Product Overview
ABB SCG-4 Window-Type Current Transformer - 800:5 Ratio, 600V Class, 10kV BIL, 50-400 Hz, 4" Bore
Condition
Unused NOS. Sourced from a government research facility. Black molded polycarbonate housing shows light surface scuffs and minor dust consistent with storage; no cracks, chips, or damage to the body or bore. Both 10-32 brass terminal studs are present and intact. Label markings legible: ABB SCG-4 800:5, 10kV BIL, 600V INS. CLASS, 50-400 Hz, serial no. 30532820/30532920.
Carefully packed and shipped same or next business day from our Idaho warehouse. Honest equipment and straightforward service.
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Product Overview
ABB 7525A29G12 - also cataloged as the ABB SCG-4 - is a molded polycarbonate window-type (toroidal/ring-type) indoor current transformer rated for 600V class systems with a 10kV Basic Impulse Insulation Level. It steps down an 800A primary current to a 5A secondary output, making high-current lines readable by standard metering and protective relay equipment without direct contact. The ultrasonically sealed housing measures 7" x 7" x 4" overall, with a 4.00" center window bore sized for large bus bars or heavy cable runs. Secondary connection is made via heavy-duty 10-32 brass terminal studs. Operational accuracy is maintained across 50-400 Hz, covering both 50 Hz and 60 Hz power systems as well as higher-frequency industrial and military applications.
Key Features
- Current ratio: 800:5 (800A primary, 5A secondary)
- Voltage class: 600V
- Basic Impulse Insulation Level (BIL): 10kV
- Frequency range: 50-400 Hz
- Center window bore: 4.00" (102 mm) - accepts large bus bars and heavy conductors
- Overall dimensions: 7" x 7" x 4"
- Housing: impact-resistant polycarbonate, ultrasonically sealed
- Secondary terminals: 10-32 brass terminal studs with hardware
- Indoor installation; window/ring/toroidal construction
- Part of the ABB SCG series
Applications
- Replacing a failed CT in an existing switchgear panel or motor control center - thread the primary bus bar through the 4" bore, terminate the secondary to the existing relay or meter, and restore accurate current monitoring without rewiring the high-current side
- Interfacing protective relays during a switchgear upgrade - the 10kV BIL rating gives the design margin needed when the engineer is specifying isolation in systems where transient impulses are a real concern
- Energy metering installations in industrial facilities where the facility team needs 800A-range current sensing brought down to a 5A signal readable by a standard panel meter or power quality analyzer
- System integration work where the 50-400 Hz frequency range is a qualifying requirement - covering both utility-frequency and higher-frequency drive or variable-speed applications in a single unit
- Spare-parts inventory for maintenance programs managing aging switchgear - keeping an unused unit on the shelf means a confirmed-fit replacement is available the moment a CT fails during a maintenance window
Frequently Asked Questions
Does the secondary circuit need to be kept closed at all times?
Yes - this is a critical safety requirement for any current transformer. While the primary conductor is energized, the secondary circuit must always remain closed (connected to a meter, relay, or short). An open secondary on an energized CT generates dangerously high voltages that can damage the transformer and create a serious shock and fire hazard.
What size conductor fits through the 4" window?
The center bore is 4.00" (102 mm) in diameter. This accommodates large bus bars and heavy-gauge cables typical of 800A-class feeders. Verify your primary conductor's outer diameter or bus bar cross-section fits within 4.00" before ordering.
Is this transformer suitable for both 50 Hz and 60 Hz power systems?
Yes. The rated frequency range is 50-400 Hz, covering standard 50 Hz and 60 Hz utility systems as well as higher-frequency industrial applications.
Is a mounting bracket or secondary shorting bar included?
No additional accessories are included. The transformer ships with its 10-32 brass terminal studs and hardware. Mounting hardware and secondary shorting devices are not included.
Can this be used in a system rated above 600V?
The voltage class rating is 600V. The 10kV BIL rating addresses impulse insulation, not continuous operating voltage. Applications above 600V class require additional insulation engineering considerations and are outside the rated continuous operating specification of this unit.
Window-type current transformers have one quietly elegant quality: the primary circuit never has to be interrupted or modified - the conductor simply passes through the bore, and measurement begins. This one sat unused in a government facility while that 4" window waited for the right 800A problem to come along. It is ready now.
