Chint offers air-insulated, metal-clad, withdrawable medium-voltage switchgear (KYN28A-12 for 3.6 to 12 kV and KYN28A-24 for 24 kV), and SF6-insulated ring main units (RMU) such as the NG7-12/24 and the NG7-17.5. KYN28A switchgear is built to IEC 62271-200 and accepts vacuum circuit breakers from Chint or other manufacturers.
What it is and where it is used
Chint is a Chinese manufacturer of electrical equipment whose distribution catalog includes medium-voltage switchgear. Among them are the withdrawable metal-clad KYN28A-12 and KYN28A-24 switchgear, and the NG7-12/24 and NG7-17.5 ring main units (RMU). The subsidiary CHINT Colombia, which according to Chint itself opened its Bogotá office in 2025, presents a low- and medium-voltage portfolio on its site; which specific models it offers locally should be confirmed with the subsidiary.
A medium-voltage switchgear groups the circuit breaker, disconnectors, busbars, instrument transformers and protection of a feeder in one cabinet. For the general concept, see medium-voltage switchgear: parts, functions and tests. For those built or offered in the region, see medium-voltage switchgear in Colombia and Mexico.
Variants: KYN28A-12, KYN28A-24, KYN61-40.5 and NG7
| Model | Application | Main difference |
|---|---|---|
| KYN28A-12(Z) | Distribution substations, industry and generation | Withdrawable metal-clad, 3.6 to 12 kV; rated current 630 to 5000 A and short-circuit current 16 to 50 kA, according to Chint |
| KYN28A-24(Z) | 24 kV networks | Withdrawable metal-clad, 24 kV; Chint publishes a 14-page catalog with the 630 to 3150 A version |
| KYN61-40.5(Z) | 40.5 kV networks | Withdrawable metal-clad, listed by Chint as a related product |
| NG7-12/24 | Secondary distribution, branches and rings | SF6-insulated RMU: 12 kV, 630 A, 25 kA and 24 kV, 630 A, 20 kA according to Chint |
| NG7-17.5 | Secondary distribution | “Smart” RMU with transformer protection, earth-fault indicator and sensors |
The exact designation of your switchgear, with its letters and figures, is on the nameplate and in the purchase order; use it to find the catalog.
Main features
- Separate compartments. The withdrawable metal-clad switchgear separates the circuit breaker, busbars, cables and the low-voltage compartment. The breaker moves on a truck between the test and service positions.
- Interlocks. Chint describes “complete mechanical interlocks to protect personnel” and lists them as a KYN28A feature. The manufacturer’s catalog, not this page, is the reference for what blocks what in your switchgear. The general principles are in interlocks in medium-voltage switchgear and RMUs.
- Internal arc. The table on the KYN28A-24 page lists an internal arc classification (IAC AFLR 31.5 kA/1 s). Verify the classification of your version in the type test certificate.
- Circuit breaker. Chint states that the switchgear houses its own or third-party vacuum breakers. The mechanical and interlock compatibility of a breaker from another brand is checked with the manufacturer.
- NG7 RMU. Chint presents it with a compact, maintenance-free design and flexible extension, for ring networks or dual radial supply, and cites IEC 62271-200 and IEC 62271-1 as standards. The sequence of opening, earthing and restoring an RMU is in switching an RMU; its tests are in RMU tests.
According to the manufacturer’s manual
For the NG7-12/24 RMU we read the installation and operation manual from CHINT Electric in its Russian edition, published as an annex to a public tender. A general summary, not a substitute for the manual:
- Composition (§1.1, p. 1). The NG7 is assembled from modules of one to five functions in a common SF6 tank, extensible by busbar. The manual lists fifteen modules; those of a typical station are C (three-position load-break switch), F (load-break switch with fuses), V (vacuum breaker with three-position disconnector) and D or De (direct cable connection, without or with earthing).
- Interlocks (§3.2 and §4.2.2, p. 9 and 13–14). The load-break switch and its earthing switch are mechanically interlocked: each is operated only with the other open. Each operating mechanism accepts a padlock. The cable compartment door is interlocked with the earthing switch and can be removed only with the earthing switch closed.
- Sequences (§4.2.2, p. 14). Before energizing or de-energizing, the SF6 density gauge must read more than 1.4 bar, in the green zone. In C and F, to de-energize you open the load-break switch and close the earthing switch; to energize, the reverse order. In V, to de-energize you open the breaker, then the disconnector and close the earthing switch; to energize, earthing switch open, disconnector and, last, the breaker. The mechanisms are operated with the manufacturer’s lever; the breaker and the F function close after the spring is charged.
- Maintenance (§5.1, p. 17). Inspection of the tank pressure, the lubrication of the mechanisms and corrosion, and one close and open cycle of the load-break switch and the vacuum breaker at least once every three years.
That order can be practiced on NG7 units in the task “CHINT NG7 RMU: earth cable 2-3” of the solar plant switching simulator, available in Spanish. The KYN28A sequence is in its own operating manual and is not summarized here.
Communications and integration
The withdrawable switchgear houses a protection and control relay in the low-voltage compartment, and the protocols (IEC 61850, DNP3, Modbus) depend on that relay, not on the switchgear. The NG7-17.5 is described on Chint’s blog with a self-powered protection relay, an earth-fault indicator and current and voltage sensors, able to communicate with distribution management systems. A protection and control relay for the transformer feeder is integrated into SCADA by IEC 61850 or DNP3, depending on the relay chosen; the choice between a self-powered relay and one with auxiliary supply is covered in transformer feeder relay.
Common technical questions
- Chint KYN28A switchgear manual: Chint publishes the KYN28A-24 catalog on its site. On the KYN28A-12 page only the link to the document list appears. The switching sequence of your switchgear is in the manual that comes with the delivery; we do not reproduce it here because it changes with the version.
- Switchgear of one brand with a Chint breaker, or the reverse: it depends on dimensional and interlock compatibility, which the switchgear manufacturer defines.
- How a switchgear is tested on receipt: breaker tests, contact resistance, insulation, interlock verification and relay functional tests.
- Chint recloser: it is a different piece of equipment; see ZW32-12 recloser: Chint, Ghorit, Rockwill and FTU.
What to verify when specifying or receiving switchgear
- Nameplate data against the specification. Rated voltage, rated busbar and breaker current, short-time short-circuit current and internal arc classification (IAC) must match the project’s short-circuit study, not the generic catalog.
- Type test certificates. IEC 62271-200 requires type tests on the switchgear; ask for the report of your exact version and, if the switchgear carries a breaker from another brand, that the test covers that combination.
- Local code and inspection. Medium-voltage switchgear is part of an electrical installation that must meet the local electrical code and the utility’s requirements, and pass the inspection they call for.
- Relay and instrument transformers. Define who supplies the relay, the current and voltage transformers and their accuracy class, so that protection and the utility metering are properly coordinated.
- Acceptance tests. Before energizing, the breaker, contacts, insulation and interlocks are tested, and the relay functional tests are carried out.
How we can help
With medium-voltage switchgear, whether Chint or another brand, our team carries out acceptance and commissioning tests, interlock verification, and relay configuration and testing for the switchgear. In solar plants, the switchgear of the transformer stations and of the substation is part of solar plant commissioning. For the switchgear relay, see remote relay configuration. If you are still defining which switchgear to install, primary engineering design includes the single-line diagram and the specification. Write to us through contact. Field work is done in Colombia, or elsewhere on request; remote relay configuration is available worldwide.
Related guides
- Medium-voltage switchgear: parts, functions and tests
- Medium-voltage switchgear in Colombia and Mexico
- ZW32-12 recloser: Chint, Ghorit, Rockwill and FTU
- Transformer feeder relay: self-powered or auxiliary
- Switching an RMU: opening, earthing and restoring
- Medium-voltage RMU (ring main unit) tests
- Solar transformer station (skid): what it is and parts
- Switching Chint NG7 units: sequence and interlocks
References
- IEC 62271-200, AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV; IEC 62271-1.
- Chint, product pages for KYN28A-12(Z), KYN28A-24(Z) and NG7-12/24, KYN28A-24(Z) catalog (2024) and blog on smart RMUs.
- Chint, note on the CHINT Colombia office in Bogotá.
- CHINT Electric, NG7-12/24 (RMU): installation and operation manual, Russian edition (annex to a public tender in Moldova, storage.mtender.gov.md).
Frequently asked questions
What is a Chint KYN28A-12 switchgear?
It is an air-insulated, withdrawable, metal-clad switchgear for 3.6 to 12 kV systems. According to the Chint page it accepts vacuum circuit breakers of the brand or from other manufacturers and is built to IEC 62271-200. It is used in distribution substations, industry and generating plants.
What is the difference between the KYN28A-12 and the KYN28A-24?
The rated voltage: the KYN28A-12 goes up to 12 kV and the KYN28A-24 up to 24 kV. The current and short-circuit current ranges also change and must be taken from each catalog, because on the KYN28A-24 page the text and the table from Chint do not give the same current range.
Is the Chint NG7 RMU the same as a KYN28A switchgear?
No. The KYN28A is an air-insulated withdrawable switchgear for substations; the NG7 is an SF6-insulated ring main unit (RMU) for secondary distribution, with load-break switches and transformer protection. Each one answers a different need.