Current transformer CTB size 1
bushing current transformer, encapsulated in epoxy resin • highest permissible system up to 36 kV • rated primary currents up to 3 kA • option: airtight bushing
Current transformers of CTB type are designed for indoor use at medium voltages. Epoxy resin casting (containing wounded cores inside) is the main electrical insulation. Excellent parameters of electrical insulation (including low level of partial discharges) are guaranteed.
CTB current transformers size 1 are used in all applications where small dimensions and high rated dynamic currents are necessary, for example in tapping busducts of power generators.
The primary current winding is made of copper conductor with silvered terminals. The length, size and type of terminals are manufactured according to Client’s requirements.
The epoxy resin castings of CTB current transformers size 1 are manufactured in various lengths, so the overall dimensions are optimised, according to the quantity of cores (max. 4 cores in standard execution) and their rated outputs.
CTB current transformers can be mounted in any position.
Technical data:
| highest permissible system voltage | 7.2/12/17.5/24/36 kV |
| power frequency withstand voltage, 1 min | 20/28/38/50/70 kV |
| impulse withstand voltage 1.2/50 µs | 60/75/95/125/170 kV |
| rated frequency | 50 or 60 Hz |
| rated primary current IPn | 75 – 3 000 A |
| rated short–time thermal current Ith1s | 150 kA/1s (r.m.s. value) |
| rated dynamic current Idyn | 250 kA (peak value) |
| number of cores | up to 4 |
| rated secondary currents ISn | 1 A or 5 A or fractional |
| rated outputs Sn | 5 – 90 VA |
| accuracy classes | 0.2, 0.2S, 0.5, 0.5S, 5P, 10P, PX, PR |
| instrument security factor (FS) | 5, 10, 15 |
| accuracy limit factor | 10, 20, 50 |
| ambient temperature | –25oC ÷ 80oC |
| weight | ca 20 – 45 kg |
| according to standards | PN-EN 61869-1:2009; PN-EN 61869-2:2012 |
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