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The Mark VI Circuit-Switcher offers the latest in interrupter technology. It features a 31.5-kA fault-interrupting rating and 3-cycle interrupting time with simultaneity of less than ¼ cycle. No shunt-trip device is needed. The Mark VI Circuit-Switcher is significantly lighter than the Mark V Circuit-Switcher, is easier to install, and has reduced maintenance requirements.

The Mark VI Circuit-Switcher uses the same rugged integral disconnect as the Mark V, making it perfect for use with pre-insertion inductors.

  • Higher-than-ever 31.5-kA fault-interrupting rating and 3-cycle interrupting time.
  • Three-phase tripping by electrically linked interrupters — provides tripping simultaneity of less than ¼ cycle.
  • Hermetically sealed interrupters — eliminates the hassle of field-filling with SF6 gas. Interrupters provide full dielectric ratings when open.
  • Reliable performance — Mark VI uses the same robust high-speed disconnect as Mark V Circuit-Switcher and the heavy-duty Mark VI CS-1A Switch Operator.

Optional features include:

  • Pre-insertion Inductors. With the addition of pre-insertion inductors, Mark VI Circuit-Switcher is ideal for capacitor-bank applications, combining switching, protection, and transient overvoltage control in one device. Pre-insertion inductors limit inrush current and overvoltage at the capacitor-bank bus, limit phase-to-phase switching-surge overvoltages at remote transformers, and control overvoltages on long, open-ended lines and on the user’s utilization-voltage bus.
  • S&C Mounting Pedestals. Dramatically reduce installation time with S&C’s easy-to-install mounting pedestals.

Voltage and Continuous, 4-Hour, Peak Withstand, and Fault-Closing Current Ratings — 50/60-Hz.

kVAmperes, RMS
69 72.5 350 420 630 81 900 31 500 30 000
115 123 550 420 630 81 900 31 500 30 000
138 145 650 420 630 81 900 31 500 30 000

Interrupter Current Ratings For Shunt Capacitor Bank Switching and Protection

ClassQualificationsMaximum Amperes, Interrupting RMS Symmetrical
Bank Current Switching Grounded capacitor banks applied on solidly grounded systems only, through 138 kV 420
Ungrounded capacitor banks through 138 kV 420
Fault Interrupting 31 500

Interrupter Current Ratings For Transformer Switching and Protection

ClassQualificationsMaximum Amperes, Interrupting RMS Symmetrical
Load Dropping 630
Duty-Cycle Fault Interrupting 3-Time 31 500
5-Time 18 900
10-Time 9 450
30-Time 3 150
Secondary Faults 69 kV 4 200
115 kV through 138 kV 2 600
Internal faults — see both primary and secondary faults, above

Pre-insertion inductors are especially suited for limiting transient overvoltages which, through voltage manification, can result in nuisance tripping of adjustable-speed drives and other sensitive electronic devices. Voltage magnification can occur where power-factor correction capacitors and/or voltage control capacitors are applied on the utility distribution system or on a utility customer’s low voltage bus, and is caused by a near-resonant condition between the switched capacitor bus and the capacitances at lower voltages.

Pre-insertion inductors are more effective than controlled-closing schemes and pre-insertion resistors for limitation of:

  • Inrush current and overvoltage at the capacitor bank bus — curbing induced transients in substation low-voltage circuits that can cause spurious signals, insulation puncture, and component damage.
  • Switching-surge overvoltages at remote transformers — which can lead to decreased transformer life, or even failure.
  • Overvoltages on long open-ended lines. Such overvoltages can cause nuisance arrestor operation.
  • Transient overvoltages on users’ utilization-voltage bus — voltage magnification of capacitor-switching transients can cause nuisance tripping of adjustable-speed drives and other sensitive electronic devices.

How does the pre-insertion inductor work?

First, an open-air arc makes up the initial circuit through the pre-insertion inductor. The inductor core picks up the inrush current before it reaches the main contact. Then, the pre-insertion inductor is bypassed, and disconnected as the moving arcing rod rotates. As the main contact is made, the pre-insertion inductor is completely removed from the circuit.

Pre-insertion inductor

The sliding contact arrangement places the pre-insertion inductor in the circuit for only a few cycles. That’s how long it takes to provide high-quality transient control.

For complete application information on S&C Pre-insertion Inductors refer to S&C Data Bulletin 711-95 or contact the nearest S&C Sales Office.

The Mark VI CS-1A Switch Operator direct-drives the vertical-break disconnect of the Mark VI Circuit-Switcher. It provides trip-free capability. Should the Mark VI be inadvertently closed into a fault sensed by user-furnished relays, Mark VI will trip immediately.

The operator features a sturdy welded enclosure with baffled louvers that allow air circulation, but keep out rain. The interior of the weatherproof, dustproof enclosure is accessed by a hinged door . . . rather than removal of the entire enclosure.

The Mark VI CS-1A Switch Operator includes:

  • Six adjustable auxiliary switch contacts, coupled to the motor
  • External trip and close push buttons with padlockable cover
  • Built-in manual operating handle for the disconnect
  • Decoupling mechanism that allows decoupling and locking of the disconnect in the open position
  • Mechanical position indicator
  • Non-resettable operation counter.

Optional features for the Mark VI CS-1A Switch Operator include:

  • Additional auxiliary-switch contacts
  • LED position indicating lamps
  • Remote-control blocking switch
  • Space-heater thermostat
  • Duplex receptacle with ground-fault circuit interrupter, and convenience light lampholder with switch.

A Resource for Selecting a Substation Transformer Protective Device

One criterion in selecting a distribution substation transformer protective device is its ability to protect the transformer from secondary-side limited faults . . . or “through-faults.” These faults are difficult to detect by the overcurrent relay of the line-terminal circuit breaker, because the magnitude of the fault current is relatively low — being limited by the impedance of the transformer. These faults are a challenge to clear as well, because of their high transient recovery voltage.

Click here to use the Through-Fault Current Calculator.