 6a
Step 6b
Arc chute adjustment
Arcing blade set screw adjustment
Page 41 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.2.4.3 Contact Pressure Checks
The contact pressure checks can be performed on an individual basis after the
contact alignment procedure has been completed, with the pushrods disconnected
from the main crank arm.
Contact pressure adjustments are performed at two contact points:
• Hinge Contacts
• Jaw Contacts
Contact Pressure Adjustment Procedure
Note: The contact pressure adjustments are required to be performed by some
manufacturer if the contact resistance values are not within the specified range.
This writer recommends the contact pressure adjustment procedure be performed
even if the resistance values falls within the specified range.
1. Open the switch until the arcing blade just clears the arc chute.
2. Connect a spring scale to the main blades approximately 1.5” below the jaw
contact or connect to the spacer between the main blades if it is present.
Note: A Tee adapter may have to be used if there is no spacer or if the spacer
is too fart from the jaw contact location.
3. Verify the pulling force required to overcome the hinge contact resistance as
per manufacturer’s specifications.
a. If necessary to adjust, loosen or tighten the hinged bolt as necessary to
obtain the required pulling force for moving the main blades.
4. Close the main blades and set it fully into the jaw contact assembly.
5. Verify the pulling force required to dislodge the blades from the jaw contacts as
per manufacturer’s specification.
Page 42 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Table 10: Figure of Scale Placement For Pressure Adjustment Measurement
Step 2,3 and 3a
Step 4 and 5
Hinge pressure measurement
using 10 pound scale
Jaw Pressure measurement using
50 pound scale
Step 4 and 5
Jaw Pressure measurement using
50 pound scale
5.2.4.4 Mechanical Safety Interlock Test
Door Interlock
The door interlock prevents the door of the enclosure from being opened when the
switch main blades are in the Close position. When the operating handle is in the
Close position, it captures the door latch and prevents the door from being opened.
Switch interlock
The switch interlock prevents closure of the switch when the enclosure door is
open. When the door is open and the handle is in the Open position, a pushrod is
inserted into a notch in the operating handle mechanism preventing the handle
from being moved to the Close position.
Page 43 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Caution: It is recognized that the switch interlock must be defeated to allow the
manual operating handle to function to operate the switch for testing
purposes. No equipment / test lead or personnel should be within the
enclosure space when the switch is being operated.
Key Interlock
Key interlock prevents the operation of the switch’s operating handle as well as
locking the main door in the closed position. The key must be inserted into the
interlock and rotated to retract the locking bolt.
Caution: Do not operate the handle when the interlock bolt is extended as it will
result in equipment damage.
The interlock scheme can be set up for locking the switch in the open or closed
position. The key can only be removed when the lock bolt is in a predetermined
position, thereby releasing one or more keys for the next step in a sequence.
Mechanical Interlock Test Procedure
Note: The noted procedure is for a key interlock which prevents opening of the
switch until the key interlock is inserted and rotated.
1. With the switch in the Close position, attempt a manual Open operation when
the key is not inserted in the cylinder unit.
Verify that the manual operator is blocked from opening.
2. Insert and rotate the key in the cylinder unit.
Verify that the handle is free to operate to open the switch
3. Check that the door interlock is functioning.
Verify that the enclosure door cannot be opened when the switch is Close.
4. Open the switch. Open the enclosure door.
5. Check the switch interlock.
Page 44 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Verify that the operating handle is blocked from closing when the enclosure
door is open.
5.2.4.5 Motor Operator Auxiliary / Limit Switch Test
Note: The noted procedure is for metal enclosed switch with motor operated
disconnect switches fitted with cam-operated limit switches within the motor
operator assembly.
The manual operator is used to operate the switch and move the drive train which
is connected to the cam operated limit switch assembly. A rotating cam actuates
the roller of a snap action micro switch using separately mounted cam mounted on
a shaft. The cams are adjustable through 360 degrees so that each stage can be
operated as an ‘a’ or ‘b’ contact.
The figure below show the cam timing diagram for a typical motor operated
disconnect switch.
• Motor limit switches are set to operate the motor for the full travel. Cut-off
is established at the end of the Close and Open operation.
• Indication limit switches are set to indicate only when the switch has
reached the end of its travel. Open and Close are not indicate during the
travel duration.
Figure 7: Motor Operator Limit Switch Cam Timing Diagram
Page 45 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Motor Operator Auxiliary / Limit Switch Test Procedure
Note: Operate the switch with the manual operator when checking limit switch can
timing setting.
1. Placed the switch in the fully Open position.
Verify that the limit switch contacts are set as per contact timing diagram.
2. Rotate the switch in the Close direction until the moving contacts moves about
5% from the Open position.
Verify that the limit switch contacts are set as per contact timing diagram.
3. Place the switch in the fully Close position.
Verify that the limit switch contacts are set as per contact timing diagram.
4. Rotate the switch in the Open direction until the moving contacts moves about
5% from the Close position.
Verify that the limit switch contacts are set as per contact timing diagram.
Page 46 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Figure 8: Powercon Corp P.I.F. Mechanism Explode View Diagram
Page 47 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.3 Electrical Testing
Electrical testing consists of:
• Insulation resistance test
• Dielectric withstand test
• Contact resistance test
• Fuse resistance test
• Fuse holder resistance test
• Operations test
5.3.1 Insulation Resistance Test
The insulation resistance test is a DC voltage test conducted at 100% of the rated
AC insulation phase-to-ground crest level. The DC equivalent is at 1.414 of the AC
RMS rated insulation to ground value.
Note: The above value is higher than the recommended NETA insulation
resistance test level. In the opinion of this writer, the higher value is a more
practical level since the insulation will be stressed at the operating value.
Note: For indoor switches, the insulation resistance tests can be combined with the
switchgear insulation resistance test when the switch in directly connected to
the main bus, in the connected position and the contacts closed.
Note: For outdoor switches and indoor open style station class switches, the
insulation resistance tests can be combined overall bus bars when the switch
in directly connected to the bus and the contacts closed.
The results of the test serves as a preliminary assessment of the primary insulation
system to determine if it is should be subjected to the power frequency dielectric
withstand test.
Note: Insulation resistance testing is best performed when the ambient temperature
is at 20° C.
Page 48 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Figure 6: Insulation Resistance Test Connection Diagram.
Insulation Resistance Test Procedure
1. For indoor / outdoor metal enclosed switches, isolate the equipment, apply
working grounds to all incoming and outgoing cables and disconnect all
incoming and outgoing cables from the spade terminals. Disconnected cables
should have sufficient clearance from the switchgear terminals greater that the
phase spacing distance. Use nylon rope to hold cable away from incoming and
outgoing terminals as required.
2. Ensure that the equipment is properly grounded.
3. Close the main contacts.
4. Apply the test voltage at the test duration on phase-A terminals with the frame
and all other phases grounded.
5. Record test values
6. Repeat step 5 and 6 for phase-B and phase-C
5.3.2 Power Frequency Withstand Test
The 60 Hz dielectric withstand tests are conducted at 75% of the factory dielectric
withstand test voltage level of the test values given in Table 2, 3 or 4.
Page 49 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
The AC test voltage shall have a crest equal to 1.414 times the RMS value
specified in Table 2, 3 or 4. The wave shape shall be essentially sinusoidal. The
frequency shall be within 20% of the rated power frequency. The test voltage is to
be increased gradually from zero at a rate no greater than 1000 V per second to
reach the required test value and shall be held there for 1 minute.
Figure7: Vacuum and SF6 Circuit Breakers Dielectric Withstand Test
Connection Diagram.
Power Frequency Withstand Test Procedure
1. For indoor / outdoor metal enclosed switches, isolate the equipment, apply
working grounds to all incoming and outgoing cables and disconnect all
incoming and outgoing cables from the spade terminals. Disconnected cables
should have sufficient clearance from the switchgear terminals greater that the
phase spacing distance. Use nylon rope to hold cable away from incoming and
outgoing terminals as required.
2. Ensure that the equipment is properly grounded.
3. Close the main contacts.
5. Apply the test voltage at the test duration on phase-A terminals with the frame
and all other phases grounded.
Page 50 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
6. Record test values.
7. Repeat step 5 and 6 for phase-B and phase-C.
8. Open the main contacts.
9. Apply the test voltage at the test duration on phase-A incoming terminal with
phase-A outgoing terminal and all other phases grounded.
10.Record test values.
11.Apply the test voltage at the test duration on phase-A outgoing terminal with
phase-A incoming terminal and all other phases grounded.
12.Record test values.
13.Repeat step 9 to 11 for phase-B and phase-C.
Page 51 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.3.3 Contact Resistance Test
The contact resistance test is performed by injecting a constant 100Adc current
between the incoming and the outgoing terminals on each phase. The voltage drop
across the main contact is read using a 4-wire resistance measurement circuit
which eliminates the measuring voltage leads wire resistance to obtain the contact
resistance value.
The switch contact resistance test should be measured from spade terminal to
spade terminal with the switch in the closed position. The best lead placement
using the 4 wire method is to place the current source leads furthest from the
resistance to be measured and the voltage measuring leads closest to the resistance
to be measured.
Figure 9: Contact Resistance Measurement Connection Diagram.
Contact Resistance Test Procedure
1. Close the main contacts.
2. Connect the +ve current lead at the incoming primary terminal on phase-A and
the –ve current lead on phase-A outgoing terminal.
3. Connect the +ve voltage lead at the incoming primary terminal on phase-A and
the –ve voltage lead on phase-A outgoing terminal.
Note: Place the voltage leads between the current lead and the main contact.
Page 52 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
4. Inject 100 Adc through phase-A main contacts.
5. Record test value.
6. Repeat step 2 to step 5 for phase-B and phase-C
5.3.4 Fuse Resistance Test
A cold resistance fuse test provides the primary indication of the fuse’s condition.
Manufacturer’s data may provide typical values or a high and low range values
normally reference to 20º C. Fuse resistance assessment should be compared to
published data.
The fuse resistance test is performed by injecting a constant 1 Adc or 10 Adc
current between end caps of the fuse. The best lead placement using the 4 wire
method is to place the current source leads furthest from the resistance to be
measured and the voltage measuring leads closest to the resistance to be measured.
The resistance measurements can be made with the fuses left in the fuse holder.
Figure 9: Fuse Resistance Test Connection Diagram
Fuse Resistance Test Procedure
Page 53 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
1. Connect the first low current DLRO measuring paired leads to one cap of
phase-A fuse, ensuring that the current injection probe tip is farthest from the
fuse barrel.
2. Connect the second measuring paired leads to the other cap, ensuring that the
current injection probe tip is farthest from the fuse barrel.
3. Inject either 1 Adc or 10Adc but not exceeding the fuse current rating.
4. Record test value
5. Repeat steps 1 to 4 for phase-B and phase-C fuses.
5.3.5 Fuse Holder Resistance Test
The fuse holder resistance test is performed by injecting a constant 1 Adc or 10
Adc current between end caps of the fuse and the fuse clip assembly or at the
bolting plate. The best lead placement using the 4 wire method is to place the
current source leads furthest from the resistance to be measured and the voltage
measuring leads closest to the resistance to be measured.
Figure 10: Fuse holder /clip Resistance Measurement Connection Diagram
Page 54 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Fuse Holder Resistance Test Procedure
1. Connect the first low current DLRO measuring paired leads to the outside of the
fuse clip on phase-A, switch side, ensuring that the current injection probe tip is
farthest from the fuse barrel.
2. Connect the second measuring paired leads to the end cap, ensuring that the
current injection probe tip is closest to the fuse barrel.
3. Inject either 1 or 10 Adc but not exceeding the fuse current rating.
4. Record test value.
5. Repeat steps 1 to 4 for phase-A load side fuse holder.
6. Repeat steps 1 to 5 for phase-B and Phase-C fuse holders.
Page 55 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Figure 11 General Electric Typical Motor Operator Schematic Diagram
Page 56 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
5.3.6 Operations Test
The operations test for a motor operated switch will verify the electrical controls
for Trip and Close operations, indications and associated electrical interlocks.
Motor operators are provided with a removable manual operating handle that is
interlocked with the electrical controls. The interlock is engaged when the manual
handle is inserted in the operating slot preventing the motor circuit from operating.
Refer to figure 11 for a typical metal enclosed motor operated switch schematic.
The actual equipment schematic should be used when commissioning the control
circuits.
Operations Test Procedure
Note: Consult the manufacture’s commissioning procedure for the switch drive
type.
1. Confirm power supply polarity and magnitude to the motor operator control
circuit with the fuse(s) removed.
Re-insert the fuse (s) if polarity and magnitude is as per nameplate
requirements.
2. Return the manual handle to the cradle and turn the cradle keylock to capture
the key and close its auxiliary contact.
3. Reset any remote lockout devices connected to terminal M3-M4 in the
schematic.
4. Perform a Close operation via the local electrical local / remote controls.
Verify switch operation and indications.
5. Perform an Open operation via the local electrical local / remote controls.
Verify switch operation and indications.
Page 57 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
6. NETA Switch Acceptance Test Procedure
6.1 Switches, Air, Medium-Voltage, Metal-enclosed
6.1.1. Visual and Mechanical Inspection
1. Compare equipment nameplate data with drawings and specifications.
2. Inspect physical and mechanical condition.
3. Inspect anchorage, alignment, grounding, and required clearances.
4. Verify the unit is clean.
5. Verify correct blade alignment, blade penetration, travel stops, arc interrupter
operation, and mechanical operation.
6. Verify that fuse sizes and types are in accordance with drawings, short-circuit
study, and coordination study.
7. Verify that expulsion-limiting devices are in place on all holders having
expulsion-type elements.
8. Verify that each fuse holder has adequate mechanical support and contact
integrity.
9. Inspect bolted electrical connections for high resistance using one or more of
the following methods:
1. Use of a low-resistance ohmmeter in accordance with Section 7.5.1.2.2.
2. Verify tightness of accessible bolted electrical connections by calibrated
torque-wrench method in accordance with manufacturer’s published data or
Table 100.12.
3. Perform thermographic survey in accordance with Section 9.
10.Verify operation and sequencing of interlocking systems.
Page 58 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
11.Verify correct phase barrier installation.
12.Verify correct operation of all indicating and control devices.
13.Verify appropriate lubrication on moving current-carrying parts and on moving
and sliding surfaces.
6.1.2. Electrical Tests
1. Perform resistance measurements through bolted connections with a lowresistance ohmmeter, if applicable, in accordance with Section 7.5.1.2.1.
2. Measure contact resistance across each switchblade and fuseholder.
3. Perform insulation-resistance tests for one minute on each pole, phase-to-phase
and phase-to- ground with switch closed, and across each open pole. Apply
voltage in accordance with manufacturer’s published data. In the absence of
manufacturer’s published data, use Table 100.1.
4. Perform a dielectric withstand voltage test on each pole with switch closed.
Test each pole-to- ground with all other poles grounded. Test voltage shall be in
accordance with manufacturer’s published data. In the absence of
manufacturer’s published data, use Table 100.2.
5. Measure the fuse resistance.
6. Verify cubicle space heater operation.
6.1.3. Test Values
6.1.3.1 Test Values – Visual and Mechanical
1. Compare bolted connection resistance values to values of similar connections.
Investigate values which deviate from those of similar bolted connections by
more than 50 percent of the lowest value. (7.5.1.2.1.9.1)
2. Bolt-torque levels shall be in accordance with manufacturer’s published data. In
the absence of manufacturer’s published data, use Table 100.12. (7.5.1.2.1.9.2)
3. Results of the thermographic survey shall be in accordance with Section 9.
Page 59 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
(7.5.1.2.1.9.3)
6.1.3.2
Test Values – Electrical
1. Compare bolted connection resistance values to values of similar connections.
Investigate values which deviate from those of similar bolted connections by
more than 50 percent of the lowest value.
2. Microhm or dc millivolt drop values shall not exceed the high levels of the
normal range as indicated in the manufacturer’s published data. In the absence
of manufacturer’s published data, investigate values that deviate from adjacent
poles or similar switches by more than 50 percent of the lowest value.
3. Insulation-resistance values shall be in accordance with manufacturer’s
published data. In the absence of manufacturer’s published data, use Table
100.1. Values of insulation resistance less than this table or manufacturer’s
recommendations should be investigated. Dielectric withstand voltage tests
shall not proceed until insulation-resistance levels are raised above minimum
values.
4. If no evidence of distress or insulation failure is observed by the end of the total
time of voltage application during the dielectric withstand test, the test
specimen is considered to have passed the test.
5. Investigate fuse resistance values that deviate from each other by more than 15
percent.
6.
Heaters shall be operational.
6.2 Switches, Air, Medium and High-Voltage, Open
6.2 1. Visual and Mechanical Inspection
1. Compare equipment nameplate data with drawings and specifications.
2. Inspect physical and mechanical condition.
3. Inspect anchorage, alignment, grounding, and required clearances.
Page 60 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
4. Verify the unit is clean.
5. Perform mechanical operator tests in accordance with manufacturer’s published
data, if applicable.
6. Verify correct operation and adjustment of motor operator limit switches and
mechanical interlocks, if applicable.
7. Verify correct blade alignment, blade penetration, travel stops, arc interrupter
operation, and mechanical operation.
8. Verify operation and sequencing of interlocking systems.
9. Verify that each fuse has adequate mechanical support and contact integrity, if
applicable.
10.Verify that fuse sizes and types are in accordance with drawings, short-circuit
study, and coordination study.
11.Inspect bolted electrical connections for high resistance using one or more of
the following methods:
1. Use of low-resistance ohmmeter in accordance with Section 7.5.1.3.2.
2. Verify tightness of accessible bolted electrical connections by calibrated
torque-wrench method in accordance with manufacturer’s published data or
Table 100.12.
3. Perform thermographic survey in accordance with Section 9.
12.Verify correct operation of all indicating and control devices, if applicable.
13.Verify appropriate lubrication on moving current-carrying parts and on moving
and sliding surfaces.
14.Record as-found and as-left operation counter readings.
6.2.2. Electrical Tests
Page 61 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
1. Perform resistance measurements through bolted connections with a lowresistance ohmmeter, if applicable, in accordance with Section 7.5.1.3.1.
2. Perform contact-resistance test across each switchblade and fuseholder.
3. Perform insulation-resistance tests for one minute on each pole, phase-to-phase
and phase-to- ground with switch closed, and across each open pole. Apply
voltage in accordance with manufacturer’s published data. In the absence of
manufacturer’s published data, use Table 100.1.
4. Perform insulation-resistance tests on all control wiring with respect to ground.
Applied potential shall be 500 volts dc for 300-volt rated cable and 1000 volts
dc for 600-volt rated cable. Test duration shall be one minute. For units with
solid-state components or control devices that can not tolerate the applied
voltage, follow manufacturer’s recommendation.
5. Perform a dielectric withstand voltage test on each pole with switch closed.
Test each pole-to- ground with all other poles grounded. Test voltage shall be in
accordance with manufacturer’s published data. In the absence of
manufacturer’s published data, use Table 100.19.
6.2.3. Test Values
6.2.3.1 Test Values – Visual and Mechanical
1. Compare bolted connection resistance values to values of similar connections.
Investigate values which deviate from those of similar bolted connections by
more than 50 percent of the lowest value. (7.5.1.3.1.11.1)
2. Bolt-torque levels shall be in accordance with manufacturer’s published data. In
the absence of manufacturer’s published data, use Table 100.12. (7.5.1.3.1.11.2)
3. Results of the thermographic survey shall be in accordance with Section 9.
(7.5.1.3.1.11.3)
4. Operation counter should advance one digit per close-open cycle.(7.5.1.3.1.14)
Page 62 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
6.2.3.2 Test Values – Electrical
1. Compare bolted connection resistance values to values of similar connections.
Investigate values which deviate from those of similar bolted connections by
more than 50 percent of the lowest value.
2. Microhm or dc millivolt drop values shall not exceed the high levels of the
normal range as indicated in the manufacturer’s published data. In the absence
of manufacturer’s published data, investigate values that deviate from adjacent
poles or similar switches by more than 50 percent of the lowest value.
3. Insulation-resistance values shall be in accordance with manufacturer’s
published data. In the absence of manufacturer’s published data, use Table
100.1. Values of insulation resistance less than this table or manufacturer’s
recommendations should be investigated. Dielectric withstand voltage tests
should not proceed until insulation-resistance levels are raised above minimum
values.
4. Minimum insulation-resistance values of control wiring shall not be less than
two megohms.
5. If no evidence of distress or insulation failure is observed by the end of the total
time of voltage application during the dielectric withstand test, the test
specimen is considered to have passed the test.
Page 63 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
7. Test Set Operational Manual
Low Current DLRO
Page 64 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
8. Test Forms
Open Air Switch Test Form
Metal enclosed Switch Test Form
Page 65 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Page 66 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Page 67 of 68
EITCA Acceptance Testing and Commissioning Training Course
Module 5: MV Air Switch acceptance tests
Acknowledgement, References and Recommended Reading
Acknowledgement:
Special thanks to Morpac Industries, Inc (Mr. John Thames, General manager)
who allowed the use of their glossary of terms for inclusion in this document.
http://www.morpac.com/switches/definitions.shtml
ANSI/IEEE C37.30-1997
Standard Requirements for High Voltage Switches
Copyright © 1998 by the Institute of Electrical and Electronics Engineers, Inc.
345 East 47th Street, New York, NY 10017-2394, USA
ISBN 1-55937-964-2
ANSI C37.32-2002
High Voltage Switches, Bus Supports and Accessories
Schedules of Preferred Ratings, Construction Guidelines and Specifications
Copyright © 2002 by the National Electrical Manufacturers Association
1300 North 17th Street, Rosslyn, VA 22209
IEEE C37.34-1994
Standard Test Code for High-Voltage Air Switches
Copyright © 1995 by the Institute of Electrical and Electronics Engineers, Inc.
345 East 47th Street, New York, NY 10017-2394, USA
ISBN 1-55937-468-3
IEEE C37.35-1995
Guide for the Application, Installation, Operation, and maintenance of HighVoltage Air Disconnecting and Interrupter Switches
Copyright © 1995 by the Institute of Electrical and Electronics Engineers, Inc.
345 East 47th Street, New York, NY 10017-2394, USA
ISBN 1-55937-597-3
NEMA SG 6
Power Switching Equipment
Copyright © 2001 by the National Electrical Manufacturing Association
1300 N 17th Street, Suite 1847, Rosslyn, Virginia 22209, USA
Page 68 of 68