Back to Top

The tower-mounted device installs into existing rightaways without the need to secure a permit or buy land, allowing you to efficiently sectionalize transmission lines, transfer loads, and connect new customers. These power-operated Circuit-Switchers can be SCADA-operated even in the most remote locations.

Mark V Circuit-Switchers are available in a variety of mounting styles with optional pre-insertion inductors for use in single-bank and multiple-bank (back-to-back) capacitor switching. When fitted with these pre-insertion inductors, the device can minimize capacitor-bank switching transients, markedly improving power quality and reliability.

Mark V Circuit-Switchers are available with continuous current ratings of 1200, 1600, and 2000 amperes.

The Mark V Circuit-Switcher uses an in-series circuit-breaking interrupter and a circuit-making and isolating disconnect, making it especially suited for the switching and protection of transformers, lines, cables, capacitor banks, and line-connected or tertiary-connected shunt reactors. The Mark V Circuit-Switcher is available in three styles—Vertical-Break, Center-Break, and Integer.

Performance-proven through over 40 years of reliable service

  • Unsurpassed capacitor switching — pre-insertion inductors dramatically reduce inrush currents, tame damaging overvoltages that can shut down sensitive adjustable-speed drives
  • Unlimited installation flexibility — can be custom-tailored to fit any structure, phase spacing or bus height
  • Maintenance-free interrupters — hermetically sealed to eliminate the hassle and expense of field filling with SF6 . . . ensure long, trouble-free life
  • Superb mechanical and electrical operating life . . . proven in the lab and in the field, backed by a full 5-year warranty

For more information regarding transient control, refer to the technical paper titled “Selecting a Capacitor-Switching Overvoltage Control Method Effective in Preventing Nuisance Tripping of Adjustable-Speed Drives”.

Mark V Circuit-Switchers are also well-suited for transformer, line, cable, and reactor switching and protection. For more information, see S&C Specification Bulletin 711-31.

Voltage and Continuous, Short-Time, and Fault-Closing Ratings

kVAmperes, RMS
Nom.MaxBILCont.Short-TimeFault-Closing,
Duty-Cycle,
One-Time
Mom.3-Second
34.5 38 200 1200 61 000 40 000 30 000
46 48.3 250 1200 61 000 40 000 30 000
69 72.5 350 1200 61 000 40 000 30 000
115 121 550 1200 61 000 40 000 30 000
138 145 650 1200 61 000 40 000 30 000
1600♥ 70 000 43 750 40 000
2000♥ 80 000 50 000 40 000
161 169 750 1200 61 000 40 000 30 000
230 242 900 1600 70 000 43 750 40 000
2000 80 000 50 000 40 000
345 362 1300 1600 70 000 43 750 40 000
2000 80 000 50 000 40 000

♥ 1600 and 2000 amperes continuous available in Three-Pole Center-Break style only.

Interrupting Current Ratings for Transformer Switching and Protection

ClassQualificationsMaximum Amperes,
Interrupting RMS
Symmetrical
Parallel Switching Max 60-hertz recovery voltage: 90 kV RMS and 150 kV RMS 1200/1600/2000
Load Dropping and Magnetizing Current Switching Transformers connected to solidly grounded-wye on the primary (Circuit-Switcher) side and delta on the secondary side 1200/1600/2000
All other connections of transformers 1200/1600/2000
Fault Interrupting Primary faults with the total connected length of all lines on the source side of the Circuit-Switcher not less than . 7000 or 8000
Primary faults with the total connected length of all lines on the source side of the Circuit-Switcher less than ♠. 4000 (3000A for 115-kV single-gap Circuit-Switchers)
Secondary faults — all other connections of transformers 4000 (3000A for 115-kV single-gap Circuit-Switchers)
Internal faults — see both primary and secondary faults, above

 Depending on continuous rating of Circuit-Switcher.
 Will switch magnetizing currents associated with such loads.
 Total connected length of all ovehead lines (in all directions) including any number of feeders connected to source-side substations as indicated in the table below:

System Voltage, kV 34.5 thru 69 115 and 138 161 230 345
Total Length, Miles 7 15 20 25 40


Interrupting Current Ratings for Line Switching and Protection

ClassQualificationsMaximum Amperes,
Interrupting RMS
Symmetrical
Load Splitting (Parallel or Loop Switching) Max 60-hertz recovery voltage: 90 kV RMS and 150 kV RMS 1200/1600/2000
Load Dropping Circuits with all load-side transformers connected solidly grounded-wye on the primary (Circuit-Switcher) side and delta on the secondary side 1200/1600/2000
Circuits with all load-side transformers connected other than as described above. 1200/1600/2000
Line Dropping Maximum length of line: 300 miles.
Fault Interrupting Line or bus faults with the total connected length of all lines on the source side of the Circuit-Switcher not less than . 7000 or 8000
Line or bus faults with the total connected length of all lines on the source side of the Circuit-Switcher less than . 4000 (3000A for 115-kV single-gap Circuit-Switchers)

 Depending on continuous rating of Circuit-Switcher.
 Total connected length of all ovehead lines (in all directions) including any number of feeders connected to source-side substations as indicated in the table below:

System Voltage, kV 34.5 thru 69 115 and 138 161 230 345
Total Length, Miles 7 15 20 25 40


Interrupting Current Ratings for Cable Switching and Protection

ClassQualificationsMaximum Amperes,
Interrupting RMS
Symmetrical
Load Splitting (Parallel or Loop Switching) Max 60-hertz recovery voltage: 90 kV RMS and 150 kV RMS 1200/1600/2000
Load Dropping Circuits with all load-side transformers connected solidly grounded-wye on the primary (Circuit-Switcher) side and delta on the secondary side 1200/1600/2000
Circuits with all load-side transformers connected other than as described above. 1200/1600/2000
Cable Dropping (Charging Current) Shielded and Unshielded Cable 550
Fault Interrupting Cable or bus faults with the total connected length of all lines on the source side of the Circuit-Switcher not less than . 7000 or 8000
Cable or bus faults with the total connected length of all lines on the source side of the Circuit-Switcher less than . 4000 (3000A for 115-kV single-gap Circuit-Switchers)

 Depending on continuous rating of Circuit-Switcher.
 Total connected length of all ovehead lines (in all directions) including any number of feeders connected to source-side substations as indicated in the table below:

System Voltage, kV 34.5 thru 69 115 and 138 161 230 345
Total Length, Miles 7 15 20 25 40


Interrupting Current Ratings for Shunt Capacitor Bank Switching and Protection

ClassQualificationsMaximum Amperes,
Interrupting RMS
Symmetrical
Bank Current Switching Grounded capacitor bank Applications on solidly grounded systems through 69 kV 1000
All other applications 550
Ungrounded capacitor bank 550
Fault Interrupting Primary faults with the total connected length of all lines on the source side of the Circuit-Switcher not less than . 7000 or 8000
Primary faults with the total connected length of all lines on the source side of the Circuit-Switcher less than . 4000 (3000A for 115-kV single-gap Circuit-Switchers)

 Total connected length of all ovehead lines (in all directions) including any number of feeders connected to source-side substations as indicated in the table below:

System Voltage, kV 34.5 thru 69 115 and 138 161 230 345
Total Length, Miles 7 15 20 25 40


Interrupting Current Ratings for Reactor Switching and Protection

ClassQualificationsMaximum Amperes,
Interrupting RMS
Symmetrical
Series Reactor Switching Refer to the nearest S&C Sales Office.
Shunt Reactor Switching and Protection (Line-Connected or Tertiary Connected Reactors) Reactor Current Switching Reactor wye-connected with solidly grounded neutral 1000
Reactor delta-connected, or wye-connected with ungrounded neutral 1000
Fault Interrupting Oil-insulated reactors 2800
Air-insulated reactors 2000

pre-insertion inductor,  limit inrush current,  overvoltage at the capacitor-bank bus, phase-to-phase switching-surge overvoltages at remote transformer, control overvoltage

Pre-insertion inductors are especially suited for limiting transient overvoltages which, through voltage magnification, 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.

Type CS-1A Switch Operator

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

  • Additional auxiliary-switch contacts
  • 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.

Loading...