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PART 1- GENERAL
1.1 DESCRIPTION
A. The switch shall consist of manually operated load interrupting, SF6 insulated, 600A linear
puffer switches and manually operated vacuum interrupter fault interrupting tap switches,
electronically controlled.
1.2 QUALITY ASSURANCE
A. Manufacturer Qualifications: The chosen manufacturer shall have at least 20 years
experience in manufacturing SF6 insulated medium voltage switchgear. The manufacturer
of the switches shall be completely and solely responsible for the performance of the load
break switch and fault interrupter as well as the complete integrated assembly as rated.
B. The manufacturer shall furnish certification of ratings of the load break switch, fault
interrupter and the integrated switch assembly upon request.
C. The switch shall comply with requirements of the latest revisions of applicable industry
standards, including:
(a) IEEE C37.71, IEEE C37.74, IEEE C37.60, ANSI/IEEE 386, IEC 60265-1
D. The switch manufacturer shall be ISO 9001:2000 and ISO 14001:2004 certified.
1.3 DELIVERY, STORAGE, AND HANDLING
A. Load break switches and fault interrupters shall be shipped preassembled at the factory.
No field assembly shall be required.
B. The contractor, if applicable, shall handle, transfer and move the switches in accordance
with manufacturer’s recommendations.
PART 2- PRODUCTS
2.1 SWITCH CONFIGURATION
A. Each switch shall be equipped with 3-phase load switch ways, (quantity) 3-phase vacuum
interrupter tapped way(s) with gang linked operating handles, and single phase vacuum
interrupter tapped way(s) with individual operating handles, as indicated on the one-line
diagram.
B. Switches shall be designed for front access to cables and operators.
2.2 SWITCH CONSTRUCTION
A. General
All switch components and entrances shall be assembled in a totally welded mild steel
tank. Entrances shall be internally connected by copper conductors capable of handling
momentary and continuous current duty. The switch shall contain no electrically floating
metallic parts or components. Construction shall be a deadfront design. Switch tanks
shall be painted ASA70 light gray using a corrosion-resistant epoxy paint.
B. Load Break Switch
Each switching way is to be equipped with an internally mounted operating mechanism
capable of providing quick-make, quick-break operation in either switching direction. The
mechanism must be capable of delivering sufficient torque and shall be provided with
latches for each position to assure load interrupting, fault closing and momentary ratings.
All switch positions are to be clearly identified, padlockable and adaptable to keylock
schemes. The operating mechanism shall be actuated from outside the switch tank with
an operating handle. The operating shaft shall be made of stainless steel providing
maximum corrosion resistance. A double "O" ring type operating shaft seal shall be used
for a leak resistant, long life seal. Switch contacts shall be a tulip-bayonet design and
made of plated, high-conductivity copper alloy with arcing tips of copper/tungsten alloy to
assure permanent low resistance and to avoid sticking during operation. The contacts
shall be designed such that arcing does not occur in the area of main current interchange
and contact pressure will increase with increased current flow. The stationary contacts
shall be supported independent of the cable entrance bushings, eliminating possible
misalignment. The contact nozzle shall have a converging/diverging geometry which
improves the flow of SF6 into the arc zone. Contact travel shall be a minimum of 3 inches
and have sufficient open contact separation to assure efficient arc extinction and to
withstand field DC testing levels and maintain BIL levels. Switch contacts shall be clearly
visible in the open position through viewing windows. Auxiliary blades used for load
interruption are not acceptable.
C. Vacuum Interrupters
The vacuum interrupter shall consist of vacuum bottles and a spring-assisted operating
mechanism. The mechanism used shall be designated Model VI for single or three phase
operation. The mechanism consists of a single vacuum bottle mechanically linked to a
spring-assisted operation mechanism. For three phase operation, the single phase
mechanisms are mechanically linked externally with an operating handle assembly. The
vacuum interrupter operating mechanism shall consist of the support assembly, linkage,
spring latch mechanism, and solenoid utilized for electronic tripping. Maximum interrupting
time shall be three cycles (50 msec). The movable contact shaft shall be flagged to
indicate the contact position, open or closed. This contact position indicator shall be fully
visible through viewing windows supplied in the switch tank. Each tap phase is to be
equipped with an individual 600A vacuum interrupter fully enclosed in an SF6 insulated
switch tank. Electrical opening shall be by a solenoid that is activated from sources
external to the switch tank. Closing (reset) of the vacuum interrupter shall be mechanical
with the use of an external operating handle. The mechanical linkage assembly shall
provide for a "trip-free" operation which allows the vacuum interrupter to interrupt
independent of the operating lever.
2.3 DESIGN RATINGS
A. Load Break Switches
The switch shall be rated: (choose appropriate column)
SELECTION OF RATINGS |
IEEE/IEC |
Maximum Design Voltage, kV |
15.5 |
27 |
38 |
Impulse Level (BIL) Voltage, kV |
110 |
125 |
150 |
Continuous Current, Amperes |
630 |
630 |
630 |
Load break Current, Amperes |
630 |
630 |
630 |
One Minute Withstand (dry), AC kV |
35 |
60 |
70 |
Production Test Rating |
34 |
40 |
50 |
15 Minute Withstand, DC kV |
53 |
78 |
103 |
Momentary Current, kA, ASYM |
40 |
40 |
40 |
Fault-Close Current, kA, ASYM |
40 |
40 |
40 |
One Second Current, kA, SYM |
25 |
25 |
25 |
Mechanical Endurance, Operations |
2000 |
2000 |
2000 |
Load Break Operations at 600 Amperes |
1200 |
1200 |
1200 |
B. Vacuum Interrupters
The vacuum interrupter assembly shall be rated: (choose appropriate column)
SELECTION OF RATINGS |
IEEE/IEC |
Maximum Design Voltage, kV |
15.5 |
27 |
38 |
Impulse Level (BIL) Voltage, kV |
95 |
125 |
150 |
Continuous Current, Amperes |
600 |
600 |
600 |
Load break Current, Amperes |
600 |
600 |
600 |
One Minute Withstand (dry), AC kV |
35 |
60 |
70 |
Production Test Rating |
34 |
40 |
50 |
Symmetrical Interrupting Rating, kA* |
12 |
12 |
12 |
Asymmetrical Interrupting Rating, kA |
19.2 |
19.2 |
19.2 |
* Optional 20 kA symmetrical bottle, 600 amp continuous is available at all voltage classes
(model VI only).
ANSI C37.60 Fault Interrupting Duty
Percent of Maximum:
Interrupting Rating |
Approx. Interrupting:
Current Amps |
No. of Fault:
Interruptions |
15-20% |
2000 |
44 |
45-55% |
6000 |
56 |
90-100% |
12000 |
16 |
Total Number of Fault Interruptions: 116 |
2.4 CABLE ENTRANCES
A. Load Break Puffer Switches
Cable entrances shall be tested to IEEE 386 and be, as indicated on the switch drawing:
- ____ 600 amp G&W Quik-Change disconnectable apparatus bushing,
- ____ 600 amp Apparatus bushing,
- ____ 600 amp Universal bushing, or
- ____ 200 amp Deepwell bushing.
B. Vacuum Interrupters
Cable entrances shall be tested to IEEE 386 and be, as indicated on the switch drawing:
- ____ 600 amp G&W Quik-Change disconnectable apparatus bushing,
- ____ 600 amp Apparatus bushing,
- ____ 600 amp Universal bushing, or
- ____ 200 amp Deepwell bushing.
2.5 VACUUM INTERRUPTER CONTROL
An electronic assembly shall be provided to sense load and fault current on each phase of the
load tap circuits. The electronic control shall be powered from the current transformers mounted
inside the SF6 insulated switch tank. No external power source shall be required for overcurrent
protection. The electronic control shall monitor the current on the individual phases of the load
tap circuits using input from the internal current transformers. Electronic trip capability shall be
selectable for each phase. Temperature range shall be -30 to +50 degrees C. Minimum trip
selection shall be accomplished with selector knobs inside the electronic enclosure. Trip time
current characteristics (TCC) shall be field selectable using a dip switch. Maximum time for
power up and ready-to-trip when closing on a circuit shall be ten percent of the trip time or 1/2
cycle, whichever is greater. Trip selection may be made with the load taps energized.
2.6 FACTORY PRODUCTION TESTS
The bulk SF6 gas supply and each individual switch shall be tested for moisture content. Each
individual switch shall undergo a mechanical operation check and a leak test. The switch shall
be factory filled with SF6 and AC hi-pot tested one minute phase-to-phase, phase-to-ground and
across the open contacts. Circuit resistance shall be checked on all ways. Switches will be
shipped factory filled with SF6 gas. Tank shall be designed to withstand 15 psig internal
pressure and an external pressure of 14 psig without affecting the performance of the switch.
2.7 STANDARD COMPONENTS
The following shall be included as standard:
- Welded steel tank painted light gray with stainless steel and brass fasteners.
- Lifting provisions.
- Gas pressure gauge and fill valve.
- Grounding provisions for switch tank and all cable entrances.
- Stainless steel three line diagram and corrosion-resistant nameplates.
- Parking stands.
- Switch operating handle(s) with padlock provision and end stops.
- Type 1 vacuum interrupter electronic package including a selector switch for single or 3-phase operation and individual phase trip level.
2.8 OPTIONS
The following options shall be supplied: (check as appropriate)
- ____ 304 stainless steel tank.
- ____ 304 stainless steel enclosure.
- ____ Front/back access to cables and operators.
- ____ Temperature compensated gas density gauge.
- ____ Low pressure warning device.
- ____ SF6 density switch for SCADA or remote indication of SF6.
- ____ 4/0 brass ground lug(s).
- ____ Keylock provisions.
- ____ Keylocks to lock in open position.
- ____ 600 amp Apparatus Bushings.
- ____ 600 amp Universal Bushings.
- ____ Current transformers for load break ways.
- ____ Potential transformers for voltage monitoring and/or control power.
- ____ Automatic transfer control type ATC451-4.
- ____ Automatic transfer control type ATC101.
- ____ Motor actuators for remote switch operation.
- ____ Stationary switch control(s) for remote switch operation and SCADA integration.
- ____ DC portable switch controls for remote switch operation and SCADA integration.
- ____ Remote terminal units and communication packages for SCADA integration.
- ____ Operations counters.
- ____ Auxiliary switches for remote switch position indication.
- ____ Analog voltage sensors.
- ____ Digital voltage sensors.
- ____ Voltage indication panel(s).
- ____ Type 2 vacuum interrupter control including ground fault trip and time delay selector switches (three phase only).
- ____ Type 3 vacuum interrupter control including ground fault trip, inrush restraint, programmable vacuum fluorescent display (VFD) and RS232/485 port.
- ____ Type 4 vacuum interrupter control (same as Type 3 with laptop programming only).
- ____ External power / trip for vacuum interrupter control.
- ____ 20kA symmetrical interrupting rating.
- ____ Refill kit consisting of regulator, hose and SF6 bottle.
2.9 LABELING
A. Hazard Alerting Signs
The exterior of the padmounted enclosure (if furnished) shall be provided with “Warning--
Keep Out--Hazardous Voltage Inside--Can Shock, Burn, or Cause Death” signs. Each unit
of switchgear shall be provided with a “Danger--Hazardous Voltage--Failure to Follow These
Instructions Will Likely Cause Shock, Burns, or Death” sign. The text shall further indicate
that operating personnel must know and obey the employer’s work rules, know the hazards
involved, and use proper protective equipment and tools to work on this equipment. Each
unit of switchgear shall be provided with a “Danger--Keep Away--Hazardous Voltage--Will
Shock, Burn, or Cause Death” sign.
B. Nameplates, Ratings Labels, and Connection Diagrams
Each unit of switchgear shall be provided with a nameplate indicating the manufacturer’s
name, catalog number, model number, date of manufacture, and serial number. Each unit
of switchgear shall be provided with a ratings label indicating the following: voltage rating;
main bus continuous rating; short-circuit rating; fault interrupter ratings including
interrupting and duty-cycle fault-closing; and load break switch ratings including duty-cycle
fault-closing and short-time.
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