China 40.5kV Vacuum Circuit Breaker with Current Transformer Manufacturer, Supplier, Factory

Kexun Electric Co., Ltd. offers the 40.5kV Vacuum Circuit Breaker with Current Transformer as a factory-fitted option on the ZW7-40.5 frame, where the transformer set sits inside the same stainless box as the operating mechanism. The frame, the interrupters and the operating gear are identical whether or not the transformers are fitted, so a buyer orders one model number and adds the transformer set as a line item. The ratio, the burden and the accuracy class follow the customer's own protection and metering design rather than a fixed catalogue value. As a China manufacturer that builds to customer drawings, Kexun starts production only after the drawing is confirmed, with a minimum order of one set.

Current Transformers Inside the Frame

The transformer set is mounted inside the box, sharing the enclosure with the operating mechanism. Because the poles are integrated magnetic units, the transformer set is mounted inside the same enclosure, so the phase-to-phase distance stays at 700±2 mm and the footprint does not change. A 40.5kV Vacuum Circuit Breaker with Current Transformer therefore takes the same installation drawing as the bare breaker, and the civil work does not change with the option.

What the Option Adds

Frame Ratings With the Option

Fitting the transformer set does not change the published ratings of the frame.

Choosing the Ratio Setup

The ratio, the burden and the accuracy class are not fixed at the factory; they follow the customer's single-line diagram and relay settings. The buyer sends the drawing with the primary current, the protection relays and the metering load, and Kexun fits the transformer set to match that specification. Once the drawing is confirmed, production starts. The transformer set is an option selected according to the user's requirement, so an order without the option is simply the bare breaker.

What the Buyer Sends

At minimum the order needs the primary rated current, the relay model and setting range, the metering burden, and the required accuracy class for each winding. Without those values the order cannot specify the transformer set, and the breaker is then supplied without it.

Secondary Wiring and Terminals

The secondary leads from the transformer set are kept inside the same protected volume as the mechanism, separated from the closing, tripping and motor circuits. Secondary circuits pass a 2 kV one-minute power-frequency test, which is the level that protects the low-voltage side when the high-voltage cable switches nearby. Control voltage for the mechanism remains AC/DC 220 V, independent of the transformer secondary.

Mechanical Data of the Frame

The mechanical settings stay the same with or without the transformer set.

Metering and Protection Duty

The same transformer set can feed both the revenue meter and the over-current protection relay, depending on how the windings are wound and labelled on the customer drawing. The protection relay trips the breaker through the over-current trip coil, which is independent of the AC/DC 220 V control supply. Metering duty reads continuously while the unit is closed, and the loop resistance per phase stays below 80 μΩ so that metering burden is not distorted by joint resistance on the line side. The metering and protection windings on this 40.5kV Vacuum Circuit Breaker with Current Transformer are wound and labelled to the customer drawing, so the duty of each winding is fixed before energisation.

How the Trip Path Closes

The relay measures the current from the transformer, decides on a fault, and sends a trip command to the tripping electromagnet. The over-current trip coil on the mechanism also reacts directly to the sensed current, so the unit trips even if the relay supply is lost. Closing bounce stays below 5 ms and the three-phase spread below 2 ms, so the fault duty is cleared cleanly on the first open.

Ordering With or Without CTs

A buyer who already owns protection relays in a separate panel usually orders the breaker without transformers, saving the cost of duplicated windings. A buyer who wants metering and protection picked up at the breaker itself orders the fitted version. Both versions leave the same frame, and the warranty runs 12 to 24 months either way. The 40.5kV Vacuum Circuit Breaker with Current Transformer is therefore a custom build on a standard frame: the mechanical and electrical ratings are fixed, the transformer specification is not.

Order Steps

Send the drawing, confirm the ratio and burden, then sign off the final drawing. Production starts only after that confirmation, the minimum order is one set, and payment is by T/T or L/C.

Frequently Asked Questions

Q: Can I buy the breaker without current transformers?

A: Yes. The transformer set is an option chosen according to the user's requirement, and the frame, bushings and mechanism are identical with or without it. Buyers who keep protection in a separate panel usually take the version without transformers, while buyers who want metering picked up at the breaker order it fitted at the factory.

Q: Who decides the CT ratio and accuracy class?

A: The buyer. The ratio, the burden and the accuracy class follow the customer's own protection and metering design, not a fixed catalogue value. The order needs the primary rated current, the relay model and setting range, the metering burden and the required accuracy class for each winding.

Q: How are the secondary wires terminated?

A: The secondary leads are kept inside the same protected volume as the mechanism, separated from the closing, tripping and motor circuits. The secondary circuit passes a 2 kV one-minute power-frequency test before dispatch.

Q: Can the same transformer feed metering and protection?

A: Yes, depending on how the windings are wound and labelled on the customer drawing. The protection relay trips through the over-current trip coil, which is independent of the AC/DC 220 V control supply, and metering reads continuously while the unit is closed.

Q: When does production start after the order?

A: Production starts only after the customer confirms the final drawing. Kexun works to customer drawings or samples as OEM work, with a detailed discussion before production and a start only after the buyer confirms the drawing.

Q: What is the minimum order and payment terms?

A: The minimum order is one set. Standard models are held in stock, which keeps the delivery period short, and payment is by T/T or L/C. Photos or video of production and testing can be shared before dispatch.

Q: How long is the warranty?

A: Warranty runs from 12 to 24 months depending on the order terms, whether the unit is supplied with or without the transformer set. The export sales managers communicate in English, so a commissioning question does not wait for translation.

Q: Does the CT option change the installation drawing?

A: No. The transformer set is mounted inside the same stainless box, the phase-to-phase distance stays at 700±2 mm, the frame footprint and the 600 kg erection weight are unchanged, and the installation drawing for the breaker applies to both versions.

CT Options in Brief

Transformers in or transformers out: the frame, the bushings and the mechanism are the same, and the ratio follows the customer drawing rather than a catalogue. With metering and protection taken from the same set, and production held until the drawing is confirmed, the 40.5kV Vacuum Circuit Breaker with Current Transformer is a custom build on a standard frame. As a China manufacturer with English-speaking export managers, Kexun Electric Co., Ltd. accepts orders from one set by T/T or L/C and covers the unit for 12 to 24 months.