General and Application Information

Square D™ brand medium voltage, metal-enclosed switchgear functions as a prime component of medium voltage, electrical power distribution systems providing necessary switching and overcurrent protection for the medium-voltage feeders. It is often used in conjunction with Square D brand unit substations. The switchgear is most frequently applied as service entrance equipment, although it performs equally well in controlling substation transformers and in the sectioning of medium-voltage feeder systems.

Square D™ brand DIN-E Medium Voltage Fuse Style with HVL/cc Switchgear have the following standard features:

• Tested per ANSI standards C37.20.3, C37.20.4, C37.57, C37.58, CSA 22.2 no. 31, and CSA 22.2 no. 193, where applicable

• Over-toggle mechanism (OTM)

• Fuse/cable access panel mechanically interlocked with the load interrupter switch and the optional grounding switch

• Removable switch operating handles

• With the optional grounding switch, the cable/fuse compartment is not accessible unless the grounding switch is closed into the grounded position

• Visible isolation viewing ports to view open, closed, and grounded switch positions

• Standard live line indicators (LLIs) powered by capacitor dividers internal to the insulators

  On incoming circuits:

  • On incoming circuits:

    • Provide incoming live line indication

    • Provide incoming line de-energized indication

  • On feeder circuits:

    • Provide live load indication

    • Provide load de-energized indication

    • Provide blown fuse indication (only on wye connected systems)

    • Provide back-fed circuit indication

    • Animated mimic bus:

      • On ungrounded switches, indicates closed and open positions

      • On units with grounding switches, indicates closed, open, and grounded positions

    • Cable lugs (one set per phase)

      • Up to two 500 kcmil cables per phase in switch bays

      • Up to four 500 kcmil cables per phase in incoming line terminal chambers (20-inch [508 mm] wide bay)

Square D Brand (or Bussmann equivalent) DIN-E Medium Voltage Fuse Style with HVL/cc Switchgear

• Fuse ratings of:

  • 5.5 kV to 1080 A

  • 15.5 kV to 480 A

  • 17.5 kV to 270 A

  • 25.8 kV to 175 A

  • 38.0 kV to 115 A

Mersen CS-3 Medium Voltage Fuse Style with HVL/cc Switchgear

Mersen® CS-3 Medium Voltage Fuse Style with HVL/cc Switchgear have the following standard features:

• 600/1200 A tin-plated copper main bus

• Belleville washers for all power connections

• Bi-phenol epoxy switch enclosure and insulators

• UL/cULus labels

• Tested to IEC 420 for switch-fuse integration

• 11-gauge steel enclosure

• 0.25 x 2-inch (6 x 51 mm) copper ground bus meeting ANSI requirements for short-circuit grounding

• Duplex switches. Single, load-side access panel mechanically interlocked to block access unless both switches are opened (key interlocks are not required)

• Provision for padlocks and/or key locks (optional).

• Fuse ratings of:

  • 5.5 kV to 450 A

  • 15.5 kV to 200 A

• The Fuselogic system:

  • Mechanical lockout feature to block reclosing the switch until three new fuses are installed

  • Single phasing protection due to blown fuses with the Fuselogic system

  • Blown fuse indicating contact for remote indication (one common contact)

  • Blown/missing fuse flag on mechanism cover

• Grounding switch with full fault-making capability:

  • On incoming switches, grounds the incoming line conductors

  • On feeder switches, grounds the outgoing load conductors

• LDA option is only available for fused units with Square D brand (or Bussmann equivalent) DIN-E style Medium Voltage fuses only. Used to discharge capacitive voltage on the load side of the fuses. (Application A < 17.5 kV, 600 A only)

• Switch position auxiliary switch

• 1200 A tin-plated copper main bus

• Live Line Indicators (LLIs) on main bus

• Infrared viewing windows for main bus and fuse/cable compartments

• Dual-spring stored energy mechanism (SEM type)

• Motor operator for OTMs and SEMs

• Opening and closing coils (SEM only)

• Fast / Auto transfer configuration (Main-Main and Main-Tie-Main):

  • Electrically interlocked

  • Mechanically interlocked

  • Operated from LLIs

• Protective relaying; contact your local field sales representative for application assistance

• Duplex configuration:

  • Optional mechanical interlock to lock out simultaneous closure of both duplex switches

• Surge arresters

  System Voltage ≤ 17.5 kV in. (mm)	System Voltage 25.8 – 38.0 kV in. (mm)
  Distribution, Intermediate, and Station class ≤ 12 kV Standard 14.75 (375) switch section Optional 20 (508) and 29.50 (749) section	Load-side surge arresters (all classes) with fuses require a 39.37 (1000) wide section. If unfused, a 29.5 (750) wide section may be used
  Distribution, Intermediate, and Station class > 12 kV Standard 20 (508) switch section Optional 29.50 (749)

• Modified cubicle widths for customers wanting additional working space for cable termination and fuse removal:

• Low voltage compartment with hinged door:

  • Space for metering or relaying system

  • Space for control components

• Heaters with thermostat

• Capacitor trip unit

• Transitions to other Square D brand medium voltage equipment and power transformers.

HVL/cc switchgear (up to 15 kV, 95 kV BIL, 600 A maximum) is certified for use in Class 1, Division 2 hazardous locations. This classification usually includes locations where volatile flammable liquids, flammable gases, or vapors are used, but would become hazardous only in case of an accident or unusual operating condition.

Modifications are made to the standard switchgear including:

• Manual operation with no electrical controls, over-toggle mechanism (OTM) only

• Optional, explosion proof, T3B rated heaters with sealed connections

• Fuses without indicating pins

• Modified LLI system that includes sealed connections at the insulator and plugged test ports to block use

These modifications are essential for the equipment to meet Class 1, Division 2 requirements. These modifications cannot be altered. Do not substitute components.

The Class 1, Division 2 switchgear without heaters are T5 rated and can be used in areas where the flash point of volatile liquids, gases, or vapors is 212°F (100°C) or above. Class 1, Division 2 switchgear with optional heaters are T3B rated and can be used in areas where the flash point of volatile liquids, gases, or vapors is 329°F

The HVL/cc load interrupter switch is, by definition and standard, only required to interrupt its continuous current nameplate rating (for example, a 15 kV, 600 A rated HVL/cc can interrupt no more than 600 A). Listed below are several applications in which it is appropriate to use a shunt trip coil, as well as applications in which it cannot be used.

• Ground Fault Protection on Solidly Grounded Systems: Occasionally, Masterclad™ switchgear, specifications are written to incorporate ground fault protection. Metal-enclosed switchgear is frequently used with solidly grounded systems where available short-circuit current is 12.5 kA or more. The HVL/cc load interrupter switch cannot be considered or used to interrupt ground fault currents on solidly grounded systems because the available fault current is far greater than its 600/1200 A load interrupting rating.

• Ground Fault Current on Resistively Grounded Systems: Frequently, three-phase electrical systems have a grounding resistor. The grounding resistor limits the level of the ground fault current and consequently reduces the potential damage to the equipment. If the system is resistively grounded with a nominally rated 400 A or less grounding resistor, then it may be possible to use HVL/cc metal-enclosed switchgear to interrupt ground fault currents. Contact your local field sales representative to determine if this is an appropriate application.

• Transformer Protection Applications: Medium voltage fuses are designed as short-circuit protection devices and generally are able to provide adequate transformer overcurrent protection per National Electrical Code® (NEC®) 450.3. For applications where the fuse E rating is less than half of the rated interrupting current of the switch, it may be possible to improve the overall protection scheme. Adding overcurrent (IEEE 51) relays can provide precise overload protection for the transformer. In this application, the selection of the CT ratio and the programming of the IEEE 51 (overcurrent) relay must be coordinated by the factory to minimize the chance that the interrupting rating of the switch is not exceeded. Contact your local field sales representative for application assistance.

• Under/Over-Voltage Protection with Fuselogic System: The Fuselogic system is well suited where under/over-voltage protection is required. The shunt trip coil, actuated by the voltage sensing relays, can be used to open the switch with the loss of incoming line voltage. This application requires optional voltage transformers (VTs) and voltage sensing relays.

• Operating Times:

  • OTM: The conventional single spring over-toggle mechanism equipped with the motor operator operates in approximately five seconds.

  • SEM: The stored energy mechanism operates in approximately 100 milliseconds. The motor operator recharges the springs in approximately five seconds and prepares the switch for any required reclose operations.

Single Section Switchgear: Contains a single fused or unfused switch in a free-standing enclosure. It is ideally suited for locating close to a load to control a single medium-voltage circuit.

Special emphasis is placed on conduit area, cable entrance, and terminations. Normally, no main bus is furnished in a single section. A ground pad bonded to the steel frame is furnished with a cable lug termination.

Multiple Section Switchgear: Consists of a lineup of individual feeder switch sections connected to a common main bus. A main switch, fused or not fused, can be included in the lineup with a utility or user-metering cubicle, depending upon job requirements. A continuous ground bus is bonded to the frame of each section for the complete length of the lineup. The end cubicles have provisions for the addition of future feeder switch sections.

Outdoor Single Section HVL/cc Medium Voltage, Metal-Enclosed Switchgear

Outdoor Single Switch or Multiple Section Switchgear: Consists of medium-voltage components in a NEMA Type 3R enclosure. Access is through a gasketed, front bulkhead-type door. The enclosure is designed so that the sheared edges of the steel are not exposed. The equipment is furnished with:

• Roof sloped to rear for precipitation runoff

• Polyester-powder paint finish

• Removable operating handles are enclosed

• Formed steel channel

• Full height, gasketed outer front doors

• 11-gauge steel enclosure per ANSI C37.20.3

• Removable split rear panels

• Strip heaters in each switch section

• Door-stay rods to hold outer-hinged doors in open position

HVL/cc Load Interrupter Switches are constructed with:

• Seal for Life® epoxy switch enclosure

• Rotary double break interrupting principle

• Interruption inside sealed enclosure

• Maintenance-free contacts

• Two viewing ports to view the main switch contacts and optional ground switch contacts from the front panel

HVL/cc Load Interrupter Switch Construction

The HVL/cc switch has been designed and tested for a leakage rate that is less than 3 x 10^-6 bar.cm³ per second. The leakage rate will not exceed 0.1% of the total volume of the gas per year over the expected life of the switch.

The HVL/cc switch was introduced globally in 1990. According to the total number of installed switches since 1992 (over 250,000), the corresponding MTTF is approximately 4,300 years.

Closed

Open

Grounded

Contacts in closed position:

• Closing is high-speed and independent of the user

• Switch meets all ANSI requirements

Contacts in open position:

• Moving contacts isolated from fixed contacts by SF₆ gas

• Gap designed to withstand the recovery voltage

Contacts in grounded position:

• Closing is high-speed and independent of the user

• Grounding switch has full fault-making capability

The HVL/cc switch with the optional internal ground switch uses sulphur hexaflouride gas (SF6) for insulation and interrupting. The live parts are contained in a sealed-for-life insulated enclosure. This switch offers remarkable characteristics including:

• Increased operating reliability

• Low gas pressure–5.8 PSI ≤ 17.5 kV; 14.5 PSI at 25.8–38 kV

• Maintenance-free contacts

• High electrical endurance

In the closed position, the main switch blades are engaged on the stationary contacts. The circuit current flows through the main blades. Live line indicators (LLIs) on the front mechanism cover indicates that voltage is present on the circuit.

An operator handle inserted in the switch operator slot is used to manually rotate the switch operating mechanism counterclockwise. After the springs become fully charged, they toggle over the center position and discharge their stored energy to the switch operating mechanism. The speed of the operating mechanism is independent of the speed of the user.

The qualities of SF6 gas are used to extinguish the electrical arc. The arc appears when the fixed and moving contacts separate. The combination of the current and the magnetic field created by the current cause arc rotation around the stationary contact. This rotation produces arc extension and cooling until the arc is extinguished at current zero. After this, the distance between the fixed and moving contacts is sufficient to withstand the recovery voltage. This system provides extended electrical endurance due to very low wear on the contacts.

The switch must be in the open position before it can be moved to the grounded position. An operator handle inserted in the mechanism ground slot is used to manually rotate the grounding mechanism clockwise. After the springs become fully charged, they toggle over the center position and discharge their stored energy to the ground mechanism.

The mechanism forces the main blades into the grounded position. The speed of the operating mechanism is also independent of the speed of the user, identical to the spring opening sequence. The mimic bus on the end of the switch shaft (visible on mechanism cover) indicates that the contacts are in the grounded position. The front load access panel can only be removed when the switch is in the grounded position.

The front load access panel must be installed before the switch can be moved from its grounded to open position. With the front load access panel installed, an operator handle inserted in the mechanism ground slot is used to manually rotate the grounding mechanism counterclockwise. After the springs become fully charged, they toggle over the center position and discharge their stored energy to the ground mechanism. The mechanism forces the main blades into the open (ungrounded) position.

The speed of the operating mechanism is independent of the speed of the user. The mimic bus on the end of the switch shaft (visible on the mechanism cover) indicates that the contacts are in the open (ungrounded) position. Since the ground switch is immersed in SF₆ gas, it has a short-circuit-making capability should a trip condition exist on the circuit when the switch is operated.

With the switch in its open/ungrounded position, an operating handle in the operating slot is rotated clockwise until the springs become fully charged and they toggle over the center position. The mechanism forces the main blades into the closed position. The speed of the operating mechanism is also independent of the speed of the user. The mimic bus on the end of the switch shaft indicates that the contacts are in the closed position. The LLIs indicate that voltage is present on the circuit.

Motor-operated HVL/cc switches are available for applications requiring remote operation. Used with programmable controllers (such as Modicon^TM controllers) or electromechanical relays, motor-operated switches may be used in automatic load transfer applications. Low voltage controls are in the top-mounted low voltage compartment.

Mechanism Cover Application A, OTM Shown